Effect of water injection on the performance of LPG fuelled spark ignition engine

The effect of water injection on LPG fuelled SI engine performance, fuel economy, combustion characteristics, and exhaust gas emissions were investigated in this thesis. In addition, an exergy and energy analysis based on experimental results was also investigated.Investigation presented in this thesis was realized in two main stages. In the first stage; an experimental set up was designed and constructed. A data acquisition system composed of all of data acquisition, accumulation, and processing components was installed to carry a fully computer aided experimental study from the test engine. In the second stage: an experimental study was conducted to determine the effects of the water injection.Experimental results showed that several combustion variables were affected by water injection. Results showed that, at mw/mf=05, energy analysis indicated that only 37.9% of the fuel energy could be utilized as an indicated power, where 62.1% of fuel energy was not available for conversion to useful work. Exergy analysis showed that 52.1% of fuel energy could be utilized as useful work (35.7% as an indicated power, 12% from the exhaust and only 4.4% from the cooling water) and the available energy unaccounted for represented 47.9% of the total available energy for the same condition. It was also found that water injection increased the combustion irreversibility significantly. Water addition provided a 35% reduction in peak NOx emissions without any significant change in CO and HC emissions. In addition, greater ignition advance was obtained. The average increase in the brake thermal efficiency for a water to fuel mass ratio of 0.5 was approximately 2.7% over the use of LPG alone.Keywords: Internal Combustion Engine, Water injection, Data Acquisition, LPG, Exergy, Thermal balance