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In the context of increasingly serious carbon emissions and energy issues, it is key to solve the emission and performance problems of vehicle under cold start. In this study, environmental cost index was introduced to evaluate the weight of environmental impact of emissions to determine the focus of emission optimization under cold start. To this end, the energy flow experiment of heavy commercial vehicle cold start under C-WTVC was carried out. In addition, the steady-state bench test of the engine of the experimental vehicle was carried out. Through comparative analysis of sustainability parameters, it provides ideas for improving energy utilization under transient cold start conditions. The results demonstrate that the sustainability index is higher around 4.3 under high-speed steady conditions. And the performance is poor under transient conditions, which is only around 1.5. In addition, environmental costs are more sensitive to changes in CO and NO emissions. What's more, it should be pointed out that engine stability in the shifting process is especially important for the carbon emissions and energy utilization.

In order to narrow the gap between real-road and certification test fuel consumption rate of heavy-duty commercial vehicles. CHTC (China Heavy-duty vehicle Test Cycle) series test cycles have been developed, and will replace C-WTVC (China-World Transient Vehicle Cycle) test cycle in the latest standard for fuel consumption rate measurement of heavy-duty commercial vehicle. Due to the change of test cycle, the fuel consumption limits standard should also be revised. In this paper, all kinds of the heavy-duty commercial vehicles have been chosen, and the fuel consumption rates under CHTC and C-WTVC have been measured. The fuel consumption values under idling, acceleration, deceleration and constant speed conditions were calculated after the treatment of same mileage. Also the fuel consumption rate under different conditions were compared in order to realize the reasons causing the fuel consumption rate variation. Results showed that the fuel consumption rate of CHTC were slightly lower than C-WTVC except for bus and coach. And the main reasons for the fuel consumption rate variation were attributed to the fuel consumption rate under constant speed condition and the accelerated condition. In addition, the driving efficiency of the two test cycles was another reason, that is, the difference of the duration of each condition under the same mileage. The longer the duration, the higher the fuel consumption.

In this paper, the vehicle energy flow test of a heavy hybrid commercial vehicle is carried out on the chassis dynamometer with an ambient chamber under the C-WTVC test cycle. Energy flow characteristics, driving modes, the power system and key component working status and efficiency of the vehicle are studied. The test results show that the energy used to drive the vehicle accounts for 30.99% of the total energy. Heat transfer loss of the radiator and the motor cooling loop accounts for 8. 89% and 2.6% of the total energy respectively. The remainder loss accounts for 50.67% of the total energy which includes engine pump gas loss, friction loss, combustion loss and exhaust enthalpy increase. In the driving mode, pure electric drive, parallel drive, drive power generation and the energy recovery mode account for 9.1%, 29.56%, 18.51% and 23.61% of the total cycle time respectively. The recovery efficiency of braking energy is 81.95%. There are about 65% of the engine working points located below 200 g/ (kW ⋅ h) areas, and the thermal efficiency of the engine is 36.81% during the whole test cycle. About 24% of the motor working points are located in areas with a mechanical efficiency exceeding 94%. About 53% of the motor working points are located in areas with a mechanical efficiency below 92%, which mainly appear when the motor is driven by the engine to generate electricity or recover energy. This study provides guidance for improving the energy efficiency of hybrid commercial electric vehicles, and the following research can be focused on reduction of engine remainder loss and optimization of engines and motor working points. [ABSTRACT FROM AUTHOR]

The emission characteristics under different operating modes (engine mode and hybrid mode) and different test cycles (C-WTVC and CHTC) of a heavy-duty hybrid electric dump truck was investigated on the chassis dynamometer. The emission performance was recorded using Portable Emissions Measurement System (PEMS) and analyzed combined with the characteristic parameters of the test conditions. It is found that the NOx emission under hybrid mode is higher than that under engine mode, while the CO emission under hybrid mode is lower than engine mode. Under engine mode, the NOx emission of CHTC is higher than that of C-WTVC. However, under hybrid mode, the NOx emission of CHTC is lower than C-WTVC. Analysis of CO emission characteristics shows that under engine mode, CO emission is concentrated at low speed and small load condition, while under hybrid mode, CO emission is concentrated at high speed and large load condition.

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In this paper, the simulation method of calculating the fuel consumption of heavy-duty commercial vehicles based on VECTO (Vehicle Energy Consumption Calculation Tool) was introduced, and the fuel consumption of four vehicles under C-WTVC and CHTC cycles was calculated with VECTO. The differences between C-WTVC and CHTC cycles were analyzed by comparing the characteristic parameters, and the fuel consumption map and driving acceleration of two cycles were compared, so as to explore the influence of different test cycles on fuel consumption. The results show that compared with the C-WTVC cycle, the fuel consumption of CHTC cycle increases by 17.08g/km~28.12g/km, with an increase of 6.42%~17.26%. Most of the engine working points in the CHTC cycle work in the middle and low speed and torque regions and the acceleration range of CHTC cycle is wider are important reasons for the increase of fuel consumption.

• Continuous acceleration and deceleration lead to more unnecessary coolant energy loss because of increases the coolant temperature variation range. • Compared the sensitivity of coolant flow with the change of vehicle speed under the warm start, the coolant flow has a great lag under cold start. • The torque is mainly distributed in the medium region, while speed range is from 1100 to 1400 rpm under C-WTVC. • Keeping the vehicle in a stable running condition is beneficial to improve the effective thermal efficiency. In order to improve the actual performance of China-VI heavy-duty vehicle (HDV), the energy flow test on a HDV was conducted under the C-WTVC (Chinese-World Transient Vehicle Cycle). Then, the transient energy distribution of heavy-duty diesel engine was compared with different start condition. Results show that, the energy flow is greatly affected by the variation of actual vehicle conditions. The percentage of coolant energy fluctuates between 6% and 76%. In the urban cycle, the exhaust energy is slightly higher under cold start condition due to the high engine speed at the beginning of this condition. In the expressway cycle, the coolant loss ratio fluctuates slightly and stabilizes around 20% and the percentage of exhaust energy is around 32% in the later constant speed stage. What's more, idle and variable working conditions can cause a large energy loss, such as the acceleration and deceleration of C-WTVC. All those provide guidance for improving the actual energy efficiency of HDVs. [ABSTRACT FROM AUTHOR]