Match!

The effect of support fibers on micro-convection in droplet combustion experiments

Published on Jan 1, 2015
· DOI :10.1016/j.proci.2014.07.022
Yu Cheng Liu11
Estimated H-index: 11
(Cornell University),
Yuhao Xu7
Estimated H-index: 7
(Cornell University)
+ 1 AuthorsMichael C. Hicks8
Estimated H-index: 8
(Glenn Research Center)
Abstract
This study reports experimental evidence of gas phase micro-convection induced by support fibers used in droplet combustion experimentation. Soot aggregates formed during combustion of n-octane and n-decane droplets (initial diameters ranging from 0.5 mm to 5 mm) provide natural seeds to reveal the thermal and flow asymmetries involved. The experiments are carried out in an environment that reduces the influence of forced and buoyant convection for both free-floating (unsupported) and fiber-supported droplets. Under these conditions, the soot trapping patterns (due to a balance of thermophoretic and flow-induced drag) would be spherical. However, this situation is only observed for unsupported droplets, or for fiber-supported droplets when the fiber is small relative to the droplet diameter. For Do 1 mm the International Space Station provided capabilities for anchoring test droplets onto a single 80 μm SiC fiber, and for deploying unsupported droplets. Results clearly indicate that a non-symmetric gas flow field exists in some cases (i.e., for 1 mm < Do < 3 mm, with an 80 μm fiber) near to where the fiber enters the droplet. This gas motion originates from the presence of the fiber that introduces asymmetries in the temperature and flow fields resulting in localized force imbalances on the soot particles, which cause vortical flow patterns near the fiber. This may in part be explained by flow asymmetries induced by droplet shape distortions coupled with heat exchanges between the fiber and surrounding gas and conduction into the droplet, resulting in a Marangoni flow near the droplet surface. For very small fibers (or for unsupported droplets) spherical soot shells are found suggesting that no thermal and flow asymmetries exist.
  • References (23)
  • Citations (13)
📖 Papers frequently viewed together
29 Citations
6 Citations
2013
27 Citations
78% of Scinapse members use related papers. After signing in, all features are FREE.
References23
Newest
#1Yu-Cheng LiuH-Index: 1
3 Citations
#1Yu Cheng Liu (Cornell University)H-Index: 11
#2Tanvir Farouk (USC: University of South Carolina)H-Index: 18
Last. C. Thomas Avedisian (Cornell University)H-Index: 14
view all 5 authors...
This study presents an experimental effort and detailed numerical simulation of the burning process of an ester-based biodiesel fuel droplet – methyl decanoate (MD). The experiments are carried out using test droplets that are anchored to small SiC support structures (14 lm diameter) and that burn in an ambience subjected to a low gravity level to promote spherical symmetry in the droplet burning process. The initial droplet diameters are 0.53–0.57 mm and the combustion gas is normal atmospheric...
18 CitationsSource
#1Tanvir Farouk (Princeton University)H-Index: 18
#2Yu Cheng Liu (Cornell University)H-Index: 11
Last. Frederick L. Dryer (Princeton University)H-Index: 68
view all 5 authors...
Abstract Combustion characteristics of isolated sub-millimeter sized methyl butanoate (MB) droplets are studied at low gravity (10 −4 m/s 2 ) in a 1.2 s drop tower. In the experiments, droplets were grown and deployed onto the intersection of two 14 μm silicon carbide fibers in a cross-string arrangement and exposed to symmetrically placed spark ignition sources. The initial droplet diameter was fixed at 0.54 ± 0.01 mm, and experiments were carried out in room temperature air at atmospheric pres...
27 CitationsSource
#1Hiroshi Nomura (College of Industrial Technology)H-Index: 10
#2Hiromu Takahashi (College of Industrial Technology)H-Index: 1
Last. Masao Kikuchi (JAXA: Japan Aerospace Exploration Agency)H-Index: 7
view all 4 authors...
Abstract Combustion experiments of fuel droplet array in fuel-vapor/air mixture were performed at normal and microgravities to investigate mechanism of flame spread. A 10-droplet array was inserted into the test section filled with a saturated fuel-vapor/air mixture as a simple model of prevaporized sprays. Gas equivalence ratio of the fuel-vapor/air mixture was controlled by the test section temperature. n -Decane droplets of 0.8 mm in the initial diameter were employed. The first droplet was i...
10 CitationsSource
#1Shinji Nakaya (UTokyo: University of Tokyo)H-Index: 8
#2Kotaro Fujishima (UTokyo: University of Tokyo)H-Index: 1
Last. Daisuke Segawa (OPU: Osaka Prefecture University)H-Index: 10
view all 5 authors...
Abstract The burning characteristics of isolated fuel droplets for ethanol, 1-butanol and n -decane were experimentally examined in carbon dioxide-rich or argon-rich environments under microgravity. The ambience consisted of oxygen, nitrogen, carbon dioxide and argon. The concentration of oxygen was fixed to be 21% in volume percentage, and that of carbon dioxide or argon was varied from 0% to 60% in volume percentage. Detailed measurements of the droplet surface areas were conducted using a hig...
