Research On Integrated Scavenging And Optimization Of Free Piston Linear Generator

Free piston linear generator(FPLG)has the advantages of simple structure,high mechanical efficiency and good fuel adaptability,which is suitable to be used as extender of series hybrid vehicle.But because there is no limit of crank and connecting rod mechanism to make it run,its running stability is poor.At the same time,there is no closed scavenging box with FPLG,it often needs additional scavenging device,which is difficult to achieve engineering application.Based on the original single piston FPLG prototype,this paper studies the influence of air spring on the motion characteristics of the system.The results show that increasing the supercharging coefficient of air spring will increase the peak cylinder pressure and operating frequency of the engine,thus increasing the output power of the system.However,when the spring pressure is too large,the operating volatility of the system will increase.An integrated scavenging scheme is designed for the single piston FPLG structure,which greatly simplifies the overall structure.Experiments show that the scavenging pressure can reach 1.42 bar and the circulating air intake volume is 190.42 m L under the operating frequency of 15.58 hz.A one-dimensional simulation model of the system is built in Simulink,and the combustion module is calibrated according to the experimental data.In order to solve the problem of insufficient engine power,this paper puts forward the operation strategy of partial stroke power generation,analyzes the influence of different spring elastic coefficient and load on the system,the results show that increasing spring elastic coefficient will increase the operation frequency and speed,and shorten the displacement,so as to improve the power and system efficiency;the change of load has little influence on the frequency,but will affect the operation speed,stroke and system efficiency.The power cylinder 3-D model is built by using Converge CFD software,the air change process in the cylinder is studied,the influence of different operation parameters on the scavenging quality and scavenging efficiency is compared,and the optimization solution is proposed for the problem of low scavenging efficiency.The results show that increasing the scavenging pressure can improve the scavenging effect and the intake volume in the cylinder,and the actual scavenging efficiency will be lower if the pressure is too high;although the scavenging effect will be reduced if the frequency is increased,the scavenging efficiency will be improved because the gas disturbance in the cylinder is strengthened;shortening the stroke of the bottom dead point of scavenging can improve the actual scavenging effect while maintaining a good scavenging effect The scavenging efficiency can also reduce the friction loss of FPLG;shortening the intake time after the bottom dead center will not have a great impact on the scavenging effect,but it can improve the actual scavenging efficiency.