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Debi Prasad Mishra - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic Flame Stability Diagnosis of Inverse Jet Flame using CH* Chemiluminescence
    Fuel, 2021
    Co-Authors: Vishnu Hariharan, Debi Prasad Mishra
    Abstract:

    Abstract The paper proposes a new methodology to sense dynamic Flame Stability in a Circumferentially Arranged Fuel Port Inverse Jet Flame (IJF) burner. This strategy is devised using the wavelet technique of the CH* signature to overcome the effects of white noise from the spectrum of the chemiluminescent signal. The Flame Stability regimes, namely the stable Flame, onset of liftoff, and main Flame extinction, are identified. The high-speed camera records the transient events during local attachment-detachment of base Flame and main Flame extinction. The higher level of fluctuations during the main Flame extinction is attributed to the Flame-fingering at the proximity of the Flame neck. Besides this, the statistical analysis indicates an increase in higher cumulative frequency count for lower values of CH* intensity at the main Flame extinction. The power spectral analysis denotes high-frequency oscillations during the onset of Flame liftoff. A semi-empirical correlation based on the Coefficient of Variance and Momentum Flux Ratio is proposed for identifying the dynamic Flame Stability. The experimental results show that this technique can be used as a reliable and active control system to avert lean Flame blowout.

  • Static Flame Stability of Circumferentially Arranged Fuel Port Inverse Jet Non-Premixed Flame Burner
    Combustion Science and Technology, 2019
    Co-Authors: Vishnu Hariharan, Debi Prasad Mishra
    Abstract:

    This paper presents experimental studies on Flame appearance and static Flame Stability characteristics of inverse jet Flame (IJF) using a circumferentially arranged fuel port (CAFP) burner by foll...

  • Flame Stability limits and near blowout characteristics of CNG inverse jet Flame
    Fuel, 2015
    Co-Authors: S. Mahesh, Debi Prasad Mishra
    Abstract:

    Abstract This paper reports the Stability limits and near blowout characteristics of unrecessed and recessed compressed natural gas (CNG) inverse jet Flames (IJFs) by varying the central air jet velocity for a constant fuel jet velocity. The experimental results indicate that unrecessed IJF has higher Flame Stability as compared to the recessed case for the same fuel jet velocity. In order to understand the reason for the enhanced Flame Stability in unrecessed IJF as compared to the recessed IJF, the visible appearance of these two inverse jet Flame configurations are examined for understanding the various transient events taking place towards blowout. In the case of unrecessed IJF, initiation of local extinction and reignition phenomena on the Flame surface ushers the onset of blowout. In contrast, this phenomenon is not observed in recessed IJF, rather the Flame gets partially lifted from the burner rim prior to blowout. The enhanced Flame Stability of unrecessed IJF is attributed to the presence of base Flame near the burner rim that acts as a pilot Flame. On the other hand, the absence of base Flame in recessed IJF is the reason for its lower Flame Stability limit as compared to the unrecessed IJF. Based on the nature of blowout events, blowout mechanisms for both unrecessed and recessed IJFs are proposed in the present work.

  • Flame Stability studies in a hydrogen–air premixed Flame annular microcombustor
    International Journal of Hydrogen Energy, 2011
    Co-Authors: Swarup Y. Jejurkar, Debi Prasad Mishra
    Abstract:

