Name: experimental methodology for estimation of local heat fluxes and burning rates in steady laminar boundary layer diffusion flames
Uploaded: 2016-06-01T14:00:00
Duration: 10 min 29 s
Description: Watch this Scientific Journal Video about Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames at JoVE.com

The authors would like to acknowledge financial support for this work from the Minta Martin Foundation at the University of Maryland, College Park.

1. Planning of Experiments
<ol>
	<li>Follow instructions and safety precautions before entering the fire or combustion research laboratory. Safety training is generally required for new users.</li>
	<li>Schedule your experiments in advance to carry out the required tests. Consider the details of the experiment, transport of required fuels and necessary equipment.</li>
	<li>Identify the liquid or solid fuel experiments of interest. Prepare the materials accordingly.</li>
</ol>
2. Preparation of Materials and Instrumentation
<ol>
	<li>For liquid fuel experiments, prepare a fuel wick of porous noncombustible material (alkaline earth silicate wool). Previous experiments4-6 have utilized 8 cm x 8 cm x 1.27 cm for free convection tests and 10 cm x 10 cm x 1.27 cm thick sheets for forced convection tests.
	<ol>
		<li>Bake the given fuel wick for approximately 20 min by exposing it to a diffusion flame from a propane torch in order to burn organic binders inside the wick.</li>
		<li>In order to eliminate leakage of the liquid fuel from the sides of the wick, liberally apply liquid sodium silicate with a syringe covering all faces of the wick except the top face.</li>
		<li>Shield all but the top face of the wick with aluminum foil. Use a high temperature adhesive to paste the aluminum foil to the sides of the wick.</li>
	</ol>
	</li>
	<li>For solid fuel experiments, cut out a sheet of the solid fuel. In previous free convection experiments2, an 8 cm&#160;x 8 cm x 1.27 cm thick sheet of a clear cast polymethyl methacrylate (PMMA) has been used.</li>
	<li>Cut out a slot in a sheet of ceramic fiber insulation board equal to the size of the fuel sample in which to later mount the sample. Often, use the same porous noncombustible as the fuel wick; however seal it with high temperature matte black paint.</li>
	<li>Check the given data acquisition hardware and software. Open the software and check the temperature mapping algorithm before carrying out required tests.</li>
</ol>
3. Preparation of the Experimental Setup
<ol>
	<li>Place a side-view digital SLR camera so that it is aligned with the central axis of the fuel and far enough away so that the full side view of the given flame is captured.
	<ol>
		<li>For forced-convection &#64258;ames, image a &#64257;eld of view at the center of the fuel specimen covering an area of 16 cm x 8 cm for calculating the &#64258;ame stand-off distance in the pyrolysis zone.</li>
	</ol>
	</li>
	<li>Place the traverse mechanism above the fuel sample. Attach a 50 &#181;m wire-diameter micro thermocouple to the horizontal axis of the traverse mechanism with care.</li>
	<li>Turn on the programmable stepper motor controller.</li>
	<li>In the case of forced flow experiments, power up the centrifugal blower of the wind tunnel.</li>
	<li>Set the pulse-width-modulation (PWM) controller to a frequency of 7,000 Hz with power settings ranging from 16% to 50% for different blower speeds, verified with a hot-wire anemometer.</li>
	<li>Wear safety glasses and fire-resistant hand gloves before proceeding with the test.</li>
	<li>During each test, soak the wick with liquid fuel (methanol or ethanol) up to its point of saturation. For an 8 cm x 8 cm x 1.27 cm thick wick, 90 ml was sufficient to fully soak the wick using two 60 ml syringes while for a 10 cm x 10 cm x 1.27 cm thick wick, 120 ml was found to be sufficient.</li>
	<li>Place the fuel-soaked wick / solid fuel plate carefully into the fuel-wick holder. Check the flatness of the fuel wick surface with an angle gauge.</li>
	<li>Open mass balance software and check the USB-interface settings. Check the mass balance and note its reading before the test.</li>
</ol>
4. Running Experiments in a Combustion or Fire Lab
<ol>
	<li>Ensure proper ventilation of the experimental facility by turning on the exhaust after completing each set of experiments. Exhaust should be as minimal or isolated as possible during the experiments to help eliminate flow disturbances.</li>
	<li>Before a sample is ignited, calibrate the side-view digital camera by taking a picture of a sheet of graph paper or ruler that is aligned along the central axis of the fuel surface. Obtain an average pixel/mm count from the calibration images. Use this value of pixels/mm during the post-processing of the images (for setting up the measurement scale in ImageJ).</li>
	<li>Ignite the fuel with a propane torch, momentarily touching it for a liquid fuel wick and passing the flame uniformly over the surface for 50-60 sec with a solid fuel.</li>
	<li>Start experimental time immediately after uniform ignition. Use a stop watch to denote the burning time.</li>
	<li>Press the data acquisition button on the mass balance software.</li>
	<li>Monitor the mass loss of the burning wick over a timed interval and write it to a measurement file. Use the mass balance software for the given purpose.</li>
	<li>Repeat steps 4.3 to 4.6 for multiple tests under the same conditions to ensure repeatability.</li>
	<li>Use the mass-loss versus time curve to determine the steady burning regime, where a linear fit of the mass loss has a high R2 value.</li>
	<li>For unsteady solid fuels, burn samples at 50 sec increments from ignition to burnout to measure surface regression (e.g., for 50 sec, 100 sec, 150 sec, etc.).</li>
	<li>Cut burned solid fuels along the centerline after cooling for regression testing.</li>
	<li>Take side-view photographs of cut solid fuels and load into ImageJ. Measure the regression at streamwise locations by converting pixels to cm with a ruler. Step by step procedure to process a given image in ImageJ is listed hereunder.
	<ol>
		<li>Open side-view photograph of the solid fuel sample in ImageJ via Select File &#8594; Open Image.</li>
		<li>Open the calibration image (with ruler) of the solid fuel sample in ImageJ via Select File &#8594; Open Calibration Image.</li>
		<li>Stack up the calibration image and solid fuel sample image. Go to Image &#8594; Stacks &#8594; Images to stack.</li>
		<li>Set measurement scale: Draw a line between two points of known distance such as a ruler on the photograph. Go to Analyze &#8594; Set Scale. In the Set Scale window the length of the line, in pixels, will be displayed. Type the known distance and units of measure in the appropriate boxes and click OK.</li>
		<li>Draw a new line and confirm that the measurement scale is correct.</li>
		<li>Measuring distance between two points in the given sample photograph: Draw a line between two points. The status bar will show the angle (from horizontal) and the length. Analyze &#8594; Measure (or Ctrl+M or simply type M on the keyboard) transfers the values to a data window.</li>
		<li>Measure the regression at each streamwise location&#160;x by measuring the thickness of the burn-out sample and subtracting it from the initial thickness of the sample.</li>
	</ol>
	</li>
	<li>Note the time interval over which the surface of solid fuels remain approximately flat and use for temperature mapping, or adjustments of thermocouple positions made to compensate for surface regression.</li>
	<li>Set the temperature mapping interval to capture measurements during the steady burning regime, approximately 150 sec for solid PMMA and 400 sec for liquid-soaked wicks. Set the temperature mapping interval based on the steady burning time interval of liquid and solid fuels. A recommended step size near the surface is 0.25 mm4-6.</li>
	<li>Align a micro thermocouple carefully with the surface of the fuel using a X-Y unislide. Place the given thermocouple at the center of width of the sample.</li>
	<li>Move the micro thermocouple carefully to the leading edge of the fuel wick using the X-Y unislide.</li>
	<li>Run a data acquisition program on a computer and read the grid scanning algorithm from a folder on the desktop. 
	Note: Once the experiment is under way, data collection is automatic, and the user only needs to oversee it to make sure the experiment is going as planned.</li>
	<li>Using a data acquisition program on a computer, acquire data and write it to a measurement file. Note, sampling rates of 1004-5 to 5006 Hz were used in past experiments.</li>
	<li>When finished, extinguish the flame. Turn off the PWM controller and disconnect the power plug of the blower from the 3-phase 240 VAC power outlet.</li>
	<li>Turn off the stepper motor controller.</li>
	<li>Repeat steps 4.12 to 4.18 for additional experiments at similar or different flow conditions with the same thermocouple. A minimum of 5 tests should be repeated for each given flow condition (e.g., forced flow velocity or vertical orientation).</li>
	<li>Repeat steps 4.12 to 4.18 for a 75 &#181;m micro thermocouple. Traverse two thermocouples (50 &#181;m and 75 &#181;m wire-diameter) along the same path at the center of the flame for accurate radiation corrections. Smaller thermocouples might also be used, however breakage often occurred for wires below 50 &#181;m.</li>
</ol>
5. Data Analysis
<ol>
	<li>Read the processed data from the LVM file into Matlab or other analytic software.</li>
	<li>Average the temperature data at each spatial point from different tests.</li>
	<li>Calculate a radiation correction from averaged thermocouple data at each streamwise location, following the correlation of Collis and Williams10 described in detail below.</li>
	<li>Calculate compensated temperature measurements by adding the radiation correction to raw temperature data.</li>
	<li>Non-dimensionalize the temperature data and spatial location.</li>
	<li>Fit the non-dimensional temperature data at the fuel surface with an appropriate higher-order polynomial fit using a curve fit algorithm in Matlab or other dedicated software. 4 to 6 points near the surface were found to work well in previous studies4-6.</li>
	<li>Calculate the normal non-dimensional temperature gradients at the fuel surface from the slope of the higher order polynomial fit to the non-dimensional temperature distribution at the fuel surface (y=0).</li>
	<li>Calculate the local mass burning rate from the corresponding local non-dimensional temperature gradient at the fuel surface using a theoretical correlation based on the Reynolds Analogy4.</li>
	<li>Calculate the convective heat flux from the temperature gradient at the surface of the fuel5-6.</li>
</ol>

