Abstract: An internal combustion engine of the gasoline-burning variety has an essentially constant maximum displacement or volume. This requires compromises in design to achieve acceptable power output at full throttle and reasonable thermal efficiency at cruising power. It would be desirable to have an engine with differing displacements for those operating conditions. However, the mechanical constraints of a conventional engine do not easily permit of that possibility. It is also desirable to separate the process of generating expandable fluid for an engine and the expansion of such fluid. This permits each of the two processes to be more closely optimized. Compression of fluid can be more nearly isothermal, and expansion which approaches truly isentropic expansion may be provided. It would also be desirable to capture waste heat from the combustion products within the expandable fluid for enhancing thermal efficiency of an engine.

Abstract: An internal combustion engine has an auxiliary cell connected thereto by a transfer valve. Approximately isothermally compressed gas, which may be a combustible mixture, is introduced into the cell through an input valve. A displacer piston in the cell is biased toward lower volume of the cell. In an illustrated embodiment, the displacer piston is translated by the compressed gas toward a larger volume in the cell. When the cell is fully charged with compressed gas, the input valve is closed and the transfer valve is opened for intermittently discharging the mass of gas in the cell into the cylinder of the internal combustion engine. The displacer piston displaces substantially all of the gas from the cell into the engine. Combustion is initiated and may, at least in part, occur within the cell, providing power to the engine as the gas expands and performs work by way of the engine piston.