Real-Time Black Carbon Emissions from Light-Duty Passenger Vehicles Using a Portable Emissions Measurement System

Black carbon(BC)is considered the second largest anthropogenic climate forcer,but the radiative effects of BC are highly correlated with its combustion sources.On-road vehicles are an important source of anthropogenic BC.However,there are major uncertainties in the estimates of the BC emissions from on-road light-duty passenger vehicles(LDPVs),and results obtained with the portable emissions measurement system(PEMS)method are particularly lacking.We developed a PEMS platform and evaluated the on-road BC emissions from ten in-use LDPVs.We demonstrated that the BC emission factors(EFs)of gasoline direction injection(GDI)engine vehicles range from 1.10 to 1.56 mg.km^(-1),which are higher than the EFs of port fuel injection(PFI)engine vehicles(0.10–0.17 mg.km^(-1))by a factor of 11.The BC emissions during the cold-start phase contributed 2%–33%to the total emissions.A strong correlation(R^(2)=0.70)was observed between the relative BC EFs and average vehicle speed,indicating that traffic congestion alleviation could effectively mitigate BC emissions.Moreover,BC and particle number(PN)emissions were linearly correlated(R^(2)=0.90),and compared to PFI engine vehicles,the instantaneous PN-to-BC emission rates of GDI engine vehicles were less sensitive to vehicle specific power-to-velocity(VSPV)increase in all speed ranges.

Direct identification of total and missing OH reactivities from light-duty gasoline vehicle exhaust in China based on LP-LIF measurement

Considerable efforts have been devoted to characterising the chemical components of vehicle exhaust.However,these components may not accurately reflect the contribution of vehicle exhaust to atmospheric reactivity because of the presence of species not accounted for(“missing species”)given the limitations of analytical instruments.In this study,we improved the laser photolysis–laser-induced fluorescence(LP-LIF)technique and applied it to directly measure the total OH reactivity(TOR)in exhaust gas from light-duty gasoline vehicles in China.The TOR for China Ⅰ to Ⅵ-a vehicles was 15.6,16.3,8.4,2.6,1.5,and 1.6×10^(4) sec^(-1),respectively,reflecting a notable drop as emission standards were upgraded.The TOR was comparable between cold and warm starts.The missing OH reactivity(MOR)values for China Ⅰ to Ⅳ vehicles were close to zero with a cold start but were much higher with a warm start.The variations in oxygenated volatile organic compounds(OVOCs)under different emission standards and for the two start conditions were similar to those of the MOR,indicating that OVOCs and the missing species may have similar production processes.Online measurement revealed that the duration of the stable driving stage was the primary factor leading to the production of OVOCs and missing species.Our findings underscore the importance of direct measurement of TOR from vehicle exhaust and highlight the necessity of adding OVOCs and other organic reactive gases in future upgrades of emission standards,such that the vehicular contribution to atmospheric reactivity can be more effectively controlled.

Research on ammonia emissions characteristics from light-duty gasoline vehicles

In this study,ammonia emissions characteristics of typical light-duty gasoline vehicles were obtained through laboratory vehicle bench test and combined with New European Driving Cycle(NEDC)condition and Worldwide Harmonized Light Vehicles Test Cycle(WLTC)condition.The influence of ambient temperature on ammonia emissions is mainly concentrated in the cold start stage.The influence of ambient temperature on ammonia emission is shown that the ammonia emissions of light-duty gasoline vehicles under ambient temperature conditions(14 and 23℃)are lower than those under low ambient temperature conditions(-7℃)and high ambient temperature conditions(35 and 40℃).The influence of TWC on ammonia emission is shown that ammonia is a by-product of the catalytic reduction reaction of conventional gas pollutants in the exhaust gas in the TWC.Under NEDC operating conditions and WLTC operating conditions,ammonia emissions after the catalyst are 45 times and 72 times that before the catalyst,respectively.In terms of ammonia emissions control strategy research,Pd/Rh combination can reduce NH3 formation more effectively than catalyst with a single Pd formula.Precise control of the engine’s air-fuel ratio and combination with the optimized matched precious metal ratio TWC can effectively reduce ammonia emissions.

