Effect of Air Pressure and Gutter Angle on Flame Stability and DeZubay Number for Methane-Air Combustion

2017 ◽  
Vol 34 (1) ◽  
Author(s):  
S. Boopathi ◽  
P. Maran
Keyword(s):  
High Speed ◽  
Pressure Range ◽  
Bluff Body ◽  
Apex Angle ◽  
Flame Stabilization ◽  
Air Pressure ◽  
Flame Stability ◽  
Stability Chart ◽  
Stable Flame

AbstractThe combustion at high speed reactants requires a flame holding characteristics to sustain the flame in the afterburner. The flame holding characteristics of the combustor is carried out by the bluff-body stabilizers. The range of conditions of parameters influencing the flame stabilization is to be identified and the effects on the flame sustainability have to be investigated. DeZubay used the concept of DeZubay number and flame stability envelope to determine the stabilization and blowout range. In the present work, the effect of air pressure and the angle of apex of the V-gutter on flame stabilization and blowout mechanism have been experimentally investigated for six different apex angles and four different air pressure conditions. The value of DeZubay number at each condition has been calculated and verified with DeZubay stability chart for flame stabilization. The results show that stable flame is obtained for the entire pressure range when the apex angle of the V gutter is in 60° and 90°.

scholarly journals Experimental Study of Kerosene Ignition and Flame Stabilization in a Supersonic Combustor

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Yu Meng ◽  
Hongbin Gu ◽  
Xinyu Zhang
Keyword(s):  
Shock Waves ◽  
Combustion Chamber ◽  
High Speed ◽  
Flame Stabilization ◽  
Supersonic Combustion ◽  
Chamber Pressure ◽  
High Speed Photography ◽  
Flame Stability ◽  
Whole Process ◽  
Stable Flame

Abstract A supersonic kerosene ignition and flame stabilization experiments were conducted on a directly connected supersonic combustion test bench. The kerosene fuel was jetted by wall jet at Ma 2.5 airflow. High-speed photography was used to record the CH* emission during ignition, extinguishing and evolution of the flame. Experiments of different equivalence ratios were performed. The processes of ignition, flame holding, and extinguishing were observed as well. The experiment showed the characteristics of ignition core initiation and extension. The time of ignition increased with the increase of equivalence ratios. Flame stability during the process of Ma 2.5 at the entrance of the combustion chamber was also studied. An equilibrium flame pattern of shock wave and flame was discovered in the experiment. In the stable flame state, shock waves near the kerosene jet orifice promote atomization and blending, and the combustion chamber pressure with stable flame makes the shock waves stable near the kerosene jet orifice, thus forming the flame stability model. The whole process and characteristics of kerosene ignition, flame holding and extinguishing are revealed in the experiment.

scholarly journals Experimental investigation of distance between v-gutters on flame stabilization and NOx emissions

2019 ◽  
Vol 23 (5 Part B) ◽  
pp. 2971-2981 ◽  
Author(s):  
Dias Umyshev ◽  
Abay Dostiyarov ◽  
Andrey Kibarin ◽  
Galya Tyutebayeva ◽  
Gaziza Katranova ◽  
...  
Keyword(s):  
Bluff Body ◽  
Flame Stabilization ◽  
Temperature Fields ◽  
Flame Stability ◽  
Bluff Bodies ◽  
Nox Emissions ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Inlet Velocity ◽  
Exhaust Gas Temperature

Blow-off performance and NOx emissions of the propane and air mixture in a rectangular combustion chamber with bluff bodies were investigated experimentally and numerically. The effects of distance between bluff bodies on NOx emissions, the blow-off limit, and exhaust gas temperature were examined. It was observed that NOx emissions are highly dependent on distance between V-gutters. The re-circulation zone behind the bluff body expands in width based on the decrease of distance between V-gutters, and expands in length with the increase of inlet velocity. The temperature fields behind the bluff body show a similar change, the temperature behind the bluff body reaches its highest when the distance between V-gutters reaches 20 mm, meaning it has better flame stability. The blow-off limit is significantly improved with the decrease of distance between V-gutters. The blow-off limit is greatly improved by reducing the distance between the V-gutters. Maximum blow-off limit of 0.11 is reached in the case of 20 mm, compared with 0.16 at 50 mm at a speed of 10 m/s.

