MAXIMUM COMBUSTION PRESSURE AND ITS RELATIONSHIP WITH THE CHARACTERISTICS OF COMBUSTION IN SPARK IGNITION ENGINES

The paper presents the results of the study of the possible relationship of the maximum combustion pressure characterizing the efficiency of heat dissipation with the main characteristics of combustion in piston internal combustion engines (ICE). During the experiments, to change the flame propagation characteristics, hydrogen in the amount of 3 % and 5 % of the mass fuel consumption was added to the air-fuel mixture, as well as the fluid turbulence was changed when using two crankshaft speed values. The authors determined the dependences of maximum combustion pressure P_zmax of the fuel-air mixture and the ion current flame intensity in the zone the most distant from the ignition plug on the composition of the fuel-air mixture with hydrogen additives during its combustion in a combustion chamber of variable volume. The addition of hydrogen leads to the decrease in the combustion time and the increase in the ion current intensity and the maximum combustion pressure of the fuel-air mixture. The authors considered the main combustion characteristics: time, ion current, volume at the moment of maximum pressure, turbulence, crankshaft speed, and their influence on the maximum combustion pressure. The study identified the relationship of the combustion pressure with the ion current reflecting the intensity of chemical reactions of combustion in the zone the most distant from the ignition plug, as well as with the volume of combustion completion. The experimental points are accurately connected by a single curve line. The obtained experimental dependences can be represented as a polynomial of the 2nd order. The authors identified the influence of turbulence change due to the change of crankshaft speed on maximum combustion pressure P_zmax. The authors proposed the experimental mathematical relationship between the maximum combustion pressure and the crankshaft speed. Knowing the maximum combustion pressure on one speed range and using the obtained dependence, it is possible to predict the value of its variable for the whole interval of speed ranges of engine work.

combustion, turbulence, combustion pressure, hydrogen addition, ion current, combustion engine, heat dissipation, combustion characteristics, chemical reaction intensity