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1
Wang, En Yu, Jing Qin, Xing Xiang, and Jin Xiang Wu. "Influence of Jet Angle on Diffusion Flames in Centrifugal Field." Applied Mechanics and Materials 694 (November 2014): 181–86. http://dx.doi.org/10.4028/www.scientific.net/amm.694.181.
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Diffusion combustion of propane and air in a rotational combustor was simulated by three-dimensional numerical model based on FLUENT. Influence of centrifugal field on the flame shapes and temperatures were discussed under various jet angles changing in the plane perpendicular to the rotational axis. The flame is compressed when the value of jet angle θ is less 90°, otherwise, the flame is stretched when |θ|>90°. When θ<90°, the deflection of flame becomes larger with an increase of θ. As contrasted to positive θ cases, the zones of high temperature in combustion chamber corresponding to negative are larger, and the maximal flame temperatures are likewise larger. The negative jet angle is useful to flame stability. External fluid is an important factor influence the distribution of temperature in combustion chamber.
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Masjudin and Wei-Chin Chang. "Combustion performance of the premixed and diffusion burners with used lubricating oil and used cooking oil as fuel." Modern Physics Letters B 33, no. 14n15 (May 28, 2019): 1940005. http://dx.doi.org/10.1142/s0217984919400050.
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This work investigated combustion performance of the premixed and diffusion burners by measuring flame temperature and gas emissions with used lubricating oil (ULO) and used cooking oil (UCO). Air–fuel ratio (AFR) is an important parameter to investigate combustion performance. Flame temperatures and gas emissions of the burners were examined to know the combustion behavior. The results found were that the flame temperatures in the premixed burner were higher than the diffusion burner at all the AFRs. The maximum flame temperature was obtained at AFR = 16 at all types of burners and fuel blending ratios. The highest flame temperature was [Formula: see text], which occurred when using 100% ULO with premixed burner at AFR = 16. By adding UCO into ULO, the flame temperatures can be decreased. The premixed burner produced 86.67% and 71.23% less CO and HC emissions, respectively, than the diffusion burner, in contrast, the premixed burner formed 26.31% and 54.7% higher [Formula: see text] and [Formula: see text] emissions, respectively, than the diffusion burner.
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Petrucci, Giuseppe A., Denise Imbroisl, Robert D. Guenard, Benjamin W. Smith, and Jame D. Winefordner. "High-Spatial-Resolution OH Rotational Temperature Measurements in an Atmospheric-Pressure Flame Using an Indium-Based Resonance Ionization Detector." Applied Spectroscopy 49, no. 5 (May 1995): 655–59. http://dx.doi.org/10.1366/0003702953964020.
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The use of a resonance ionization photon detector (RID) is described for the measurement of flame temperatures with a spatial resolution of less than 100 μm. The detector, based on the two-step excitation of indium atoms, with subsequent collisional ionization, was used to record rotational excitation scans of OH in an atmospheric-pressure acetylene/air flame. The OH excitation spectra were recorded by scanning an “excitation” laser in the A2σ+ ← X2II i (1, 0) vibronic band in the wavelength range, 281–288 nm, while simultaneously illuminating the same flame region with the “detection” laser, tuned to the 6 p2 P3/2 → 10 d2. D5/2 excited-state transition of In at 786.44 nm. The excitation and detection laser beams were made orthogonal in the flame, defining the resolution to be limited by the waist of the excitation beam (100 μm), whose diameter was always smaller than the detection laser beam. A temperature profile of the flame is recorded with the use of both the RID approach and a more conventional laser-induced fluorescence (LIF) approach for comparison. A more structured temperature profile is recorded with the RID owing to its high spatial resolution, whereas the LIF method, which is inherently a line-of-sight method, produces a rather featureless temperature distribution across the flame. Anomalously high flame temperatures were recorded at the flame edge with the RID. The cause of these high flame temperatures has not been determined.
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Wotton, B. Mike, James S. Gould, W. Lachlan McCaw, N. Phillip Cheney, and Stephen W. Taylor. "Flame temperature and residence time of fires in dry eucalypt forest." International Journal of Wildland Fire 21, no. 3 (2012): 270. http://dx.doi.org/10.1071/wf10127.
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Temperature profiles of flames were measured using arrays of thermocouples on towers located in experimental bushfires of varying intensity, carried out in dry eucalypt forest of different fuel age and structure. In-fire video of flame-front passage and time series data from very fine exposed thermocouples were used to estimate the duration of passage of the main flaming front in these experimental fires. Flame temperature measured at points within the flame was found to vary with height; maximum flame temperature was greater in the tall shrub fuel than in the low shrub fuel sites. A model to estimate flame temperature at any height within a flame of a specific height was developed. The maximum flame temperature observed was ~1100°C near the flame base and, when observation height was normalised by flame height, flame temperature exponentially decreased to the visible flame tip where temperatures were ~300°C. Maximum flame temperature was significantly correlated with rate of spread, fire intensity, flame height and surface fuel bulk density. Average flame-front residence time for eucalypt forest fuels was 37 s and did not vary significantly with fine fuel moisture, fuel quantity or bulk density.
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Rajković, Miloš, Goran Malidža, Strahinja Stepanović, Marko Kostić, Kristina Petrović, Mirko Urošević, and Sava Vrbničanin. "Influence of Burner Position on Temperature Distribution in Soybean Flaming." Agronomy 10, no. 3 (March 13, 2020): 391. http://dx.doi.org/10.3390/agronomy10030391.
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The main objective of this study was to identify optimal burner orientation for a newly designed flame cultivator by quantifying the flame temperature distributions of cross, back, and parallel position of burners at different heights of the soybean canopy (distance from the soil surface). Flame temperatures were measured within-row for three burner orientations at seven propane doses (20–100 kg/ha) and eight different canopy heights (0–18 cm above soil surface). Soybean plants in V3 growth stage were flamed with the same doses and burner orientations, and 28 days after treatment (DAT) crop injury (0%–100%), plant height (cm), dry matter (g) and grain yield (t/ha) were assessed. All three burner orientations had high flame temperatures at lower canopy heights (<6 cm high) that gradually decreased with increasing canopy height (6–18 cm). Measured temperatures ranged from 33 to 234 ℃ for cross flaming, 29 to 269 ℃ for back flaming and 23 to 155 ℃ for parallel flaming, with high variability in temperature patterns. Back flaming generated flame temperatures above 100℃ at a lower propane dose (27 kg/ha) compared to cross and parallel flaming (40 and 50 kg/ha). For all tested parameters, parallel and cross flaming had better impact on soybeans than back flaming, but for weed control in crop rows, cross flaming is recommended.
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Huang, Haiming, and Weijie Li. "Influence factors of methane-air counterflow diffusion flame." Thermal Science 21, no. 4 (2017): 1689–93. http://dx.doi.org/10.2298/tsci160506054h.
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This paper investigates the influences of pressures, velocities, and temperatures of gases at nozzles on the temperature of flame. Considering that temperature and species mass fractions are functions of axial co-ordinates, a quasi-1-D mathematic model in cylindrical co-ordinates for counterflow diffusion flame is built. The results show that the pressure, velocities, and temperatures of gases can affect the temperature distributions of methane-air counterflow diffusion flame, and that the influence of the variations of velocities at two nozzles on the movement of the starting reaction interface is most significant in these factors.
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Salman, Ahmed M., Ibrahim A. Ibrahim, Hamada M. Gad, and Tharwat M. Farag. "Effects of Air Temperature on Combustion Characteristics of LPG Diffusion Flame." Materials Science Forum 1008 (August 2020): 128–38. http://dx.doi.org/10.4028/www.scientific.net/msf.1008.128.
