Research On Control Valve Performance Of Dimethyl Ether Premixed Combustion System

With the rapid development of automobile industry,energy shortage and environment pollution problems got people ' s more attention in recent years.It is necessary to look for new clean alternative fuel for engine and optimize combustion efficiency.Dimethyl ether has great potential as diesel engine clean alternative fuel since it has high octane and no soot emissions.Dimethyl ether(DME)premixed charge compression ignition(PCCI)which is similar to homogeneous charge compression ignition(HCCI)combustion mode received high attention of scholars because its good operation.Control valve which located in two combustion chamber channel of DME engine is the key influence factor to DME PCCI mode.So the design of the control valve drive model and the exploration of control valve dynamic characteristics are very important.First,the electro-hydraulic control system is proposed in this paper based on control valve operating characteristics.The composition structure of electro-hydraulic control system is introduced,the specific work processes of control system in the dimethyl ether PCCI combustion mode is illustrated.Mathematical model is established and the main influencing parameters of control valve dynamic characteristics are analyzed.The control valve basic dynamic characteristic requirements are analyzed according to actual work requirements of DME engine.Second,according to the working principle of electro-hydraulic control system,the electro-hydraulic control system simulation model is built by AMESim software.The influence rules of hydraulic oil supply pressure,hydraulic piston diameter,valve mass,spring stiffness and line length on control valve dynamic characteristics are analyzed,the control valve timing and lift variable control characteristics are revealed.The results have shown that the peak values of control valve lift and speed enlarge with the increase of hydraulic oil supply pressure and hydraulic piston diameter,the control valve oscillation frequency at the maximum lift is affected obviously by hydraulic piston diameter.Valve mass has a little influence on the peak values of control valve lift and speed,but it has great effect on the amplitude of the control valve.The maximum lift will decrease with the increase of spring stiffness value,and the closing time is also shorter.Line length has a little influence on dynamic characteristics of control valve.At last,aiming at control valve seat impact problem,the strategy of damper orifices hydraulic brake and closed-loop control are adopted for optimization design.With the help of genetic algorithm,suitable PID control parameters which are applied to closed-loop control simulation model are obtained by AMESim optimized design function.The results have shown that control valve seat speed decreased from about 2m/s to 0.35 m/s after taking strategy of damper orifices hydraulic brake,and the speed can meet the requirements of the valve seat speed well,so as to realize the flexible control of the control valve seat speed.