Numerical and Experimental Flame Stabilization Analysis in the New Spinning Combustion Technology Framework

2020 ◽  
Author(s):  
Pasquale Walter Agostinelli ◽  
Yi Hao Kwah ◽  
Stephane Richard ◽  
Gorka Exilard ◽  
James R. Dawson ◽  
...  
Keyword(s):  
Film Cooling ◽  
Flame Stabilization ◽  
Fuel Injector ◽  
Azimuthal Component ◽  
Thermoacoustic Instabilities ◽  
Annular Combustor ◽  
Combustion Technology ◽  
Experimental Side ◽  
Spinning Combustion ◽  
Swirled Flames

Abstract Global warming, climate change and pollution are burning environmental issues. To reduce the carbon footprint of the aviation sector, aeronautical companies have been striving to lower engine emissions via the development of reliable lean combustors. In this context, effort has been devoted to the better understanding of various flame dynamics with emphasis on thermoacoustic instabilities, lean blow-off and extinctions. In line with this effort, Safran Helicopter Engines has recently developed and patented the revolutionary spinning combustion technology (SCT) for its next generation of combustors. This technology has indeed great flexibility when it comes to ignition and blow-off capabilities. To better understand the various physical mechanisms occurring in a SCT combustor, a joint numerical and experimental analysis of the flame stabilization in this spinning combustion technology framework has been devised. On the experimental side, the NTNU atmospheric annular combustor has been modified to introduce a relevant azimuthal component of velocity while operating under premixed fuel conditions, following the SCT concept. Note that to reduce temperature at the backplane of the chamber, film cooling is incorporated to avoid fuel injector damage. On the numerical side, high fidelity Large Eddy Simulations of the test bench have been carried out with the AVBP code developed at CERFACS, providing insights on the flame stabilization in this unique SCT geometry. In particular, it is noted that there is a strong interaction between the cooling film and the highly swirled flames exiting from the fuel injector bend. In that respect, changing the injector or global equivalence ratios while operating the SCT is shown to affect the combustion of this design.

Numerical and Experimental Flame Stabilization Analysis in the New Spinning Combustion Technology Framework

2021 ◽  
Author(s):  
Pasquale Walter Agostinelli ◽  
Yi Hao Kwah ◽  
Stephane Richard ◽  
Gorka Exilard ◽  
James R. Dawson ◽  
...  
Keyword(s):  
Flame Stabilization ◽  
Combustion Technology ◽  
Spinning Combustion

Assessment of Aero-Thermal Design Methodology for Effusion Cooled Lean Burn Annular Combustors

2014 ◽  
Author(s):  
A. Andreini ◽  
B. Facchini ◽  
L. Mazzei ◽  
L. Bellocci ◽  
F. Turrini
Keyword(s):  
Film Cooling ◽  
Cooling System ◽  
Heat Removal ◽  
Protective Layer ◽  
Aircraft Engine ◽  
Thermal Design ◽  
Heat Transfer Analysis ◽  
Lean Burn ◽  
Annular Combustor ◽  
Combustion Technology

Increasingly stringent limitations imposed on aircraft engine emissions have led many manufacturers toward lean combustion technology, which involves a relevant increase in mass flow rate dedicated to primary combustion, leading as a consequence to a reduction of air dedicated to cooling of liners. One of the most promising cooling techniques in such conditions is represented by effusion cooling, which consists of an array of closely spaced discrete film cooling holes. This cooling method is based on a protective layer of cooling flow on the hot side of the liner, enhancing at the same time the heat removal within the holes. In the latest years many aero engine manufacturers have increased the research and technology investment on this combustion technology. Working in partnership with the University of Florence, specific component design tools and experimental techniques have been improved by Avio Aero for combustor gas turbine investigation. From a design perspective, CFD analysis has become a key tool up to the early stages of novel combustor design process, producing affordable direct 3D optimization of combustor aerodynamics. Nevertheless, a RANS simulation of even only a single sector of an annular combustor still presents a challenge when the cooling system is taken into account. This issue becomes more critical in case of modern effusion cooled combustors, which may contain up to two thousand holes for the single sector. For this reason, many efforts have been devoted to develop methodologies based on film cooling modeling. Among the approaches published in the literature, models based on local sources represent a good compromise between simplicity and accuracy, with the capability to automatically perform a Conjugate Heat Transfer analysis. This type of methodology has been already defined and validated by the authors, with comparison on effusion cooled plates in terms of experimental overall effectiveness measurements as well as the application on a tubular combustor test case. In the context of this work, the proposed approach has been applied to the analysis of a lean annular combustor with the purpose of investigating pressure losses, flow split and metal temperature field. The results obtained have been compared to experimental data and different numerical tools exploited during the preliminary design of these devices.