Influence of ambient temperature on the CO_(2)emitted of light-duty vehicle

Because of global warming,people have paid more attention to greenhouse gas emitted by vehicles.To quantify the impact of temperature on vehicle CO_(2)emissions,this study was conducted using the world light vehicle test cycle on two light-duty E10 gasoline vehicles a ambient temperatures of-10,0,23,and 40℃,and found that CO_(2)emission factors of Vehicle1 in the low-speed phase were 22.07%and 20.22%higher than those of Vehicle 2 at cold star and hot start under-10℃.The reason was vehicle 1 had a larger displacement and more friction pairs than vehicle 2.There was the highest CO_(2)emission at the low-speed phase due to low average speed,frequent acceleration,and deceleration.The CO_(2)temperature factor and the ambient temperature had a strong linear correlation(R2=0.99).According to CO_(2)temperature factors and their relationships,CO_(2)emission factors of other ambien temperatures could be calculated when the CO_(2)emission factor of 23℃was obtained,and the method also could be used to obtain the CO_(2)temperature factors of different vehicles.To separate the effect of load setting and temperature variation on CO_(2)emission quantitatively a method was proposed.And results showed that the load setting was dominant for the CO_(2)emission variation.Compared with 23℃,the CO_(2)emission for vehicle 1 caused by load setting variation were 62.83 and 47.42 g/km,respectively at-10 and 0℃,while those fo vehicle 2 were 45.01 and 35.63 g/km,respectively.

基于整车转毂的轻型车油耗特征研究

为探究影响轻型汽油车油耗的因素和车载诊断系统(OBD)油耗数据的修正方法,以促进机动车油耗的精细化控制和管理,该文对不同轻型汽油车的油耗测量值进行了详细分析。以满足国V和国VIb排放标准的轻型汽油车(LDGVs)为研究对象,在全球统一轻型车测试循环(WLTC)工况下进行冷、热启动测试,同时用OBD读取发动机和整车的瞬态运行参数,再分别用碳平衡法和OBD空燃比法计算被测车辆在不同启动温度和不同速度段下的油耗,分析温度和速度对不同车辆的油耗影响。利用均值法补齐了OBD参数读取过程中的数据损失,提高了2种油耗计算方法在瞬时油耗上的线性相关性,并分析了OBD油耗计算的误差来源。结果表明:与国V车辆相比,国VIb车辆油耗受启动温度的影响更小,其冷启动油耗仅比热启动高2.02%~2.27%;加装了汽油车颗粒捕集器(GPF)的车辆比未加装车辆的100 km油耗高出约0.48 L,且由GPF导致的油耗增幅与行驶速度有关;发动机在低速段的反复启停会导致该阶段的油耗达到全阶段的1.46倍;OBD的油耗测量误差更多来自车辆减速阶段。

Variability of fuel consumption and CO_(2) emissions of a gasoline passenger car under multiple in-laboratory and on-road testing conditions

An increasing divergence regarding fuel consumption(and/or CO_(2)emissions) between realworld and type-approval values for light-duty gasoline vehicles(LDGVs) has posed severe challenges to mitigating greenhouse gases(GHGs) and achieving carbon emissions peak and neutrality. To address this divergence issue, laboratory test cycles with more real-featured and transient traffic patterns have been developed recently, for example, the China Lightduty Vehicle Test Cycle for Passenger cars(CLTC-P). We collected fuel consumption and CO_(2)emissions data of a LDGV under various conditions based on laboratory chassis dynamometer and on-road tests. Laboratory results showed that both standard test cycles and setting methods of road load affected fuel consumption slightly, with variations of less than 4%. Compared to the type-approval value, laboratory and on-road fuel consumption of the tested LDGV over the CLTC-P increased by 9% and 34% under the reference condition(i.e., air conditioning off, automatic stop and start(STT) on and two passengers). On-road measurement results indicated that fuel consumption under the low-speed phase of the CLTC-P increased by 12% due to the STT off, although only a 4% increase on average over the entire cycle. More fuel consumption increases(52%) were attributed to air conditioning usage and full passenger capacity. Strong correlations(R2> 0.9) between relative fuel consumption and average speed were also identified. Under traffic congestion(average speed below 25 km/hr), fuel consumption was highly sensitive to changes in vehicle speed. Thus,we suggest that real-world driving conditions cannot be ignored when evaluating the fuel economy and GHGs reduction of LDGVs.

NDIR方法应用于汽油车NO排气检测的试验研究

为改善在用点燃式轻型汽车简易工况NO排气检测准确性,将NDIR检测法应用于NO的排放检测。采用比对测试方法,在184辆在用轻型汽油车的ASM排放检测中,同时采用NDIR方法与通用的电化学法进行排气NO浓度测试。测试结果表明,对于NO检测,NDIR方法与工况的跟随性较电化学方法好,电化学方法测试响应时间较NDIR方法滞后7~8s。采用有限差分法对两种检测方法的检测灵敏度进行分析,得出NDIR法的灵敏度为11.87,电化学法为6.97。分析NDIR法、电化学法两种检测方法下NO测试浓度值的相关性,发现两者高度线性相关,相关系数为0.98。研究结果表明NDIR方法完全适用于ASM工况NO排气浓度检测,其检测准确率较电化学方法高。