Patent Application
20100077792
Lubricants and lubricant control systems consisting of electrostatic or electromagnetic devices within thermodynamic cycles for air conditioning, refrigeration, or power generating systems.
Various embodiments relate to operable modes for generating power, cooling, or heating utilizing a wide range of thermodynamic cycles from Rankine, Brayton, to Goswami cycles to optimize the energy efficiency associated with the power production or consumption, and to increase the operating lifetimes of the components with moving parts by reducing friction. Many such known methods are present in the art ranging from magnetic bearings to gas bearings, though virtually all of these methods are subject to limited number of start/stop cycles. Additional more traditional methods ranging from oil bearings utilizing traditional lubricants have other limitations ranging from temperature to adverse impact of heat transfer within a thermodynamic cycle's heat exchangers.
A lubricant system that overcomes the cost, lifetime, or efficiency limitations as noted would be of great utility for many high value applications in both power generation, and traditional heating/air conditioning and refrigeration applications. One such exemplary would be a turboexpander capable of having a virtually unlimited number of start/stop cycles through the use of either an electrostatic or electromagnetic method to switch between modes of attracting or repelling an lubricant, and more preferably a lubricant capable of partially absorbing the thermodynamic cycle working fluid.
The term “algorithm” refers to calculations, rules, and parameter values utilized to determine the change of state in a deterministic manner.
The term “hydraulic” energy refers to the utilization of a pressurized fluid, which is generally incompressible, to store and/or transmit power.
The term “thermal hydraulic” fluid refers to the utilization of a pressurized fluid, which generally has increasing pressure at increasing temperatures. A thermal hydraulic fluid is a compressible fluid, with one exemplary being supercritical CO2. Another example is a binary fluid whereby CO2 is absorbed into the absorbent.
The term “supercritical” is defined as the point at which fluids have been exploited above their critical temperatures and pressures.
The term “expanded fluid” refers to a binary composition comprised of a gas, such as carbon dioxide, and a solvent or absorbent in which the gas is respectively dissolved or absorbed that has an increasing volume for increasing temperatures at a specified pressure. The term “ionic liquids” “ILs” is defined as liquids that are highly solvating, non-coordinating medium in which a variety of organic and inorganic solutes are able to dissolve. They are effective solvents for a variety of compounds, and their lack of a measurable vapor pressure makes them a desirable substitute for Volatile Organic Compounds (VOCs). Ionic liquids are attractive solvents as they are non-volatile, non-flammable, have a high thermal stability, and are relatively inexpensive to manufacture. The key point about ionic liquids is that they are liquid salts, which means they consist of a salt that exists in the liquid phase and have to be manufactured; they are not simply salts dissolved in liquid. Usually one or both of the ions is particularly large and the cation has a low degree of symmetry. These factors result in ionic liquids having a reduced lattice energy and hence lower melting points. Exemplary ionic liquids include liquid ionic phosphates “LIPs”, polyammonium ionic liquid sulfonamides “PILS”, poly(ionic liquids), or combinations thereof, with the additional distinct advantage of being more tolerant to moisture content (above 2%).
The term “poly(ionic) liquid” refers to polymer of ionic liquid monomers.
The term “thermodynamic cycle” is defined as a process in which a working fluid undergoes a series of state changes and finally returns to its initial state, in which the state changes are within a low pressure first state relative to a second high pressure state. The high pressure state is upstream of either an expansion valve or expander device, and the low pressure state is upstream to a compressor or pump. The low pressure first state is at a temperature that is lower than the high pressure second state. Any reference to high pressure is understood as being at a higher pressure of a high side state point relative in the context of a thermodynamic cycle to a low side state point.
The term “separation device” is a device that separates at least one component from another using methods known in the art including filtration, electrostatic attraction or repulsion, or electromagnetic attraction or repulsion.
The term “thermodynamic device” is a device having moving parts within a system having a thermodynamic cycle. Such devices include pump, compressor, turbine, turboexpander, positive displacement pumps and motors, piston pumps and motors, where the thermodynamic device either increases the pressure of the thermodynamic working fluid or extracts mechanical energy from the thermodynamic working fluid.
The term “thermodynamic system” is a system that operates a thermodynamic cycle and has at least one thermodynamic device, and at least one heat exchanger for the addition of thermal energy, and at least one heat exchanger for the removal of thermal energy.
The term “friction reducing device” is a device operable to reduce the friction between moving parts as known in the art to include gas bearings, magnetic bearings, journal bearings, etc.
The term “partially desorb” refers to a minimum of 5% on a weight basis of the total weight absorbed or solubilized thermodynamic working fluid from the solvent or absorbent.