<ol>
	<li>Babrauskas, V., Peacock, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heat+release+rate:+the+single+most+important+variable+in+fire+hazard.">Heat release rate: the single most important variable in fire hazard.</a> Fire Safety J. 18 (3), 255-272 (1992).</li><li>Pagni, P., Shih, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Excess+pyrolyzate.">Excess pyrolyzate.</a> Proc. Combust. Inst. 16 (1), 1329-1343 (1977).</li><li>Orloff, L., Modak, A. T., Alpert, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Burning+of+large-scale+vertical+surfaces.">Burning of large-scale vertical surfaces.</a> Proc. Combust. Inst. 16 (1), 1345-1354 (1977).</li><li>Singh, A. V., Gollner, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimation+of+local+mass+burning+rates+for+steady+laminar+boundary+layer+diffusion+flames.">Estimation of local mass burning rates for steady laminar boundary layer diffusion flames.</a> Proc. Combust. Inst. 35 (3), 2527-2534 (2015).</li><li>Singh, A. V., Gollner, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+methodology+for+estimation+of+local+heat+fluxes+in+steady+laminar+boundary+layer+diffusion+flames.">A methodology for estimation of local heat fluxes in steady laminar boundary layer diffusion flames.</a> Combust. Flame. 162 (5), 2214-2230 (2015).</li><li>Singh, A. V., Gollner, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+burning+rates+and+heat+flux+for+forced+flow+boundary-layer+diffusion+flames.">Local burning rates and heat flux for forced flow boundary-layer diffusion flames.</a> AIAA J. 54 (2), 408-418 (2016).</li><li>Collis, D., Williams, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+convection+from+heated+wires+at+low+Reynolds+numbers.">Two-dimensional convection from heated wires at low Reynolds numbers.</a> J. Fluid Mech. 6 (3), 357-384 (1959).</li><li>Jakob, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Heat Transfer. , (1967).</li><li>Sforza, P., Steiger, M., Trentacoste, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+on+three-dimensional+viscous+jets.">Studies on three-dimensional viscous jets.</a> AIAA J. 4 (5), 800-806 (1966).</li><li>Pizzo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+observations+on+the+steady-state+burning+rate+of+a+vertically+oriented+PMMA+slab.">Experimental observations on the steady-state burning rate of a vertically oriented PMMA slab.</a> Combust. Flame. 152 (3), 451-460 (2008).</li><li>Chilton, T. H., Colburn, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass+transfer+(absorption)+coefficients+prediction+from+data+on+heat+transfer+and+fluid+friction.">Mass transfer (absorption) coefficients prediction from data on heat transfer and fluid friction.</a> Ind. Eng. Chem. 26 (1), 1183-1187 (1934).</li><li>Silver, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+the+Reynolds+analogy+to+combustion+of+solid+fuels.">Application of the Reynolds analogy to combustion of solid fuels.</a> Nature. 165, 725-726 (1950).</li></ol>

The authors have nothing to disclose.

