Patent Application
20170145930
The present invention relates generally to an apparatus and a method for regulating fluid pressures. More particularly, the invention relates to an apparatus and method for regulating fluid pressures in a fluid system which uses two distinct fluids, either alternatively or simultaneously. The fluid regulator of the present invention may be applied to a variety of fluid systems, such as dual fuel engines, plant watering systems and so forth.
With ever increasing raw oil prices and more and more stringent emission regulations, the use of alternative fuels, such as gaseous fuels, for operating combustion engines has become increasingly attractively. Most commonly, such alternative gaseous fuels are compressed natural gas (CNG) and liquified petroleum gas (LPG), which exhibit a higher specific calorific value compared to traditional fuel sources, and thus cause less air pollution.
An increasing number of customers are specifically requesting dual fuel systems, capable to run on conventional fuels and, additionally, on fuels, such as CNG and LPG. Dual fuel engines are well known in the art and combust a mixture of conventional liquid fuels, such as diesel fuel, and gaseous fuels such as LPG or CNG. By combusting two different types of fuel, the advantages of both fuels can be realised. In dual fuel engines, the pressures and/or flow rates of the two different kinds of fuel need to be controlled accurately to ensure correct performance of the engine. In particular, when combining diesel fuel with a gaseous alternative fuel, the diesel fuel is used for the ignition of the gas/air mixture inside the combustion cylinder. Historically, the liquid fuel and the gaseous fuel have been fed into a combustion cylinder independently, for example via separate liquid fuel pumps and pressurised gas reservoirs. It is a known problem of the conventional system that linking of the pressures and/or flow rate of the two fuels requires complicated control systems, which are prone to failure and high in cost, due to their complexity.
Due to the above, it is an object of the present invention to provide a method and a device for regulating fluid pressures, particularly for but not limited to dual fuel engines, which comprises a simple, more cost efficient construction. Additionally, it is an object to provide a method and apparatus that is more reliable and durable than the commonly known fluid pressure regulators.
The present invention solves the aforementioned objectives by means of a fluid pressure regulator according to claim 1 and a method for regulating fluid pressure according to claim 18.
In a first embodiment of the present invention, a fluid pressure regulator is provided with a housing and a cavity extending between a first end surface and a second end surface of the housing. A divider is arranged within the housing and configured to divide the cavity into a first chamber, extending between the divider and the first end surface, for receiving a first pressurised fluid and a second chamber, extending between the divider and the second end surface, for receiving a second pressurised fuel. The fluid pressure regulator further comprises a liquid fluid inlet connected to the first chamber and adapted for introduction of a liquid fluid into the first chamber, and a gaseous fluid inlet connected to the second chamber and adapted for reduction of a gaseous fluid into the second chamber. A sensor device is provided and configured to monitor the position of the divider within the cavity of the housing.
According to the present invention, the fluid pressure regulator comprises two chambers for introduction of two different kinds of fluid, the chambers being divided by a divider, which is freely moveable within the cavity of the housing. By virtue of this arrangement, the non-compressible first fluid, that is the liquid fluid, can be subjected to a pressure, which is dependent on the pressure of the second, compressible fluid, that is the gaseous fluid. In more detail, if the liquid fluid and the gaseous fluid act on the same surface area of the divider, then the pressure of the liquid fluid within the first chamber will be equal to the pressure of the gaseous fluid in the second chamber, which relates to a pressure ratio 1:1. As will be described in more detail below, this ratio can easily be amended, should this be necessary for the purpose of the pressure regulator. By monitoring the position of the divider within the housing, it is possible to determine at least the flow rate of the liquid fuel through the system, at any point in time.
The fluid pressure regulator of the present invention might be a fuel pressure regulator for regulating the gaseous and liquid fuel pressures of a dual fuel engine. In this regard, the liquid fuel might be diesel, while the gaseous fuel might be natural gas.
In another aspect of the present invention, the divider is moveable between the first end surface and the second end surface of the housing. If the divider moves towards the first end of the housing, the volume of the first chamber will reduce, whilst the volume of the second chamber increases and vice-versa. This embodiment represents a particularly simple construction of the housing and divider, which does not require any stops but rather holds the divider freely moveable within a cavity of the housing. Of course, it is also feasible to provide stop surfaces within the cavity of the housing, which restrict the moving space of the divider, thereby assuring minimum volumes for the first and second chamber.
In another embodiment, the fluid pressure regulator comprises a control unit adapted to control introduction of the liquid fluid into the first chamber, via the liquid fluid inlet. The control unit may further be adapted to control introduction of the gaseous fluid into the second chamber, via the gaseous fluid inlet. In a particularly preferred arrangement, the control unit is connected to the sensor device and configured to introduce liquid fluid into the first chamber, depending on the position of the divider within the housing. As the skilled person will understand, the position of the divider within the housing is ultimately determined by the amount of non-compressible liquid fluid within the first chamber. Accordingly, the control unit may be configured to maintain a predetermined volume of liquid fluid within the first chamber, which may in turn depend on the size and type of engine supplied by the fluid regulator.
