Heat Losses from the Turbine of a Turbocharged SI-Engine - Measurements and Simulation

Traditionally, heat losses from the turbine are neglected in turbomatching calculations as well as in engine simulations [1]. On the SI-engine, with it's high exhaust temperatures, this assumption will lead to errors in the calculations. Significant amounts of heat are dissipated from the turbine through several mechanisms. This paper contains measurements of the different heat loss mechanisms from the turbine during full load operation on a 4-cylinder SI-engine. The largest loss components are convective and radiative. The heat losses to cooling water and lubrication oil were approximately 3-5% of the total heat loss from the turbine. In addition to heat losses to the surroundings, heat flux is also present internally in the turbocharger. Heat flux from the turbine to the compressor can deteriorate the efficiency of the compressor. Measurements and calculations were performed for several heat flux conditions and it could be concluded that little possibility exists for significant heat flux through the rotor, instead the major heat flux comes from conduction in the housings and external radiation. With the heat transfer included in the model the turbine outlet temperature could be simulated very close to measured. However, incorporation of the heat losses in the simulation did not do very much for the necessity of using correction factors for the turbine efficiency.