Flow Field, Spray Distribution and Pilot Flame Stabilization in a Centrally Staged Combustor

2020 ◽  
Author(s):  
Bo Wang ◽  
Guangming Ren ◽  
Xiaohua Gan ◽  
Yuzhen Lin
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Stability Boundary ◽  
Critical Time ◽  
Flame Stabilization ◽  
Cycle Duration ◽  
High Speed Camera ◽  
Double Root ◽  
Fuel Distribution ◽  
Spray Distribution

Abstract Centrally staged lean premixed prevaporized low emission combustor has achieved great commercial success in the past decade. Pilot flame characteristics is with key importance to centrally staged combustor, which is considered not entirely up to the design of pilot stage, but also influenced by the flow field and fuel distribution of the combustor. The flow field and fuel distribution behaviors in centrally staged combustor are not very clear since the role of LRZ is unknown, as well as the pilot flame stabilization mechanism. The goal of this paper is to study the flow field, spray distribution and pilot flame stabilization in centrally staged combustor. This paper designs a comparison scheme of the dome lip for study. Particle image velocimetry, Planar Mie scattering measurements and high-speed camera experiments are conducted to get an in depth understanding on the flow field, spray distribution characteristics and pilot flame stabilization in a centrally staged combustor. The flow field with a 3.0 mm lip incline is quite different. Two PRZs forms, one connected with the LRZ and the other at the outlet of pilot stage. Pilot flow no longer joins to the main flow but flows alone in the center. It seems like it is the decoupling pilot stage air cutting PRZ into two PRZs. The pilot spray has a conical boundary and it is probably formed by the high velocity main air flow. A considerable number of fuel droplets are involved in LRZ with the lip incline. Two shapes of pilot flame are observed, the V-shaped flame and double root flame. High-speed camera has captured the flame stabilization process close to LBO. As for the V-shaped pilot flame, the central flame root performs an extinction/relight cycle close to LBO. The cycle duration time is much longer than the critical time of swirl cup methane flame previously reported. As for the double root pilot flame, the central flame root is lighted before the lip flame root and it is the central flame that plays the leading role in stabilizing the whole flame. The lip flame root can weaken the quench effect of main air and broaden the flame stability boundary. A relatively large lip height is recommended for the consideration of the LBO performance.

Influence of Main Swirler Vane Angle on the Ignition Performance of TeLESS-II Combustor

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Bo Wang ◽  
Chi Zhang ◽  
Yuzhen Lin ◽  
Xin Hui ◽  
Jibao Li
Keyword(s):  
High Speed ◽  
Inlet Temperature ◽  
Main Stage ◽  
Ignition Process ◽  
High Speed Camera ◽  
Fuel Distribution ◽  
Fuel Droplets ◽  
Planar Laser ◽  
Cfd Method ◽  
Vane Angle

In order to balance the low emission and wide stabilization for lean premixed prevaporized (LPP) combustion, the centrally staged layout is preferred in advanced aero-engine combustors. However, compared with the conventional combustor, it is more difficult for the centrally staged combustor to light up as the main stage air layer will prevent the pilot fuel droplets arriving at igniter tip. The goal of the present paper is to study the effect of the main stage air on the ignition of the centrally staged combustor. Two cases of the main swirler vane angle of the TeLESS-II combustor, 20 deg and 30 deg are researched. The ignition results at room inlet temperature and pressure show that the ignition performance of the 30 deg vane angle case is better than that of the 20 deg vane angle case. High-speed camera, planar laser induced fluorescence (PLIF), and computational fluids dynamics (CFD) are used to better understand the ignition results. The high-speed camera has recorded the ignition process, indicated that an initial kernel forms just adjacent the liner wall after the igniter is turned on, the kernel propagates along the radial direction to the combustor center and begins to grow into a big flame, and then it spreads to the exit of the pilot stage, and eventually stabilizes the flame. CFD of the cold flow field coupled with spray field is conducted. A verification of the CFD method has been applied with PLIF measurement, and the simulation results can qualitatively represent the experimental data in terms of fuel distribution. The CFD results show that the radial dimensions of the primary recirculation zone of the two cases are very similar, and the dominant cause of the different ignition results is the vapor distribution of the fuel. The concentration of kerosene vapor of the 30 deg vane angle case is much larger than that of the 20 deg vane angle case close to the igniter tip and along the propagation route of the kernel, therefore, the 30 deg vane angle case has a better ignition performance. For the consideration of the ignition performance, a larger main swirler vane angle of 30 deg is suggested for the better fuel distribution when designing a centrally staged combustor.

