Diffusion controlled combustion of polymers

Holve, D. J.; Sawyer, Robert F.

doi:10.1016/s0082-0784(75)80310-9

Cited by 31 publications

(16 citation statements)

References 10 publications

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“…But since the flame lengths do not change with time (for pool fires with fixed diameters), the loss terms remain constant, and the B-number calculated is a constant. A similar study by Holve and Sawyer [22] where the B-number is measured by burning solid fuels in a counter flow burner configuration also results in a constant Bnumber. Orloff et al [23] measured the radiative losses of turbulent flames and include this effect in their calculation of the B-number.…”

Section: Introductionmentioning

confidence: 55%

“…A more realistic mass transfer number, will have χ and Q, in its formulation and is useful in predicting the flammability of a material in a realistic fire scenario. Previous experimental calculations of the B-number in the literature [19,[21][22][23][24] have always assumed the loss term Q in the denominator as a constant, resulting in a B-number that does not change with time (Table 1). Kanury [21] measured the radiation losses, and accounted for them in the B-number, when burning solid pool fires under various oxygen concentrations.…”

Section: Introductionmentioning

confidence: 99%

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Flame Spread Analysis Using a Variable B-Number

Rangwala¹

2008

Fire Saf. Sci.

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Flame spread over solid materials is commonly described in the literature by a two-dimensional reactive boundary layer solution first formulated by Emmons (1956). In the recent past, experimental measurements associated with material flammability testing (e.g. NASA-STD-6001) are compared with the Emmons solution, as modified by Pagni and Shih (1979), and found in disagreement. In the classical solution, the B-number (Spalding mass transfer number) appears as one of the boundary conditions, and has been traditionally assumed a constant for mathematical simplicity. However, experimental results show that the B-number is not a constant, but varies with time and space. A simple modification to the standard measurement procedure is described, which allows calculation of the B-number from the flame stand-off distance. Measurements of flame standoff distance are performed to determine the B-number as a function of time. The classical combustion problem is revisited to model flame spread over a combustible surface. An experimentally-obtained B-number is used to model flame propagation, showing good agreement with current and previous experimental data obtained from the literature. Implications to microgravity flame spread are discussed.

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Section: Introductionmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Flame Spread Analysis Using a Variable B-Number

Rangwala¹

2008

Fire Saf. Sci.

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“…Numerous studies have been conducted in the past which deals with flame spread or counterflow diffusion flame, stating that the parameter affecting the regression rate of solid fuel can be non-dimensionalized with the use of the gas phase Damköhler number (Holve and Sawyer, 1975), , , (Krishnamurthy, 1975), (Matsui, et al, 1975), (Matsui and Tsuji, 1976), (Pello, et al, 1981), (Tsuji, 1982), (Wichman, et al, 1982). In these studies, the physical parameters included within the gas phase Damköhler number are assumed to express the effects imposed on the regression rate.…”

Section: Previous Studies With Solid Fuel Combustionmentioning

confidence: 99%

“…In comparison, research with solid Effect of combustion pressure on regression rate of solid fuel under an impinging oxidizer jet counterflow diffusion flame fuel -impinging oxidizer jet opposed flow diffusion flame, or the so called counterflow diffusion flame, has investigated the effects of oxidizer nitrogen dilution and oxidizer flux (Tsuji and Matsui, 1976). Earlier experiments conducted by Tsuji (Tsuji, 1982) and Holve (Holve and Sawyer, 1975) have confirmed the effects of forced oxidizer flow on the regression rate of a PMMA solid fuel, while Krishnamurthy (Krishnamurthy, 1975) has investigated in detail the mechanics behind flame extinction in the stagnation point of a counterflow flame. These studies propose a method to predict the regression rate of the fuel surface using a given oxidizer flow condition.…”

Section: Previous Studies With Solid Fuel Combustionmentioning

confidence: 99%

Effect of combustion pressure on regression rate of solid fuel under an impinging oxidizer jet counterflow diffusion flame

Terakawa

Saito

Nakamura

et al. 2014

JTST

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Flame spread and counterflow diffusion flame experiments are widely conducted to investigate the combustibility of solid fuels. Although the use of the gas phase Damköhler number to organize the flame spread rate or regression rate of a solid fuel is effective under constant pressure, some research point out the possibility that the combustion pressure may be an independent factor in determining the regression rate. This research employs a counterflow diffusion flame to investigate the effects of combustion pressure on regression rate, and clarifies the deviation of results using the classical Damköhler number under varying pressures. First, a numerical flow analysis was conducted to determine the oxidizer velocity gradient near the fuel surface, which is an essential factor in evaluating the non-dimensional regression rate. Next, using an enclosed combustion chamber with independently variable oxidizer flux and pressure, experiments with a quasi two-dimensional flame were conducted with polyethylene solid fuel and nitrogen diluted oxygen oxidizer, and the regression rate was measured for two experiment series, constant pressure, and constant oxidizer flux. By comparing the two series, the effect of pressure on non-dimensionalized regression rate is clarified. The results suggest that contrary to the theoretical reaction rate of the gas phase, the non-dimensional regression rate increases when the combustion pressure is decreased, even in the thermal regime. This suggests that the classic method of organizing the regression rate with Damköhler number in thermal regime could not be implemented with varying pressure conditions, possibly due to the change in diffusion rates involved with varying pressures.

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“…The relatively simple, quasi-one-dimensional nature of diffusion flames in lamanar stagnation-point flows has encouraged analyses [1][2][3][4][5][6][7][8][9] of that system. Motivated by the importance of flame radiation to fire safety [10], the present study extends previous work [8,11] to the opposed flow diffusion flame apparatus, where proper determination of material properties from experimental data requires quantification of the net radiative effect on heat transfer at the pyrolyzing surface.…”

Section: Introductionmentioning

confidence: 99%