Strain-induced extinction of hydrogen-air counterflow diffusion flames - Effects of steam, CO2, N2, and O2 additives to air

Pellett, G. L.; Northam, G. B.; Wilson, Lloyd G.

doi:10.2514/6.1992-877

Cited by 12 publications

(14 citation statements)

References 10 publications

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“…An example of experiments to study the reaction and the potential flameholding of fuel in ground facilities relative to clean air have been performed using an opposed jet burner. 50 This study and others showed that the effects of test gas contaminants present in a methane-fired facility decreased flame strength by about 7%. In addition, the results indicated that careful control of the oxygen replenishment was essential to propulsion testing, with a one-percent increase (from 21-22%) being sufficient to offset the decrease in flame strength.…”

Section: Facility Contaminantsmentioning

confidence: 68%

Experimental supersonic combustion research at NASA Langley

Rogers

Capriotti

Guy

1998

20th AIAA Advanced Measurement and Ground Testing Technology Conference

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Experimental supersonic combustion research related to hypersonic airbreathing propulsion has been actively underway at NASA Langley Research Center (LaRC) since the mid-1960's. This research involved experimental investigations of fuel injection, mixing, and combustion in supersonic flows and numerous tests of scramjet engine flowpaths in LaRC test facilities simulating flight from Mach 4 to 8. Out of this research effort has come scramjet combustor design methodologies, ground test techniques, and data analysis procedures. These technologies have progressed steadily in support of the National Aero-Space Plane (NASP) program and the current Hyper-X flight demonstration program. During NASP nearly 2500 tests of 15 scramjet engine models were conducted in LaRC facilities. In addition, research supporting the engine flowpath design investigated ways to enhance mixing, improve and apply nonintrusive diagnostics, and address facility operation. Tests of scramjet combustor operation at conditions simulating hypersonic flight at Mach numbers up to 17 also have been performed in an expansion tube pulse facility. This paper presents a review of the LaRC experimental supersonic combustion research efforts since the late 1980's, during the NASP program, and into the Hyper-X Program.

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Section: Facility Contaminantsmentioning

confidence: 68%

Experimental supersonic combustion research at NASA Langley

Rogers

Capriotti

Guy

1998

20th AIAA Advanced Measurement and Ground Testing Technology Conference

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“…In previous studies of H 2 -air and HC-air systems, flame restoration was found independent of jet diameter, and a large hysteresis in exit velocity existed between extinction and restoration [16][17][18][19][20][21]. It was concluded that flame restoration occurs as a velocity-limited piloted-reignition along a thin stagnated region containing inter-diffused jet flows; or, when the inward "stretched laminar burning velocity" finally exceeds the maximum outward radial velocity [21].…”

Section: Steady State Flame Strength Measurementsmentioning

confidence: 89%

“…To obtain steady-state extinction of a CFDF, the mass flows of fuel mixture and air are slowly increased simultaneously, so the disk flame, located primarily on the airside, is always centered and free-floating [16][17][18][19][20][21]. Manual control of flame centering is monitored visually, and also through a TV display from a horizontally oriented focusing schlieren system [18].…”

Section: Steady State Flame Strength Measurementsmentioning

confidence: 99%

“…Hence mass inflow measurements are unaffected by local variations in gas velocity caused by jet temperature variations, and resultant "density-weighted" extinction limits have been found independent of such linear variations in gas velocity up to ~ 600 K [21]. Thus potential data scatter due to temperature variation is effectively nulled, which is especially helpful when heated fuel jets are required [17]. However, variations in atmospheric pressure do affect the data slightly.…”

Section: Dynamic Flame Strength Measurementsmentioning

confidence: 99%

“…The few known experimental studies have emphasized detailed nonintrusive measurements of species, temperature, and velocity, and resultant axial strain rates in methane-air and propane-air systems at relatively low frequencies [10,[13][14][15]. This paper presents an idealized experimental study of four gaseous hydrocarbon-air systems, using an Oscillatory-input convergent-nozzle Opposed Jet Burner (OOJB) system developed from earlier steady-state studies [16][17][18][19][20][21]. It features a substantially improved analysis of the ethylene-air and methane-air dynamic extinction data presented in our previous paper, AIAA-2003-4634 [26], and it also contains new sets of ethane-air and propane-air data that exhibit intermediate behavior.…”

Section: Introductionmentioning

confidence: 99%

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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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Thermal and Kinetic Impact of CO, CO₂, and H₂O on the Postoxidation of IC-Engine Exhaust Gases

Anderlohr¹,

Cruz²,

Bounaceur³

et al. 2010

Combustion Science and Technology

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The thermal and kinetic impact of the residual species CO, CO 2 , and H 2 O on hydrocarbon (HC) oxidation chemistry was investigated numerically. The case of pure dilution by N 2 was tested against a dilutant composed of CO, CO 2 , and H 2 O in proportions corresponding to internal combustion (IC)-engine Postoxidation conditions (at the end of the expansion stroke and throughout exhaust). The impact of each residual species was tested individually, as well as in combination with others. Attention was given to the thermal impact, kinetic impact and third-body effects of each residual. In the cases of CO 2 and H 2 O, a negative thermal C p -effect in competition with an accelerating kinetic impact due to third-body reactions was observed. The influence of CO on HC-oxidation is restricted to its direct participation in oxidizing reactions, and its thermal impact is negligible compared to N 2 . CO 2 and H 2 O have a negative thermal impact compared to N 2 , resulting from their increased heat capacities. Kinetically, they interact as collision partners with HC-oxidation through H 2 O 2 -dissociation. Generally, it was shown that the composition of a dilutant strongly impacts HC-oxidation and that the presence of CO 2 and mainly H 2 O may lead to an acceleration of HC-oxidation, in spite of their unfavorable thermal properties compared to N 2 .

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Strain-induced extinction of hydrogen-air counterflow diffusion flames - Effects of steam, CO2, N2, and O2 additives to air

Cited by 12 publications

References 10 publications

Experimental supersonic combustion research at NASA Langley

Experimental supersonic combustion research at NASA Langley

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

Thermal and Kinetic Impact of CO, CO₂, and H₂O on the Postoxidation of IC-Engine Exhaust Gases

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Strain-induced extinction of hydrogen-air counterflow diffusion flames - Effects of steam, CO2, N2, and O2 additives to air

Cited by 12 publications

References 10 publications

Experimental supersonic combustion research at NASA Langley

Experimental supersonic combustion research at NASA Langley

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

Thermal and Kinetic Impact of CO, CO2, and H2O on the Postoxidation of IC-Engine Exhaust Gases

Contact Info

Product

Resources

About

Thermal and Kinetic Impact of CO, CO₂, and H₂O on the Postoxidation of IC-Engine Exhaust Gases