Thermoacoustic Analysis of a Full Annular Lean Burn Aero-Engine Combustor

2013 ◽  
Author(s):  
Antonio Andreini ◽  
Bruno Facchini ◽  
Andrea Giusti ◽  
Ignazio Vitale ◽  
Fabio Turrini
Keyword(s):  
Heat Release ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Thermal Fluctuations ◽  
Injection System ◽  
Combustion Instabilities ◽  
Lean Burn ◽  
Acoustic Effect ◽  
Lean Combustion ◽  
Critical Issues

In order to reduce NOx emissions, modern gas turbines are often equipped with lean burn combustion systems, where the engine operates near the lean blow-out limits. One of the most critical issues of lean combustion technology is the onset of combustion instabilities related to a coupling between pressure oscillations and thermal fluctuations excited by the unsteady heat release. In this work a thermoacoustic analysis of a full annular combustor developed by AVIO is discussed. The system is equipped with an advanced PERM (Partially Evaporating and Rapid Mixing) injection system based on a piloted lean burn spray flame generated by a pre-filming atomizer. Combustor walls are based on multi-perforated liners to control metal temperature: these devices are also recognized as very effective sound absorbers, thus in innovative lean combustors they could represent a good means both for wall cooling and damping combustion instabilities. The performed analysis is based on the resolution of the eigenvalue problem related to an inhomogeneous wave equation which includes a source term representing heat release fluctuations (the so called Flame Transfer Function, FTF) in the flame region using a three-dimensional FEM code. A model representing the entire combustor was assembled including all the acoustically relevant geometrical features. In particular, the acoustic effect of multi-perforated liners was introduced by modeling the corresponding surfaces with an equivalent internal impedance. Different simulations with and without the presence of the flame were performed analyzing the influence of the multi-perforated liners. Furthermore, different modeling approaches for the FTF were examined and compared with each other. Comparisons with available experimental data showed a good agreement in terms of resonant frequencies in the case of passive simulations. On the other hand, when the presence of the flame is considered, comparisons with experiments showed the inadequacy of FTFs commonly used for premixed combustion and thus the necessity of an improved FTF, more suitable for liquid fueled gas turbines where the evaporation process could play an important role in the flame heat release fluctuations.

The Research of Lean Combustion Characteristic of Compound Injection System of Direct Injection Engine

2014 ◽  
Vol 532 ◽  
pp. 362-366 ◽  
Author(s):  
Jiang Feng Mou ◽  
Rui Qing Chen ◽  
Yi Wei Lu
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Injection System ◽  
Intake Manifold ◽  
Combustion Characteristic ◽  
Injection Timing ◽  
Mixed Gas ◽  
Lean Burn ◽  
Direct Injection Engine ◽  
Lean Combustion

This paper studies the lean burn limit characteristic of the compound injection system of the direct-injection gasoline engine. The low pressure nozzle on the intake manifold can achieve quality homogeneous lean mixture, and the direct injection in the cylinder can realized the dense mixture gas near the spark plug. By adjusting the two injection timing and injection quantity, and a strong intake tumble flow with special shaped combustion chamber, it can produces the reverse tumble to form different hierarchical levels of mixed gas in the cylinder. Experimental results show: the compound combustion system to the original direct-injection engine lean burn limit raise 1.8-2.5 AFR unit.

Three-dimensional organization of the flow structure in a non-reactive model aero engine lean burn injection system

2014 ◽  
Vol 52 ◽  
pp. 164-173 ◽  
Author(s):  
Giuseppe Ceglia ◽  
Stefano Discetti ◽  
Andrea Ianiro ◽  
Dirk Michaelis ◽  
Tommaso Astarita ◽  
...  
Keyword(s):  
Flow Structure ◽  
Three Dimensional ◽  
Injection System ◽  
Lean Burn ◽  
Aero Engine

Active Control of Combustion Instabilities in a Matrix Burner Using Primary and Pilot Fuel and Acoustic Forcing

2010 ◽  
Author(s):  
Dieter Bohn ◽  
Nils Ohlendorf ◽  
Frank Weidner ◽  
James F. Willie
Keyword(s):  
Heat Release ◽  
Mass Flow ◽  
Gas Turbines ◽  
Open Loop ◽  
Nox Emissions ◽  
Combustion Instabilities ◽  
Loop Control ◽  
First Case ◽  
Pilot Fuel ◽  
Acoustic Forcing

