Influence of Transversal Acoustic Excitation of the Burner Approach Flow on the Flame Structure

2010 ◽  
Vol 133 (4) ◽  
Author(s):  
Martin Hauser ◽  
Manuel Lorenz ◽  
Thomas Sattelmayer
Keyword(s):  
Combustion Chamber ◽  
Acoustic Field ◽  
Gas Turbines ◽  
Phase Distribution ◽  
Flame Structure ◽  
Excitation Frequency ◽  
Acoustic Properties ◽  
Acoustic Oscillations ◽  
Test Rig ◽  
Low Frequencies

Modern large gas turbines for power generation have multiple burners, which are distributed around the circumference of the engine and which generate flames in combustors of either annular or can-annular geometry. In both cases, considering only the axial modes has proven to be insufficient for the assessment of the thermoacoustic stability. An adequate analysis requires consideration of the circumferential acoustic coupling generated by the acoustic field in the upstream and downstream annuli and the open passages between the cans, respectively. As in annular combustors, the particularly critical eigenmodes with low frequencies are predominantly of circumferential nature; the stability of annular combustors is often governed by the onset of circumferential acoustic oscillations. To determine the influence of these circumferential acoustic modes on the dynamic flame behavior, a new single burner test rig was developed. The unique acoustic properties of the test rig allow the exposure of a single swirl burner to a two-dimensional acoustic field that resembles the circumferential mode in an annular combustor. Measurements were performed for axial as well as transversal excitation of the burner and the combination of both. To investigate the dynamic flame structure, phase-resolved flame images have been evaluated in terms of amplitude and phase distribution. Under transversal excitation, the flame structure becomes highly asymmetrical. A region of higher OH∗ intensity is generated in the combustion chamber, which rotates with the excitation frequency. From phase-resolved particle image velocimetry (PIV) measurements of the isothermal flow, it is concluded that the transversal excitation modulates the swirl generation leading to an asymmetrical velocity distribution in the burner nozzle and the combustion chamber.

Influence of Transversal Acoustic Excitation of the Burner Approach Flow on the Flame Structure

2010 ◽  
Author(s):  
Martin Hauser ◽  
Manuel Lorenz ◽  
Thomas Sattelmayer
Keyword(s):  
Combustion Chamber ◽  
Acoustic Field ◽  
Gas Turbines ◽  
Phase Distribution ◽  
Flame Structure ◽  
Excitation Frequency ◽  
Acoustic Properties ◽  
Acoustic Oscillations ◽  
Test Rig ◽  
Low Frequencies

Modern large gas turbines for power generation have multiple burners, which are distributed around the circumference of the engine and which generate flames in combustors of either annular or can-annular geometry. In both cases considering only the axial modes has proven to be insufficient for the assessment of the thermoacoustic stability. An adequate analysis requires consideration of the circumferential acoustic coupling, generated by the acoustic field in the upstream and downstream annuli and the open passages between the cans, respectively. As in annular combustors the particularly critical eigenmodes with low frequencies are predominantly of circumferential nature, the stability of annular combustors is often governed by the onset of circumferential acoustic oscillations. To determine the influence of these circumferential acoustic modes on the dynamic flame behavior, a new single burner test rig was developed. The unique acoustic properties of the test rig allow the exposure of a single swirl burner to a two-dimensional acoustic field that resembles the circumferential mode in an annular combustor. Measurements were performed for axial as well as transversal excitation of the burner and the combination of both. To investigate the dynamic flame structure phase-resolved flame images have been evaluated in terms of amplitude and phase distribution. Under transversal excitation the flame structure becomes highly asymmetrical. A region of higher OH*-intensity is generated in the combustion chamber which rotates with the excitation frequency. From phase-resolved PIV measurements of the isothermal flow it is concluded that the transversal excitation modulates the swirl generation leading to an asymmetrical velocity distribution in the burner nozzle and the combustion chamber, respectively.