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In the present study, the combustion characteristics of LPG gaseous fuel diffusion flame at elevated air temperatures were experimentally investigated. An experimental test rig was manufactured to examine a wide range of operating conditions. The investigated parameters are the air temperatures of 300, 350, 400, 450, and 500 K with constant percentage of nitrogen addition in combustion air stream of 5 % to give low oxygen concentration of 18.3 % by mass at constant air swirl number, air to fuel mass ratio, and thermal load of 1.5, 30, and 23 kW, respectively. The gaseous combustion characteristics were represented as axial and radial temperatures distributions, temperatures gradient, visible flame length and species concentrations. The results indicated that as the air temperature increased, the chemical reaction rate increased and flame volume decreased, the combustion time reduced leading to a reduction in flame length. The NO concentration reaches its maximum values near the location of the maximum centerline axial temperature. Increasing the combustion air temperature by 200 K, the NO consequently O2 concentrations are increased by about % 355 and 20 % respectively, while CO2 and CO concentrations are decreased by about % 21 and 99 % respectively, at the combustor end.
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Gupta, A. K., S. Bolz, and T. Hasegawa. "Effect of Air Preheat Temperature and Oxygen Concentration on Flame Structure and Emission." Journal of Energy Resources Technology 121, no. 3 (September 1, 1999): 209–16. http://dx.doi.org/10.1115/1.2795984.
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The structure of turbulent diffusion flames with highly preheated combustion air (air preheat temperature in excess of 1150°C) has been obtained using a specially designed regenerative combustion furnace. Propane gas was used as the fuel. Data have been obtained on the global flame features, spectral emission characteristics, spatial distribution of OH, CH, and C2 species, and pollutant emission from the flames. The results have been obtained for various degrees of air preheat temperatures and O2 concentration in the air. The color of the flame was found to change from yellow to blue to bluish-green to green over the range of conditions examined. In some cases a hybrid color flame was also observed. The recorded images of the flame photographs were analyzed using color-analyzing software. The results show that thermal and chemical flame behavior strongly depends on the air preheat temperature and oxygen content in the air. The flame color was observed to be bluish-green or green at very high air preheat temperatures and low-oxygen concentration. However, at high-oxygen concentration, the flame color was yellow. The flame volume was found to increase with increase in air-preheat temperature and decrease in oxygen concentration. The flame length showed a similar behavior. The concentrations of OH, CH, and C2 increased with an increase in air preheat temperatures. These species exhibited a two-stage combustion behavior at low-oxygen concentration and single-stage combustion behavior at high-oxygen concentration in the air. Stable flames were obtained for remarkably low equivalence ratios, which would not be possible with normal combustion air. Pollutant emission, including CO2 and NOx, was much lower with highly preheated combustion air at low O2 concentration than with normal air. The results also suggest uniform flow and flame thermal characteristics with conditioned, highly preheated air. Highly preheated air combustion provides much higher heat flux than normal air, which suggests direct energy savings and a reduction of CO2 to the environment. Colorless oxidation of fuel has been observed under certain conditions.
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Jeon, Min-Kyu, and Nam Il Kim. "Fuel pyrolysis and its effects on soot formation in non-premixed laminar jet flames of methane, propane, and DME." Mathematical Modelling of Natural Phenomena 13, no. 6 (2018): 56. http://dx.doi.org/10.1051/mmnp/2018052.
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High-temperature combustion techniques have recently attracted interest with regard to the improvement of the thermal efficiency of combustion systems. Fuel pyrolysis is an important factor, as it can affect such flame structures at high temperatures. In this study, the pyrolysis of methane, propane, and dimethyl ether (DME) was measured and the results were compared with theoretical predictions. Pyrolyzed fuels were quenched to room temperature before being introduced onto the burner. Thus, the pyrolysis effects on laminar non-premixed jet flames could be distinguished from many other complex thermal effects. It was found that the flame length was not notably extended in spite of the great increase in the volumetric flow rates resulting from the pyrolysis. In contrast, fuel pyrolysis could significantly affect the soot formation process,and the number of smoke points could be sharply reduced depending on the pyrolysis temperature. Distributions of the luminous intensity and scattering intensity levels in the soot region were discussed in terms of the soot temperatures obtained with a two-color method. Although the adiabatic flame temperatures of the pyrolyzed fuels were theoretically increased, the actual soot temperatures could be reduced when the soot particles were excessively formulated, as in the case with propane flames.
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Zhang, Hongyi, William R. Graves, and Alden M. Townsend. "Water Loss and Survival of Stem Cuttings of Two Maple Cultivars Held in Subirrigated Medium at 24 to 33 °C." HortScience 32, no. 1 (February 1997): 129–31. http://dx.doi.org/10.21273/hortsci.32.1.129.
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We determined transpiration rate, survival, and rooting of unmisted, softwood cuttings of `Autumn Flame' red maple (Acer rubrum L.) and `Indian Summer' Freeman maple (Acer ×freemanii E. Murray). Effects of perlite at 24, 30, and 33 °C were assessed to determine whether responses of cuttings would be consistent with cultivar differences in resistance to root-zone heat previously shown with whole plants. During 7 d, cutting fresh mass increased by ≈20% at all temperatures for `Autumn Flame' red maple, but fresh mass of `Indian Summer' Freeman maple decreased by 17% and 21% at 30 and 33 °C, respectively. The percentage of cuttings of `Indian Summer' that were alive decreased over time and with increasing temperature. Transpiration rate decreased during the first half of the treatment period and then increased to ≈1.1 and 0.3 mmol·m-2·s-1 for `Autumn Flame' and `Indian Summer', respectively. Mean rooting percentages over temperatures for `Autumn Flame' and `Indian Summer' were 69 % and 16%, respectively. Mean rooting percentages at 24, 30, and 33 °C over both cultivars were 74%, 29%, and 25%, respectively. Over temperatures, mean root count per cutting was 41 and seven, and mean root dry mass per cutting was 4.9 and 0.4 mg, for `Autumn Flame' and `Indian Summer', respectively. Use of subirrigation without mist to root stem cuttings was more successful for `Autumn Flame' than for `Indian Summer'. Temperature × cultivar interactions for cutting fresh mass and the percentage of cuttings remaining alive during treatment were consistent with previous evidence that whole plants of `Autumn Flame' are more heat resistant than plants of `Indian Summer'. Mass and survival of stem cuttings during propagation in heated rooting medium may serve as tools for screening for whole-plant heat resistance among maple genotypes.
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Kim, J. S., and M. A. Cappelli. "An experimental study of the temperature and stoichiometry dependence of diamond growth in low pressure flat flames." Journal of Materials Research 10, no. 1 (January 1995): 149–57. http://dx.doi.org/10.1557/jmr.1995.0149.
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A study of the temperature and stoichiometry dependence of diamond synthesis in low pressure premixed acetylene-oxygen flames is presented. A specially designed low pressure flat flame operating at 40 Torr is employed to deposit diamond films uniformly over areas of at least 2 cm2. Under optimized conditions of substrate temperatures and flame equivalence ratios, high quality translucent diamond that is well faceted is synthesized exhibiting first-order Raman fullwidths (half maximum) of about 2.5 cm−1. Diamond growth rates under these optimum conditions are approximately 4 μm/h. The film growth rate is found to drop off substantially at high substrate temperatures, with little or no carbon deposited beyond a temperature of 1070 °C. The growth behavior in response to changes in flame equivalence ratio and substrate temperature is discussed in terms of the possible role that oxygen-containing species may have on surface chemistry. The results described here are also used to project a base cost for manufacturing diamond under these process conditions.
12
Lee, Dae-Hee, and B. Bollinger. "The Development of Combustion Laboratory Test Apparatus for Mechanical Engineers." International Journal of Mechanical Engineering Education 24, no. 1 (January 1996): 1–10. http://dx.doi.org/10.1177/030641909602400101.
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A combustion laboratory test apparatus has been developed and put to use in the mechanical engineering measurement course at the California State University, Sacramento. The objectives of this apparatus are to study the characteristics of a premixed flame for a range if air/propane mixtures (from near stoichiometric to rich to highly rich) and to examine the principles of chemical thermodynamics of combustion by comparing the calculated adiabatic flame temperature to the measured adiabatic flame temperature, and by doing an energy balance on the flame. The apparatus consists of a burner that is used to ignite a regulated air/propane mixture. A thin wire thermocouple is used to measure both the flame temperature profiles and the adiabatic flame temperatures for two different air/propane mixtures (rich and highly rich). Furthermore, a copper tank containing water is heated by a near-stoichiometric mixture flame, causing heat transfer from the flame to the water. The results show that approximately 83% of the heat released from the near stoichiometric flame is transferred to the water in the copper tank.
