Heat Flux Measurements in a Scramjet Combustor Using Direct Write Technology

Abstract

In this experimental study, heat flux measurements were made at four locations within the isolator/combustor/nozzle region of a direct-connect gaseous hydrocarbon-fueled scramjet combustor. Combustor conditions were fixed and representative of a Mach-5 flight condition. The heat flux measurements were made using sensors deposited directly on the engine thermal barrier coating (TBC) using Direct Write Technology. Flush-wall fuel injection locations were fixed and a cavity on the body side wall provided the necessary flame holder. Overall equivalence ratios were varied from 0.6 to 1.0, but were held constant for a given run. Preliminary results show heat flux values rising with combustor equivalence ratio at all measurement locations. Heat flux values ranging from 400 to 1000 kW/m 2 (35 to 88 BTU/ft 2 -s) were measured in the location downstream of the cavity flame holder. Heat flux values ranging from 600 to 2000 kW/m 2 (53 to 176 BTU/ft 2 -s) were measured in the cavity flame holder location. Heat flux values ranging from 200 to 600 kW/m 2 (18 to 53 BTU/ft 2 -s) were measured in the locations upstream of the cavity flame holder. Measured local heat flux values were consistent with area-averaged heat flux measurements over a section of the combustor. Nomenclature D = depth of cavity k = thermal conductivity L = length of cavity N = number of thermopile elements k = thermal conductivity P = pressure S = Seebeck effect T = temperature   fuel equivalence ratio Q = flight dynamic pressure L x = thickness of material x R x = thermal resistance of material x q = heat transfer rate = heat flux (heat transfer rate per unit area) = mass flow rate c p = specific heat

Diagnostic Sensing for Scramjet Combustors

“…These trends are consistent with calorimetric measurements taken at locations within the combustor (inlet and pilot cavity) and truncated nozzle (up and downstream of the instrumented plug) 16 . However, quantitative deviations are apparent between the Direct Write sensor responses and the calorimetric heat flux measurements, which can be attributed to:…”

“…While only representative results are presented herein, a full discussion of the test results can be found in Kennedy et al 16 . Data for these tests was acquired at 100Hz sampling rates using a National Instruments hardware DAQ card, with voltage channels configured for the heat flux thermopile signal, as well as the upper and lower thermocouple junction signals.…”

Numerical study of combustion and convective heat transfer of a Mach 2.5 supersonic combustor

“…Vincent et al [9] obtained surface heat flux and temperature of Zirconia-coated copper wall via water-cooled heat flux gage and sub-surface temperature measurement for HIFiRE Direct Connect Rig. Kennedy et al [10] applied Direct Write Technology for the measurement of heat flux of a direct-connect hydrocarbon-fueled scramjet combustor.…”

Application of conjugate gradient method for estimation of the wall heat flux of a supersonic combustor

“…Both direct and indirect measurement techniques have been developed to measure the inner wall heat flux and temperature. Heat flux sensor, directly contacting the combustor flow, is the most commonly used apparatus [1,2]. However, its operation lifetime and reliability are limited due to combustor flow with high temperature, high speed and considerable fraction of oxygen.…”