Transformation of Transverse Acoustic Velocity of the Burner Approach Flow Into Flame Dynamics

2012 ◽  
Author(s):  
Martin Hauser ◽  
Michael Wagner ◽  
Thomas Sattelmayer
Keyword(s):  
Acoustic Field ◽  
Velocity Fluctuation ◽  
Gas Turbines ◽  
Transverse Velocity ◽  
Excitation Frequency ◽  
Rotational Flow ◽  
Acoustic Oscillations ◽  
Flow Oscillation ◽  
Low Frequencies ◽  
The Stability

Modern, large gas turbines for power generation have multiple burners, which are distributed around the circumference of the engine and which generate flames in combustors of either annular or can-annular geometry. In both cases considering only the axial modes has proven to be insufficient for the assessment of the thermoacoustic stability. An adequate analysis requires consideration of the circumferential acoustic coupling, generated by the acoustic field in the upstream and downstream annuli and the open passages between the cans, respectively. As in annular combustors the particularly critical eigenmodes with low frequencies are predominantly of circumferential nature, the stability of annular combustors is often governed by the onset of circumferential acoustic oscillations. In this study one single radial swirl burner is exposed to a transverse velocity fluctuation comparable to a circumferential oscillation in the plenum annulus. The transverse velocity fluctuation is transformed into a rotational flow oscillation through a convective process depending on excitation frequency and mass flow rate. The characteristics of this process are determined and the resulting dynamic flow structure in the burner nozzle is analyzed. Phase plots show that the rotational flow oscillation is transported into the flame causing a rotational flame pulsation. The influence of transverse velocity fluctuation on the global dynamic flame behavior is determined through FTF measurements. It is concluded from the increased FTF amplitude observed for transverse velocity excitation that the modification of the acoustic field at the burner exit due to circumferential acoustic modes has to be taken into account for a reliable prediction of the stability limits of annular gas turbines.

Environmentally Friendly Update of Gas Turbines on Gas Transmission Lines

2006 ◽  
Author(s):  
S. Vesely´ ◽  
A. Soudarev ◽  
E. Vinogradov ◽  
Y. Zacharov
Keyword(s):  
Combustion Chamber ◽  
Transmission Lines ◽  
Gas Turbines ◽  
Environmentally Friendly ◽  
Diffusion Combustion ◽  
Toxic Substances ◽  
Test Rig ◽  
Low Emission ◽  
Wide Range ◽  
Emission Limits

Currently, more than 1,500 gas turbines are in operation on natural gas transmission lines all over Europe. These turbines do not comply with the requirements for toxic substances content in exhaust gases. Therefore, an environmentally friendly update of these turbines is a hot topic now, especially because these turbines are supposed to remain in operation for another 10 or 15 years. Besides, environmentally friendly update is a specific issue that differs from the development of a new low-emission combustion chamber. The authors participated in environmentally friendly update of more than 500 gas turbines of this design in Russia, Ukraine, Slovakia, Czech Republic, Germany, and Hungary. As new emission limits are expected to be issued in the EU, a new low-emission burner was developed that makes use of a combination of kinetic and diffusion combustion to achieve low NOx and CO emissions. The burner operation in combustion chambers of gas turbines is characterized by a wide range of the coefficient of excess air from idle run to full performance. Therefore, the control of the quantity of primary air is necessary. The paper will describe the main stages of the burner research. Tests were performed on an atmospheric pressure test rig where the basic characteristics were gained. The influence of pressure was examined on a special test rig at 0.75–1.1 MPa of pressure. Tests have confirmed that the required NOx and CO emission limits can be achieved with the designed burner. The low emission burner was used for the combustion chamber of a 6 MW gas turbine. The tests performed on a part of a model burner will be presented and an analysis of measurement results will be given.

