Predicted Heat Transfer Loss in the Expansion Cylinder of a Two Cylinder Reciprocating Engine

摘要

Carmichael has proposed a direct injection, temperature ignition (TI), reciprocating engine design which divides the conventional four stroke cycle functions between a compression cylinder and an expansion cylinder, interconnected by a static regenerative heat exchanger. The prediction of heat transfer loss in the expansion cylinder is required to predict the performance of the new cycle. Woschni's correlations developed for direct injection, quiescent, four stroke, compression ignition (CI) engines, are used to predict uncorrelated expansion cylinder heat transfer loss. Laws of similarity allow, in principle, extrapolation outside the experimental data range for forced convection heat transfer only. General applicability of Woschni's correlations is established by examining the expansion cylinder quiescent condition, using predicted mean gas velocity magnitudes and fully developed, turbulent flow, forced convection models. Predicted radiant peak flame emissivity and temperature are found and compared with nominal peak values observed in conventional CI engine cycles to establish a minimum radiation flux reduction ratio. A mean reduction ratio for forced convection flux is also found. A corrected, conservative prediction of heat transfer loss in the expansion cylinder is then established.