CN101535603A - Cryogenic engines - Google Patents

Abstract

A semi-molten gas is used as the driving fluid for the cryogenic engine, which is a gas or gas mixture cooled to a partially solid and partially liquid state. The cryogenic engine has a working chamber (50) which is connected via an injection device to an energy source comprising a main body of semi-molten gas (47). The injection device has a housing (36) which serves as a heat exchanger to partially boil the semi-molten gas entering the injector, thereby enabling the gas to be driven into the working chamber (15) under pressure.

Description

cryogenic engine

technical field

The present invention relates to cryogenic engines and in particular to drive fluids for cryogenic engines. The term "cryogenic engine" is used to include, but is not limited to, any device that generates mechanical (and/or electrical) power from a cryogenic drive fluid through boiling and expansion. Mechanical power includes output shaft power and propulsion power from jets. Thus, for example, the term engine includes within its scope engines having reciprocating drive members, rotary engines including turbines, and jet or non-chemical rocket engines.

Background technique

PCT specification WO 01/63099 discloses a cryogenic engine using liquefied gas (eg liquefied nitrogen) as the drive fluid. Liquefied nitrogen has a drawback: in the event of a leak into an enclosed space, the resulting atmosphere can suffocate people and other animals. Also, pumping liquefied nitrogen at high pressure is very difficult because of its tendency to vaporize. The present invention is based on the work done to identify alternative drive fluids for cryogenic engines.

Contents of the invention

According to one aspect of the invention, the semi-melted gas is used as a driving fluid in a cryogenic engine. As used herein, the term "semi-molten gas" refers to a gas, or a mixture of gases, that has been cooled or compressed such that it is partially solid and partially liquid.

Semi-melted gas may be semi-melted air, which is air cooled (typically below minus 210 degrees Celsius) so that it is partially solid and partially liquid.

The drive fluid may be supplied to the engine as semi-melted gas. In another example of the present invention, the driving fluid is a liquid obtained from a semi-melted gas by first melting solid components in the semi-melted gas, whereby said semi-melted gas constitutes the source of the driving fluid.

The semi-melted gas is pretreated by removing one or more constituents of the air prior to solidification. It is especially desirable to remove moisture (ie, water vapor) from the air by using known cryogenic drying processes, according to which air is cooled to condense water vapor which is then vented. Additionally, or alternatively, carbon dioxide may be removed during compression or chemical absorption by, for example, physical separation, both processes known per se.

Semi-molten air is easier and cheaper to produce than liquid nitrogen, and semi-molten air contains more energy than liquid nitrogen. Semi-molten air has an energy density of 1.5 to 1.6 MJ/kg compared to 1.23 for liquid air and 1.1 for liquid nitrogen. Also, semi-melted air is safer and easier to transport because any increase in temperature will first cause the solid components to melt rather than the liquid components to boil, resulting in less pressure build-up and less overall waste. Also, any semi-melted air that boils off results in harmless emissions.

The liquid-to-solid ratio of the semi-melted air can vary, but the semi-melted air must be sufficiently flowable (or fluid) to be injected into a cylinder or other working chamber of a cryogenic engine. The preferred ratio of liquid:solid is in the range of 70:30, most preferably 60:40.

Instead of forming the semi-molten gas by cooling air, the semi-molten gas can be formed by cooling the individual gas components (eg, nitrogen and oxygen) and then combining the cooled components to form the semi-molten gas.

Alternatively, the semi-molten gas may be semi-molten nitrogen, which is nitrogen cooled so that it is partially solid and partially liquid.

According to another aspect of the invention, a cryogenic engine is made utilizing semi-melted gas as its driving fluid.

The cryogenic engine, to which the semi-melted gas is delivered, can be used to power a vehicle (eg, a motor road vehicle) or a stationary engine (eg, to generate electricity).

Injection means are preferably used to deliver semi-melted gas under pressure to engine cylinders or other working chambers where the drive fluid (consisting of semi-melted gas) expands to provide shaft power.

The present invention also includes within its scope a method of generating shaft power using semi-melted gas as an energy source, preferably semi-melted air.

The injection device preferably comprises a housing, and an injection member movable in the housing to displace the driving fluid from a first region of the housing to a second region of the housing, in use, the driving fluid being in a semi-molten state is introduced into the housing The first area of the body and through the movement of the injection member is transferred to the second area, the second area is at a higher temperature than the first area, so that the small volume of driving fluid in the second area boils and the driving fluid is then injected under pressure into a cold engine.