Experimental Investigation of the Influence of Water Injection on Acoustic Properties of the Exhaust System of a Gas Turbine Combustion Test Rig

2011 ◽  
Author(s):  
Martin Schmid ◽  
Natalie Trott ◽  
Robert Kathan ◽  
Dan Fanaca ◽  
Thomas Sattelmayer
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Droplet Diameter ◽  
Water Injection ◽  
Exhaust System ◽  
Acoustic Properties ◽  
Sonic Velocity ◽  
Test Rig ◽  
Stability Behavior ◽  
Influence Of Water

It is a known phenomenon that single can combustion test rigs and gas turbines have a different stability behavior. Real gas turbines are often more stable than their test rigs. One main difference between test rigs and real engines is the injection of cooling water into the test rigs to reduce the temperature of the exhaust gas and thus to protect the exhaust valve. A literature survey showed that the presence of a two phase flow can drastically reduce the sonic velocity and consequently change the acoustic properties of a system. The aim of this project is to study the influence of water injection on the acoustic properties of a test rig representing the exhaust system of a gas turbine. The experimental results clearly show that the sonic velocity does not change in the present test rig because the droplets are too big to follow the acoustic fluctuations. The critical dimension-less number in this context is the Stokes number, which is mainly determined by the droplet diameter and the acoustic frequency. Furthermore, the experimental results point out that the injected water increases the acoustic damping. It can be concluded from this study that the influence of water injection on the acoustic properties and therefore on the stability behavior is very sensitive to the injection conditions, especially the droplet diameter.

On the Performance of Porous Sound Absorbent Ceramic Lining in a Combustion Chamber Test Rig

2013 ◽  
Author(s):  
Hans-Christoph Ries ◽  
Mateus Vieira Carlesso ◽  
Christian Eigenbrod ◽  
Stephen Kroll ◽  
Kurosch Rezwan
Keyword(s):  
Combustion Chamber ◽  
Sound Pressure Level ◽  
Gas Turbines ◽  
Sound Pressure ◽  
Porous Ceramic ◽  
Pressure Level ◽  
Test Rig ◽  
Resonance Frequencies ◽  
Lean Premixed ◽  
Ceramic Lining

This paper discusses the potential of using porous ceramic lining as insulating material in combustion chambers with respect to their sound absorbent ability to suppress thermoacoustic instabilities. For this purpose a combustion chamber test rig was developed and different types of ceramic linings were tested. The examined range of power was between 40 and 250 kW and the air-propane equivalence ratio was between 1.2 and 2.0. The overall sound pressure level and frequency domain of a lean premixed swirl stabilized and piloted burner are presented. The resonance frequencies and sound pressure levels are obtained and compared for the different combustion chamber linings. The results show a significant decrease in overall sound pressure level by up to 23.5 dB for sound absorbent lining in comparison to the common sound reflecting combustion chamber lining. In summary, sound absorbent ceramic combustion chamber lining can contribute to improve the stability of lean premixed gas turbines.

An Investigation of Turbine Erosion by Combustor Generated Carbon in a Light Weight Marine Gas Turbine

1978 ◽  
Author(s):  
R. J. Russell ◽  
J. J. Witton
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Fuel Type ◽  
Test Rig ◽  
Erosion Process ◽  
Marine Application ◽  
Mineral Dusts

A study has been made of the turbine erosion problem encountered in a marinized aero gas turbine which arose from the change of fuel type necessitated by the marine application. The work has involved the development of a technique for collecting carbon shed from the combustion chamber under engine operating conditions. Tests using the collector were made with a single combustor test rig and compared to engine experience. Combustion chamber modifications were developed having low solids emissions and their emissions characterized using the collector. The data from the collector show that smaller particles than hitherto collected can produce significant long-term erosion and that reduction on both size and quantity of particles is necessary to reduce erosion to acceptable levels. The data obtained in this study are compared with other published information on the basic erosion process and erosion in gas turbines by natural mineral dusts. The implications of the results to current and future engines are discussed.