scholarly journals Characterization of the Acoustic Interactions in a Two-Staged Multi-Injection Combustor Fed With Liquid Fuel

2012 ◽  
Author(s):  
T. Providakis ◽  
L. Zimmer ◽  
P. Scouflaire ◽  
S. Ducruix
Keyword(s):  
Velocity Field ◽  
Acoustic Field ◽  
Gas Turbines ◽  
High Speed ◽  
Fuel Injection ◽  
Flame Stabilization ◽  
Pollutant Emissions ◽  
Mean Values ◽  
Fuel Distribution ◽  
Droplet Behavior

Burners operating in lean premixed prevaporized (LPP) regimes are considered as good candidates to reduce pollutant emissions from gas turbines. Lean combustion regimes result in lower burnt gas temperatures and therefore a reduction on the NOx emissions, one of the main pollutant species. However, these burners usually show strong flame dynamics, making them prone to various stabilization problems (combustion instabilities, flashback, flame extinction). To face this issue, multi-injection staged combustion can be envisaged. Staging procedures enable fuel distribution control, while multipoint injections can lead to a fast and efficient mixing. A laboratory-scale staged multipoint combustor is developed in the present study, in the framework of LPP combustion, with an injection device close to the industrial one. Using a staging procedure between the primary pilot stage and the secondary multipoint one, droplet and velocity field distributions can be varied in the spray that is formed at the entrance of the combustion chamber. The resulting spray and the flame are characterized using OH-Planar Laser Induced Fluorescence, High Speed Particle Image Velocimetry and Phase Doppler Anemometry measurements. Three staging values, corresponding to three different flame stabilization processes, are analyzed, while power is kept constant. It is shown that mean values are strongly influenced by the fuel distribution and the flame position. Using adequate post-processing, the interaction between the acoustic field and the droplet behavior is characterized. Spectral analysis reveals a strong acoustic-flame coupling leading to a low frequency oscillation of both the velocity field and the spray droplet distribution. In addition, acoustic measurements in the feeding line show that a strong oscillation of the acoustic field leading to a change in fuel injection, and hence droplet behavior.

scholarly journals Characterization of the Acoustic Interactions in a Two-Stage Multi-Injection Combustor Fed With Liquid Fuel

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Theodore Providakis ◽  
Laurent Zimmer ◽  
Philippe Scouflaire ◽  
Sébastien Ducruix
Keyword(s):  
Velocity Field ◽  
Acoustic Field ◽  
Gas Turbines ◽  
High Speed ◽  
Fuel Injection ◽  
Flame Stabilization ◽  
Pollutant Emissions ◽  
Mean Values ◽  
Fuel Distribution ◽  
Droplet Behavior

