The Experts below are selected from a list of 4170 Experts worldwide ranked by ideXlab platform

Zuohua Huang - One of the best experts on this subject based on the ideXlab platform.

  • an experimental comparative study of the stabilization mechanism of biogas hydrogen diffusion Flame
    International Journal of Hydrogen Energy, 2019
    Co-Authors: H S Zhen, Z L Wei, Z B Chen, M W Xiao, Zuohua Huang
    Abstract:

    Abstract This work describes an experimental study of the effect of hydrogen addition on the stabilization characteristics of laminar biogas diffusion Flame. The focus is to identify and compare various factors influencing the blowoff process. Three compositions of biogas, BG40, BG50 and BG60 were considered and the amount of hydrogen added was varied from 5% to 25% of the biogas by volume. With increasing hydrogen addition, the critical flow velocity beyond which the Flame blows off increases faster than the laminar burning velocity (LBV) does, indicating that Flame stabilization is not solely dependent on laminar burning velocity. An exponential relationship is observed between LBV and Flame Propagation Speed. Therefore, both Flame Propagation Speed and LBV, together with other factors, contribute to Flame stabilization. The reason for no stable lift for either biogas or H2-biogas Flame is analyze by Schmidt number calculation, and the results agree with the literature. Also found is that hydrogen added to biogas accelerates the fuel mass diffusion, which may play an important role for stabilization of the nozzle-attached Flame. The CO2-C3H8 and BG60 Flames were compared to exclude the possible dominant role played by insufficient heat release and/or excessive heat loss due to CO2 present in biogas. Tested on varied-size burners show that Flame stabilization depends on burner pore size, where larger diameter allows better Flame stability. The universal equation for predicting blowout/blowoff velocity in the literature was found to be invalid for H2-enriched biogas Flame and a new scaling law was put forwards.

  • Flame Propagation Speed of co2 diluted hydrogen enriched natural gas and air mixtures
    Energy & Fuels, 2009
    Co-Authors: Haiyan Miao, Qi Jiao, Qian Huang, Zuohua Huang
    Abstract:

    Adding hydrogen into natural gas can extend its lean burn capacity, improve engine performance at low load operation, and reduce unburned hydrocarbon emissions at the cost of increased NOx emissions. In this paper, Flame Propagation of premixed CO2 diluted natural gas/hydrogen/air mixtures under various initial pressures was studied by using a constant volume combustion bomb together with high-Speed Schlieren photography. Laminar Flame Speed and laminar burning velocity as well as Markstein length and Flame thickness were obtained for the diluted stoichiometric fuel/air mixtures with different natural gas/hydrogen fractions and diluent ratios under normal, reduced, and elevated pressures. The results showed that both unstretched Flame Speed and unstretched burning velocity are reduced with the increase of diluent ratio as well as initial pressure (except when the hydrogen fraction is 80%). Hydrogen-enriched natural gas with higher hydrogen fraction can tolerate relatively more diluent gas.

  • measurements of laminar burning velocities and markstein lengths of 2 5 dimethylfuran air diluent premixed Flames
    Energy & Fuels, 2009
    Co-Authors: Xuesong Wu, Zuohua Huang, Xiangang Wang, Bin Zheng, Yingjia Zhang
    Abstract:

    Laminar burning velocities and Markstein lengths of 2,5-dimethylfuran (DMF)−air−N2/CO2 premixed mixtures at the atmospheric pressure and initial temperature of 393 K over three different dilution ratios were obtained by using the outwardly propagating spherical Flame and high-Speed schlieren photograph system. Addition of diluent was used to simulate the effects of exhaust gas recirculation on the Flame Propagation. The results show that both unstretched Flame Propagation Speed and laminar burning velocity decrease with the increase of dilution ratio. Markstein length is increased with the increase of dilution ratio, indicating that addition of diluent will improve the stability of the Flame. The dilution effects of CO2 as diluent on the Flame Propagation and the Flame stability are stronger than those of N2 as diluent. For a specific equivalence ratio, the laminar burning velocity shows a linear decreasing trend with the increase of dilution ratio. The ratio of the laminar burning velocities with and wit...

