Abstract: An internal combustion engine system that converts thermal energy from an exhaust of an engine to mechanical energy includes a heat exchanger thermally coupled to an exhaust from an internal combustion process. The heat exchanger receives a heat transfer fluid therein. A generator is coupled to the heat exchanger. The heat transfer fluid expands and evaporates in the generator in response to heat from the exhaust of the internal combustion process. The expansion of the heat transfer fluid vapor converts thermal energy of the heat transfer fluid to mechanical energy.

Abstract: A method for use in generating power in an internal combustion engine from combustion of a fuel admixed with an oxidizing gas and operating cyclically with intentional ignition of a first fuel or with self-ignition of a second fuel which includes changing a volume of a combustion chamber from a fixed minimum volume to a fixed maximum volume wherein the maximum volume is greater than a critical volume. The critical volume includes a volume of the chamber filled with an oxidizing gas at an initial temperature and an initial pressure such that when the temperature is compressed from the critical volume to the minimum volume the gas reaches a maximum temperature and a maximum pressure causing detonation of a first fuel, or the gas exceeds a maximum temperature and a maximum pressure predetermined for self-ignition of a second fuel.