Non-dimensional correlations on flame height and axial temperature profile of a buoyant turbulent line-source jet fire plume

2014 ◽  
Vol 32 (5) ◽  
pp. 406-416 ◽  
Author(s):  
Xiaochun Zhang ◽  
Longhua Hu ◽  
Xiaolei Zhang ◽  
Lizhong Yang ◽  
Shuangfeng Wang
2015 ◽  
Vol 5 (9) ◽  
pp. 2024
Author(s):  
Zhiwen Pan ◽  
Jens Kobelke ◽  
Kay Schuster ◽  
Hartmut Bartelt

2001 ◽  
Author(s):  
Hayden M. Reeve ◽  
Ann M. Mescher ◽  
Ashley F. Emery

Abstract The transient heating of a polymer preform within a cylindrical furnace is the initial step in the manufacture of polymer optical fiber. A numerical model was used to simulate the radiative and convective heat transfer within the furnace enclosure during this initial heating. Results illustrate a strong dependence of the preform’s heating rate on the radiative properties of the preform. Due to the prominence of radiative heat transfer at steady-state, the resulting axial temperature profile within the preform is strongly coupled to the corresponding axial temperature profile of the furnace wall. Numerical predictions were compared with experimental results for several preform surface emissivities, preform diameters, and thermal boundary conditions. The results compare well for preforms with well-characterized surface finishes (such as black paint and aluminum), with discrepancies between experimental and numerical results typically less than 1.3°C. Experiments indicate that the heating characteristics of poly(methyl methacrylate) preforms can be adequately simulated by assuming that the preform exhibits nearly blackbody behavior (ε = 0.96) when exposed to the low furnace temperatures (85°C) used in this study. Finally, the experiments revealed the tendency for unstable natural convection within tall furnace cavities, with experimental readings indicating oscillatory air temperatures as the system approached steady-state.


2019 ◽  
Vol 37 (3) ◽  
pp. 236-256 ◽  
Author(s):  
Xuehui Wang ◽  
Tiannian Zhou ◽  
Qinpei Chen ◽  
Junjiang He ◽  
Zheng Zhang ◽  
...  

Liquid–vapor phase equilibrium theories are used to analyze boiling processes of blended fuel pool fires, and the results show that there are two boiling mechanisms (azeotropism and non-azeotropism) for blended fuels compared with single-component fuels. A series of pool fire experiments were conducted to investigate the combustion characteristics of blended fuel pool fires. The experimental results showed that the two boiling mechanisms have different effects on the burning process of the fuel blends. The boiling temperature and composition varied for the non-azeotropic blends during the burning process and remained steady for azeotropic blends. Furthermore, the boiling temperature of azeotropic blends is lower than that of its components and ranges from a specific temperature to the boiling point of the less volatile component. The flame radiant fraction of the azeotropic blend was also relatively constant during the burning process, whereas that of the non-azeotropic blend varied in different stages of the burning process. Heskestad’s flame height model and flame axial temperature distribution model are applicable for pool fires of azeotropic and non-azeotropic blends.


2003 ◽  
Author(s):  
Elizabeth J. Weckman ◽  
Cecilia S. Lam ◽  
Jennifer E. Weisinger ◽  
Walter Gill ◽  
Alexander L. Brown

Macroscopic fire parameters such as fuel regression rate, flame height and flame tilt are critical to the development of detailed fire models and empirical tools for hazard analysis [1–3]. As a result, these characteristics have been investigated by many researchers using various measurement methods in studies of liquid fuelled pool fires of different diameters and fuel types, under a range of crosswind conditions. In investigations related to transportation accidents, fire scenarios have been complicated further through interactions between the fire and upwind or downwind objects [1,2]. Of particular interest is the determination of fuel regression rate, an important parameter but one that is generally difficult to characterize accurately. Many techniques have been reported for measurement of fuel regression rate. These include load cells [2,4,5], differential pressure systems [2,5–7], sight glass and float-type level meters [6–8] and thermocouple rakes [1]. In general, load cells have been employed most successfully for measurements in smaller scale fires [2,4], while researchers have turned to differential pressure and thermocouple type systems for measurements in fires above 5 m diameter [2,6,7]. All the techniques have been used with varying levels of success to measure fuel regression rate under quiescent conditions. Under crosswind conditions and in cases with an object present, however, inherent wandering of the fire plume and dynamic wind loading on the pool can be of additional concern as they affect the accuracy and repeatability of the measurements [1,2,6,7]. In several excellent reviews, available results have been summarized and used to derive empirical correlations relating overall fire characteristics to fire diameter, fuel type and/or wind velocity [3,9–11].


Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 935 ◽  
Author(s):  
Dariusz Szeliga ◽  
Waldemar Ziaja ◽  
Maciej Motyka ◽  
Krzysztof Kubiak ◽  
Jan Sieniawski

The technique of flattening the temperature profile and controlling the formation of both the dendritic microstructure and grain structure in the directional solidification of nickel-based superalloy casting, using the novel inner radiation baffles (IRBs) in the Bridgman process, is presented in this paper. These baffles matched to the shape of mold and were placed horizontally along its height at various distances from the casting base. The plate castings of CMSX-4 superalloy were fabricated without and with the use of IRBs, withdrawing the mold at the rate of 6 mm/min from the heating to the cooling area of the industrial Bridgman furnace. Thermal analysis of the directional solidification of castings was carried out using the ProCAST software for a process where the various designs of the radiation baffle were applied. The results of the solidification conditions, the shape of liquidus and solidus isotherms, and grain structure obtained for the IRBs were compared with those reached for the standard ring-shaped (AERB) or perfectly adjusted (PARB) radiation baffles. The use of IRB resulted in flattening of the temperature distribution and decrease of the curvature of liquidus and solidus isotherms, as well as an increase of temperature gradient and cooling rate, compared with the process where AERB was only used. Consequently, primary dendrite arm spacing (PDAS) reached similar values across the width of casting and equaled to approximately 370 μm, reducing its average value by 26%, compared with the standard process. The change in predicted axial temperature gradient in casting was not found when thermophysical properties of molybdenum IRBs were used. The increase in graphite IRBs number in mold from seven to 14 caused the reduction of inhomogeneity of axial temperature gradient along the casting height.


Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1460
Author(s):  
Ruibang Sun ◽  
Xing Yang ◽  
Juncai Wang ◽  
Peng Chen ◽  
Liusuo Wu

With the widespread use of substations around the world, oil jet fire accidents from transformer oil-filled equipment in substations caused by faults have occurred from time to time. In this paper, a series of transformer oil jet fire experiments are carried out by changing the external heat source (30 cm and 40 cm) and the inner diameter of the container (5 cm, 8 cm and 10 cm) to study the axial centerline temperature distribution of the transformer oil jet fire plume of the transformer oil-filled equipment in the substation. The experiment uses K-type thermocouple, electronic balance and CCD to measure and assess the temperature distribution of the axial centerline of the fire plume of the transformer oil jet. The result demonstrates that the axial centerline temperature of the fire plume increases with the external heat release rate and the inner diameter of the container. In addition, a novel axial temperature distribution prediction model of the transformer oil jet fire plume is established. This model can effectively predict the oil jet fire plume temperature of transformer oil- filling equipment in substations, and provide help for substation fire control.


2018 ◽  
Vol 36 (4) ◽  
pp. 362-375 ◽  
Author(s):  
Cong Li ◽  
Rui Yang ◽  
Yina Yao ◽  
Zhenxiang Tao ◽  
Hui Zhang

This article presents an experimental investigation on the pool fire plume characteristics in a full-scale depressurized aircraft cargo compartment. The effects of decreasing pressure and vent flow rate on the fire characteristics such as flame shape, flame puffing, flame height, and centerline temperature were analyzed. The results show that during the depressurization process, the ventilation had an activation effect on the mass loss rate, and its increment had a linear relationship with the dimensionless ventilation factor. In addition, the larger depressurized rate caused the larger dimensionless ventilation factor and further resulted in the larger increment of mass loss rate. The flame puffing frequency was determined by the ratio of the gas density in the flame area of that in the ambient air, which increased with the drop of pressure. For flame centerline temperature, there was a counteraction area in the flame intermittent region, where the centerline temperature had almost no difference before and after the depressurization. The conclusions could provide the theoretical base and reference materials for the fire disaster in the cargo compartment of real aircrafts.


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