Hydrogen Mixing with Air and Its Combustion under Direct Jet Injection into the Small-Scale Chamber

The study numerically simulated the mixing of hydrogen with air and its subsequent combustion with a direct jet injection of hydrogen and its ignition from an external source. The pulsed jet flow is simulated using a high-pressure chamber where hydrogen is initially stored at a pressure of up to 700 atm. The hydrogen flow is achieved through a system of valves, the number of which varies from one to six. The hydrogen supply time is calculated based on an estimate of the hydrogen content in the combustion chamber, corresponding to the stoichiometric ratio of the components of the hydrogen–air mixture. The dimensions of the combustion chamber are selected to correspond to the dimensions of the combustion chamber of a small-sized gas piston engine. In this way, the process of direct injection of hydrogen to the combustion chamber is simulated. In a series of calculations, ignition occurs at different stages of mixing, which allows us to evaluate the efficiency of the direct hydrogen injection system, including the completeness of combustion of the fuel supplied to the combustion chamber. It is shown that the fastest mixing occurs when hydrogen is supplied through a system of six slits, with the mixing time being about 25 ms. Subsequent ignition leads to combustion of the hydrogen–air mixture in about 1 ms, and the degree of hydrogen incomplete combustion is 9.5%.