The goal of this investigation was to develop a new methodology for the estimation of local mass burning rates for both liquid and solid fuels under a variety of flow-field conditions. The study considered two cases, a free convection boundary layer diffusion flame and forced convection boundary layer diffusion flames established under different free-stream conditions, using both liquid and solid fuels.
Local burning rates measured via fine-wire thermocouple measurements over both liquid fuel-soaked wicks and over solid slabs of PMMA were found to match other means of estimation, namely fuel regression measurements. These temperature gradients near the fuel surface were determined using a correlation based upon the Reynolds analogy12-13 that, while requiring steady, laminar combustion, worked very well for small scale samples, ultimately resulting in data within 15% accuracy for mean results and much more for local measurements4-6. The correlating factor for these local mass-loss rate measurements depends upon the Spalding mass transfer number of the representative fuel and other thermo-physical properties of the fuel which can be calculated a priori. The results suggest that this technique may be useful to extract these quantities and understand the burning of small scale fuels in greater detail in the future.
Other studies in the literature have expanded the representative work here incorporating numerical simulations4 and experiments on vertically-oriented samples, freely burning4,5, and horizontally-mounted samples under ambient winds6. For these configurations, components of heat fluxes have also been determined locally over the fuel surface using the same fine-wire thermocouple technique very close to the condensed fuel surface. While components of heat flux have been measured in the past by use of embedded gauges, this technique is minimally invasive and offers direct measurement of convective heat fluxes, which has not been possible before.
Particular care should be taken during experiments when choosing specific configurations and setup of the apparatus. In these experiments, thermocouples chosen for step 3.2 protruded from a small ceramic tube, keeping tension on the wire and making the location of the thermocouple relatively fixed. Using a thermocouple wire suspended over the entire flame without a tube would reduce possible disturbances from the ceramic tube, however it would make locating the specific location of the thermocouple much more variable as the wire tends to expand with increasing temperatures. Sometimes changes in the configuration could induce effects across the width of the sample (for instance inclining the sample). If the setup is modified from those studied in the past4-6, around step 4.14 occasional checks that the flame temperature measurements across the width of the sample show no significant variation should be taken (i.e., a 2-D assumption still holds). Otherwise, a 3-D mapping system will need to be implemented.
The most critical steps while performing the experiments have to do with preparation of the fuel and proper use of thermocouples. Even slight deviations in positioning of the thermocouples could cause errors, therefore care must be taken when positioning the thermocouple in steps 3.2, 4.13 and 4.14. The fuel wick must also be placed so that as flat a surface as possible is maintained (step 2.1) and all filler material should be baked out of wicks (step 2.1.1).
The exhaust system, activated in step 4.1 should also be kept as minimal or isolated as possible close to the experiment to help eliminate flow disturbances. This should be checked by ensuring a small candle is not blown where the test will take place (without wind). Baffles, screens, a separate enclosed facility or testing in a large space can be used to accomplish this. In step 4.2, the solid fuel must be ignited as uniformly as possible. While the propane torch is not the most ideal source to do this, experiments were not found to be sensitive to the ignition source in past work4-6. Sensitivity to the ignition source should be documented during experiments by varying the time or intensity of exposure and observing the results on the steady mass burning rate. If sensitivity is observed a radiant panel should alternatively be used to ignite samples. Solid fuels, or any fuel that does not have a large (&#62;300 sec) steady burning region as observed by mass-loss rates should have temperature mapping taken during a short region. For instance, in step 4.13 the mapping is recommended for PMMA to be taken over the first 150 sec, while the fuel is still relatively flat and surface regression has been well documented. Surface regression measurements can use ImageJ or other similar image software to measure pixels on the photographs and convert to length. Alternatively, a digital micrometer can be used to measure the surface regression of the solid plate after it cools (note the surface of &#34;bubbling&#34; materials such as PMMA must be sanded first).
The proposed burning rate correlation is based upon laminar assumptions, however, it is hypothesized that this technique should follow a similar form for turbulent burning of a fuel surface, albeit with a modified functional relationship which must be experimentally determined. The work presented here can be subsequently extended to turbulent boundary layer combustion and associated interactions between turbulence and gas-phase heat release that drive the incident heat flux to the fuel surface can be further investigated.
The theory upon which the burning rate correlation is based also neglects radiation. The theory is oversimplified leading to uncertainty in its predictive capabilities in circumstances that are not covered by the present work. For instance, the given methodology may not work for high sooting flames where the heat flux to the surface is largely radiative. For large turbulent wall flames, where radiative heat flux to the condensed fuel surface is high, the proposed burning rate correlation may or may not work. Inclusion of radiation effects in the proposed correlation is, thus, desirable and further research must be undertaken in order to determine this functional relationship. This area requires improvements in the model if confident prediction methods are to be achieved for such flames.

While critical advancements have been made in the area of fire safety research over the past century, predicting rates of flame spread still remains a challenge for many materials in diverse configurations. Flame spread often proceeds in either the built or natural environments as a series of ignitions of new elements, emanating from an initial source of ignition. Knowledge of the burning characteristics of individual burning materials is critical in order to predict these rates of flame spread, because this contributes to rates of heating to unignited elements. The heat-release rate (HRR) of a fuel element has therefore been cited as the most fundamental quantity in fire research1, being approximately equal to the burning (mass-loss) rate of the condensed-phase fuel, namely the evaporation rate of a liquid fuel or pyrolysis rate of a solid fuel.
The burning rate can be thought of as a measure of the flammability of a material and is a critical parameter in fire risk analysis and the design of fire suppression systems. The local mass loss (or burning) rate, m&#775;&#34;f, of a vertical wall is, in particular, an important variable in many fire-related problems, such as flame spread on a wall, fire growth, and energy-release rates within an enclosure fire, and the spread of smoke and hot gas plumes. For prediction of upward flame spread on a vertical wall, the flame height must be calculated, which depends on the total energy release rate; that, in turn, is directly influenced by the local mass-loss rate integrated over the entire pyrolyzing area of the wall2-3. While knowledge of these integrated mass-loss rates are relatively well known, knowledge of mass-burning rates at incremental locations along a fuel surface are not well known because experimental techniques to measure such rates are extremely limited. A technique that provides this &#34;local&#34; mass-burning rate information could provide increased insight to the burning of condensed fuels, enabling researchers to further understand the mechanisms which distinguish different fuels or configurations from one another. As most materials are first evaluated at the small scale (e.g., in a cone calorimeter1), a logical first step is to provide a technique to measure local mass burning rates in small, laminar diffusion flames over condensed fuel surfaces.
The work presented here discusses the experimental methodology and protocols for carrying out experiments on steady laminar flames established over condensed fuel surfaces. Estimation of local temperature gradients using micro thermocouples is a particularly useful technique for the estimation of local mass burning rates and heat fluxes in these flames4-6. An analysis of literature data shows the difficulty of determining local heat transfer, combustion and friction coefficients at the condensed fuel surface, which are important for understanding the physics and the underlying mechanisms that drive a particular fire and its spread4-6. Components of heat fluxes, which have remained perhaps the most well-measured fire property at local locations over a fuel surface, have proved difficult to measure. Effects such as variability of fuels, heat flux scalability, difficulty of achieving steady state conditions and differing heat flux gauge technologies have contributed to a rather wide scatter of data which is available in the literature4. Measurements of local temperature gradients with high accuracy will help to alleviate this variability and also provide heat transfer correlations that could be used for numerical validation of laminar wall fires, a canonical fire research problem. Such experiments are also useful in exploring the dynamic relationship between a combustible condensed fuel surface and gas-phase flames in laminar and turbulent boundary layers. Methods to accurately capture these temperature gradients in an accurate and repeatable manner are described below.

