Fuel Consumption and NO _x Emission Prediction of Heavy-Duty Diesel Vehicles under Different Test Cycles and Their Sensitivities to Driving Factors

Due to the rapid development of road infrastructure and vehicle population in China, the fuel consumption and emission of on-road vehicles tested in China World Transient Vehicle Cycle (C-WTVC) cannot indicate the real driving results. But the test results in China Heavy-duty Commercial Vehicle Test Cycle-Coach (CHTC-C) based on the road driving conditions in China are closer to the actual driving data. In this paper, the model for predicting the performance of heavy-duty vehicles is established and validated. The fuel consumption and NO_x emission of a Euro VI heavy-duty coach under C-WTVC and CHTC-C tests are calculated by employing the developed model. Furthermore, the fuel consumption of the test coach is optimized and its sensitivity to the driving factors is analyzed. The results show that compared to the tests in C-WTVC, the fuel consumption and NO_x emission in CHTC-C increase by 6.5% and 11.2% respectively, while the average exhaust temperature decreases by 24°C and the urea injection timing is delayed by 36s. According to the scattered operation points of the diesel engine, it can be found that the operating points in C-WTVC is more concentrated in the high-efficiency area. By optimizing the gear shift strategy, the fuel consumption in CHTC-C reduces by 1.6%, but still higher than that in C-WTVC. Through the sensitivity analysis of the driving factors, it is demonstrated that the road grade and vehicle mass have the greatest impact on fuel consumption in both C-WTVC and CHTC-C, and an optimization of driveline efficiency and gear shift duration are more effective for reducing fuel consumption in CHTC-C compared with C-WTVC among these driving factors.