A three-dimensional computational fluid dynamics(CFD) simulation model of a two-stroke semi-direct injection hydraulic free-piston engine(HFPE) was built by the CONVERGE. The effects of the injection angle

fuel injection timing

chamfer of cylinder head

intake pressure on fuel capture and mixture formation were studied. The results show that as the injection timing is delayed

the fuel capture rate and evaporation time increase. The fuel capture rate increases with the increase of injection angle

while the evaporation time decreases first and then increases as the injection angle increases. With the appropriate injection angle and injection timing

the fuel capture rate can reach 99% or more. The larger the cylinder head chamfer

the faster the fuel evaporates and the more uniformly the fuel distributes in the cylinder. As the intake pressure increases

the fuel capture rate and the evaporation time decrease. Under the same fuel capture rate

more uniform mixture can be obtained by changing the intake pressure than by changing the fuel injection parameters. The minimum unevenness of the mixture can reach 0.5.