Burners operating in lean premixed prevaporized (LPP) regimes are considered as good candidates to reduce pollutant emissions from gas turbines. Lean combustion regimes result in lower burnt gas temperatures and therefore a reduction on the NOx emissions, one of the main pollutant species. However, these burners usually show strong flame dynamics, making them prone to various stabilization problems (combustion instabilities, flashback, flame extinction). To face this issue, multi-injection staged combustion can be envisaged. Staging procedures enable fuel distribution control, while multipoint injections can lead to a fast and efficient mixing. A laboratory-scale staged multipoint combustor is developed in the present study, in the framework of LPP combustion, with an injection device close to the industrial one. Using a staging procedure between the primary pilot stage and the secondary multipoint one, droplet and velocity field distributions can be varied in the spray that is formed at the entrance of the combustion chamber. The resulting spray and flame are characterized using OH-planar laser induced fluorescence, high speed particle image velocimetry, and phase Doppler anemometry measurements. Three staging values, corresponding to three different flame stabilization processes, are analyzed, while power is kept constant. It is shown that mean values are strongly influenced by the fuel distribution and the flame position. Using adequate postprocessing, the interaction between the acoustic field and the droplet behavior is characterized. Spectral analysis reveals a strong acoustic-flame coupling leading to a low frequency oscillation of both the velocity field and the spray droplet distribution. In addition, acoustic measurements in the feeding line show that a strong oscillation of the acoustic field leads to a change in fuel injection, and hence droplet behavior.

Air Flow Field and Fiber Motion in a Swirl Die Melt-Blowing Process

2013 ◽  
Vol 690-693 ◽  
pp. 2861-2865
Author(s):  
Sheng Xie ◽  
Yuan Sheng Zheng ◽  
Yong Chun Zeng
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Air Flow ◽  
High Speed Camera ◽  
Important Process ◽  
Melt Blowing ◽  
Spiral Motion ◽  
Fiber Motion ◽  
Fiber Path ◽  
The Relationship

Melt blowing is an important process for producing nanofibrous nonwovens. Compared to another technology for producing nanofibrous nonwovens, electrospinning, melt blowing applies high-speed air flow field to attenuate the extruded polymer jet. In this study, the air flow field of a swirl die melt-blowing process was simulated by CFD software, Fluent 6.3. The swirling air profile was shown. Meanwhile, a high-speed camera was used to capture the fiber path below a single-orifice melt-blowing swirl die. The spiral motion of the fiber was revealed. The relationship between the fiber path and the air flow field was discussed. This paper shows the relationship between the fiber path and the air flow field in a swirl die melt-blowing process.

Experimental Visualization Study on the Explosion Process of Gasoline Vapor in Narrowly-Confined Space

2013 ◽  
Vol 791-793 ◽  
pp. 2108-2111 ◽  
Author(s):  
Jian Jun Liang ◽  
Yang Du ◽  
Yi Hong Ou ◽  
Xin Sheng Jiang ◽  
Hai Bing Qian ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Data Acquisition ◽  
High Speed ◽  
Development Stage ◽  
High Speed Camera ◽  
Confined Space ◽  
Vapor Explosion ◽  
Gasoline Vapor ◽  
Explosion Process

In this paper, experimental study on gasoline vapor explosion was conducted with data acquisition technology of high-speed camera. In the experiments, the flame behaviors and the flow field movements were shot by the high-speed camera, the space pressure were recorded by high-speed dynamic tester, and the explosion process were analyzed refinedly and intuitively. Studies have shown that according to variations of flame behaviors and pressure characteristics, process of gasoline vapor explosion can be divided into four stages: the ignition stage, the development stage, the intensification stage and the plume stage.

An Experimental Study of Influence of Slits in Throat Position on Suppression of Cavitation Instabilities in Liquid Propellant Rocket Inducer

2019 ◽  
Author(s):  
Moena Kanamaru ◽  
Yoshito Kamikura ◽  
Satoshi Kawasaki ◽  
Takashi Shimura ◽  
Iga Yuka
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Pressure Fluctuation ◽  
High Speed ◽  
Cavity Length ◽  
High Speed Camera ◽  
Liquid Propellant ◽  
Suppression Effect ◽  
Suction Performance ◽  
Propellant Rocket

Abstract Experiments of an inducer with symmetric slits were conducted. The purpose of the study is to explore the suppression effect on cavitation instabilities by slits. The slits are located in a throat position in each blade and it means symmetric slits. The experiments are done through measuring pressure fluctuation in the flow field and shaft displacement and visualization using high speed camera. In this study, the head performance, the suction performance, the cavity length and the occurrence range and the strength of the cavitation instabilities are compared with the results of inducer without slit. As a result, the slit in throat position does not give bad effect on head performance, improves suction performance, and has a relation to suppression of oscillation of cavitation instabilities because of the suppression effect of cavity length, although the occurrence range of super-synchronous rotating cavitation unfortunately increases because the cavity develops slowly.

