Simulation and analysis of combustion and heat transfer in low-heat-rejection diesel engine using two-zone combustion model and different heat transfer models

摘要

A comprehensive analysis of combustion, heat release, heat transfer and performance of a low-heat-rejection diesel engine was carried out for its potential development over the conventional diesel engine. A model for the prediction of combustion and heat release has been formulated and developed, based on the two-zone, combustion-modelling concept of WHITEHOUSE.N.D/WAY.R.J., and BALUWAMY.N. The combustion model takes into consideration on a zonal basis, the details of spray formation under non-swirl and swirling conditions, spray wall interaction, heat transfer, preparation and reaction rates. The penetration, deflection and growth of the spray are calculated based on the momentum added due to entrainment under swirl and non-swirl conditions. The combustion parameters were calculated based on the first law of thermodynamics using energy and enthalpy coefficients. The gas-wall heat transfer calculations are based on ANNAND.W.J.D, ANNAND. W.J.D & MA.T.H, LE FEUVRE.T., and WOSCHNI.G., heat transfer models for IC engines. A wall heat transfer model for the combustion chamber components along with the insulation coating was developed and formulated to simulate the low-heat-rejection condition. This model is coupled along with the above combustion and gas-wall heat transfer models to predict the effect of increased instantaneous wall temperature on heat release, gas-wall heat transfer, heat transfer through the engine components such as piston, cylinder head & cylinder liner and overall performance of a low-heat-rejection, direct- injection diesel engine. In this paper, the overall heat transfer on performance of conventional and operating conditions are simulated and analyzed. To validate the predicted results, experimental investigation were carried out under identical conditions on a six-cylinder, direct-injection Automotive diesel engine under conventional and insulated conditions using partially stabilized zirconia coating of thickness 0.5 mm and 1 mm for the combustion chamber components and outside surface of the cylinder liner. The predictions by the computer model, the experimental results and the capability of the model in predicting engine heat release, cylinder peak pressure, temperature and heat transfer details on zonal and cumulative basis are demonstrated, and the correlation are highly satisfactory.