<table>
	<tbody>
		<tr>
			<td>Thermocouples with connectors and clamps</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Unsheathed Fine Gauge T/C</td>
			<td>P13R-002</td>
			<td>Omega Engineering, Inc.</td>
			<td>Fine wire microthermocouples (R-type)</td>
		</tr>
		<tr>
			<td>Unsheathed Fine Gauge T/C</td>
			<td>P13R-003</td>
			<td>Omega Engineering, Inc.</td>
			<td>Fine wire microthermocouples (R-type)</td>
		</tr>
		<tr>
			<td>Ceramic 2 hole round -5pk</td>
			<td>TRX-010364-6</td>
			<td>Omega Engineering, Inc.</td>
			<td>Ceramic tubes to hold the fine wire thermocouples</td>
		</tr>
		<tr>
			<td>Thermocouple extension wire</td>
			<td>EXTT-RS-24-100</td>
			<td>Omega Engineering, Inc.</td>
			<td>Thermocouple extension wire</td>
		</tr>
		<tr>
			<td>Male Female Connectors</td>
			<td>SHX-R/S-MF</td>
			<td>Omega Engineering, Inc.</td>
			<td>Connectors for R-type thermocouples&#160;</td>
		</tr>
		<tr>
			<td>Accessories</td>
			<td>MSRT-116-10</td>
			<td>Omega Engineering, Inc.</td>
			<td>Rubber tubes for maintaining grip for the ceramic tubes at the connectors&#39;s end</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Traverse mechanism</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>X slide, travel = 10 inch, 0.025 in/rev, limits, NEMA 17</td>
			<td>XN10-0100-E25-71</td>
			<td>Velmex Inc.</td>
			<td>Velmex unislide</td>
		</tr>
		<tr>
			<td>Vexta type 17, 1.8 deg/step 2phase, single shaft stepper motor</td>
			<td>PK245-01AA</td>
			<td>Velmex Inc.</td>
			<td>Stepper motor&#160;</td>
		</tr>
		<tr>
			<td>Mounting cleat, standard using 6-32 bolts</td>
			<td>XMC-2</td>
			<td>Velmex Inc.</td>
			<td>Mounting accessories for the given Velmex unislide</td>
		</tr>
		<tr>
			<td>6-32 X 7/16 SH Cap Screw for Xslide in X &#38; Y axis</td>
			<td>XMB-1</td>
			<td>Velmex Inc.</td>
			<td>Mounting accessories for the given Velmex unislide</td>
		</tr>
		<tr>
			<td>X slide, travel = 10 inch, 0.025 in/rev, limits, NEMA 17</td>
			<td>XN10-0100-E25-71</td>
			<td>Velmex Inc.</td>
			<td>Velmex unislide</td>
		</tr>
		<tr>
			<td>Vexta type 17, 1.8 deg/step 2phase, single shaft stepper motor</td>
			<td>PK245-01AA</td>
			<td>Velmex Inc.</td>
			<td>Stepper motor&#160;</td>
		</tr>
		<tr>
			<td>Mounting cleat, standard using 6-32 bolts</td>
			<td>XMC-2</td>
			<td>Velmex Inc.</td>
			<td>Mounting accessories for the given Velmex unislide</td>
		</tr>
		<tr>
			<td>6-32 X 7/16 SH Cap Screw for Xslide in X &#38; Y axis</td>
			<td>XMB-1</td>
			<td>Velmex Inc.</td>
			<td>Mounting accessories for the given Velmex unislide</td>
		</tr>
		<tr>
			<td>Control, 2 Axis programmable stepping motor control, 1 motor at a time</td>
			<td>VXM-2</td>
			<td>Velmex Inc.</td>
			<td>Stepper motor controller</td>
		</tr>
		<tr>
			<td>USB to RS232 DB9 Serial Communication cable 10 ft</td>
			<td>RPC-USB-RS232-3M</td>
			<td>Velmex Inc.</td>
			<td>Serial communication cable between the stepper motor controller and&#160; computer</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Data acquisition hardware</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NI 9214 16-Ch Isothermal TC, 24-bit C Series 
			Module for high accuracy thermocouple 
			measurements (includes terminal block)</td>
			<td>781510-01</td>
			<td>National Instruments</td>
			<td>Thermocouple data acquistion card</td>
		</tr>
		<tr>
			<td>Power Cord, AC, U.S., 120 VAC, 2.3 meters</td>
			<td>763000-01</td>
			<td>National Instruments</td>
			<td>Power cord for the 8 slot C-DAQ chassis</td>
		</tr>
		<tr>
			<td>cDAQ-9178, CompactDAQ chassis (8 slot 
			USB)</td>
			<td>781156-01</td>
			<td>National Instruments</td>
			<td>C-DAQ chassis for NI 9214 and NI 9239</td>
		</tr>
		<tr>
			<td>EMI Suppression Ferrite for NI 9229/39 BNC</td>
			<td>782801-01</td>
			<td>National Instruments</td>
			<td>Accessories for NI 9239 data acquistion card</td>
		</tr>
		<tr>
			<td>NI 9239 BNC, 4-Ch +/-10 V, 50 kS/s per channel</td>
			<td>780181-01</td>
			<td>National Instruments</td>
			<td>Data acquistion card for hot wire anemometer system</td>
