Study on the formation and maintenance mechanism of the stationary flame at the head of a LOX/GCH4 pintle injector element

The mechanism of the formation and maintenance of the stationary flame at the head of a LOX/GCH4 pintle injector element was investigated by experiment and numerical simulation. The total propellant flow rate is 153 g/s, the mixing ratio is 1.48, and the combustion chamber pressure is 1.06 MPa in the hot fire test. Non-contact optical measurement technology was adopted to obtain the flame images. Experimental results indicated that the stationary flame at the pintle head is formed during the start-up stage of the combustion chamber and maintained here throughout the whole combustion process. And there were obvious overheat regions at the pintle head caused by the stationary flame. The spray distribution at the pintle head was simulated by the VOF-to-DPM method. Numerical results showed that there were low-velocity and liquid mist enrichment regions behind the liquid jets, and their positions were basically coincided. Meanwhile, the positions of the low-velocity and liquid mist enrichment regions were basically the same as the positions of the overheat regions caused by the stationary flame in the hot fire test. The main reason for the formation of the stationary flame at the head of the pintle injector element is the existence of the low-velocity and liquid mist enrichment regions behind the liquid jets. The continuous transport of the droplets generated by the surface breakup of the liquid oxygen jets to the low-velocity regions is the significant factor for the maintenance of the stationary flame.