A study of super-adiabatic combustion engine

A one-dimensional numerical calculation has been performed on a reciprocating heat engine with super-adiabatic combustion in porous media. The system consists of two pistons and a thin porous medium in a cylinder; one being a displacer piston and the other a power piston. These create reciprocating motions with a phase relation, similar to those of an ordinary Stirling engine. By means of the reciprocating flow system, the residual combustion gas enthalpy is effectively regenerated to induce enthalpy increase in the mixture through the porous medium, which provides heat storage. The results show that due to heat recirculation, the maximum temperature is higher than the theoretical one in free space. Furthermore, using a porous medium with a high absorption coefficient, since the thermal diffusion by radiation decreases in the porous medium, the maximum temperature increases, resulting in the extension of the flammability limit for the heat engine. (C) 1997 Elsevier Science Ltd.