The Effects of Engine Speed and Injection Pressure Transients on Gasoline Direct Injection Engine Cold Start

Results are presented from an experimental study of the effects of engine speed and injection pressure transients on the cold start performance of a gasoline direct injection engine operating on iso-octane. The experiments are performed in an optically-accessible single-cylinder research engine modified for gasoline direct injection operation. In order to isolate the effects of the engine speed and injection pressure transients, three different cold start simulations are used. In the first cold start simulation the engine speed and injection pressure are constant. In the second cold start simulation the injection pressure is constant while the engine speed transient of an actual cold start is simulated. In the third cold start simulation both the engine speed and the injection pressure transients of an actual cold start are simulated. Performance is characterized during each of the 50-cycle cold start simulations by measurements of the in-cylinder pressure and engine-out hydrocarbon emissions. In addition, the in-cylinder spray and fuel-air mixing processes are characterized on a cycle-by-cycle basis using simultaneous planar laser induced fluorescence and two-dimensional Mie scattering. The results are used to gain a better understanding of the effects of engine speed and injection pressure transients on gasoline direct injection engine cold start.