Özet:

Mixture formation in port fuel spark ignition engines is one of the most im-portant parameters, which affect combustion and emissions. In this study, the ef-fects of different injection start timings and some other port fuel injection (PFI) parameters on the performance and emissions of a water cooled and single cylin-der spark ignition engine were examined experimentally. The experiments were performed at different engine speeds (1200 and 1500 rpm for effect of injection pressure and 1500 rpm for changing injection timings) and different engine loads (3 bar and 5 bar for injection pressure and 1 bar and 5 bar for start of injection). The start of injection was chosen according to intake pressure measurements. The experiment results showed that brake specific fuel consumption (BSFC) and total hydrocarbon (THC) emissions are increased by the increase of the injection pressure. Because with the increase of injection pressure, the fuel can reach the intake manifold wall or intake valve. Therefore, the fuel enters the cylinder as a droplet. Different start of injection experiments showed that injection times have an effect on emissions and performance. The minimum brake specific fuel con-sumption and THC values were obtained at -243 °CA value of injection start. The twice injection in one cycle increased brake specific fuel consumption and THC emissions.

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