Abstract:35 China 5 stage taxis with high mileages between 160~500 thousand km were random selected in Beijing for the study of the emission deterioration characteristics. Emission characteristics of pollutants were tested with the Constant Volume Sampler on Chassis dynamometer before and after the catalysts of all taxis were replaced. The results showed that the emission factor of the China five stage high mileage taxi for CO、THC、NOx and NMHC were 1.571, 0.124, 0.192, 0.123g/km respectively, which were more than 1.2~2.8 times of the limit values of China five. The four pollutants emissions had an exponential growth with the mileage increasing and correlation coefficients of R2 were 0.6683、0.6306、0.7309 and 0.641 respectively. Excess limit values were initially observed on the taxis with the mileage between 200thousand and 300 thousand. The pollutant emission deteriorated sharply after the taxis had a mileage of over 300thousand and NOx had the highest emission which was almost 16 times of limit value. The disabled catalyst and air leak of emission system seemed to be the main reasons based on the analysis of noble metals content in the 3kinds of catalysts. The 35 taxis with the new replaced catalysts all met the emission requirement of China Five Stage. It indicated that pollutants emission reduction could be achieved obviously by replacing disabled catalysts of high mileage taxis in Beijing. The deterioration coefficients of different high mileage taxis were calculated.
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WEN Yi, LIU Jun-nv, LIU Xian, YANG Zheng-jun. Emission deterioration characteristics of the China five stage taxis in Beijing. CHINA ENVIRONMENTAL SCIENCECE, 2017, 37(12): 4487-4492.
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