    Abstract Flame Stability in an annular heat recirculating microcombustor burning stoichiometric hydrogen–air mixture was explored by means of a rigorous thermal analysis. The analysis is based on computational fluid dynamics model of reacting fluid flow accounting for interactions in flow, species, and conjugate thermal field in fluid and solid. Consideration of thermal diffusion effects in the model was necessary for realistic predictions in all the cases. Flame Stability under different inlet velocity and wall thermal conductivities was studied. Results showed that a stable Flame could stabilize in this combustor in the velocity range of 3–35 m/s. However, the upper Stability limit widened for lower wall thermal conductivity. Low velocity flashback and high velocity blowout bounded the Stability region with respect to inlet velocity for lower thermal conductivity wall material. Lower Flame Stability limit was influenced by thermal design of the microcombustor that prevented Flame extinction and ability of Flame to stabilize at the heated wall even at higher inlet velocity controlled the upper Flame Stability limit. Flame established well within the combustor for the lowest wall thermal conductivity without blowout and approached flashback for the highest conductivity when wall thermal conductivity was varied at constant inlet velocity. Relative importance of axial and radial wall heat conduction in Flame stabilization was explored at the extremes of operating conditions. Both the components played equally important roles in Flame stabilization by influencing heat recirculation and losses within the microcombustor. A suitable combination of structural materials could provide a stable Flame with high surface temperatures in a lightweight system.

Omid Askari - One of the best experts on this subject based on the ideXlab platform.

  • Flame Stability in Inverse Coaxial Injector Using Repetitive Nanosecond Pulsed Plasma
    Journal of Energy Resources Technology-transactions of The Asme, 2020
    Co-Authors: Saeid Zare, Omid Askari
    Abstract:

    Abstract Recently, methane has been investigated as a feasible fuel for propulsion systems. The higher boiling point and higher density of methane, compared with hydrogen, makes its storage tank lighter, cheaper, and smaller to launch. Methane is abundant in the outer solar system and can be harvested on Mars, Titan, Jupiter, and many other planets and therefore, it can be used in reusable rocket engines. However, there are still some technological challenges in the methane engines development path. For example, ignition reliability and Flame Stability are of great importance. These challenges can be addressed by integrating low-temperature plasma (LTP) through repetitive nanosecond pulsed (RNP) discharge to the injector design. This research focuses on air/CH4 jet Flames in a single-element coaxial shear injector coupled with RNP plasma discharge to study the influence of LTP on ignition characteristics and Flame Stability using advanced diagnostic techniques. The experiments have been performed for different fuel composition, jet velocities, discharge voltages, and frequencies at atmospheric conditions. The transient Flame behavior including Flame oscillation is studied using direct photography by CMOS high-speed camera. The effect of plasma discharge location on Flame Stability is also investigated. To demonstrate the effectiveness of RNP discharge on liftoff and blowout/blowoff velocities, the jet velocity at the critical conditions is measured and the enhancements of Flame Stability are then evaluated. The collected experimental data have shown that the RNP discharge can significantly extend the Stability by reducing the liftoff height and increasing the velocity of blowout/blowoff phenomena.

  • Flame Stability in Inverse Coaxial Injector Using Repetitive Nanosecond Pulsed Plasma
    Volume 6: Energy, 2019
    Co-Authors: Saeid Zare, Shrabanti Roy, Omid Askari
    Abstract:

    Abstract There has been recently a growing interest in the use of methane as a strong candidate for both interplanetary and descent/ascent propulsion solutions. The higher boiling point and higher density of methane compared with hydrogen, makes its storage tank lighter, cheaper and smaller to launch. Methane is abundant in the outer solar system and can be harvested on Mars, Titan, Jupiter, and many other planets and therefore, it can be used in reusable rocket engines. However, there are still some technological challenges in methane engines development path. Among those challenges, ignition reliability and Flame Stability are of great importance. These challenges can be addressed by integrating low-temperature plasma (LTP) through repetitive nanosecond pulsed (RNP) discharge to the injector design. This research work focuses on Air/CH4 jet Flames in a single-element coaxial shear injector coupled with RNP plasma discharge to study the influence of LTP on ignition characteristics and Flame Stability using advanced diagnostic techniques. The experiments have been performed for different fuel composition, jet velocities, discharge voltages and frequencies at atmospheric conditions. The transient Flame behavior including Flame oscillation is studied using direct photography by CMOS high-speed camera. The effect of plasma discharge location on Flame Stability is also investigated. To demonstrate the effectiveness of RNP discharge on liftoff and blowout/blowoff velocities, the jet velocity at the critical conditions is measured in terms of discharge frequencies and the enhancement of Flame Stability is then evaluated. The collected experimental data have shown that the RNP discharge can significantly extend the Flame Stability by reducing the liftoff height and increasing the velocity at which blowout/blowoff occurs.

