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.

Characterization of Lean Burn Module Air Blast Pilot Injector With Laser Techniques

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
U. Meier ◽  
S. Freitag ◽  
J. Heinze ◽  
L. Lange ◽  
E. Magens ◽  
...  
Keyword(s):  
Flow Field ◽  
Soot Formation ◽  
Test Methods ◽  
Oh Radicals ◽  
Main Stage ◽  
Fuel Injector ◽  
Lean Burn ◽  
Fuel Ratio ◽  
Optical Test ◽  
Planar Laser

For lean burn combustor development in low emission aero-engines, the pilot stage of the fuel injector plays a key role with respect to stability, operability, NOx emissions, and smoke production. Therefore it is of considerable interest to characterize the pilot module in terms of pilot zone mixing, fuel placement, flow field, and interaction with the main stage. This contribution focuses on the investigation of soot formation during pilot-only operation. Optical test methods were applied in an optically accessible single sector rig at engine idle conditions. Using planar laser-induced incandescence (LII), the distribution of soot and its dependence on air/fuel ratio, as well as geometric injector parameters, was studied. The data shows that below a certain air/fuel ratio, an increase of soot production occurs. This is in agreement with smoke number measurements in a standard single sector flame tube rig without optical access. Reaction zones were identified using chemiluminescence of OH radicals. In addition, the injector flow field was investigated with PIV. A hypothesis regarding the mechanism of pilot smoke formation was made based on these findings. This along with further investigations will form the basis for developing strategies for smoke improvement at elevated pilot-only conditions.

CFD Analysis of Fuel Distribution in Concentric Swirling Flows in a Reverse Flow Gas Turbine Combustor

2006 ◽  
Author(s):  
K. Sudhakar Reddy ◽  
D. N. Reddy ◽  
C. M. Vara Prasad
Keyword(s):  
Gas Turbine ◽  
Reverse Flow ◽  
Distribution Patterns ◽  
Swirling Flows ◽  
Cfd Analysis ◽  
Fuel Injector ◽  
Gas Turbine Combustor ◽  
Fuel Distribution ◽  
Wide Range ◽  
Injection Pressures

This paper presents the results of numerical investigations of a turbulent, swirling and recirculating flow without combustion inside a reverse flow gas turbine combustor. In order to establish the characteristics of fuel distribution patterns of the fuel spray injected into swirling flows, flow fields are analyzed inside the swirl combustor for varying amount of swirl strength using a commercial CFD code fluent 6.1.22. Three Dimensional computations are performed to study the influence of the various parameters like injection pressure, flow Reynolds number and Swirl Strength on the fuel distribution patterns. The model predictions are compared against the experimental results, and its applicability over a wide range of flow conditions was investigated. It was observed from the CFD analysis, that the fuel decay along the axis is faster with low injection pressures compared to higher injection pressures. With higher Reynolds numbers the fuel patterns are spreading longer in the axial direction. The higher momentum of the air impedes the radial mixing and increases the constraint on the jet spread. The results reveal that an increase in swirl enhances the mixing rate of the fuel and air and causes recirculation to be more pronounced and to occur away form the fuel injector. The CFD predictions are compared with the experimental data from the phototransistor probe measurements, and good agreement has been achieved.

A Simulation Study of Magnetostrictive Material Terfenol-D in Automotive CNG Fuel Injection Actuation

2009 ◽  
Vol 154 ◽  
pp. 41-46 ◽  
Author(s):  
H.A. Chowdhury ◽  
Saiful Amri Mazlan ◽  
Abdul Ghani Olabi
Keyword(s):  
Flow Rate ◽  
Fuel Injection ◽  
Response Times ◽  
Turbulence Models ◽  
High Energy ◽  
Injection System ◽  
Fuel Injector ◽  
Cross Sectional ◽  
Magnetostrictive Material ◽  
Fast Control

Magnetostriction is the deformation that spontaneously occurs in ferromagnetic materials when an external magnetic field is applied. In applications broadly defined for actuation, magnetostrictive material Terfenol-D (Tb0.3Dy0.7Fe1.9) possesses intrinsic rapid response times while providing small and accurate displacements and high-energy efficiency. These are some of the essential parameters required for fast control of fuel injector valves for decreased engine emissions and lower fuel consumption compared with the traditional solenoid fuel injection system. A prototype CNG fuel injector assembly was designed which included magnetostrictive material Terfenol-D as the actuator material. A 2D cross-sectional geometry of the injector assembly, which incorporated both linear and non-linear magnetic properties of the corresponding materials, was modeled in ANSYS for 2D axisymmetric magnetic simulation. Subsequently, a 3D replica of the CNG flow conduit was modeled in GAMBIT with the resultant injector lift. The meshed conduit was then simulated in FLUENT using the 3D time independent segregated solver with the Standard k  , the Realizable k   and RSM turbulence models to predict the mass flow rate of CNG to be injected. Eventually, the simulated flow rate was verified against mathematically derived static flow rate required for a standard automotive fuel injector considering standard horsepower, BSFC and injector duty cycle.

