Stability limits of cavity-stabilized flames in supersonic flow

Rasmussen, Chadwick C.; Driscoll, James F.; Hsu, Kuang–Yu; Donbar, Jeffrey M.; Gruber, Mark; Carter, Campbell D.

doi:10.1016/j.proci.2004.08.185

Cited by 142 publications

(79 citation statements)

References 13 publications

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“…Recently, endothermic catalytic cracking of HC fuels has also been investigated [1][2]. Difficult and competing objectives remain, however, to achieve ignition and robust combustion in relatively small subsonic cavity flameholders -so as to (a) generate rapid reaction with sufficient initial heat release, (b) avoid excessive internal drag and loss of net thrust, and (c) achieve needed "endothermic" heat soak in active cooling channels without the formation and deposition of significant carbon residues [2][3][4][5][6][7][8]. Thus catalytically cracked fuel vapor and entrained air must mix, diffuse and react long enough in a subsonic cavity to achieve ignition with robust "incipient flameholding," to supply radicals and adequate enthalpy to the overriding supersonic flow, with minimal loss of initial kinetic energy.…”

Section: Introductionmentioning

confidence: 99%

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels

Pellett¹,

Convery²,

Wilson³

2006

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Opposed Jet Burner (OJB) tools have been used extensively by the authors to measure Flame Strength (FS) extinction limits of laminar H 2 /N 2 -air and (recently) hydrocarbon (HC)-air Counterflow Diffusion Flames (CFDFs) at one atm. This paper details normalization of FSs of N 2 -diluted H 2 and HC systems to account for effects of fuel composition, temperature, pressure, jet diameter, inflow Reynolds number, and inflow velocity profile (plug, contoured nozzle; and parabolic, straight tube). Normalized results exemplify a sensitive accurate means of validating, globally, reduced chemical kinetic models at ~ 1 atm and the relatively low temperatures approximating the loss of non-premixed "idealized" flameholding, e.g., in scramjet combustors.Laminar FS is defined locally as maximum air input velocity, U air , that sustains combustion of a counter-jet of g-fuel at extinction. It uniquely characterizes a fuel. And global axial strain rate at extinction (U air normalized by nozzle or tube diameter, D n or t ) can be compared directly with computed extinction limits, determined using either a 1-D Navier Stokes stream-function solution, using detailed transport and finite rate chemistry, or (better yet) a detailed 2-D Navier Stokes numerical simulation. The experimental results define an "idealized flameholding reactivity scale" that shows wide ranging (50 x) normalized FS's for various vaporized-liquid and gaseous HCs, including, in ascending order: JP-10, methane, JP-7, n-heptane, n-butane, propane, ethane, and ethylene. Results from H 2 -air produce a unique and exceptionally strong flame that agree within ~1% of a recent 2-D numerically simulated FS for a 3 mm tube-OJB. Thus we suggest that experimental FS's and/or FS ratios, for various neat and blended HCs w/ and w/o additives, offer accurate global tests of chemical kinetic models at the Ts and Ps of extinction.In conclusion, we argue the FS approach is more direct and fundamental, for assessing, e.g., idealized scramjet flameholding potentials, than measurements of laminar burning velocity or blowout in a Perfectly Stirred Reactor, because the latter characterize premixed combustion in the absence of aerodynamic strain. And FS directly measures a chemical kinetic characteristic of non-premixed combustion at typical flameholding temperatures. It mimics conditions where gfuels are typically injected into a subsonic flameholding recirculation zone that captures air, where the effects of aerodynamic strain and associated multi-component diffusion become important.

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Section: Introductionmentioning

confidence: 99%

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels

Pellett¹,

Convery²,

Wilson³

2006

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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“…Driscoll and Rasmussen [16], Rasmussen et al [17,18], and Chadwick et al [19] showed that the correlations of premixed flame could not be directly applied to supersonic combustion, in which the fuel is injected into the airflow upstream or inside the cavity and the flame is actually non-premixed. Chadwick et al [19] have proposed a theoretical model to correlate the blowout equivalence ratio with the Damköhler number for the non-premixed flames of small-molecule fuels, such as hydrogen, ethylene, methane, and acetylene.…”

Section: Introductionmentioning

confidence: 99%

Blowout Limits of Cavity-Stabilized Flame of Supercritical Kerosene in Supersonic Combustors

Zhang

Wang

et al. 2014

Journal of Propulsion and Power

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Blowout limits of cavity-stabilized flame of supercritical kerosene were experimentally studied by using Mach 2.5 and 3.0 direct-connect supersonic model combustors operated under various air and fuel conditions. Specifically, the effects of the stagnation temperature and the stagnation pressure on the blowout limits were investigated for supercritical kerosene injected from the wall upstream of a cavity flameholder in a Mach 2.5 combustor. Experiments were performed under the same conditions for supercritical kerosene injected from the rear part of the cavity bottom to study the influence of the location of fuel injection. The blowout limits of supercritical kerosene injected from the wall upstream of the cavity were further investigated in a Mach 3.0 combustor. Besides the effects of the stagnation temperature and stagnation pressure, the effect of the divergence angle of the combustor on the lean-fuel blowout limit was studied. Results show that there exist two blowout limits corresponding to the lean-and rich-fuel conditions for a given stagnation temperature. The location of fuel injection has substantial influence on the blowout limits, whereas the influence of the stagnation pressure and the divergence angle of the combustor can be neglected in the range of interest.

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“…Common assistant ignition technique includes: (1) Igniter. Igniters, producing a small high temperature region in the flow-field such as spark (Chadwick et al, 2005), flame torch, arc discharge (Aleksandrov et al, 2006) etc. and also releasing lots of radicals such as plasma torch (Watanabe, Abe, & Takita, 2009), could effectively assist for ignition and combustion.…”

Section: Introductionmentioning

confidence: 99%

Experimental Research on Hydrogen and Hydrocarbon Fuel Ignition for Scramjet at Ma=4

Zhang¹,

Le²,

Yang³

et al. 2013

MAS

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Ignition experiments of Hydrogen and Ethylene were performed on direct-connected pulse combustion facility. Air stagnation temperatures were 900 K and stagnation pressures were 0.8 MPa, the entrance Mach number was approximate 2.0 provided by a two-dimension nozzle. The experimental results indicate that: (1) Hydrogen self-ignition won't occur at stagnation 935 K when it is injected upstream the cavity in this combustor model. But with low input power igniter, hydrogen can be ignited reliably. (2) Ethylene cannot be ignited with igniter only even at high igniter power. Under the assistant of both igniter and pilot Hydrogen, Ethylene can be ignited reliably and maintain stable combustion after the igniter and pilot hydrogen completely turned off. (3) The lowest equivalence ratio of pilot hydrogen for successful ethylene ignition is 0.05 below that ignition will fail. (4) When pilot hydrogen and igniters were both employed for ignition, the function of igniter is to ignite the hydrogen and the input power of igniter has no influence on ignition performance.

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Stability limits of cavity-stabilized flames in supersonic flow

Cited by 142 publications

References 13 publications

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels

Blowout Limits of Cavity-Stabilized Flame of Supercritical Kerosene in Supersonic Combustors

Experimental Research on Hydrogen and Hydrocarbon Fuel Ignition for Scramjet at Ma=4

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