Study on Through-flow Model for Turbine System Considering Three-dimensional Flow Field Distortion Effect

Abstract

Turbocharging is an important way to raise engine power density, save energy and reduce emission. Because turbocharger is driven by exhaust gas, energy utilization rate is a key factor for turbocharged engine performance. As a part transferring heat to mechanical energy, turbine efficiency decides exhaust gas energy utilization. Because of three-dimensional flow field distortion effect at outlet to exhaust manifold, turbine efficiency will be different from MAP when engine working. Influences by interaction in turbine system, turbine efficiency will decrease. So in order to evaluate turbine operating performance and design or select turbine more precisely, it is necessary to build a through-flow model for turbine which can consider three-dimensional flow field distortion effect.Unsteady flow field distortion at outlet to turbine was analyzed and flow field interaction law between exhaust manifold and turbine was studied. On the basis, six typical flow field distortion models in an engine operation cycle were raised. Then influences six models on each flow stage in turbine were analyzed. Further, models for exhaust manifold and turbine were built separately. Difference between unsteady three-dimensional simulation result and that based on turbine system through-flow model was compared and analyzed. Research result illustrated that difference of turbine cycle efficiency was only 0.1% and difference of turbine cycle work was 0.3%. So it can be deduced that turbine system through-flow model can predict turbine operation performance precisely and help turbine system matching exactly.