On the Use of Helmholtz Resonators for Damping Acoustic Pulsations in Industrial Gas Turbines

2001 ◽  
Author(s):  
Valter Bellucci ◽  
Christian Oliver Paschereit ◽  
Peter Flohr ◽  
Fulvio Magni
Keyword(s):  
Heat Release ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Structural Integrity ◽  
Combustion Process ◽  
Low Frequency ◽  
Operating Regime ◽  
Pressure Pulsations ◽  
Helmholtz Resonators ◽  
Resonance Frequencies

In modern gas turbines operating with premix combustion flames, the suppression of pressure pulsations is an important task related to the quality of the combustion process and to the structural integrity of engines. High pressure pulsations may occur when the resonance frequencies of the system are excited by heat release fluctuations independent of the acoustic field (“loudspeaker” behavior of the flame). Heat release fluctuations are also generated by acoustic fluctuations in the premixed stream. The feedback mechanism inherent in such processes (“amplifier” behavior of the flame) may lead to combustion instabilities, the amplitude of pulsations being limited only by nonlinearities. In this work, the application of Helmholtz resonators for damping low-frequency pulsations in gas turbine combustion chambers is discussed. We present a nonlinear model for predicting the acoustic response of resonators including the effect of purging air. Atmospheric experiments are used to validate the model, which is employed to design a resonator arrangement for damping low-frequency pulsations in an ALSTOM GT11N2 gas turbine. The predicted damper impedances are used as the boundary condition in the three-dimensional analysis of the combustion chamber. The suggested arrangement leads to a significant extension of the low-pulsation operating regime of the engine.

On the Use of Helmholtz Resonators for Damping Acoustic Pulsations in Industrial Gas Turbines

2004 ◽  
Vol 126 (2) ◽  
pp. 271-275 ◽  
Author(s):  
V. Bellucci ◽  
P. Flohr ◽  
C. O. Paschereit ◽  
F. Magni
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Low Frequency ◽  
Operating Regime ◽  
Acoustic Response ◽  
Combustion Chambers ◽  
Helmholtz Resonators ◽  
Industrial Gas Turbines ◽  
Significant Extension

In this work, the application of Helmholtz resonators for damping low-frequency pulsations in gas turbine combustion chambers is discussed. We present a nonlinear model for predicting the acoustic response of resonators including the effect of purging air. Atmospheric experiments are used to validate the model, which is employed to design a resonator arrangement for damping low-frequency pulsations in an ALSTOM GT11N2 gas turbine. The predicted damper impedances are used as the boundary condition in the three-dimensional analysis of the combustion chamber. The suggested arrangement leads to a significant extension of the low-pulsation operating regime of the engine.

scholarly journals Comprehensive Thermodynamic Analysis of the Humphrey Cycle for Gas Turbines with Pressure Gain Combustion

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3521 ◽  
Author(s):  
Panagiotis Stathopoulos
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Combustion Process ◽  
Ideal Gas ◽  
Point Of View ◽  
Pressure Gain Combustion ◽  
Combustion Technology ◽  
Secondary Air ◽  
And Performance ◽  
The Impact

Conventional gas turbines are approaching their efficiency limits and performance gains are becoming increasingly difficult to achieve. Pressure Gain Combustion (PGC) has emerged as a very promising technology in this respect, due to the higher thermal efficiency of the respective ideal gas turbine thermodynamic cycles. Up to date, only very simplified models of open cycle gas turbines with pressure gain combustion have been considered. However, the integration of a fundamentally different combustion technology will be inherently connected with additional losses. Entropy generation in the combustion process, combustor inlet pressure loss (a central issue for pressure gain combustors), and the impact of PGC on the secondary air system (especially blade cooling) are all very important parameters that have been neglected. The current work uses the Humphrey cycle in an attempt to address all these issues in order to provide gas turbine component designers with benchmark efficiency values for individual components of gas turbines with PGC. The analysis concludes with some recommendations for the best strategy to integrate turbine expanders with PGC combustors. This is done from a purely thermodynamic point of view, again with the goal to deliver design benchmark values for a more realistic interpretation of the cycle.

