The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Deying Chen - One of the best experts on this subject based on the ideXlab platform.
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laser induced spark ignition of coaxial methane oxygen nitrogen Diffusion Flames
Optics Express, 2014Co-Authors: Chang Liu, Rongwei Fan, Deying ChenAbstract:We report the laser induced spark ignition (LSI) of coaxial methane/oxygen/nitrogen Diffusion Flames using the 1064 nm output of a Q-switched Nd:YAG laser. The minimum ignition energy (MIE) and ignition time of the LSI has been determined by measuring the emission signals due to the ignited Flames. The effects of the gas mixture properties, including the overall equivalence ratio (Ф), oxygen concentration and flow rate, and the ignition positions on the two parameters have been investigated systematically. The variation of the MIE and ignition time with the experimental conditions has been compared with the existing results and discussed with a special concentration on the effects of the local Ф.
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Laser induced spark ignition of coaxial methane/oxygen/nitrogen Diffusion Flames
Optics express, 2014Co-Authors: Chang Liu, Rongwei Fan, Deying ChenAbstract:We report the laser induced spark ignition (LSI) of coaxial methane/oxygen/nitrogen Diffusion Flames using the 1064 nm output of a Q-switched Nd:YAG laser. The minimum ignition energy (MIE) and ignition time of the LSI has been determined by measuring the emission signals due to the ignited Flames. The effects of the gas mixture properties, including the overall equivalence ratio (Ф), oxygen concentration and flow rate, and the ignition positions on the two parameters have been investigated systematically. The variation of the MIE and ignition time with the experimental conditions has been compared with the existing results and discussed with a special concentration on the effects of the local Ф.
Omer L Gulder - One of the best experts on this subject based on the ideXlab platform.
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soot formation characteristics of Diffusion Flames of methane doped with toluene and n heptane at elevated pressures
Proceedings of the Combustion Institute, 2017Co-Authors: Adriana Elizabeth Daca, Omer L GulderAbstract:Abstract Laminar co-flow Diffusion Flames of methane doped with n-heptane and toluene were studied experimentally to assess the sooting characteristics of two liquid fuels with increasing pressure. Experiments were conducted in the high-pressure combustion chamber that had been used previously for high-pressure soot formation studies in laminar Diffusion Flames. Either toluene or n-heptane was added to the methane such that 7.5% of the total carbon would be from the liquid fuel so that the results could be used to infer the pressure dependence of sooting propensities of the two liquid fuels. Pressure range was from atmospheric to 8 atm for methane and methane+n-heptane Flames, whereas for methane+toluene mixture it was from atmospheric to 6 atm. A constant carbon mass flow rate of 0.41 mg/s for the three fuels was maintained at all pressures to have tractable measurements. Visible flame heights, as marked by the luminous soot radiation, were constant at all pressures except for methane at 1 atm. Variation of the maximum soot volume fractions, maximum soot yields, and the line-of-sight averaged soot temperatures of the three Flames, pure methane, toluene-doped methane, and n-heptane-doped methane, with pressure were evaluated from soot spectral emission measurements which were collected line-of-sight but converted to radially-resolved values by using an Abel type inversion algorithm assuming axisymmetry of the laminar Diffusion Flames. Maximum soot volume fractions and maximum soot yields in n-heptane- and toluene-doped Flames showed the higher sooting propensity of toluene in comparison to n-heptane at elevated pressures. Sooting propensity, in terms of both maximum soot yield and maximum soot volume fraction, of the methane+toulene flame displayed a relatively weaker dependence on pressure as compared to those of methane and methane+n-heptane mixture.
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comparison of structures of laminar methane oxygen and methane air Diffusion Flames from atmospheric to 60 atm
Combustion and Flame, 2013Co-Authors: Peter H Joo, Marc R J Charest, C P T Groth, Omer L GulderAbstract:Abstract A combined experimental and numerical study was conducted to examine the structure of laminar methane–oxygen Diffusion Flames in comparison with methane–air Flames. Soot measurements made in these Flames indicated that the maximum soot yields of methane–air Flames are consistently higher than methane–oxygen Flames at all pressures. The maximum soot yield of the methane–oxygen Flames reaches a peak near 40 atm and then starts decreasing as the pressure further increased. The maximum soot yield of the methane–air Flames plateaus at about 40 atm and does not change much with further increases in pressure. Methane–oxygen Flames display a distinct two-zone structure which is visible from atmospheric pressure up to 60 atm. The inner zone, similar to hydrocarbon-air Diffusion Flames, has a yellow/orange colour and is surrounded by an outer blue zone. This outer zone was shown to have a stratified structure with a very steep equivalence ratio gradient. The main reactions in this zone were shown to be the oxidation of hydrogen and carbon monoxide produced within the inner zone. The methane–air Diffusion Flames had a thin layer of blue outer zone at atmospheric pressure; however, this zone completely disappeared when the pressure was increased above atmospheric. The presence of the two-zone structure in the methane–oxygen Flames was attributed to the intensified penetration of oxygen into the core flow. The higher diffusivities, steeper oxygen concentration gradients, and enhanced entrainment increase the transport of oxygen to the flame. As such, there is sufficient oxygen present near the base of the flame to support the Diffusion flame in the inner zone of the methane–oxygen Flames. The abundance of oxygen near the centerline, even in the lower portion of the flame, also promotes the oxidation of soot.
