Patent Application
20220256919
The present disclosure relates to a smoking substitute apparatus and, in particular, a smoking substitute apparatus that is able to reduce fluid leakage during use, as well as to deliver nicotine to a user in an effective manner.
The smoking of tobacco is generally considered to expose a smoker to potentially harmful substances. It is thought that a significant amount of the potentially harmful substances are generated through the burning and/or combustion of the tobacco and the constituents of the burnt tobacco in the tobacco smoke itself.
Low temperature combustion of organic material such as tobacco is known to produce tar and other potentially harmful by-products. There have been proposed various smoking substitute systems in which the conventional smoking of tobacco is avoided.
Such smoking substitute systems can form part of nicotine replacement therapies aimed at people who wish to stop smoking and overcome a dependence on nicotine.
Known smoking substitute systems include electronic systems that permit a user to simulate the act of smoking by producing an aerosol (also referred to as a “vapor”) that is drawn into the lungs through the mouth (inhaled) and then exhaled. The inhaled aerosol typically bears nicotine and/or a flavorant without, or with fewer of, the health risks associated with conventional smoking.
In general, smoking substitute systems are intended to provide a substitute for the rituals of smoking, whilst providing the user with a similar, or improved, experience and satisfaction to those experienced with conventional smoking and with combustible tobacco products.
The popularity and use of smoking substitute systems has grown rapidly in the past few years. Although originally marketed as an aid to assist habitual smokers wishing to quit tobacco smoking, consumers are increasingly viewing smoking substitute systems as desirable lifestyle accessories. There are a number of different categories of smoking substitute systems, each utilizing a different smoking substitute approach. Some smoking substitute systems are designed to resemble a conventional cigarette and are cylindrical in form with a mouthpiece at one end. Other smoking substitute devices do not generally resemble a cigarette (for example, the smoking substitute device may have a generally box-like form, in whole or in part).
One approach is the so-called “vaping” approach, in which a vaporizable liquid, or an aerosol precursor or aerosol precursor, sometimes typically referred to herein as “e-liquid”, is heated by a heating device (sometimes referred to herein as an electronic cigarette or “e-cigarette” device) to produce an aerosol vapor which is inhaled by a user. The e-liquid typically includes a base liquid, nicotine and may include a flavorant. The resulting vapor therefore also typically contains nicotine and/or a flavorant. The base liquid may include propylene glycol and/or vegetable glycerin.
A typical e-cigarette device includes a mouthpiece, a power source (typically a battery), a tank for containing e-liquid and a heating device. In use, electrical energy is supplied from the power source to the heating device, which heats the e-liquid to produce an aerosol (or “vapor”) which is inhaled by a user through the mouthpiece.
E-cigarettes can be configured in a variety of ways. For example, there are “closed system” vaping smoking substitute systems, which typically have a sealed tank and heating element. The tank is pre-filled with e-liquid and is not intended to be refilled by an end user. One subset of closed system vaping smoking substitute systems include a main body which includes the power source, wherein the main body is configured to be physically and electrically couplable to a consumable including the tank and the heating element. In this way, when the tank of a consumable has been emptied of e-liquid, that consumable is removed from the main body and disposed of. The main body can then be reused by connecting it to a new, replacement, consumable. Another subset of closed system vaping smoking substitute systems are completely disposable, and intended for one-use only.
There are also “open system” vaping smoking substitute systems which typically have a tank that is configured to be refilled by a user. In this way the entire device can be used multiple times.
An example vaping smoking substitute system is the myblu™ e-cigarette. The myblu™ e-cigarette is a closed system which includes a main body and a consumable. The main body and consumable are physically and electrically coupled together by pushing the consumable into the main body. The main body includes a rechargeable battery. The consumable includes a mouthpiece and a sealed tank which contains e-liquid. The consumable has an inlet which is fluidly connected to an outlet at the mouthpiece by an air flow channel. The consumable further includes a heater, which for this device is a heating filament coiled around a portion of a wick positioned across the width of the air flow passage. The wick is partially immersed in the e-liquid, and conveys e-liquid from the tank to the heating filament. The system is controlled by a microprocessor on board the main body. The system includes a sensor for detecting when a user is inhaling through the mouthpiece, the microprocessor then activating the device in response. When the system is activated, electrical energy is supplied from the power source to the heating device, which heats e-liquid from the tank to produce a vapor, which promptly condenses to form an aerosol as it is cooled by an air flow passing through the air flow passage. A user may therefore inhale the generated aerosol through the mouthpiece.
For a smoking substitute system, it is desirable to deliver nicotine into the user's lungs, where it can be absorbed into the bloodstream. However, the present disclosure is based in part on a realization that some prior art smoking substitute systems, such delivery of nicotine is not efficient. In some prior art systems, the aerosol droplets have a size distribution that is not suitable for delivering nicotine to the lungs. Aerosol droplets of a large particle size tend to be deposited in the mouth and/or upper respiratory tract. Aerosol particles of a small (e.g., sub-micron) particle size can be inhaled into the lungs but may be exhaled without delivering nicotine to the lungs. As a result, the user would require drawing a longer puff, more puffs, or vaporizing e-liquid with a higher nicotine concentration in order to achieve the desired experience.
Furthermore, in such prior art smoking substitute systems the air inlet is often positioned at the base of the vaporizing chamber. In use, coalesced aerosol droplets that are too large to be suspended in the airflow, as well as excess aerosol precursor that is wicked from the sealed tank, may undesirably leak through the air inlet by gravity.
Accordingly, there is a need for improvement in the delivery of nicotine to a user, as well as reduction in fluid leakage, in the context of a smoking substitute system.
The present disclosure has been devised in the light of the above considerations.
In a general aspect, the present disclosure relates to a smoking substitute apparatus that, when placed in an upright orientation, has at least one chamber inlet positioned above the aerosol generator in an aerosol generation chamber. As such, substantially all of the air flow entering the aerosol generation chamber is directed away from the aerosol generator.
According to a first preferred aspect there is provided a smoking substitute apparatus for generating an aerosol, comprising:
an aerosol generation chamber containing an aerosol generator being operable to generate an aerosol from an aerosol precursor, the aerosol generation chamber having a chamber outlet and at least one chamber inlet, air flowing in use from the at least one chamber inlet into the aerosol generation chamber towards the chamber outlet to entrain generated aerosol for inhalation by a user drawing on the apparatus;
wherein, when the apparatus is oriented upright, said at least one chamber inlet is positioned higher than the position of the aerosol generator and configured so that substantially all of the airflow entering the aerosol generation chamber is directed away from the aerosol generator.
The aerosol generation chamber may be provided at or towards a first end of a housing of the apparatus. For example, the base of the aerosol generation chamber may form the base of the housing. Said first end of the housing may be engageable with a main body of a smoking substitute system. The chamber outlet may open towards the second end of the housing and in fluid communication with an outlet at a mouthpiece at the second end of the housing, onto which the user may puff in order to draw an air flow through the aerosol generation chamber.
For the avoidance of doubt, we note here that a user may draw on the apparatus with or without making physical contact with the apparatus. For example, a mouthpiece or other intervening structure may be provided, separate from and/or separable from the housing of the smoking substitute apparatus, and the user's lips may make contact with this mouthpiece or other intervening structure when drawing on the apparatus.
For convenience of discussion of the structure of the smoking substitute apparatus, it is considered to be placed in an upright orientation. In contrast to prior art smoking substitute systems, which generate an aerosol by directly passing an air flow over the heater, the at least one chamber inlet according to the present disclosure may be located at a position above the aerosol generator in said upright orientation. In other words, the chamber inlet may be positioned downstream to the aerosol generator in the direction of aerosol flow. For example, substantially all of the air flow may enter the aerosol generation chamber along an air flow path between the at least one chamber inlet and the chamber outlet, and wherein the aerosol generator may be arranged to be spaced from the air flow path. More specifically, the at least one chamber inlet may open, at the aerosol generation chamber, in a direction away from the aerosol generator, e.g., the at least one chamber inlet may open in a direction parallel to the aerosol generator. Advantageously, such arrangement may avoid having the majority of air flow directly impinging upon the aerosol generator, and therefore it may reduce the amount of turbulence in the vicinity of the aerosol generator. As a result, an aerosol with enlarged droplet sizes may be formed.
The aerosol precursor may comprise a liquid aerosol precursor, and wherein the aerosol generator may comprise a heater configured to generate the aerosol by vaporizing the liquid aerosol precursor. The liquid aerosol precursor may be an e-liquid and may comprise nicotine and a base liquid such as propylene glycol and/or vegetable glycerin and may include a flavorant. The aerosol generator may be a heater such as a heater coil wound around a wick.
In use, the aerosol generator may vaporize the aerosol precursor to form a vapor. The vapor may expand or flow from the aerosol generator to merge or entrain into the air flow entering the chamber through the at least one chamber inlet. For example, the formation of vapor may increase the internal pressure at the aerosol generation chamber, and may advantageously aid the convection of the vapor towards the chamber outlet. Said vapor may cool and condense to from an aerosol in the aerosol generation chamber and subsequently be discharged towards the chamber outlet. More specifically, substantially all of the air flow entering the aerosol generation chamber may not directly pass over the aerosol generator but may only come into contact with the vapor and/or aerosol once it is formed. Even though the air flow may induce a degree of turbulence in the aerosol generation chamber, the turbulence in the vicinity of the aerosol generator in the present disclosure is significantly lower than the amount of turbulence that would otherwise occur in prior art consumables. The base of the aerosol generation chamber may be sealed against air flow. This is discussed in more detail below.
Optionally, when the apparatus is oriented upright, the aerosol generation chamber is sealed against air flow into or out of the chamber in a region level with and below the position of the aerosol generator. For example, in said upright orientation the chamber outlet of the aerosol generation chamber may face an upward direction, with the sealed region of the aerosol generation chamber positioned below both the chamber inlet and chamber outlet. That is, in the sealed region of the aerosol generation chamber may be free from apertures that allow the passage of an air flow. The sealed region of the aerosol generation chamber may comprise sealed apertures for allowing electrical contact to extending therethrough. As a result, any excess aerosol precursor accumulated at the aerosol generator, e.g., in the case of a heater, at a wick of the heater, may be retained in the aerosol generation chamber by gravity. Therefore advantageously, such arrangement may reduce or eliminate liquid leakage through the smoking substitute apparatus.
In alternative arrangements, some air flow may be permitted to enter the aerosol generation chamber. However, where such air flow is permitted, preferably this is only in an amount that does not significantly affect the degree of turbulence around the aerosol generator.
Optionally, the chamber inlet may form on a sidewall of the aerosol generation chamber at a position in between the aerosol generator and the chamber outlet. In some embodiments, at least a portion of the sidewall of the aerosol generation chamber may be defined by the housing, and wherein the chamber inlet may form on said portion of sidewall through the housing. For example, the chamber inlet may open on a sidewall of the housing and into the aerosol generation chamber. In other embodiments, the aerosol generation chamber may form separately to the housing. For example, the aerosol generation chamber may extend coaxially with the housing, and an annulus may be defined between the respective sidewalls of the aerosol generation chamber and the housing. The annulus may comprise a tank for storing a reservoir of aerosol precursor. In such embodiments, an air inlet passage may extend from an opening of the sidewall of the housing, through the annulus to the chamber inlet of the aerosol generation chamber.
Optionally, the smoking substitute apparatus is configured to generate an aerosol having a droplet size, d50, of at least 1 μm. Optionally, the smoking substitute apparatus is configured to generate an aerosol having a droplet size, d50, ranged between 1 μm to 4 μm. Optionally, the smoking substitute apparatus is configured to generate an aerosol having a droplet size, d50, ranged between 2 μm to 3 μm. Advantageously, aerosol having droplets in such size ranges may improve delivery of nicotine into the user's lung, by reducing the likelihood of nicotine deposition in the mouth and/or upper respiratory tract, e.g., in the case of oversized aerosol droplets, or not being absorbed at all, e.g., in the case of undersized aerosol droplets.
Optionally, the aerosol generator is adjacent to the base of the aerosol generation chamber. Advantageously, such arrangement may allow the aerosol generator to be located at a position furthest away from the chamber inlet and the air flow entering therethrough, and therefore it may limit the turbulence in the vicinity of the aerosol generator. Further, such arrangement may increase the residence time of the vapor in the aerosol generation chamber and thus it may allow some aerosol droplets to form and even coalesce before being entrained in the air flow. Additionally in the case of a heater, at such location, the wick of the heater may absorb excess aerosol precursor that is collected at the base of aerosol generation chamber, and subsequently allowing it to be vaporized.
Alternatively, the aerosol generator is located at a position adjacent to the chamber inlet, e.g., the aerosol generator is immediately upstream of the chamber inlet. Advantageously, this may shorten the path of travel for the aerosol and thereby allow the aerosol to be promptly entrained or merged into the air flow.
Optionally, the aerosol generation chamber is configured to have a substantially uniform cross sectional profile along its length. For example, the aerosol flow path along the length of the aerosol generation chamber may have the same cross-sectional area. Advantageously, this may reduce turbulence, as well as fluctuation in pressure in the aerosol flow path and thereby such arrangement may lead to an increase in the size of aerosol droplets.
Optionally, the smoking substitute apparatus further comprises a housing containing the aerosol generation chamber, wherein one or more electrical contacts are provided on a first end of the housing and electrically connected with the aerosol generator, and wherein the one or more electrical contacts are configured to engage with corresponding electrical terminals on a main body of a smoking substitute system. For example, electrical connectors may extend from the aerosol generator, through respective sealed apertures at the base of the aerosol generation chamber, to establish electrical connection with the one or more electrical contacts. Advantageously, such arrangement may allow electrical connection between the main body and the aerosol generator to establish by biasing the housing towards the main body.
Optionally, the smoking substitute apparatus further comprises a housing containing the aerosol generation chamber, wherein one or more electrical contacts have an electrically conductive surface which extends orthogonally to the longitudinal axis of the housing. For example, the electrically conductive surface may form from conductor strips, e.g., copper strips that extends partially across the first end of the housing. Advantageously, such arrangement may increase the surface area of the electrical contacts.
Alternatively, or in addition, one or more electrical contacts are provided on a sidewall of the housing and electrically connected with the aerosol generator, wherein the one or more electrical contacts are configured to engage with corresponding electrical terminals on a main body of a smoking substitute system. For example, electrical connectors may extend from the aerosol generator, through respective sealed apertures at the sidewalls of the aerosol generation chamber, to establish electrical connection with the one or more electrical contacts. Advantageously, such arrangement may allow electrical connection between the main body and the aerosol generator to establish by sliding the housing into a cavity of the main body.
Optionally, the one or more electrical contacts have an electrically conductive surface which is parallel to the longitudinal axis of the housing. For example, the electrically conductive surface may form from conductor strips, e.g., copper strips that extends along the sidewall of the housing. Advantageously, such arrangement may increase the surface area of the electrical contacts.
Optionally, the one or more electrical contacts are provided on an outer surface of the housing. For example, the electrical contacts may form on the external surface at the base of the housing, or they may form on the external surface at the sidewall of the housing. Advantageously, such arrangement may allow the one or more electrical contacts to establish connection with corresponding electrical contacts formed on an internal surface of a cavity of the main body.
Optionally, the one or more electrical contacts are resiliently movable for effecting a secure electrical connection with the corresponding electrical terminals on the main body. For example, the electrical contacts may form an interference fit with the corresponding electrical terminals of main body, whereby such interference fit may help retaining the housing within the main body.
The smoking substitute apparatus may be in the form of a consumable. The consumable may be configured for engagement with a main body. When the consumable is engaged with the main body, the combination of the consumable and the main body may form a smoking substitute system such as a closed smoking substitute system. For example, the consumable may comprise components of the system that are disposable, and the main body may comprise non-disposable or non-consumable components (e.g., power supply, controller, sensor, etc.) that facilitate the generation and/or delivery of aerosol by the consumable. In such an embodiment, the aerosol precursor (e.g., e-liquid) may be replenished by replacing a used consumable with an unused consumable.
Alternatively, the smoking substitute apparatus may be a non-consumable apparatus (e.g., that is in the form of an open smoking substitute system). In such embodiments an aerosol precursor (e.g., e-liquid) of the system may be replenished by re-filling, e.g., a reservoir of the smoking substitute apparatus, with the aerosol precursor (rather than replacing a consumable component of the apparatus).
In light of this, it should be appreciated that some of the features described herein as being part of the smoking substitute apparatus may alternatively form part of a main body for engagement with the smoking substitute apparatus. This may be the case in particular when the smoking substitute apparatus is in the form of a consumable.
Where the smoking substitute apparatus is in the form of a consumable, the main body and the consumable may be configured to be physically coupled together. For example, the consumable may be at least partially received in a recess of the main body, such that there is an interference fit between the main body and the consumable. Alternatively, the main body and the consumable may be physically coupled together by screwing one onto the other, or through a bayonet fitting, or the like.
Thus, the smoking substitute apparatus may comprise one or more engagement portions for engaging with a main body. In this way, one end of the smoking substitute apparatus may be coupled with the main body, whilst an opposing end of the smoking substitute apparatus may define a mouthpiece of the smoking substitute system.
The smoking substitute apparatus may comprise a reservoir configured to store an aerosol precursor, such as an e-liquid. The e-liquid may, for example, comprise a base liquid. The e-liquid may further comprise nicotine. The base liquid may include propylene glycol and/or vegetable glycerin. The e-liquid may be substantially flavorless. That is, the e-liquid may not contain any deliberately added additional flavorant and may consist solely of a base liquid of propylene glycol and/or vegetable glycerin and nicotine.
The reservoir may be in the form of a tank. At least a portion of the tank may be light-transmissive. For example, the tank may comprise a window to allow a user to visually assess the quantity of e-liquid in the tank. A housing of the smoking substitute apparatus may comprise a corresponding aperture (or slot) or window that may be aligned with a light-transmissive portion (e.g., window) of the tank. The reservoir may be referred to as a “clearomizer” if it includes a window, or a “cartomizer” if it does not.
The smoking substitute apparatus may comprise a passage for fluid flow therethrough. The passage may extend through (at least a portion of) the smoking substitute apparatus, from the chamber outlet to an outlet of the apparatus. The outlet may be at a mouthpiece of the smoking substitute apparatus. The passage may be at least partially defined by the tank. The tank may substantially (or fully) define the passage, for at least a part of the length of the passage. In this respect, the tank may surround the passage, e.g., in an annular arrangement around the passage.
The aerosol generator may comprise a wick. The aerosol generator may further comprise a heater. The wick may comprise a porous material, capable of wicking the aerosol precursor. A portion of the wick may be exposed in the aerosol generation chamber, however said portion of the wick may be spaced from the air flow path. The wick may also comprise one or more portions in contact with liquid stored in the reservoir. For example, opposing ends of the wick may protrude into the reservoir and an intermediate portion (between the ends) may extend across the aerosol generation chamber. Thus, liquid may be drawn (e.g., by capillary action) along the wick, from the reservoir to the portion of the wick exposed in the aerosol generation chamber.
The heater may comprise a heating element, which may be in the form of a filament wound about the wick (e.g., the filament may extend helically about the wick in a coil configuration). The heating element may be wound about the intermediate portion of the wick that is extended across the aerosol generation chamber. The heating element may be electrically connected (or connectable) to a power source. Thus, in operation, the power source may apply a voltage across the heating element so as to heat the heating element by resistive heating. This may cause liquid stored in the wick (i.e., drawn from the tank) to be heated so as to form a vapor in the aerosol generation chamber. This vapor may subsequently cool to form an aerosol in the aerosol generation chamber, typically downstream from the heating element.
As a user puffs on the mouthpiece, vaporized e-liquid may be drawn towards the chamber outlet. The vapor may cool, and thereby nucleate and/or condense to form a plurality of aerosol droplets, e.g., nicotine-containing aerosol droplets. A portion of these aerosol droplets may be delivered to and be absorbed at a target delivery site, e.g., a user's lung, whilst a portion of the aerosol droplets may instead adhere onto other parts of the user's respiratory tract, e.g., the user's oral cavity and/or throat. Typically, in some known smoking substitute apparatuses, the aerosol droplets as measured at the outlet of the passage, e.g., at the mouthpiece, may have a droplet size, d50, of less than 1 μm.
The particle droplet sizes, d50, of an aerosol may be measured by a laser diffraction technique. For example, the stream of aerosol output from the outlet of the passage may be drawn through a Malvern Spraytec laser diffraction system, where the intensity and pattern of scattered laser light are analyzed to calculate the size and size distribution of aerosol droplets. As will be readily understood, the particle size distribution may be expressed in terms of d10, d50 and d90, for example. Considering a cumulative plot of the volume of the particles measured by the laser diffraction technique, the d10 particle size is the particle size below which 10% by volume of the sample lies. The d50 particle size is the particle size below which 50% by volume of the sample lies. The d90 particle size is the particle size below which 90% by volume of the sample lies. Unless otherwise indicated herein, the particle size measurements are volume-based particle size measurements, rather than number-based or mass-based particle size measurements.
The smoking substitute apparatus (or main body engaged with the smoking substitute apparatus) may comprise a power source. The power source may be electrically connected (or connectable) to a heater of the smoking substitute apparatus (e.g., when the smoking substitute apparatus is engaged with the main body). The power source may be a battery (e.g., a rechargeable battery). A connector in the form of e.g., a USB port may be provided for recharging this battery.
When the smoking substitute apparatus is in the form of a consumable, the smoking substitute apparatus may comprise an electrical interface for interfacing with a corresponding electrical interface of the main body. One or both of the electrical interfaces may include one or more electrical contacts. Thus, when the main body is engaged with the consumable, the electrical interface of the main body may be configured to transfer electrical power from the power source to a heater of the consumable via the electrical interface of the consumable.
The electrical interface of the smoking substitute apparatus may also be used to identify the smoking substitute apparatus (in the form of a consumable) from a list of known types. For example, the consumable may have a certain concentration of nicotine and the electrical interface may be used to identify this. The electrical interface may additionally or alternatively be used to identify when a consumable is connected to the main body.
Again, where the smoking substitute apparatus is in the form of a consumable, the main body may comprise an identification means, which may, for example, be in the form of an RFID reader, a barcode or QR code reader. This identification means may be able to identify a characteristic (e.g., a type) of a consumable engaged with the main body. In this respect, the consumable may include any one or more of an RFID chip, a barcode or QR code, or memory within which is an identifier and which can be interrogated via the identification means.
The smoking substitute apparatus or main body may comprise a controller, which may include a microprocessor. The controller may be configured to control the supply of power from the power source to the heater of the smoking substitute apparatus (e.g., via the electrical contacts). A memory may be provided and may be operatively connected to the controller. The memory may include non-volatile memory. The memory may include instructions which, when implemented, cause the controller to perform certain tasks or steps of a method.
The main body or smoking substitute apparatus may comprise a wireless interface, which may be configured to communicate wirelessly with another device, for example a mobile device, e.g., via Bluetooth®. To this end, the wireless interface could include a Bluetooth® antenna. Other wireless communication interfaces, e.g., WIFI®, are also possible. The wireless interface may also be configured to communicate wirelessly with a remote server.
