A new design approach of a compact high performance bipropellant liquid rocket engine combustors

Based on the theory of group conjugate and normal combustion of bipropellants, a design procedure of a minimum length combustor for a prescribed combustion efficiency at fixed propellant flow rates and a constant fuel group combustion dumber is developed. Die optimum Sauter Mean Diameter (SMD) and the corresponding droplet number density that give the minimum burner length are provided to aid in the design of an optimum injector. It is estimated, for example, an approximately 10% reduction in a burner length la achieved when the SMD of oxidizer droplets is increased from 20 μm to 60 μm which is the optimum value for the selected flow rates- the minimum length requirement for the optimum burner is attributed to the rapid axial development of the combustion rate rather than the fast vaporization rate. The present approach can be used for all cryogenic propellants, partially cryogenic or non- cryogenic bipropellant combinations.