Research On Alternative Catalytic Converters Based On Bench Evaluation

With the increasing emphasis on the environmental pollution,the control of vehicle emissions has become an issue that cannot be neglected in formulating development policies in our country.Nowadays,since energy conservation and emission reduction have become the major themes in the development of internal combustion engine,how to control the emissions of vehicles effectively has become the research focus of countries,enterprises,research institutes and institutions.Vehicle emission control involves both new vehicle certification and supervision on in-use vehicle.In view of the large quantity and the high emission of in-use vehicle,the control of vehicle emissions affects the overall vehicle emission level.In order to meet the increasingly stringent emission regulations,TWC(Three Way Catalyst)has become an indispensable key component of the vehicle emission control system.The working status and efficiency of TWC somehow determine the emission level of vehicles in its full useful life.It is of great significance to replace failed and damaged catalytic converters to ensure the emissions of in-use vehicle meeting the regulatory requirements throughout full useful life.The characteristics of vehicle emissions in different stages based on the vehicle emission test cycle are analyzed.On this basis,the differences in the performance of catalytic converters under air/fuel ratio oscillate,the light-off performance,space velocity as well as the oxygen storage capacity of catalytic converters are explored,respectively.The influence of air-fuel ratio oscillate process on the performance of three-way catalytic converter with different oscillate amplitude,frequency and mean value are compared.The results show that compared with the air-fuel ratio at the inlet of the catalyst,the air-fuel ratio at the outlet of the catalyst is more consistent with the change of its working performance.With the oscillation of air-fuel ratio,the performance of catalytic deteriorates with the increase of the amplitude,and improves with the increase of the frequency.While the mean value of air-fuel ratio oscillates is lean,the conversion of CO and HC is high,but the conversion of NOx deteriorated.While the mean value of air-fuel ratio oscillates is rich,the catalyst has a better performance.The air-fuel ratio oscillates of high frequency,low amplitude and a mean value slightly smaller than 1 is beneficial to the performance of three-way catalytic converter.This paper analyzes the light-off performance,space velocity and oxygen storage capacity of catalyst.The results shows that compared with the inlet temperature of the catalyst,the outlet temperature can better reflect the change of average temperature of the catalyst substrate,so as to measure the light-off performance of the catalyst more accurately.Light-off performance improves with the increasing of cell density,while the effect of which reduces gradually.Light-off performance shows little difference under different wall thickness,it only slightly deteriorated with the increase of wall thickness.Light-off performance deteriorates as the space velocity increases,but the effect of which decreases because of the decreasing of the mean substrate temperature.The catalyst with larger cell density and smaller wall thickness has better adaptability to the variation of space velocity.Under the rapid and disorderly change of air-fuel ratio,the increase of oxygen storage capacity is in favor of the stable performance of catalytic converter.Under the regular change of air-fuel ratio,the influence of the difference of oxygen storage capacity on the performance of catalyst gradually weakened.