Download or read book Mechanisms of Flame Stabilisation at Low Lifted Height in a Turbulent Lifted Slot jet Flame written by and published by . This book was released on 2015 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Leading Edge Flame Behavior on Flame Stabilization and Blowout written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this work was to identify the mechanisms that effect stabilization of hydrocarbon jet flames. Methane, nitrogen, and co-flowing air were regulated and directed through a burner that created fully-developed fuel flow with concurrent air. The behavior of the reaction zone at the leading-edge was analyzed from digital images obtained from a camera optimally positioned to capture the movements of the entire flame front. Low Reynolds number flows allowed for the investigation of hysteretic behavior. The hysteresis regime refers to the situation where the jet flame has dual positions favorable to flame stabilization: attached and lifted. Results indicate that flame height in hysteresis is significantly impacted by high velocities of co-flow and that past a critical value a local minimum will be created. Fully turbulent lifted flames were also studied to determine the fluctuations in the height of lifted methane flames in the presence of air co-flow. The partially-premixed flame front of the lifted flame fluctuates in the axial direction, with the fluctuations becoming greater in flames stabilized further downstream. These fluctuations are also observed in flames where blowout is imminent. The height and rate of these fluctuations are studied with respect to average height, flow velocities, and Reynolds number. Additionally, the mechanisms that cause jet-flame blowout, particularly in the presence of air co-flow, are not completely understood. Two types of experiments are described, and the data report that a predictor of blowout is the prior disappearance of the axially-oriented flame branch which is consistently witnessed despite a turbulent flameÃØâ'Ơâ"Øs inherent variable behavior. The conclusions are supported by experiments with nitrogen-diluted flames. A blowout parameter is also calculated for methane flames in co-flow and diluted methane flames that can be used to predict at what flow velocities blowout will occur. This work analyzes flames near the bu.

Download or read book Investigation of Turbulent Lifted Jet Flame Stabilization Using Experimental Methods and Simulations written by Wei Wang and published by . This book was released on 2010 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Simulation of Flame Stabilization of Lifted Turbulent Jet Diffusion Flames written by Ming Chen and published by . This book was released on 2000 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book On Flame Stability In The Hysteresis Regime In Co Flow written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This study documents experiments performed on lifted turbulent diffusion flames in the hysteresis regime with air co-flow. Undiluted methane, ethylene, and propane were used as fuels and two nozzle sizes were used. The results confirm the non-linearity of the lift-off height with nozzle velocity, showing a previously undocumented region where lifted flame height increases as fuel velocity is decreased and that reattachment nozzle velocity varies linearly with co-flow. Using jet relations from Tieszen, the local excess jet velocity was computed and found to vary linearly for flames lifted well above the nozzle. The effect of co-flow was captured using an effective local excess jet velocity, similar to the effective nozzle jet velocity proposed by Montgomery used in conjunction with the results of Khalghatgi. Local excess jet velocities at the reattachment point were also compared for varying co-flow and found to be consistent between co-flow cases. This threshold velocity was found to vary with the inverse of the laminar burning velocity of the fuel squared. Relations for reattachment nozzle velocity and flame lift-off height at reattachment were also determined. The results extend the work of Khalghatgi into the hysteresis regime and complement the work of Gollahalli in determining the mechanisms that support flame stability in the hysteresis regime. Any comprehensive theory for flame stability will have to explain some of the unexpected results seen in the hysteresis regime and incorporate the findings of this study.

Download or read book The Stability of Lifted Turbulent Diffusion and Premixed Flames written by Raymond Kushida and published by . This book was released on 1972* with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Lifted Turbulent Jet Flames written by Jay A. Hammer and published by . This book was released on 1993 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book written by and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Studies on the Leading Edge and Local Extinction in Lifted Jet Diffusion Flames written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Several researchers have examined the concept of flame stability and there has been little agreement regarding the reasons governing this phenomenon. The experiments described within were devised to establish the dominating stabilization mechanism in lifted flames. Specifically, the flame base of lifted methane-jet diffusion flames were examined through the use of various combinations of synchronized laser-based techniques involving particle image velocimetry (PIV), planar laser-induced fluorescence (PLIF), and Rayleigh scattering. Results indicate the presence of a structure termed a flame. Results involving the gradient in the Rayleigh signal across the flame base, in addition to two-shot CH-PLIF interpretations support the leading-edge flame as a primary stabilization mechanism. The extent of premixing upstream of the flame base has been a major source of disagreement in the past. The simultaneous Rayleigh and CH-PLIF images indicate the base of the lifted flame lies in a region that is within the flammability limits of methane burning in air. Furthermore, the average velocity at the stabilization point is 1.18 m/s (as determined from the simultaneous CH-PLIF and PIV investigation); this value is comparable to three times the laminar burning velocity of methane (~ 3S), thereby supporting previous numerical triple flame simulations. Results from the joint two-shot CH-PLIF and PIV technique show that the flame base velocity is independent of the flow conditions when the flame is stationary during the time separation of the CH-PLIF pulses. Specifically, flames with Re flow conditions. Finally, regions of local extinction -- as indicated by openings in the CH profiles -- were examined. Results from four experiments (simultaneous CH-PLIF and PIV, simultaneous CH-PLIF and OH-PLIF, simultaneous CH-PLIF and Rayleigh scattering, and simultaneous two-shot CH-PLIF and PIV) provide complementary information regarding the role of large-scale fuel vortices in initiat.

