Effect of flow area ratio of scrolls to turbine on matching of exhaust pulse energy distribution of an asymmetric twin-scroll turbocharging heavy-duty diesel engine

The operation mode of an asymmetric twin-scroll turbine is significantly different from that of a steady state under exhaust pulse feeding conditions, which leads to a more complex matching between a turbine with an engine. In this paper, It was first studied that the matching effect of the flow area ratio of asymmetric twin-scroll to turbine wheel on the pulse energy distribution of asymmetric twin-scroll turbocharged engines. Firstly, It was compared that the deviation between turbine average efficiency on time average testing results and turbine cycle average efficiency based high frequency test results under the background of pulse energy distribution in the scheduling of asymmetric twin-scroll turbocharged engines, as well as a matching method based on pulse energy weight distribution was proposed. Furthermore, the impact of the flow area ratio of scrolls to turbine on matching was studied to further optimize turbine matching. Finally, the optimal and original turbines were tested on the engine to further demonstrate the accuracy and rationality of the results. The results showed that the turbine cycle-average efficiency and the engine fuel economy were improved by about 2%–4% and 0.8%, respectively at the middle and high speeds region of the engine with maintaining equivalent NOx emissions.