Experimental studies on the effect of base bleed on aerospike nozzle

Based on experimental data of 1-cell aerospike nozzle, the effect of base bleed on aerospike nozzle performance and base behaviour was presented. Pressure distribution along plug surface under different ambient pressure was obtained. It was shown that base has different aerodynamic behaviour at different ambient pressure. The nozzle pressure ratio at base transition increased and the nozzle pressure ratio at which base thrust starts to be positive decreased when some base bleed was injected. A sudden thrust reduction at base transition was also avoided with base bleed injection. Base pressure level was not increased any more when more than 2.0% base bleed ratio was carried out; as a result the overall efficiency of the aerospike nozzle was reduced. It was found that 1.5% to 2.0% base bleed ratio seems to be the optimum value. At low altitude, pressure was raised along the rear part of the plug. With the ambient pressure decreasing, the pressure amplitude became smaller and the pressure rising position moved rearward until out of the plug surface eventually.