On the Influence of Fuel Distribution on the Flame Structure of Bluff-Body Stabilized Flames

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Jeffery A. Lovett ◽  
Kareem Ahmed ◽  
Oleksandr Bibik ◽  
Andrew G. Smith ◽  
Eugene Lubarsky ◽  
...  
Keyword(s):  
Reaction Zone ◽  
Bluff Body ◽  
Fuel Injection ◽  
Flame Structure ◽  
Reacting Flow ◽  
Oh Radicals ◽  
Fuel Distribution ◽  
Jet In Crossflow ◽  
Wide Range ◽  
Stabilized Flames

This paper describes recent learning on the flame structure associated with bluff-body stabilized flames and the influence of the fuel distribution with nonpremixed, jet-in-crossflow fuel injection. Recent experimental and analytical results disclosing the flame structure are discussed in relation to classical combustion reaction zone regimes. Chemiluminescence and planar fluorescence imaging of OH* radicals as an indicator of the flame zone are analyzed from various tests conducted at Georgia Tech using a two-dimensional vane-type bluff-body with simple wall-orifice fuel injectors. The results described in this paper support the view that combustion occurs in separated flame zones aligned with the nonpremixed fuel distribution associated with the fuel jets that are very stable and contribute to flame stability at low fuel flow rates. The experimental data is also compared with computational reacting flow large-eddy simulations and interpreted in terms of the fundamental reaction zone regimes for premixed flames. For the conditions of the present experiment, the results indicate combustion occurs over a wide range of flame regimes including the broken reaction zone or separated flamelet regimes.

Effect of Slot Injection and Effusion Array on the Liner Heat Transfer Coefficient of a Scaled Lean Burn Combustor With Representative Swirling Flow

2015 ◽  
Author(s):  
Antonio Andreini ◽  
Riccardo Becchi ◽  
Bruno Facchini ◽  
Alessio Picchi ◽  
Fabio Turrini
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Flame Stabilization ◽  
Recirculation Region ◽  
Flow Conditions ◽  
Lean Burn ◽  
Cooling Flows ◽  
The Impact

International standards regarding polluting emissions from civil aircraft engines are becoming gradually even more stringent. Nowadays, the most prominent way to meet the target of reducing NOx emissions in modern aero-engine combustors is represented by lean burn technology. Swirl injectors are usually employed to provide the dominant flame stabilization mechanism coupled to high efficiency fuel atomization solutions. These systems generate very complex flow structures such as recirculations, vortex breakdown and processing vortex core, that affect the distribution and therefore the estimation of heat loads on the gas side of the liner as well as the interaction with the cooling system flows. The main purpose of the present work is to provide detailed measurements of Heat Transfer Coefficient (HTC) on the gas side of a scaled combustor liner highlighting the impact of the cooling flows injected through a slot system and an effusion array. Furthermore, for a deeper understanding of the interaction phenomena between gas and cooling flows, a standard 2D PIV (Particle Image Velocimetry) technique has been employed to characterize the combustor flow field. The experimental arrangement has been developed within EU project LEMCOTEC and consists of a non-reactive three sectors planar rig installed in an open loop wind tunnel. Three swirlers, replicating the real geometry of a GE Avio PERM (Partially Evaporated and Rapid Mixing) injector technology, are used to achieve representative swirled flow conditions in the test section. The effusion geometry is composed by a staggered array of 1236 circular holes with an inclination of 30deg, while the slot exit has a constant height of 5mm. The experimental campaign has been carried out using a TLC (Thermochromic Liquid Crystals) steady state technique with a thin Inconel heating foil and imposing several cooling flow conditions in terms of slot coolant consumption and effusion pressure drop. A data reduction procedure has been developed to take into account the non-uniform heat generation and the heat loss across the liner plate. Results, in terms of 2D maps and averaged distributions of HTC have been supported by flow field measurements with 2D PIV technique focussed on the corner recirculation region.

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.

