The Taylored Nozzle: A Method for Reducing the Convective Heat Transfer to Nozzle Throats by Gasdynamic Shielding

Abstract

A novel method to reduce the convective heat transfer rate to the throat walls of nozzles employed in hypersonic research facilities, high performance propulsion devices or high temperature industrial processes is presented. The technique described herein utilizes a light gas film (helium, hydrogen, or perhaps even methane), which is injected tangentially along the wall upstream of the region where the convective heat transfer rate is large. The acoustic impedance of the gas film is matched or tailored (“Taylored”) to that of the main gas so as not to interfere significantly with the expansion of the main flow of gas and to minimize mixing. As a result, the light gas film has a significantly lower static and total temperature than the main flow of gas, hence reducing the convective heat transfer rate to the nozzle walls. This reduction in convective heat transfer rate allows the facility, device, etc., to operate at higher total enthalpies for longer durations. The general method is presented, as well as analytical and numerical studies which assess the effectiveness and viabilitv of the technique.