Experimental and numerical study of heat flux in dual bell nozzles

The characteristic contour inflection of a dual bell nozzle is the key to altitude adaption. In sea level conditions, it forces the flow to a symmetrical separation, limiting the side load generation and increasing the thrust. After the transition, under high altitude conditions, the nozzle flows full, increasing the vacuum thrust. A hot flow experimental study has been conducted at the German Aerospace Center on a planar dual bell nozzle. The wall temperature distribution has been measured at various depths for the determination of the heat flux through the wall. The region of the inflection is of particular interest for the adjustment of the conventional cooling methods of dual bell nozzles. The contour inflection leads to a local increase of the thermal loads. In addition to the tests, the flow behavior and thermal loads have been calculated with CFD method and compared with the experiment