Saeid Zare - One of the best experts on this subject based on the ideXlab platform.

  • Flame Stability in Inverse Coaxial Injector Using Repetitive Nanosecond Pulsed Plasma
    Journal of Energy Resources Technology-transactions of The Asme, 2020
    Co-Authors: Saeid Zare, Omid Askari
    Abstract:

    Abstract Recently, methane has been investigated as a feasible fuel for propulsion systems. The higher boiling point and higher density of methane, compared with hydrogen, makes its storage tank lighter, cheaper, and smaller to launch. Methane is abundant in the outer solar system and can be harvested on Mars, Titan, Jupiter, and many other planets and therefore, it can be used in reusable rocket engines. However, there are still some technological challenges in the methane engines development path. For example, ignition reliability and Flame Stability are of great importance. These challenges can be addressed by integrating low-temperature plasma (LTP) through repetitive nanosecond pulsed (RNP) discharge to the injector design. This research focuses on air/CH4 jet Flames in a single-element coaxial shear injector coupled with RNP plasma discharge to study the influence of LTP on ignition characteristics and Flame Stability using advanced diagnostic techniques. The experiments have been performed for different fuel composition, jet velocities, discharge voltages, and frequencies at atmospheric conditions. The transient Flame behavior including Flame oscillation is studied using direct photography by CMOS high-speed camera. The effect of plasma discharge location on Flame Stability is also investigated. To demonstrate the effectiveness of RNP discharge on liftoff and blowout/blowoff velocities, the jet velocity at the critical conditions is measured and the enhancements of Flame Stability are then evaluated. The collected experimental data have shown that the RNP discharge can significantly extend the Stability by reducing the liftoff height and increasing the velocity of blowout/blowoff phenomena.

  • Flame Stability in Inverse Coaxial Injector Using Repetitive Nanosecond Pulsed Plasma
    Volume 6: Energy, 2019
    Co-Authors: Saeid Zare, Shrabanti Roy, Omid Askari
    Abstract:

    Abstract There has been recently a growing interest in the use of methane as a strong candidate for both interplanetary and descent/ascent propulsion solutions. The higher boiling point and higher density of methane compared with hydrogen, makes its storage tank lighter, cheaper and smaller to launch. Methane is abundant in the outer solar system and can be harvested on Mars, Titan, Jupiter, and many other planets and therefore, it can be used in reusable rocket engines. However, there are still some technological challenges in methane engines development path. Among those challenges, ignition reliability and Flame Stability are of great importance. These challenges can be addressed by integrating low-temperature plasma (LTP) through repetitive nanosecond pulsed (RNP) discharge to the injector design. This research work focuses on Air/CH4 jet Flames in a single-element coaxial shear injector coupled with RNP plasma discharge to study the influence of LTP on ignition characteristics and Flame Stability using advanced diagnostic techniques. The experiments have been performed for different fuel composition, jet velocities, discharge voltages and frequencies at atmospheric conditions. The transient Flame behavior including Flame oscillation is studied using direct photography by CMOS high-speed camera. The effect of plasma discharge location on Flame Stability is also investigated. To demonstrate the effectiveness of RNP discharge on liftoff and blowout/blowoff velocities, the jet velocity at the critical conditions is measured in terms of discharge frequencies and the enhancement of Flame Stability is then evaluated. The collected experimental data have shown that the RNP discharge can significantly extend the Flame Stability by reducing the liftoff height and increasing the velocity at which blowout/blowoff occurs.

Yuegui Zhou - One of the best experts on this subject based on the ideXlab platform.

