Search

Diurnal evaporative testing of atmospheric fuel system with no-load canister for 14 days and half load canister for 7 days is carried out according to the US EPA BETP test procedure. In addition, the atmospheric fuel system and pressurized fuel system were tested for BETP for 72h diurnal evapration respectively.The results show that the total emissions of the atmospheric fuel system in 72h is 210mg, and the proportion of respiratory emissions is between 90% - 95%. The 72h total emissions of the pressurized fuel system is about 120mg, and the permeation emissions of the fuel tank accounts for about 82% - 90%. The total respiratory emissions of the atmospheric fuel system are 130.4 mg, mainly alkanes, accounting for 70% - 80%. The pressurized fuel system is dominated by the permeation emission of the fuel tank, with a total amount of 127.5 mg, mainly composed of alkanes, aromatic hydrocarbons and OVOCs, accounting for 45% - 50%, 43% - 47% and 3% - 5% respectively. In the canister breakdown test of gasoline vehicle fuel system, the THC emissions of no-load test and 7-day half load test are similar; the VOCs composition in the first 12 days is similar to that in the 3-day test, mainly alkanes. After the canister breakthrough, the proportion of aromatic hydrocarbons and OVOCs increases significantly.

Vehicular refueling emission is a potential source of urban atmospheric volatile organic compounds (VOCs) that is not well understood and controlled. China 6 vehicles have been equipped with the onboard refueling vapor recovery (ORVR) system to cut down refueling emissions, while the emission characteristics and reduction effectiveness are rarely reported. In this study, we conducted laboratory tests to measure the refueling emissions from ten China 6 vehicles and three China 5 vehicles (refueling-emission-uncontrolled, REU) and developed an inventory in a typical middle-sized Chinese city (Langfang) to explore the emission reduction resulted from relevant policies. Compared with headspace vapor and refueling vapor from REU vehicles, the emission profiles for China 6 vehicles are consist of considerably higher proportions of small alkanes and alkenes (C2-C3) and lower proportions of C6-C8 hydrocarbons. Such differences indicate that the headspace vapor profiles are incapable of representing the refueling emission for China 6 vehicles. The market-share-weighting emission factors (EFs) of total hydrocarbons (THCs) and total VOCs for China 6 vehicles are 11.2 mg/L and 6.4 mg/L, respectively, corresponding to control efficiency of approximately 98.8% compared with the REU vehicles. Based on the real-world EFs and the fuel consumption in Langfang, a refueling emission inventory with high spatiotemporal resolution is developed. The total refueling emission of THCs in Langfang is approximately 190.6 tons in 2018 and will likely decline to 25.0 tons in 2035. The implementation of the ORVR will contribute to 90% of the refueling emission reduction in 2035.

In order to study the gasoline working capacity and durability of the carbon canister, the gasoline working capacity test of the carbon canister was conducted under different test conditions. The results showed that the gasoline working capacity of the canister carbon decreased with the increase of fuel vapor loading rate. The fuel vapor volume ratio of the inlet has little effect on the gasoline working capacity. After 300 gasoline working capacity test cycles, the working capacity of butane decreased by about 20%. The fuel vapor adsorption amount in first cycle of each carbon canister is far greater than the desorption amount in first cycle, and also far greater than the adsorption and desorption amount in the subsequent cycles, which indicated that a large amount of fuel vapor occupied the active sites after the first use of the carbon canister and cannot desorb.

In order to improve the energy-saving effect of a pure electric vehicle, this paper analyzes the causes and influencing factors of the internal resistance loss of the automobile, and expounds the necessity of internal resistance optimization. Select a model in research and development, determine the resistance through the sliding resistance test, and evaluate the energy saving potential of the vehicle through the benchmarking method. A method of resistance decomposition is proposed. The resistance values of key components are tested and analyzed, and the optimization scheme is given. In order to verify the effect of the optimization scheme, this paper proposes a theoretical calculation method. After verification, the proposed optimization scheme finally improves the energy-saving effect of the vehicle by 3%.

Based on the research and comparison of the main contents and measurement methods for the inspection and Maintenance Program in the United States, the European Union, and China, and the analysis of the OBD inspection in China, it is found that the in-use vehicle measurement method in our country has covered the mainstream measurement methods, however, the overall system design still lacks corresponding standards and technical support for maintenance and closed-loop supervision, the cause of the OBD inspection failure is concentrated the malfunction of the oxygen sensor and three-way catalytic converter.