Exploitation of Measured Flame Transfer Functions for a Two-Phase Lean Fuel Injector to Predict Thermoacoustic Modes in Full Annular Combustors

2014 ◽  
Author(s):  
M. A. Macquisten ◽  
M. Whiteman ◽  
S. R. Stow ◽  
A. J. Moran
Keyword(s):  
Transfer Functions ◽  
Early Stage ◽  
Linear Perturbation ◽  
Combustion System ◽  
Fuel Injector ◽  
Two Phase ◽  
Thermoacoustic Instabilities ◽  
Annular Combustor ◽  
Linear Perturbation Theory ◽  
Lean Fuel

Thermoacoustic instabilities are a limitation on the operability of any combustion system, especially under lean fuel conditions. The ability to avoid or eliminate rumble, especially at an early stage of the development of a combustion system, is a useful capability. The occurrence of thermoacoustic modes can be predicted by an acoustic network of the combustion system, where the aerodynamic/flame interaction is described by a flame transfer function. In the EC funded KIAI project a series of tasks were performed to measured flame transfer functions of lean fuel injectors with the aim of predicting thermoacoustic Eigen modes in a full annular combustion rig. The linear flame transfer functions, of the injector, were measured at Cambridge University on a single intermediate pressure sector siren rig via OH* and CH* chemiluminescence and unsteady pressure measurements. These flame transfer functions were implemented in a low order acoustic network of the rig in the form of an inverse FFT method. The acoustic network uses linear perturbation theory, where the Eigen modes are solved by satisfying the acoustic boundary conditions. Alternatively, the acoustic network can be used to predict the forced pressure response of the system. Finally, the network was used to predict the frequencies, stability and spectra in a full annular combustor rig, utilising the same injector.

The Civic: A Concept in Vortex Induced Combustion for the Solar Gemini 10 kW Gas Turbine

1981 ◽  
Vol 103 (1) ◽  
pp. 34-42 ◽  
Author(s):  
J. R. Shekleton
Keyword(s):  
Gas Turbine ◽  
Diffusion Flames ◽  
Reynolds Numbers ◽  
Flame Stabilization ◽  
Fuel Injector ◽  
Combustion Chambers ◽  
Turbine Generator ◽  
Fuel Injectors ◽  
Swirl Flame ◽  
Combustion Processes

The Radial Engine Division of Solar Turbines International, an Operating Group of International Harvester, under contract to the U.S. Army Mobility Equipment Research & Development Command, developed and qualified a 10 kW gas turbine generator set. The very small size of the gas turbine created problems and, in the combustor, novel solutions were necessary. Differing types of fuel injectors, combustion chambers, and flame stabilizing methods were investigated. The arrangement chosen had a rotating cup fuel injector, in a can combustor, with conventional swirl flame stabilization but was devoid of the usual jet stirred recirculation. The use of centrifugal force to control combustion conferred substantial benefit (Rayleigh Instability Criteria). Three types of combustion processes were identified: stratified and unstratified charge (diffusion flames) and pre-mix. Emphasis is placed on five nondimensional groups (Richardson, Bagnold, Damko¨hler, Mach, and Reynolds numbers) for the better control of these combustion processes.