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Alkali, Adam Umar, Turnad Lenggo Gintar, Hasan Fawad, and Ahmad Majdi Abdulrani. "Influence of Preheat Flux on the Microstructure of 304 Stainless Steel." Applied Mechanics and Materials 465-466 (December 2013): 1287–91. http://dx.doi.org/10.4028/www.scientific.net/amm.465-466.1287.
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An experimental investigation had been carried out for heating-only on samples of type 304 stainless steel with oxyacetylene gas flame set to neutral flame with temperature 27000-3300°C. The flame effect on surface integrity was investigated in terms of hardness test and microstructural characterization. Substrates temperatures were raised to 355°C as well as 550°C while oxyacetylene flame travels at approximate of 74 mm/min along the span of the material. The experimental outcome revealed the microstructures from two examined conditions: Initial grain structures as well as grain structure when flame heated to 355°C has retained austenite crystal structure while flame heating to 5000-550°C revealed chromium carbide precipitates. Within the investigated temperature range of 5000-550°C, preheating was evidently proven to result to sensitization.
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Bhattacharjee, S., M. King, W. Cobb, R. A. Altenkirch, and K. Wakai. "Approximate Two-Color Emission Pyrometry." Journal of Heat Transfer 122, no. 1 (August 2, 1999): 15–20. http://dx.doi.org/10.1115/1.521431.
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Approximate methods for the determination of a temperature field using pure emission pyrometry applied to a two-dimensional nonoptically thin flame without variation along a line of sight are presented. In the absence of an absorption measurement, emission pyrometry depends on theoretical spectral information. Limitations of existing techniques stem from the fact that spectral information is a function of temperature only for the optically thin situation, by and large the situation to which current techniques apply, and temperatures above 1000 K. Through extensive narrow-band calculation using a simulated flame over polymethylmethacrylate, we show that the spectral information contained in the equivalent bandwidth ratio is approximately a constant for the 2.8 μm/1.8 μm band pair and appropriate bandwidths. The constant can be evaluated from emission measurements at a point where the temperature is known or can be estimated using, e.g., the maximum flame temperature of a simulated flame and the peak band intensities. The temperature field evaluated with this approximately constant value of the equivalent bandwidth ratio, Ar, is accurate to within five percent for temperatures down to 450 K. [S0022-1481(00)02601-3]
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Zhao, Shilong, Fan Yuxin, and Zhang Xiaolei. "Influence of parameters on flame expansion in a high-speed flow: Experimental and numerical study." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 234, no. 8 (December 30, 2019): 1122–30. http://dx.doi.org/10.1177/0957650919896504.
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Flameholder-stabilized flames are conventional and also commonly used in propulsion and various power generation fields to maintain combustion process. The characteristics of flame expansion were obtained with various blockage ratios, which were observed to be highly sensitive to inlet conditions such as temperatures and velocities. Experiments and simulations combined methodology was performed; also the approach adopted on image processing was calculated automatically through a program written in MATLAB. It was found that the change of flame expansion angle indicated increasing fuel supply could contribute to the growth of flame expansion angle in lean premixed combustion. Besides, the influence of inlet velocity on flame expansion angle varies with different blockage ratios, i.e. under a small blockage ratio (BR = 0.1), flame expansion angle declined with the increase of velocity; however, under a larger blockage ratio (BR = 0.2 or 0.3), flame expansion angle increased firstly and then decreased with the increasing velocity. Likewise, flame expansion angle increased firstly and then decreased with the increasing temperature under BR = 0.2/0.3. In addition, flame expansion angle was almost the same for BR = 0.2 and BR = 0.3 at a higher temperature (900 K), and both of which were bigger than BR = 0.1. Overall, BR = 0.2 is the best for increasing flame expansion angle and reducing total pressure loss. The influence of velocity and temperature on flame expansion angle found from this research are vital for engineering practice and for developing a further image processing method to measure flame boundary.
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Hsu, Ching Min, Dickson Bwana Mosiria, and Wei Chih Jhan. "Flow and Temperature Characteristics of a 15° Backward-Inclined Jet Flame in Crossflow." Energies 12, no. 1 (December 31, 2018): 132. http://dx.doi.org/10.3390/en12010132.
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The flow and flame characteristics of a 15° backward-inclined jet flame in crossflow were investigated in a wind tunnel. The flow structures, flame behaviors, and temperature fields were measured. The jet-to-crossflow momentum flux ratio was less than 7.0. The flow patterns were investigated using photography and Mie-scattering techniques. Meanwhile, the velocity fields were observed using particle image velocimetry techniques, whereas the flame behaviors were studied using photographic techniques. The flame temperatures were probed using a fine-wire R-type thermocouple. Three flame modes were identified: crossflow dominated flames, which were characterized by a blue flame connected to a down-washed yellow recirculation flame; transitional flames identified by a yellow recirculation flame and an elongated yellow tail flame; and detached jet dominated flames denoted by a blue flame base connected to a yellow tail flame. The effect of the flow characteristics on the combustion performance in different flame regimes is presented and discussed. The upwind shear layer of the bent jet exhibited different coherent structures as the jet-to-crossflow momentum flux ratio increased. The transitional flames and detached jet dominated flames presented a double peak temperature distribution in the symmetry plane at x/d = 60. The time-averaged velocity field of the crossflow dominated flames displayed a standing vortex in the wake region, whereas that of the detached jet dominated flames displayed a jet-wake vortex and a wake region source point.
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Lee, Jeonghoon, Jason Olfert, Igor S. Altman, and Mansoo Choi. "Determination of particle temperatures in a silica-generating counterflow flame via flame emission measurements." International Journal of Heat and Mass Transfer 53, no. 1-3 (January 2010): 564–67. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2009.09.036.
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Chen, Hanyu, Yaoqi Hou, Xi Wang, Zhixiang Pan, and Hongming Xu. "Characterization of In-Cylinder Combustion Temperature Based on a Flame-Image Processing Technique." Energies 12, no. 12 (June 21, 2019): 2386. http://dx.doi.org/10.3390/en12122386.
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The analysis of in-cylinder combustion temperatures using flame image processing technology is reliable. This method can accurately, intuitively, and in real time obtain the temperature field distribution law of the combustion flame in the cylinder, so we can more deeply understand the characteristics of the combustion process of internal combustion engines. In this paper, a high-speed charge-coupled device (CCD) camera is used to record an in-cylinder combustion image, which is calculated and corrected according to the principle of three primary color temperature measurement, and the temperature field distribution of the combustion flame in the diesel engine cylinder is analyzed in detail. In addition, the temperature of the typical combustion flame images under the open-cycle and closed cycle conditions is compared by the CMS2002 measurement and MATLAB program, respectively. The results show that the accuracy of the MATLAB program is acceptable in general but not entirely acceptable in a few ways.
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Butler, Bret W., and Ted Putnam. "Fire shelter performance in simulated wildfires: an exploratory study." International Journal of Wildland Fire 10, no. 1 (2001): 29. http://dx.doi.org/10.1071/wf01019.
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Fire shelters are required equipment for most wildland firefighters in the United States. In this study we report flame emissive power and temperatures inside and outside fire shelters placed in one prescribed fire, five experimental field fires, and one laboratory fire. Energy levels radiated by flames varied from 70 to 150 kW m–2 and lasted less than 10 min. Maximum fire shelter internal air temperatures reached 250˚C and occurred during the test with the maximum external air temperatures (1000˚C). Air temperatures inside the fire shelters did not show a strong dependence on flame radiant power, rather they correlated most strongly with external air temperature. We compare measurements from these tests with results reported by others. The data clearly indicate (1) the capability of the fire shelter to protect the occupant from radiant heating; (2) the susceptibility of the current design to convective heating; and (3) the significant decrease in burn injury when fire shelters are used.