  • measurements of laminar burning velocities and onset of cellular instabilities of methane hydrogen air Flames at elevated pressures and temperatures
    International Journal of Hydrogen Energy, 2009
    Co-Authors: Zuohua Huang, Jianjun Zheng, Haiyan Miao
    Abstract:

    An experimental study on laminar burning velocities and onset of cellular instabilities of the premixed methane–hydrogen–air Flames was conducted in a constant volume combustion vessel at elevated pressures and temperatures. The unstretched laminar burning velocity and Markstein length were obtained over a wide range of hydrogen fractions. Besides, the effects of hydrogen addition, initial pressure and initial temperature on Flame instabilities were analyzed. The results show that the unstretched Flame Propagation Speed and the unstretched laminar burning velocity are increased with the increase of initial temperature and hydrogen fraction, and they are decreased with the increase of initial pressure. Early onset of cellular instability is presented and the critical radius and Markstein length are decreased with the increase of initial pressure, indicating the increase of hydrodynamic instability with the increase of initial pressure. Flame instability is insensitive to initial temperature compared to initial pressure. With the increase of hydrogen fraction, significant decrease in critical radius and Markstein length is presented, indicating the increase in both diffusional-thermal and hydrodynamic instabilities as hydrogen fraction is increased.

  • measurement of laminar burning velocities of dimethyl ether air premixed mixtures with n2 and co2 dilution
    Energy & Fuels, 2009
    Co-Authors: Zhaoyang Chen, Haiyan Miao, Zuohua Huang, Xibin Wang, Deming Jiang
    Abstract:

    Measurements of laminar burning velocities of dimethyl ether−air premixed mixtures with N2 and CO2 dilution were made at room temperature and atmospheric pressure using the spherically expanding Flame and schlieren photography over a wide range of dilution and equivalence ratios. The stretched Flame Propagation Speed, the unstretched Flame Propagation Speed, the unstretched laminar burning velocity, and the Markstein length (Lb) were obtained and analyzed. The results show that the Flame Speeds and the burning velocities decrease monotonously with the increase of the dilution ratio. The maximum value of the unstretched laminar burning velocity is presented at the equivalence ratio of 1.1, regardless of N2 dilution ratios, while it slightly shifts to the rich mixture side with the increase of the CO2 dilution ratio. This phenomenon reveals the different dilution effect on the unstretched laminar burning velocity between the triatomic molecule gas CO2 and the diatomic molecule gas N2. The Markstein length i...

Haiyan Miao - One of the best experts on this subject based on the ideXlab platform.

  • Flame Propagation Speed of co2 diluted hydrogen enriched natural gas and air mixtures
    Energy & Fuels, 2009
    Co-Authors: Haiyan Miao, Qi Jiao, Qian Huang, Zuohua Huang
    Abstract:

    Adding hydrogen into natural gas can extend its lean burn capacity, improve engine performance at low load operation, and reduce unburned hydrocarbon emissions at the cost of increased NOx emissions. In this paper, Flame Propagation of premixed CO2 diluted natural gas/hydrogen/air mixtures under various initial pressures was studied by using a constant volume combustion bomb together with high-Speed Schlieren photography. Laminar Flame Speed and laminar burning velocity as well as Markstein length and Flame thickness were obtained for the diluted stoichiometric fuel/air mixtures with different natural gas/hydrogen fractions and diluent ratios under normal, reduced, and elevated pressures. The results showed that both unstretched Flame Speed and unstretched burning velocity are reduced with the increase of diluent ratio as well as initial pressure (except when the hydrogen fraction is 80%). Hydrogen-enriched natural gas with higher hydrogen fraction can tolerate relatively more diluent gas.

  • measurements of laminar burning velocities and onset of cellular instabilities of methane hydrogen air Flames at elevated pressures and temperatures
    International Journal of Hydrogen Energy, 2009
    Co-Authors: Zuohua Huang, Jianjun Zheng, Haiyan Miao
    Abstract:

    An experimental study on laminar burning velocities and onset of cellular instabilities of the premixed methane–hydrogen–air Flames was conducted in a constant volume combustion vessel at elevated pressures and temperatures. The unstretched laminar burning velocity and Markstein length were obtained over a wide range of hydrogen fractions. Besides, the effects of hydrogen addition, initial pressure and initial temperature on Flame instabilities were analyzed. The results show that the unstretched Flame Propagation Speed and the unstretched laminar burning velocity are increased with the increase of initial temperature and hydrogen fraction, and they are decreased with the increase of initial pressure. Early onset of cellular instability is presented and the critical radius and Markstein length are decreased with the increase of initial pressure, indicating the increase of hydrodynamic instability with the increase of initial pressure. Flame instability is insensitive to initial temperature compared to initial pressure. With the increase of hydrogen fraction, significant decrease in critical radius and Markstein length is presented, indicating the increase in both diffusional-thermal and hydrodynamic instabilities as hydrogen fraction is increased.

