Effect of Turbine Speed Parameter on Exhaust Pulse Energy Matching of an Asymmetric Twin-Scroll Turbocharged Heavy-Duty Engine

Abstract

<div>The two-branch exhaust of an asymmetric twin-scroll turbocharged engine are asymmetrically and periodically complicated, which has great impact on turbine matching. In this article, a matching effect of turbine speed parameter on asymmetric twin-scroll turbines based on the exhaust pulse energy weight distribution of a heavy-duty diesel engine was introduced. First, it was built as an asymmetric twin-scroll turbine matching based on exhaust pulse energy distribution. Then, by comparing the average matching point and energy matching points on the corresponding turbine performance map, it is revealed that the turbine speed parameter of energy matching points was a significant deviation from the turbine speed parameter under peak efficiency, which leads to the actual turbine operating efficiency lower than the optimal state. In addition, a turbine speed parameter adjustment strategy was proposed by changing compressor impeller diameters to reveal the effect on turbine matching based on pulse energy weight. The testing results indicated that adjusting the impeller diameter could change the turbine speed parameter effectively. The matching aim is to make the turbine speed parameter close to the one under peak efficiency by changing impeller diameters. At last, this strategy was tested on a 12.5 L engine with EGR. The results showed that a more suitable turbine speed parameter could increase the turbine operating efficiency and the fuel economy by about 2% and 1%, respectively, at engine critical running region under the condition of maintaining the same NOx emissions.</div>