Spatially distributed flame transfer functions for predicting combustion dynamics in lean premixed gas turbine combustors

2010 ◽  
Vol 157 (9) ◽  
pp. 1718-1730 ◽  
Author(s):  
K.T. Kim ◽  
J.G. Lee ◽  
B.D. Quay ◽  
D.A. Santavicca
Keyword(s):  
Gas Turbine ◽  
Transfer Functions ◽  
Combustion Dynamics ◽  
Gas Turbine Combustors ◽  
Lean Premixed ◽  
Spatially Distributed

scholarly journals Thermoacoustic Instability Considerations for High Hydrogen Combustion in Lean Premixed Gas Turbine Combustors: A Review

Hydrogen ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 33-57
Author(s):  
Jadeed Beita ◽  
Midhat Talibi ◽  
Suresh Sadasivuni ◽  
Ramanarayanan Balachandran
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Hydrogen Combustion ◽  
Dynamic State ◽  
Pure Hydrogen ◽  
High Hydrogen ◽  
Combustion Dynamics ◽  
Thermoacoustic Instability ◽  
Gas Turbine Combustors ◽  
Lean Premixed

Hydrogen is receiving increasing attention as a versatile energy vector to help accelerate the transition to a decarbonised energy future. Gas turbines will continue to play a critical role in providing grid stability and resilience in future low-carbon power systems; however, it is recognised that this role is contingent upon achieving increased thermal efficiencies and the ability to operate on carbon-neutral fuels such as hydrogen. An important consideration in the development of gas turbine combustors capable of operating with pure hydrogen or hydrogen-enriched natural gas are the significant changes in thermoacoustic instability characteristics associated with burning these fuels. This article provides a review of the effects of burning hydrogen on combustion dynamics with focus on swirl-stabilised lean-premixed combustors. Experimental and numerical evidence suggests hydrogen can have either a stabilising or destabilising impact on the dynamic state of a combustor through its influence particularly on flame structure and flame position. Other operational considerations such as the effect of elevated pressure and piloting on combustion dynamics as well as recent developments in micromix burner technology for 100% hydrogen combustion have also been discussed. The insights provided in this review will aid the development of instability mitigation strategies for high hydrogen combustion.

Characteristic Time Model Correlation of NOx Emissions From Lean Premixed Combustors

1995 ◽  
Author(s):  
Donald M. Newburry ◽  
Arthur M. Mellor
Keyword(s):  
Gas Turbine ◽  
Diffusion Flame ◽  
Characteristic Time ◽  
Equivalence Ratio ◽  
Nox Emissions ◽  
Time Model ◽  
New Model ◽  
Gas Turbine Combustors ◽  
Ratio Data ◽  
Lean Premixed

The semi–empirical characteristic time model (CTM) has been used previously to correlate and predict emissions data from conventional diffusion flame, gas turbine combustors. The form of the model equation was derived for NOx emissions from laboratory flameholders and then extended to conventional gas turbine combustors. The model relates emissions to the characteristic times of distinct combustion subprocesses, with empirically determined model constants. In this paper, a new model is developed for lean premixed (LP) NOx emissions from a perforated plate flameholder combustor burning propane fuel. Several modifications to the diffusion flame CTM were required, including a new activation energy and a more complicated dependence on combustor pressure. Appropriate model constants were determined from the data, and the correlation results are reasonable. An attempt was made to validate the new model with LP NOx data for a different but geometrically similar flameholder operating at lower pressures. The predictions are good for the low equivalence ratio data. However, a systematic error in the reported equivalence ratios may be adversely affecting the predictions of the higher equivalence ratio data through the calculated adiabatic flame temperature.

Model Based Active Combustion Control Concept for Reduction of Pulsations and NOx Emissions in Lean Premixed Gas Turbine Combustors

2008 ◽  
Author(s):  
Ernst Schneider ◽  
Stephan Staudacher ◽  
Bruno Schuermans ◽  
Haiwen Ye
Keyword(s):  
Gas Turbine ◽  
Gaussian Processes ◽  
Nox Emissions ◽  
Combustion Control ◽  
Model Based Control ◽  
Thermoacoustic Instabilities ◽  
Gas Turbine Combustors ◽  
Model Based ◽  
Lean Premixed ◽  
Control Concept

