A Matching Method for Two Stage Turbocharging System

Abstract

The turbine system of a twostage turbocharger composed of high pressure turbine (HT), low pressure turbine (LT), and bypass valve decides distribution and utilization of exhaust gas energy and influence performance of twostage turbocharger in whole operational conditions. Besides, characteristics of turbine is expressed by envelop line of characteristic lines in different speeds. So turbine can be conveniently selected compared with compressor with similarity theory. Therefore, twostage turbocharger matching begins from turbine system matching in the paper. In twostage turbocharger, cooler efficiency, cooler loss, and bypass valve open besides turbochargers will influence turbocharging system performance and design of cooler and bypass valve are important contents of turbocharging system matching. The paper matched intercooler, bypass valve open, compressors, and turbines jointly. Calculation model for turbocharger matching was built, and turbine performance is get from reference turbine based on similarity theory; influence of compressor ratio distribution, cooler efficiency, and pressure drop in cooler imposing on compressor work was analyzed; and influence of turbine flow capacity and bypass valve imposing on output working in expanding process was studied; the method for matching of twostage turbocharging system in whole operational condition is studied. Matching analysis was made aiming at twostage turbocharging system of a type of high power density diesel engine, and design for turbocharging system was finished. Matching result using the method is compared to matching result using traditional method. Analysis result proves that using the method matching points in different operational conditions are located in more reasonable zone of compressor MAP.