An investigation on asymmetric flow characteristics of asymmetric twin-scroll turbine

Abstract

Asymmetry, as the most significant characteristic of asymmetric twin-scroll turbines, has a significant effect on the flow characteristics of asymmetric twin-scroll turbines. In this paper, the effect of asymmetry on flow parameters, efficiency, twin-scroll pressure ratio ( SPR), single admission twin-scroll flow parameters ratio ( SSMR) and twin-scroll divide wall of asymmetric twin-scroll turbines were investigated for the first time. First, several turbines with the same total critical section of twin scrolls and different asymmetries were designed, as well as several turbines with the same asymmetric twin scrolls and different heights of the divide wall. Subsequently, these asymmetric twin-scroll turbines were tested and studied on the turbine performance rig. Asymmetry had little influence on turbine flow characteristics under equal admission, but a great impact under partial and single admission. Meanwhile, SMR had a low slope linear relationship with the expansion ratio for every asymmetry turbine. Moreover, the asymmetry was approximately linear with the average single admission twin-scroll pressure ratio ( SSMR ave), which could be used to guide the early design of asymmetric twin-scroll turbines. Besides, divide wall schemes testing found that the length of divide wall had a certain effect on the SSMR ave, which is a control factor to maintain asymmetric property. Finally, the relation between the expansion ratio of small or large scroll turbines and lg(SPR) was approximately exponential function, and the exponential parameter was strongly correlated with SSMR and SSMR ave, which could be the key parameter reflecting the asymmetry.