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Li, Jianzhong, Jian Chen, Li Yuan, and Ge Hu. "Effect of Airflow Temperature on the Formation of Initial Flame Kernel and the Propagation Characteristics of Flame." International Journal of Aerospace Engineering 2018 (December 17, 2018): 1–12. http://dx.doi.org/10.1155/2018/7286705.
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Using liquid RP-3 aviation kerosene as the fuel to study, the effect of airflow temperature on the formation of initial flame kernel during the ignition of spray combustion and on the propagation characteristics of flame was investigated. Combining high-speed camera and dynamic temperature acquisitions at the outlet of combustor, the internal triggering mode was used under a constant fuel flow rate and airflow velocity. This combined system simultaneously recorded the formation of initial flame kernel, flame propagation, and outlet temperature variation of combustor under different airflow temperatures. MATLAB software was used to obtain the reaction zones at different moments and to analyze the effects of airflow temperature on morphological characteristics such as flame area, perimeter-to-area ratio, maximum length-to-height ratio, equivalent mean length-to-height ratio, mass center, and centroid. According to the growth rate in flame area, the ignition process can be divided into three stages: formation of flame kernel, rapid development of flame, and stable development of flame. Airflow temperature not only affects the formation time of flame kernel but also affects the growth rate of flame area. During the development of flame, the movements of mass center and centroid are irregular, and their positions do not coincide with each other. However, the overall moving trends are consistent. With the increase of the airflow temperature, the position, where the flame kernel is gradually formed, moves closer to the center of the end face of spark plug. The force of airflow on flame is the main factor that increases the flame area and heat-release rate. Therefore, the folds around the flame edge mainly result from the stretching under the action of airflow. With the increase in airflow temperature, the heat release of the initial flame kernel increases, and the ratio of perimeter to area as a characterization parameter increases by 8%, 86%, and 33%, respectively. In addition, the maximum outlet temperature rise increased by about 53%, 73.5%, and 0.65%, respectively. Meanwhile, the maximum rate of temperature rise increased by about 42.8%, 57%, and 5.1%, respectively.
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Li, Man Hou, Shou Xiang Lu, Jin Guo, and Kwok Leung Tsui. "Study on Flame Spread over Aviation Kerosene and Diesel." Advanced Materials Research 1016 (August 2014): 587–91. http://dx.doi.org/10.4028/www.scientific.net/amr.1016.587.
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Flame spreading over liquid fuels is a common phenomenon involving in accidental fuel leakage in aircraft crash or oil tanker which may result in many casualties and economic losses. Comparative experiments are conducted concerning flame spread over aviation kerosene (RP5) and 0# diesel at a variety of initial fuel temperatures. The threshold value of initial fuel temperature for liquid-phase and gas-phase controlled flame spread is approximately 17 °C larger than liquid’s flashpoint for both oils. For a given initial fuel temperature, due to low volatility and ignitability of 0# diesel, its flame spread rate is smaller than that of RP5, while the length of the horizontal subsurface convection flow is larger. Given the difference in flame speed, fire accidents for RP5 are potentially more hazardous than those of 0# diesel. Moreover, the variation trend of subsurface convection flow length falls nearly linearly with the initial fuel temperature for both fuels.
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Gu¨lder, O¨ L. "Flame Temperature Estimation of Conventional and Future Jet Fuels." Journal of Engineering for Gas Turbines and Power 108, no. 2 (April 1, 1986): 376–80. http://dx.doi.org/10.1115/1.3239914.
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An approximate formula is presented by means of which the adiabatic flame temperature of jet fuel-air systems can be calculated as functions of pressure, temperature, equivalence ratio, and hydrogen to carbon atomic ratio of the fuel. The formula has been developed by fitting of the data from a detailed chemical equilibrium code to a functional expression. Comparisons of the results from the proposed formula with the results obtained from a chemical equilibrium code have shown that the average error in estimated temperatures is around 0.4 percent, the maximum error being less than 0.8 percent. This formula provides a very fast and easy means of predicting flame temperatures as compared to thermodynamic equilibrium calculations, and it is also applicable to diesel fuels, gasolines, pure alkanes, and aromatics as well as jet fuels.
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Giurcan, Venera, Domnina Razus, Maria Mitu, and Dumitru Oancea. "Numerical study of the laminar flame propagation in ethane-air mixtures." Open Chemistry 12, no. 3 (March 1, 2014): 391–402. http://dx.doi.org/10.2478/s11532-013-0387-0.
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AbstractThe structure of premixed free one-dimensional laminar ethane-air flames was investigated by means of numerical simulations performed with a detailed mechanism (GRI-Mech version 3.0) by means of COSILAB package. The work provides data on ethane-air mixtures with a wide range of concentrations ([C2H6] = 3.0–9.5 vol.%) at initial temperatures between 300 and 550 K and initial pressures between 1 and 10 bar. The simulations deliver the laminar burning velocities and the profiles of temperature, chemical species concentrations and heat release rate across the flame front. The predicted burning velocities match well the burning velocities measured in various conditions, reported in literature. The influence of initial concentration, pressure and temperature of ethane-air mixtures on maximum flame temperature, heat release rate, flame thickness and peak concentrations of main reaction intermediates is examined and discussed.
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Mane, Deshmukh, Krishnamoorthy Arunagiri, and Virendra Bhojwani. "Effect of mixture velocity for given equivalence ratio on flame development in Swiss roll combustor." Thermal Science, no. 00 (2019): 263. http://dx.doi.org/10.2298/tsci180604263m.
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Small-scale power generation using heat energy from hydrocarbon (HC) fuels is a proven technology. In this study, we analyzed 2D flame development in meso-scale Swiss roll combustor (SW). A mixture of 60% butane and 40 % propane was used (0.25-0.55 l/min). During all the analyses, equivalence ratio (1.1) was kept constant by adjusting air quantity against fuel quantity. The effect of increase in the mixture velocity on the development of flame shapes/patterns was monitored. We found different patterns of flame, e.g., Planar, Concave, conical, with the increase in mixture velocity. Increase in combustion chamber temperature was also noted. No Flashback was observed and blowout was observed with very high mixture velocity. Combustion chamber temperatures were found to be increasing with the increase in mixture velocity at the same equivalence ratio. Elongation of the flame was observed because of the increased flow velocity. Heat recirculation to the reactants enhances flame characteristics.
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Kitagawa, K., N. Konishi, N. Arai, and A. K. Gupta. "Temporally Resolved Two-Dimensional Spectroscopic Study on the Effect of Highly Preheated and Low Oxygen Concentration Air on Combustion." Journal of Engineering for Gas Turbines and Power 125, no. 1 (December 27, 2002): 326–31. http://dx.doi.org/10.1115/1.1520155.
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Spontaneous emission spectroscopy has been applied to measure the time-resolved temperature profiles of gaseous fuel flames using high temperature and low oxygen concentration combustion air. Two emission peaks of C2 radical species have been observed at visible wavelengths from propane-air flames. The ratio of these two peaks depends on the flame temperature. The relationship between the ratios of these peaks was correlated with the thermocouple output using a premixed flat flame burner and a multichannel CCD spectrometer. Using this relationship, the flame temperature was determined from the ratio of the C2 peaks. Time-resolved emission intensity profiles of the two C2 bands (two-wavelength image) were observed simultaneously with a high sensitivity video camera fitted with an optical system. The time-resolved temperature profiles were constructed from these intensity profiles by utilizing the previously determined relationship at each pixel. To evaluate fluctuations of flame temperatures, the standard deviation profiles for the temperature profiles have been constructed. This spectroscopic diagnostic technique has been used to measure the profiles of mean flame temperature and temperature fluctuation produced from a concentric diffusion flame using propane as the fuel and high temperature and low oxygen concentration combustion air. In this study, the effect of air-preheat and low oxygen concentration in the combustion air on the subsequent flame temperature and temperature fluctuations has been determined by analyzing the spectra of spontaneous emission from the C2 radicals.
