Experimental Research on the Matching Characteristics of the Compound VGT-STC System with a V-Type Diesel Engine

In order to improve the performance of a V-type diesel engine at low and medium speeds, the compound VGT-STC turbocharger system was proposed. First, the compound VGT-STC turbocharger system bench was established, which allowed to switch between the VGT and STC boosting systems. Then, the load characteristic tests with a variable VGT vane opening were conducted at different speeds in the 1TC and the 2TC, respectively. The results showed that the VGT-1TC could provide much more air into the cylinder than the VGT-2TC at 1000 r/min, and the maximum torque was increased by 4000 Nm (80%), and the BSFC decreased by 20.1 g/kWh on average. The matching characteristics are analyzed for three boosting control strategy systems, including the VGT, STC, and the compound VGT-STC. The results show that the VGT system has a steady increase of the maximum torque in both low and medium speeds, while the STC system has a large increase in torque at 1000 r/min and begins to decline when speed is greater than 1200 r/min, and the compound VGT-STC system combines the advantages of the VGT and STC, which can maintain 9000 Nm (83% rated torque at 1800 rpm) and a lower BSFC at both low and medium speeds. As a result, with the compound VGT-STC boosting control strategy system, the operating range has expanded by 10%, and its smoke opacity, BSFC, and exhaust temperature are reduced by 0.057, 8.2 g/kWh, and 64 °C, respectively.