Numerical Investigation of the Thermo-Acoustic Influence of the Turbine on the Combustor

2015 ◽  
Author(s):  
Federica Farisco ◽  
Lukasz Panek ◽  
Bertram Janus ◽  
Jim B. W. Kok
Keyword(s):  
Reflection Coefficient ◽  
Combustion Chamber ◽  
Gas Turbines ◽  
Main Idea ◽  
High Heat ◽  
Harmonic Excitation ◽  
Forced Response ◽  
Acoustic Oscillations ◽  
Mean Flow ◽  
Lean Premixed Combustion

Lean premixed combustion technology became state-of-the-art in modern gas turbines for power generation to reduce NOx emissions. In these systems, thermo-acoustic oscillations are easily excited in the combustion chamber. Due to the high heat release density, extreme amplitudes can occur which reduce component life or may even cause damage to the engine. Knowledge of the acoustic behavior is required in order to understand and predict these instabilities. This study of the combustor-turbine interaction is focused on the reflection coefficient analysis. The interface between the combustion system and the first turbine stage is the focus area of this study. The rotating components need to be included as outlook of this work. Compressible Large Eddy Simulation (LES) resolving acoustics is applied based on the open source CFD code OpenFOAM. Five cases of increasing complexity are presented. The main idea is to begin the study based on simple geometries such as a convergent-divergent nozzle and two nozzles respectively convergent and divergent, to proceed with increased complexity by adding a vane section, and finally to investigate the behavior of a realistic turbine design. The real engine case consists of an authentic geometry including a can annular combustion chamber and turbine vane section. These cases are studied as basic generic tests in order to validate analytical formulae and to test the CFD methods applied. Calculations with acoustic excitation and non reflecting boundary conditions (NRBC) at the computational inlet and outlet domains are carried out to verify the plausibility of the acoustic set up. The forced response approach is applied provoking a wave excitation at the inlet of the combustion chamber. Multi-harmonic excitation with small amplitudes is used to stay in the linear range. The post-processing for all cases is performed using the two-microphone method in order to calculate the reflection coefficient and the acoustic impedance taking into account the effects of the mean flow.

Experimental and Numerical Investigation of Different Flame Types Inside a Laboratory Scale RQL Combustion Chamber

2019 ◽  
Author(s):  
Thomas von Langenthal ◽  
Nikolaos Zarzalis ◽  
Marco Konle
Keyword(s):  
Flow Field ◽  
Combustion Chamber ◽  
Thermal Power ◽  
Measurement Techniques ◽  
Flame Structure ◽  
Operating Conditions ◽  
Test Rig ◽  
Combustion Chambers ◽  
Primary Zone ◽  
Secondary Air

Abstract RQL (rich burn, quick quench, lean burn) combustion chambers are common in modern aero engines due to their low NOx emissions and good stability. The rich primary zone leads to lower flame temperatures and in combination with the lack of oxygen, the NOx production is low. The mixing of the secondary air must be quick in order to avoid stoichiometric conditions and at the same time must ensure the oxidation of the soot produced in the fuel rich primary zone to keep soot emissions to a minimum. However, the design of such a combustion chamber is complicated due to the complex interaction between the swirling primary flow and the jets of the secondary airflow. In this paper, we present a new test rig, which was designed to study combustion processes inside RQL combustion chambers at atmospheric conditions. The test rig features liquid kerosene combustion and a realistic quenching zone as well as good access for optical and conventional measurement techniques. For realistic engine like conditions the combustion air is preheated to 600 K and the fuel–air equivalence ratio in the primary combustion zone is set to be between Φ = 1.66 and Φ = 1.25, resulting in an overall thermal power between 80 kW and 110 kW. To get insights into the complex flow field inside the combustion chamber unsteady RANS simulations of both the reacting and the non-reacting case were performed using OpenFOAM. The turbulent flow field was modeled using the k-ω-SST model and the combustion was simulated using the Partially Stirred Reactor model. The experimental investigations showed two stable flame types for the same operating conditions with considerable differences in the visible flame structure and soot radiation. The flow field of both of these flame types were measured using a 1.5 kHz 2D PIV System. The numerical simulations showed good overall agreement with the experimental results but could not represent the change in flame type. In order to understand the underlying effects of the flame change the OH* chemiluminescence was recorded and the two-phase flow near the nozzle exit was investigated. This showed that the change in flame structure might arise due to spray dispersion of the pilot fuel nozzle and the recirculation of the secondary air into the primary zone.