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Bai, Bao Sheng, Ji Chun Zhang, and Bo Lin. "Premixed Gas Flame Burning Velocities of Biomass Gasification Gas." Applied Mechanics and Materials 170-173 (May 2012): 2448–53. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.2448.
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Discuss the flame burning velocities of biomass gasification gases and the methods of increasing them by calculating and programming through MATLAB. The results display that the flame burning velocities of biomass gasification gases are relatively low, and they increase when adding hydrogen, which has a higher flame burning speed. Satisfying effects are achieved under different equivalence ratios, initial temperatures and pressures. Research shows that flame burning velocities improve with the fraction of hydrogen volume increasing. It also suggests that with the rise of equivalence ratio, the velocities increase first, and then decrease, and they reach the highest when equivalence ratio is stoichiometric; an increase in initial temperature accelerates the burning velocities, while the velocities drop by enhancing the pressures.
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Kalman, Joseph, Nick G. Glumac, and Herman Krier. "Experimental Study of Constant Volume Sulfur Dust Explosions." Journal of Combustion 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/817259.
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Dust flames have been studied for decades because of their importance in industrial safety and accident prevention. Recently, dust flames have become a promising candidate to counter biological warfare. Sulfur in particular is one of the elements that is of interest, but sulfur dust flames are not well understood. Flame temperature and flame speed were measured for sulfur flames with particle concentrations of 280 and 560 g/m3and oxygen concentration between 10% and 42% by volume. The flame temperature increased with oxygen concentration from approximately 900 K for the 10% oxygen cases to temperatures exceeding 2000 K under oxygen enriched conditions. The temperature was also observed to increase slightly with particle concentration. The flame speed was observed to increase from approximately 10 cm/s with 10% oxygen to 57 and 81 cm/s with 42% oxygen for the 280 and 560 g/m3cases, respectively. A scaling analysis determined that flames burning in 21% and 42% oxygen are diffusion limited. Finally, it was determined that pressure-time data may likely be used to measure flame speed in constant volume dust explosions.
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Kretschmer, D., and J. Odgers. "The Prediction of Laminar Flame Speeds for Weak Mixtures." Journal of Engineering for Gas Turbines and Power 119, no. 3 (July 1, 1997): 566–72. http://dx.doi.org/10.1115/1.2817022.
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In a recent publication [3], the authors tentatively explored the prediction of propane flame speeds using the calculated burned gas temperature (Tb) and the predicted flame extinction temperature (Ti). A formula was developed that utilized these temperatures together with correction factors for inlet temperature and the oxygen/inert ratio. The present paper has extended this technique so that data from 20 different fuels have been examined over a range of conditions, which include significant variations of both inlet temperature and pressure. Limitations of the technique are discussed, as are possible related applications to other premixed systems such as laminar flames and well-stirred reactors.
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Gupta, A. K., M. J. Lewis, and S. Qi. "Effect of Swirl on Combustion Characteristics in Premixed Flames." Journal of Engineering for Gas Turbines and Power 120, no. 3 (July 1, 1998): 488–94. http://dx.doi.org/10.1115/1.2818171.
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A double concentric premixed swirl burner is used to examine the structure of two different methane-air premixed flames. Direct flame photography together with local temperature data provides an opportunity to investigate the effects of swirl number distribution in each annulus on the global and local flame structure, flame stability and local distribution of thermal signatures. An R-type thermocouple compensated for high-frequency response is used to measure the local distribution of thermal signatures in two different flames, each of which represents a different of thermal signatures in two different flames, each of which represents a different of thermal signatures in two combination of swirl number in the swirl burner. In order to improve the accuracy of the temperature data at high-frequency conditions, information on the thermocouple time constant are also obtained under prevailing conditions of local temperature and velocity by compensating the heat loss from the thermocouple sensor bead. These results assist in quantifying the degree of thermal nonuniformities in the flame signatures as affected by the distribution of swirl and to develop strategies for achievinguniform distribution of temperatures in flames.
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Sturgess, G. J., S. P. Heneghan, M. D. Vangsness, D. R. Ballal, A. L. Lesmerises, and D. Shouse. "Effects of Back-Pressure in a Lean Blowout Research Combustor." Journal of Engineering for Gas Turbines and Power 115, no. 3 (July 1, 1993): 486–98. http://dx.doi.org/10.1115/1.2906735.
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Experimental information is presented on the effects of back-pressure on flame-holding in a gaseous fuel research combustor. Data for wall temperatures and static pressures are used to infer behavior of the major recirculation zones, as a supplement to some velocity and temperature profile measurements using LDV and CARS systems. Observations of flame behavior are also included. Lean blowout is improved by exit blockage, with strongest sensitivity at high combustor loadings. It is concluded that exit blockage exerts its influence through effects on the jet and recirculation zone shear layers.
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Liu, Pengzhong, Fang Niu, Xuewen Wang, Fei Guo, Wei Luo, and Naiji Wang. "Influence of the Inner and Outer Secondary Air Ratios on the Combustion Characteristic and Flame Shape of a Swirl Burner with a Prechamber." Journal of Chemistry 2020 (July 24, 2020): 1–9. http://dx.doi.org/10.1155/2020/4363016.
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The swirl burner with a prechamber was used in a 14 MW pulverized-coal combustion experiment to investigate the influence of inner and secondary air ratios (ISA/OSA) on the combustion characteristic and flame shape in this work. The temperatures and species concentrations in the prechamber were measured via the flue gas analyzer and thermocouples. The flame shape beyond the prechamber outlet was captured by using a high-speed camera. The results showed that the combustion efficiency was increased and low nitrogen combustion was achieved by adopting the swirl burner with a prechamber. The high temperature corrosion and slagging phenomenon did not occur in the prechamber. The influence of ISA/OSA on temperature and species concentration profiles at different areas in the prechamber was different. The flame shape size exhibited an inflection point with increasing ISA/OSA. Considering, comprehensively, the temperature peak, near wall temperature, oxygen-free zone, CO concentration, flame length, flame diameter, and divergence angle, the case of ISA/OSA =1 : 2 had great processing on combustion efficiency and NOx emission. Thus, ISA/OSA = 1 : 2 was selected as the optimized case under experiment conditions.
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White, Scott N., and Nathan S. Boyd. "Effect of Dry Heat, Direct Flame, and Straw Burning on Seed Germination of Weed Species Found in Lowbush Blueberry Fields." Weed Technology 30, no. 1 (March 2016): 263–70. http://dx.doi.org/10.1614/wt-d-15-00103.1.
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Experiments were conducted to determine the effects of dry heat, direct flame, and straw burning on germination of several weed species from lowbush blueberry fields. Dry heat experiments were designed as factorial arrangements of temperature (100, 200, and 300 C in experiment 1 and room temperature, 100, 200, and 300 C in experiment 2) and exposure time (0, 5, 10, 20, 40, and 80 s in experiment 1 and 2, 5, 10, and 20 s in experiment 2) to determine the exposure time required to reduce germination for each temperature. Susceptibility to dry heat varied across species tested, but germination of spreading dogbane, meadow salsify, fireweed, and hair fescue seeds collected from lowbush blueberry fields in Nova Scotia, Canada generally declined exponentially as a function of duration of heat exposure at the temperatures tested. Germination decreased more rapidly at higher temperatures in all species, although the duration of heat exposure required to reduce germination by 50 and 90% varied across temperatures and species. Exposure of seeds to direct flame rapidly reduced germination, with less than 1 s of exposure required to reduce seed germination of witchgrass, spreading dogbane, and meadow salsify by > 90%. Straw burning did not consistently reduce germination of hair fescue or winter bentgrass, indicating that a surface burn occurring above weed seeds may not be consistently effective at reducing seed viability. These results provide important estimates of the temperature and exposure times required to reduce viability of weed seeds in lowbush blueberry fields and suggest that thermal technologies that expose weed seeds to direct flame will be the most consistent in reducing seed viability.
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Bohn, Jan-Peter, Maximilian Blume, Adrian Goanta, and Hartmut Spliethoff. "Flame temperatures and species concentrations in non-stoichiometric oxycoal flames." Fuel 90, no. 10 (October 2011): 3109–17. http://dx.doi.org/10.1016/j.fuel.2011.05.009.
