Two-Dimensional Air Cushion Landing System Peripheral Jet Confirmation Study

Abstract:
A simplified two-dimensional peripheral jet theory for the equilibrium performance of an air cushion vehicle is investigated. The proposed theory intends to yield a rapid prediction of the actual flow rate and actual power requirements for an Air Cushion Landing System in the hover condition. Nine specific nozzle configurations were tested to determine which resulted in the best power-height performance and whether the theory is able to predict the experimental performance. Three single peripheral jet configurations were tested at a trunk pressure of 80 psfg. Six distributed jet configurations were tested at a trunk pressure of 40 psfg. Effects of inward flow injection angles of 30 degrees and 60 degrees were investigated. It was found that the simplified theory can adequately predict a value of the flow coefficient Cq for an ACLS nozzle conficguration. Values of the power-height parameter Chhd predicted by the theory always indicated better performance than was achieved experimentally. The beneficial effect of inward flow injection was demonstrated for each group of similar nozzle configurations. The single slot with 60 degree flow injection resulted in the best performance below cushion to truck pressure ratios of 0.5. Above this pressure ratio the distributed jet configurations with 60 degree inward injection resulted in superior performance.