Hybrid Large Eddy Simulation/Reynolds-Averaged Navier–Stokes Analysis of a Premixed Ethylene-Fueled Dual-Mode Scramjet Combustor

Hydrocarbon fuels offer optimal high energy per volume for scramjet applications for sustained hypersonic flight but require additional residence time due to slower ignition delays (compared with hydrogen fuel). The injection of ethylene at the start of the isolator of a dual-mode scramjet combustor...

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Bibliographic Details
Published in:AIAA journal 2021-07, Vol.59 (7), p.2440-2456
Main Authors: Nielsen, Tanner B, Edwards, Jack R, Chelliah, Harsha K, Lieber, Damien, Geipel, Clayton, Goyne, Christopher P, Rockwell, Robert D, Cutler, Andrew D
Format: Article
Language:English
Subjects:
Aerodynamics
Combustion chambers
Computational fluid dynamics
Direct numerical simulation
ENGINEERING
Ethylene
Flame structure
Flow velocity
Fluid flow
Hydrocarbon fuels
Hydrogen fuels
Hypersonic flight
Large eddy simulation
Mathematical models
Navier-Stokes equations
Numerical prediction
Particle image velocimetry
Raman spectroscopy
Reynolds averaged Navier-Stokes method
Simulation
Stability
Stabilization
Supersonic combustion ramjet engines
Turbulent combustion
Turbulent flames
Vortices
Wall pressure
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Summary:Hydrocarbon fuels offer optimal high energy per volume for scramjet applications for sustained hypersonic flight but require additional residence time due to slower ignition delays (compared with hydrogen fuel). The injection of ethylene at the start of the isolator of a dual-mode scramjet combustor, operating in ramjet mode, allows sufficient mixing to achieve efficient premixed turbulent combustion. A cavity flameholder anchors the flame, supplying sufficient radicals to sustain a stable flame in the high-speed environment. This work investigates flame structure and stabilization limits of a new configuration with a scaled-down cavity embedded in the flow path of the combustor with a strut and insert. The cavity is reduced in size by one-third to enable eventual direct numerical simulations of the flame stabilization process. This work, however, focuses on modeling the full isolator/combustor geometry using a hybrid large eddy simulation/Reynolds-averaged Navier–Stokes simulation strategy. Particle image velocimetry, planar laser-induced fluorescence, coherent anti-Stokes Raman spectroscopy, and pressure measurements are compared with numerical predictions to analyze and characterize the conditions within the combustor, including flame structure, flow velocities, species composition, and wall pressure. An adjustable air throttle in the extender is able to control the placement of the shock train in the isolator and maintain a stable flame at various equivalence ratios. The simulations show reasonably good agreement with the experimental scalar and velocity data and predict a flame angle consistent with premixed turbulent flame-speed correlations.
ISSN:0001-1452
1533-385X
DOI:10.2514/1.J059343