The injection member preferably moves within the housing in a repeating sequence timed to be properly synchronized with the low temperature engine duty cycle, which coincides with a two-stroke or four-stroke cycle. The injection device is driven by a low temperature engine or alternatively by a separate power source, such as an electric motor. At start-up, the device cools the semi-melted gas by filling it through the first zone.

The spray member is preferably reciprocable within the housing, undergoing spray strokes and return strokes in an alternating sequence. During the injection stroke, the member moves toward the second region, carrying a volume of drive fluid, and in this case the member is in sealing engagement with the housing and has a groove into which the volume of drive fluid is introduced at the first region and which at the second Two regions are transmitted from it.

Alternatively, the injection member moves towards the first area during the injection stroke, displacing the drive fluid from the first area to the second area, and in this case the housing is preferably equipped with inlet and outlet valves, inlet and outlet valves Opening and closing are timed to introduce drive fluid into the first region at the start of the spray stroke and allow drive fluid to be withdrawn before the return stroke begins.

The injection device consumes little power conveniently derived from the shaft power of the associated cryogenic engine.

The present invention includes within its scope a body of semi-molten gas suitable for use as a drive fluid (or source thereof) as an energy source for a cryogenic engine.

The body of semi-molten gas is maintained in a container, preferably insulated, at atmospheric pressure or above. The container is the fuel tank of a cryogenic engine, which may be a stationary engine or may power a vehicle such as a motor road vehicle; or the container may be a storage tank (stationary or mobile) for refueling the cryogenic engine. This semi-melted gas body can be regarded as an energy storage battery, which has the advantages of easy availability of component gases, high energy density, storage capacity for extended time periods, easy transportation and no pollution during use.

In the case of fuel tanks for small vehicles, such as scooters, golf carts, mopeds, motorcycles, or lawn mowers, or small household generators, the container has a capacity of up to 100 liters ( also corresponds to the volume of the semi-melted gas body therein). The container for the fuel tank of a motor vehicle has a capacity of at least 100 liters, preferably 250-300 liters, with a corresponding initial volume of the body of semi-melted gas. If the body of semi-melted gas is used to propel the bus, the initial volume of the body and the capacity of its container are preferably at least 1000 liters.

Semi-melted gas bodies can be used as devices for storing energy derived from off-peak power generated by power plants such as nuclear power plants, in which case the body volume is on the order of millions of liters and can be stored in large underwater or in an underground storage box.

Description of drawings

Four embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figures 1 to 3 illustrate a first embodiment at three different stages in the operating cycle,

Figures 4 to 7 illustrate a second embodiment at four different stages in the operating cycle,

Figure 8 illustrates a third embodiment combined with part of a cryogenic engine,

Fig. 9 is a sectional view on line IX-IX of Fig. 8, and

Figures 10 and 11 correspond to Figures 8 and 9, but show a fourth embodiment.

Two examples of injection devices for injecting semi-melted air into cryogenic engines will now be described exemplarily with reference to the accompanying drawings, in which:

Detailed ways

Each example of the injection means is designed to inject a charge of semi-melted air into the working chamber of a cryogenic engine, preferably a cryogenic engine as disclosed in PCT specification WO 01/63099, the disclosure of which is incorporated by reference. Semi-melted air is a mixture of liquefied and solidified air in a 60:40 liquid-to-solid ratio so that the mixture is fluid enough to spray. In the working chamber of the engine, semi-melted air receives energy from the heat exchange fluid and expands to generate engine shaft power.

The spraying device of Figures 1 to 3 comprises a spraying member in the form of a plunger 4 reciprocating in a cylindrical housing 6 and in sealing engagement therewith. The housing 6 has a first zone 8 (at a temperature low enough for semi-melted air) and a second zone 10 at ambient temperature, typically between 10°C and 20°C. The wall of the housing has an increased diameter portion forming an annular inlet chamber, and the plunger has a reduced diameter portion forming a waist-shaped region defining an annular volume.

The plunger 4 undergoes alternating injection and return strokes to draw semi-melted air 2 at low pressure from its source and deliver it under pressure to the working chamber of the cryogenic engine.

