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Development of a fundamental model of hypergolic ignition in space-ambient engines.
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1967
Year
EngineeringCombustion EngineeringPropellant Accommodation CoefficientFuel InjectionHypergolic IgnitionIn-cylinder FlowThermodynamicsRocket EnginePropellant VaporizationFundamental ModelPropulsionMultiphase FlowSupersonic CombustionHeterogeneous CombustionAerospace EngineeringCombustion ScienceSpace-ambient EnginesAerospace PropulsionChemical KineticsIgnition
A fundamental model describing hypergolie ignition processes in spaceambient engines is presented. The model, whose development is being continued, is based on both physical kinetics of propellant vaporization and chemical kinetics of ignition reactions. Propellants considered are N2O4/MMH and O-i/UDMH, whose dominant ignition reactions at low pressure are gas phase. A computer program for predicting preignition chamber pressurization due to propellant vaporization is described. Calculated results show the effects on chamber pressurization of propellant spray drop sizes, propellant accommodation coefficient, transient flow build-up at valve opening, and nonadiabaticity of the vapor /drop system. Overall kinetic factors of ignition reactions, experimentally determined for use in the ignition delay model, are given. A subignition reaction intermediate, observed during the kinetics study, is described. Analytical engine ignition delays, based on the measured kinetic factors and on estimated vapor-phase composition and temperature, are in reasonable agreement with experimental values. Additional features for refining the present model are discussed.