A puff sensor may be provided that is configured to detect a puff (i.e., inhalation from a user). The puff sensor may be operatively connected to the controller so as to be able to provide a signal to the controller that is indicative of a puff state (i.e., puffing or not puffing). The puff sensor may, for example, be in the form of a pressure sensor or an acoustic sensor. That is, the controller may control power supply to the heater of the consumable in response to a puff detection by the sensor. The control may be in the form of activation of the heater in response to a detected puff. That is, the smoking substitute apparatus may be configured to be activated when a puff is detected by the puff sensor. When the smoking substitute apparatus is in the form of a consumable, the puff sensor may be provided in the consumable or alternatively may be provided in the main body.
The term “flavorant” is used to describe a compound or combination of compounds that provide flavor and/or aroma. For example, the flavorant may be configured to interact with a sensory receptor of a user (such as an olfactory or taste receptor). The flavorant may include one or more volatile substances.
The flavorant may be provided in solid or liquid form. The flavorant may be natural or synthetic. For example, the flavorant may include menthol, licorice, chocolate, fruit flavor (including e.g., citrus, cherry etc.), vanilla, spice (e.g., ginger, cinnamon) and tobacco flavor. The flavorant may be evenly dispersed or may be provided in isolated locations and/or varying concentrations.
According to a second aspect there is provided a smoking substitute system for generating an aerosol, comprising:
Optionally, the main body comprises corresponding electrical terminals configured to engage with the one or more electrical contacts by a sliding fit. For example, the smoking substitute system may be configured such that electrical connections between the heater and the main body by sliding the housing into a cavity of the main body.
According to a third aspect there is provided a method of using the smoking substitute apparatus of the first aspect, comprising: generating an aerosol with the aerosol generator;
drawing on the apparatus to cause an air flow to enter the aerosol generation chamber and entrain the generated aerosol.
The present inventors consider that a flow rate of 1.3 L min−1 is towards the lower end of a typical user expectation of flow rate through a conventional cigarette and therefore through a user-acceptable smoking substitute apparatus. The present inventors further consider that a flow rate of 2.0 L min−1 is towards the higher end of a typical user expectation of flow rate through a conventional cigarette and therefore through a user-acceptable smoking substitute apparatus. Embodiments of the present disclosure therefore provide an aerosol with advantageous particle size characteristics across a range of flow rates of air through the apparatus.
The aerosol may have a Dv50 of at least 1.1 μm, at least 1.2 μm, at least 1.3 μm, at least 1.4 μm, at least 1.5 μm, at least 1.6 μm, at least 1.7 μm, at least 1.8 μm, at least 1.9 μm or at least 2.0 μm.
The aerosol may have a Dv50 of not more than 4.9 μm, not more than 4.8 μm, not more than 4.7 μm, not more than 4.6 μm, not more than 4.5 μm, not more than 4.4 μm, not more than 4.3 μm, not more than 4.2 μm, not more than 4.1 μm, not more than 4.0 μm, not more than 3.9 μm, not more than 3.8 μm, not more than 3.7 μm, not more than 3.6 μm, not more than 3.5 μm, not more than 3.4 μm, not more than 3.3 μm, not more than 3.2 μm, not more than 3.1 μm or not more than 3.0 μm.
A particularly preferred range for Dv50 of the aerosol is in the range 2-3 μm.
When the air flow rate inhaled by the user through the apparatus is 1.3 L min−1, the average magnitude of velocity of air in the vaporization chamber may be not more than 0.001 ms−1, or not more than 0.005 ms−1, or not more than 0.01 ms−1, or not more than 0.05 ms−1.
The aerosol generator may comprise a vaporizer element loaded with aerosol precursor, the vaporizer element being heatable by a heater and presenting a vaporizer element surface to air in the vaporization chamber. A vaporizer element region may be defined as a volume extending outwardly from the vaporizer element surface to a distance of 1 mm from the vaporizer element surface.
The air inlet, flow passage, outlet and the vaporization chamber may be configured so that, when the air flow rate inhaled by the user through the apparatus is 1.3 L min−1, the average magnitude of velocity of air in the vaporizer element region is in the range 0-1.2 ms−1. The average magnitude of velocity of air in the vaporizer element region may be calculated using computational fluid dynamics.
When the air flow rate inhaled by the user through the apparatus is 1.3 L min−1, the average magnitude of velocity of air in the vaporizer element region may be not more than 0.001 ms−1, or not more than 0.005 ms−1, or not more than 0.01 ms−1, or not more than 0.05 ms−1.
When the average magnitude of velocity of air in the vaporizer element region is in the ranges specified, it is considered that the resultant aerosol particle size is advantageously controlled to be in a desirable range. It is further considered that the velocity of air in the vaporizer element region is more relevant to the resultant particle size characteristics than consideration of the velocity in the vaporization chamber as a whole. This is in view of the significant effect of the velocity of air in the vaporizer element region on the cooling of the vapor emitted from the vaporizer element surface.
Additionally, or alternatively is it relevant to consider the maximum magnitude of velocity of air in the vaporizer element region.
Therefore, the air inlet, flow passage, outlet and the vaporization chamber may be configured so that, when the air flow rate inhaled by the user through the apparatus is 1.3 L min−1, the maximum magnitude of velocity of air in the vaporizer element region is in the range 0-2.0 ms−1.
When the air flow rate inhaled by the user through the apparatus is 1.3 L min−1, the maximum magnitude of velocity of air in the vaporizer element region may be not more than 0.001 ms−1, or not more than 0.005 ms−1, or not more than 0.01 ms−1, or not more than 0.05 ms−1.
It is considered that configuring the apparatus in a manner to permit such control of velocity of the airflow at the vaporizer permits the generation of aerosols with particularly advantageous particle size characteristics, including Dv50 values.
Additionally, or alternatively is it relevant to consider the turbulence intensity in the vaporizer chamber in view of the effect of turbulence on the particle size of the generated aerosol. For example, the air inlet, flow passage, outlet and the vaporization chamber may be configured so that, when the air flow rate inhaled by the user through the apparatus is 1.3 L min−1, the turbulence intensity in the vaporizer element region is not more than 1%.
When the air flow rate inhaled by the user through the apparatus is 1.3 L min−1, the turbulence intensity in the vaporizer element region may be not more than 0.95%, not more than 0.9%, not more than 0.85%, not more than 0.8%, not more than 0.75%, not more than 0.7%, not more than 0.65% or not more than 0.6%.
It is considered that configuring the apparatus in a manner to permit such control of the turbulence intensity in the vaporizer element region permits the generation of aerosols with particularly advantageous particle size characteristics, including Dv50 values.
Following detailed investigations, the inventors consider, without wishing to be bound by theory, that the particle size characteristics of the generated aerosol may be determined by the cooling rate experienced by the vapor after emission from the vaporizer element (e.g., wick). In particular, it appears that imposing a relatively slow cooling rate on the vapor has the effect of generating aerosols with a relatively large particle size. The parameters discussed above (velocity and turbulence intensity) are considered to be mechanisms for implementing a particular cooling dynamic to the vapor.
More generally, it is considered that the air inlet, flow passage, outlet and the vaporization chamber may be configured so that a desired cooling rate is imposed on the vapor. The particular cooling rate to be used depends of course on the nature of the aerosol precursor and other conditions. However, for a particular aerosol precursor it is possible to define a set of testing conditions in order to define the cooling rate, and by extension this imposes limitations on the configuration of the apparatus to permit such cooling rates as are shown to result in advantageous aerosols. Accordingly, the air inlet, flow passage, outlet and the vaporization chamber may be configured so that the cooling rate of the vapor is such that the time taken to cool to 50° C. is not less than 16 ms, when tested according to the following protocol. The aerosol precursor is an e-liquid consisting of 1.6% freebase nicotine and the remainder a 65:35 propylene glycol and vegetable glycerin mixture, the e-liquid having a boiling point of 209° C. Air is drawn into the air inlet at a temperature of 25° C. The vaporizer is operated to release a vapor of total particulate mass 5 mg over a 3 second duration from the vaporizer element surface in an air flow rate between the air inlet and outlet of 1.3 L min−1.