The influence of the geometry of V-gutter bluff body on transient vortex shedding

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Luckachan K George ◽  
Raja Sekar K ◽  
Srikrishnan A R ◽  
Kannan R
Keyword(s):  
Vortex Shedding ◽  
High Speed ◽  
Bluff Body ◽  
Vortex Motion ◽  
Flame Stabilization ◽  
Cold Flow ◽  
Transient Simulations ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency ◽  
The Impact

Abstract This study investigates the turbulent flow field downstream of V-gutters using unsteady numerical modelling. An important domain of application of the vortex shedding induced by the V-gutters is the flame stabilization in high speed combustion systems which find extensive applications in aerospace engineering. In view of this, the present study analyses the impact of the V-gutter geometry, as characterized by the included angle, on inducing vortex motion in the wake. Transient simulations are carried out for three values of the semi-span angle, α = 30°, 45° and 60°. Based on the analysis of the saddle point and the vortex shedding frequency, the study shows that an increase in span angle within this range, favours the effectiveness of the method in flame stabilization. Though the simulations are done for cold flow, the dominant mechanism of vortex shedding is adequately addressed in the analysis.

Characterization of ALM Swirl Burner Surface Roughness and its Effects on Flame Stability Using High-Speed Diagnostics

2019 ◽  
Author(s):  
Jon Runyon ◽  
Anthony Giles ◽  
Richard Marsh ◽  
Daniel Pugh ◽  
Burak Goktepe ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Flame Stabilization ◽  
Flame Stability ◽  
Post Processing ◽  
Swirl Burner ◽  
Stability Limits ◽  
Near Wall

Abstract The use of metallic Additive Layer Manufacturing (ALM) is an active area of development for gas turbine components, particularly concerning novel combustor prototypes for micro gas turbines. However, further study is required to understand the influence of this manufacturing technique and subsequent post-processing on the resulting burner component surface roughness and its effect on flame stability. In this study, two Inconel 625 swirl nozzle inserts with identical bulk geometry (swirl number, Sg = 0.8) were constructed via ALM for use in a generic gas turbine swirl burner. Further post-processing by grit blasting of one swirl nozzle insert results in a quantifiable change to the surface roughness characteristics in the burner exit nozzle when compared with the unprocessed ALM swirl nozzle insert or a third nozzle insert which has been manufactured using traditional machining methods. An evaluation of the influence of variable surface roughness effects from these swirl nozzle inserts is therefore performed under preheated isothermal and combustion conditions for premixed methane-air flames at thermal power of 25 kW. High-speed velocimetry at the swirler exit under isothermal air flow conditions gives evidence of the change in near-wall boundary layer thickness and turbulent fluctuations resulting from the change in nozzle surface roughness. Under atmospheric combustion conditions, this influence is further quantified using a combination of dynamic pressure, high-speed OH* chemiluminescence, and exhaust gas emissions measurements to evaluate the flame stabilization mechanisms at the lean blowoff and rich stability limits. Notable differences in flame stabilization are evident as the surface roughness is varied, and changes in rich stability limit were investigated in relation to changes in the near-wall turbulence intensity. Results show the viability of using ALM swirl nozzles in lean premixed gas turbine combustion. Furthermore, precise control of in-process or post-process surface roughness of wetted surfaces can positively influence burner stability limits and must therefore be carefully considered in the ALM burner design process as well as CFD models.

Flame Stability Measurement on Rectangular Slot Meso-Scale Combustor

2016 ◽  
Vol 836 ◽  
pp. 271-276 ◽  
Author(s):  
Satworo Adiwidodo ◽  
I.N.G. Wardana ◽  
Lilis Yuliati ◽  
Mega Nur Sasongko
Keyword(s):  
Heat Loss ◽  
Dead Zone ◽  
Flame Temperature ◽  
Flame Stabilization ◽  
Flame Stability ◽  
Flammability Limit ◽  
Rectangular Slot ◽  
Stability Measurement ◽  
Stable Flame ◽  
Meso Scale

The biggest problem of combustion in the micro-scale or meso-scale combustor is heat loss. Heat loss led to a difficult of stable flame. This research aims to elucidate the flame stabilization and flammability limit of LPG-oxygen premixed flame, temperature distribution and flame visualization. Flame stabilization and flammability limit map are shows in φ - U plane. The result shows that there are six regions in the map that is stable without noise, stable with noise, transition zone, dead zone, pseudo stable, and blow off. Measurement parameters are LPG-oxygen flow velocity at various equivalent ratio and temperature. The flame stabilization and flammability limit map within measurement parameters are discussed.