  • Mechanism analysis on the pulverized coal combustion Flame Stability and NOx emission in a swirl burner with deep air staging
    Journal of the Energy Institute, 2019
    Co-Authors: Chaoyang Zhou, Yongqiang Wang, Qiye Jin, Qijuan Chen, Yuegui Zhou
    Abstract:

    Abstract Low NOx burner and air staged combustion are widely applied to control NOx emission in coal-fired power plants. The gas-solid two-phase flow, pulverized coal combustion and NOx emission characteristics of a single low NOx swirl burner in an existing coal-fired boiler was numerically simulated to analyze the mechanisms of Flame Stability and in-Flame NOx reduction. And the detailed NOx formation and reduction model under fuel rich conditions was employed to optimize NOx emissions for the low NOx burner with air staged combustion of different burner stoichiometric ratios. The results show that the specially-designed swirl burner structures including the pulverized coal concentrator, Flame stabilizing ring and baffle plate create an ignition region of high gas temperature, proper oxygen concentration and high pulverized coal concentration near the annular recirculation zone at the burner outlet for Flame Stability. At the same time, the annular recirculation zone is generated between the primary and secondary air jets to promote the rapid ignition and combustion of pulverized coal particles to consume oxygen, and then a reducing region is formed as fuel-rich environment to contribute to in-Flame NOX reduction. Moreover, the NOx concentration at the outlet of the combustion chamber is greatly reduced when the deep air staged combustion with the burner stoichiometric ratio of 0.75 is adopted, and the CO concentration at the outlet of the combustion chamber can be maintained simultaneously at a low level through the over-fired air injection of high velocity to enhance the mixing of the fresh air with the flue gas, which can provide the optimal solution for lower NOx emission in the existing coal-fired boilers.

  • The Effect of Coal Composition on Ignition and Flame Stability in Coaxial Oxy-Fuel Turbulent Diffusion Flames
    Energy & Fuels, 2013
    Co-Authors: Dadmehr Rezaei, Kerry E. Kelly, Eric G. Eddings, Yuegui Zhou, Ronald J. Pugmire, Mark S. Solum, Jingwei Zhang, Jost O.l. Wendt
    Abstract:

    The purpose of the research reported here is to explore how minor coal composition changes can affect oxy-coal Flame ignition. Whereas previous work focused on the Stability of coaxial turbulent diffusion Flames for a single coal, we explore here how two coals of similar rank, fired under aerodynamically identical input conditions, may show very different Flame Stability characteristics. Since oxy-coal combustion allows oxygen contents in primary and secondary oxidant streams to be varied, Flame Stability characteristics were determined here by effects of partial pressure of oxygen (PO2) in the primary stream (with differing preheat temperatures in the secondary stream) and effects of PO2 in the secondary stream (with zero O2 in the primary stream), on the Flame stand-off distance. The two coals investigated were a Utah Skyline bituminous coal and an Illinois #6 bituminous coal. Flame Stability was quantified by probability density functions (PDF) of the Flame stand-off distance, which were determined usi...

Yong Yan - One of the best experts on this subject based on the ideXlab platform.

  • Quantitative Assessment of Flame Stability Through Image Processing and Spectral Analysis
    IEEE Transactions on Instrumentation and Measurement, 2015
    Co-Authors: Duo Sun, Hao Zhou, Yong Yan, Shi Liu
    Abstract:

    This paper experimentally investigates two generalized methods, i.e., a simple universal index and oscillation frequency, for the quantitative assessment of Flame Stability at fossil-fuel-fired furnaces. The index is proposed to assess the Stability of Flame in terms of its color, geometry, and luminance. It is designed by combining up to seven characteristic parameters extracted from Flame images. The oscillation frequency is derived from the spectral analysis of Flame radiation signals. The measurements involved in these two methods do not require prior knowledge about fuel property, burner type, and other operation conditions. They can therefore be easily applied to Flame Stability assessment without costly and complex adaption. Experiments were carried out on a 9-MW heavy-oil-fired combustion test rig over a wide range of combustion conditions including variations in swirl vane position of the tertiary air, swirl vane position of the secondary air, and the ratio of the primary air to the total air. The impact of these burner parameters on the Stability of heavy oil Flames is investigated by using the index and oscillation frequency proposed. The experimental results obtained demonstrate the effectiveness of the methods and the importance of maintaining a stable Flame for reduced NO x emissions. It is envisaged that such methods can be easily transferred to existing Flame closed-circuit television systems and Flame failure detectors in power stations for Flame Stability monitoring.

