Evaluation of Full-Scale Hovercraft Lift Systems.
DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD
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Design of a hovercraft lift system is normally based upon fairly simple hydraulic models of the lift system components. Lift system loss coefficients and fan efficiencies are determined from prior experience, empirical data bases and components or system model studies. Prediction of full-scale performance is complicated by the difficulty of establishing corresponding between model-scale and full-scale values of Reynolds number, Mach number and Euler number. Full-scale verification of the lift system design process is an essential part of hovercraft development. This paper presents results of a full-scale evaluation of the performance of a hovercraft lift system, and performance characteristics are compared with model-scale results. Comparisons of lift system loss coefficients show good correlation, but lift system efficiencies are shown to be significantly higher in full-scale results than from model-scale predictions. Three lift-fan designs are discussed and an increase in lift system efficiency of 10 to 15 is observed for a mixed-flow fan over a centrifugal-flow fan design. Keywords Air cushion vehicles, Lift fans and Model theory.
- Surface Effect Vehicles and Amphibious Vehicles