CFD Simulation and testing of a Turbocharger Compressor for various Impeller Design Variables

To meet the future engine emission legislations and efficiently use the fuel, automotive industries are downsizing the engine and depending on the turbocharger to deliver the high power when necessary. However, the design of a turbocharger compressor is very complex due to the transient nature and the high flow velocity and compressibility of the airflow. Modelling the airflow in the compressor requires high computation resources which could be challenging especially, when examining operating conditions that are close to surge and choke limits [1,2]. Different level of CFD complexity can be used depending on the level of details needed and objective of the study [3]. To ensure the assumptions made is not affecting the results, experimental testing using either in-house or commercial test facilities are commonly employed [2]. Various design parameters can affect the compressor performance and its range of operations [4,5]. Among these variables the inlet vane angle which can be varied to achieve high performance at various rotational speeds [6,7]. In this work, 3-D CFD model has been developed to simulate the airflow under steady operating conditions. The model utilizes RANS together with k- turbulence model to evaluate the compressor performance at various impeller rotational speed 60,000 to 140,000 rpm and inlet mass flow rates. Experimental test rig using continuous steady flow has been employed to validate the CFD model and reasonable agreement has been achieved. The effect of three design parameters (impeller leading-edge angle, impeller trailing-edge angle, splitter blade length) are examined and the effect of their deviation from its optimum value on the performance of the turbocharger compressor in terms of pressure boost, efficiency and range of the turbocharger are evaluated.