Effect of Fuel Distribution on Spray Dynamics in a Two-Staged Multi-Injection Burner

2011 ◽  
Author(s):  
T. Providakis ◽  
L. Zimmer ◽  
P. Scouflaire ◽  
S. Ducruix
Keyword(s):  
Velocity Field ◽  
High Frequency ◽  
Gas Turbines ◽  
Low Frequency ◽  
Flame Stabilization ◽  
Pollutant Emissions ◽  
Reactive Flow ◽  
Mean Values ◽  
Fuel Distribution ◽  
Flame Dynamics

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. Non-reactive and reactive flows are characterized through an extensive Phase Doppler Anemometry (PDA) campaign. Three staging values, corresponding to three different flame stabilization processes, are analyzed, while power is kept constant. It is shown that mean values and droplet distributions are affected by the staging procedure in the non-reactive as in the reactive situations. Using adequate post-processing, it is also possible to study non-reactive and reactive flow/flame dynamics. Spectral analysis shows that the non-reactive flow is strongly structured by a high frequency rotating structure that can clearly be associated with a precessing vortex core (PVC), while the reactive situation encounters a strong acoustic-flame coupling leading to a low frequency oscillation of both the velocity field and the spray droplet distribution. In this last situation, high frequency phenomena, which may be due to PVC, are still visible.

Flow Field and Flame Dynamics of Swirling Methane and Hydrogen Flames at Dry and Steam-Diluted Conditions

2014 ◽  
Author(s):  
Steffen Terhaar ◽  
Oliver Krüger ◽  
Christian Oliver Paschereit
Keyword(s):  
Flow Field ◽  
Heat Release ◽  
Combustion Process ◽  
Helical Structure ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Reconstruction Technique ◽  
Complete Suppression ◽  
Wide Range

The majority of recent stationary gas turbine combustors employ swirling flows for flame stabilization. The swirling flow undergoes vortex breakdown and exhibits a complex flow field including zones of recirculating fluid and regions of high shear. Often, self-excited helical flow instabilities are found in these flows that may influence the combustion process in beneficial and adverse ways. In the present study we investigate the occurrence and shape of self-excited hydrodynamic instabilities and the related heat-release fluctuations over a wide range of operating conditions. We employ high-speed stereoscopic particle image velocimetry and simultaneous OH*-chemiluminescence imaging to resolve the flow velocities and heat release distribution, respectively. The results reveal four different flame shapes: A detached annular flame, a long trumpet shaped flame, a typical V-flame, and a very short flame anchored near the combustor inlet. The flame shapes were found to closely correlate with the reactivity of the mixture. Highly steam-diluted or very lean flames cause a detachment, whereas hydrogen fuel leads to very short flames. The detached flames feature a helical instability, which in terms of frequency and shape is similar to the isothermal case. A complete suppression of the helical structure is found for the V-flame. Both, the trumpet shaped flame and the very short flame feature helical instabilities of different frequencies and appearances. The phase-averaged OH*-chemiluminescence images show that the helical instabilities cause large scale-heat release fluctuations. The helical structure of the fluctuations is verified using a tomographic reconstruction technique.

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.

PIV Measurements of Combustor Turbulence Fields

2007 ◽  
Author(s):  
Adrian Spencer ◽  
David Hollis ◽  
Jon Carrotte
Keyword(s):  
Flow Field ◽  
Jet Impingement ◽  
Structure Identification ◽  
Fuel Injector ◽  
Reynolds Stresses ◽  
Isothermal Model ◽  
Validation Data ◽  
Complete Mapping ◽  
Wide Range ◽  
Filtering Effect

An experimental study has been conducted on a full-scale, three-sector, isothermal model of a gas turbine combustor. PIV has been used as the main instrumentation technique and this has been validated against LDA and hot-wire velocity measurements of the same geometry. These data combine to provide high quality boundary condition and validation data for CFD predictions. Substantial care has been taken in assuring the quality of the PIV data. In high turbulence intensity flow fields, low pass spatial filtering can artificially reduce the Reynolds stresses calculated from the PIV measured velocities. The level of this filtering depends upon the ratio of the integral lengthscales in the flow field to the size of the measurement volume of the PIV interrogation cell. Within the highly turbulent flow field of a combustor there exist a very wide range of turbulent length scales. Consideration should therefore be given to any measurements taken in a combustor, hot or cold, to take account of this sub-grid filtering effect. A method is described to overcome this problem and it is demonstrated to be successful by comparing with LDA and PIV data (at increased magnification) that does not suffer this problem. Sparse LDA and HWA data for the combustor is thus complemented by more dense planar PIV data to allow a more complete mapping of the velocity field. This has allowed better understanding of the processes occurring in the combustor such as the jet impingement process and the fuel injector swirler flow interaction with the primary jets. In addition detailed information on turbulence statistics, integral lengthscales, spatial correlation and energetic structure identification is available.

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