Emission Measurements and OH-PLIF of Reacting Hydrogen Jets in Vitiated Crossflow for Stationary Gas Turbines

2012 ◽  
Author(s):  
Mario Roa ◽  
Warren G. Lamont ◽  
Scott E. Meyer ◽  
Peter Szedlacsek ◽  
Robert P. Lucht
Keyword(s):  
Gas Turbines ◽  
Combustion Zone ◽  
Flame Structure ◽  
Combustion Process ◽  
Test Rig ◽  
Gas Turbine Combustor ◽  
Depth Of Penetration ◽  
Jet In Crossflow ◽  
Air Jet ◽  
Sampling Probe

An optically accessible gas turbine combustor test rig was constructed to study the combustion characteristics of a coaxial hydrogen/air jet injected into a vitiated swirl crossflow. The test rig has two combustion zones. The main combustion zone (MCZ) is a swirl stabilized dump combustor, and the secondary combustion zone (SCZ) is a reacting crossflow jet, referred to as the jet-in-crossflow (JIC). The SCZ is located downstream of the MCZ. The JIC is a coaxial hydrogen/air jet that penetrates radially into the vitiated stream. The combustor was designed to study the effects of JIC conditions on the SCZ combustion process and in particular on NOx production. The jet velocity and equivalence ratio were systematically varied. A water-cooled sampling probe was used to extract exhaust gases downstream of the SCZ for emission measurements. The JIC flame structure was captured by OH-PLIF images which show the extent of the flame front and the depth of penetration into the vitiated stream. The OH-PLIF images were averaged to determine the JIC reaction zone and were compared to the Holdeman correlation.

Acoustic Nearfield Characteristics of a Premixed Flame in a Longitudinal Acoustic Field

2001 ◽  
Author(s):  
Doh-Hyoung Lee ◽  
Tim C. Lieuwen
Keyword(s):  
Acoustic Field ◽  
Acoustic Waves ◽  
Near Field ◽  
Premixed Flame ◽  
Acoustic Wave Equation ◽  
Acoustic Oscillations ◽  
Acoustic Characteristics ◽  
Low Frequencies ◽  
Longitudinal Acoustic ◽  
One Dimensional

The occurrence of self excited, combustion driven oscillations pose significant problems in lean, premixed gas turbine combustors. The interactions between flames and longitudinal acoustic oscillations play a key role in many of these instabilities. This paper analyzes the acoustic field in the vicinity of a premixed flame front in order to clarify these interactions. Specifically, it describes a numerical analysis of the acoustic characteristics of a premixed flame that is excited by longitudinal disturbances. Solutions are determined from an integral formulation of the acoustic wave equation that is solved via boundary element techniques. Analyses of these results are performed to characterize the deviations of the acoustic field from one-dimensionality. First, as can be anticipated from quasi one-dimensional considerations, the flame’s reflection coefficient is lower than that predicted by purely one-dimensional calculations. The results also show that the acoustic pressure is nearly one-dimensional in the vicinity of the flame. Finally, they show that the velocity oscillations are strongly multidimensional, even in acoustically compact flames. At very low frequencies, these local velocity oscillations are in phase with each other, while at higher frequencies, their phase may change significantly along the flame. The results of this study show that the multidimensional nature of the acoustic velocity oscillations in the near field of the flame must be taken into consideration in analyses of the interactions between acoustic waves and flames.

Sign in / Sign up

Export Citation Format

Share Document