Additionally, or alternatively, the air inlet, flow passage, outlet and the vaporization chamber may be configured so that the cooling rate of the vapor is such that the time taken to cool to 50° C. is not less than 16 ms, when tested according to the following protocol. The aerosol precursor is an e-liquid consisting of 1.6% freebase nicotine and the remainder a 65:35 propylene glycol and vegetable glycerin mixture, the e-liquid having a boiling point of 209° C. Air is drawn into the air inlet at a temperature of 25° C. The vaporizer is operated to release a vapor of total particulate mass 5 mg over a 3 second duration from the vaporizer element surface in an air flow rate between the air inlet and outlet of 2.0 L min−1.
Cooling of the vapor such that the time taken to cool to 50° C. is not less than 16 ms corresponds to an equivalent linear cooling rate of not more than 10° C./ms.
The equivalent linear cooling rate of the vapor to 50° C. may be not more than 9° C./ms, not more than 8° C./ms, not more than 7° C./ms, not more than 6° C./ms or not more than 5° C./ms.
Cooling of the vapor such that the time taken to cool to 50° C. is not less than 32 ms corresponds to an equivalent linear cooling rate of not more than 5° C./ms.
The testing protocol set out above considers the cooling of the vapor (and subsequent aerosol) to a temperature of 50° C. This is a temperature which can be considered to be suitable for an aerosol to exit the apparatus for inhalation by a user without causing significant discomfort. It is also possible to consider cooling of the vapor (and subsequent aerosol) to a temperature of 75° C. Although this temperature is possibly too high for comfortable inhalation, it is considered that the particle size characteristics of the aerosol are substantially settled by the time the aerosol cools to this temperature (and they may be settled at still higher temperature).
Accordingly, the air inlet, flow passage, outlet and the vaporization chamber may be configured so that the cooling rate of the vapor is such that the time taken to cool to 75° C. is not less than 4.5 ms, when tested according to the following protocol. The aerosol precursor is an e-liquid consisting of 1.6% freebase nicotine and the remainder a 65:35 propylene glycol and vegetable glycerin mixture, the e-liquid having a boiling point of 209° C. Air is drawn into the air inlet at a temperature of 25° C. The vaporizer is operated to release a vapor of total particulate mass 5 mg over a 3 second duration from the vaporizer element surface in an air flow rate between the air inlet and outlet of 1.3 L min−1.
Additionally, or alternatively, the air inlet, flow passage, outlet and the vaporization chamber may be configured so that the cooling rate of the vapor is such that the time taken to cool to 75° C. is not less than 4.5 ms, when tested according to the following protocol. The aerosol precursor is an e-liquid consisting of 1.6% freebase nicotine and the remainder a 65:35 propylene glycol and vegetable glycerin mixture, the e-liquid having a boiling point of 209° C. Air is drawn into the air inlet at a temperature of 25° C. The vaporizer is operated to release a vapor of total particulate mass 5 mg over a 3 second duration from the vaporizer element surface in an air flow rate between the air inlet and outlet of 2.0 L min−1.
Cooling of the vapor such that the time taken to cool to 75° C. is not less than 4.5 ms corresponds to an equivalent linear cooling rate of not more than 30° C./ms.
The equivalent linear cooling rate of the vapor to 75° C. may be not more than 29° C./ms, not more than 28° C./ms, not more than 27° C./ms, not more than 26° C./ms, not more than 25° C./ms, not more than 24° C./ms, not more than 23° C./ms, not more than 22° C./ms, not more than 21° C./ms, not more than 20° C./ms, not more than 19° C./ms, not more than 18° C./ms, not more than 17° C./ms, not more than 16° C./ms, not more than 15° C./ms, not more than 14° C./ms, not more than 13° C./ms, not more than 12° C./ms, not more than 11° C./ms or not more than 10° C./ms.
Cooling of the vapor such that the time taken to cool to 75° C. is not less than 13 ms corresponds to an equivalent linear cooling rate of not more than 10° C./ms.
It is considered that configuring the apparatus in a manner to permit such control of the cooling rate of the vapor permits the generation of aerosols with particularly advantageous particle size characteristics, including Dv50 values.
The disclosure includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.
So that the disclosure may be understood, and so that further aspects and features thereof may be appreciated, embodiments illustrating the principles of the disclosure will now be discussed in further detail with reference to the accompanying figures, in which:
Further background to the present disclosure and further aspects and embodiments of the present disclosure will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. The contents of all documents mentioned in this text are incorporated herein by reference in their entirety.
As is apparent from
The system 110 is configured to vaporize an aerosol precursor, which in the illustrated embodiment is in the form of a nicotine-based e-liquid 160. The e-liquid 160 comprises nicotine and a base liquid including propylene glycol and/or vegetable glycerin. In the present embodiment, the e-liquid 160 is flavored by a flavorant. In other embodiments, the e-liquid 160 may be flavorless and thus may not include any added flavorant.
In other embodiments, the e-liquid (i.e., aerosol precursor) may be the only part of the system that is truly “single-use”. That is, the tank may be refillable with e-liquid or the e-liquid may be stored in a non-consumable component of the system. For example, in such other embodiments, the e-liquid may be stored in a tank located in the main body or stored in another component that is itself not single-use (e.g., a refillable cartomizer).
The external wall of tank 152 is provided by a casing of the consumable 150. The tank 152 annularly surrounds, and thus defines a portion of, a passage 170 that extends between a vaporizer inlet 172 and an outlet 174 at opposing ends of the consumable 150. In this respect, the passage 170 comprises an upstream end at the end of the consumable 150 that engages with the main body 120, and a downstream end at an opposing end of the consumable 150 that comprises a mouthpiece 154 of the system 110.
When the consumable 150 is received in the cavity of the main body 120 as shown in
When the consumable 150 is engaged with the main body 120, a user can inhale (i.e., take a puff) via the mouthpiece 154 so as to draw air through the passage 170, and so as to form an air flow (indicated by the dashed arrows in
The smoking substitute system 110 is configured to vaporize the e-liquid 160 for inhalation by a user. To provide this operability, the consumable 150 comprises an aerosol generator for example a heater, the heater having a porous wick 162 and a resistive heating element in the form of a heating filament 164 that is helically wound (in the form of a coil) around a portion of the porous wick 162. The porous wick 162 extends across the passage 170 (i.e., transverse to a longitudinal axis of the passage 170 and thus also transverse to the air flow along the passage 170 during use) and opposing ends of the wick 162 extend into the tank 152 (so as to be immersed in the e-liquid 160). In this way, e-liquid 160 contained in the tank 152 is conveyed from the opposing ends of the porous wick 162 to a central portion of the porous wick 162 so as to be exposed to the air flow in the passage 170.
The helical filament 164 is wound about the exposed central portion of the porous wick 162 and is electrically connected to an electrical interface in the form of electrical contacts 156 mounted at the end of the consumable that is proximate the main body 120 (when the consumable and the main body are engaged). When the consumable 150 is engaged with the main body 120, electrical contacts 156 make contact with corresponding electrical contacts (not shown) of the main body 120. The main body electrical contacts are electrically connectable to a power source (not shown) of the main body 120, such that (in the engaged position) the filament 164 is electrically connectable to the power source. In this way, power can be supplied by the main body 120 to the filament 164 in order to heat the filament 164. This heats the porous wick 162 which causes e-liquid 160 conveyed by the porous wick 162 to vaporize and thus to be released from the porous wick 162. The vaporized e-liquid becomes entrained in the air flow and, as it cools in the air flow (between the heated wick and the outlet 174 of the passage 170), condenses to form an aerosol. This aerosol is then inhaled, via the mouthpiece 154, by a user of the system 110. As e-liquid is lost from the heated portion of the wick, further e-liquid is drawn along the wick from the tank to replace the e-liquid lost from the heated portion of the wick.
