Topical issue in recent years is the search for methods of reducing fuel consumption and improve environmental performance of internal combustion engines. In spark-ignition engines great importance is the type of ignition system and its components. This report examined the performance of the internal combustion engine running on gaseous fuels and with different types of spark plugs. Presented are the power-economic and environmental characteristics of different fuels and different types of spark plugs. Conclusions are practical and economic terms..

The paper presents studies on a high-speed diesel engine driven by added CNG (compressed natural gas) in order to increase its power. The effects of the amount of CNG added on the engine performance have been studied. Throughout the tests the effective performance and pollution emission indicators of ICE (Internal Combustion Engine), the cylinder pressure, etc. were measured. Under all operating conditions the diesel fuel consumption per hour and the rotation speed have remained constant. The amount of CNG added is variable. As a result of the research, relations have been established concerning the overall efficiency, the air to fuel ratio for steady-state performance and smoke opacity. An increase in CO, NOx and HC emissions has been recorded and at the same time the amount of CO2 released has decreased. Both the maximum pressure in the combustion chamber and the pressure rise rate increase which results in rising the engine performance harshness. When CNG has been added in quantity about 47% of the total amount of fuel, the peak value is achieved. The influence of the amount of added gas fuel on the calculated gross heat release rate has been determined. The maximum heat release rate does not change significantly. The nature of the combustion process does not change either. In conclusion, findings validate the possibility to achieve up to 30 % higher maximum rated power by adding 56% CNG mass fraction of the total amount of fuel. Provided the amount of CNG is up to 48% of the total amount of fuel, the ICE ecological indicators have not been deteriorated, furthermore the power has been increased by up to 20%.

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The paper presents a study of the variation of ignition advance when the engine works with methane and a comparison with values when the engine runs on gasoline. It is known that methane has a lower burning velocity than gasoline, and therefore, to obtain a maximal efficiency from the working process (the maximum value of cylinder pressure pz should be 7-15 degrees after TDC), ignition advance should be increased, as for different operating regimes this angle should be increased with different values. A gasoline engine has been studied and were measured and analysed the ignition advance at work with gasoline and methane, with optimal air-fuel ratio (α) for both fuels. Three-dimensional graphics of ignition advance variation across the rpm and load range were made. In conclusion, on the basis of the experiments, a table is produced, which presents the values of coefficients for change of base parameters of ignition advance for all engine operating modes, in dependence on rpm and load of the engine.