Lean premixed flames applied in modern gas turbines leads to reduce NOx emissions, but at the same time they are more susceptible to combustion instabilities than diffusion flames. These oscillations cause pressure fluctuations with high amplitudes and unacceptable noise as well as the risk of component or even engine failure. They can lead to pockets of fuel being formed in the mixing chamber and to bad mixing, which leads to increase in emissions. This paper reports the successful decoupling of the pressure and heat release inside the combustion chamber of a matrix burner using two actuation techniques. This led to the successful attenuation of the dominant instability modes occurring inside the combustor of the matrix burner. In the first case, acoustic forcing was used to decouple the pressure and the heat release inside the combustor. This was achieved by using a loudspeaker to modulate the primary air mass flow. This was followed by using acoustic forcing in CFD to decouple the pressure and heat release inside the combustor. For the action of the loudspeaker, sinusoidal forcing was used to mimic the modulation action of the diaphragm of the loudspeaker. In the second case, a fast gaseous “on-off” injector was used to modulate the primary fuel mass flow. After this, pilot fuel modulation was used to stabilize the flame. The control law governing the primary and pilot fuel modulation is discussed in details. The effect of open loop control on NOx emissions in the burner is also reported and discussed.

CFD Aerodynamic and Reactive Study of an Innovative Lean Combustion System in the Frame of the NEWAC Project

2010 ◽  
Author(s):  
Alessandro Marini ◽  
Lorenzo Bucchieri ◽  
Antonio Peschiulli
Keyword(s):  
Numerical Procedure ◽  
Research Programme ◽  
Injection System ◽  
Combustion System ◽  
Lean Burn ◽  
The Core ◽  
Numerical Tests ◽  
Lean Combustion ◽  
Annular Combustor ◽  
The Eu

This paper deals with the very last activities carried out by EnginSoft in the frame of the EU funded research programme NEWAC. The work regards the pre-production numerical tests performed on the single annular combustor with the purpose of verify its performance in reactive frame. The core of this study is the innovative lean-burn injection system technology, developed by University of Karlsruhe and AVIO for medium OPR. Such device has been widely investigated in previous activities in order to optimise the combustor layout and the numerical procedure for this work [1].

A Quantitative Comparison Between a Low Order Model and a 3D FEM Code for the Study of Thermoacoustic Combustion Instabilities

2011 ◽  
Author(s):  
Giovanni Campa ◽  
Sergio Mario Camporeale ◽  
Anai¨s Guaus ◽  
Julien Favier ◽  
Matteo Bargiacchi ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Quantitative Comparison ◽  
Complex Eigenvalue ◽  
Combustion Instabilities ◽  
Order Model ◽  
Element Method ◽  
Low Order

The study of thermoacoustic combustion instabilities has an important role for safety operation in modern gas turbines equipped with lean premixed dry low emission combustion systems. Gas turbine manufacturers often adopt simulation tools based on low order models for predicting the phenomenon of humming. These simulation codes provide fast responses and good physical insight, but only one-dimensional or two-dimensional simplified schemes can be generally examined. The finite element method can overcome such limitations, because it allows to examine three-dimensional geometries and to search the complex eigenfrequencies of the system. Large Eddy Simulation (LES) techniques are proposed in order to investigate the instability phenomenon, matching pressure fluctuations with turbulent combustion phenomena to study thermoacoustic combustion oscillations, even if they require large numerical resources. The finite element approach solves numerically the Helmholtz equation problem converted in a complex eigenvalue problem in the frequency domain. Complex eigenvalues of the system allow us to identify the complex eigenfrequencies of the combustion system analyzed, so that we can have a valid indication of the frequencies at which thermoacoustic instabilities are expected and of the growth rate of the pressure oscillations at the onset of instability. Through the collaboration among Ansaldo Energia, University of Genoa and Polytechnic University of Bari, a quantitative comparison between a low order model, called LOMTI, and the three-dimensional finite element method has been examined, in order to exploit the advantages of both the methodologies.

