Features of heat transfer in a pre-nozzle volume of a solid-propellant rocket motor with charges of complex shapes

Local features of thermophysical processes in the channels and pre-nozzle volumes of solid-propellant rocket engines with case-bonded charges of different cross-sectional shapes are considered. The influence of the charge shape on the heat exchange in the nozzle bottom is investigated. It is shown that the value of the Nusselt number at a critical point on the multi-nozzle bottom is determined both by the charge channel form and by the geometry of the pre-nozzle volume. By processing the numerical experimental results the criterial dependences for determining the Nusselt number in the areas of local increase of heat exchange intensity are obtained. The obtained dependences are compared with the known empirical formulas [1-4]. It is found that the use of empirical relationships to estimate the Nusselt number leads to incorrect determination of the parameters of heat transfer on the armored surfaces of the charge, the nozzle covers, and the input parts of the submerged rotating nozzle.