The effect of adding NG to LPG on a spark ignition engine

LPG and natural gas are both available in large quantities in Iraq, but unfortunately, they are not used as fuel for internal combustion engines. The current study aims to evaluate the possibility of operating the spark ignition engines by enriching the liquefied petroleum gas with volumetric fractions of natural gas, such as 30, 50, 70 and 80%. The influence of some design factors such as compression ratio and some operational factors such as the equivalent ratio, spark timing, and engine speed have been studied in detail. The study showed that the highest useful pressure of LPG is 10.5: 1 while natural gas was 13: 1. When adding natural gas to LPG, the compression ratio can be increased to a certain limit to be the highest increase in the mixing ratio of 80% with a compression ratio of 11.6: 1. The natural gas has a low flame propagation speed so the spark timing should be provided when added to the LPG. The addition of this addition reduces the induced power at a low speed due to this natural gas characteristic. Natural gas reduces the engine's output power by reducing the engine's volumetric efficiency by entering the combustion chamber with its gas phase. Keywords—LPG, NG, compression ratio, equivalence ratio, spark timing.