The Study On Catalyst Control For Exhaust Emissions Reduction

At present,the air-fuel ratio closed-loop control technology,which is composed of the electronical control fuel injection system and catalytic converters,has become the main vehicle emissions control measure.The control system could get excellent exhaust gas purification properties,meanwhile,the fuel consumption and operating characteristics are guaranteed.However,accurate air-fuel ratio control can only be completed at an ideal air-fuel ratio in the traditional control system.In other regions, the control results can only be based on open-loop control to amend the injection.In order to achieve optimal fuel consumption,emissions and operation performance,it is indispensable that a new type control device is proposed,which can control air-fuel ratio within the whole operation.In the first part,the harmfulness and influence factors of vehicle exhaust gas emissions are introduced,the impact and the relationship between air-fuel ratio and CO,HC,NOx are emphatically analyzed.It can be concluded that maintaining the theoretical air-fuel ratio value is very important.Secondly the most critical component—three-way catalytic converters on the emissions control system is presentd in detail,including its composition,classification and performance parameters.After that three-way catalytic converters' chemical mechanism,oxygen storage effect,and air-fuel ratio control are mentioned.Then oxygen sensors are given a comprehensive introduction,which play an important role in the emission control system.And a wide scope of air-fuel ratio sensors that can detect the entire air-fuel ratio scope of the emissions control system are proposed;a comprehensive comparison between air-fuel ratio oxygen sensors and conventional sensors is performed,including the structure of sensors,detecting principle,output characteristics,work characteristics,and practical application of oxygen sensors.Finally,a simulation design of the catalytic control devices is carried out by using robust control toolbox of MATLAB6.X.including the mathematical model of three-way catalytic converters,the delayed air-fuel ratio sensor model and proportional integral controller design,Conclusion of the new control device results can be achieved through excess air ratio,HC and NOx conversion efficiency,and air-fuel ratio deviation.Moreover the experiment proves the new emission control device superiority through detecting catalyst aging and exhaust emissions value.In a word,the research results have practical value and significance on automobile exhaust emissions control.