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Torchinskij, A. I., and S. K. Andreev. "DEVELOPMENT OF MODERNIZED GAS BURNER DEVICE OF SERIES GS-M FOR TUNNEL KILNS OF CERAMIC BRICK FIRING." Energy Technologies & Resource Saving, no. 2 (June 20, 2019): 66–69. http://dx.doi.org/10.33070/etars.2.2019.08.
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On the basis of gas-burning devices of the GS series, new devices have been developed, in which gas channels are installed for operation in the mode of maximum or minimum flame length. This allows to increase the stability of the flame at low temperatures of the working space (below the natural gas ignition temperature), which in turn provides an increase in the economic performance of the tunnel kiln firing ceramic bricks. Bibl. 5, Fig. 2.
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de Sá Teles e Lima, Gabriel, Sandro Marden Torres, Kelly Cristiane Gomes, Silvio Romero de Barros, Antônio Farias Leal, and Marçal Rosas Florentino Lima Filho. "Behavior of Sisal Fiber Mat Reinforced Alkaline Activated Metakaolin Matrix under Direct Flame." Key Engineering Materials 600 (March 2014): 433–41. http://dx.doi.org/10.4028/www.scientific.net/kem.600.433.
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Biodegradable containing composites are increasingly present in several industries, mainly because they are renewable but also for their engineering properties. Despite environmentally friendliness has become an issue of paramount importance, the use of natural fibers has some limitations, especially when high temperature exposure is concerned. Geopolymers are known to withstand temperatures as high as 1000°C, preserving significant mechanical properties. This paper aims to explore the potential use of sisal fiber reinforced alkaline activated in high temperature environment. The composites were exposed to direct flame and visual changes and temperature profile were assessed up to 35 minutes. The results shows that material behavior works as an insulation barrier with a c.a. 80% temperature reduction between the direct flame exposed surface to the opposite side. Also, samples with thickness above 5mm maintained their integrity without developing smoke or spreading flame throughout the study time.
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Malek, Asiah A., Frank A. Blazich, Stuart L. Warren, and James E. Shelton. "Initial Growth of Seedlings of Flame Azalea in Response to Day/Night Temperature." Journal of the American Society for Horticultural Science 117, no. 2 (March 1992): 216–19. http://dx.doi.org/10.21273/jashs.117.2.216.
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Seedlings of flame azalea [Rhododendron calendulaceum (Michx.) Torr] were grown for 12 weeks under long-day conditions with days at 18, 22, 26, or 30C for 9 hours in factorial combination with nights at 14, 18, 22, or 26C for 15 hours. Total plant dry weight, top dry weight, leaf area, and dry weights of leaves, stems, and roots were influenced by day and night temperatures and their interactions. Dry matter production was lowest with nights at 14C. Root, leaf, top, and total dry weights were maximized with days at 26C in combination with nights at 18 to 26C. Stem dry weight was maximized with days at 26 to 30C and nights at 22C. Leaf area was largest with days at 18 and 26C in combination with nights at 18 or 26C. Within the optimal, day/night temperature range of 26 C/18-26C for total plant dry weight, there was no evidence that alternating temperatures enhanced growth. Shoot: root ratios (top dry weight: root dry weight) were highest with days at 18 and 30C. Leaf area ratio (total leaf area: total plant dry weight) was highest and specific leaf area (total leaf area: leaf dry weight) was largest when days and nights were at 18C and were lower at higher temperatures. Regardless of day/night temperature, leaf weight ratio (leaf dry weight: total plant dry weight) was higher than either the stem weight ratio (stem dry weight: total plant dry weight) or root weight ratio (root dry weight: total plant dry weight). Net leaf photosynthetic rate increased with day temperatures up to 30C.
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Krupa, R. J., T. F. Culbreth, B. W. Smith, and J. D. Winefordner. "A Flashback-Resistant Burner for Combustion Diagnostics and Analytical Spectrometry." Applied Spectroscopy 40, no. 6 (August 1986): 729–33. http://dx.doi.org/10.1366/0003702864508232.
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A general utility burner for the production of laminar, homogenous diffusion flames, which is immune to flashbacks, is presented. Because the fuel and oxidant mix on the surface of the burner rather than within the spray chamber, the flames cannot flashback. A wide variety of gas mixtures has been investigated, including oxygen, nitrous oxide, and nitric oxide as the oxidants. Any combination of fuel and oxidant can be safely burned to produced a stable, laminar, and audibly quiet flame. Flame temperatures can be varied over a wide range either by changing the fuel-oxidant ratio or by diluting the flame gases with an inert gas. In this manner, the optimum flame temperature and composition can be achieved. These burners are of general use in analytical emission, fluorescence, and photoacoustic spectrometry, as well as combustion diagnostics.
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Mollamahdi, Mahdi, and Seyed Abdolmehdi Hashemi. "The effects of porous wall as a novel flame stabilization method on flame characteristics in a premixed burner for CH4/air mixture by numerical simulation." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 234, no. 2 (June 10, 2019): 211–25. http://dx.doi.org/10.1177/0957650919854906.
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In the present investigation, the effects of inner diameter and length of porous wall on flame stability limits, temperature distribution, methane conversion, and pressure drop in a premixed burner are numerically analyzed. The governing equations are solved by the control volume method, considering Re-Normalization Group k-ɛ for turbulence modeling and eddy dissipation concept for turbulence–chemistry interaction modeling. The simulations are performed for various porous walls with the inner diameter of 30, 40, and 50 mm and the length of 22, 44, and 66 mm. The results demonstrate that the increase in inner diameter of porous wall causes an increase in the lower flame stability limit and a decrease in the upper flame stability limit, gas and solid temperatures, pressure drop, and methane conversion. Also, the maximum solid and gas temperatures in the porous wall and methane conversion are related to the porous wall with 44 mm length. Furthermore, the methane conversion and pressure drop increase with the rise in the equivalence ratio. Finally, it can be said that the change in inner diameter of porous wall is more important than the length of porous wall in the studied phenomena.
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Cole, Wesley J., McKaye H. Dennis, Thomas H. Fletcher, and David R. Weise. "The effects of wind on the flame characteristics of individual leaves." International Journal of Wildland Fire 20, no. 5 (2011): 657. http://dx.doi.org/10.1071/wf10019.
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Individual cuttings from five shrub species were burned over a flat-flame burner under wind conditions of 0.75–2.80 m s–1. Both live and dead cuttings were used. These included single leaves from broadleaf species as well as 3 to 5 cm-long branches from coniferous and small broadleaf species. Flame angles and flame lengths were determined by semi-automated measurements of video images. Additional data, such as times and temperatures corresponding to ignition, maximum flame height and burnout were determined using video and infrared images. Flame angles correlated linearly with wind velocity. They also correlated with the Froude number when either the flame length or flame height was used. Flame angles in individual leaf experiments were generally 50 to 70% less than flame angles derived from Froude number correlations reported in the literature for fuel-bed experiments. Although flame angles increased with fuel mass and moisture content, they were unaffected by fuel species. Flame lengths and flame heights decreased with moisture contents and wind speed but increased with mass. In most cases, samples burned with wind conditions ignited less quickly and at lower temperatures than samples burned without wind. Most samples contained moisture at the time of ignition. Results of this small-scale approach (e.g. using individual cuttings) apply to ignition of shrubs and to flame propagation in shrubs of low bulk density. This research is one of the few attempts to characterise single-leaf and small-branch combustion behaviour in wind and is crucial to the continued development of a semi-empirical shrub combustion model.
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De Lillis, Manuela, Pietro Massimiliano Bianco, and Francesco Loreto. "The influence of leaf water content and isoprenoids on flammability of some Mediterranean woody species." International Journal of Wildland Fire 18, no. 2 (2009): 203. http://dx.doi.org/10.1071/wf07075.
