Abstract: A cylinder for an internal combustion engine. A metallic ring (6) surrounds the top of the cylinder. An insulating ring (7) is provided at the top of the cylinder between the metallic ring and cylinder wall. The axial extent of the insulating ring (7) is less than that of the metallic ring (6) and is determined so that it diverts some of the heat away from the relatively poorly cooled zone towards the top of the cylinder, but does not significantly obstruct the heat flow to surrounding cooling channels (5).

Abstract: A passive valve assembly for controlling the flow into or out of chamber (3) through a port (4). The valve assembly comprises a valve element (5) arranged to open in the direction of flow through the port. The valve element (5) has a piston (9) which is reciprocable in a cylinder (10) containing gas. On opening of the valve, gas is compressed in a first chamber (11) of the cylinder (10), and this energy of compression is used to reverse the direction of the valve element (5) and return it to its seat.

Abstract: A two stroke internal combustion engine having a compressed air inlet port and an exhaust port the flow through which is controlled by suitable valves. Fuel is injected through a fuel injector. The timing of the opening of the valve is such that, as the piston approaches top dead centre and with the air inlet valve closed, the exhaust valve is closed such that some exhaust gas is trapped and compressed in the combustion chamber thereby increasing the temperature within the combustion chamber and hence facilitating ignition. The invention also contemplates initiating combustion before the air inlet valve is closed.

Abstract: A heat exchanger comprising a pressure vessel (1). A plurality of serpentines (8) convey a fluid to be heated through the pressure vessel (1) in one direction. A duct (9) surrounding the serpentines (8) conveys a second fluid in the opposite direction to give up its heat to the first fluid. The duct (9) is spaced from the pressure vessel (1) and is surrounded with thermal insulation (23). An opening in the duct (9) equalizes the pressure between the inside and the outside of the duct (9) which is also supported against expansion caused by the pressure inside the duct (9) exceeding the pressure outside the duct (9).

Abstract: An engine comprising an isothermal air compressor (1) into which liquid is sprayed as the air is compressed. A combustion chamber (4) receives and expands the compressed air from which the liquid has been removed, to generate power. A precompressor (21, 27) compresses the air upstream of the isothermal compressor. The compressed air from the isothermal compressor receives heat from the exhaust gas from the combustion chamber in a primary heat exchanger (3). A secondary heat exchanger (31, 45) transfers heat recovered from a part of the engine to the compressed air from the isothermal compressor (1) upstream of the primary heat exchanger (3).