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sooting behaviour of n heptane laminar Diffusion Flames at high pressures
Combustion and Flame, 2013Co-Authors: Ahmet E Karatas, Gorngrit Intasopa, Omer L GulderAbstract:Abstract The effect of pressure on sooting behaviour of n-heptane is studied in co-flow n-heptane/air laminar Diffusion Flames at pressures above atmospheric in a high pressure combustion chamber. The fuel is diluted with either nitrogen or helium to keep a non-smoking flame at elevated pressures, and the selected fuel mass flow rate of n-heptane provided Diffusion Flames in which the soot was completely oxidized within the visible flame envelope. The flame stability proved to be a challenge and stable Flames were possible only at certain pressures for a sufficiently long duration to permit measurements. The soot volume fractions and temperatures were measured by spectral soot emission as a function of pressure for nitrogen-diluted n-heptane Flames at 2, 5 and 7 atm. For helium-diluted n-heptane Flames, line of sight soot emission data at 3, 4, and 5 atm are presented at two heights above the burner exit. Comparison of limited nitrogen-diluted n-heptane data to previous measurements of soot yields indicate that soot formation in Diffusion Flames of n-heptane seems to be slightly more sensitive to pressure than that in aliphatic gaseous fuel Diffusion Flames within the pressure range considered in this work.
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soot formation in high pressure laminar Diffusion Flames
Progress in Energy and Combustion Science, 2012Co-Authors: Ahmet E Karatas, Omer L GulderAbstract:Abstract The details of the chemical and physical mechanisms of the soot formation process in combustion remain uncertain due to the highly complex nature of hydrocarbon Flames, and only a few principles are firmly established mostly for atmospheric conditions. In spite of the fact that most combustion devices used for transportation operate at very high pressures (e.g., aircraft gas turbines up to 40 atm, diesel engines exceeding 100 atm), our understanding of soot formation at these pressures is not at a desirable level, and there is a fundamental lack of experimental data and complementary predictive models. The focus of this review is to assess the experimental results available from laminar co-flow Diffusion Flames burning at elevated pressures. First, a brief review of soot formation mechanisms in Diffusion Flames is presented. This is followed by an assessment of soot diagnostics techniques, both intrusive and non-intrusive, most commonly used in soot experiments including the laser induced incandescence. Then the experimental results of soot measurements done at elevated pressures in Diffusion Flames are reviewed and critically assessed. Soot studies in shock tubes and in premixed Flames are not covered. Smoke point fuel mass flow rate is revisited, and shortcomings in recent measurements are pointed. The basic requirements for tractable and comparable measurements as a function of pressure are summarized. Most recent studies at high pressures with aliphatic gaseous fuels show that the soot yield displays a unified behaviour with reduced pressure. The maximum soot yield seems to reach a plateau asymptotically as the pressure exceeds the critical pressure of the fuel. Lack of experimental data on the sensitivity of soot morphology to pressure is emphasized. A short summary of efforts in the literature on the numerical simulation of soot formation in Diffusion Flames at high pressures is the last section of the paper.
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numerical modelling of soot formation and oxidation in laminar coflow non smoking and smoking ethylene Diffusion Flames
Combustion Theory and Modelling, 2003Co-Authors: Fengshan Liu, Hongsheng Guo, Gregory J. Smallwood, Omer L GulderAbstract:A numerical study of soot formation and oxidation in axisymmetric laminar coflow non-smoking and smoking ethylene Diffusion Flames was conducted using detailed gas-phase chemistry and complex therm...
Sang In Keel - One of the best experts on this subject based on the ideXlab platform.
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effects of lewis number and preferential Diffusion on flame characteristics in 80 h2 20 co syngas counterflow Diffusion Flames diluted with he and ar
International Journal of Hydrogen Energy, 2009Co-Authors: Jeong Park, Tran Manh Vu, Sung Hwan Yoon, Sang In KeelAbstract:Numerical study is conducted to grasp flame characteristics in H2/CO syngas counterflow Diffusion Flames diluted with He and Ar. An effective fuel Lewis number, applicable to premixed burning regime and even to moderately stretched Diffusion Flames, is suggested through the comparison among fuel Lewis number, effective Lewis number, and effective fuel Lewis number. Flame characteristics with and without the suppression of the diffusivities of H, H2, and He are compared in order to clarify the important role of preferential Diffusion effects through them. It is found that the scarcity of H and He in reaction zone increases flame temperature whereas that of H2 deteriorates flame temperature. Impact of preferential Diffusion of H, H2, and He in flame characteristics is also addressed to reaction pathways for the purpose of displaying chemical effects.
