INVESTIGATION OF COMBUSTION CHARACTERISTICS OF A HIGH CHAMBER PRESSURE ROCKET MOTOR

The objectives of the experimental and analytical investigation were to: (1) Successfully operate a rocket motor at a chamber pressure level of 4000 psia. (2) Determine the performance of the high pressure rocket motor. (3) Determine the pressure regulated feed system limitations to prevent the occurrence of low frequency instability. (4) Monitor the occurrence of high frequency instability of the unpulsed high pressure rocket motor tests. (5) Predict the combustion characteristics of the high pressure rocket motor tests with the Priem-Heidmann steady-state vaporization model.; The experimental investigation employed storable hypergolic propellants, nitrogen tetroxide and a 50-50 blend by weight of hydrazine and unsymmetrical dimethyl hydrazine. Rocket motor experiments were conducted at a chamber pressure level of 4000 psia over a range of mixture ratios, contraction ratios, characteristic lengths and flow rates. Two injectors each having seven quadlet elements with like-on-like impingement but with different orifice sizes were employed in the experimental program.; The results of the experimental investigation showed that in order to achieve successful rocket motor operation at 4000 psia chamber pressure, the overshoot in pressure that occurs in the fuel manifold during the start transient must be kept at a minimum. High performance was obtained from the rocket motor firings with C* efficiencies averaging 99%. Both injectors used in the investigation were high performance injectors and the optimum characteristic length was determined to be less than the 45 inches minimum employed for this program. Low frequency instability, chugging, was encountered during the experimental investigation when the pressure drop across the injector was less than 10% of the chamber pressure. None of the unpulsed 4000 psia chamber pressure rocket motor experiments exhibited any high frequency instability.; In the analytical investigation the Priem-Heidmann steady-state vaporization model was used to predict the combustion characteristics of a high pressure rocket motor operation. The analytical results showed that performance increased with pressure and that the performance for the small orifice tube injector was greater than the large orifice tube injector. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI...