ENVIRONMENTAL SAFETY OF POWER PLANTS: DUAL-FUEL AND GAS ENGINES

Abstract

The subject of this study is internal combustion engines capable of using gaseous fuels-gas and dual-fuel engines. The main technologies of using natural gas in piston engines from the standpoint of ensuring the highest energy efficiency and environmental safety are considered in the paper. It is noted that the use of natural gas as a fuel, regardless of the technology, reduces carbon dioxide emissions from combustion products by 28 % compared to liquid fuels. All known designs of gas and dual-fuel engines fundamentally implement two technologies, namely, the use of homogeneous or heterogeneous gas-air mixtures. The most common is the technology of homogeneous mixtures, which provides high fuel efficiency and the highest environmental safety indicators. This technology provides for the supply of low-pressure gas to the intake ducts of the engine through automatic gas valves. There are practically no sulfur oxides, solid particles in the exhaust gases of the engine, and the emission of nitrogen oxides can be provided at the level of the requirements of the Tier III standard. At the same time, the main disadvantage of the homogeneous mixture technology is the potential penetration of natural gas with a high level of greenhouse effect (which is up to 28 times higher than the effect of carbon-acid gas) into the exhaust tract of the engine - “methane slippage”. This negative aspect can be largely minimized through the use of heterogeneous technology, when fuel gas is fed directly into the cylinder of a dual-fuel engine under high pressure, up to 50 bar, at the end of the compression process. This technology is becoming widespread in the structures of two-stroke engines due to the specifics of their gas exchange process. However, the high dynamics of the heat release process in the implementation of heterogeneous technology of gas-air mixtures is associated with a high emission of nitrogen oxides, commensurate with the emission of NOx by a diesel engine. Based on the analysis of the parameters and characteristics of the products of leading manufacturers implementing various technologies for using natural gas as fuel, conclusions about the potential advantages and prospects of using gas and dual-fuel engines are made.