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The impact of water content and isoprenoids on leaf flammability was studied. Field and laboratory experiments were carried out on monoterpene-emitting evergreen broad-leaved species (Quercus ilex, Quercus suber); a needle-leaved species (Pinus halepensis) that emits and stores monoterpenes; an evergreen species (Myrtus communis) that emits isoprene but stores monoterpenes; and a deciduous species (Quercus pubescens) that emits isoprene. Photosynthesis, leaf water content (LWC) and isoprenoid emission were measured. Isoprenoid content was calculated. Temperatures of visible smoke, incandescence and flame appearance were recorded. The LWC significantly correlated with both photosynthesis and isoprenoid emissions. Linear correlation and factorial analysis revealed a positive correlation between temperature of flame appearance and LWC and a negative relationship between temperature of flame appearance and isoprenoid emission. Multiple regression analysis indicated that the temperature of flame appearance was reduced in broadleaved monoterpene-emitting species. In monoterpene emitters, the temperature of flame appearance depended for ~65% on LWC, whereas monoterpene emissions explained ~35% of the dependency. P. halepensis and M. communis, storing high levels of isoprenoids, ignited at high humidity. The results may be explained if isoprenoids indeed facilitate leaf ignition but, being dissolved in water, isoprenoids are also an indicator of a high water content that decreases flammability.
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Zhu, Yong Hong, and Peng Li. "Research on Burning Zone Detection Method Based on Flame Image Recognition for Ceramic Roller Kiln." Applied Mechanics and Materials 602-605 (August 2014): 1761–67. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.1761.
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In the firing process of ceramic products, the sintering conditions vary from firing phase to firing phase. In different firing phases, flame texture changes obviously, so it can be used as a important parameter of burning zone identification for ceramic roller kiln. In this paper, both flame image recognition of simulating artificial-look-fire and multi-point temperature detection technology are used to detect burning zone working conditions of ceramic roller kiln so as to greatly improve detection accuracy. The key data fusion algorithm of PTCR-based point detection temperature and flame image recognition–based detection method of burning zone working condition for ceramic roller kiln are proposed. The temperature measurement experiment system scheme of ceramic roller kiln burning zone is also given. The system can fuse the key process data with flame image characteristics so as to get the comprehensive database used to judge burning zone working conditions and temperatures. In the end, The testing experiment was carried out. The experimental results show that the method proposed above is feasible and effective.
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Daniele, S., J. Mantzaras, P. Jansohn, A. Denisov, and K. Boulouchos. "Flame front/turbulence interaction for syngas fuels in the thin reaction zones regime: turbulent and stretched laminar flame speeds at elevated pressures and temperatures." Journal of Fluid Mechanics 724 (April 29, 2013): 36–68. http://dx.doi.org/10.1017/jfm.2013.141.
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AbstractExperiments were performed in dump-stabilized axisymmetric flames to assess turbulent flame speeds (${S}_{T} $) and mean flamelets speeds (stretched laminar flame speeds, ${S}_{L, k} $). Fuels with significantly different thermodiffusive properties have been investigated, ranging from pure methane to syngas (${\mathrm{H} }_{2} \text{{\ndash}} \mathrm{CO} $ blends) and pure hydrogen, while the pressure was varied from 0.1 to 1.25 MPa. Flame front corrugation was measured with planar laser-induced fluorescence (PLIF) of the OH radical, while turbulence quantities were determined with particle image velocimetry (PIV). Two different analyses based on mass balance were performed on the acquired flame images. The first method assessed absolute values of turbulent flame speeds and the second method, by means of an improved fractal methodology, provided normalized turbulent flame speeds (${S}_{T} / {S}_{L, k} $). Deduced average Markstein numbers exhibited a strong dependence on pressure and hydrogen content of the reactive mixture. It was shown that preferential-diffusive-thermal (PDT) effects acted primarily on enhancing the stretched laminar flame speeds rather than on increasing the flame front corrugations. Interaction between flame front and turbulent eddies measured by the fractal dimension was shown to correlate with the eddy temporal activity.
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Gou, Xiang, Jin Xiang Wu, Lian Sheng Liu, En Yu Wang, Jun Hu Zhou, Jian Zhong Liu, and Ke Fa Cen. "Study on Factors Influencing Pulverized Coal Ignition Time." Advanced Materials Research 614-615 (December 2012): 120–25. http://dx.doi.org/10.4028/www.scientific.net/amr.614-615.120.
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Pulverized coal ignition time is one of crucial parameters in coal ignition process. Based on a general heat absorption equation without chemical reaction, this study was focused on some crucial factors which influence pulverized coal ignition time to theoretically explain the mechanism of heat absorption of pulverized coal. The influences of recirculated flue gas (RFG) temperature, flame temperature, primary air temperature, and coal particle diameter on ignition time were discussed. The importance of radiation heat and convection heat was analyzed. The results show that the higher temperatures of RFG, flame, and primary air can lead to the shorter ignition time respectively. The increase of the coal particle diameter greatly increases the ignition time, and as the diameter goes up, the amount of the ignition delay becomes greater. For high accuracy of ignition time calculation, both radiation heat and convection heat should be taken into account. When flame temperature is very high and RFG temperature is very low, radiation is the dominant factor, otherwise convection is more crucial.
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Alonso, Francisca, Fernando M. Chiamolera, Juan J. Hueso, Mónica González, and Julián Cuevas. "Heat Unit Requirements of “Flame Seedless” Table Grape: A Tool to Predict Its Harvest Period in Protected Cultivation." Plants 10, no. 5 (April 30, 2021): 904. http://dx.doi.org/10.3390/plants10050904.
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Greenhouse cultivation of table grapes is a challenge due to difficulties imposed by their perennial habit and chilling requirements. Despite difficulties, greenhouse cultivation allows ripening long before that in the open field. Nonetheless, for harvesting “Flame Seedless” in the most profitable periods, a cultural practices timetable has to be established. In this context, an estimation of development rate as a function of temperature becomes essential. This work puts forward a procedure to determine “Flame Seedless” threshold temperatures and heat requirements from bud break to ripening. “Flame Seedless” required an average of 1633 growing degree days (GDD) in the open field with a base temperature of 5 °C and an upper threshold temperature of 30 °C. Strikingly, only 1542 GDD were required within the greenhouse. This procedure forecast “Flame Seedless” ripening with an accuracy of three and six days in the open field and greenhouse, improving predictions based on the average number of days between bud break and ripening. The procedure to predict oncoming harvest date was found satisfactory, just four days earlier than the real date. If we used the typical meteorological year instead of the average year, then the prediction was greatly improved since harvest was forecast just one day before its occurrence.
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Herron, J. R., and R. B. Peterson. "Optical Determination of Stagnation Temperature Behind a Gas Sampling Orifice." Journal of Heat Transfer 112, no. 4 (November 1, 1990): 1070–75. http://dx.doi.org/10.1115/1.2910480.
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A technique has been developed for measuring the temperature during a transient combustion event. It combines the features of atomic resonance absorption and direct sampling to produce a relatively simple, intrusive diagnostic technique to obtain time-resolved measurements. In this study, a propagating hydrogen/air flame was used to provide a rapid temperature increase. A small fraction of krypton was added to the reactants and the absorption of resonant radiation at 123.5 nm was recorded downstream of the sampling orifice within a flow tube. Conversion from absorption measurements to temperature values was performed using a computer model of the radiation source and the absorption by the sample. The model of the source was validated by comparing predicted and recorded spectra of hydrogen Lyman-α emissions, while the absorption model for the sampled gas was tested by comparing the temperatures predicted by krypton absorption measurements with those recorded at a range of known temperatures. The direct sampling atomic resonance technique minimizes time-history distortions inherent in other direct sampling techniques, and is capable of tracking local temperatures during the passage of a propagating flame front.
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Lou, Bo, Yonghai Qiu, and Jianhong Xu. "Characteristics of diffusion flames with accelerated motion." Thermal Science 20, no. 6 (2016): 2113–24. http://dx.doi.org/10.2298/tsci150413180l.
