Gasoline Direct-Injection Engine Combustion and Emissions Measurements and Modelling

Abstract

Abstract

Experimental measurements of exhaust emissions and combustion pressure are presented for a piston-guided direct-injection spark-ignition engine over a wide range of injection timings and ignition timings. The measurements show that the engine can be operated satisfactorily in very lean conditions (λ = 4.0) at wide-open throttle. High hydrocarbon emissions are measured at late start-of-injection conditions and with late ignition. High emissions of nitrogen oxides (NO _x ) occur with early start of injection and with early ignition.

Modelling results show acceptable agreement with the measurements for the indicated mean effective pressure and show that high levels of NO _x are produced from the inhomogeneous zones that burn close to stoichiometric conditions. It is argued that early start of injection gives rise to high NO _x because of fuel mixing to conditions close to stoichiometric and burning early in the combustion process.