Abstract: The present invention provides a method of operating an engine (14) having one or more cylinders (16) each having a piston (18) within the cylinder (16) and each piston (18) having an expansion stroke and a return stroke and a top dead center (TDC) position and a bottom dead center position (BDC) and said engine (14) employing a working fluid (WF) and a heat exchange fluid (HEF), comprising the steps of: introducing the HEF during the return stroke of the engine; introducing the working fluid (WF) during the expansion stroke of the engine; causing the exhaust valve to be opened at or near bottom dead center of the piston BDC; delivering the HEF to the cylinder (16) after the exhaust valve has been opened; and closing the exhaust valve before TDC, such as to allow the working fluid to be compressed by the piston within the cylinder. The invention also provides an engine (14) capable of being operated in accordance with the method.

Abstract: The present invention provides a method of operating an engine (14) having one or more cylinders (16) each having a piston (18) within the cylinder (16) and each piston (18) having an expansion stroke and a return stroke and a top dead centre (TDC) position and a bottom dead centre position (BDC) and said engine (14) employing a working fluid (WF) and a heat exchange fluid (HEF), comprising the steps of: introducing the HEF during the return stroke of the engine; introducing the working fluid (WF) during the expansion stroke of the engine; causing the exhaust valve to be opened at or near bottom dead centre of the piston BDC; delivering the HEF to the cylinder (16) after the exhaust valve has been opened; and closing the exhaust valve before TDC, such as to allow the working fluid to be compressed by the piston within the cylinder. The invention also provides an engine (14) capable of being operated in accordance with the method.

Abstract: A cryogenic engine system and method for delivering cryogen to a cryogenic engine are provided. The cryogenic engine system comprises a tank for storing liquid cryogen, a cryogenic engine, a pump configured to pressurize cryogen from the tank, a first conduit for transporting cryogen between the pump and the cryogenic engine, a second conduit for transporting cryogen from the pump back to the tank, and a first valve disposed in the second conduit for controlling the flow of cryogen from the pump back to the tank. A pre-mixing system for a cryogenic engine and a method for mixing cryogen with a heat exchange fluid (HEF) are also provided.

Abstract: A cryogenic engine system and method for delivering cryogen to a cryogenic engine are provided. The cryogenic engine system comprises a tank for storing liquid cryogen, a cryogenic engine, a pump configured to pressurise cryogen from the tank, a first conduit for transporting cryogen between the pump and the cryogenic engine, a second conduit for transporting cryogen from the pump back to the tank, and a first valve disposed in the second conduit for controlling the flow of cryogen from the pump back to the tank. A pre-mixing system for a cryogenic engine and a method for mixing cryogen with a heat exchange fluid (HEF) are also provided.

Abstract: Injection apparatus is provided for injecting a drive fluid, such as liquefied nitrogen, into the working chamber (50) of a cryogenic engine. Liquefied nitrogen is admitted to a housing (36) of the apparatus under the control of an inlet valve (42) and expelled from the housing (36) under the control of an outlet valve (48). In the housing (36), heat is transferred to the liquid nitrogen to cause a small volume of the liquefied nitrogen to boil and thereby inject the drive fluid into the cryogenic engine under pressure. In each of two embodiments (FIGS. 1 to 7) the liquid nitrogen is transferred to a warmed region of the housing by a moveable injection member (4, 20) and in two further embodiments the housing is formed as a heat exchanger through which the nitrogen passes.