To this end, a source of low-pressure semi-melted air is provided in communication with the annular inlet chamber. At the beginning of the injection stroke ( FIG. 1 ), the annular inlet chamber communicates with the waist region in the plunger, so that the annular volume is filled with semi-melted air 2 at low pressure. The plunger 4 then moves down in the housing 6 to undergo the injection stroke (FIG. 2), the plunger sealingly engages the housing wall so that the volume of semi-melted air 2 in the chamber travels with the plunger 4 from region 8 to Region 10 carries. Once zone 10 is reached, the small volume of delivered semi-melted air boils as it experiences higher temperatures in zone 10, creating a source of high pressure which, at the end of the injection stroke when the chamber is no longer covered by the shell walls, boils A dose of semi-melted air is driven into the chamber of the cryogenic engine (Figure 3).

Referring to Figures 4 to 7, a second embodiment of the injection device includes a plunger 20 reciprocable with clearance in a cylindrical housing 22, with an inlet valve 24 to control the introduction of low pressure semi-melted air from a semi-melted air source , and outlet valve 26 to control the flow of high pressure semi-melted air from housing 22 to the working chamber of the cryogenic engine. Valve 26 has a valve stem 30 that passes through a passage in plunger 20 .

At the beginning of the injection stroke (FIG. 4), the inlet valve 24 is opened and the outlet valve 26 is closed, and low pressure semi-melted air enters the first region 32 of the housing which is at a low temperature. The inlet valve 24 is then closed and the plunger 20 begins the injection stroke, moving upwards in the housing 22 towards the low temperature region 32 (Fig. 5). During the injection stroke of the plunger 20, the semi-melted air is transferred by moving from the low temperature region 32 to the second region 34 which is at ambient temperature. At the end of the injection stroke ( FIG. 6 ), substantially all the semi-melted air has been delivered and due to the higher temperature in region 34 a small volume of nitrogen boils. The resulting high pressure opens the outlet valve 26 and causes semi-melted air to be injected at high pressure into the working chamber of the cryogenic engine.

In each embodiment, the flow of semi-melted air through the device will maintain the desired low temperature in the first (low temperature) region. The second (higher temperature) zone is maintained at the desired higher temperature by absorbing heat from the cylinders or housing of the cold engine, or by contact with the heat exchange fluid. The device is driven by the low temperature engine (for example, from its camshaft), or may be driven from a separate electric motor. The amount of semi-melted air entering the device can be controlled (eg, by a valve, or by controlling the pump speed in relation to the cryogenic engine).

The injection device shown in Figures 8 and 9 has a generally cylindrical housing 36 from which extends an array of 12 heat exchange tubes 38 through which a heat exchange liquid 40, such as glycol, passes. At the inlet area of the housing, an inlet valve 42 controls the introduction of semi-melted air 44, which is supplied to the injection device through a supply pipe 46, which is adiabatically pressurized to maintain the semi-melted air supply at about minus 220 °C The storage box 47 communicates. The box is shown schematically and on a reduced scale for clarity. In the outlet area of the housing, where outlet valve 48 controls the delivery of semi-melted air under pressure to cylinder 50 of the two-stroke cryogenic engine, there is a piston 52 reciprocable in cylinder 50 .

The inlet valve 42 is formed by a movable valve member having an elongated stem 54 terminating at its lower end in a valve head 56 cooperating with a valve seat 58 on the lower end of a cylindrical guide 60 . The valve member stem 54 slides within the guide 60 and is sealed against the inner surface of the guide 60 by a circumferential seal 62 . The supply pipe 46 communicates with the lower end of the guide 60 just above the valve seat.

Similarly, the outlet valve 48 has a movable valve member with an elongated stem 64 terminating at its lower end in a valve head 66 cooperating with a valve seat 68 on the lower end of a cylindrical guide 70 . The valve member stem 64 slides in the guide 70 and is sealed against the inner surface of the guide 70 by a circumferential seal 72 .

Just above the valve seat 68 , an outlet tube 74 communicates with the lower end of the guide 70 , opening into the upper end of the cylinder 50 . The upper end of the cylinder 50 has two valves, a valve 76 for introducing the heat exchange liquid 40 into the cylinder 50 and a valve 78 for discharging the heat exchange liquid and the drive fluid through a discharge pipe 80 . The cryogenic engine is a two-stroke engine and functions in the manner disclosed in WO 01/63099. The injection device and cryogenic engine of Figures 8 and 9 operate in the following manner.

