Flame-Spread Behavior of Fuel-Droplet Arrays With Uneven Inter-Droplet Distance at High Temperature in Microgravity

2007 ◽  
Author(s):  
Kazuki Yagi ◽  
Hisashi Shigeno ◽  
Hiroshi Oyagi ◽  
Mikami Masato ◽  
Naoya Kojima
Keyword(s):  
High Temperature ◽  
Combustion Chamber ◽  
Waiting Time ◽  
Flame Spread ◽  
Room Temperature ◽  
Fuel Droplet ◽  
Hot Wire ◽  
Spread Rate ◽  
Flame Spread Rate ◽  
Droplet Array

This research experimentally studied flame-spread behavior of fuel-droplet arrays with uneven inter-droplet distance at high temperature in microgravity. In experiments, first, n-decane droplets were generated in room-temperature air. Next, the droplet array was inserted into the combustion chamber with 600 K air. The droplet array was ignited at one end by a hot wire igniter after a certain waiting time to initiate the flame spread. Local inter-droplet distances were varied to investigate the effect of droplet interaction on local flame-spread-limit distance. Waiting time for ignition was varied to investigate the prevaporization effect on flame spread. Experimental results showed that as the inter-droplet spacing became smaller, local flame-spread-limit distance to the next droplet became larger. The local flame-spread-limit distance at high temperature was larger than that at room temperature. Flame-spread rate from the interactive droplets to the next droplet was greater with longer waiting time for ignition.

High-Pressure Combustion Phenomena

2007 ◽  
Author(s):  
Hideaki Kobayashi
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Flame Spread ◽  
Burning Velocity ◽  
Premixed Flames ◽  
Spread Rate ◽  
Flame Spread Rate ◽  
Droplet Array ◽  
Turbulent Burning Velocity ◽  
Turbulent Premixed

Two high-pressure combustion phenomena recently observed by the author’s group are reviewed. The first one is the flame spread of a droplet array in the supercritical pressure range of the fuel in microgravity. Microgravity experiments are essential for research on droplet combustion, especially at high pressure, because of the large Grashof number in normal gravity. The flame spread rate for an n-decane droplet array was measured at high pressure, and a fuel-vapor jet was found to be generated due to an imbalance of surface tension of the droplet surface, leading to a higher flame spread rate. The second phenomenon is turbulent premixed combustion at high pressure and high temperature, environmental conditions of which are very close to those in SI engines and premixed-type gas turbine combustors. Information on the flame characteristics in such conditions has been very limited. A high-pressure combustion test facility with a large high-pressure combustion chamber enabled us to stabilize turbulent premixed flames with a high turbulence Reynolds number and to perform flame observations and measurements for extended period using lasers. Turbulent burning velocity was successfully measured and significant effects of intrinsic flame instability on flame structure and turbulent burning velocity at high pressure were revealed. Effects of CO2 dilution on high-pressure and high-temperature premixed flames were also investigated to evaluate the fundamental effects of exhaust gas recirculation (EGR) in practical high-load high-pressure combustors.

scholarly journals Thermodynamic and Kinetic Characteristics of Combustion of Discrete Polymethyl Methacrylate Plates with Different Spacings in Concave Building Facades

Polymers ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 167
Author(s):  
Weiguang An ◽  
Lujun Peng ◽  
Minglun Cai ◽  
Kaiyang Hu ◽  
Song Li ◽  
...  
Keyword(s):  
Polymethyl Methacrylate ◽  
Flame Spread ◽  
Structure Factor ◽  
Turning Point ◽  
Fire Risk ◽  
Flame Height ◽  
Hazard Evaluation ◽  
Spread Rate ◽  
Building Facades ◽  
Flame Spread Rate

Polymethyl methacrylate plates are widely applied to buildings, producing significant fire hazards. It lacks a theoretical basis for the fire risk assessment of polymethyl methacrylate in concave building facades. Therefore, experimental methods are used to investigate combustion characteristics of discrete polymethyl methacrylate plates in a concave building facade. Influences of fuel coverage and structure factor are investigated, which is scant in previous works. When structure factor is invariable, average flame height increases first and then decreases as fuel coverage increases, and the turning point is between 0.64 and 0.76. In total, three different patterns of pyrolysis front propagation are first observed for different fuel coverages. Flame spread rate first increases and then decreases as fuel coverage rises, and the turning point is also between 0.64 and 0.76. When fuel coverage is invariable, the flame spread rate first increases and then decreases with increasing structure factor, and the turning point is 1.2. A model for predicting the flame spread rate of discrete polymethyl methacrylate is also developed. The predicted values are consistent with experimental results. Fuel spread rate of discrete polymethyl methacrylate rises as the fuel coverage increases. The above results are beneficial for thermal hazard evaluation and fire safety design of polymethyl methacrylate used in buildings.

