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

47Thermal efficiency (%)44434241403938RPM 1000 RPM 1500RPM 2000 RPM 2500RPM 30005 10 15 20 25 30 35 40Molar water injection -fuel ratio (Nw/Nf)FIGURE 4-26 Thermal efficiency- Molar water injection-fuel ratios withEngine speedAccording to Figure 4-25 and Figure 4-26, this results help to predict thelimitation of maximum performances to simulate a spark ignition engine variedengine speed with molar water injection-fuel ratio increasing. The indicated meaneffective pressure (IMEP) and thermal efficiency curves are almost the same for eachengine speed. However, it is not much difference in both from at 20 of molar waterinjection-fuel ratio, mass of water injection see Table 4-2. The both cases increasingwere approximately value of 50,000 Pa and 3% of IMEP and thermal efficiencyrespectively which only fluctuates slightly around this value.Theoretically, in actual engines or simulation model, it is clearly shown that asthe engine speed increases the engine performance parameters of the model increases.All of cases were assumed by using the equally mass of water injection. It follows asimilar trend to the performance curve while the molar water injection-fuel ratio( X ) Wincreases gradually. However, if a lot mass of water is injected, a bulk of waterin a cylinder will be a large amount and low temperature may absorb the energy fromthe gas burned and decrease its temperature. But at the high engine speed does notdifferent value, due to be the range of time in the piston cylinder less than low enginespeed, which gives the low energy transfer between water and gas burned. So, theenergy conversation to work in a cylinder will be less or almost equal value4.6 Two-Zone Thermodynamic Models of Water Injection StrokeThe change of parameters such as temperature, pressure and volume per 1 CAor the period of time are used in this study to indicate the change of the engines, if theengine having water injection system. This study will therefore focus on the two zonethermodynamics model of water injection mode which can be seen in section 3.3.Each simulation has different schematics of burned zone and water zone both basedon equally volume and pressure system with the different molar water injection-fuelratios and using 3 modes for simulation with variation of compression ratio (8-12),equivalence ratio (0.8-1.2) and engine speed (1000-2500 RPM), respectively.