Theoretical Analysis on Flame Stabilization by a Bluff-Body

Kundu, Krishnendu; Banerjee, Debanjan; Bhaduri, D.

doi:10.1080/00102207708946825

Cited by 47 publications

(29 citation statements)

References 3 publications

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“…In addition, Kundu et al's. [100,101] measurements show a monotonic reduction of temperature in the recirculation zone as the flow velocity increases toward its blowoff value. They found that the ratio of wake to adiabatic flame temperature decreased from 0.94 to 0.88 as U/U LBO increased from 0.3 to 0.9.…”

Section: Discussionmentioning

confidence: 93%

“…Since entrainment rates scale as D/U (see Section 2.2.2) then it follows that this criterion reduces to a Damkö hler number blowoff criterion, using a chemical time that is derived from the well stirred reactor, s PSR . A similar idea relates to an energy balance between heat supplied by the hot recirculating flow to the fresh gases and that released by reaction [98,[100][101][102]. In this view, blowoff occurs when the heat required by the combustible stream exceeds that received from the recirculation zone.…”

Section: Discussionmentioning

confidence: 98%

See 1 more Smart Citation

Lean blowoff of bluff body stabilized flames: Scaling and dynamics

Shanbhogue

Husain

Lieuwen

2009

Progress in Energy and Combustion Science

543

206

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 98%

Lean blowoff of bluff body stabilized flames: Scaling and dynamics

Shanbhogue

Husain

Lieuwen

2009

Progress in Energy and Combustion Science

543

206

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“…The total mass flow rate of air contained in the freestream is not appropriate because this flow rate can be made arbitrarily large by increasing the height of the freestream above the recirculation zone, and this height is not a relevant parameter. Winterfeld 6 and Kundu et al 4 present data showing that the air mass flow rate entrained into a recirculation zone behind a bluff body of height H and width W is proportional to ρ A U A H W . Therefore, following the convention set by Winterfeld, 7 the characteristic air mass flow rate is defined as…”

Section: Correlation Of Blowout Limits For Nonpremixed Flamesmentioning

confidence: 97%

Correlation and Analysis of Blowout Limits of Flames in High-Speed Airflows

Driscoll

Rasmussen

2005

Journal of Propulsion and Power

107

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This work identifies a scaling parameter (which is a modified Damkohler number) that is found to correlate the flame blowout limits that were measured in six previous studies of nonpremixed flames which were stabilized in high-speed airflows by wall cavities, bluff bodies, and struts. Understanding the scaling of the combustor is needed to select the correct height of a cavity or step flameholder for ramjets, scramjets, or afterburners. This work focuses on nonpremixed conditions that occur when fuel is injected directly into a wall cavity or behind a strut, as is done with new designs. Thus, the Damkohler number that is identified is different from of that of Zukoski and Ozawa, who considered the different case of premixed flames in afterburners. Nonpremixed conditions introduce a new parameter that is not relevant for premixed conditions: the location of the fuel injector with respect to the recirculation zone. An analysis of a shear layer was performed in order to derive equations for the appropriate Damkohler number. Using this result, approximately 100 measured values of blowout limits from six previous studies were plotted, and a best-fit correlation curve that has a rich limit branch and a lean limit branch was determined. Although this correlation result provides a general estimate of blowout limits, it also indicates that additional research is needed to reduce the scatter in the correlation by improving the model of entrainment into the recirculation zone and by including unsteady effects. The results show that a reasonable correlation is achieved using the concept that the propagation speed of the flame in the shear layer is matched to the velocity of the local incident gas flow. Hot products in the recirculation zone preheat the shear-layer gases and increase the propagation speed of the flame. The analysis avoids an assumption that has been used previously-that the residence time of reactants in a "well-stirred" homogeneous reaction zone is matched to a global chemical reaction time. Experimental justification of the present approach is presented. NomenclatureDa NP = critical Damkohler number at flame blowout, for nonpremixed conditions Da P = critical Damkohler number at flame blowout, for premixed conditions [Eq. (1)] f = mixture fraction (defined in Ref. 33) H = step height (Fig. 1) h = liftoff distance in x direction L RZ = recirculation zone length M A = Mach number of airstream m A = characteristic air mass flow rate [Eq. (3)] m F = fuel mass flow rate R = velocity ratio U RZ /U A r s = stoichiometric fuel-air ratio S base = propagation speed of base of the lifted flame S 0 = stoichiometric laminar burning velocity at 300 K, 1 atm s = density ratio ρ RZ /ρ A T = static temperature T F = fuel-injection temperature T 0 = stagnation temperature U = axial velocity of gas W = spanwise width of step x = streamwise distance Y P,RZ = mass fraction of products in recirculation zone α 0 = thermal diffusivity of fuel-air mixture at 300 K, 1 atm β = empirical constant δ A = shear-layer thickness ε = mixing...

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“…Spalding [10] and Kundu et al [11] studied the role of the recirculation zone on blowout criteria. Nicholson and Field [12] and Chao et al [13] reported increased flame detachment and reattachment events near blowout.…”

Section: Blowout Phenomenonmentioning

confidence: 99%

Real-time prediction of lean blowout using chemical reactor network

Kaluri

Malte

Novosselov

2018

Fuel

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The lean blow-out (LBO) of gas turbine combustors is a concern that can limit the rate of descent for an aircraft, the maneuverability of military jets, and cause a costly and time-intensive reignition of land-based gas turbines. This work explores the feasibility of a model-based combustor monitoring for the real-time prediction of combustion system proximity to LBO. The approach makes use of (1) iv

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Theoretical Analysis on Flame Stabilization by a Bluff-Body

Cited by 47 publications

References 3 publications

Lean blowoff of bluff body stabilized flames: Scaling and dynamics

Lean blowoff of bluff body stabilized flames: Scaling and dynamics

Correlation and Analysis of Blowout Limits of Flames in High-Speed Airflows

Real-time prediction of lean blowout using chemical reactor network

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