Study of dynamic and ecological properties of automotive bi-fuel engine

Gaseous fuels are increasingly used to power internal combustion engines. Spark-ignition engines are fuelled with liquefied petroleum gas. Engines powered by gaseous fuels are characterized by good ecological properties due to the emission of pollutants. The paper presents the results of empirical tests of two passenger cars with spark-ignition engines powered alternatively: with gasoline and LPG fuel. The engines were equipped with fifth generation LPG fuelling systems. The tests were performed on a chassis dynamometer in tests used in approval procedures in Europe (NEDC test) and in the United States of America (FTP-75 test). These tests were the basis for determining the average specific distance emission of pollutants (carbon monoxide, hydrocarbons, nitrogen oxides and carbon dioxide) during the tests. The engines were also tested in the conditions of the external speed characteristics while accelerating the car in third gear. It was found that the type of fuelling the engines with both fuels has little influence on the dynamic properties of the engine due to the effective power. The tests clearly showed a decrease in specific distance emission of carbon monoxide and carbon dioxide. The relative reduction in specific distance emission of carbon monoxide was in the order of (45–65)%, and carbon dioxide—about 10%. For hydrocarbons, there was an increase in specific distance emission of hydrocarbons for the fuelling of engines with LPG, while for hydrocarbons, there was a large difference in the value of the relative specific distance emission difference for both tests. (The relative difference was from 25 to 175%.) Specific distance emission of nitrogen oxides turned out to be significantly higher when running engines with LPG. The reason for this is leaning of the fuel mixture at high rotational speed during acceleration of the car, which may result from insufficient conversion efficiency of engine control algorithms in the LPG fuel mode.