Acoustic Damper Placement and Tuning for Annular Combustors: An Adjoint-Based Optimization Study

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Georg A. Mensah ◽  
Jonas P. Moeck
Keyword(s):  
Helmholtz Equation ◽  
Gas Turbines ◽  
Algebraic Models ◽  
Combustion Chambers ◽  
Thermoacoustic Instabilities ◽  
Helmholtz Resonators ◽  
Major Threat ◽  
Optimization Study ◽  
Annular Combustor ◽  
Parameter Values

Thermoacoustic instabilities pose a major threat to modern gas turbines. The use of acoustic dampers, like Helmholtz resonators, has proven useful for the mitigation of such instabilities. However, assessing the effect of acoustic dampers on thermoacoustic modes in annular combustion chambers remains an intricate task. This results from the implicit nature of the thermoacoustic Helmholtz equation associated with the high number of possible parameter values for the positioning of the dampers and their impedance design. In the present work, the principal challenges of the effective placement and the design of the impedance of acoustic dampers in annular chambers are discussed. This includes the choice of an appropriate objective function for the optimization, the combinatorial challenges when dealing with different possible damper arrangements, and the numerical complexities when using the thermoacoustic Helmholtz equation to approach this issue. As a key aspect, the paper proposes a new adjoint-based approach to tackle these problems. The new algorithm establishes algebraic models that predict the effect of acoustic dampers on the growth rates of the thermoacoustic modes. The theory is exemplified on the basis of a generic annular combustor model with 12 burners.

813 Low-Pressure Flame Stabilization Experiments on Modification of Fuel Injector of the Sub-Scale Precooled Turbojet Engine to Liquid Fuel Usage

2012 ◽  
Vol 2012.18 (0) ◽  
pp. 285-286
Author(s):  
Katsuya KIKKAWA ◽  
Hiroshi NOMURA ◽  
Kazutaka MICHISHITA ◽  
Keichi OKAI ◽  
Motoyuki HONGO
Keyword(s):  
Liquid Fuel ◽  
Low Pressure ◽  
Flame Stabilization ◽  
Fuel Injector ◽  
Turbojet Engine

Full Scale Testing of a Low Swirl Fuel Injector Concept for Ultra-Low NOx Gas Turbine Combustion Systems

2006 ◽  
Author(s):  
Waseem Nazeer ◽  
Kenneth Smith ◽  
Patrick Sheppard ◽  
Robert Cheng ◽  
David Littlejohn
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Pressure Oscillation ◽  
Test Results ◽  
Combustion System ◽  
Fuel Injector ◽  
Annular Combustor ◽  
Swirl Injector ◽  
Gas Turbine Combustion

The continued development of a low swirl injector for ultra-low NOx gas turbine applications is described. An injector prototype for natural gas operation has been designed, fabricated and tested. The target application is an annular gas turbine combustion system requiring twelve injectors. High pressure rig test results for a single injector prototype are presented. On natural gas, ultra-low NOx emissions were achieved along with low CO. A turndown of approximately 100°F in flame temperature was possible before CO emissions increased significantly. Subsequently, a set of injectors was evaluated at atmospheric pressure using a production annular combustor. Rig testing again demonstrated the ultra-low NOx capability of the injectors on natural gas. An engine test of the injectors will be required to establish the transient performance of the combustion system and to assess any combustor pressure oscillation issues.

Autoignition of Hydrogen / Natural Gas / Nitrogen Fuel Mixtures at Reheat Combustor Operating Conditions

2012 ◽  
Author(s):  
Julia Fleck ◽  
Peter Griebel ◽  
Manfred Aigner ◽  
Adam M. Steinberg
Keyword(s):  
Natural Gas ◽  
High Speed ◽  
Volume Fraction ◽  
Fluid Dynamic ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Mixing Zone ◽  
Fuel Injector ◽  
Jet Penetration ◽  
Penetration Depths