  • measurement of laminar burning velocities of dimethyl ether air premixed mixtures with n2 and co2 dilution
    Energy & Fuels, 2009
    Co-Authors: Zhaoyang Chen, Haiyan Miao, Zuohua Huang, Xibin Wang, Deming Jiang
    Abstract:

    Measurements of laminar burning velocities of dimethyl ether−air premixed mixtures with N2 and CO2 dilution were made at room temperature and atmospheric pressure using the spherically expanding Flame and schlieren photography over a wide range of dilution and equivalence ratios. The stretched Flame Propagation Speed, the unstretched Flame Propagation Speed, the unstretched laminar burning velocity, and the Markstein length (Lb) were obtained and analyzed. The results show that the Flame Speeds and the burning velocities decrease monotonously with the increase of the dilution ratio. The maximum value of the unstretched laminar burning velocity is presented at the equivalence ratio of 1.1, regardless of N2 dilution ratios, while it slightly shifts to the rich mixture side with the increase of the CO2 dilution ratio. This phenomenon reveals the different dilution effect on the unstretched laminar burning velocity between the triatomic molecule gas CO2 and the diatomic molecule gas N2. The Markstein length i...

  • measurements of laminar burning velocities and markstein lengths of propane hydrogen air mixtures at elevated pressures and temperatures
    International Journal of Hydrogen Energy, 2008
    Co-Authors: Chenglong Tang, Zuohua Huang, Chun Jin, Jinhua Wang, Xibin Wang, Haiyan Miao
    Abstract:

    Abstract Experimental study on the laminar burning velocities and the onset of cellular instabilities of propane–hydrogen–air mixtures with spherically expanding Flames was conducted at elevated pressures and temperatures and different hydrogen fractions at the equivalence ratio of 0.8 and 1.2. The results show that the unstretched Flame Propagation Speed and the unstretched laminar burning velocity increase with the increase of hydrogen fraction and initial temperature, and they decrease with the increase of initial pressure. An earlier onset of cellular instability and the decrease in the critical radius and the Markstein length are presented with the increase of initial pressure, indicating that the hydrodynamic instability is enhanced with the increase of initial pressure. At the equivalence ratio of 0.8, where the propane–air mixture is thermal-diffusionally stable and the hydrogen–air mixture is thermal-diffusionally unstable, the critical radius and the Markstein length decrease significantly with the increase of hydrogen fraction, indicating that hydrogen addition will increase the diffusional-thermal and the hydrodynamic instability. At equivalence ratio of 1.2, where the propane–air mixture and hydrogen–air mixture are both thermal-diffusionally neutral, a moderate decrease in the critical radius and the Markstein length is presented. This indicates the increase of hydrodynamic instability as hydrogen is added.

Pavel Bulat - One of the best experts on this subject based on the ideXlab platform.

  • ignition and combustion of air fuel mixture in a long tube induced by microwave subcritical streamer discharge
    Acta Astronautica, 2019
    Co-Authors: Mikhail Bulat, Pavel Bulat, Petr Denissenko, Igor Esakov, L P Grachev, K N Volkov, Igor Volobuev
    Abstract:

    Abstract There have been consistent efforts in developing more efficient combustion for propulsion systems. Ignition and combustion control using cold and non-thermal plasma in microwave discharges have become a major topic of interest. In this study, a microwave subcritical streamer discharge is used to initiate ignition and combustion of premixed air/fuel mixture in a long cylindrical tube. The streamer discharge is arising on the internal surface of the dielectric tube using a passive vibrator in a single pulse regime at atmospheric pressure and temperature. The Propagation Speed of the combustion front in the quartz cylindrical tube filled by the air/propane mixture is analyzed experimentally and numerically. The streamer discharge creating a multitude of ignition points provides practically instantaneous ignition of the mixture in the entire volume. The Speed of streamer induced combustion front has been shown to be higher compared to that initiated by a spark. Increasing the length of streamer discharge leads to increasing the Flame Propagation Speed. The combustion efficiency has also been shown to be higher when using the microwave streamer ignition.

  • ignition of premixed air fuel mixtures by microwave streamer discharge
    Combustion and Flame, 2019
    Co-Authors: Petr Denissenko, Mikhail Bulat, Pavel Bulat, Igor Esakov, Igor Volobuev, L P Grachev, K N Volkov, Vladimir Upyrev
    Abstract:

    Abstract A variety of methods exists for fast and efficient combustion of air-fuel mixtures. In this study, a microwave subcritical streamer discharge is used to ignite propane-air mixtures at atmospheric pressure. The streamer is initiated at the inner surface of a dielectric tube with the help of a passive half-wave vibrator. By creating a network of ignition lines, the streamer discharge forms the network of burning channels with large total surface area. This leads to the apparent Speed of combustion Propagation along the cylinder in excess of 100 m/s, which is more than 200 times the laminar Flame Propagation Speed. The axial Propagation of the combustion front in a cylindrical tube filled with the air/propane mixture is investigated by high Speed video recording in visible light. A simple model is presented to explain observed results.