Dynamics of Non-Premixed Bluff Body-Stabilized Flames in Heated Air Flow

2010 ◽  
Author(s):  
Caleb Cross ◽  
Aimee Fricker ◽  
Dmitriy Shcherbik ◽  
Eugene Lubarsky ◽  
Ben T. Zinn ◽  
...  
Keyword(s):  
Heat Release ◽  
Vortex Shedding ◽  
High Speed ◽  
Bluff Body ◽  
Combustion Process ◽  
Flame Stabilization ◽  
Inlet Temperature ◽  
Fuel Injectors ◽  
Flame Holder ◽  
Process Heat

This paper describes a study of the fundamental flame dynamic processes that control bluff body-stabilized combustion of liquid fuel with low dilatation. Specifically, flame oscillations due to asymmetric vortex shedding downstream of a bluff body (i.e., the Be´nard/von-Ka´rma´n vortex street) were characterized in an effort to identify the fundamental processes that most affect the intensity of these oscillations. For this purpose, the spatial and temporal distributions of the combustion process heat release were characterized over a range of inlet velocities, temperatures, and overall fuel-air ratios in a single flame holder combustion channel with full optical access to the flame. A stream of hot preheated air was supplied to the bluff body using a preburner, and Jet-A fuel was injected across the heated gas stream from discrete fuel injectors integrated within the bluff body. The relative amplitudes, frequencies, and phase of the sinusoidal flame oscillations were characterized by Fourier analysis of high-speed movies of the flame. The amplitudes of the flame oscillations were generally found to increase with global equivalence ratio, reaching a maximum just before rich blowout. Comparison of the flame dynamics to the time-averaged spatial heat release distribution revealed that the intensity of the vortex shedding decreased as a larger fraction of the combustion process heat release occurred in the shear layers surrounding the recirculation zone of the bluff body. Furthermore, a complete transition of the vortex shedding and consequent flame stabilization from asymmetric to symmetric modes was clearly observed when the inlet temperature was reduced from 850°C to 400°C (and hence, significantly increasing the flame dilatation ratio from Tb/Tu ∼ 2.3 to 3.7).

Experimental and Numerical Analysis of Gas Premix Turbulent Flames Stabilized in a Swirl Burner with Central Bluff Body

2020 ◽  
Author(s):  
Fernando Biagioli ◽  
Alessandro Innocenti ◽  
Steffen Terhaar ◽  
Teresa Marchione
Keyword(s):  
Numerical Analysis ◽  
Bluff Body ◽  
Reverse Flow ◽  
Flame Stabilization ◽  
Turbulent Flames ◽  
Experimental Investigations ◽  
Swirl Burner ◽  
Stable Flame ◽  
Sudden Transition ◽  
Flame Behaviour

Abstract Lean premixed gas turbulent flames stabilized in the flow generated by an industrial swirl burner with a central bluff body are experimentally found to behave bi-stable. This bi-stable behaviour, which can be triggered via a small change in some of the controlling parameters, for example the bulk equivalence ratio, consists in a rather sudden transition of the flame from completely lifted to well attached to the bluff body. While several experimental investigations exist on this topic, numerical analysis is limited. The present work is therefore also of numerical nature, with a two-fold scope: a) simulation and validation with experiments of the bi-stable flame behaviour via Computational Fluid Dynamics (CFD) in the form of Large Eddy Simulation (LES) and b) analysis of CFD results to shed light on the flame stabilization properties. LES results, in case of the lifted flame, show that the vortex core is sharply precessing at a given frequency. Phase averaging these results at the frequency of precession clearly indicates a counter-intuitive and unexpected presence of reverse flow going all the way through the flame apex and the bluff body tip. A simple one-dimensional flame stabilization model is applied to explain the bi-stable flame behaviour.

Experimental Investigation on the Influences of Bluff-Body’s Position on Diffusion Flame Structures

2017 ◽  
Author(s):  
Yiheng Tong ◽  
Mao Li ◽  
Jens Klingmann ◽  
Shuang Chen ◽  
Zhongshan Li
Keyword(s):  
Flow Rate ◽  
Diffusion Flame ◽  
High Speed ◽  
Bluff Body ◽  
Recirculation Zone ◽  
Air Flow ◽  
Annular Channel ◽  
Flow Fields ◽  
Flame Stabilization ◽  
Operating Conditions

