THE STUDY OF SPECIAL ASPECTS OF COMBUSTION IN A VARIABLE VOLUME COMBUSTION CHAMBER

The paper covers the study of special aspects of the application of ionization sensors intended for determining the characteristics of flame propagation (flame propagation velocity and the width of chemical combustion reactions area) in the variable volume combustion chamber. The review of contemporary methods of study of the process of hydrocarbon fuel combustion in piston engines showed the perspectivity of ionization sensors application. On a single-cylinder engine, the authors experimentally obtained and studied the main parameters of fuel combustion using the specially developed ionization sensors designed for identifying the characteristics of flame propagation when changing temperature, pressure, turbulence, and the combustion chamber volume in a wide range within several milliseconds. The variance of ion current, flame propagation turbulent velocity and the width of combustion chemical reactions area are determined depending on the fuel-air mixture composition when changing its physical and chemical properties due to the addition of hydrogen. It is shown that the change in the flame propagation turbulent velocity when adding hydrogen is caused by the increase in its normal component, and the width of turbulent combustion area is linearly related to the ion current value and its variance reflects the intensity of chemical combustion reactions. It is identified that despite the change in the excess air factor, the hydrogen concentration in fuel, and the engine speed rate, the linear dependence of flame width on the flame propagation turbulent velocity in the second combustion phase remains: the velocity increase corresponds to the flame width narrowing.