London

Gasoline Partially Premixed Combustion (PPC) was investigated in a single cylinder optical diesel engine. The PPC operation was achieved with a combination of high dilution and higher intake charge temperature at part-load conditions using Primary Reference Fuel (PRF). The relative air/fuel ratio (λ) was set to 2.3 and the EGR rate at 22%. Split injections of three fuel distribution strategies (50:50, 70:30 and 30:70) were studied. In addition, the effect of injection pressure (900 and 1200 bar) was investigated for each injection timing. The emission and performance of the gasoline PPC operations were then compared with those of the baseline diesel combustion operation. Based on the thermodynamic analysis of the engine performance, detailed in-cylinder studies were carried out by means of optical techniques. The high speed imaging technique was employed to observe the fuel spray development and combustion processes. A simultaneous Mie-LIF technique was then developed and utilized for the visualization of fuel liquid and vapour formation. The experimental results demonstrated that better output performance can be obtained when the combustion phasing (CA50) was properly controlled by injection timings. Simultaneous reduction of NOx and soot emissions was achieved under gasoline PPC operation. Further reduction in soot emissions was achieved at the higher injection pressure of 1200 bar. However, excessive uHC emissions were noted during the gasoline PPC operations. The Mie-LIF images illustrated the faster fuel evaporation process and less luminous combustion of gasoline PPC than the diesel operation. In addition, more luminous combustion was observed at 900 bar injection pressure than 1200 bar injection pressure. I