Diagnostic Sensing for Scramjet Combustors

Abstract

Embedded sensors fabricated using Direct Write technology were deployed for quantifying heat flux and monitoring component temperature within a direct-connect, hydrocarbon-fueled, scramjet combustor. Particular emphasis was placed on sensor fabrication and calibration, and performance was confirmed within a scramjet flowpath. Heat flux sensors employed a multilayer thermopile architecture fabricated via Direct Write, and were integrated directly onto the components to be tested . Sensors were calibrated using a combination of experimental measurements within custom calibration rigs for determining heat flux sensor sensitivity at ambient and elevated temperatures. Component instrumentation necessitated embedment of devices within a thermal barrier coating (TBC) deposited onto the wetted surface of the component, which was successfully demonstrated. Real-time measurements of component heat flux in high temperature combustion environments and supersonic gas flows was conducted via full-scale testing in a scramjet combustor operating at simulated Mach 5 flight conditions. Nomenclature k = thermal conductivity L = length of cavity N = number of thermopile elements P = pressure " = incident radiative heat flux " = heat flux through Direct Write sensor S = Seebeck coefficient t = dielectric thickness ∆T = temperature difference ∆V = output voltage β T = theoretical sensitivity factor β E = experimental sensitivity factor ε = emissivity