Measurement and Analysis of Flame Transfer Function in a Sector Combustor Under High Pressure Conditions

2003 ◽  
Author(s):  
W. S. Cheung ◽  
G. J. M. Sims ◽  
R. W. Copplestone ◽  
J. R. Tilston ◽  
C. W. Wilson ◽  
...  
Keyword(s):  
High Pressure ◽  
Transfer Function ◽  
Heat Release ◽  
Gas Turbine ◽  
Mass Flow ◽  
Atmospheric Pressure ◽  
Acoustic Waves ◽  
Gas Turbines ◽  
Transfer Functions ◽  
Unsteady Pressure

Lean premixed prevaporised (LPP) combustion can reduce NOx emissions from gas turbines, but often leads to combustion instability. A flame transfer function describes the change in the rate of heat release in response to perturbations in the inlet flow as a function of frequency. It is a quantitative assessment of the susceptibility of combustion to disturbances. The resulting fluctuations will in turn generate more acoustic waves and in some situations self-sustained oscillations can result. Flame transfer functions for LPP combustion are poorly understood at present but are crucial for predicting combustion oscillations. This paper describes an experiment designed to measure the flame transfer function of a simple combustor incorporating realistic components. Tests were conducted initially on this combustor at atmospheric pressure (1.2 bar and 550 K) to make an early demonstration of the combustion system. The test rig consisted of a plenum chamber with an inline siren, followed by a single LPP premixer/duct and a combustion chamber with a silencer to prevent natural instabilities. The siren was used to induce variable frequency pressure/acoustic signals into the air approaching the combustor. Both unsteady pressure and heat release measurements were undertaken. There was good coherence between the pressure and heat release signals. At each test frequency, two unsteady pressure measurements in the plenum were used to calculate the acoustic waves in this chamber and hence estimate the mass-flow perturbation at the fuel injection point inside the LPP duct. The flame transfer function relating the heat release perturbation to this mass flow was found as a function of frequency. The same combustor hardware and associated instrumentation were then used for the high pressure (15 bar and 800 K) tests. Flame transfer function measurements were taken at three combustion conditions that simulated the staging point conditions (Idle, Approach and Take-off) of a large turbofan gas turbine. There was good coherence between pressure and heat release signals at Idle, indicating a close relationship between acoustic and heat release processes. Problems were encountered at high frequencies for the Approach and Take-off conditions, but the flame transfer function for the Idle case had very good qualitative agreement with the atmospheric-pressure tests. The flame transfer functions calculated here could be used directly for predicting combustion oscillations in gas turbine using the same LPP duct at the same operating conditions. More importantly they can guide work to produce a general analytical model.

Bearing Housing Design for Vibration Control, Using Tilting Pad Bearings Instead of Lemon-Bore Type on a Gas Turbine

2020 ◽  
Author(s):  
Chippa Anil ◽  
Aparna Satheesh ◽  
Babu Santhanagopalakrishnan ◽  
Marcin Bielecki
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Structural Integrity ◽  
Plane Surface ◽  
Rotor Dynamics ◽  
Turbine Rotor ◽  
Outer Diameter ◽  
Housing Design ◽  
Tilting Pad ◽  
And Performance

Abstract Heavy duty gas turbines are usually equipped with hydrodynamic bearings which are either lemon-bore or tilting pad type. Baker Hughes legacy gas turbines use these two types of bearings, and its selection is based on 1) considering pros & cons from Rotor dynamics, 2) bearing performance, 3) bearing housing stiffness, 4) vibration detection & control. Non-contact probes are used to monitor the vibrations of rotor. Majority of legacy gas turbines are not equipped with these probes. Due to this fact, over the years it resulted in non-detection of dynamics & vibration issue, which caused frequent bearing replacement. As the increase in industry demand to apply and measure vibrations using non-contact probes on bearings, an effort was made by Baker Hughes to implement these on existing fleet units. Also, in order to increase rotor dynamics stability of low-pressure rotor, to improve bearing life and performance, effort was made to replace lemon-bore bearings with tilting pad. This paper demonstrates efforts made to design the titling pad which would fit within envelop of already available bearing housing. Bearing/shaft clearance, bearing performance, modification of bearing retainer clearances are the mandatory tasks which would be dealt in this study. The swap of bearing type, and its effect on whole gas turbine rotor dynamic stability, checking the frequency crossovers with Campbell diagram would also be dealt in this paper. This paper also focuses on assessment on oil passage routing, temperature & proximity probe instrumentation routing design. Re-design is performed by analyzing various configuration, assessing different sensitivity studies & validation of modified bearing housing from structural integrity, ultimate load capability, & split plane oil leakage retention and its comparison with baseline are most important aspects of finalization of this change, which will be showcased in this paper. Instrumentation routing was a critical task when the considering bearing replacement from lemon-bore to tilting pad. As lemon-bore type bearings just have an elliptical inner surface, it’s quite easy to install the thermocouples into a simple hole. But as replacement has tilting pads, the challenge is to instrument the pads without effecting their movement and functionality. Such best practices are also dealt in this paper. Comparison of tilting-pad with lemon-bore, considering the fixed shaft diameter, the retainer outer diameter of tilting pad is higher than lemon-bore. This effect has a change in bearing seat on bearing housing, thereby reducing the effective stiffness of the housing, and the reduced split plane surface. To tackle this situation, several sensitivities were executed, by re-modifying the bolts and bolt holes on the existing housing, without modifying the housing envelop.

