Abstract
An analogue experiment is proposed to simulate flame flickering comprising a free ascending column fed on its side with a light gas (helium) emerging from a vertical slot in ambient air. The convective motion of the helium jet is considered to represent the motion of burnt gases of buoyant jet flames. The helium jet is accelerated by buoyancy effects and the flow field is similar to that of burnt gases observed for real buoyant flames. The vertical velocity profile of the steady helium jet is measured at different vertical distances. The unsteady helium jet is also studied by measuring the instability frequency as a function of ambient pressure at different injection flow rates, and by analyzing the tomography images of the helium jet. The instability morphology is the same as that observed on real buoyant flames. We conclude that this type of instability can be approximately characterized by the maximum vertical velocityu max, and the distance δ betweenu max in the helium ascending column andu = o in the ambient air. For this type of instability the local vorticity is proportional to\(\frac{{u_{\max } }}{\delta }\) which can be influenced by gravity and ambient pressure. Theoretical prediction of the instability frequency as a function of gravity and ambient pressure has been obtained, and is in good agreement with the experimental results.
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Abbreviations
- C 1,C 2 :
-
constants
- F :
-
instability frequency
- F c :
-
critical frequency
- F m :
-
the most amplified frequency
- F (K, ε):
-
function defined in (11)
- g :
-
gravitational acceleration
- g′:
-
reduced gravity acceleration g(σ0-σ*)/σ*
- k :
-
real wave number of the disturbance
- K :
-
reduced wave numberK=2kδ
- K c :
-
reduced wave number of the critical instability mode
- K m :
-
nondimensional wavenumber of the most amplified mode
- L :
-
vertical characteristic length (in x direction)
- P :
-
ambient pressure
- u :
-
local vertical buoyant velocity (inx direction)
- u max :
-
local maximum vertical velocity
- v :
-
local velocity component iny direction (horizontal)
- V 0 :
-
injection velocity of helium (iny direction)
- x :
-
vertical distance measured from the leading edge of boundary layer
- y :
-
horizontal distance measured from the exit plane of the vertical slot
- Z(K, ε):
-
function defined in equation (11)
- δ:
-
distance betweenu max in the helium ascending column andu = o in the ambient air
- ε:
-
\(\varepsilon = \frac{{\rho _0 - \rho ^* }}{{\rho _0 + \rho ^* }}\)
- λ:
-
wavelength of instability
- λ c :
-
critical wavelength
- λ m :
-
the most amplified wavelength
- σ* :
-
helium density at slot exit
- σ0 :
-
ambient air density
- μ* :
-
helium dynamic viscosity at slot exit
- v * :
-
helium kinematic viscosity at slot exit
- ω:
-
complex number presented in disturbancee i(kx+ωt)
- ω i :
-
imaginary part of ω, representing the amplification rate of disturbance
- ω r :
-
real part of ω, where (ω r /k) represents the group velocity
- μ:
-
reduced complex number of ω, defined\(\Omega = \frac{\omega }{{ku_{max} }}\)
References
Buckmaster J; Peters N (1986) The infinite candle and its stability — a paradigm for flickering diffusion flame. Twenty-First Symp. (Intern.) on Combustion/The Combustion Institute, 1829–1836
Cetegen B; Ahmed T (1993) Experiments on the periodic instability of buoyant plumes and pool fires. Combustion and Flame 93: 157–184
Chandrasekhar S (1961) Hydrodynamic and hydromagnetic stability. Oxford at The Clarendon Press, 481–494
Chen L-D; Faeth GM (1982) Ignition of supercritical fluids during natural convection from a heated vertical surface. Combustion and Flame 44: 169–183
Chen L-D; Seaba JP; Roquemore WM; Goss LP (1988) Buoyant diffusion flames. Twenty-second symp. (Intern.) 0n Combustion/The Combustion Institute, 677–684
Chen L-D; Vilimpoc V; Goss LP; Davis RW; Moore EF; Roquemore WM (1992) Time evolution of a buoyant jet diffusion flame. Twenty-Fourth Symp. (Intern.) on Combustion/The Combustion Institute, 303–310
Davis RW, Moore EF; Roquemore, WM; Chen L-D Vilimpoc V; Goss LP (1990) Preliminary results of a numerical/experimental study of the dynamic structure of a buoyant jet diffusion flame. Combustion and Flame 83: 263–270
Delichatsios MA (1986) A simple algebraic model for turbulent wall fires. Twenty-First Symp. (Intern.) on Combustion/The Combustion Institute, 53–64
Durox D; Yuan T; Villermaux E (1992) Influence of gravity and ambient pressure variations on the behaviour of buoyant laminar diffusion flame. VIIIth European Symposium on Materials and Fluid Sciences in Microgravity, 12–16 April, Brussels
Ellzey JL; Laskey KJ; Oran ES (1991) A study of confined diffusion flames. Combustion and Flame 84: 249–264
Gebhart B (1973) Instability, transition, and turbulence in buoyancy-induced flows. Annual Rev. Fluid Mechanics
Grant AJ; Jones JM (1975) Low-frequency diffusion flame oscillations. Combustion and Flame 25: 153–160
Hamins A; Yang JC; Kashiwagi T (1992) An experimental investigation of the pulsation frequency of flames. Twenty-Fourth Symp. (Intern.) on Combustion/The Combustion Institute, 1695–1702
Hosangadi A; Merkle CL; Turn SR (1990) Analysis of forced combustion jets. AIAA Journal, vol 28, No. 8, August, 1473–1480
Katta VR; Goss LP; Roquemore WM (1992) Numerical investigation on the dynamic behaviour of a H2-N2 diffusion flame under the influence of gravitational force. AIAA Paper 92-0335, 30th Aerospace Sciences Meeting & Exhibit, January 6–9, Reno, NV
Kimura I (1965) Stability of laminar-jet flames. Tenth Symp. (Intern.) on Combustion/The Combustion Institute 1295–1300
Mahalingam S; Cantwell BJ; Ferziger JH (1990) Full numerical simulation of coflowing axisymmetric jet diffusion flames. Phys Fluids A2 (5) May, 720–728
Mahalingam S; Cantwell BJ; Ferziger JH (1991) Stability of low-speed reacting flows. Phys Fluids A 3(6), June 1533–1543
Mollendorf JC; Gebhart B (1973) An experimental and numerical study of the viscous stability of a round laminar vertical jet with and without thermal buoyancy for symmetric and asymmetric disturbances. J Fluid Mech 61: 367–399
Monkewitz PA; Bechert DW; Barsikow B; Lehmann B (1990) Self-excited oscillations and mixing in a heated round jet. J Fluid Mech 213: 611–639
Parikh PG; Moffat RJ; Kays WM; Bershader D (1974) Free convection over a vertical plate with transpiration. Int J Heat Mass Transfer 17: 1465–1474
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Yuan, T., Durox, D. & Villermaux, E. An analogue study for flame flickering. Experiments in Fluids 17, 337–349 (1994). https://doi.org/10.1007/BF01874414
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DOI: https://doi.org/10.1007/BF01874414