The filament 164 and the exposed central portion of the porous wick 162 are positioned across the passage 170. More specifically, the part of passage that contains the filament 164 and the exposed portion of the porous wick 162 forms a vaporization chamber, or aerosol generation chamber. In the illustrated example, the aerosol generation chamber has the same cross-sectional diameter as the passage 170. However, in other embodiments the aerosol generation chamber may have a different cross sectional profile as the passage 170. For example, the aerosol generation chamber may have a larger cross sectional diameter than at least some of the downstream part of the passage 170 so as to enable a longer residence time for the air inside the aerosol generation chamber.
When the user inhales, air is drawn from through the inlets 176 shown in
At substantially the same time as the air flow passes around the porous wick 162, the filament 164 is heated so as to vaporize the e-liquid which has been wicked into the porous wick. The air flow passing around the porous wick 162 picks up this vaporized e-liquid, and the vapor-containing air flow is drawn in direction 403 further down passage 170.
The power source of the main body 120 may be in the form of a battery (e.g., a rechargeable battery such as a lithium-ion battery). The main body 120 may comprise a connector in the form of e.g., a USB port for recharging this battery. The main body 120 may also comprise a controller that controls the supply of power from the power source to the main body electrical contacts (and thus to the filament 164). That is, the controller may be configured to control a voltage applied across the main body electrical contacts, and thus the voltage applied across the filament 164. In this way, the filament 164 may only be heated under certain conditions (e.g., during a puff and/or only when the system is in an active state). In this respect, the main body 120 may include a puff sensor (not shown) that is configured to detect a puff (i.e., inhalation). The puff sensor may be operatively connected to the controller so as to be able to provide a signal, to the controller, which is indicative of a puff state (i.e., puffing or not puffing). The puff sensor may, for example, be in the form of a pressure sensor or an acoustic sensor.
Although not shown, the main body 120 and consumable 150 may comprise a further interface which may, for example, be in the form of an RFID reader, a barcode or QR code reader. This interface may be able to identify a characteristic (e.g., a type) of a consumable 150 engaged with the main body 120. In this respect, the consumable 150 may include any one or more of an RFID chip, a barcode or QR code, or memory within which is an identifier and which can be interrogated via the interface.
The consumable 250 comprises a housing which defines an aerosol generation chamber 280 at a first end of the housing. The aerosol generation chamber 280 and housing shares the same longitudinal axis along a dashed line as shown in
As shown in
The aerosol generation chamber 280 further comprises a chamber outlet 282 opened towards an outlet (not shown) at the second end of the housing opposite the first end. The second end of the consumable 250 comprises a mouthpiece 254 onto which a user may puff, in order to draw an air flow through the chamber inlets 272 and aerosol generation chamber 280 before exhausting through the chamber outlet 282 and the outlet. Substantially all of the air flow entering the chamber inlet is directed away from the heater. The flow path of the air flow 412 is shown as solid arrows in
As clearly illustrated in
In some other embodiments, the base of aerosol generation chamber may permit only an insignificant amount of air to ingress into the aerosol generation chamber, e.g., through a gap or an aperture formed at said base.
As aerosol precursor is vaporized from the heated portion of the wick, further aerosol precursor is drawn along the wick from the tank to replace said vaporized aerosol precursor. In some cases, excess aerosol precursor may be drawn, by momentum or by gravity, into the wick and subsequently collected in the aerosol generation chamber 280, e.g., at the base of the aerosol generation chamber 280. Such arrangement may reduce or eliminate excess aerosol precursor in the porous wick 262 leaking through the consumable 250, e.g., said excess aerosol precursor is retained and subsequently collected at the base of aerosol generation chamber by gravity.
In contrast with the consumable 150 as shown in
In the illustrated embodiment, the aerosol generation chamber is configured to have a length of 20 mm and a volume of 680 mm3. In other embodiments the aerosol generation chamber may be configured to have an internal volume ranging between 68 mm3 to 680 mm3, wherein the length of the aerosol generation chamber may range between 2 mm to 20 mm.
In the illustrated embodiment, the heater is positioned at the base 284 of the aerosol generation chamber 280, e.g., the heater is spaced from the chamber inlets 272. Such arrangement may reduce the amount of air flow that may interact with the heater, and therefore it may minimize the amount of turbulence in the vicinity of the heater. Furthermore, such arrangement may increase the residence time of vapor in the stagnant aerosol generation chamber 280 for the vapor to cool and condense, and thereby it may result in the formation of larger aerosol droplets. Additionally, such arrangement may allow excess aerosol precursor collected at the base of the aerosol generation chamber to be absorbed into the wick, and thereby reduces the likelihood of leakage of said excess aerosol precursor.
In some other embodiments, the heater may be positioned adjacent to, or immediately upstream of, the chamber inlets along the longitudinal axis of the housing, and therefore that the flow path of aerosol from the heater to merge with the air flow may be shortened. This may allow aerosol to entrain with the air flow in a more efficient manner.
When the consumable 250 is put in an upright orientation, a region of the aerosol generation chamber 280 level with and below the aerosol generator is sealed against air flow into and out of the chamber 280. This differs to the reference arrangement as shown in
In
The electrical contacts 356 have an electrically conductive surface which is parallel to the longitudinal axis of the housing. The corresponding electrical contacts 359 have an electrically conductive surface which is parallel to the longitudinal axis of the main body 320. The electrical contacts 356 and corresponding electrical contacts 359 lie against one another in the engaged position. The electrical contacts 356 and corresponding electrical contacts 359 may physically slide against one another as the consumable 350 is moved into the engaged position. One, or both, of the electrical contacts 356 and corresponding electrical contacts 359 may be resiliently movable in the radial direction. For example, the electrical contacts 356 and corresponding electrical contacts 359 may comprise a cantilever spring or coil spring. The resilient movement may help to ensure a secure electrical connection. The electrical contacts 356 may have the same configuration as corresponding electrical contacts 359.
As illustrated in
In other embodiments, the electrical contacts are provided on an external surface at the side of consumable housing and corresponding electrical contacts are provided on an internal surface at the side of the cavity of the main body. The electrical contacts and corresponding electrical contacts may overlay and press against one another in an axial direction (i.e., parallel to the longitudinal axis of the housing or of the main body) in the engaged position. One, or both, of the electrical connects and corresponding electrical contacts may be resiliently movable in the axial direction. For example, as the consumable is moved into the engaged position, corresponding contacts in the cavity are movable axially inwardly, while continuing to exert a force against electrical contacts of the consumable. The resilient movement may help to ensure a secure electrical connection. The electrical contacts may have the same configuration as corresponding electrical contacts.
There now follows a disclosure of certain examples of experimental work undertaken to determine the effects of certain conditions in the smoking substitute apparatus on the particle size of the generated aerosol. However, the present disclosure is to be understood to not be limited in its application to the specific experimentation, results, and laboratory procedures disclosed herein after. Rather, the Examples are simply provided as one of various embodiments and are meant to be exemplary, not exhaustive.
The experimental work described in this example is relevant to the embodiments disclosed above in view of the “stagnant chamber” nature of the embodiments. The experimental work described in this example shows that control over the flow conditions at the wick has an effect on the particle size of the generated aerosol.
Introduction
Aerosol droplet size is a considered to be an important characteristic for smoking substitution devices. Droplets in the range of 2-5 μm are preferred in order to achieve improved nicotine delivery efficiency and to minimize the hazard of second-hand smoking. However, at the time of writing (September 2019), commercial EVP devices typically deliver aerosols with droplet size averaged around 0.5 μm, and to the knowledge of the inventors not a single commercially available device can deliver an aerosol with an average particle size exceeding 1 μm.
The present inventors speculate, without themselves wishing to be bound by theory, that there has to date been a lack of understanding in the mechanisms of e-liquid evaporation, nucleation and droplet growth in the context of aerosol generation in smoking substitute devices. The present inventors have therefore studied these issues in order to provide insight into mechanisms for the generation of aerosols with larger particles. The present inventors have carried out experimental and modelling work described in this example alongside theoretical investigations, leading to significant achievements as now reported.
