Toxicity of exhaust gases in gasoline engines powered with compressed natural gas and gasoline

The need to reduce environmental stress caused by active use of vehicles in large cities calls for reducing the toxicity of exhaust gases emitted by gasoline engines with spark ignition. The research aimed to find ways to reduce the toxicity of exhaust gases emitted by spark-ignition engines. The studies were carried out on a single-cylinder UIT-85 simulating the working process under maximum load and on a VAZ-2111 engine in idle mode. These modes have the greatest impact on the toxicity of a gasoline engine. Experimental studies on the VAZ-2111 engine were conducted at a standard compression ratio of 9.8 and at a reduced compression ratio of 7.5 using a special four-millimeter-thick aluminum plate. During the experimental studies, we recorded the pressure in the engine cylinder, the electrical conductivity of the flame in the zones of ionization sensors, as well as the consumption of fuel and air at the inlet and the toxicity characteristics of the exhaust gases. Gasoline and compressed natural gas were used as fuel. To assess the potential for reducing toxicity by intensifying the combustion process in VAZ-2111 engine, we used a hydrogen additive in the amount of 4 % (0.02 kg / h) and 6 % (0.03 kg / h) of the fuel mass. When studying UIT-85, we used a 5 % hydrogen additive for gasoline and a 5, 10, 15 % hydrogen additive for compressed natural gas. It was shown that natural gas can reduce the toxicity of exhaust gases, reducing the content of nitrogen oxides, hydrocarbons, and carbon monoxide. The engine performance indicators remain the same, if the optimal ignition dwell angles are selected. For efficient combustion at idle mode, methods for intensifying the combustion process have to be applied. We showed an example of effective impact of hydrogen additive in amount of 4 % of the fuel mass. At the same time, the effect of hydrogen is more effective when engines are powered with natural gas.