In-cylinder simulation of hydraulic free-piston diesel engine

Through the calculation of indicator diagram and CFD numerical simulation, in order to study the in-cylinder combustion process of hydraulic free-piston engine, the numerical simulation iteration method is proposed. Thus the control parameters and the interactive relationship between in-cylinder coupling parameters in the working process can be analyzed. Results show that compared with the traditional crank-shaft engine, when the injection timing or the injection location is the same, the mixture prepared during ignition delay period is different. The ignition delay period of HFPDE is shorter, which leads to the difference in premixed combustion heat release rate. Rapid heat release causes fast piston movement, thus resulting in different in-cylinder temperature distribution. Lower temperature causes NO_x to concentrate on TDC. NO_x is hardly produced after combustion. On the other hand, the influence of inverse extrusion flow on in-cylinder air-fuel ratio is great, soot is mainly formed near the cylinder liner, and the rapid decline of temperature makes less contribution to soot distribution.