| Abstract:Based on a high-pressure common rail heavy-duty diesel engine, a one-dimensional thermodynamic simulation model was built. Firstly, the effects of single-stage turbocharged (1TC) and two-stage turbocharged (2TC) on the operational characteristics of diesel engine under variable altitudes were conducted. Afterward, the high-pressure stage of 2TC was replaced with a variable geometry turbocharger to investigate the effects of the blade opening on the performance of the diesel engine at an altitude of 4 km. The results show that compared with 1TC, 2TC can further improve the adaptability of diesel engine to altitude changes, especially in low-speed operational conditions. In low-speed operational conditions, the regulated two stage turbocharging (RTST) systems diesel engine has a maximum torque, highest effective thermal efficiency and lowest break specific fuel consumption (BSFC) when the blade opening were between 40% and 70%. As the speed increases, enlarging the blade opening can reduce the exhaust back pressure and residual exhaust gas in the cylinders, increase the efficiency of the turbocharger, decrease NOx emissions and BSFC; at low-speed operational conditions, the heat transfer loss rate decreases firstly and then increases with the increase of the blade opening. At medium and high-speed operational conditions, the heat transfer loss rate decreases with the increase of the blade opening. |