Effect of Sample Width on Downward Flame Spread over Typical Energy Conservation Material at a High Elevation Area

2014 ◽  
Vol 664 ◽  
pp. 199-203 ◽  
Author(s):  
Wei Guang An ◽  
Lin Jiang ◽  
Jin Hua Sun ◽  
K.M. Liew
Keyword(s):  
Mass Loss ◽  
Flame Spread ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
High Elevation ◽  
Flame Height ◽  
Spread Rate ◽  
Flame Spread Rate ◽  
Sample Width ◽  
Downward Flame Spread

An experimental study on downward flame spread over extruded polystyrene (XPS) foam at a high elevation is presented. The flame shape, flame height, mass loss rate and flame spread rate were measured. The influences of width and high altitude were investigated. The flame fronts are approximately horizontal. Both the intensity of flame pulsation and the average flame height increase with the rise of sample width. The flame spread rate first drops and then rises with an increase in width. The average flame height, mass loss rate and flame spread rate at the higher elevation is smaller than that at a low elevation, which demonstrates that the XPS fire risk at the higher elevation area is lower. The experimental results agree well with the theoretical analysis. This work is vital to the fire safety design of building energy conservation system.

Experimental study of moisture content effects on horizontal flame spread over thin cotton fabric

2018 ◽  
Vol 89 (15) ◽  
pp. 3189-3200 ◽  
Author(s):  
Yunji Gao ◽  
Guoqing Zhu ◽  
Hui Zhu ◽  
Weiguang An ◽  
Yu Xia
Keyword(s):  
Moisture Content ◽  
Cotton Fabric ◽  
Flame Spread ◽  
Extreme Values ◽  
Ignition Time ◽  
Convective Heat Transfer Coefficient ◽  
Flame Height ◽  
Spread Rate ◽  
Untreated Cotton ◽  
Flame Spread Rate

In this paper, moisture content effects on horizontal flame spread were experimentally investigated using 0.245 mm thick, 28 cm tall and 28 cm wide untreated cotton fabric sheets with various moisture contents varying from 0 to 34%. The pyrolysis spread rates, flame heights and ignition times were obtained and analyzed. The corresponding results are as follows: as moisture content increases, the flame height and spread rate first increase and then decrease. In contrast, the ignition time shows an opposite trend with moisture content. The extreme values are observed in cases of 2% moisture content samples. Moreover, the flame spread rate in the warp direction is larger than that in the weft direction. For horizontal flame spread, the moisture content has the effect of consuming part of the heat feedback, which can play a role in reducing the flame spread rate; simultaneously, the moisture content can enlarge flame size and increase the convective heat transfer coefficient, thereby resulting in an increase in flame spread rate. The non-monotonous trend in pyrolysis spread rate is the result of competition between these effects.

Numerical Study of the Effects of Confinement on Concurrent-Flow Flame Spread in Microgravity

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Yanjun Li ◽  
Ya-Ting T. Liao ◽  
Paul Ferkul
Keyword(s):  
Flame Spread ◽  
Numerical Study ◽  
Flame Temperature ◽  
Combustion Model ◽  
Conductive Heat ◽  
Spread Rate ◽  
Transient Model ◽  
Concurrent Flow ◽  
Flame Spread Rate ◽  
Flow Duct

Abstract The objective of this work is to investigate the aerodynamics and thermal interactions between a spreading flame and the surrounding walls as well as their effects on fire behaviors. A three-dimensional transient computational fluid dynamics (CFD) combustion model is used to simulate concurrent-flow flame spread over a thin solid sample in a narrow flow duct. The height of the flow duct is the main parameter. The numerical results predict a quenching height for the flow duct below which the flame fails to spread. For duct heights sufficiently larger than the quenching height, the flame reaches a steady spreading state before the sample is fully consumed. The flame spread rate and the pyrolysis length at steady-state first increase and then decrease when the flow duct height decreases. The detailed gas and solid profiles show that flow confinement has multiple effects on the flame spread process. On one hand, it accelerates flow during thermal expansion from combustion, intensifying the flame. On the other hand, increasing flow confinement reduces the oxygen supply to the flame and increases conductive heat loss to the walls, both of which weaken the flame. These competing effects result in the aforementioned nonmonotonic trend of flame spread rate as duct height varies. Near the quenching duct height, the transient model reveals that the flame exhibits oscillation in length, flame temperature, and flame structure. This phenomenon is suspected to be due to thermodiffusive instability.

