Simulation And Experiment Of Diesel FPELG For The In-cylinder Combustion Processes

Free-piston Engine Linear Generator, or FPELG, is a new power system developed in the last ten years under the background of energy shortage and environmental pollution. It makes free piston engine and linear generator coupled as one. It can also provide clean power system solution for hybrid electric vehicle. Comparing with the combination of traditional crankshaft internal combustion engine and rotating generator, FPELG rejects crank train. It is valued by domestic and foreign researchers because of the performance advantages such as uncomplicated mechanism, high energy conversion efficiency, multi-fuel adaptability, high energy density and low NVH. Diesel FPELG has the potential advantages of high compression ratio and large output power, become the hot spot in the field of FPELG.This paper adopts a method of combining simulation and experiment for studying the heat release rate of free piston internal combustion engine. In the part of simulation research, this paper used piston dynamics and kinematic model to analyze the law of free piston and used this to analyze the differences of heat release simulation results between free piston engine and traditional engine. The zero dimensional model and the three-dimensional model coupling simulation were used to analyze the influence of the injection starting point, the injection law curve, the basic parameters of nozzle hole for the combustion of gas mixture in cylinder. In the part of experimental study, to build a diesel FPELG principle prototype experimental platform, focused on the process of the fuel supply system and load of the system, realized motor drive combustion condition and mode switching condition. Used the first law of thermodynamics, the heat release rate of the cylinder is calculated according to the pressure data and piston displacement data. The fitting of the dual-weber function is carried out. Then divided the combustion exothermic stage and analyzed the different heat release characteristics of FPELG from traditional engine. At last, the design of variable thrust experiments and variable injection position experiments were made to analyze the influence of the thrust and fuel injection location of the motor on the heat release of FPELG combustion.