Strict environmental regulations demand gas turbine operation at very low equivalence ratios. Premixed gas turbine combustors, operated at very lean conditions, are prone to thermoacoustic instabilities. Thermoacoustic instabilities cause significant performance and reliability problems in gas turbine combustors, so their prevention is a general task. Splitting the fuel mass flow between different burner groups, i.e. using a burner group fuel staging technique, is a possibility to control the thermoacoustic instabilities. The resulting combustion perturbations have also effects on the gas turbine NOx emissions making it necessary to find an optimum balance between pulsations and emissions. This paper presents a model based active combustion control concept for the reduction of pulsations and emissions in lean premixed gas turbine combustors. The model is integrated in an observer structure derived from a Luenberger observer. The control logic is based on a PID algorithm allowing either the direct command of the pulsation level with a continuous monitoring and a potential limit setting of the NOx emission level or vice versa. The gas turbine pulsations and emissions are modelled using Gaussian Processes. - Gaussian Processes are stochastic processes related to Neural Networks that can approximate arbitrary functions. Based on measured gas turbine data they can be implemented in an easy and straightforward manner. The model provides the control system with real time data of the outputs resulting from settings of the staging ratio that is the actuating variable of the system. A model based control concept can significantly alleviate the effects of time delays in the system. The model based control concept allows for fast adaptation of the burner group staging ratio during static and transient operations to achieve an optimum of the pulsation and emission levels. During tests the model based control concept gave good results and proved to be robust even at high disturbance levels.

Combustion Oscillation Monitoring Using Flame Ionization in a Turbulent Premixed Combustor

2006 ◽  
Vol 129 (2) ◽  
pp. 352-357 ◽  
Author(s):  
B. T. Chorpening ◽  
J. D. Thornton ◽  
E. D. Huckaby ◽  
K. J. Benson
Keyword(s):  
Standard Deviation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Dynamic Pressure ◽  
Pressure Oscillation ◽  
Chamber Pressure ◽  
Ion Distribution ◽  
Combustion Dynamics ◽  
Gas Turbine Combustors ◽  
Flame Ionization

To achieve very low NOx emission levels, lean-premixed gas turbine combustors have been commercially implemented that operate near the fuel-lean flame extinction limit. Near the lean limit, however, flashback, lean blow off, and combustion dynamics have appeared as problems during operation. To help address these operational problems, a combustion control and diagnostics sensor (CCADS) for gas turbine combustors is being developed. CCADS uses the electrical properties of the flame to detect key events and monitor critical operating parameters within the combustor. Previous development efforts have shown the capability of CCADS to monitor flashback and equivalence ratio. Recent work has focused on detecting and measuring combustion instabilities. A highly instrumented atmospheric combustor has been used to measure the pressure oscillations in the combustor, the OH emission, and the flame ion field at the premix injector outlet and along the walls of the combustor. This instrumentation allows examination of the downstream extent of the combustion field using both the OH emission and the corresponding electron and ion distribution near the walls of the combustor. In most cases, the strongest pressure oscillation dominates the frequency behavior of the OH emission and the flame ion signals. Using this highly instrumented combustor, tests were run over a matrix of equivalence ratios from 0.6 to 0.8, with an inlet reference velocity of 25m∕s(82ft∕s). The acoustics of the fuel system for the combustor were tuned using an active-passive technique with an adjustable quarter-wave resonator. Although several statistics were investigated for correlation with the dynamic pressure in the combustor, the best correlation was found with the standard deviation of the guard current. The data show a monotonic relationship between the standard deviation of the guard current (the current through the flame at the premix injector outlet) and the standard deviation of the chamber pressure. Therefore, the relationship between the standard deviation of the guard current and the standard deviation of the pressure is the most promising for monitoring the dynamic pressure of the combustor using the flame ionization signal. This addition to the capabilities of CCADS would allow for dynamic pressure monitoring on commercial gas turbines without a pressure transducer.

Scaling of Stability Limits in Lean-Premixed Gas Turbine Combustors

2004 ◽  
Author(s):  
Martin Lohrmann ◽  
Horst Bu¨chner
Keyword(s):  
Gas Turbine ◽  
Scaling Laws ◽  
Transfer Functions ◽  
Burning Velocity ◽  
Phase Reaction ◽  
Combustion Instabilities ◽  
Burner Exit ◽  
Periodic Disturbances ◽  
Lean Premixed ◽  
Coherent Vortex

The prediction and the systematic suppression of self-sustained combustion instabilities in combustors for gas turbine applications still suffer from incomplete physical understanding of the feedback mechanisms and lack of experimental data of the dynamic flame characteristics of Lean-Premixed swirl flames. Hence, the experimental determination of the flame transfer functions of LP swirl flames was achieved using a mixing unit to generate a time-independent and spatial homogeneous mixture of natural gas and combustion air at the burner exit. The determined LP flame dynamics are strongly affected by the formation and in-phase reaction of coherent vortex structures, well known as drivers of combustion instabilities, that have been visualized with an phase-correlated imaging technique. The results discussed in this paper lead to a basic understanding of the frequency-dependent dynamics of LP swirl flames on periodic disturbances and especially, of the influence of the preheating temperature and the air equivalence ratio on the amplitude responses and phase angle functions. Based on the measurements and theoretical considerations concerning the burning velocity of steady-state premixed flames a physical model and — derived from it — scaling laws for the prediction of unstable operation modes in dependence of main operation parameters of the flame were formulated and validated by measurements.

