I would like to know how the pressure curves and emissions behave when fuel injection timing in a port injected gasoline engine is varied from suction TDC to compression TDC. Coefficient of variation in pressure fluctuation reduces or increases when fuel injection is timed at compression TDC. The port fuel injected is gasoline in the gasoline engine.
Hello,
I'm not sure to understand what is precisely what you are looking for when varying injection timing. What I can tell is that phsaing injection in port injected engines is a capital factor on combustion efficiency and pollutant emissions, not only in steady functionning but moreover on transients. Most of injectors and injection systems in low-pressure port injection engines do not provide enough atomization for an effective vaporization of fuel. So, the major part of it (up to 90% in cold conditions and 70% otherwise) deposits in pipe and valves. Injection prior to valve opening is therefore the best solution in terms of combustion and pollution (time is longer and contact with hot surfaces enhances desposited film evaporation). Injection during intake stroke, while valves are open allows large droplets to enter the combustion chamber whom do not burn and cause increase of HC and soot. Cylinder pressure increases when combustion is optimzed. If injection is made while valves are open, a compromize between aerodynamics and injection/valve timing must be found to carry a correct injection and is dependent on engine speed (aerodynamic behaviour) and charge (amount of fuel to be burnt). Some experiments can be found on :
L Le Moyne, F Maroteaux (1998) Air-fuel flow modeling applied to the reduction of air-fuel ratio excursions during transients on port injected spark ignition engines Journal of engines - SAE Transactions 1997 106: 3. 728-735.
L LeMoyne, F Maroteaux, P Guibert, M Murat (1997) Model and measure of flows at the intake of engines JOURNAL DE PHYSIQUE III 7: 10. 1927-1940 OCT.
hope it is of use for you
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