11 CitationsSource
#1Christopher L. Dembia (Cornell University)H-Index: 7
#2Yu Cheng Liu (Cornell University)H-Index: 11
Last. C. Thomas Avedisian (Cornell University)H-Index: 14
view all 3 authors...
A simple automated image analysis algorithm has been developed that processes consecutive images from high speed, high resolution digital images of burning fuel droplets. The droplets burn under conditions that promote spherical symmetry. The algorithm performs the tasks of edge detection of the droplet’s boundary using a grayscale intensity threshold, and shape fitting either a circle or ellipse to the droplet’s boundary. The results are compared to manual measurements of droplet diameters done...
16 CitationsSource
#1Yu Cheng Liu (Cornell University)H-Index: 11
#2C. Thomas Avedisian (Cornell University)H-Index: 14
Abstract The droplet burning characteristics of binary blends of iso-octane, n -heptane and toluene were studied in an ambience that minimizes external convection and promotes spherical droplet flames. The results are compared to gasoline (87 octane rating). The initial droplet diameter was fixed at 0.51 ± 0.02 mm and the experiments were carried out in room temperature air. Measurements of the evolution of droplet diameter show that iso-octane, n -heptane and their mixtures have almost identica...
29 CitationsSource
#1Tanvir Farouk (Princeton University)H-Index: 18
#2Frederick L. Dryer (Princeton University)H-Index: 68
Abstract Tethered methanol droplet combustion in carbon dioxide enriched environment is simulated using a transient one-dimensional spherosymmetric droplet combustion model that includes the effects of tethering. A priori numerical predictions are compared against recent experimental data. The numerical predictions compare favorably with the experimental results and show significant effects of tethering on the experimental observations. The presence of a relatively large quartz fiber tether incr...
22 CitationsSource
#1Michael C. Hicks (Glenn Research Center)H-Index: 8
#2Vedha Nayagam (Glenn Research Center)H-Index: 15
Last. Forman A. Williams (UCSD: University of California, San Diego)H-Index: 54
view all 3 authors...
Diffusive extinction of methanol droplets with initial diameters between 1.25 mm and 1.72 mm, burning in a quiescent microgravity environment at one atmosphere pressure, was obtained experimentally for varying levels of ambient carbon-dioxide concentrations with a fixed oxygen concentration of 21% and a balance of nitrogen. These experiments serve as precursors to those which are beginning to be performed on the International Space Station and are motivated by the need to understand the effectiv...
25 CitationsSource
#1Alberto Cuoci (Polytechnic University of Milan)H-Index: 30
#2Marco Mehl (Polytechnic University of Milan)H-Index: 27
Last. E. Ranzi (Polytechnic University of Milan)H-Index: 9
view all 6 authors...
This paper presents a mathematical model for the unsteady evaporation, ignition, and combustion of isolated fuel droplets under microgravity. The model consists of a large structured system of differential algebraic equations, where the numerical complexity is due both to the stiff nature of the kinetic mechanism and to the flame structure around the droplet. A very general, detailed kinetic scheme, consisting of ∼200 species and over 5000 reactions, is used to describe the gas-phase combustion ...
70 CitationsSource
Cited By13
Newest
#1Jigang WangH-Index: 1
Last. Chunhua SunH-Index: 1
view all 5 authors...
Abstract The effect of support fiber on fuel droplet vaporization is experimentally investigated in a stagnant high-temperature environment (673–973 K) using high-speed backlit imaging technique. Droplets with nearly identical initial diameter suspended on the different support fibers, thus the effect of support fiber on droplet vaporization due to different initial droplet diameter is removed. The fiber diameters are 0.08, 0.1 and 0.15 mm, and thermal conductivities are 1.4, 80 and 400 W/m·K, r...
Source
#1Shion Ando (UTokyo: University of Tokyo)
#2Yuxiang Wu (UTokyo: University of Tokyo)
Last. Mitsuhiro Tsue (UTokyo: University of Tokyo)H-Index: 15
view all 4 authors...
Abstract Droplet combustion behavior of degraded and non-degraded fatty acid methyl ester (FAME) were studied under microgravity condition. Accelerated oxidation tests were conducted for methyl laurate (LME) and methyl oleate (OME) as representatives of FAME, and the changes in viscosities and compositions were evaluated. The Rancimat method was employed for oxidizing fuels at 100 °C for 6 or 24 h. The viscosities and compositions were measured with an Ubbelohde viscometer and a gas chromatograp...
Source
#1S. Radhakrishnan (Indian Institute of Technology Madras)H-Index: 1
#2N. Srivathsan (Indian Institute of Technology Madras)H-Index: 1
Last. Shamit Bakshi (Indian Institute of Technology Madras)H-Index: 9
view all 4 authors...
Abstract The influence of the suspender on the evaporation of droplets under quiescent atmospheric conditions was studied experimentally using pendant droplets of ethanol (volatile) and water (non-volatile). Conducting and non-conducting suspenders of different materials and configurations (a steel needle, glass needle, steel rod, and glass rod) were evaluated. For both liquids, it is observed that the rate of evaporation is higher with steel suspenders. More importantly, for ethanol droplets, t...
