Rapid compression machines: Heat transfer and suppression of corner vortex

A method to suppress the piston corner vortex generated in compressing gas mixtures in rapid compression machines has been developed. A piston crevice was designed to swallow the thermal boundary layer along the wall, allowing better definition of core conditions in the reacting mixtures by confining the cold gases to the wall. Axisymmetric calculations of the flow and temperature fields show that the proposed design indeed suppresses the vortex formation, keeping the core reacting cases intact. A simple thermodynamic model based on the piston displacement history was formulated, incorporating the predicted heat transfer to the walls and mass transfer to the crevices. The model predictions agree very well with experimental pressure history under a range of initial pressures and types of different gases. The new experimental device and model allows the incorporation of complex chemical kinetics with early hear release without the need for experimental approximations for the heat transfer terms. (C) 1998 by The Combustion Institute.