Improving the Ecological Performance of Free-Piston Gas Generator by Air-Gas Mixture Self-Ignition

The paper considers the implementation of combustion of premixed mixture with compression ignition (HCCI-process) in a free-piston gas generator designed according to a scheme with oppositely moving pistons, with two compressor and buffer chambers. The processes of gas exchange and combustion of an air-gas mixture are considered in a three-dimensional formulation, considering the dynamics of pistons freely moving under the action of inertia, friction and gas forces. The mathematical model is based on the system of equations of energy, motion (Navier-Stokes), diffusion and continuity, and supplemented with ignition and combustion models (Extended Coherent Flame Model, ECFM) and heat transfer in near-wall regions. In the first cycles, the operation of free-piston gas generator with ignition of the mixture using spark plugs is considered; later, the possibility of implementing a cycle with spark-assisted compression ignition or compression ignition without the use of spark plugs is analyzed.