Combustion Regimes of Hydrogen at Its Direct Injection Into the Internal Combustion Engine Chamber

This paper analyzes processes in the combustion chamber of spark ignition engine under direct jet injection of hydrogen during the compression stroke. Numerical modeling is used to study the features of mixing hydrogen with air and its combustion after ignition from a spark at the instant when the piston reaches the top dead center (TDC). The combustion regimes that develop when the injection pressure is varied from 20 to 140 atm, and the start of injection, from 180° to 45° of the crank angle (CA) before the TDC, are considered. In all cases the mass of hydrogen necessary for the formation of a stoichiometric mixture with air during injection into the combustion chamber is supplied. It is found that the most uniform mixture at the time of ignition is formed with advanced injection (180°–135° of the CA before the TDC) at a relatively low pressure (20–60 atm). The ignition of a uniform mixture in the conditions considered leads to detonation regime of combustion. A lower degree of uniformity of the mixture corresponds to a slow, deflagration combustion regime. It is important to note that nonuniformity of the mixture determines the ambiguity of the formation of a certain combustion regime, depending on the local mixture composition in the vicinity of a spark. At the same time, the slowest combustion regime provides the maximum hydrogen combustion incompleteness, up to 8.2%. Generally, the considered ranges of injection pressure and start of injection lead to satisfactory levels of incompleteness of hydrogen combustion of less than 4%.