Previous autoignition studies at conditions relevant to reheat combustor operation have indicated that the presence of relatively small amounts of natural gas (NG) in H2/N2 fuel significantly changes the autoignition behavior. The present study further elucidates the influence of NG on autoignition, kernel propagation, and subsequent flame stabilization at conditions that are relevant for the practical operation of gas turbine reheat combustors (p = 15 bar, Tinlet > 1000 K, hot flue gas, appropriate residence times). The experimental investigation was carried out in a generic, optically accessible reheat combustor. Autoignition events in the mixing zone were recorded by a high-speed camera at frame rates of up to 30,000 fps. This paper describes the autoignition behavior as the H2 volume fraction is increased (decreasing NG) in a H2/NG/N2 fuel mixture for two different jet penetration depths. Additionally, the subsequent flame stabilization phenomena and the structure of the stabilized flame are discussed. The results reveal that autoignition kernels occurred even for the lowest H2 fuel fraction, but they did not initiate a stable flame in the mixing zone. Increasing the H2 volume fraction decreased the distance between the initial position of the autoignition kernels and the fuel injector, finally leading to flame stabilization. The occurrence of autoignition kernels at lower H2 volume fractions (H2/(H2+NG) < 85%) was not found to be significantly influenced by the fluid dynamic and mixing field differences related to the different jet penetration depths. In contrast, autoignition leading to flame stabilization was found to depend on jet penetration; flame stabilization occurred at lower H2 fractions for the higher jet penetration depth (H2/(H2+NG) ≈ 89 compared to H2/(H2+NG) ≈ 95 vol. %).

Development of a Liquid-Fueled, Lean-Premixed Gas Turbine Combustor

1993 ◽  
Vol 115 (3) ◽  
pp. 554-562 ◽  
Author(s):  
L. H. Cowell ◽  
K. O. Smith
Keyword(s):  
Gas Turbine ◽  
Performance Testing ◽  
Operating Conditions ◽  
Operating Parameters ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Design Variables ◽  
Lean Premixed ◽  
Annular Combustor ◽  
Injector Design

Development of a lean-premixed, liquid-fueled combustor is in progress to achieve ultra-low NOx emissions at typical gas turbine operating conditions. A filming fuel injector design was tested on a bench scale can combustor to evaluate critical design and operating parameters for low-emissions performance. Testing was completed using No. 2 diesel. Key design variables tested include premixing length, swirler angle, injector centerbody diameter, and reduced liner cooling. NOx emissions below 12 ppmv at 9 bar pressure were measured. Corresponding CO levels were 50 ppmv. An optimized injector design was fabricated for testing in a three injector sector of an annular combustor. Operating parameters and test results are discussed in the paper.

scholarly journals Weakly nonlinear analysis of thermoacoustic instabilities in annular combustors

2016 ◽  
Vol 805 ◽  
pp. 52-87 ◽  
Author(s):  
G. Ghirardo ◽  
M. P. Juniper ◽  
J. P. Moeck
Keyword(s):  
Gas Turbines ◽  
Practical Importance ◽  
Industrial Applications ◽  
Local Pressure ◽  
Weakly Nonlinear ◽  
Acoustic Damping ◽  
Thermoacoustic Instabilities ◽  
Rotationally Symmetric ◽  
Flame Response ◽  
Annular Combustor

Rotationally symmetric annular combustors are of practical importance because they generically resemble combustion chambers in gas turbines, in which thermoacoustically driven oscillations are a major concern. We focus on azimuthal thermoacoustic oscillations and model the fluctuating heat release rate as being dependent only on the local pressure in the combustion chamber. We study the dynamics of the annular combustor with a finite number of compact flames equispaced around the annulus, and characterize the flames’ response with a describing function. We discuss the existence, amplitude and the stability of standing and spinning waves, as a function of: (i) the number of the burners; (ii) the acoustic damping in the chamber; (iii) the flame response. We present the implications for industrial applications and the future direction of investigations. We then present as an example the first theoretical study of thermoacoustic triggering in annular combustors, which shows that rotationally symmetric annular chambers that are thermoacoustically unstable do not experience only stable spinning solutions, but can also experience stable standing solutions. We finally test the theory on one experiment with good agreement.

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