The control unit may be adapted to control the introduction of the liquid fluid such that the divider remains in a predetermined working range about a predetermined working position. The predetermined working position may be chosen such that the volume of liquid fluid within the first chamber, that is the volume of liquid fluid within the housing, is appropriate for running a respective engine. The predetermined working range may be chosen in such a way that the amount of liquid fluid within the first chamber always exceeds the minimum amount of fluid required for operating the respective engine for a predetermined amount of time. The amount of time may relate to the “control cycle”, i.e. the amount of time it takes a control unit to process the position signals received from the sensor device and supply more pressurized liquid fuel to the first chamber.
According to another embodiment of the present fluid pressure regulator, the working position is set in the centre between the first and second end surfaces of the housing, whereas the working range may extend 1 to 10 millimetres from the working position towards the first end surface and 1 to 10 millimetres from the working position towards the second end surface of the housing. Of course, the working range is not limited to such values. The skilled person would understand that the working range may vary, depending on several factors, such as the size of the chambers, the reaction time of the control unit and the liquid consumption of the fuel system.
In yet another embodiment, the fluid pressure regulator comprises a first inlet pressure gauge to measure the pressure of the gaseous fluid at the gaseous fluid inlet, wherein the control unit is connected to the first inlet pressure gauge and configured to control the supply of gaseous fluid into the second chamber, depending on a predetermined gas pressure value. As will be discussed in more detail below, the pressure at the gaseous fluid inlet is a measure for the pressure of the gaseous fluid within the second chamber of the fluid pressure regulator. Upon consumption of the gaseous fluid during operation of the respective fluid system, the gas pressure within the second chamber will decrease. The decrease in gas pressure is monitored by the first inlet pressure gauge, which in turn is connected to the control unit that is configured to control the supply of new gaseous fluid into the second chamber. The control unit is configured to supply enough gaseous fluid into the second chamber to maintain a predetermined gas pressure value. The predetermined gas pressure value may depend on the size and type of the respective engine. As mentioned previously, the liquid fluid pressure in the first chamber is directly dependent on the gas pressure within the second chamber. Consequently, the control unit functions to control both the gas pressure of the second chamber and the liquid fluid pressure of the first chamber, at the same time. In an alternative embodiment, the supply of gaseous fluid is not directly controlled but monitored by the control unit. In this embodiment, the pressurized gaseous fluid from a gaseous fluid source is supplied to the second chamber constantly via a normally open gaseous fluid inlet. Consequently, the pressure within the second chamber remains equal to the fluid pressure of the gaseous fluid source.
In another embodiment of the present invention, the pressure regulator is constructed in such a way that the liquid fluid pressure is 5 psi to 10 psi (0.345 bar to 0.690 bar) higher than the gaseous fluid pressure in the second chamber. It should be understood that the pressure difference may be significantly higher or lower than this, depending on the specific requirements of the corresponding fluid system. According to one arrangement, the difference in fluid pressure between the first and second chamber may be achieved by biasing the divider towards the first end surface of the housing, that is in the direction of the first chamber. One way of biasing the divider in the direction of the first end of the housing, may be the arrangement of a compression spring within the second chamber, which is adapted to apply its spring force on the divider, in a direction towards the first end surface of the housing. According to this embodiment, the divider comprises a piston, which seals the first chamber from the second chamber. The person skilled in the art would appreciate that placement of the compression spring can be on either side of the divider, therefore providing positive or negative bias pressure between the liquid and the gaseous fluid as required by the application.
Alternatively, it is also feasible to achieve the aforementioned pressure difference by providing a divider with unequal contact surfaces. In particular, the contact surface of the divider facing the second chamber may be constructed bigger than the opposite contact surface facing the first chamber. The person skilled in the art would appreciate that this could be achieved by any conventional means, such as a divider rod, which extends through the first chamber of the housing.
In an alternative embodiment of the present invention the pressure regulator is constructed for zero bias. There is no spring and therefore the gas pressure is equal to the liquid pressure within the housing. A piston and seal may be used as the divider to divide the cavity into two separate chambers.
Alternatively, if the housing is mounted vertically, so that said second chamber is on top of the said first chamber, the liquid fluid will be separated from the gaseous fluid by gravity. According to this embodiment, the divider may comprise a floating gauge. This divider (without a seal) can comprise a liquid fluid barrier and be used to prevent splashing and as a marker for the sensor device.
In another aspect of the present invention, the fluid pressure regulator further comprises a liquid fluid outlet connecting the first chamber with an engine fuel system, and a gaseous fluid outlet connecting the second chamber with an engine fuel system. Accordingly, the liquid fuel and the gaseous fuel remain separate but at a sharply defined ratio, until the two alternative fuels reach the engine fuel system, which will then be used simultaneously or subsequently by the engine.