Effects of the bluff-body’s position on diffusion flame structures and flame instability characteristics were investigated experimentally. A flame regime diagram together with the corresponding flow fields were proposed to evaluate the influences caused by the alternation of bluff-body’s position. The disk shape bluff-body was placed 10 mm downstream or at the same height with the annular channel exit. The bulk velocity of the annular air flow varied from 0 to 8.6m/s while the central jet fuel velocity ranged from 0 to 30m/s. Various flame patterns including the recirculation zone flame, the stable diffusion jet flame, split-flashing flame and lifted flame were observed and recorded with a high speed camera. It is found that the flame has approximately the same patterns with different bluff-body’s positions, except for cases with high air flow rate (Ua > 6.8m/s) and low fuel flow rate (Uj < 5m/s). Under that operating conditions, placing the disk bluff-body 10 mm above the annular channel could better stabilize the flame. High speed Particle Image Velocimetry (PIV) was also used to get deeper insight into the characteristics of the flow fields and flame stabilization. The size and strength of the recirculation zone downstream of the bluff-body altered with the changing of bluff-body’s position and other operating conditions. The recirculation zone, in the burner with the bluff-body placed 10 mm above the air channel exit, was found larger and stronger than that in the other burner geometry. In the reacting case, a recirculation bubble was formed besides the bluff-body’s outer wall which enhanced the flame stabilization. It is also found that the combustion changed the flow fields by enlarging the recirculation bubbles downstream of the bluff-body.

Computational and Experimental Analysis of a Compact Combustor Integrated into a JetCat P90 RXi

2021 ◽  
Author(s):  
Daniel Holobeny ◽  
Brian T. Bohan ◽  
Marc D. Polanka
Keyword(s):  
Bluff Body ◽  
Flame Stabilization ◽  
Inlet Temperature ◽  
Gas Temperature ◽  
Turbine Engine ◽  
Pressure Losses ◽  
Primary Zone ◽  
Sustained Operation ◽  
Mass Flow Rates ◽  
Stable Flame

Abstract Ultra Compact Combustors (UCC) look to reduce the overall combustor length and weight in modern gas turbine engines. Previously, a UCC achieved self-sustained operation at sub-idle speeds in a JetCat P90 RXi turbine engine with a length savings of 33% relative to the stock combustor. However, that combustor experienced flameout as reactions were pushed out of the primary zone before achieving mass flow rates at the engine's idle condition. A new combustor that utilized a bluff body flame stabilization with a larger combustor volume looked to keep reactions in the primary zone within the same axial dimensions. This design was investigated computationally for generalized flow patterns, pressure losses, exit temperature profiles, and reaction distributions at three engine power conditions. The computational results showed the validity of this new Ultra Compact Combustor, with a turbine inlet temperature of 1080 K and a pattern factor of 0.67 at the cruise condition. The combustor was then built and tested in the JetCat P90 RXi with rotating turbomachinery and gaseous propane fuel. The combustor maintained a stable flame from ignition through the 36,000 RPM idle condition. The engine ran self-sustained from 25,000 to 36,000 RPM with an average exit gas temperature of 980 K, which is comparable to the stock engine.

Iterative learning control of air pressure variation inside a high-speed train under the excitation of the tunnel pressure wave with a fixed-morphologic form

2021 ◽  
pp. 095440972110327
Author(s):  
Zhiying He ◽  
Chunjun Chen ◽  
Dongwei Wang ◽  
Chao Deng ◽  
Jia Hu ◽  
...  
Keyword(s):  
Iterative Learning Control ◽  
Pressure Wave ◽  
High Speed ◽  
Learning Control ◽  
Pressure Variation ◽  
Iterative Learning ◽  
Air Pressure ◽  
High Speed Train ◽  
Comfort Index ◽  
Simulation Signal

Based on the characteristics that the tunnel pressure wave has a fixed-morphologic form when the same train passes through the same tunnel, an applicational approach based on the iterative learning control (ILC) is developed, aiming at overcoming the drawbacks of the traditional strategy for controlling the air pressure variation inside a high-speed train carriage. To achieve the goal, the control system is mathematically modelled. Then, the problem is formulated. The task of suppressing the influence of the tunnel pressure wave on the air pressure inside the carriages is shifted as an ILC problem of tracking the comfort index with varying trial length. The algorithm of refreshing the control signal from trial to trial is determined and the process of ILC control is designed. Next, the convergence of the newly-developed applicational ILC algorithm is discussed and the algorithm is simulated by the simulation signal and field-test signal. Results show that the applicational ILC algorithm be more adaptable in handling the control of the air pressure inside carriage under the excitation of varying-amplitude, varying-scale and varying-initial-states tunnel pressure wave. Meanwhile, the matching with tunnel pressure wave makes the applicational ILC algorithm will take both the riding comfort and fresh air into consideration, which upgrades the performances when the high-speed train passing through long tunnels.

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