Cavity flameholders for ignition and flame stabilization in scramjets - Review and experimental study

Ben‐Yakar, Adela; Hanson, Ronald K.

doi:10.2514/6.1998-3122

Cited by 62 publications

(31 citation statements)

References 31 publications

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“…The appearance of a separation shock further forces the liquid jet to mix with the air upstream of the injection under subsonic 15 conditions. Exactly this zone is of importance in cases involving combustion due to its flame-holding capability [45,17] . After injection, the jet is deflected in a manner dependent on the momentum flux ratio [124].…”

Section: Flow Topologymentioning

confidence: 99%

Experimental Investigation of Liquid Fragmentation In Hypersonic Crossflow

Asma

Masutti

Chazot

2009

27th AIAA Applied Aerodynamics Conference

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Section: Flow Topologymentioning

confidence: 99%

Experimental Investigation of Liquid Fragmentation In Hypersonic Crossflow

Asma

Masutti

Chazot

2009

27th AIAA Applied Aerodynamics Conference

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“…Fuel and air can be entrained from the free stream flow into the cavity through the shear layer, or directly injected into the cavity itself. The trapped vortex concept has been shown by Ben-Yakar and Hanson (1998) Figure 4 illustrates the geometric classification of cavities. Nestler et al (1968) (Gruber et al, 2001; used without permission).…”

Section: Cavity Flameholdersmentioning

confidence: 99%

“…It seems then that the cavity's double vortex structure limits the effectiveness of increasing fuel input as a means of increasing combustion within the cavity. Ben-Yakar and Hanson (1998) suggested that the mass entrainment can be improved with the addition of fuel or a fuel-air combination within or upstream of the cavity. Gruber et al (2004) showed direct injection of fuel into the cavity flameholder to be an improvement over other forms of fuel injection such as upstream injection.…”

Section: Cavity Flameholdersmentioning

confidence: 99%

Performance Measurements of Direct Air Injection in a Cavity-Based Flameholder for a Supersonic Combustor

Edens¹

2006

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

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For several years the Air Force Research Lab Propulsion Directorate has been studying the difficulties in fueling supersonic combustion ramjet engines with hydrocarbon based fuels. Recent investigations have focused on the use of direct air injection into a directlyfueled cavity-based flameholder. Direct air injection has been shown qualitatively to be a valuable tool for improving cavity combustion. Little quantitative data is available that characterizes the performance of cavity-based flameholders. The objective of this research was to quantitatively determine the specific advantages and disadvantages of the direct air injection scheme. This was accomplished via intrusive probing into a supersonic free stream flow at an axial location behind the cavity flameholder. Pitot and static pressure, total temperature, and gas sampling measurements were taken and the corresponding values were processed to yield relevant engineering quantities. Data were taken over a range of fuel and air injection rates. Direct air injection resulted in increased combustion throughout the area of interest behind the cavity. Air injection increased the static temperature and pressure throughout the area of interest. Enthalpy spread into the free stream was also increased through the use of air injection. Total pressure losses increased as a result of the direct air injection scheme. The ratio of enthalpy increase to increase in total pressure losses increased with higher fuel flow rates, indicating that the direct air injection technique shows more promise for higher fuel loadings.iv

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“…One relatively obvious approach for scramjet flameholding is to consider fundamental resonant frequencies in cavity pressure oscillations caused by ducted supersonic flows, and resultant turbulent shear layer flows, over both open and closed cavities [25]. For example, application of a "modified Rossiter" expression, reviewed in [25], predicts a fundamental frequency of 2960 Hz for a typical free stream air velocity of 1500 m/s over an open cavity of 10-cm. length.…”

Section: Implications For Scramjet Combustorsmentioning

confidence: 99%

Dynamic Weakening (Extinction) of Simple Hydrocarbon-Air Counterflow Diffusion Flames by Oscillatory Inflows

Pellett¹,

Kabaria²,

Panigrahi³

et al. 2005

41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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This study of laminar non-premixed HC-air flames used an Oscillatory-input Opposed Jet Burner (OOJB) system developed from a previously well-characterized 7.2-mm Pyrex-nozzle OJB system. Over 600 dynamic Flame Strength (FS) measurements were obtained on unanchored (free-floating) laminar Counterflow Diffusion Flames (CFDF's). Flames were stabilized using plug inflows having steady-plus-sinusoidal axial velocities of varied magnitude, frequency, f, up to 1600 Hz, and phase angle from 0 (most data) to 360 degrees. Dynamic FS is defined as the maximum average air input velocity (U air , at nozzle exit) a CFDF can sustain before strain-induced extinction occurs due to prescribed oscillatory "peak-to-peak" velocity inputs superimposed on steady inputs.Initially, dynamic flame extinction data were obtained at low f, and were supported by 25-120 Hz HotWire cold-flow velocity data at nozzle exits. Later, expanded extinction data were supported by 4-1600 Hz Probe Microphone (PM) pk/pk P data at nozzle exits. The PM data were first obtained without flows, and later with cold stagnating flows, which better represent speaker-diaphragm dynamics during runs. The PM approach enabled characterizations of Dynamic Flame Weakening (DFW) of CFDF's from 8 to 1600 Hz. DFW was defined as % decrease in FS per Pascal of pk/pk P oscillation, namely, DFW = -100 d(U air / U air,0Hz ) / d(pkpk P). The linear normalization with respect to acoustic pressure magnitude (and steady state (SS) FS) led to a DFW unaffected by strong internal resonances.For the C 2 H 4 /N 2 -air system, from 8 to 20 Hz, DFW is constant at 8.52 + 0.20 (% weakening)/Pa. This reflects a "quasi-steady flame response" to an acoustically induced dU air /dP. Also, it is surprisingly independent of C 2 H 4 /N 2 mole fraction due to normalization by SS FS. From 20 to ~ 150 Hz, the C 2 H 4 /N 2 -air flames weakened progressively less, with an inflection at ~ 70 Hz, and became asymptotically insensitive (DFW ~ 0) at ~ 300 Hz, which continued to 1600 Hz. The DFW of CH 4 -air flames followed a similar pattern, but showed much greater weakening than C 2 H 4 /N 2 -air flames; i.e., the quasi-steady DFW (8 to ~ 15 Hz) was 44.3 %/Pa, or ~ 5x larger, even though the 0 Hz (SS) FS was only 3.0 x smaller. The quasi-steady DFW's of C 3 H 8 -air and C 2 H 6 -air were intermediate at 34.8 and 20.9 %Pa, respectively. The DFW profiles of all four fuels, at various frequencies, correlated well but non-linearly with respective SS FS's. Notably, the DFW profile for C 3 H 8 -air fell more rapidly in the range > 15 to 60 Hz, compared with the 1-and 2-carbon fuels. This may indicate a shift in chemical kinetics, and/or O 2 transport to a flame that moved closer to the fuel-side.

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Cavity flameholders for ignition and flame stabilization in scramjets - Review and experimental study

Cited by 62 publications

References 31 publications

Experimental Investigation of Liquid Fragmentation In Hypersonic Crossflow

Experimental Investigation of Liquid Fragmentation In Hypersonic Crossflow

Performance Measurements of Direct Air Injection in a Cavity-Based Flameholder for a Supersonic Combustor

Dynamic Weakening (Extinction) of Simple Hydrocarbon-Air Counterflow Diffusion Flames by Oscillatory Inflows

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