A new asymmetric twin-scroll turbine with two wastegates for energy improvements in diesel engines

This paper first presented a new asymmetric twin-scroll turbine with two wastegates (ATST-2WG) for energy improvements. An asymmetric twin-scroll turbine with one wastegate (ATST-1WG) is relatively simple and can effectively solve the contradiction between low nitrogen oxide emissions and low fuel consumption when exhaust gas recirculation is employed. However, its disadvantage is that the fuel economy will decrease at a partial opening degree of the exhaust gas recirculation valve, especially at a high-speed engine range. An experimental investigation has been performed to calibrate the numerical model of a diesel engine equipped with an asymmetric twin-scroll turbine with one wastegate, and the engine with an asymmetric twin-scroll turbine with two wastegates model has also been especially established. Based on the models, both the wastegates control strategy and the critical parameter ASY turbine asymmetry (ASY, the ratio of the throat areas of the two scrolls) effect laws have been studied, and they are different from the asymmetric twin-scroll turbine with one wastegate. The brake specific fuel consumption advantage first remains unchanged and then decreases as the engine speed increases, and the maximum fuel economy improvement is 2.91% at the rated power point. The asymmetric twin-scroll turbine with two wastegates has great advantages to achieve a better balance of engine emissions and energy.