| With the increase in the number of motor vehicles around the world,the problems caused by exhaust emissions are becoming more and more serious and threatening environmental safety.In order to protect the ecological environment,each country has implemented a series of increasingly strict emission regulations.Since the emission limit regulations for soot particles are getting smaller and smaller,it is imperative to reduce the emissions of nitrogen oxides and solid particulates from diesel exhaust.Diesel engine and auto parts manufacturers have introduced their own exhaust gas after treatment systems to meet emission regulations.In order to meet the national six-stage emission standards for PM and NO_X,two technical routes of“EGR+DOC+DPF+SCR”and“DOC+DPF+efficient SCR”are mainly used in exhaust gas after-treatment,all of which require DPF active regeneration process,of which“DOC+DPF”is commonly used.The active regeneration mode,while the temperature of the DOC needs to reach above 500°C during the combustion of the PM,but the temperature of the exhaust pipe is only 300°C,so it is necessary to increase the HC injection system at the DOC front end to ignite the emissions,so that the temperature of the DOC reaches Above 500°C.The HC injection system is an important part of DPF active regeneration process.The mainstream HC injection system technology in the market is mainly in the hands of several foreign companies.It is of great significance to develop HC injection system by itself.By comparing and analyzing the detailed structure and working principle of several HC injection systems abroad,summarize the working principle of several HC injection systems and the advantages and disadvantages of the structure,and a HC injection system with light weight,high precision and adapting to the requirements of the Chinese market is designed.The key technologies for HC injection system design are system integration and light weight,metering valve metering injection accuracy,nozzle sealing and atomization.In the process of designing the HC injection system,the overall structure and key components of the HC injection system are analyzed.When implementing system integration and light weight,fully consider the volume,installation method and working principle of each component,and reasonably arrange the position and occupied space of each component.The metering valve is the main component of the metering,and the accuracy of the metering quantity is related to the throttle area of the metering valve and the pressure difference between the inlet and outlet.Design calculations and physical modeling of metering valves and nozzles are first performed.The AMEsim software was then used to analyze the effect of the orifice diameter of the metering valve and the nozzle back pressure on the injection volume.Finally,the relationship between the flow force curve and the duty cycle of the metering valve and mass flow is verified by simulation and experiment.The nozzle is the main component to achieve sealing and atomization.Firstly,according to the main design parameters,select the appropriate sealing form and calculate the sealing force to determine the structure of the seal.Then use Fluent software to analyze the pressure,velocity and atomization result of the nozzle seal.Set up a comprehensive performance test bench to test the flow characteristics and atomization effect of the HC injection system in actual work,and analyze the simulation and experimental results.Through simulation and experiment,the flow rate and pressure of the HC injection system are basically proportional.The duty cycle of the metering valve and the mass flow have a good linear relationship.The particle diameter after atomization meets the design requirements. |
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