Cryogenic engines

Abstract

Slush gas, i.e. a gas or a mixture of gases cooled so that it is partially solid and partially liquid is employed as a drive fluid in a cryogenic engine. A cryogenic engine has a working chamber ( 50 ) connected to an energy source comprising a body of slush gas ( 47 ) via injection apparatus having a housing ( 36 ) which acts as a heat exchanger for causing part of the slush gas entering the injector to boil, so as to enable the gas to be driven under pressure into the working chamber ( 15 ).

1 . The use of slush gas as a drive fluid, or as a source of drive fluid, in a cryogenic engine. 
     
     
         2 . The use of slush gas in accordance with  claim 1 , wherein the slush gas is slush air. 
     
     
         3 . The use of slush air in accordance with  claim 2 , wherein the slush air is pre-treated by removing one or more constituents of air before it is liquefied and partially frozen. 
     
     
         4 . The use of slush air in accordance with  claim 3 , in which said constituents, which are removed, are water vapour and carbon dioxide. 
     
     
         5 . The use of slush gas in accordance with  claim 1 , in which the proportion of liquid to solid in the slush gas are in the range 70:30. 
     
     
         6 . The use of slush gas in accordance with  claim 5 , in which the proportions are in the range 60:40. 
     
     
         7 . A method of operating a cryogenic engine, the method comprising the step of supplying to the engine a cryogenic drive fluid comprising, or derived from, slush gas. 
     
     
         8 . A method according to  claim 7 , in which the slush gas is injected directly into a working chamber of the engine. 
     
     
         9 . A method according to  claim 8 , in which said injection is achieved by admitting a charge of the drive fluid into an inlet region of an injector housing via an inlet valve, closing said inlet valve, transferring heat to the fluid as the latter passes towards an outlet region of the housing, causing a small volume of the drive fluid to boil, and thereby injecting the fluid into the engine under pressure. 
     
     
         10 . A method according to  claim 8 , in which the fluid is injected into the engine through an outlet valve of the injector. 
     
     
         11 . A method according to  claim 10 , further comprising operating the valves in a timed relationship such that when the inlet valve opens to admit a charge of drive fluid the outlet valve is closed, after which the inlet valve closes, the pressure of drive fluid within the housing rises and the outlet valve opens for the delivery of the drive fluid under pressure. 
     
     
         12 . A method according to any of  claim 8 , in which the cryogenic engine, to which the slush gas is delivered, is used to power a vehicle or a stationary engine. 
     
     
         13 . A cryogenic engine for utilising slush gas as a drive fluid, the engine having injection apparatus delivering slush gas under pressure to the engine cylinder or other working chamber in which the drive fluid expands to provide the shaft power produced by the engine. 
     
     
         14 . An engine according to  claim 13 , in which the injection apparatus comprises a housing, an inlet valve for controlling the admission of the drive fluid to an inlet region of the housing and an outlet valve for controlling the delivery of the drive fluid from an outlet region of the housing, the housing being such that heat is transferred to the drive fluid in its passage from the inlet region to the outlet region, causing a small volume of the drive fluid in the housing to boil and thereby inject the drive fluid through the outlet valve and into the cryogenic engine under pressure. 
     
     
         15 . An engine according to  claim 14 , in which the inlet valve and the outlet valve operate in timed relationship such that when the inlet valve opens to admit a charge of drive fluid the outlet valve is closed, after which the inlet valve closes, the pressure of the drive fluid within the housing rises and the outlet valve opens for the delivery of the drive fluid under pressure. 
     
     
         16 . An engine according to  claim 14 , in which the housing is formed as a heat exchanger for the passage of a heat exchange liquid in order to transfer heat from the heat exchange liquid to the drive fluid. 
     
     
         17 . An engine according to  claim 16 , in which the heat exchanger is constituted by a plurality of pipes, which extend through the housing and through which the heat exchange liquid is passed. 
     
     
         18 . An engine according to  claim 17 , in which the pipes extend from the inlet region to the outlet region of the housing, the drive fluid occupying the spaces which is within the housing and which surrounds the pipes. 
     
     
         19 . An engine according to  claim 13 , in which the injection apparatus comprises a housing, and an injection member moveable within the housing in order to displace the drive fluid from a first region of the housing to a second region of the housing, in use the drive fluid, in a liquefied condition, being admitted to the first region of the housing and transferred to the second region by movement of the injection member, the second region being at a higher temperature than the first region, causing a small volume of the drive fluid in the second region to boil and thereby inject the drive fluid into the cryogenic engine under pressure. 
     
     
         20 . An engine according to  claim 19 , in which the injection member is moveable within the housing in a repetitive sequence timed to be in appropriate synchronism with the working cycle of the cryogenic engine, which may follow a two-stroke or a four-stroke cycle. 
     
     
         21 . An engine according to  claim 20 , in which the injection member is reciprocatable within the housing, undergoing injection strokes and return strokes in alternate sequence. 
     
     
         22 . An engine according to  claim 21 , in which on an injection stroke, the member moves towards the second region, carrying a volume of drive fluid with it, the member making sealing engagement with the housing and having a recess into which a volume of drive fluid is admitted at the first region and from which it is delivered at the second region. 
     
     
         23 . An engine according to  claim 21 , in which the injection member moves towards the first region on an injection stroke, displacing the drive fluid from the first region to the second region, the housing being equipped with inlet and outlet valves which open and close in timed manner to admit the drive fluid to the first region at the commencement of an injection stroke and allow egress of the drive fluid before the commencement of the return stroke. 
     
     
         24 . An energy source for a cryogenic engine, the energy source comprising a body of slush gas adapted for use as a drive fluid (or source thereof) for the cryogenic engine. 
     
     
         25 . An energy source according to  claim 24 , in which the body of slush gas is held in a container at atmospheric pressure or above. 
     
     
         26 . An energy source according to  claim 25 , in which the container is a fuel tank of the cryogenic engine. 
     
     
         27 . An energy source according to  claim 25 , in which the container is a storage tank (fixed or mobile) for refuelling a cryogenic engine. 
     
     
         28 . An energy source according to  claim 26 , in which the container has a capacity of up to 100 litres, which also corresponds to the maximum volume of the body of slush gas therein. 
     
     
         29 . An energy source according to  claim 26 , in which the capacity of the container, and hence the maximum volume of the body is 250-300 litres. 
     
     
         30 . An energy source according to  claim 26 , in which the capacity of the container and hence the initial volume of the body, is at least 1000 litres. 
     
     
         31 . An energy source according to  claim 24 , in which the body of slush gas is used as a means of storing energy derived from off peak power produced by a power station, the volume of the body being of the order of millions of litres. 
     
     
         32 . A cryogenic engine and an energy source connected thereto, the energy source comprising slush gas for use as a drive fluid, or source thereof, for the engine. 
     
     
         33 . A cryogenic engine and energy source in accordance with  claim 32 , wherein the cryogenic engine has injection apparatus apparatus delivering slush gas under pressure to the engine cylinder or other working chamber in which the drive fluid expands to provide the shaft power produced by the engine.