Investigation of Heat Transfer and Scale Effects on the Performance of a Giffard Injector-Pumped Microrocket

A novel approach to propellant pressurization for microscale rocket engines is introduced. The Giffard injector is shown to be a viable alternative to turbomachinery for pressurizing the liquid propellants on board a microrocket, offering a design free of moving parts. Extending the authors’ previous work, the engine performance is computed for several fuel/oxidizer combinations. A large-scope study of the heat transfer throughout the regenerative cooling engine cycle examines the effects of combustion chamber pressure and engine size on performance. A boiler is designed that facilitates the heat transfer required for adequate cooling and is modeled using the effectiveness-number of transfer units method. The computed specific impulse and thrust-to-weight ratio of the design for the propellants considered are roughly 250 s and 2000, respectively. The power density of the proposed injector-pumped design is seen to behave like that of turbopumped microrockets up to a critical nozzle throat diameter of approximately 1 cm, beyond which the advantages of an entirely static structure are outweighed by decreasing performance.