analysis of water injection into high-temperature mixture of ...

38According to Figure 4-11 and Figure 4-12, this results help to predict the bestmolar water injection -fuel ratio to simulate a spark ignition engine with waterinjection. The indicated mean effective pressure (IMEP) and thermal efficiency risesas the molar water injection-fuel ratio increases. However it is not much difference inthe both from the normal case. The both cases increasing was approximately value25,000 Pa and 1% of IMEP and thermal efficiency respectively which only fluctuateslightly around this value for all of equivalence ratio case. And these curves arealmost the same for each the molar water injection-fuel ratio case which werecompared with normal case. Indicated efficiency increase with increasingcompression ratio, is maximized by lean combustion, and is practically independentof the initial temperature and initial pressure.Theoretically, in actual engines or simulation, maximum efficiency occurs atstoichiometric or slightly lean, excessive dilution of the change with air degrades thecombustion [6]. However, it depends on application any types of fuels provided [6].In this case, a 0.8 value of equivalence ratio was chosen for gasoline that may beoptimized value for this simulation which gives IMEP and the thermal efficiency thatdoes not look different much for all of equivalence ratio case.4.3.3 Performance of the water injection model at different engine speeds (RPM)This simulation test was run at 2,000 rpm, equivalence ratio of 0.8 and waterinjection duration angle ( θW) of 10 CA with the different molar water injection-fuelratio ( XW) while using different engine speed, varied from 1000, 1500, 2000, 2500and 3000, respectively.IMEP (MPa)1.0501.0251.0000.9750.9500.9250.9000.8750.850Normal1.0Nw/Nf2Nw/Nf0.5Nw/Nf1.5Nw/Nf1000 1500 2000 2500 3000RPMFIGURE 4-13 IMEP-RPM with the molar water injection-fuel ratio