From piston 52 at top dead center (as shown in FIG. 8 ), inlet valve 42 is closed, outlet valve 48 is opened, and both valves 76 and 78 are closed. A charge of drive fluid (i.e., semi-melted air) is forced from housing 36 through open outlet valve 48 and into cylinder 50, where the drive fluid expands (while absorbing heat from the heat exchange liquid in cylinder 50), causing piston 52 to experience The power stroke to drive the crankshaft of the engine. Near the end of the power stroke, as piston 52 approaches bottom dead center, discharge valve 78 opens and outlet valve 48 remains open until piston 52 is just above bottom dead center to reduce pressure in the housing when the outlet valve closes. During the return stroke of the piston 52, the outlet valve 48 is closed, after which the inlet valve 42 is opened as quickly as possible. This causes a charge of drive fluid to be introduced into the space surrounding the tube in housing 36 . Heat exchange fluid 40 passing through tube 38 transfers thermal energy to the drive fluid causing a small amount of drive fluid to boil thereby increasing the pressure in the housing so that when outlet valve 48 opens at the start of the next power stroke the drive fluid is under pressure injected into the cylinder. During the return stroke of piston 52 , valve 76 opens to direct heat exchange fluid to cylinder 50 .

The valve timing described above requires the inlet valve 42 and outlet valve 48 to go through operating cycles at the same speed as a low temperature engine. This places considerable demands on the inlet valve 42, and in order to meet this problem, the injection device can be duplicated (or repeated any number of times). For example, a pair of injection devices, each as shown in Figures 8 and 9, could be arranged side by side to feed a single cryogenic engine, with each of the two devices operating at half the speed that would be required if the engine were fed by a single device.

The heat exchange fluid supplied to housing 36 is the same fluid supplied to cylinder 50 through inlet valve 76 . The liquid supplied to the housing 36 is preferably taken from the main heat exchange liquid supplied to the cylinders through a branch connection, the liquid flowing from the housing 36 being supplied back to the return of the heat exchange liquid after having been drained from the cylinders 50 . The inlet and outlet valve guides 60 and 70 and stems 54 and 64 are elongated so that the seals 52, 72 can be positioned away from the cryogenic regions at the lower ends of these valves.

In the spraying device of Figs. 10 and 11, the same parts corresponding to the parts of Figs. 8 and 9 have the same reference numerals. Figures 10 and 11 differ in that: the way the supply tube 46 continues through the guide 60; on the lower end of the guide 60, the increased spacing of the junction between the tube 46 and the guide 60; and the inlet valve member is formed as A spring loaded check valve member 84 biased towards its closed position, wherein the check valve member 84 engages the lower end of the pilot 60 . Inlet valve 42 is opened by downward movement of stem 54, which not only traps a volume of drive fluid in the lower length of guide 60, but also causes check valve member 84 to open, thereby forcing that volume of drive fluid into the housing 36 in.

The supply pipe 46 continues beyond the guide 60, directing the semi-melted air back into the storage tank under the influence of a small recirculation pump preferably located in the storage tank. This slow cycle reduces the tendency to form air bubbles in the semi-melted air.

After entering the housing 36 the semi-melted air receives heat from the heat exchanger causing a small portion to boil, driving the semi-melted air through the outlet valve 48 and into the cylinder 50 in the manner described with respect to FIGS. 8 and 9 .

Claims (33)