This disclosure considers the roles of air velocity, air turbulence and vapor cooling rate in affecting aerosol particle size.
In this work, a Malvern PANalytical Spraytec laser diffraction system was employed for the particle size measurement. In order to limit the number of variables, the same coil and wick (1.5 ohms Ni—Cr coil, 1.8 mm Y07 cotton wick), the same e-liquid (1.6% freebase nicotine, 65:35 propylene glycol (PG)/vegetable glycerin (VG) ratio, no added flavor) and the same input power (10 W) were used in all experiments described in this example. Y07 represents the grade of cotton wick, meaning that the cotton has a linear density of 0.7 grams per meter.
Particle sizes were measured in accordance with ISO 13320:2009(E), which is an international standard on laser diffraction methods for particle size analysis. This is particularly well suited to aerosols, because there is an assumption in this standard that the particles are spherical (which is a good assumption for liquid-based aerosols). The standard is stated to be suitable for particle sizes in the range 0.1 micron to 3 mm.
The results presented here concentrate on the volume-based median particle size Dv50. This is to be taken to be the same as the parameter d50 used above.
Rectangular Tube Testing
The work reported here based on the inventors' insight that aerosol particle size might be related to: 1) air velocity; 2) flow rate; and 3) Reynolds number. In a given EVP device, these three parameters are inter-linked to each other, making it difficult to draw conclusions on the roles of each individual factor. In order to decouple these factors, experiments in this example were carried out using a set of rectangular tubes having different dimensions. These were manufactured by 3D printing. The rectangular tubes were 3D printed in an MJP 2500 3D printer.
The rectangular tubes were manufactured to have same internal depth of 6 mm in order to accommodate the standardized coil and wick, however the tube internal width varied from 4.5 mm to 50 mm. In this disclosure, the “tube size” is referred to as the internal width of rectangular tubes.
The rectangular tubes with different dimensions were used to generate aerosols that were tested for particle size in a Malvern PANalytical Spraytec laser diffraction system. An external digital power supply was dialed to 2.6 A constant current to supply 10 W power to the heater coil in all experiments described in this example. Between two runs, the wick was saturated manually by applying one drop of e-liquid on each side of the wick.
Three groups of experiments were carried out in this example:
1.3 lpm (liters per minute, L min−1 or LPM) constant flow rate on different size tubes 2.0 lpm constant flow rate on different size tubes 1 m/s constant air velocity on 3 tubes: i) 5 mm tube at 1.4 lpm flow rate; ii) 8 mm tube at 2.8 lpm flow rate; and iii) 20 mm tube at 8.6 lpm flow rate.
Table 1 shows a list of experiments in this example. The values in the “calculated air velocity” column were obtained by simply dividing the flow rate by the intersection area at the center plane of wick. Reynolds numbers (Re) were calculated through the following equation:
where: ρ is the density of air (1.225 kg/m3); ν is the calculated air velocity in table 1; μ is the viscosity of air (1.48×10−5 m2/s); L is the characteristic length calculated by:
where: P is the perimeter of the flow path's intersection, and A is the area of the flow path's intersection.
Five repetition runs were carried out for each tube size and flow rate combination. Between adjacent runs there were at least 5 minutes wait time for the Spraytec system to be purged. In each run, real time particle size distributions were measured in the Spraytec laser diffraction system at a sampling rate of 2500 per second, the volume distribution median (Dv50) was averaged over a puff duration of 4 seconds. Measurement results were averaged and the standard deviations were calculated to indicate errors as shown in section 4 below.
Turbulence Tube Testing
The Reynolds numbers in Table 1 are all well below 1000, therefore, it is considered fair to assume all the experiments described in this example would be under conditions of laminar flow. Further experiments were carried out in this example and reported in this section to investigate the role of turbulence.
Turbulence intensity was introduced as a quantitative parameter to assess the level of turbulence. The definition and simulation of turbulence intensity is discussed below.
Different device designs were considered in order to introduce turbulence. In the experiments described in this example, jetting panels were added in the existing 12 mm rectangular tubes upstream of the wick. This approach enables direct comparison between different devices as they all have highly similar geometry, with turbulence intensity being the only variable.
For each of
These four devices were operated to generate aerosols following the procedure explained above using a flow rate of 1.3 lpm and the generated aerosols were tested for particle size in the Spraytec laser diffraction system.
High Temperature Testing
The experiment described in this example aimed to investigate the influence of inflow air temperature on aerosol particle size, in order to investigate the effect of vapor cooling rate on aerosol generation.
The experimental set up is shown in
Three smoking substitute apparatuses (referred to as “pods”) were tested in the study: pod 1 is the commercially available “myblu optimized” pod (
Pod 1, shown in longitudinal cross sectional view (in the width plane) in
Pod 2, shown in longitudinal cross sectional view (in the width plane) in
All three pods were filled with the same e-liquid (1.6% freebase nicotine, 65:35 PG/VG ratio, no added flavor). Three experiments described in this example were carried out for each pod: 1) standard measurement in ambient temperature; 2) only the inlet air was heated to 50° C.; and 3) both the inlet air and the pods were heated to 50° C. Five repetition runs were carried out for each experiment and the Dv50 results were taken and averaged.
Modelling Work
In this study, modelling work was performed using COMSOL Multiphysics 5.4, engaged physics include: 1) laminar single-phase flow; 2) turbulent single-phase flow; 3) laminar two-phase flow; 4) heat transfer in fluids; and (5) particle tracing. Data analysis and data visualization were mostly completed in MATLAB R2019a.
Velocity Modelling
Air velocity in the vicinity of the wick is believed to play an important role in affecting particle size. In this example, the air velocity was calculated by dividing the flow rate by the intersection area, which is referred to as “calculated velocity” in this work. This involves a very crude simplification that assumes velocity distribution to be homogeneous across the intersection area.
In order to increase reliability of the work, computational fluid dynamics (CFD) modelling was performed to obtain more accurate velocity values.
The average velocity in the vicinity of the wick (defined as a volume from the wick surface to 1 mm away from the wick surface).
The maximum velocity in the vicinity of the wick (defined as a volume from the wick surface to 1 mm away from the wick surface).
The CFD model uses a laminar single-phase flow setup. For each experiment described in this example, the outlet was configured to a corresponding flowrate, the inlet was configured to be pressure-controlled, the wall conditions were set as “no slip”. A 1 mm wide ring-shaped domain (wick vicinity) was created around the wick surface, and domain probes were implemented to assess the average and maximum magnitudes of velocity in this ring-shaped wick vicinity domain.
The CFD model outputs the average velocity and maximum velocity in the vicinity of the wick for each set of experiments carried out in the above example. The outcomes are reported in Table 2.
Turbulence Modelling
Turbulence intensity (l) is a quantitative value that represents the level of turbulence in a fluid flow system. It is defined as the ratio between the root-mean-square of velocity fluctuations, u′, and the Reynolds-averaged mean flow velocity, U:
where ux, uy and uz are the x-, y- and z-components of the velocity vector,
Higher turbulence intensity values represent higher levels of turbulence. As a rule of thumb, turbulence intensity below 1% represents a low-turbulence case, turbulence intensity between 1% and 5% represents a medium-turbulence case, and turbulence intensity above 5% represents a high-turbulence case.
In this study, turbulence intensity was obtained from CFD simulation using turbulent single-phase setup in COMSOL Multiphysics. For each of the four experiments described in this example, the outlet was set to 1.3 lpm, the inlet was set to be pressure-controlled, and all wall conditions were set to be “no slip”.
