Compact Ejector Thrust Augmentation

Ejectors offer interesting means for resolving problems arising from the additional power requirements of V/STOL aircraft. They are capable not only of turning and augmenting the cruise engine's thrust vector, but their efflux can also serve to control circulation lift. The feasibility of ejector propulsion-lift concepts requires the simultaneous attainment of two conflicting objectives: high performance and compactness. Performance is degraded by losses occurring in the inlet, the primary nozzle, and the duct-diffuser of the ejector. Analytic results identified practical loss trade-offs that led to the design of the ejector's components. Static experiments with independently varied duct and diffuser lengths showed, surprisingly, that skewed flows can be diffused effectively. Augmentation ratios in excess of 1.85 were measured with a duct-diffuser 28 in. long. Increasing the length to 50 in. caused augmentation ratios to exceed 2.0.