1. Use of semi-melted gas as a driving fluid, or a source of driving fluid, in a cryogenic engine. 2. The use of semi-melted gas according to claim 1, characterized in that the semi-melted gas is semi-melted air. 3. Use of semi-melted air according to claim 2, characterized in that said semi-melted air is pretreated by removing one or more constituents of the air before its liquefaction and partial solidification. 4. Use of semi-melted air according to claim 3, characterized in that the components removed are water vapor and carbon dioxide. 5. Use of semi-melted gas according to any one of the preceding claims, characterized in that the liquid-solid ratio in the semi-melted gas is in the range of 70:30. 6. The use of semi-melted gas according to claim 5, characterized in that the ratio is in the range of 60:40. 7. A method of operating a cryogenic engine, said method comprising the step of supplying a cryogenic drive fluid comprising or derived from semi-melted gas to the engine. 8. The method of claim 7, wherein the semi-melted gas is injected directly into the working chamber of the engine. 9. The method of claim 8, wherein said injecting is accomplished by introducing a charge of drive fluid into the inlet region of the injector housing via an inlet valve, closing said inlet valve, Heat is transferred to the fluid towards the exit region of the housing, causing a small volume of drive fluid to boil and thereby inject the fluid under pressure to the engine. 10. The method of claim 8, wherein the fluid is injected into the engine through an outlet valve of an injector. 11. The method of claim 10, further comprising operating the valves in a timed relationship such that when the inlet valve opens to introduce a charge of drive fluid, the outlet valve closes, after which the inlet valve closes and the shell The pressure of the driving fluid in the body increases and the outlet valve opens to deliver the driving fluid under pressure. 12. A method according to any one of claims 8-11, characterized in that the cryogenic engine to which the semi-melted gas is delivered is a stationary engine for powering a vehicle. 13. Cryogenic engines employing semi-melted gas as drive fluid, said engine having injection means to deliver semi-melted gas under pressure to engine cylinders or other working chambers where the drive fluid expands to provide shaft power generated by the engine. 14. The engine of claim 13, wherein the injection device comprises a housing, an inlet valve for controlling the introduction of drive fluid into the inlet area of the housing, and a valve for controlling the delivery of drive fluid from the outlet area of the housing. an outlet valve, the housing being arranged such that heat is transferred to the drive fluid as it passes from the inlet region to the outlet region such that a small volume of drive fluid in the housing boils and thereby injects the drive fluid through the outlet valve and under pressure into a cold engine. 15. The engine of claim 14, wherein the inlet valve and the outlet valve operate in a timed relationship such that when the inlet valve is opened to introduce a charge of drive fluid, the outlet valve is closed, at which point The inlet valve is then closed, the pressure of the drive fluid in the housing is increased and the outlet valve is opened to deliver the drive fluid under pressure. 16. An engine as claimed in claim 14 or 15, wherein the housing is formed as a heat exchanger for passing a heat exchange liquid to transfer heat from the heat exchange liquid to the drive fluid. 17. The engine of claim 16, wherein the heat exchanger is formed by a plurality of tubes extending through the casing and the heat exchange liquid passes through the tubes. 18. The engine of claim 17, wherein the tube extends from an inlet region to an outlet region of the housing, the drive fluid occupying a space within the housing and surrounding the tube. 19. The engine of claim 13, wherein the injection device includes a housing, and an injection member movable within the housing to displace drive fluid from a first area of the housing to a second area of the housing , in use, the driving fluid in the liquefied state is introduced into the first area of the housing and transferred to the second area by the movement of the injection member, the second area is at a higher temperature than the first area, so that the small volume in the second area drives The fluid is boiled and the drive fluid is then injected under pressure into the cryogenic engine. 20. The engine of claim 19, wherein the injection member moves within the housing in a repeating sequence timed to be properly synchronized with the low temperature engine working cycle corresponding to a two-stroke or four-stroke cycle. 21. The engine of claim 20, wherein the injection member is reciprocable within the housing, undergoing injection strokes and return strokes in an alternating sequence. 22. The engine of claim 21 , wherein, during the injection stroke, the member moves toward the second region carrying a volume of drive fluid, the member sealingly engaged with the housing and having a groove, the volume of drive fluid Introduced into the tank at a first area and transported from the tank at a second area. 23. The engine of claim 21, wherein the injection member moves towards the first area during the injection stroke, displacing the driving fluid from the first area to the second area, the housing being equipped with inlet and outlet valves, The inlet and outlet valves are opened and closed in a timed manner to introduce drive fluid into the first zone at the start of the spray stroke and to allow drive fluid to be withdrawn before the return stroke begins. 24. An energy source for a cryogenic engine comprising a body of semi-melted gas suitable for use as a drive fluid (or source thereof) for a cryogenic engine. 25. The energy source of claim 24, wherein the body of semi-melted gas is maintained in the container at or above atmospheric pressure. 26. The energy source of claim 25, wherein the container is a fuel tank of a cryogenic engine. 27. The energy source of claim 25, wherein the container is a storage tank (stationary or mobile) for refueling a cryogenic engine. 28. Energy source according to claim 26, characterized in that said container has a capacity of up to 100 liters, which also corresponds to the maximum volume of the body of semi-melted gas therein. 29. Energy source according to claim 26, characterized in that the capacity of the container and thus the maximum volume of the body is 250-300 liters. 30. Energy source according to claim 26, characterized in that the capacity of the container and thus the initial volume of the body is at least 1000 liters. 31. Energy source according to claim 24, characterized in that a body of semi-melted gas is used as a device for storing energy obtained from off-peak power generated by a power station, said body having a volume of the order of million liters. 32. A cryogenic engine and an energy source connected thereto, said energy source comprising semi-melted gas used as a drive fluid for the engine, or as a source of drive fluid. 33. A cryogenic engine and energy source according to claim 32, characterized in that the cryogenic engine is an engine according to any one of claims 13-23.

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