In the automotive industry, the demand for fuel economy and emission reduction has led to the downsizing of engines and turbochargers play a leading role in compensating for the performance loss. In complex flow modelling of the compressor, effective determination of the mesh resolution is not a priori due to variation of local flow and turbulence variables. In this study, the compressible flow of a centrifugal turbocharger compressor was numerically modelled. The accuracy of the models is discussed with respect to boundary layer adaptivity for the k-w SST turbulence model.
The numerical models are investigated and verified against pick efficiency, extracted experimental points at 150,000 (rpm), along with other points of partial load at 80,000 (rpm) speed lines. The TD025-05T4 compressor of the 1.2 Litre engine Renault Megane passenger car was designed, constructed and provided experimental data (compressor map) by Mitsubishi Turbocharger and Engine Europe (MTEE). In addition, a numerical and mathematical study has been developed on the aerodynamic optimisation of the turbocharger compressor diffuser geometry.
The optimisation of the single-target problem (efficiency) of the axial flow compressor outlet stage is carried out using a new smart evolutionary optimisation technique named adjoint solver. The Adjoint solver usually produces a surface vector field that shows how and where the geometry can be changed for optimisation based on a defined objective, efficiency in this study. Such irregular and non-parametric changes could be manufactured using recent advances in 3D printing technology.
The expected result of optimisation of the diffuser geometry started with the design point, central area, 150,000 (rpm) speed line, shows a gradual development of efficiency to an uttermost of 2.5% and the process of optimisation has been enlarged and completed on all design operating areas selected previously. The development of an optimised geometry diffuser accomplishes a wider operating range, high efficiency and robust performance due to changes in engine operating conditions in the high-pressure area.
Therefore, the optimal diffuser geometry leads to an impact on the engine’s efficiency and overall performance of a passenger car for real-world drive cycles, increasing power output and improving thermal efficiency.