A Study on Gap Influence on Slamming Experiment

2012 ◽  
Author(s):  
C. W. Park ◽  
J. Y. Shin ◽  
S. H. Kwon ◽  
J. Y. Chung ◽  
S. B. Lee ◽  
...  
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Gap Effect ◽  
High Speed Camera ◽  
Tank Wall ◽  
Central Location ◽  
The Difference

This study presents an investigation of gap effect on slamming experiment. Two gaps were considered; a gap between transverse side of a model and tank wall and a gap between longitudinal end and end of a model. The deadrise angle was fixed 0°. The pressure was measured at the central location and compared. Three different drop heights were chosen to see the difference. A High speed camera was used to record the flow field. Therefore pressure at the center, and flow field around corner of the specimen were analyzed to investigate the gap effect in slamming experiment. The results showed that there was clear influence of the gap in slamming experiment.

Characterization of a Multi-Swirler Fuel Injector Using Simultaneous Laser Based Planar Measurements of Reaction Zone, Flow Field, and Fuel Distribution

2009 ◽  
Author(s):  
P. Iudiciani ◽  
S. M. Hosseini ◽  
R. Zoltan-Szasz ◽  
C. Duwig ◽  
L. Fuchs ◽  
...  
Keyword(s):  
Flow Field ◽  
Flame Stabilization ◽  
Injection System ◽  
Oh Radicals ◽  
Fuel Injector ◽  
Flow Conditions ◽  
Cross Sectional ◽  
Fuel Distribution ◽  
Flame Dynamics ◽  
Wide Range

Modern gas turbine spray combustors feature multiple swirlers with distributed fuel injection system for rapid fuel/air mixing and flame stabilization ensuring low NOx operations. In the present paper, we investigate the effects of different swirler designs on flame characteristics, stabilization, and behavior at lean blow out using a Triple Annular Research Swirler (TARS) burner. Simultaneous planar measurements using laser diagnostics, namely, Planar Laser Induced Fluorescence (LIF) of OH radicals indicating the reacting zone, LIF Acetone indicating unburnt fuel distribution and Particle Image Velocimetry (PIV) for flow field mapping, were applied to study the flow dynamics, fuel distribution and flame dynamics for different swirler geometries, air flow rates, and equivalence ratios. Both axial and nearly perpendicular to axis cross-sectional planes were investigated. The three swirler configurations allowed getting stable and repeatable flames over a wide range of different flow and fuel equivalence ratio conditions, confirming the good flexibility and operability of the TARS burner. Averaged fields are presented to compare the effect of different flow conditions using the same swirler configuration, and the effect of different swirler configurations at the same flow conditions. LIF and PIV instantaneous samples are also shown, both in axial and cross sectional planes, with structures captured in detail. Perfect matching is found between unburnt and burnt field, as well as agreement between axial and cross-sectional measurements. Particular attention has been placed on unstable flames and a highly unsteady flame near the lean blow out (LBO) is shown. Local extinctions are occasionally seen on instantaneous snapshots. Unsteadiness of such flame is suitable to exemplify the use of Proper Orthogonal Decomposition (POD) analysis that identifies the most “energetic” large scale structures or modes of the flame. In particular, rotational and helical modes are observed which can contribute to the swirling flame instability. The results show the effect of the strength and rotation direction of the swirlers can lead to strong flame stratification or to a more homogenous flames. Analysis of the flame dynamics, indicates that the flame can be stabilized dynamically without the presence of a Central Recirculation Zone (CRZ) through flame quenching and flame propagation.