The term “electrorheological” is in the context of an electrorheological fluid where the fluid's viscosity changes when subjected to an electrical field.
The term “dry running friction” is the friction between moving parts when the moving parts are operating without any lubricant.
The term “operating speed” is the actual operational speed for the thermodynamic within the device specifications, and more particularly the upper limit of the speed specification.
The term “moving surfaces” is at least two surfaces that have physical contact with each other and that move in relation to each other. The movement between each other can include rotational or sliding between the at least two surfaces.
Various embodiments of the present invention relate to energy generation, and more particularly to power generation employing dynamic switching to an array of energy storage devices having unique prioritization and energy demand profiles.
Additional embodiments may further include the means to utilize byproduct waste heat in a manner that enables the asynchronous utilization and production of the primary energy form and thermal energy.
Additional features and advantages of the various embodiments are described herein and will be apparent from the detailed description of the presently preferred embodiments. It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
A high efficiency and long operating lifetime, thermodynamic cycle device is provided. The process uses the combination of a primary working fluid with at least a partially immiscible lubricant having either electrically conductive or magnetic properties with a method of controlling the attraction or repelling of the lubricant from the surface of a moving part within the thermodynamic cycle device. The further incorporation of a control system increases the energy efficiency and operating lifetime, especially in thermodynamic cycles having high frequency start/stop operations, as it creates a substantial amount of friction and wear on moving/rotating parts within the thermodynamic cycle devices including compressors, pumps, and expanders.
One aspect of various embodiments is to dynamically vary between two modes of operating, which are lubricant attraction and repulsion, as a means of increasing energy efficiency and reducing friction.
Another aspect of various embodiments is to utilize the immiscible lubricant having either electrically conductive or magnetic properties in combination with a nanofiltration membrane to seal and prevent the flow of a thermodynamic cycle working fluid passed the nanofiltration membrane.
Friction from moving parts present opportunities and challenges that are distinct for most thermodynamic cycle energy consumers and energy producers. The first and most important distinction is compatibility of the thermodynamic cycle working fluid with the lubricant of choice. The second is adverse impact that a lubricant has on heat transfer within the thermodynamic cycle heat exchangers due to the lubricant creating a barrier film within the heat exchangers therefore reducing the heat exchanger effectiveness. Another challenge for lubricants is the operating conditions particularly within an energy producer cycle where the combination of high temperatures and the presence of supercritical working fluids such as carbon dioxide solubilize the lubricant which prevents the lubricant from forming a hydrodynamic film, which renders the lubricant virtually worthless. The selection of superior lubricants, and the ability to precisely control the lubricant attraction or repulsion reduces the associated energy inefficiencies thus contributing to lower emissions, operating costs, and maintenance costs. These benefits further reduce the hurdles particularly for turbines or turboexpanders that are now limited to relatively few start/stop cycles, which leads to more opportunities for distributed generation, hybrid vehicles, and high efficiency HVAC/R.
One embodiment of the electrostatic or electromagnetic lubricant invention provides for the integration of a polarity switching mechanism and control system to optimize the performance of a thermodynamic cycle for high efficiency and long operating lifetimes.
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Further, reference numeral 114 indicates an electrostatic field applying electrode portion which is provided in the lubricant charge accumulator 103 of the lubricant charge accumulator 101, reference numeral 115 indicates a counter electrode portion which is a electrically conductive component of at the rotating roller 107, and reference numeral 116 indicates a bias power supply portion for applying a negative voltage to the counter electrode portion 115. Reference numeral 117 indicates a voltage power supply portion for supplying a voltage to the electrostatic field applying electrode portion 114, and reference numeral 118 indicates a ground portion.
Here, between the electrostatic field applying electrode portion 114 and the counter electrode portion 115, the negative voltage applied from the bias power supply portion 116 to the counter electrode portion 115 and a voltage of from the power supply portion 117 are superimposed. In this way, a superimposed electric field is generated. The ejection of the lubricant 102 ejected from the nozzle hole 104 is controlled by means of the superimposed electric field. In addition, reference numeral 119 indicates a projected meniscus that is formed at the nozzle hole 104 by the bias voltage applied to the counter electrode portion 115. The rotating roller 107 is representative of a moving surface of a compressor, pump, or expander.
