The output performance of the 25% gasoline-75% NG combination mode and its ‎comparison with NG mode

Population growth and industrialization have worsened environmental pollution. The share of passenger cars in the carbon dioxide produced by the transportation sector is about 40%, and considering that the type of fuel has a significant effect on the production of this greenhouse gas, researchers are trying to replace natural gas with gasoline. Natural gas is one of the available and cheap fuels, especially in countries with abundant natural gas resources. However, using gasoline and natural gas alone has advantages and disadvantages in terms of thermodynamics, pollution, and economy. Therefore it is difficult to prefer one over the other. Thus, by designing spark-ignition engines that burn with gasoline and natural gas combination, the disadvantages of using each of these fuels individually can be reduced and the appropriate conditions can be achieved in terms of engine performance and emission level. In this work, the experimental results of a single-cylinder research engine in two modes of 25% gasoline-75% natural gas combination and single-natural gas combustion under stoichiometric conditions, full load, identical compression ratio, and engine speed have been extracted, compared, and analyzed. The results showed that the optimum spark advance of the combination fuel mode was less than that of the gas fuel mode, and the maximum output torque and volumetric efficiency of the combination fuel mode were about 5.5% and 1.7% higher than the gas fuel mode, respectively. It was also observed that in optimum spark advances, the brake fuel conversion efficiency of the combination mode was about 6.5% higher than the value corresponding to the natural gas mode. In addition, it was observed that the temperature of the exhaust gases of the combination mode was higher than that of the natural gas mode at the optimum spark advance.