Effects of Unmixedness in Piloted-Lean Premixed Gas-Turbine Combustors

1998 ◽  
Vol 14 (6) ◽  
pp. 967-973 ◽  
Author(s):  
J. C. Barnes ◽  
A. M. Mellor
Keyword(s):  
Gas Turbine ◽  
Gas Turbine Combustors ◽  
Lean Premixed

High Frequency Thermoacoustic Modulation Mechanisms in Swirl-Stabilized Gas Turbine Combustors: Part One — Experimental Investigation of Local Flame Response

2016 ◽  
Author(s):  
Frederik M. Berger ◽  
Tobias Hummel ◽  
Michael Hertweck ◽  
Jan Kaufmann ◽  
Bruno Schuermans ◽  
...  
Keyword(s):  
Heat Release ◽  
Gas Turbine ◽  
High Frequency ◽  
Transfer Functions ◽  
Temporal Dynamics ◽  
Dynamic Pressure ◽  
Radon Transforms ◽  
Gas Turbine Combustors ◽  
High Modulation ◽  
The Impact

This paper presents the experimental approach for determination and validation of non-compact flame transfer functions of high frequency, transverse combustion instabilities observed in a generic lean premixed gas turbine combustor. The established non-compact transfer functions describe the interaction of the flame’s heat release with the acoustics locally, which is necessary due to the respective length scales being of the same order of magnitude. Spatio-temporal dynamics of the flame are measured by imaging the OH* chemiluminescence signal, phase-locked to the dynamic pressure at the combustor’s front plate. Radon transforms provide a local insight into the flame’s modulated reaction zone. Applied to different burner configurations, the impact of the unsteady heat release distribution on the thermoacoustic driving potential, as well as distinct flame regions that exhibit high modulation intensity are revealed. Utilizing these spatially distributed transfer functions within thermoacoustic analysis tools (addressed in this joint publication’s part two) allows then to predict transverse linear stability of gas turbine combustors.

Scaling Thermo-Acoustic Characteristics of LP and LPP Swirl Flames

2007 ◽  
Author(s):  
Michael Russ ◽  
Axel Meyer ◽  
Horst Bu¨chner
Keyword(s):  
Gas Turbine ◽  
Transfer Functions ◽  
Burning Velocity ◽  
Pollutant Emissions ◽  
Operating Pressure ◽  
Swirl Number ◽  
Frequency Dependent ◽  
Lean Premixed ◽  
Operation Parameters ◽  
Main Operation

One of the main objectives of combustion research in field of gas turbine application during the last decades was and still is the reduction of pollutant emissions. The most promising technology to reduce these pollutants turned out to be Lean Premixed (LP) and Lean Premixed Pre-Vaporized (LPP) combustion. However, serious problems concerning combustion-driven instabilities occurred with the implementation of the LP/LPP-concept. Today, prediction and systematic suppression of self-sustained combustion instabilities is an issue still unsolved, due to incomplete understanding of the physical feedback mechanism and the lack of models for dynamic flame response, i.e. frequency dependent characteristics of LP/LPP swirl flames. In that context, the purpose of the current paper is the establishment of a physical model to describe frequency dependent flame dynamics concerning burning velocity of steady-state premixed flames. Derived from that basic understanding, scaling laws for the prediction of unstable operation conditions will be established in dependence on main operation parameters such as thermal load, mixture temperature, air equivalence ratio and especially of fuel and operating pressure. Therefore, a new swirl-burner has been designed, offering the feasibility to choose the type of fuel, to adjust the swirl number for main and pilot burner and the burner exit geometry steplessly and to vary preheating temperatures, air equivalence ratios and thermal loads in a range of industrial relevance for gas turbine applications. To establish a periodical modulation of the mixture mass flow of the main L(P)P flame at the burner outlet sinusoidally in-time with well-defined frequencies and amplitudes, a pulsating unit was used. Using a mixing/ pre-vaporizing unit to create a time-independent and spatial homogeneous mixture of natural gas/ kerosene vapor and combustion air at the burner outlet, flame transfer functions of LP- and LPP swirl flames depending on main operating parameters were determined. The discussed results then lead to stability map for a given combustion system depending on the main operation parameters based on the knowledge of only one fully-described parameter combination leading to an instable condition. Based on this scaling procedure and confirmed by further experimental work the prediction of stability limits depending especially on the type of fuel, the swirl number and the operating pressure will be possible.

Sign in / Sign up

Export Citation Format

Share Document