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One exemplary of the invention is a thermodynamic system comprising a thermodynamic device having at least one moving surface, a lubricant, a thermodynamic working fluid, where the thermodynamic device includes an expansion device (i.e., expander), and pumping (e.g., positive displacement pump) or compressing device (i.e., compressor). The lubricant reduces the friction between moving surfaces by creating hydrostatic and/or hydrodynamic forces through the utilization of the thermodynamic working fluid. The thermodynamic working fluid's temperature, which makes the working fluid an expanded liquid, increases from friction between the moving surface(s). The preferred lubricant is at least partially immiscible with the thermodynamic working fluid and reduces the friction between the moving surface(s) by at least 5 percent of the friction when not using an expanded liquid. An embodiment of the invention achieves a reduction of friction between the moving surfaces of at least 15%, and in the particularly preferred embodiment of virtually eliminating friction between the moving surfaces through the effective creation of a hydrostatic “bearing” where the expanded working fluid's volumetric increase becomes an air cushion.
The particularly preferred thermodynamic working fluid is a binary solution having an absorbate and absorbent where the preferred lubricant absorbs the absorbate at a first pressure P1, a first temperature T1, and a first density D1. The increase in temperature due to the friction of the moving parts increases the lubricant temperature to a second temperature T2 and has a second pressure P2 and second density D2 at which point the lubricant desorbs at least 5 weight percent of the absorbate being the desorbed absorbate. The particularly preferred thermodynamic working fluid absorbent and/or lubricant are both selected from the group consisting of ionic liquids, liquid ionic phosphates, polyammonium ionic liquid sulfonamides, and poly(ionic liquids). It is furthermore preferred that the lubricant is comprised of at least one component identical to the thermodynamic working fluid absorbent. The lubricant will absorb at least 1% by weight of the thermodynamic working fluid in order to create a volumetric expansion at the second temperature T2 in order to further reduce the friction between the moving parts.
It is recognized in the art that lubricants have adverse impact on heat transfer thus the desire to reduce the lubricant content from the thermodynamic working fluid as known in the art using oil separators. The thermodynamic device of the invention also has a separation device, with the at least two heat exchangers (e.g., evaporator, condenser, regenerator) in order to isolate at least 90 percent of the lubricant from the thermodynamic working fluid. The significant reduction of the lubricant from the thermodynamic working fluid enables an increase in heat transfer by at least 5 percent of the at least two heat exchangers. The preferred lubricant has the ability to control the hydrodynamic film thickness by using a lubricant that is electrically conductive. The current art of lubricants is recognized as including the use of additives within either/both the thermodynamic working fluid or lubricant to enhance corrosion protection, increase thermal conductivity (e.g., nanoscale additives), increase electrical conductivity (e.g., nanoscale additives, and potassium salts). The particularly preferred lubricant has the ability to absorb the thermodynamic working fluid at a relatively lower temperature, which then subsequently desorbs at least 0.5% by weight of the thermodynamic working fluid being the desorbed absorbate. One exemplary lubricant is a functionalized lubricant to increase the gas absorption ability to at least 1% on a weight basis such as an ionic liquid containing increased fluoroalkyl chains on either the cation or anion to improve carbon dioxide solubility as compared to less fluorinated ionic liquids. It is recognized in the art that at least one desorption method including electrostatic desorption, electromagnetic desorption, or thermal desorption can be utilized. The specifically preferred lubricant concurrently desorbs at least 0.5% by weight of the thermodynamic working fluid from the lubricant by electrostatic desorption or electromagnetic desorption, and increases the hydrodynamic film thickness by at least 5% through the lubricants electrostatic/electromagnetic attraction to the moving surface. The lubricant operating conditions and molecular composition are selected such that the desorbed absorbate volumetrically expands by at least 3 percent, with a nominal 15 Kelvin temperature change, as a result of the lubricant's temperature rise leading to at least a 10 percent friction reduction as compared to a lubricant not having the ability to absorb then desorb the thermodynamic working fluid (i.e., the desorbed gas is the refrigerant of the thermodynamic system). One such operating condition is where the desorbed absorbate expands to a second density D2 at a second operating pressure P2 (where the pressure P2 is at least 10 psi higher than the first operating pressure P1). The lubricant expansion leads a localized seal to subsequently reduce leak paths and therefore increase isentropic efficiency of the thermodynamic device.
As noted earlier, the presence of the lubricant has an adverse impact on heat transfer, the control system will further regulate a first electrostatic device operable to attract the lubricant to at least one moving surface of the thermodynamic device and a second electrostatic device operable to isolate the lubricant from the thermodynamic working fluid after lubricating the thermodynamic device moving surfaces such that the lubricant is predominantly present during start/stop operations particularly when used with hydraulic motors such as positive displacement motors, radial thermodynamic devices selected from power producing devices such as turbines, turboexpanders, and ramjets, or power consuming devices including air compressors, vacuum pumps, fuel pumps, fluid pumps, hydraulic pumps, and positive displacement pumps. An exemplary second electrostatic device is an electrostatic filter, an electrode, or an electrostatic membrane. And an exemplary first electrostatic device is an electrode, a porous electrode or an electrostatic membrane.