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Effects of Lewis number and preferential Diffusion on flame characteristics in 80%H2/20%CO syngas counterflow Diffusion Flames diluted with He and Ar
International Journal of Hydrogen Energy, 2009Co-Authors: Jeong Park, Tran Manh Vu, Sung Hwan Yoon, Sang In KeelAbstract:Numerical study is conducted to grasp flame characteristics in H2/CO syngas counterflow Diffusion Flames diluted with He and Ar. An effective fuel Lewis number, applicable to premixed burning regime and even to moderately stretched Diffusion Flames, is suggested through the comparison among fuel Lewis number, effective Lewis number, and effective fuel Lewis number. Flame characteristics with and without the suppression of the diffusivities of H, H2, and He are compared in order to clarify the important role of preferential Diffusion effects through them. It is found that the scarcity of H and He in reaction zone increases flame temperature whereas that of H2 deteriorates flame temperature. Impact of preferential Diffusion of H, H2, and He in flame characteristics is also addressed to reaction pathways for the purpose of displaying chemical effects.
Chang Liu - One of the best experts on this subject based on the ideXlab platform.
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laser induced spark ignition of coaxial methane oxygen nitrogen Diffusion Flames
Optics Express, 2014Co-Authors: Chang Liu, Rongwei Fan, Deying ChenAbstract:We report the laser induced spark ignition (LSI) of coaxial methane/oxygen/nitrogen Diffusion Flames using the 1064 nm output of a Q-switched Nd:YAG laser. The minimum ignition energy (MIE) and ignition time of the LSI has been determined by measuring the emission signals due to the ignited Flames. The effects of the gas mixture properties, including the overall equivalence ratio (Ф), oxygen concentration and flow rate, and the ignition positions on the two parameters have been investigated systematically. The variation of the MIE and ignition time with the experimental conditions has been compared with the existing results and discussed with a special concentration on the effects of the local Ф.
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Laser induced spark ignition of coaxial methane/oxygen/nitrogen Diffusion Flames
Optics express, 2014Co-Authors: Chang Liu, Rongwei Fan, Deying ChenAbstract:We report the laser induced spark ignition (LSI) of coaxial methane/oxygen/nitrogen Diffusion Flames using the 1064 nm output of a Q-switched Nd:YAG laser. The minimum ignition energy (MIE) and ignition time of the LSI has been determined by measuring the emission signals due to the ignited Flames. The effects of the gas mixture properties, including the overall equivalence ratio (Ф), oxygen concentration and flow rate, and the ignition positions on the two parameters have been investigated systematically. The variation of the MIE and ignition time with the experimental conditions has been compared with the existing results and discussed with a special concentration on the effects of the local Ф.
Jeong Park - One of the best experts on this subject based on the ideXlab platform.
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effects of lewis number and preferential Diffusion on flame characteristics in 80 h2 20 co syngas counterflow Diffusion Flames diluted with he and ar
International Journal of Hydrogen Energy, 2009Co-Authors: Jeong Park, Tran Manh Vu, Sung Hwan Yoon, Sang In KeelAbstract:Numerical study is conducted to grasp flame characteristics in H2/CO syngas counterflow Diffusion Flames diluted with He and Ar. An effective fuel Lewis number, applicable to premixed burning regime and even to moderately stretched Diffusion Flames, is suggested through the comparison among fuel Lewis number, effective Lewis number, and effective fuel Lewis number. Flame characteristics with and without the suppression of the diffusivities of H, H2, and He are compared in order to clarify the important role of preferential Diffusion effects through them. It is found that the scarcity of H and He in reaction zone increases flame temperature whereas that of H2 deteriorates flame temperature. Impact of preferential Diffusion of H, H2, and He in flame characteristics is also addressed to reaction pathways for the purpose of displaying chemical effects.
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Effects of Lewis number and preferential Diffusion on flame characteristics in 80%H2/20%CO syngas counterflow Diffusion Flames diluted with He and Ar
International Journal of Hydrogen Energy, 2009Co-Authors: Jeong Park, Tran Manh Vu, Sung Hwan Yoon, Sang In KeelAbstract:Numerical study is conducted to grasp flame characteristics in H2/CO syngas counterflow Diffusion Flames diluted with He and Ar. An effective fuel Lewis number, applicable to premixed burning regime and even to moderately stretched Diffusion Flames, is suggested through the comparison among fuel Lewis number, effective Lewis number, and effective fuel Lewis number. Flame characteristics with and without the suppression of the diffusivities of H, H2, and He are compared in order to clarify the important role of preferential Diffusion effects through them. It is found that the scarcity of H and He in reaction zone increases flame temperature whereas that of H2 deteriorates flame temperature. Impact of preferential Diffusion of H, H2, and He in flame characteristics is also addressed to reaction pathways for the purpose of displaying chemical effects.