چكيده به لاتين
Given the growing need to properly use energy resources and increase the price of carriers, it is necessary to study and feasibility of using new designs that reduce fuel consumption in cars. One of the designs used in new cars is the use of direct fuel injection for internal combustion engines, which reduces the fuel consumption of internal combustion engines in urban driving cycles. Also, due to the increasing reduction of fossil fuel sources, the use of alternative fuels in order to achieve the optimal combined fuel is necessary. Natural gas as a fuel that can be obtained from other sources and also has a lower cost, can be a good choice. In this research, a combination of direct natural gas injection and gasoline port injection has been used. Direct injection of natural gas prevents a reduction in volumetric efficiency compared to port injection of natural gas. In this study, an attempt was made to investigate the effect of variables on engine performance by numerical simulation using Converge software. Because for some of these changes, experimental testing is difficult. First, the simulation results were validated to provide the reliability of other results for discussion and comparison. The results showed that with increasing the percentage of natural gas in the mixture, the amount of carbon monoxide, carbon dioxide and nitrogen oxides were significantly reduced. For example, for engines with a compression ratio of 10.5, the amount of carbon monoxide and carbon dioxide for 100% CNG mode decreased by 29.3% and 23.5% compare pure gasoline mode, respectively. Also, due to the high knock resistance of natural gas, with increasing the percentage of natural gas in the fuel mixture, the probability of knock occurs sharply decreased. this advantage manifests itself in full load mode and a higher compression ratio. For example, for the engine with a compression ratio of 12.5, the RI value decreased by 56%, 66%, 74.6% and 88.6% for the 25%, 50%, 75% and 100% CNG modes, respectively.
