Reciprocating piston internal combustion engine

A low compression ratio reciprocating piston internal combustion engine comprises a piston and cylinder arrangement including a working volume in which the compression and power stages of the engine operating cycle occur, the working volume being bounded in part by the piston crown and the cylinder head and in part by inlet valve means whereby an inlet charge can enter the working volume and exhaust valve means whereby products of combustion occuring within the working volume can leave the working volume, a regenerative heat exchanger located within said working volume, the heat exchanger having a hot face and a cold face between which gases are caused to flow, and, means whereby the charge is caused to flow through the heat exchanger from the cold face to the hot face so as to be heated thereby immediately prior to the combustion stage of the engine operatine cycle, the burning and expanding fuel/air mixture is caused to act directly on the piston of the piston and cylinder arrangement without passing through the heat exchanger, and the products of combustion are subsequently caused to flow through the heat exchanger from the hot face to the cold face to heat the heat exchanger before leaving the working volume by way of the exhaust valve means, wherein the hot face of the regenerative heat exchanger is permanently exposed to the crown of the piston and said means whereby the charge can flow includes a by-pass whereby during compression of the inlet charge the charge can flow through said by-pass to the region of the cold face of the heat exchanger without passing through the heat exchanger.

A low compression ratio reciprocating piston internal combustion engine comprises a piston and cylinder arrangement including a working volume in which the compression and power stages of the engine operating cycle occur, the working volume being bounded in part by the piston crown and the cylinder head and in part by inlet valve means whereby an inlet charge can enter the working volume and exhaust valve means whereby products of combustion occuring within the working volume can leave the working volume, a regenerative heat exchanger located within said working volume, the heat exchanger having a hot face and a cold face between which gases are caused to flow, and, means whereby the charge is caused to flow through the heat exchanger from the cold face to the hot face so as to be heated thereby immediately prior to the combustion stage of the engine operating cycle, the burning and expanding fuel/air mixture is caused to act directly on the piston of the piston and cylinder arrangement without passing through the heat exchanger, and the products of combustion are subsequently caused to flow through the heat exchanger from the hot face to the cold face to heat the heat exchanger before leaving the working volume by way of the exhaust valve means, wherein said heat exchanger is movable within the working volume between a first position wherein the cold face thereof is exposed to the piston crown and a second position wherein the hot face is exposed to the piston crown, the exchanger occupying its first position during compression of the charge and dividing the working volume so that the charge is caused to be heated by passing through the heat exchanger from the cold face to the hot face prior to combustion and the heat exchanger occupying its second position during the power and exhaust stages wherein the burning and expanding fuel/air mixture can act directly on the piston, and the resultant products of combustion are caused to flow through the heat exchanger from the hot face to the cold face, heating the heat exchanger, to leave the working volume by way of the exhaust valve means.