		</tr>
		<tr>
			<td>cDAQ-9171, CompactDAQ chassis (1 slot USB)</td>
			<td>781425-01</td>
			<td>National Instruments</td>
			<td>C-DAQ chassis for NI 9214&#160;</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cameras</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nikon D7100 24.1 MP DX-Format CMOS Digital SLR with 18-105mm f/3.5-5.6 AF-S DX VR ED Nikkor Lens</td>
			<td>Nikon D7100</td>
			<td>Amazon</td>
			<td>Digital SLR camera for taking top-view flame photographs</td>
		</tr>
		<tr>
			<td>Canon EOS Rebel T5 DSLR CMOS Digital SLR Camera and DIGIC Imaging with EF-S 18-55mm f/3.5-5.6 IS Lens</td>
			<td>Canon EOS Rebel T5 DSLR&#160;</td>
			<td>Amazon</td>
			<td>Digital SLR camera for taking side-view flame photographs</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mass balance</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mettler-Toledo, MS32001L Balance Prec 32200g x 0.1g</td>
			<td>97035-654</td>
			<td>VWR</td>
			<td>Precision electronic&#160; mass balance&#160; for measuring&#160; average mass burning rate</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mini CTA system</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MiniCTA Anemometer Package for wire- and film- probes</td>
			<td>9054T0461</td>
			<td>Dantec Dynamics</td>
			<td>Hot wire system for measuring velocities and turbulence intesity at the wind tunnel outlet</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Wind tunnel equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1/2 in. x 4 ft. x 8 ft. C-3 Whole Piece Birch Domestic Plywood</td>
			<td>Model # 833185</td>
			<td>Home Depot</td>
			<td>Used to make the laboratory scale wind tunnel</td>
		</tr>
		<tr>
			<td>Woodgrain Millwork WM 206 11/16 in. x 11/16 in. x 96 in. Wood Pine Corner Moulding</td>
			<td>Model # 109610</td>
			<td>Home Depot</td>
			<td>Used to make the laboratory scale wind tunnel</td>
		</tr>
		<tr>
			<td>Extension Spring, Loop Ends, 6.562&#34; Overall Length, Pack of 6</td>
			<td>1330K26</td>
			<td>McMaster-Carr</td>
			<td>Used to make the laboratory scale wind tunnel</td>
		</tr>
		<tr>
			<td>Strainer Grade Wire Cloth, 30x30 Mesh, 0.0130&#34; wire diameter. 12&#34;x12&#34; sheet</td>
			<td>9241T41</td>
			<td>McMaster-Carr</td>
			<td>Used to make the laboratory scale wind tunnel</td>
		</tr>
		<tr>
			<td>Strainer Grade Wire Cloth, 40x40 Mesh, 0.0065&#34; wire diameter. 12&#34;x12&#34; sheet</td>
			<td>9241T42</td>
			<td>McMaster-Carr</td>
			<td>Used to make the laboratory scale wind tunnel</td>
		</tr>
		<tr>
			<td>Mobile Lift Table Foot-Operated, 600# Capacity, 10&#34; - 33&#34; Table Height</td>
			<td>2791T22</td>
			<td>McMaster-Carr</td>
			<td>Table to hold the experimental setup</td>
		</tr>
		<tr>
			<td>ebm-papst p/n: G3G250-MW75-05 (EC Centrifugal blower, 200-240V, 3-phase, 50/60Hz, M3G112-EA motor, 2.2kW)</td>
			<td>G3G250-MW75-05</td>
			<td>Ebm papst</td>
			<td>Blower for the wind tunnel</td>
		</tr>
		<tr>
			<td>ebm-papst p/n: HX0C-003-000-04 (Controller)</td>
			<td>HX0C-003-000-04</td>
			<td>Ebm papst</td>
			<td>Pulse width modulation controller for controlling the speed of the blower</td>
		</tr>
		<tr>
			<td>8020 1&#8221; X 1&#8221; T-SLOTTED PROFILE&#160;</td>
			<td>8020-1010</td>
			<td>80/20 (Rankin Automation)</td>
			<td>Used to create a framework for the wind tunnel</td>
		</tr>
		<tr>
			<td>Momentive/GE Silicone Sealant RTV108, 10.1-oz Cartridge, Semi-Clear</td>
			<td>7545A472</td>
			<td>McMaster Carr</td>
			<td>Sealant for the wood</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>LabVIEW</td>
			<td>Contact vendor</td>
			<td>National Instruments</td>
			<td>Used for continuous temperature data acquistion and analysis. Alternatively used for positioning the thermocouple.</td>
		</tr>
		<tr>
			<td>Mettler Toledo mass balance software</td>
			<td>Contact vendor</td>
			<td>Mettler Toledo</td>
			<td>Used for measuring the mass loss rate of the condensed fuel wick / solid plate with time</td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td>Free download</td>