Effect of Hydrogen Content on the Gas Turbine Combustion Performance of Synthetic Natural Gas

2013 ◽  
Author(s):  
Min Chul Lee ◽  
Seik Park ◽  
Uisik Kim ◽  
Sungchul Kim ◽  
Jisu Yoon ◽  
...  
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Gas Turbine ◽  
Hydrogen Content ◽  
Gas Turbines ◽  
Combustion Instabilities ◽  
Synthetic Natural Gas ◽  
Natural Gases ◽  
Combustion Performance ◽  
Gas Turbine Combustion

This paper investigates the effect of hydrogen content on the gas turbine combustion performance of synthetic natural gases to determine whether they are adaptable to industrial gas turbines. Synthetic natural gases which are composed of methane, propane and varying amounts of hydrogen (0%, 1%, 3% and 5%), are tested in ambient pressure and high temperature conditions at the combustion test facility of a 60kWth industrial gas turbine. Combustion instabilities, flame structures, temperatures at nozzle, dump plane and turbine inlet, and emissions of NOx and CO are investigated for the power outputs from 35 to 60kWth. With increasing hydrogen content, combustion instabilities are slightly alleviated and the frequency of pressure fluctuation and heat release oscillation is increased. NOx and CO emissions are almost similar in trends and amounts for all tested fuels, and the undesirable phenomena from addition of hydrogen such as flashback, auto-ignition and overheating of fuel nozzle were not observed. Synthetic natural gas with less than 1% hydrogen showed no difference in gas turbine combustion characteristics, while synthetic natural gases containing hydrogen of over 3% showed a slight difference in combustion instability such as amplitude and frequency of pressure fluctuations and heat release oscillations. From these results, we conclude that the synthetic natural gas containing less than 1% hydrogen is adaptable without retrofitting any part of the combustor, and Korea coal-SNG Quality Standard Bureau is planning to establish the SNG quality standards, guaranteeing hydrogen content of up to 1%.

Improvement of Impaired Combustion Conditions at Some Off-Design Operation by Driving a Precisely Controlled Modulation of the Burner Air Feed

2017 ◽  
Author(s):  
Fabrice Giuliani ◽  
Lukas Pfefferkorn ◽  
Gerhard Kraft
Keyword(s):  
Gas Turbines ◽  
Operating Conditions ◽  
Forced Flow ◽  
Combustion Instabilities ◽  
Resonant Frequencies ◽  
Positive Effects ◽  
Lean Combustion ◽  
Swirling Flame ◽  
Pulse Combustion ◽  
Load Conditions

A non-conventional method based on forced-flow combustion oscillations is investigated regarding the improvement of combustion conditions at suboptimal operating conditions. In the field of gas turbines, uncontrolled combustion oscillations are called combustion instabilities and they have been extensively studied over the last two decades. Low NOx systems that operate in the lean combustion domain are prone to enable combustion instabilities. A common way to investigate combustion instabilities is to reproduce these with help of an acoustic driver, e.g. using a loudspeaker or a fast valve in order to drive forced-flow combustion oscillations. When the oscillations match with one of the natural resonant frequencies of the combustor cavities or of the feeding pipes, the thermoacoustic coupling can occur in a well-controlled way. Some positive effects of this type of forcing can be found in the literature. In a similar context, it was shown in a previous work (GT2015-42377) under which conditions and by how far a forced-flow thermoacoustic drive can further push the lean-blow-out limits in the lean region. Following to this work, it is described that driving a resonant flame can also be beneficial regarding combustion quality. Better combustion performances were observed with the help of pulsating the burner air feed at part-load conditions on a premixed swirling flame, where combustion quality is known to be impaired at steady-state. The presented technology can then be seen as a flexible On-Off thermoacoustic drive, based on forced pulse combustion and using a siren tunable in frequency and amplitude in a refined way. The benefits and the challenges about its hypothetic implementation in the field of turbomachinery conclude this paper.

scholarly journals Numerical analysis of the dynamic flame response of a spray flame for aero-engine applications

2017 ◽  
Vol 9 (4) ◽  
pp. 310-329 ◽  
Author(s):  
Alessandro Innocenti ◽  
Antonio Andreini ◽  
Bruno Facchini ◽  
Antonio Peschiulli
Keyword(s):  
Injection System ◽  
Lean Burn ◽  
Droplet Dynamics ◽  
Spray Flame ◽  
Spray Flames ◽  
Aero Engine ◽  
Critical Issues ◽  
Flame Response ◽  
Acoustic Instabilities ◽  
The Impact

