Empirical Lumped-mass Approach to Modelling Heat Transfer in Automotive Turbochargers

When evaluating the performance of new boosting hardware, it is a challenge to isolate the heat transfer effects inherent within measured turbine and compressor efficiencies. This work documents the construction of a lumped mass turbocharger model in the MatLab Simulink environment capable of predicting turbine and compressor metal and gas outlet temperatures based on measured or simulated inlet conditions. A production turbocharger from a representative 2.2L common rail diesel engine was instrumented to enable accurate gas and wall temperature measurements to be recorded under a variety of engine operating conditions. Initially steady-state testing was undertaken across the engine speed and load range in order that empirical Reynolds-Nusselt heat transfer relationships could be derived and incorporated into the model. Steady state model predictions were validated against further experimental data. Model predictions for compressor wall temperature show very good correlation with measured data (average 0.4% error, standard deviation 1.27%) and turbine housing temperatures also demonstrate good agreement (average 2.7% error, standard deviation 3.58%). The maximum compressor and turbine wall temperature errors were 2.9% and 8.1% respectively at the steady state validation test conditions. This work demonstrates that a relatively simple approach to modelling the heat transfer within turbochargers can generate accurate predictions of housing temperatures and the knock-on impact on compressor and turbine gas outlet temperatures.