  • A simple index based quantitative assessment of Flame Stability
    2013 IEEE International Conference on Imaging Systems and Techniques (IST), 2013
    Co-Authors: Duo Sun, Hao Zhou, Yong Yan
    Abstract:

    This paper proposes a simple universal index for on-line quantitative assessment of Flame Stability. The proposed index has a dynamic range of [0, 1] and is designed by combining the dynamic characteristics of seven parameters extracted from Flame images in HSI color space. It assesses the Flame Stability in terms of color, geometry and luminance. Experiments were carried out on a 9MWth heavy-oil-fired combustion test facility. The impact of the swirl vanes on the Stability of a heavy oil Flame is investigated. The results obtained demonstrate the effectiveness of the proposed approach to quantitative Flame Stability assessment.

  • I2MTC - Flame Stability monitoring through statistical analysis of the medial axis
    2013 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), 2013
    Co-Authors: Tian Qiu, Yong Yan
    Abstract:

    On-line monitoring of Flame Stability is crucial as it is closely related to plant safety, combustion efficiency, and pollutant emissions. This paper presents a new method for the Stability monitoring of a burner Flame using its medial axis. Flame video clips are acquired on a combustion test rig under different combustion conditions. Each frame of the Flame video clips is processed and the medial axis of the Flame is extracted. The processed medial axes are then superimposed for statistical analysis. The test results show that, although the shape of the Flame is randomly fluctuated even under the same combustion condition, some of the statistical shape parameters are relatively stable for the given burner condition. These parameters can be used to indicate the Stability of the Flame.

  • Flame Stability monitoring and characterization through digital imaging and spectral analysis
    Measurement Science and Technology, 2011
    Co-Authors: Duo Sun, Hao Zhou, Yong Yan
    Abstract:

    This paper presents the design, implementation and evaluation of an instrumentation system for the Stability monitoring and characterization of combustion Flames. The system, incorporating optical sensing, image processing and spectral analysis techniques, is designed to monitor a range of Flame characteristic parameters. The Stability of the Flame is assessed through statistical analysis of the Flame parameters obtained. Embedded computer techniques are employed to ensure the compactness and robustness of the system. Experiments were conducted on a gas-fired combustion test rig to evaluate the system. The impact of equivalence ratio on the Stability of the gaseous Flame is investigated. Further trials were carried out on a 9 MWth heavy-oil-fired combustion test facility. The impact of the swirl vane angle of tertiary air on the oil-fired Flames is studied. The results demonstrate the effectiveness of the system for the monitoring and characterization of the Flame Stability.

  • An embedded imaging and signal processing system for Flame Stability monitoring and characterisation
    2010 IEEE International Conference on Imaging Systems and Techniques, 2010
    Co-Authors: Duo Sun, Yong Yan
    Abstract:

    This paper presents the design, implementation and evaluation of an instrumentation system for Flame Stability monitoring and characterisation on industrial furnaces. The system, incorporating digital imaging and spectral analysis techniques, is designed to monitor a range of Flame characteristic parameters. The Stability of the Flame is then assessed through statistical analysis of the Flame parameters obtained. Embedded computer techniques are employed to ensure the system is compact and robust. Experiments were conducted on a laboratory-scale combustion test rig to evaluate the system. The impact of the air-to-fuel ratios on the Stability of a gaseous Flame is investigated. The results demonstrate that the system is capable of monitoring Flame Stability in a statistical way.