Vehicular evaporative emission is a major source of atmospheric volatile organic compounds (VOCs), while quantification and characterization of the evaporative emission in China, particularly for the vehicles meeting the latest emission standards, are rarely reported. In this study, we performed evaporative emission experiments in a sealed housing evaporative determination (SHED) using eleven new and in-use light-duty gasoline vehicles to investigate the evaporative VOCs emission from the China 5 and China 6 vehicles and unravel the deterioration of evaporation control system of in-use ones. The total hydrocarbon (THC) emission factors (EFs) of 24-h diurnal breathing loss from the new China 6, new China 5 and in-use China 5 vehicles are 0.25, 0.81 and 5.27 g/d respectively. Compared with headspace vapor, the emission profiles of both hot soak loss (HSL) and diurnal breathing loss (DBL) from all new tested vehicles contain more C7–C9 aromatics, particularly for the China 6 vehicles. C4–C5 alkanes and C7–C9 aromatics account for most of total VOCs mass for all China 5 vehicles, while emissions from the China 6 vehicles exhibit no strongly prevailing species for both HSL and DBL emission. Typical ratios like normalized ratios of benzene, toluene and ethylbenzene can be used to distinguish evaporative emission from vehicular exhaust. Ozone formation potentials (OFPs) of the in-use China 5 vehicles are 5.35 and 7.16 times higher than that of China 5 new ones in DBL and HSL experiments respectively. Secondary organic aerosol formation potential of all tests ranged from 17.30 to 29.76, with aromatics contributing the largest proportion (over 90.0%). With the implementation of China 6's standard, the evaporative THC emission in China may peak in 2022 and will be cut down by 76% until 2030. Also, the underestimation of evaporative emission was estimated when neglecting the difference of EFs between new and in-use vehicles.

Through the fuel consumption test of several listed vehicles in China, the basic fuel consumption results of cold start under CLTC-P cycle, the fuel consumption results of vehicles under the condition of air conditioning on, and the fuel consumption results of vehicles under the condition of air conditioning off are measured. At the same time, the differences between NEDC cycle and CLTC-P cycle in China's fuel consumption certification test are compared, and the results of fuel consumption test are combined The fuel consumption test results under CLTC-P cycle are higher than those under NEDC cycle, and the fuel consumption test procedures under Chinese condition are more in line with the actual driving situation in China.

This paper briefly introduces the progress of evaporative emission standards for light-duty vehicles in developed countries such as the United States and Europe, and the test procedures specified in the latest evaporative emission standard were concluded. Moreover, the development of evaporative emission standards for light-duty vehicles in China was comparatively analyzed. The evaporative emission test data from 2004 to 2019 was randomly selected for analysis of the trend of evaporative emission performance of vehicles in China with the use of EPR. Affected by the more stringent China 6 Evaporative Emissions standards issued in 2016, the EPR value of the evaporative emission test conducted according to the China 5 had continuously decreased to 41% in 2018. Subsequently, the EPR value increased again to a value of 60% in 2018 and 2019 due to strengthen of the emission limit from 2g to 0.7g and the raise of deterioration factor. Finally, based on the world's latest evaporative emission standards, the development trend of evaporative emission standards for light-duty vehicles in China is forecasted. The application of canister bench aging test, BETP, running loss emission test, and a test cycle with Chinese characteristics may be more conducive to control the light-duty vehicle emissions. Compared with the LEV 3, the evaporative emission limit of 0.7g/test specified in China 6 is still relatively larger. In addition, strengthen the control of durability test and in-use emission performance test would makes the HC emission less during the actual operation of the vehicle.

Based on a plug-in hybrid car equipped with a 1.5L turbocharged direct injection gasoline engine, this paper studies the emission and fuel consumption characteristics of the prototype vehicle under three different cycle conditions, WLTC city, WLTC and CLTC-P. The results show that for the four pollutants: CO, THC, NMHC and NOx, WLTC city cycle emissions are the largest, WLTC cycle emissions are the smallest, CLTC-P cycle emissions are the middle. For N2O, WLTC cycle has the largest combined emissions, CLTC-P cycle combined emissions are the smallest, and WLTC city cycle combined emissions are the center. The combined fuel consumption under WLTC city conditions is approximately 1.3 times the combined fuel consumption under the complete WLTC cycle. The combined fuel consumption under CLTC-P conditions is approximately 1.25 times that of the complete WLTC cycle. The first phase of each cycle is the phase with the highest emissions and fuel consumption.

A model of fuel system which is with ORVR is established based on STAR CCM +, to study the influence of different refueling velocity on the formation of liquid seal in refueling process. The simulation results show that the increase of refueling rate leads to the formation of liquid seal in the process of fuel flow, but it will lead to the deterioration of refueling smoothness. When the refueling rate is 15L/min, there is no liquid seal formed at the bottom of the refueling pipe, because of the small gas resistance formed in the refueling process, and when the refueling flow rate reaches 37L/min, a stable dynamic liquid seal can be formed at the bottom of the refueling pipe but the fuel accumulation at the refueling port has taken place. When the refueling flow rate reaches40L/min and 45L/min, a stable dynamic liquid seal is formed at the bottom of the refueling pipe at 4s, but until 4 seconds, fuel has been submerged in the refueling muzzle. At 10 seconds, the fuel accumulation state is the same as 5 seconds, indicating that the gun PSO had taken happened.