Download or read book An Experimental Study of Flame Stabilization Mechanisms in Turbulent Non premixed Jet Flames Under Autoignitive Conditions written by Aravind Ramachandran and published by . This book was released on 2019 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Study of Turbulent Jet and Lifted Jet Flame Unsteadiness from a Non linear Dynamics Perspective written by Sina Rafati and published by . This book was released on 2021 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research aims to investigate the nonlinear dynamics of the non-reacting jets and non-premixed lifted jet flames. The goal is to understand better how the flow system dynamics change over time and identify the path toward unwanted conditions such as flashback, extinction, or blowout to limit combustors' dynamical failure. The existence of these undesirable conditions is bound to the fluid's history, meaning that initiated perturbation may persist in the system for time scales comparable to large-scale flow timescales. Hence, the notion is to utilize jet and jet flames as a study test case to work out how the flow evolves dynamically with the hope of understanding how to limit occurrences of the chaotic unwanted condition. Initially, planar particle image velocimetry has been used for the development of the methodologies. I have used planar data to investigate the nonlinear dynamics of non-reacting turbulent jets, with a low-to-moderate Reynolds number using the single-trajectory framework and ensemble framework. I have used Lyapunov exponents to calculate the spectra of scaling indices of the attractor. Then, I used Lagrangian Coherent Structures (LCSs), which are defined as manifolds that are locally Euclidean and invariant, to study the relationship between Lyapunov exponent changes with flow topological features. These LCSs behave as hypersurfaces with maximally repelling or attracting properties. These various methodologies were used to investigate flame-turbulence interaction in lifted jet flames. The Lagrangian framework is shown to be effective at revealing the kinematics associated with flame-turbulence interaction. The LCSs' time history represents how eddy structures interact with the flame and highlight their role in the dynamics of the lifted jet flames. Finally, I have investigated the flame and turbulence interaction using high-speed luminosity imaging and simultaneous three-dimensional particle image velocimetry. The three-dimensional Lagrangian structures provide us a more detailed flow-flame interaction. It is shown that the flow features associated with attracting LCSs can create a barrier attracting the flame that makes the flame move upstream. In contrast, the presence of repelling LCSs near stationary flames breaks the balance between the gas velocity and flame propagation speed, causing the flame to become non-stationary and move downstream. It was also found that the repelling LCSs induce negative curvature on the flame surface whereas pushing the flame toward the products. However, the attracting LCSs induce positive curvature on the flame surface and draws the flame toward the reactants

Download or read book Combined Effects of Dilution and Co flow on the Stability of Lifted Non premixed Gaseous Flames written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This research documents experiments and analysis of turbulent, lifted, non-premixed diffusion flames in co-flow and with dilution with implications for the development and operation of biogas-fueled combustors. Fuels used in this study were methane and ethylene. The diluent used was nitrogen. General trends were observed in the liftoff and reattachment behavior as affected by dilution of the fuel stream. Initial liftoff velocity was observed to decrease linearly with dilution, while initial lift height behavior was bimodal. Reattachment conditions were similar in overall behavior to liftoff conditions. Co-flow effects were not included in liftoff and reattachment studies. Combined effects of dilution and co-flow were also studied. Stabilization height compared to radial stabilization was found to be bimodal, with behavior differing in the potential core region compared with the far-field region. Dilution was found to decrease the radial stabilization distance, and co-flow tended to increase the radial stabilization distance. However, both effects were minor. The major results involve heat release effects. For given stabilization heights, stabilization velocity was found to decrease with dilution faster than laminar burning velocity with dilution. Stabilization height was also found to increase rapidly with dilution beyond a certain diluent concentration. Flames were also found to taper inward and become more cylindrical in shape as dilution increases. Implications for several flame stabilization theories are discussed. Future work for confirming the results of this research are also discussed.

Download or read book Local Flame Stabilization Mechanisms in Turbulent Non premixed Jet Flames in Vitiated Coflow by Particle Image Velocimetry written by Anirudh Reddy Mothe and published by . This book was released on 2016 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Studies on the Leading Edge and Local Extinction in Lifted jet Diffusion Flames written by Kyle Anthony Watson and published by . This book was released on 2002 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: lifted flame, flame stabilization, triple flame, PIV, PLIF, Rayleigh scattering.

Download or read book Th ringer Schulordnung written by Thüringen Kultusministerium and published by . This book was released on 1996 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Conditional Velocity Measurements at the Base of a Turbulent Lifted Jet Flames written by Tzong H. Chen and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stabilization and Blowout of Gaseous and Spray Jet Flames written by Kevin M. Lyons and published by . This book was released on 2001 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: A research program to focus on experimental work in lifted flames (gaseous and spray) has been initiated. In particular, the group is interested in the similarities of spray and gaseous lifted-flame structures, similarities and differences in apparent stabilization phenomena, the role of mixing in each and blowout phenomena. Discussed in this report are the details of experimental findings in gaseous combustion and proposed experiments primarily in spray combustion and how the information and data to be obtained aids in understanding the physics of flame stabilization in general.