CFD MODELING OF DIESEL OIL AND DME PERFORMANCE IN A TWO-STROKE FREE PISTON ENGINE

This paper presents the CFD KIVA3V, rel. 2 model and numericalresults of combustion process simulations in a two-stroke, uniflowscavenging dual free piston engine, FPE, designed for electricity generation.Two fuels, diesel oil and dimethyl ether (DME), were studiedin order to achieve HCCI-like combustion. Limited size reactionmechanisms were constructed and used in the modeling. The dieseloil surrogate mechanism consisting of a mixture of n-heptane andtoluene includes 70 species participating in 305 reactions, whereasthe mechanism for DME consists of 43 species participating in 211reactions. The combustion development has been simulated in aFPE prototype geometry. It is illustrated that by varying the directinjection timings, a comparably efficient, low-emission operationhas been achieved for both fuels. Specific difficulties when usingslowly vaporizing diesel oil and rapidly vaporizing DME are outlined.