The Influence of the “Piston Heat Belt–Sleeve” Gap on Heat Exchange in the Combustion Chamber of an Engine Depending on the Fuel Utilized

Numerous experimental works concerning the comparative analysis of heat transfer processes in hydrogen and gasoline engines have confirmed the noticeable increase in heat loss in the case of applying hydrogen. Without denying the influence of higher values of the flame propagation velocity and the hydrogen combustion temperature contributing to intensification of the convective heat transfer in the combustion chamber, the present article shows that, when using hydrogen as a fuel, the main problem consists in penetration of the flame into the gap between the heat belt of the piston and the sleeve. We analyze this phenomenon using the flame extinguishing theory by Ya.B. Zeldovich. On the base of the unsteady heat flux measurements in the gap, as well as of 3D simulation of both the thermophysical processes in the combustion chamber and the thermal state of the piston of the experimental gasoline engine converted to hydrogen, we explain the phenomenon of relative increase in heat losses in the hydrogen engine, its existence previously having been shown experimentally without theoretical justification.