			<td>NIH, http://imagej.nih.gov/ij/</td>
			<td>Used for measuring the flame standoff distance and surface regression of the solid fuel plate</td>
		</tr>
		<tr>
			<td>Matlab</td>
			<td>Contact vendor</td>
			<td>Mathworks</td>
			<td>Used for post-processing of data</td>
		</tr>
		<tr>
			<td>Fortran 90/95</td>
			<td>Contact vendor</td>
			<td>The Fortran company</td>
			<td>Used for post-processing of data</td>
		</tr>
		<tr>
			<td>MATERIALS</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol&#160;</td>
			<td>UMD Chem Store</td>
			<td>NA</td>
			<td>Liquid fuel</td>
		</tr>
		<tr>
			<td>Ethanol&#160;</td>
			<td>UMD Chem Store</td>
			<td>NA</td>
			<td>Liquid fuel</td>
		</tr>
		<tr>
			<td>safety glasses</td>
			<td>UMD Chem Store</td>
			<td>NA</td>
			<td>Used for safety purpose</td>
		</tr>
		<tr>
			<td>spray bottle</td>
			<td>UMD Chem Store</td>
			<td>NA</td>
			<td>Used for carrying water in case of emergency</td>
		</tr>
		<tr>
			<td>Syringe 60 cc</td>
			<td>UMD Chem Store</td>
			<td>NA</td>
			<td>Used for soaking the liquid fuel wick with liquid fuels</td>
		</tr>
		<tr>
			<td>Optically Clear Cast Acrylic Sheet, 1/8&#34; Thick, 24&#34; X 48&#34;</td>
			<td>Mc master carr</td>
			<td>8560K262</td>
			<td>Solid fuel PMMA</td>
		</tr>
		<tr>
			<td>Loctite Proxy Pak (Hi-temp adhesive)</td>
			<td>Mc master carr</td>
			<td>7556A33</td>
			<td>Used for covering the sides of the wick with aluminum foil</td>
		</tr>
		<tr>
			<td>Hi-Temp Aerosol Spray Paint (Black)</td>
			<td>Mc master carr</td>
			<td>7832T1</td>
			<td>Used for painting the insulation&#160;</td>
		</tr>
		<tr>
			<td>Self-Igniting Economy Propane Gas Torch Adjustable Flame, 4179 Btu/hr</td>
			<td>Mc master carr</td>
			<td>78245A3</td>
			<td>Propane torch for igniting the solid fuel plate</td>
		</tr>
		<tr>
			<td>Heat-Resistant Cotton Glove W/Nitrile Coating, 400 Deg F Max Temp, 10&#34; Lg, Large</td>
			<td>Mc master carr</td>
			<td>56025T1</td>
			<td>Used for safety purpose</td>
		</tr>
		<tr>
			<td>Modular Protective Screen with Tie-on Curtain, 6&#39;Height x 4&#39;Width Abrasion-Resistant Fiberglass</td>
			<td>Mc master carr</td>
			<td>9145T84</td>
			<td>Fire-resistant curtain for the background</td>
		</tr>
		<tr>
			<td>Multipurpose Aluminium Alloy 6061 .125&#34; thick, 12&#34;X24&#34;</td>
			<td>Mc master carr</td>
			<td>89015K28</td>
			<td>Used for holding the insulation</td>
		</tr>
		<tr>
			<td>Marine grade plywood 1/2&#34; thick, 12&#34; X 24&#34;</td>
			<td>Mc master carr</td>
			<td>1125T32</td>
			<td>Used for holding the experimental setup</td>
		</tr>
		<tr>
			<td>Multipurpose Aluminium Alloy 6061 U-channel, 2&#34; base X 1-1/4&#34; legs, 1&#39; length</td>
			<td>Mc master carr</td>
			<td>1630T473</td>
			<td>Used for holding the aluminum plate, insulation and wick</td>
		</tr>
		<tr>
			<td>Architectural Anodized Aluminium (Alloy 6063) 90 deg angle, 1/8&#34; Thk, 1/2&#34; X 1/2&#34; legs, 6&#39; L</td>
			<td>Mc master carr</td>
			<td>4630T21</td>
			<td>Used for holding the aluminum plate, insulation and wick</td>
		</tr>
		<tr>
			<td>Aluminium Inch T-Slotted Framing System Concealed 90 degree connector, for 1&#34; extrusion</td>
			<td>Mc master carr</td>
			<td>47065T155</td>
			<td>Used for holding the aluminum plate, insulation and wick</td>
		</tr>
		<tr>
			<td>Aluminium Inch T-Slotted Framing System Extended 90 degree bracket, Single, 4 Hole, for 1&#34; extrusion</td>
			<td>Mc master carr</td>
			<td>47065T175</td>
			<td>Used for holding the aluminum plate, insulation and wick</td>
		</tr>
		<tr>
			<td>Aluminium Inch T-Slotted Framing System Four-Slot single, 1&#34; solid extrusion, 4&#39; length</td>
			<td>Mc master carr</td>
			<td>47065T101</td>
			<td>Used for holding the aluminum plate, insulation and wick</td>
		</tr>
		<tr>
			<td>1/2&#34; X 48&#34; X 36&#34; (Superwool 607 insulation board) 1 carton containing 12 sheets</td>
			<td>Mccormick Insulation</td>
			<td>Superwool 607&#160;</td>
			<td>Insulation material for making the wick and the wick holder</td>
		</tr>
	</tbody>
</table>

