Local Heat Exchange in the Combustion Chamber of a Hydrogen Engine Running on a Lean Fuel Mixture

The results of study of the working process, the local heat transfer in the combustion chamber, and the thermal state of the piston of a hydrogen engine with an external mixture formation are analyzed. Studies of the local heat transfer coefficients were carried out using a 3D-CRFD-mathematical model developed and verified on the basis of the experimental results, first used to study a hydrogen engine of this type. It has been established that the operation of a hydrogen engine on combustible mixtures of stoichiometric (or close to it) composition is impractical, since it leads not only to abnormal combustion processes and increased emission of nitrogen oxides, but also to an increase in local heat loads on parts, in particular on the piston, the local temperatures of which may exceed acceptable values. It is shown that the use of lean mixtures can prevent undesirable phenomena, in particular, reduce the emission of nitrogen oxides, reduce heat loads, and improve the heat-stressed state of the piston, providing acceptable conditions for the operation of the hydrogen engine.