Research On Emission Limits For Exhaust Pollutants From In-Use Light Duty Vehicle Equipped Ignition Engine Under Simple Driving Mode Conditions

As the economy develops in China, the vehicular emissions have become the major source of air pollution in many cities with the rapid growth of vehicle population. At present, compared with the new vehicle emission standards, the in-use vehicle emission standards are seriously behind the control level, which go against the prevention of the increasingly severe air pollution in China. Studies on the emission limits for exhaust pollutants from in-use light duty vehicle equipped ignition engine under simple driving mode conditions have important meaning to determine the emission level of in-use light duty vehicle, and promote the in-use light duty vehicle emission reduction.This paper was based upon HJ/T240-2005standard and the emission data of in-use light duty vehicle equipped ignition engine under simple driving mode conditions. By analyzing the relationship between relative concentration of exhaust pollutants and cumulative frequency and utilizing the mathematical statistics methods, this research not only innovated in the determining method for exhaust pollutant emission limits under simple driving mode conditions, but also proposed the suggestions to revise the emission limits under simple driving mode conditions in China. Finally, this paper discussed the effect of vehicle aging on exhaust pollutants emissions. The main conclusions were summarized as follows:(1) The relative concentration of NO was more evenly distributed than CO and HC for tested vehicles under simple driving mode conditions, which demonstrated that the emission concentration of NO dominated the passage rate of vehicles in the simple driving mode tests.(2) It suggests that the CO and HC emission limits are determined in the range of cumulative frequency between the tangent point of curve slope equals to one and this cumulative frequency minus10%for pre-China1vehicles; The CO and HC emission limits are determined in the range of cumulative frequency between the tangent point of curve slope equals to one and this cumulative frequency plus10%for China1to China4 vehicles.(3) The passage rates of simple driving mode tests for pre-China1, China1/China2and China3/China4vehicles were set to45%,75%and90%, respectively, in the key areas; the passage rates of simple driving mode tests for pre-China1, China1/China2and China3/China4vehicles were set to65%,85%and94%, respectively, in the general areas.(4) Following the conclusions above, it suggests that the NO emission limits are determined with the passage rate of simple driving mode tests, both in different emission stages and in different reference masses classifications, after the setting of CO and HC emission limits. This method could be used to determine the exhaust pollutant emission limits under simple driving mode conditions.(5) The emission limits of NO for pre-China1, China1/China2and China3/China4vehicles were about40%,40%and50%lower than the corresponding limits of HJ/T240-2005in the key areas; the emission limits of NO for pre-China1, China1/China2and China3/China4vehicles were about5%,10%and30%lower than the corresponding limits of HJ/T240-2005in the general areas.(6) The average concentrations of CO, HC and NO fell in the ranges of0.9%-1.3%,115ppm-165ppm and890ppm-1450ppm, respectively, for pre-China1vehicles. The regression analysis revealed that the average concentrations of exhaust pollutants took on exponential growth along with the aging for the China1and China2vehicles those were2-11years old.