Influence of Main Swirler Vane Angle on the Ignition Performance of TeLESS-II Combustor

2016 ◽  
Author(s):  
Bo Wang ◽  
Chi Zhang ◽  
Yuzhen Lin ◽  
Xin Hui ◽  
Jibao Li
Keyword(s):  
High Speed ◽  
Inlet Temperature ◽  
Main Stage ◽  
Ignition Process ◽  
High Speed Camera ◽  
Fuel Distribution ◽  
Fuel Droplets ◽  
Pilot Fuel ◽  
Cfd Method ◽  
Vane Angle

In order to balance the low emission and wide stabilization for lean premixed prevaporized combustion, the centrally staged layout is preferred in advanced aero-engine combustors. However, compared with the conventional combustor, it is more difficult for the centrally staged combustor to light up as the main stage air layer will prevent the pilot fuel droplets arriving at igniter tip. The goal of the present paper is to study the effect of the main stage air on the ignition of the centrally staged combustor. Two cases of the main swirler vane angle of the TeLESS-II combustor, 20° and 30° are researched. The ignition results at room inlet temperature and pressure show that the ignition performance of the 30° vane angle case is better than that of the 20° vane angle case. High speed camera, PLIF and CFD are used to better understand the ignition results. The high-speed camera has recorded the ignition process, indicated that an initial kernel forms just adjacent the liner wall after the igniter is turned on, the kernel propagates along the radial direction to the combustor center and begins to grow into a big flame, and then it spreads to the exit of the pilot stage, and eventually stabilizes the flame. CFD of the cold flow field coupled with spray field is conducted. A verification of the CFD method has been applied with PLIF measurement, and the simulation results can qualitatively represent the experimental data in terms of fuel distribution. The CFD results show that the radial dimensions of the primary recirculation zone of the two cases are very similar, and the dominant cause of the different ignition results is the vapor distribution of the fuel. The concentration of kerosene vapor of the 30° vane angle case is much larger than that of the 20° vane angle case close to the igniter tip and along the propagation route of the kernel, therefore, the 30° vane angle case has a better ignition performance. For the consideration of the ignition performance, a larger main swirler vane angle of 30° is suggested for the better fuel distribution when designing a centrally staged combustor.

Ignition and Flame Stabilization of a Premixed Jet in Hot Cross Flow

2013 ◽  
Author(s):  
Denise Schmitt ◽  
Michael Kolb ◽  
Johannes Weinzierl ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Equivalence Ratio ◽  
Large Scale ◽  
Large Diameter ◽  
Flame Temperature ◽  
Cross Flow ◽  
Flame Stabilization ◽  
Wide Range ◽  
Cold Case

At the Institute of Thermodynamics, Technical University of Munich a large scale atmospheric combustion test rig has been designed and set up. The experimental setup is comprised of two burning zones: A first zone consists of 16 burners providing vitiated air at 1776K, into which a secondary fuel-air mixture jet is injected and ignited by the hot cross flow. The phenomenon is known in the literature as a reacting jet in hot cross flow. The hot data is compared to the cold case in order to show differences in the flow field due to flame propagation. For evaluating the flow field several experimental analyses have been applied so far (OH*, High-Speed PIV, Mixture Analysis). The focus of this paper is on the momentum ratios J = 4–10 with Jet Reynolds Numbers between 20,000 and 80,000. For the cold case the flow field is measured and compared with the reacting jet. In the injector the air and the natural gas are perfectly premixed. The equivalence ratio of the jet is varied over a wide range of mixtures (ϕ = 0.05–0.77) resulting in an adiabatic flame temperature of the jet between 800 and 2200K. As the pictures of the chemiluminescence analysis show the jet gas ignites immediately upon entering the hot cross flow. The distinct influence of the equivalence ratio on the flame length and shape can be seen in the data. The trajectory of the flame penetrates further into the channel compared to the trajectory of the cold case caused by the reaction in the flame and its resulting gas expansion. Due to the large diameter of the jet in the experiment the origins of the dominant flow patterns are obtained with high spatial resolution. Following this, flame anchoring mechanisms at different operation points are derived.

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