Simulation of a centrifugal compressor to obtain the characteristic map through computational effort

Abstract

The association of turbochargers with piston engines is widespread since both the efficiency and the power output of an engine could be improved. However, a piston engine operational range is wide and highly variable. This characteristic imposes challenges for the project and application of a turbocharger that should perform properly within the operational range. An important tool used to evaluate the performance of both turbine and compressor, which compose a turbocharger, is the characteristic map. The map condenses the main performance parameters into a single graphic that allow the evaluation of the machine characteristics, such as the operational width. A typical characteristic map relates the pressure ratio, mass flow rate, rotation and efficiency for each operational condition. The present work provides a technique to obtain the characteristic map of a turbocharger centrifugal compressor with reduced time consumption through steady state simulation using a fully unstructured mesh. Evaluation of the results indicated good accuracy for the predicted mass flow rate and pressure ratio. However, the resulting efficiency presented considerable discrepancy, which was aggravated when simulating extreme operational conditions or when the mass flow was used as a boundary condition. At last, the porter shroud and volute were evaluated within the entire range to provide an insight into the compressor operation.