Experimental investigation of compressed natural gas using in an indirect injection diesel engine at different conditions

Because of deficiency of fossil fuels and stringent emission legislations of environmental pollutants, many researches have been done on the sustainable fuel resources. Natural gas ranks as one of the most popular alternative fuels for public transportation due to its lower impact on human health and air quality, low cost, and appropriate availability. The novelty of this experimental work is replacing different mass fractions of diesel fuel with natural gas in an indirect injection diesel engine and evaluating its effect on the emissions of soot and nitrogen oxides, and brake specific fuel consumption in the presence of cold exhaust gas recirculation. The test bed is provided in the internal combustion engine laboratory of the Ferdowsi University of Mashhad by modifications on a naturally aspirated indirect injection diesel engine. Experiments were done at different equivalence ratios with 1200, 2000, and 3000 rpm and at 25, 50, and 75% of the full load in each speed. Replacing 40% mass fraction of input diesel fuel by adding natural gas resulted in a maximum 74% reduction of soot; the reason is a decrease in carbon to hydrogen ratio in the mixture. Also adding 40% natural gas made a maximum 54% reduction in nitrogen oxides mainly because of more homogeneity in the fuel mixture which reduces hot spots in the combustion chamber, and lower nitrogen content in the fuel. Moreover, maximum decrease in brake specific fuel consumption was 15%, due to increase in power output meanwhile lubricated engine friction remains unchanged in each speed. These research engine improvements in average are 62% for NOx and 35% for soot emission indicating acceptable decrease in exhaust emissions in comparison with allowable decrease in Euro emission standards. (C) 2020 Elsevier Ltd. All rights reserved.