In another embodiment, the fluid pressure regulator comprises a bypass line, connecting the liquid fuel source directly to the engine fuel system. The operator may choose whether the fuel system of the present invention may be used as a dual fuel system or as a single fuel system. If the operator chooses to run the system as a dual fuel system, the liquid fuel is introduced into the first chamber via the liquid fluid inlet, which may comprise one or more control valves. If, however, the operator would like to run the engine on liquid fuel only, the system may be operated in a “run on liquid fuel” mode, in which the liquid fuel bypasses the fluid pressure regulator and is directly introduced into the engine fuel system via a bypass line. To this end, the bypass line may comprise a bypass valve, which can be controlled by the aforementioned control unit. The control unit may also be configured to automatically choose between the two different modes of operation. In detail, the control unit may choose the “run on liquid fuel” mode for start up, while the temperature of the engine is still too low for use with gaseous fuels. Alternatively, the control unit might use the “run on liquid fuel” mode for diagnostic reasons or if the system has run out of gaseous fuel, or there are any issues with the system (“limp home mode”).
According to another aspect of the present invention, the gaseous fluid outlet is connected to a vent valve, said vent valve being adapted to controllably vent the second chamber of the housing. When the engine is stopped, the fluid pressure regulator is shut down and the pressurised gaseous fluid in the second chamber can be released into a gas reservoir, via the vent valve. Due to the specific construction of the present fluid pressure regulator, it is not required to vent the non-compressible liquid fluid of the first chamber, since the pressure on the liquid fluid will be removed as soon as the gas pressure is released through the vent valve. Consequently, this particular embodiment provides for a quick and simple shut down function.
In another aspect, the liquid fluid is diesel and/or the gaseous fluid is natural gas, preferably compressed natural gas (CNG). Of course, it is equivalently feasible to use petroleum as the liquid fluid and/or LPG as the gaseous fuel.
The present invention further relates to a fuel system comprising a liquid fuel source and a gaseous fuel source, said liquid and gaseous fuel sources being connected to an engine fuel system via the pressure regulator of the present invention.
In another embodiment, the present invention discloses an engine comprising the aforementioned fuel system.
The present invention further relates to a method for regulating fluid pressure comprising the following steps:
In another embodiment, the method further comprises controlling the amount of liquid fluid introduced into the first chamber depending on the position of the divider within the cavity of the housing.
In another aspect, the amount of liquid fluid introduced into the first chamber is controlled such that the divider remains in a predetermined working range about a predetermined working position.
According to another embodiment, the method of the present invention further comprises measuring the pressure of the gaseous fluid at the gaseous fluid inlet of the second chamber, and controlling the supply of gaseous fluid into the second chamber depending on a predetermined gas pressure value.
In another aspect, the method comprises biasing the divider towards a first end surface at the end of the first chamber, preferably by means of a compression spring.
In the following, detailed description of the figures, preferred embodiments of the present invention are explained.
The divider 20 is constructed as a piston, which is in contact with and guided by an interior wall 17 of the housing 10. In order to prevent an inadvertent mixture of the gaseous fluid of the second chamber 12 with the liquid fluid of the first chamber 11, the divider 20 comprises a seal member 23, which is received within an annular recess 25. The divider 20 is freely moveable between the first end surface 13 and the second end surface 14 of the housing 10 as indicated by the two arrows. As will be appreciated by any skilled person, the position of the divider 20 within the housing 10 is determined by the amount of liquid fuel, which is introduced into the first chamber 11 via fluid inlet 51. In particular, due to the non-compressible nature of the liquid fuel, the amount of gaseous fluid within the second chamber 12 is irrelevant for the position of the freely moveable divider 20.
Accordingly, in the first embodiment, the pressure of the liquid fluid within the first chamber 11 is always substantially the same as the pressure of the gaseous fluid within the second chamber 12. The skilled person will understand, that although provision of a gaseous fluid to the engine fuel system via fluid outlet line 62 will decrease the absolute gas pressure within the second chamber 12, the ratio between the gas fluid pressure and the liquid fluid pressure will always remain the same, which is crucial for the correct function of a dual fuel engine. In this particular embodiment, the ratio between the gaseous fluid pressure and the liquid fluid pressure will always remain at about 1:1.
The method of controlling fluid pressure according to the present invention is better understood in view of
P
liquid fluid
=P
spring
+P
gaseous fluid
At the first method step of
During a second method step, shown in
A third embodiment of the fluid pressure regulator of the present invention is shown in
The embodiment of
First and second check valves 93, 94 are provided in the liquid fluid inlet 51 and the gaseous fluid inlet 61 respectively. Each of the check valves 93, 94 is located downstream of the first or second solenoid valve 91, 92. Check valves 93, 94 prevent the fuels from flowing back out of the first and second chamber 11, 12, via the respective fluid inlets 51, 61. In other words, the check valves 93, 94 function as one-way inlet valves of the fluid pressure regulator 1.
As will be described in more detail with reference to
The system of
The second embodiment of the fuel system shown in
For the system of
A third embodiment of the fluid system is shown in
While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood that the invention is not limited thereto since modifications may be made by those skilled in the art without departing from the spirit and scope of the present disclosure, particularly in light of the foregoing teachings.
| Number | Date | Country | |
|---|---|---|---|
| 62259769 | Nov 2015 | US |
