Effects of Injection Timing on the Conditions at Top Dead Center for Direct Injected HCCI

摘要: The homogeneous charge compression ignition (HCCI) concept has been acknowledged as a potential combustion for engines, due to low NOx and soot emissions high efficiency, especially at part-load. Early direct-injection (DI) during the stroke is an option when Diesel fuel used in HCCI. This implies that risk wall impingement increases, decreasing in-cylinder density. sprays be well dispersed order avoid impingement. Specially designed impinging nozzles providing collision of vicinity orifice exits have experimentally verified yield desired benefits HCCI under various conditions. purpose this work use Computational Fluid Dynamics (CFD) tool simulate evaluate non-impinging with respect mixture formation direct-injected Three different are considered: one two 30 60 degree angle respectively. Lagrangian CFD simulations using traditional model O’Rourke not sufficient obtain correct spray properties sprays. proposes enhanced model, which extension frequency, post collisional velocities induced break-up. referred EORIS (Enhanced Impinging Sprays). initial drop size distribution break-up time constant standard Wave calibrated calculated (piston liner) compared smoke, HC CO function injection timing. A set parameters were selected further evaluation. These applied low- load able predict agreement experimental measurements efficiency smoke conditions investigated nozzles. benefit can formation, there no need additional calibration when, instance, timing or nozzle geometry changed. In general, experiments indicate recommended early stroke. shorter penetration leads reduced are, however, beneficial later During these more stratified some poor quality achieved.