Experimental Development of On-Line Flame Transfer Function Measurements for Fielded Gas Turbines

2021 ◽  
Author(s):  
Austin Matthews ◽  
Anna Cobb ◽  
Subodh Adhikari ◽  
David Wu ◽  
Tim Lieuwen ◽  
...  
Keyword(s):  
Transfer Function ◽  
Heat Release ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Transfer Functions ◽  
Full Scale ◽  
Fuel Injector ◽  
Experimental Development ◽  
On Line

Abstract Understanding thermoacoustic instabilities is essential for the reliable operation of gas turbine engines. To complicate this understanding, the extreme sensitivity of gas turbine combustors can lead to instability characteristics that differ across a fleet. The capability to monitor flame transfer functions in fielded engines would provide valuable data to improve this understanding and aid in gas turbine operability from R&D to field tuning. This paper presents a new experimental facility used to analyze performance of full-scale gas turbine fuel injector hardware at elevated pressure and temperature. It features a liquid cooled, fiber-coupled probe that provides direct optical access to the heat release zone for high-speed chemiluminescence measurements. The probe was designed with fielded applications in mind. In addition, the combustion chamber includes an acoustic sensor array and a large objective window for verification of the probe using high-speed chemiluminescence imaging. This work experimentally demonstrates the new setup under scaled engine conditions, with a focus on operational zones that yield interesting acoustic tones. Results include a demonstration of the probe, preliminary analysis of acoustic and high speed chemiluminescence data, and high speed chemiluminescence imaging. The novelty of this paper is the deployment of a new test platform that incorporates full-scale engine hardware and provides the ability to directly compare acoustic and heat release response in a high-temperature, high-pressure environment to determine the flame transfer functions. This work is a stepping-stone towards the development of an on-line flame transfer function measurement technique for production engines in the field.

New Catalytic Combustion Technology for Very Low Emissions Gas Turbines

1994 ◽  
Author(s):  
R. A. Dalla Betta ◽  
J. C. Schlatter ◽  
S. G. Nickolas ◽  
D. K. Yee ◽  
T. Shoji
Keyword(s):  
Thermal Shock ◽  
Gas Turbine ◽  
High Temperatures ◽  
Gas Turbines ◽  
Catalytic Combustion ◽  
Combustion Process ◽  
Combustion System ◽  
Gas Turbine Combustors ◽  
Homogeneous Combustion ◽  
Combustion Technology

A catalytic combustion system has been developed which feeds full fuel and air to the catalyst but avoids exposure of the catalyst to the high temperatures responsible for deactivation and thermal shock fracture of the supporting substrate. The combustion process is initiated by the catalyst and is completed by homogeneous combustion in the post catalyst region where the highest temperatures are obtained. This has been demonstrated in subscale test rigs at pressures up to 14 atmospheres and temperatures above 1300°C (2370°F). At pressures and gas linear velocities typical of gas turbine combustors, the measured emissions from the catalytic combustion system are NOx < 1 ppm, CO < 2 ppm and UHC < 2 ppm, demonstrating the capability to achieve ultra low NOx and at the same time low CO and UHC.

Validation of Advanced Computational Methods for Determining Flame Transfer Functions in Gas Turbine Combustion Systems

2007 ◽  
Author(s):  
Krzysztof Kostrzewa ◽  
Berthold Noll ◽  
Manfred Aigner ◽  
Joachim Lepers ◽  
Werner Krebs ◽  
...  
Keyword(s):  
System Identification ◽  
Heat Release ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Transfer Functions ◽  
Sound Waves ◽  
Gas Turbine Combustion ◽  
Combustion Systems ◽  
Combustion Processes ◽  
Gas Turbine Burner

The operation envelope of modern gas turbines is affected by thermoacoustically induced combustion oscillations. The understanding and development of active and passive means for their suppression is crucial for the design process and field introduction of new gas turbine combustion systems. Whereas the propagation of acoustic sound waves in gas turbine combustion systems has been well understood, the flame induced acoustic source terms are still a major topic of investigation. The dynamics of combustion processes can be analyzed by means of flame transfer functions which relate heat release fluctuations to velocity fluctuations caused by a flame. The purpose of this paper is to introduce and to validate a novel computational approach to reconstruct flame transfer functions based on unsteady excited RANS simulations and system identification. Resulting time series of velocity and heat release are then used to reconstruct the flame transfer function by application of a system identification method based on Wiener-Hopf formulation. CFD/SI approach has been applied to a typical gas turbine burner. 3D unsteady simulations have been performed and the flame transfer results have been validated by comparison to experimental data. In addition the method has been benchmarked to results obtained from sinusoidal excitations.