experimental methodology for estimation of local heat fluxes and burning rates in steady laminar boundary layer diffusion flames

Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex interactions occurring at the interface between gas-phase flames and condensed-phase fuels. The current research provides a technique to explore the dynamic relationship between a combustible condensed fuel surface and gas-phase flames in laminar boundary layers. Experiments have previously been conducted in both forced and free convective environments over both solid and liquid fuels. A unique methodology, based on the Reynolds Analogy, was used to estimate local mass burning rates and flame heat fluxes for these laminar boundary layer diffusion flames utilizing local temperature gradients at the fuel surface. Local mass burning rates and convective and radiative heat feedback from the flames were measured in both the pyrolysis and plume regions by using temperature gradients mapped near the wall by a two-axis traverse system. These experiments are time-consuming and can be challenging to design as the condensed fuel surface burns steadily for only a limited period of time following ignition. The temperature profiles near the fuel surface need to be mapped during steady burning of a condensed fuel surface at a very high spatial resolution in order to capture reasonable estimates of local temperature gradients. Careful corrections for radiative heat losses from the thermocouples are also essential for accurate measurements. For these reasons, the whole experimental setup needs to be automated with a computer-controlled traverse mechanism, eliminating most errors due to positioning of a micro-thermocouple. An outline of steps to reproducibly capture near-wall temperature gradients and use them to assess local burning rates and heat fluxes is provided.

