Study of instantaneous unsteady heat transfer in a rapid compression-expansion machine using zero- dimensional k-e turbulence model

Abstract

In this investigation, the instantaneous unsteady heat transfer within a pneumatically driven rapid compression-expansion machine that offers simple, well-controlled and known boundary conditions was studied. Values of the instantaneous apparent overall heat flux from the cylinder gas to the wall surfaces were calculated using a thermodynamics analysis of the experimentally measured pressure and volume temporal development. Corresponding heat flux values were also calculated through the application of a zero-dimensional k-e turbulence model. In the zero-dimensional k-e turbulence model (ZDM) the characteristic velocity is a contribution of turbulence kinetic energy, mean kinetic energy of charged air into cylinder and piston motion for the calculation of Reynolds, Nusselt and Prandtl numbers. Comparison of the zero-dimensional k-e turbulence model prediction with experimental data shows good agreement for all compression ratios (8.4~24.3).