In order to obtain a perfect nozzle, which provides maximum thrust with a given expansion ratio, a new concept of nozzle design is presented.
Primary efflux from a convergent nozzle into the secondary flow atmosphere, and pressure distribution in the axial direction of the secondary flow, is arranged to give the primary flow the ideal wall pressure distribution of a perfect nozzle.
The secondary flow presents a cushioning action to the primary flow to prevent irregular expansion or shock waves, and provides a lubricating effect to reduce wall friction.
The secondary nozzle wall shape and the optimum secondary pressure are computed.
A similar idea has been utilized in the tail nozzle of the F-104 fighter in the form of a double convergent nozzle.
Experiments were conducted to investigate the flow by means of Schlieren pictures, and to measure the thrust of a model nozzle.