  • numerical simulation of ignition of premixed air fuel mixtures by microwave streamer discharge
    IEEE Transactions on Plasma Science, 2019
    Co-Authors: Mikhail Bulat, Pavel Bulat, Petr Denissenko, Igor Esakov, L P Grachev, K N Volkov, Igor Volobuev
    Abstract:

    A subcritical microwave streamer discharge is used to initiate ignition of premixed air/fuel mixture. The streamer is arising on the internal surface of the dielectric tube using a passive vibrator in a single-pulse regime at atmospheric pressure and temperature. The Propagation Speed of the combustion front in the quartz cylindrical tube filled by the air/propane mixture is analyzed numerically. The performed studies showed that the streamer discharge, which creates a multitude of ignition points, provides practically instantaneous ignition of the mixture in the entire volume of the tube, where the streamers reach. The results of numerical simulation are compared with the experimental data. Increasing the length of streamer discharge leads to increasing the Flame Propagation Speed.

  • Numerical Simulation of Ignition of Premixed Air/Fuel Mixtures by Microwave Streamer Discharge
    IEEE Transactions on Plasma Science, 2019
    Co-Authors: Mikhail Bulat, Pavel Bulat, Petr Denissenko, Igor Esakov, Lev Grachev, Konstantin Volkov, Igor Volobuev
    Abstract:

    A subcritical microwave streamer discharge is used to initiate ignition of premixed air/fuel mixture. The streamer is arising on the internal surface of the dielectric tube using a passive vibrator in a single-pulse regime at atmospheric pressure and temperature. The Propagation Speed of the combustion front in the quartz cylindrical tube filled by the air/propane mixture is analyzed numerically. The performed studies showed that the streamer discharge, which creates a multitude of ignition points, provides practically instantaneous ignition of the mixture in the entire volume of the tube, where the streamers reach. The results of numerical simulation are compared with the experimental data. Increasing the length of streamer discharge leads to increasing the Flame Propagation Speed.

Mikhail Bulat - One of the best experts on this subject based on the ideXlab platform.

  • ignition and combustion of air fuel mixture in a long tube induced by microwave subcritical streamer discharge
    Acta Astronautica, 2019
    Co-Authors: Mikhail Bulat, Pavel Bulat, Petr Denissenko, Igor Esakov, L P Grachev, K N Volkov, Igor Volobuev
    Abstract:

    Abstract There have been consistent efforts in developing more efficient combustion for propulsion systems. Ignition and combustion control using cold and non-thermal plasma in microwave discharges have become a major topic of interest. In this study, a microwave subcritical streamer discharge is used to initiate ignition and combustion of premixed air/fuel mixture in a long cylindrical tube. The streamer discharge is arising on the internal surface of the dielectric tube using a passive vibrator in a single pulse regime at atmospheric pressure and temperature. The Propagation Speed of the combustion front in the quartz cylindrical tube filled by the air/propane mixture is analyzed experimentally and numerically. The streamer discharge creating a multitude of ignition points provides practically instantaneous ignition of the mixture in the entire volume. The Speed of streamer induced combustion front has been shown to be higher compared to that initiated by a spark. Increasing the length of streamer discharge leads to increasing the Flame Propagation Speed. The combustion efficiency has also been shown to be higher when using the microwave streamer ignition.

  • ignition of premixed air fuel mixtures by microwave streamer discharge
    Combustion and Flame, 2019
    Co-Authors: Petr Denissenko, Mikhail Bulat, Pavel Bulat, Igor Esakov, Igor Volobuev, L P Grachev, K N Volkov, Vladimir Upyrev
    Abstract:

    Abstract A variety of methods exists for fast and efficient combustion of air-fuel mixtures. In this study, a microwave subcritical streamer discharge is used to ignite propane-air mixtures at atmospheric pressure. The streamer is initiated at the inner surface of a dielectric tube with the help of a passive half-wave vibrator. By creating a network of ignition lines, the streamer discharge forms the network of burning channels with large total surface area. This leads to the apparent Speed of combustion Propagation along the cylinder in excess of 100 m/s, which is more than 200 times the laminar Flame Propagation Speed. The axial Propagation of the combustion front in a cylindrical tube filled with the air/propane mixture is investigated by high Speed video recording in visible light. A simple model is presented to explain observed results.