Incoming standards on NO x emissions are motivating many aero-engine manufacturers to adopt the lean burn combustion concept. One of the most critical issues affecting this kind of technology is the occurrence of thermo-acoustic instabilities that may compromise combustor life and integrity. Therefore the prediction of the thermo-acoustic behaviour of the system becomes of primary importance. In this paper, the complex interaction between the system acoustics and a turbulent spray flame for aero-engine applications is numerically studied. The dynamic flame response is computed exploiting reactive URANS simulations and system identification techniques. Great attention has been devoted to the impact of liquid fuel evolution and droplet dynamics. For this purpose, the GE Avio PERM (partially evaporating and rapid mixing) lean injection system has been analysed, focussing attention on the effect of several modelling parameters on the combustion and on the predicted flame response. A frequency analysis has also been set up and exploited to obtain even more insight on the dynamic flame response of the spray flame. The application is one of the few in the literature where the dynamic flame response of spray flames is numerically investigated, providing a description in terms of flame transfer function and detailed information on the physical phenomena.

Experimental and Computational Results of Distributed Combustion for Application in Current Gas Turbine Engine Combustor Architectures

2011 ◽  
Author(s):  
Nick Overman ◽  
Jason Ryon
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Swirling Flow ◽  
Numerical Test ◽  
Injection System ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Lean Burn ◽  
Lean Combustion ◽  
Improved Performance

Current development and testing has lead to a fuel/air injection system for application in gas turbine engines that produces ultra low emissions and stable, lean combustion. The system is designed to operate with current combustor architectures similar to existing gas turbine engines. This paper presents both experimental and numerical test results demonstrating the benefits of such technology including extremely low emissions of NOx, CO, and un-burned hydrocarbons (UHC). Primary focus is on experimental results demonstrating reaction distribution and emissions. Numerical confirmation of flow field dynamics was used to develop an understanding of the re-circulation rates within the combustor and impact on reaction behavior. Several design configurations were tested to investigate the effects of aerodynamic stagnation point and fuel placement with respect to the aerodynamic shear layer produced by the swirling flow field. Test conditions were varied, including inlet air temperature and injector pressure drop for monitoring effects on the operating envelope of distributed reaction and on lean blow out limit. Results demonstrate the improved performance of a system capable of operating in a flameless or distributed reaction mode over that of a typical lean burn system.

Effect of Cooling Liner on Acoustic Energy Absorption and Flame Response

2010 ◽  
Author(s):  
Umesh Bhayaraju ◽  
Johannes Schmidt ◽  
Karthik Kashinath ◽  
Simone Hochgreb
Keyword(s):  
Transfer Function ◽  
Heat Release ◽  
Acoustic Waves ◽  
Bluff Body ◽  
Acoustic Energy ◽  
Combustion Instabilities ◽  
Acoustic Damping ◽  
Lean Combustion ◽  
Bias Flow ◽  
Flame Response

Gas turbine combustors with lean combustion injectors are prone to thermo-acoustic/combustion instabilities. Several passive techniques have been developed to control combustion instabilities, such as using Helmholtz resonators or viscous dampers using perforated liners that have potential for broadband acoustic damping. In this paper the role of single-walled cooling liners is considered in the damping of acoustic waves and on the flame transfer function in a sample bluff-body burner. Three liner geometries are considered: no bias flow (solid liner), normal effusion holes, and grazing effusion holes at 25° inclination. Cold flow experiments with speaker forcing are carried out to characterise the absorption properties of the liner and compared with an acoustic network model. The results show that whereas the bulk of the acoustic losses is due to the vortex recirculation zones, the liners contribute significantly to the absorption over a wide area of the frequency range. The flame transfer function gain is measured as a function of bias flow for a given operating condition of the burner. The experiments show that for the geometry considered, the global flame transfer function is little affected by cooling except in the case of the normal flow holes. Further analysis shows that whereas the total flame transfer function is not affected, the flame heat release becomes more spatially distributed along the axial length, and a 1D flame response shows distinct modes corresponding to the modal heat release locations.

Sign in / Sign up

Export Citation Format

Share Document