Concurrent-Flow Flame Spread Over a Thin Solid in a Narrow Confined Space in Microgravity

2019 ◽  
Author(s):  
Yanjun Li ◽  
Ya-Ting T. Liao ◽  
Paul Ferkul
Keyword(s):  
International Space Station ◽  
Flame Spread ◽  
Numerical Study ◽  
Space Station ◽  
Spread Rate ◽  
International Space ◽  
Concurrent Flow ◽  
Microgravity Experiments ◽  
Flame Spread Rate ◽  
Flow Duct

Abstract A numerical study is pursued to investigate the aerodynamics and thermal interactions between a spreading flame and the surrounding walls as well as their effects on fire behaviors. This is done in support of upcoming microgravity experiments aboard the International Space Station. For the numerical study, a three-dimensional transient Computational Fluid Dynamics combustion model is used to simulate concurrent-flow flame spread over a thin solid sample in a narrow flow duct. The height of the flow duct is the main parameter. The numerical results predict a quenching height for the flow duct below which the flame fails to spread. For duct heights sufficiently larger than the quenching height, the flame reaches a steady spreading state before the sample is fully consumed. The flame spread rate and the pyrolysis length at steady state first increase and then decrease when the flow duct height decreases. The detailed gas and solid profiles show that flow confinement has competing effects on the flame spread process. On one hand, it accelerates flow during thermal expansion from combustion, intensifying the flame. On the other hand, increasing flow confinement reduces the oxygen supply to the flame and increases conductive heat loss to the walls, both of which weaken the flame. These competing effects result in the aforementioned non-monotonic trend of flame spread rate as duct height varies. This work relates to upcoming microgravity experiments, in which flat thin samples will be burned in a low-speed concurrent flow using a small flow duct aboard the International Space Station. Two baffles will be installed parallel to the fuel sample (one on each side of the sample) to create an effective reduction in the height of the flow duct. The concept and setup of the experiments are presented in this work.

scholarly journals Study experimental of flame-spread rate and spread limit distance of bio-solar droplets in microgravity combustion

2018 ◽  
Vol 197 ◽  
pp. 08006 ◽  
Author(s):  
Laila Fitriana ◽  
Bawono Widyo Gumelar ◽  
Herman Saputro ◽  
Tutuko Firdani ◽  
Riyadi Muslim ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Flame Spread ◽  
Combustion Engine ◽  
Microgravity Condition ◽  
Free Fall ◽  
Spray Combustion ◽  
Spread Rate ◽  
Stable Combustion ◽  
Fuel Droplets ◽  
Flame Spread Rate

The most important issues in spray combustion science are how to understand the mechanism of the combustion of liquid fuel spray, especially in the flame-spread phenomenon. In spray combustion, combustion is the existence of the group is very important in order to obtain the stable combustion. Therefore, the flame spread among fuel droplets affects the occurrence of stable combustion in the spray combustion engine. This study was focused on phenomenon on diesel combustion engines. This research was conducted to study the behavior of flame spread rate of flame spread and limit the distance of bio-diesel liquid droplets. This research method was used experimental research. Microgravity condition was Obtained through the free fall tower with the height of the tower used is 6 m. Observed droplets suspended was placed on SiC fibers with different distance and droplet size 1 mm. This study observed Also the influence of the flame propagation direction of the burning droplet to the next burning droplets that lies in the direction and perpendicular to the direction of the flame propagation. The results showed that the bio-diesel fuel droplet Igniter (I) could burn next droplet (A)at a distance (S/d0) = 8.

Measurement of instantaneous flame spread rate over solid fuels using image analysis

2017 ◽  
Vol 91 ◽  
pp. 123-129 ◽  
Author(s):  
Subrata Bhattacharjee ◽  
Luca Carmignani ◽  
Gregory Celniker ◽  
Blake Rhoades
Keyword(s):  
Image Analysis ◽  
Flame Spread ◽  
Solid Fuels ◽  
Spread Rate ◽  
Flame Spread Rate

Effect of Sample Width on Characteristics of Flame Spread across Eucalyptus Wood Surface

2013 ◽  
Vol 401-403 ◽  
pp. 767-770
Author(s):  
Gui Hong Wu ◽  
Yi Qiang Wu ◽  
Yun Chu Hu ◽  
Xiao Dan Zhu
Keyword(s):  
Mass Loss ◽  
Flame Spread ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Flame Height ◽  
Spread Rate ◽  
Eucalyptus Wood ◽  
Flame Spread Rate ◽  
Sample Width ◽  
The Relationship

To study the effect of sample width on flame spread characteristics, a series of laboratory-scale experiments were conducted employing eucalyptus wood with width from 3 to 7 cm. Flame dimension, flame spread rate and mass loss rate were obtained. The relationship between these flame spread characteristics and sample width was explored. Both the dimensionless average flame height and depth vary as the-n power of sample width. With the increase of sample width, both the flame spread rate and mass loss rate first decrease and then rise. The minimum values appear when sample width measures 6 cm.

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