Combustion Characteristics in a Pure Hydrogen-Oxygen Engine Under Various Oxygen Equivalence Ratios and Engine Speeds for Space In-Orbit

In this study, three-dimensional (3D) and one-dimensional (1D) models of port fuel injection (PFI) hydrogen-oxygen internal combustion engine (H2-O2 ICE) were established. Firstly, the experiment of PFI-H2 ICE was conducted to validate the accuracy of the simulation models. Then the effects of the oxygen equivalence ratio (ΦO2) and engine speed in the combustion process were analyzed. Results show that two threshold values in the H2-O2 ICE combustion can be deduced. When ΦO2 = 0.20, the combustion process is violent with extremely high temperatures and pressure, called excessively intense combustion. When ΦO2 = 0.10, the flame propagation is slow, suggesting it is difficult to ignite at a smaller oxygen equivalence ratio. Moreover, the influence of engine speed on performance parameters is analyzed in a 1D simulation. Results show that the fluctuation of brake thermal efficiency with engine speed becomes more obvious with the decrease in the oxygen equivalence ratio.