Experimental And Simulation Research On Integrated Aftertreatment System Of Heavy Duty Diesel Engine

With the strengthening of people's awareness of environmental protection and the rapid increase in vehicle ownership,in recent years,the world has increasingly stringent emissions regulations.The European VI(or China 6)emission stage,the mainstream trend of emission control technologies of heavy duty diesel engine is coupled using various aftertreatment technology integrated system for aftertreatment of exhaust HC CO,NOx,PM,and other comprehensive treatment to meet the requirements of stringent emission regulations.Compared with the diesel engine techniques of the China 4 and China 5,the integrated aftertreatment system can effectively reduce the exhaust NOx and PM emissions,thus reducing engine emissions control requirements,so that the engine has better power and economy.However,there is many factors affecting the performance of each aftertreatment technique and the mutual interaction between techniques because of the multiple usage of integrated aftertreatment in the integrated aftertreatment system.Hence,the difficulty of the development and matching of the integrated postprcessing system become bigger.This thesis,which is based on a horizontal project cooperated with a domestic engine manufacturer,applies a method of including experimental investigations and numerical simulations to investigate the factors that influence the integration aftertreatment system of heavy-duty diesel,the numerical simulations and the Catalyst optimization.Firstly,the catalytic performance of the catalysts under different conditions were investigated:(1)The oxidation properties of DOC catalyst with different length and different amounts of coat were tested.(2)The oxidation properties of CDPF catalyst with different Pt:Pd coating schemes were tested.(3)The NOx catalytic efficiency of SCR catalyst at different space velocities and temperature was tested.The NOx catalytic efficiency of SCR catalyst under different ratio of ammonia and nitrogen and different temperatures was tested.As a result of the above tests,the application schemes of the integrated aftertreatment system are determined.(4)The sulfur resistance of the integrated aftertreatment system is tested,and the results show that the system has favorable capability of sulfur resistance.According to the characteristics of the integrated after treatment system,the system is simplified and assumed to established a numerical model including the model of NO oxidation and NOx reduction reaction and catalytic decomposition of urea water solution.Then,the model is calibrated by using the test datas from the second chapter and the chemical reaction activation energy and pre-exponential factor value are derived.Finally,we calculate the system optimally,(1)Optimizing the nozzle distance d with SCR catalyst for entry.The results showed that:d=750 mm is the best installation position of the nozzle.Aqueous urea solutions is fully decomposed at this time and ammonia into the SCR catalyst with maximum concentration and uniform state.(2)Optimizing the DOC and the length of the SCR catalyst.Compared with the preliminary plan,the new plan is less catalyst usage and more compact structure.To sum up,the experimental research and simulation of heavy duty diesel engine integrated aftertreatment system are carried out.The results can provide the design basis and theoretical guidance for the integrated aftertreatment system of heavy duty diesel engine.