Another embodiment of the invention is the use of the high pressure thermodynamic working fluid and a control system controlling a high pressure valve to regulate the passage of the high pressure thermodynamic working fluid into the thermodynamic device's moving surfaces to create a hydrostatic force. Of particular importance is the utilization of the high pressure fluid to create a hydrostatic force prior to the thermodynamic device's achieving sufficient speed to utilize hydrostatic air bearings/air foils as known in the art. The release of the thermodynamic working fluid from the thermodynamic working fluid high pressure accumulator creates a hydrostatic force, thus operating as a hydrostatic bearing to reduce by at least 50% the dry running friction between moving surfaces of the thermodynamic device. The preferred control system utilizes a variable position high pressure valve to dynamically regulate the working fluid flow such that the combination of the hydrostatic force from the fluid and the real-time speed of the thermodynamic device creating a second hydrostatic force from the hydrostatic air bearing/air foil is precisely the force required to prevent direct contact of the moving surfaces. One exemplary operating mode is where the thermodynamic working fluid high pressure accumulator provides mass flow prior to equilibrium operation to create a hydrostatic force on the hydrostatic bearing until the thermodynamic device is operating at sufficient speed to reduce by at least 10%, with typically at least 50%, and optimally virtually eliminating the dry running friction between moving surfaces. The invention anticipates the utilization of a magnetic bearing as known in the art in replacement of the air bearings/air foil, where air and gas are interchangeable.
Another embodiment of the invention is the combination of the particularly preferred lubricant, which is electrically conductive, and a membrane that is preferably a nanofiltration membrane. The specifically preferred nanofiltration membrane has a pore size that is at least 5% smaller than the lubricant molecular size, and at least 5% greater than the thermodynamic working fluid molecular size. Alternatively, the membrane can have a pore size that is larger than the working fluid molecular size and has a thickness that is at least 10 times the molecular size of the working fluid, thus creating a tortuous path to limit the flow of the thermodynamic working fluid. The membrane contains the lubricant that when configured within a pipe is controlled to limit and/or prevent the flow of the thermodynamic working fluid. The configuration is effectively a valve, which when configured with a controllable electrostatic or electromagnetic field limits the flow thermodynamic working fluid through the membrane. The control system switches the electrostatic device to attract and or repel the lubricant. The configuration within the valve determines whether the electrostatic film blocks the flow of working fluid, or opens the passage to enable flow of working fluid. The control system varies the electrostatic device operating voltage to dynamically vary the thermodynamic working fluid flow rate through the valve.
Another embodiment of the invention is the utilization of the strong solution, from within an absorption heat pump system to reduce the friction created from moving surfaces of the pump, through the pump where it concurrently increases the enthalpy of the strong solution due to the thermal energy from friction within the pump and reduces friction.
Yet another embodiment, is a friction reducing machine having at least one moving surface, a fluid port that is operational as both the fluid inlet and discharge outlet, and a nanofiltration membrane within the fluid port to contain a lubricant. The nanofiltration membrane contains the lubricant within the cell/cavity of the machine by minimizing the discharge of the lubricant by selectively enabling a working fluid having a smaller molecular weight to discharge from the machine. A preferred configuration utilizes an electrostatic field to increase the hydrodynamic film within the machine further reducing the friction. A preferred machine includes gerotor motor, gerotor pump, vane motor, vane pump, piston motor, and piston pump, which can be operational as hydraulic pumps/motors or equally well using a fluid medium selected from water, air, fuel, refrigerants, etc. It is anticipated that the configuration further comprising the mass flow sensor and power sensor is also utilized in the aforementioned machine by utilizing a control system having a machine performance table. The control system has a performance table that is ideally represented as known in the art by a multi-parametric non-linear equation that is a function of input temperature, input pressure, outlet temperature, outlet pressure, and mass flow. The machine's real-time performance is compared to the predicted power output from the multi-parametric equation to predict scheduled maintenance requirements. The particularly preferred machine is manufactured of at least one part that has the moving surface such that the part is able to wear into its final size in order to minimize leak paths between the moving surfaces. It is recognized in the art that the part can be made of a soft metal, ceramic, or carbon/graphite where the part is machined to a size that is at least 0.0005 inches larger than final part size.
The invention has been described with reference to the various preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