The Characteristics of Radial Turbines for Small Gas Turbines

2003 ◽  
Author(s):  
C. Rodgers
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Structural Integrity ◽  
Velocity Ratio ◽  
Turbine Rotor ◽  
Flow Coefficient ◽  
Cycle Performance ◽  
Radial Turbine ◽  
Auxiliary Power Units ◽  
Axial Turbines

Inward flow radial and mixed flow turbines are effectively utilized in both small gas turbine auxiliary power units (APU’s) and turbochargers, where moderately high levels of efficiency can be readily attained with simple cast components, less sensitive to blade end-gap clearances than axial turbines. This paper provides an overview of radial turbine performance characteristics for small gas turbine applications as basically influenced by specific speed, velocity ratio, exit flow coefficient, and rotor tip to exducer root mean square (RMS) diameter ratio. Since turbine rotor mass and inertia play important roles in structural integrity and engine acceleration characteristics, the importance of turbine velocity ratio selection upon rotor tip diameter, and cycle performance are discussed. The effects of rotor reaction on radial turbine flow versus pressure characteristics are examined pertinent to engine matching requirements. Engine transient performance is addressed, as influenced by turbine operation towards and beyond runaway conditions.

Aero Structure Interaction for Mechanical Integration of Laced LP Compressor Blades in a Gas Engine Rotor

2016 ◽  
Author(s):  
Vinayaka Nagarajaiah ◽  
Nilotpal Banerjee ◽  
B. S. Ajay Kumar ◽  
Kumar K. Gowda
Keyword(s):  
Gas Turbine ◽  
Cross Sections ◽  
Gas Turbines ◽  
Structural Integrity ◽  
Operating Conditions ◽  
Free Standing ◽  
Compressor Blades ◽  
Elliptical Cross ◽  
Structure Interaction ◽  
Mechanical Integrity

Aero-structure interaction during turbomachinery blade design has become an important area of research due to its critical applications in aero engines and land based gas turbines. Studies reveal that a certain mistuning leads to stress build up through mode localization under operating conditions. This paper deals with comparative case studies of aero-structure interaction for free standing and various laced LP blade configurations of a gas turbine. The lacing wire provides better structural integrity as it is more aerodynamic and feasible when compared to cases of free standing blades without lacing wires. Hence calling for the optimum positioning checks at ¼th, ½, ¾th and combined positioning at ¼th and ¾th along the length of LP compressor blades. The lacing wire of both circular and elliptical cross sections are considered for comparative study for better aerodynamic performance. Assuming 100% fixity at blade root, the study involves critical parametric evaluations involved in achieving mechanical integrity in airfoil design and blade platform design. Mechanical integrity involves stress checks, frequency margins, Campbell Diagram, gross yield stress, Stress Stiffening and Spin Softening of blades and so on, for design and off-design conditions for a given stage efficiency of 93% in an ideal LP compressor of a gas turbine engine.

Combustion Oscillations in Bluff Body Stabilized Diffusion Flames With Variable Length Inlet

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
M. Madanmohan ◽  
S. Pandey ◽  
A. Kushari ◽  
K. Ramamurthi
Keyword(s):  
Heat Release ◽  
Phase Angle ◽  
Bluff Body ◽  
Diffusion Flames ◽  
Combustion Process ◽  
Low Frequency ◽  
Pressure Oscillations ◽  
Pipe Length ◽  
Entry Length ◽  
Low Frequency Oscillations

This paper describes the results of an experimental study to understand the influence of inlet flow disturbances on the dynamics of combustion process in bluff body stabilized diffusion flames of liquid petroleum gas and air. The results show the influence of weak disturbances created by the change in incoming pipe length on the amplitude of pressure oscillations and the phase angle between pressure and heat release. It is seen that the phase delay increases as the entry length increases. The rms value of pressure, however, generally falls with the increase in length. The phase angle is seen to be in the second quadrant, showing that the heat release oscillations damp the pressure oscillations. Therefore, the decrease in the phase angle results in the reduction in damping and hence an increase in pressure fluctuations. The dominant frequencies of combustion oscillations are found to be the low frequency oscillations, and the frequency of oscillations increases with a decrease in the inlet pipe length and an increase in the flow Reynolds number. It is suggested that such low frequency oscillations are driven by vortex shedding at the wake of the bluff body, which energizes the diffusion and mixing process.

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