Turbulence intensity was assessed within the volume up to 1 mm away from the wick surface (defined as the wick vicinity domain). For the four experiments described in this example, the turbulence intensities are 0.55%, 0.77%, 1.06% and 1.34%, respectively, as also shown in
Cooling Rate Modelling
The cooling rate modelling involves three coupling models in COMSOL Multiphysics: 1) laminar two-phase flow; 2) heat transfer in fluids, and 3) particle tracing. The model is setup in three steps:
Set Up Two Phase Flow Model
Laminar mixture flow physics was selected in this study. The outlet was configured in the same way as in the example above. However, this model includes two fluid phases released from two separate inlets: the first one is the vapor released from wick surface, at an initial velocity of 2.84 cm/s (calculated based on 5 mg total particulate mass over 3 seconds puff duration) with initial velocity direction normal to the wick surface; the second inlet is air influx from the base of tube, the rate of which is pressure-controlled.
Set Up Two-Way Coupling with Heat Transfer Physics
The inflow and outflow settings in heat transfer physics was configured in the same way as in the two-phase flow model. The air inflow was set to 25° C., and the vapor inflow was set to 209° C. (boiling temperature of the e-liquid formulation). In the end, the heat transfer physics is configured to be two-way coupled with the laminar mixture flow physics. The above model reaches steady state after approximately 0.2 second with a step size of 0.001 second.
Set Up Particle Tracing
A wave of 2000 particles were release from wick surface at t=0.3 second after the two-phase flow and heat transfer model has stabilized. The particle tracing physics has one-way coupling with the previous model, which means the fluid flow exerts dragging force on the particles, whereas the particles do not exert counterforce on the fluid flow. Therefore, the particles function as moving probes to output vapor temperature at each timestep.
The model outputs average vapor temperature at each time steps. A MATLAB script was then created to find the time step when the vapor cools to a target temperature (50° C. or 75° C.), based on which the vapor cooling rates were obtained (Table 3).
Results and Discussions
Particle size measurement results for the rectangular tube testing are shown in Table 4. For every tube size and flow rate combination, five repetition runs were carried out in the Spraytec laser diffraction system. The Dv50 values from five repetition runs were averaged, and the standard deviations were calculated to indicate errors, as shown in Table 4.
In this example, the roles of different factors affecting aerosol particle size will be discussed based on experimental and modelling results described in this example.
Decouple the Factors Affecting Particle Size
The particle size (Dv50) experimental results described in this example are plotted against calculated air velocity in
Different size tubes were tested at two flow rates: 1.3 lpm and 2.0 lpm. Both groups of data show the same trend that slower air velocity leads to larger particle size. The conclusion was made more convincing by the fact that these two groups of data overlap well in
In addition,
The above results lead to a strong conclusion that air velocity is an important factor affecting the particle size of EVP devices. Relatively large particles are generated when the air travels with slower velocity around the wick. It can also be concluded that flow rate, tube size and Reynolds number are not necessarily independently relevant to particle size, providing the air velocity is controlled in the vicinity of the wick.
Further Consideration of Velocity
In
The particle size measurement data were plotted against the average velocity (
The data in these two graphs indicates that in order to obtain an aerosol with Dv50 larger than 1 μm, the average velocity should be less than or equal to 1.2 m/s in the vicinity of the wick and the maximum velocity should be less than or equal to 2.0 m/s in the vicinity of the wick.
Furthermore, in order to obtain an aerosol with Dv50 of 2 μm or larger, the average velocity should be less than or equal to 0.6 m/s in the vicinity of the wick and the maximum velocity should be less than or equal to 1.2 m/s in the vicinity of the wick.
It is considered that typical commercial EVP devices deliver aerosols with Dv50 around 0.5 μm, and there is no commercially available device that can deliver aerosol with Dv50 exceeding 1 μm. It is considered that typical commercial EVP devices have average velocity of 1.5-2.0 m/s in the vicinity of the wick.
The Role of Turbulence
The role of turbulence has been investigated in terms of turbulence intensity, which is a quantitative characteristic that indicates the level of turbulence. In this work, four tubes of different turbulence intensities were used to general aerosols which were measured in the Spraytec laser diffraction system. The particle size (Dv50) experimental results described in this example are plotted against turbulence intensity in
The graph suggests a correlation between particle size and turbulence intensity, that lower turbulence intensity is beneficial for obtaining larger particle size. It is noted that when turbulence intensity is above 1% (medium-turbulence case), there are relatively large measurement fluctuations. In
The results clearly indicate that laminar air flow is favorable for the generation of aerosols with larger particles, and that the generation of large particle sizes is jeopardized by introducing turbulence. In
Vapor Cooling Rate
Without wishing to be bound by theory, the results are in line with the inventors' insight that control over the vapor cooling rate provides an important degree of control over the particle size of the aerosol. As reported above, the use of a slow air velocity can have the result of the formation of an aerosol with large Dv50. It is considered that this is due to slower air velocity allowing a slower cooling rate of the vapor.
Another conclusion related to laminar flow can also be explained by a cooling rate theory: laminar flow allows slow and gradual mixing between cold air and hot vapor, which means the vapor can cool down in slower rate when the airflow is laminar, resulting in larger particle size.
The results in
Further Consideration of Vapor Cooling Rate
In this example, the vapor cooling rates for each tube size and flow rate combination were obtained via multiphysics simulation. In
The data in these graphs indicates that in order to obtain an aerosol with Dv50 larger than 1 μm, the apparatus should be operable to require more than 16 ms for the vapor to cool to 50° C., or an equivalent (simplified to an assumed linear) cooling rate being slower than 10° C./ms. From an alternative viewpoint, in order to obtain an aerosol with Dv50 larger than 1 μm, the apparatus should be operable to require more than 4.5 ms for the vapor to cool to 75° C., or an equivalent (simplified to an assumed linear) cooling rate slower than 30° C./ms.
Furthermore, in order to obtain an aerosol with Dv50 of 2 μm or larger, the apparatus should be operable to require more than 32 ms for the vapor to cool to 50° C., or an equivalent (simplified to an assumed linear) cooling rate being slower than 5° C./ms. From an alternative viewpoint, in order to obtain an aerosol with Dv50 of 2 μm or larger, the apparatus should be operable to require more than 13 ms for the vapor to cool to 75° C., or an equivalent (simplified to an assumed linear) cooling rate slower than 10° C./ms.
Conclusions of Particle Size Examples
In this work, particle size (Dv50) of aerosols generated in a set of rectangular tubes was studied in order to decouple different factors (flow rate, air velocity, Reynolds number, tube size) affecting aerosol particle size. It is considered that air velocity is an important factor affecting particle size—slower air velocity leads to larger particle size. When air velocity was kept constant, the other factors (flow rate, Reynolds number, tube size) has low influence on particle size.
The role of turbulence was also investigated. It is considered that laminar air flow favors generation of large particles, and introducing turbulence deteriorates (reduces) the particle size.
Modelling methods were used to simulate the average air velocity, the maximum air velocity, and the turbulence intensity in the vicinity of the wick. A COMSOL model with three coupled physics has also been developed to obtain the vapor cooling rate.
All experimental and modelling results described in these examples support a cooling rate theory that slower vapor cooling rate is a significant factor in ensuring larger particle size. Slower air velocity, laminar air flow and higher inlet air temperature lead to larger particle size, because they all allow vapor to cool down at slower rates.
The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilized for realizing the disclosure in diverse forms thereof.
While the disclosure has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the disclosure set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the disclosure.
For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.
Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.
Throughout this specification, including the claims which follow, unless the context requires otherwise, the words “have”, “comprise”, and “include”, and variations such as “having”, “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means, for example, +/−10%.
The words “preferred” and “preferably” are used herein refer to embodiments of the disclosure that may provide certain benefits under some circumstances. It is to be appreciated, however, that other embodiments may also be preferred under the same or different circumstances. The recitation of one or more preferred embodiments therefore does not mean or imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure, or from the scope of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19198651.2 | Sep 2019 | EP | regional |
This application is a non-provisional application claiming benefit to the international application no. PCT/EP2020/076261 filed on Sep. 21, 2020, which claims priority to EP 19198651.2 filed on Sep. 20, 2019. The entire contents of each of the above-referenced applications are hereby incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP20/76261 | Sep 2020 | US |
| Child | 17685101 | US |