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The aim of this work is to present an experiment to study the characteristics of a laminar diffusion flame under acceleration. A Bunsen burner (nozzle diameter 8 mm), using liquefied petroleum gas as its fuel, was ignited under acceleration. The temperature field and the diffusion flame angle of inclination were visualised with the assistance of the visual display technology incorporated in MATLAB?. Results show that the 2-d temperature field under different accelerations matched the variation in average temperatures: they both experience three variations at different time and velocity stages. The greater acceleration has a faster change in average temperature with time, due to the accumulation of combustion heat: the smaller acceleration has a higher average temperature at the same speed. No matter what acceleration was used, in time, the flame angle of inclination increased, but the growth rate decreased until an angle of 90?: this could be explained by analysis of the force distribution within the flame. It is also found that, initially, the growth rate of angle with velocity under the greater acceleration was always smaller than that at lower accelerations; it was also different in flames with uniform velocity fire conditions.
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Silva, R. L. da, L. S. Azevedo, B. V. Sant´Anna, J. R. Patelli Jr, and M. M. Vieira. "THERMAL PERFORMANCE AND FLAME TEMPERATURES ON LPG RADIAL BURNERS IN DOMESTIC COOKERS." Revista de Engenharia Térmica 18, no. 2 (December 16, 2019): 38. http://dx.doi.org/10.5380/reterm.v18i2.70787.
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The objective is to investigate radial burners through experimental tests, looking for its thermal performance behavior. Gas burners in domestic cookers operate on LPG, typically with two different geometries and five thermal power conditions. Usually, those thermal equipment lacks information on its whole operating conditions range for higher energy conversion efficiency and lower fuel consumption; it is not pointed out by the manufacturer or by energy efficiency labeling, what could result in a recommendation for widely effective performance. Appropriate instrumentation was used to carry out the measurements and methodology used as a guideline regulations from INMETRO/CONPET, ABNT - Brazilian Technical Standards Normative, and ANP - National Agency of Petroleum, Natural Gas and Biofuels. Experimental measurements and uncertainties are for the following parameters: fuel mass consumption (kg.s-1), test time elapsed (s), temperature (°C), water mass (kg) and flame temperature by K-type thermocouples (quantitative) and a thermal camera (qualitative). Main conclusions are: a) Operating domestic cookers with handle position selector on middle position (TP3) provides almost the same temperature rise as maximum fuel consumption (TP5), i.e., ΔT in the water container; b) Heat is better transferred (Qgas → Qwater) with the handle position selector fully opened (TP5@B1) and just before fully opening (TP4@B2); c) A non-linear behavior occurs for ηThermal, when moving forward the handle position selector; maximum efficiency occurs at fully open (TP5@B2) and middle opening (TP3@B1); d) Higher values for TPexperimental occurs for B2, in comparison to B1, in whole operational condition ranges; differences are mainly due to geometric parameters (ARB2/ARB1~0.82). In general, B2 has a better geometric design; e) Uncertainty analysis indicate values lower than ±3%, proving to be a suitable methodology for the experimental results in this work; f) Flame temperatures are entirely consistent with both, ηThermal and heat energy delivered, reaching higher temperature values at TP4 for both burners; 751.5°C (B1) and 830.7°C (B2).
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Tao, Mingyuan, Haiwen Ge, Brad VanDerWege, and Peng Zhao. "Fuel wall film effects on premixed flame propagation, quenching and emission." International Journal of Engine Research 21, no. 6 (September 12, 2018): 1055–66. http://dx.doi.org/10.1177/1468087418799565.
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The formation of fuel wall film is a primary cause for efficiency loss and emissions of unburnt hydrocarbons and particulate matters in direct injection engines, especially during cold start. When a premixed flame propagates toward a wall film of liquid fuel, flame structure and propagation could be fundamentally affected by the vaporization flux and the induced thermal and concentration stratifications. It is, therefore, of both fundamental and practical significance to investigate the consequent effect of a wall film on flame quenching. In this work, the interaction of a laminar premixed flame and a fuel wall film has been studied based on one-dimensional direct numerical simulation with detailed chemistry and transport. The mass and energy balance at the wall film interface have been implemented as boundary condition to resolve vaporization. Parametric studies are further conducted with various initial temperatures of 600–800 K, pressures of 7–15 atm, fuel film and wall temperatures of 300–400 K. By comparing the cases with an isothermal dry wall, it is found that the existence of a wall film always promotes flame quenching and causes more emissions. Although quenching distance can vary significantly among conditions, the local equivalence ratio at quenching is largely constant, suggesting the dominant effects of rich mixture and rich flammability limit. By further comparing constant volume and constant pressure conditions, it is observed that pressure and boiling point variation dominate the vaporization boundary layer development and flame quenching, which further suggests that increased pressure during compression stroke in engines can significantly suppress film vaporization. Emissions of unburnt hydrocarbon, soot precursor and low-temperature products before and after flame quenching are also investigated in detail. The results lead to useful insights on the interaction of flame propagation and wall film in well-controlled simplified configurations and shed light on the development of wall film models in three-dimensional in-cylinder combustion simulation.
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Jung, Hyun Chul, Woo Nyon Kim, Chang Ryong Lee, Kwang S. Suh, and Sung-Ryong Kim. "Properties of Flame-Retarding Blends of Polycarbonate and Poly(Acrylonitrile-butadiene-Styrene)." Journal of Polymer Engineering 18, no. 1-2 (March 1, 1998): 115–30. http://dx.doi.org/10.1515/polyeng-1998-1-210.
Full textAbstract:
Abstract Limiting oxygen index (LOI) value, glass transition temperature (Tg), thermal degradation profile, morphology, and tensile strength and elongation at break of the flame-retarding polycarbonate (PC)-poly(acrylonitrile- butadiene-styrene) (ABS) (7/3) blends were studied. The flame retardants used were huntite-hydromagnetite compounds (HHM), triphenyl phosphate (TPP), zinc stannate, and antimony trioxide. The LOI values were increased with the increase of TPP content, but they did not change significantly when the HHM was used as a flame retardant Glass transition temperatures of the flame-retarding PC-ABS (7/3) blends were decreased significantly when TPP was added to the blends. This is mainly due to the plasticizing effect of the TPP on the PC-ABS (7/3) blends. In the flame-retarding PC-ABS (7/3) blends, the LOI value, tensile strength, and elongation at break were measured and found to be 24.6 - 31.6%, 41.4 - 50.3 MPa, and 2.16 - 33.7%, respectively. These LOI values and mechanical properties were achieved when the TPP, zinc stannate, and antimony trioxide were used as flame retardants, and when dodecylbenzenesulfonic acid sodium salt and dimethylsulfone were used as additives into the PC-ABS (7/3) blends.
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Ugarte, Orlando J., and V’yacheslav Akkerman. "Computational Study of Premixed Flame Propagation in Micro-Channels with Nonslip Walls: Effect of Wall Temperature." Fluids 6, no. 1 (January 11, 2021): 36. http://dx.doi.org/10.3390/fluids6010036.
Full textAbstract:
This investigation evaluates the propagation of premixed flames in narrow channels with isothermal walls. The study is based on the numerical solution of the set of fully-compressible, reacting flow equations that includes viscosity, diffusion, thermal conduction and Arrhenius chemical kinetics. Specifically, channels and pipes with one extreme open and one extreme closed are considered such that a flame is sparked at the closed extreme and propagates towards the open one. The isothermal channel walls are kept at multiple constant temperatures in the range from Tw=300 K to 1200 K. The impact of these isothermal walls on the flame dynamics is studied for multiple radii of the channel (R) and for various thermal expansion ratios (Θ), which approximate the thermal behavior of different fuel mixtures in the system. The flame dynamics in isothermal channels is also compared to that with adiabatic walls, which were previously found to produce exponential flame acceleration at the initial stage of the burning process. The results show that the heat losses at the walls prevent strong acceleration and lead to much slower flame propagation in isothermal channels as compared to adiabatic ones. Four distinctive regimes of premixed burning in isothermal channels have been identified in the Θ−Tw−R space: (i) flame extinction; (ii) linear flame acceleration; (iii) steady or near-steady flame propagation; and (iv) flame oscillations. The physical processes in each of these regimes are discussed, and the corresponding regime diagrams are presented.