  • numerical simulation of ignition of premixed air fuel mixtures by microwave streamer discharge
    IEEE Transactions on Plasma Science, 2019
    Co-Authors: Mikhail Bulat, Pavel Bulat, Petr Denissenko, Igor Esakov, L P Grachev, K N Volkov, Igor Volobuev
    Abstract:

    A subcritical microwave streamer discharge is used to initiate ignition of premixed air/fuel mixture. The streamer is arising on the internal surface of the dielectric tube using a passive vibrator in a single-pulse regime at atmospheric pressure and temperature. The Propagation Speed of the combustion front in the quartz cylindrical tube filled by the air/propane mixture is analyzed numerically. The performed studies showed that the streamer discharge, which creates a multitude of ignition points, provides practically instantaneous ignition of the mixture in the entire volume of the tube, where the streamers reach. The results of numerical simulation are compared with the experimental data. Increasing the length of streamer discharge leads to increasing the Flame Propagation Speed.

  • Numerical Simulation of Ignition of Premixed Air/Fuel Mixtures by Microwave Streamer Discharge
    IEEE Transactions on Plasma Science, 2019
    Co-Authors: Mikhail Bulat, Pavel Bulat, Petr Denissenko, Igor Esakov, Lev Grachev, Konstantin Volkov, Igor Volobuev
    Abstract:

    A subcritical microwave streamer discharge is used to initiate ignition of premixed air/fuel mixture. The streamer is arising on the internal surface of the dielectric tube using a passive vibrator in a single-pulse regime at atmospheric pressure and temperature. The Propagation Speed of the combustion front in the quartz cylindrical tube filled by the air/propane mixture is analyzed numerically. The performed studies showed that the streamer discharge, which creates a multitude of ignition points, provides practically instantaneous ignition of the mixture in the entire volume of the tube, where the streamers reach. The results of numerical simulation are compared with the experimental data. Increasing the length of streamer discharge leads to increasing the Flame Propagation Speed.

Yangfan Cheng - One of the best experts on this subject based on the ideXlab platform.

  • combustion behaviors and explosibility of suspended metal hydride tih2 dust
    International Journal of Hydrogen Energy, 2020
    Co-Authors: Yangfan Cheng, Rong Liu, Yule Yao, Wentao Wang, Chimin Shu
    Abstract:

    Abstract In the production and storage processes of metal hydride material of TiH2, there are at least three kinds of explosion hazards, for example, TiH2 dust explosion, H2 explosion and hybrid H2/TiH2 dust explosion. In this study, combustion behaviors of TiH2 dust cloud under isobaric and isochoric conditions were studied using a visual dust combustion facility and a standard 20-L spherical explosion vessel bomb, respectively, and Ti dust and hybrid H2/Ti dust were used as the reference materials. Experimental results showed that at equal dust concentrations, the Flame Propagation Speed Sf, burning velocity SL, maximum pressure rise Pex and maximum rate of pressure rise (dP/dt)ex of TiH2 dust were all higher than those of Ti dust, while much smaller than those of hybrid H2/Ti dust except the maximum pressure rise Pex. The hydrogen state and content were the primary factors for the combustion differences of dust explosions. The values of explosion index Kst showed that the explosion risks of these samples increased as follows: Ti ˂ TiH2 ˂ hybrid H2/Ti dust.

  • Flame Propagation behaviors and influential factors of tih2 dust explosions at a constant pressure
    International Journal of Hydrogen Energy, 2018
    Co-Authors: Yangfan Cheng, Xiangrui Meng, Quan Wang, Zhaowu Shen, Shixiang Song
    Abstract:

    Abstract The Flame Propagation through TiH2 dust cloud at near constant pressure condition is studied in a series of experiments using an apparatus with transparent latex balloons. The influential factors for the combustion performance of TiH2 dust cloud, including dust concentration, particle size, scale of isobaric space and oxygen content are investigated. Results show that the burning velocity increases with dust concentration in the fuel-lean mixtures, and then plateaus after crossing the stoichiometric condition, while the trend of Flame Speed changing with dust concentration varies for different mean particle sizes (D50) of 48 and 106 μm. The Flame Propagation Speed of dust cloud is positively correlated to the isobaric space scale and oxygen content. The burning mechanism of TiH2 dust is thought to be mainly controlled by diffusion regime, the appearance of hydrogen gas accelerates the combustion rate of TiH2 particles and also makes the TiH2 dust changed from a discrete media to a continuum, which may account for the phenomenon that the Flame Speed in dust cloud of TiH2 is larger than that of Ti at the same concentration no matter in air or oxygen atmosphere.