1 CitationsSource
#1Álvaro Muelas (University of Zaragoza)H-Index: 1
#2Pilar Remacha (University of Zaragoza)H-Index: 1
Last. Javier Ballester (University of Zaragoza)H-Index: 23
view all 3 authors...
Abstract The droplet combustion characteristics of conventional heating oil, UCO biodiesel and their mixtures (10 and 20% biodiesel by volume) were examined in a free-falling droplet combustion facility designed to approach the typical temperature and oxygen conditions around individual droplets in real boiler flames. Moreover, and given the importance of avoiding effects due to gravity or convection in this type of experiments, the quite spherical soot shells recorded (infrequent event in free-...
1 CitationsSource
#1Christian Chauveau (CNRS: Centre national de la recherche scientifique)H-Index: 21
#2Madjid Birouk (UM: University of Manitoba)H-Index: 18
Last. Iskender Gökalp (CNRS: Centre national de la recherche scientifique)H-Index: 30
view all 4 authors...
Abstract This paper presents an analysis of the effect of the droplet support fiber on the droplet evaporation process. This effect is evaluated for a droplet evaporating in a hot environment at atmospheric pressure using the experimental results of the present study and those in the literature. Selected published results are acquired using similar test conditions and experimental setups as the present data. The only main difference between these studies is the droplet support fiber diameter whi...
3 CitationsSource
#1Masato Mikami (Yamaguchi University)H-Index: 14
#2Naoya Motomatsu (Yamaguchi University)H-Index: 1
Last. Takehiko Seo (Yamaguchi University)H-Index: 4
view all 5 authors...
Abstract This research investigates the flame-spread characteristics between two droplets, Droplets A and L, of different diameter. n-Decane droplets are placed at intersections of 14 µ SiC fibers. The flame spread from Droplet A to Droplet L was observed in microgravity. The results show that the flame-spread rate decreases with an increase in the droplet spacing or the initial diameter of Droplet L for a constant initial diameter of Droplet A. The flame-spread time is approximated as the summa...
2 CitationsSource
#1Masato Mikami (Yamaguchi University)H-Index: 14
#2Yasuko Yoshida (Yamaguchi University)H-Index: 2
Last. Masaki NokuraH-Index: 1
view all 7 authors...
This research conducted microgravity experiments on the flame spread over randomly distributed n-decane-droplet clouds aboard the Japanese Experiment Module “Kibo” on the International Space Station. 67-152 droplets were distributed at intersections of a 30 × 30 square lattice with 14-micron SiC fibers placed in a combustion chamber. One droplet on the bottom side of lattice was ignited by a hot-wire igniter to start the flame spread. The burning behavior was observed by a digital camera. This p...
4 CitationsSource
#1D. Chaitanya Kumar Rao (IIT-KGP: Indian Institute of Technology Kharagpur)H-Index: 4
#2Srinibas Karmakar (IIT-KGP: Indian Institute of Technology Kharagpur)H-Index: 7
Last. S.K. Som (IIT-KGP: Indian Institute of Technology Kharagpur)H-Index: 16
view all 3 authors...
ABSTRACTButanol is mainly produced by acetone–butanol–ethanol (A-B-E) fermentation. The higher costs associated with the separation of butanol from the A-B-E mixture has prohibited the large-scale production of butanol. The direct use of the intermediate product (A-B-E mixture) could be an economical pathway if utilized for clean combustion. The present investigation deals with the puffing and micro-explosion characteristics in the combustion of a single droplet comprising butanol/Jet A-1, A-B-E...
12 CitationsSource
#1Yuhao Xu (Cornell University)H-Index: 7
#2Michael C. Hicks (Glenn Research Center)H-Index: 8
Last. C. Thomas Avedisian (Cornell University)H-Index: 14
view all 3 authors...
Abstract The burning characteristics of iso -octane droplets in the standard atmosphere are reported over a large range of initial droplet diameters (0.5 mm D o 5 mm) for near one-dimensional droplet flames as promoted by low gravity. A ground-based drop tower and a space-based platform (International Space Station) were used to provide an environment to examine the influence of D o that encompasses regimes where radiation does not have an effect on burning to where it does. For D o K ) was near...
3 CitationsSource
#1Yu Cheng Liu (UM: University of Michigan)H-Index: 11
#2Yuhao Xu (Cornell University)H-Index: 7
Last. C. Thomas Avedisian (Cornell University)H-Index: 14
view all 4 authors...
Abstract This paper reports the results of a comprehensive experimental study on the effect of initial droplet diameter ( D o ) over a very wide range (0.5 mm D o n -heptane, n -octane and n -decane – that are representative of components found in petroleum-based transportation fuels and their surrogates. Spherical symmetry in the burning process was promoted by carrying out the experiments in a reduced convection (stagnant ambience) and buoyancy (low gravity) environment using the facilities of...
18 CitationsSource