Study on turbocompound system for a heavy-duty diesel engine by combining matching analysis with experiments

In this work, to improve the fuel economy of long-haul commercial vehicles, the effects of turbocompound system matching on engine performance were numerically and experimentally studied. Firstly, a 1D GT-POWER simulation model of an 11 L heavy-duty diesel engine was established and verified by the experimental data. Secondly, the performances of the turbocompound engine matching with different sizes of fixed geometry turbine (FGT) and power turbines were analyzed. It was found that the exhaust energy distribution between the turbocharger turbine and power turbine had a significant impact on engine performance, and the size of the turbocharger turbine had a more noticeable impact than the power turbine. Based on the FGT turbocompound system simulation result, an appropriate variable geometry turbocharger (VGT) and three wastegate turbochargers (WGT) were selected for further simulation and experimental research. In addition, the impacts of the transmission ratio between the power turbine shaft and the engine crankshaft, and the fuel injection timing on the engine performance were experimentally studied. The engine test result showed that the fuel economy was improved by 1.6% under European Steady State (ESC) cycle while keeping the weighted NOx emission the same as the original engine. Finally, the turbocompound engine with WGT was installed on a heavy-duty long-haul commercial vehicle for road tests. The fuel economy of the vehicle was improved by 2.54% under the 80 km/h constant speed road test.