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

39Thermal efficiency (%)434241403938373635Normal1.0Nw/Nf2Nw/Nf0.5Nw/Nf1.5Nw/Nf1000 1500 2000 2500 3000RPMFIGURE 4-14 Thermal Efficiency-RPM with the molar water injection -fuel ratioAccording to Figure 4-13 and Figure 4-14, this results help to predict the bestengine speed to simulate a spark ignition engine with water injection. The indicatedmean effective pressure (IMEP) and thermal efficiency rises as the molar waterinjection-fuel ratio increases. However it is not much difference in both from thenormal case. The both cases increasing was approximately value of 30,000 Pa and 1%of IMEP and thermal efficiency respectively which only fluctuates slightly aroundthis value for all of engine speed increases and curves almost the same for each themolar water injection-fuel ratio increases which were compared with normal case.Theoretically, in actual engines or simulation model, it is clearly shown that asthe engine speed increases the engine performance parameters of the model increases.As the engine speed increases, the turbulence inside the cylinder increases, leading toincrease the flame front speed [7]. In this case, 0.5 value of the molar water injectionfuelratio may be the optimizing value for this simulation which gives IMEP and thethermal efficiency that does not look different much for all of equivalence ratio caseand it follows a similar trend to the spark ignition engine.4.4 Performances of Water injection models varied Water injection durationangleIn this section, the schematic from Figure 4-4 were used to analytically discussresults of pressure mixing and temperature mixing under effects of different waterinjection duration angle ( θ W) .Which are divided into 3 modes for simulation withvariation of compression ratio range (8-12), equivalence ratio range (0.8-1.2) and enginespeed range (1000-2500 RPM) respectively at the different molar water injection-fuelratio ( X ) W. These will be described as following.4.4.1 Performance of water injection model at different compression ratio ( r)This simulation test was run at 2,000 rpm, equivalence ratio of 0.8 and waterinjection-fuel ratio ( XW) of 10 with the different water injection duration angle ( θW)while using different compression ratios ( r), varied from 8, 9, 10, 11 and 12,respectively.