Study On Monitoring Three-Way Catalyst Converter Efficiency Based On Exotherm

Despite of the fact that exhaust emission regulations for new cars have becomeincreasingly stringent and automobile exhaust controlling technology is quite advanced;real-world emission levels of the average car have been remained higher than anticipated.This is attributed mainly deterioration of some controlling emission parts with poormaintenance of in-use cars.The main way of identifying these vehicles is through aninspection and maintenance (I/M) program.However,I/M programs rely on periodicinspections,between the inspections,the emissions couldn't be monitored.The introductionof on-board diagnostics (OBD) resolves the inherent difficulty of I/M programs.Withactualizing of theâ…¢/V emission regulars of China step by step,the developing of OBDtechnology is going in our country widely.Now most products of OBD are made by abroadenterprise.Therefore,the study on OBD has important realistic significance.The monitoring methods and technologies for three-way catalyst converter (TWCC)Efficiency are core techniques of OBD system.Now the main methodologies are to indirectlyassess catalyst performance by existing sensors.This thesis completes the study onmonitoring three-way catalyst converter efficiency based on catalyst exotherm,afteranalyzing the shortcoming of the method based OSC of TWCC,by applying analyzingtheoretically and modeling mathematically and experimentation and article nerve net (ANN)etc.The conclusions of the paper have some significance theoretically and useful forengineering reference to decrease the emission of vehicle in-used.The following are themostly contents and conclusions of the study.(1) The reason for invalidation and primary indexes of TWCC are analyzed.Theaverage requirements for OBD are discussed.By comparing between the methods for TWCCefficiency monitoring,especially OSC,Component-sensors and thermal methods,it is putforward that processing method for TWCC efficiency monitoring based on catalyst exothermis feasible and valuable.(2) The process of TWCC multiphase catalytic dynamics,transfer-mass and transfer-heat,stream distributing and the oxygen storage model are analyzed.Through theintroduction of the advance of TWCC's reaction mechanism,the process of TWCC ispredigested to five reaction formulas From the point of hydrodynamics transfer-heat andmultiphase catalytic exotherm,according to gas phase and solid phase mass conservation andenergy conservation within TWCC,the thesis develops TWCC single-path transfer-mass andtransfer-heat conservation models,and then develops transfer-mass and transfer-heatconservation models for monolithic catalytic converter.So the controlling equations are givenfor monitoring three-way catalyst converter efficiency.By making the equationsdimensionless,the TWCC single path and monolithic monitoring models are developed,andanalyzes the application of the monitoring models.Lastly,the relation between out-inlettemperature and total converter efficiency of the TWCC is established on the stable conditionsof engine.(3) The concept of 'total converter efficiency' is put forward and quantified in theengine test-bed.The influence on converter efficiency with engine's rotating speed,load isprobed into,and the change rule of inlet-outlet temperature difference of TWCC with engine'srotating speed,load is analyzed.Lastly,with temperature difference coefficient,the modelbased thermal is validated.On driving mode conditions with dynamometer,the test furtheranalyzes the velocity of the test car influences the total efficiency and inlet-outlet temperaturedifference of TWCC.The relation between total converter efficiency of the TWCC and someparameters of engine is nonlinear.(4) The thesis uses BP ANN to develop the TWCC efficiency monitoring model toevaluate the TWCC based on the traditional model analysis and the relation between TWCCefficiency and some input parameters.The BP ANN model's capacity of learning andprolongation is validated.The results show that the developed BP ANN model can forecastthe level of TWCC efficiency without mathematics model.The BP ANN offers a new way tomonitor TWCC.