Watch this Scientific Journal Video about Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames at JoVE.com

Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames

We describe the use of micro-thermocouples to estimate local temperature gradients in steady laminar boundary layer diffusion flames. By extension of the Reynolds Analogy, local temperature gradients can be further used to estimate the local mass burning rates and heat fluxes in such flames with high accuracy.

Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex ...

Research

JoVE Journal

Engineering

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Measurement of Outgassing Rates of Steels

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Experimental Implementation of a New Composite Fabrication Method: Exposing Bare Fibers on the Composite Surface by the Soft Layer Method

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Design and Characterization Methodology for Efficient Wide Range Tunable MEMS Filters

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Measurements of Waves in a Wind-wave Tank Under Steady and Time-varying Wind Forcing

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Determination of the Excitation and Coupling Rates Between Light Emitters and Surface Plasmon Polaritons

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Atmospheric Pressure Fabrication of Large-Sized Single-Layer Rectangular SnSe Flakes

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The Diffusion of Passive Tracers in Laminar Shear Flow

A simple method to experimentally observe and measure the dispersion of a passive tracer in a laminar fluid flow is described. The method consists of ...

Experimental Procedure for Laboratory Studies of In Situ Burning : Flammability and Burning Efficiency of Crude Oil

Experimental Procedure for Laboratory Studies of In Situ Burning : Flammability and Burning Efficiency of Crude Oil

A new method for the simultaneous study of the flammability and burning efficiency of fresh and weathered crude oil through two experimental laboratory ...