Combustion Phenomena in a Rocket Motor

Fig. 14.4 Combustion phenomena in a rocket motor, from ignition to completion of the combustion.

Combustion of a propellant in a rocket motor accompanied by high-frequency pressure oscillation is one of the most harmful phenomena in rocket motor operation. There have been numerous theoretical and experimental studies on the acoustic mode of oscillation, concerning both the medium-frequency range of 100 Hz-1 kHz and the high-frequency range of 1 kHz-30 kHz. The nature of oscillatory combustion instability is dependent on various physicochemical parameters, such... 

Since the burning rate of a propellant is dependent on the burning pressure, the mass balance between the mass generation rate in the chamber and the mass discharge rate from the nozzle is determined by the pressure. In addition, the propellant burning rate in a rocket motor is affected by various phenomena that influence the mass balance relationship. Fig. 14.4 shows typical combustion phenomena encountered in a rocket motor, from pressure build-up by ignition to pressure decay upon completion of the combustion. 

In this paper, an overview of the important phenomena is given. The supercritical combustion process employed is also known to occur in liquid propellant rocket motors (e.g. in LOX/GH2-motors), liquid propellant guns (LPG), advanced aviation gas turbines and, to a lesser extent, in internal combustion engines. Supercritical combustion is characterized by (1) injection of at least one liquid state fuel component into a chamber which is thermodynamically in the supercritical state, (2) density ratios of fuel to oxidizer near one, (3) supercritical phase transitions of fluid-particles due to combustion, (4) non-ideal properties of the fluids. Additionally a short description of pertinent design criteria is given. 

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