Thermoacoustic Behaviour of a Hydrogen Micromix Aviation Gas Turbine Combustor Under Typical Flight Conditions

2021 ◽  
Author(s):  
David Abbot ◽  
Alessandro Giannotta ◽  
Xiaoxiao Sun ◽  
Pierre Gauthier ◽  
Vishal Sethi
Keyword(s):  
Time Delay ◽  
System Design ◽  
Gas Turbines ◽  
Characteristic Time ◽  
Diffusion Flames ◽  
Combustion System ◽  
Low Frequencies ◽  
Combustion Dynamics ◽  
Thermoacoustic Instabilities ◽  
Longitudinal Modes

Abstract Hydrogen micromix is a candidate combustion technology for hydrogen aviation gas turbines. The introduction and development of new combustion technologies always carries the risk of suffering from damaging high amplitude thermoacoustic pressure oscillations. This was a particular problem with the introduction of lean premixed combustion systems to land based power generation gas turbines. There is limited published information on the thermoacoustic behaviour of such hydrogen micromix combustors. Diffusion flames are less prone to flashback and autoignition problems than premixed flames and conventional diffusion flames are less prone to combustion dynamics issues. However, with the high laminar flame speed of hydrogen, lean fuel air ratio (FAR) and very compact flames, the risk of combustion dynamics for micromix flames should not be neglected and a comparison of the likely thermoacoustic behaviour of micromix combustors and kerosene fueled aviation combustors would inform the early stage design of engine realistic micromix combustors. This study develops a micromix combustor concept suitable for a modern three spool, high bypass ratio engine and derives the acoustic Flame Transfer Function (FTF) at typical engine operating conditions for top of climb, take-off, cruise, and end of runway. The FTF is derived using CFD and FTF models based on a characteristic flame delay. The relative thermoacoustic behaviour for the four conditions is assessed using a low order acoustic network code. The comparisons suggest that the risk of thermoacoustic instabilities associated with longitudinal waves at low frequencies (below 1kHz) is small, but that higher frequency longitudinal modes could be excited. The sensitivity of the combustor thermoacoustic behaviour to key combustor dimensions and characteristic time delay is also investigated and suggests that higher frequency longitudinal modes can be significantly influenced by combustion system design. The characteristic time delay and thus FTF for a Lean Premixed Prevapourised (LPP) kerosene combustor is derived from information in the literature and the thermoacoustic behaviour of the micromix combustor relative to that of this kerosene combustor is determined using the same low order modelling approach. The comparison suggests that the micromix combustor is much less likely to produce thermoacoustic instabilities at low frequencies (below 1kHz), than the LPP combustor even though the risk in the LPP combustor is small. It is encouraging that this simple approach used in a preliminary design suggests that the micromix combustor has lower risk at low frequency than a kerosene combustor and that the risk of higher frequency longitudinal modes can be reduced by appropriate combustion system design. However, more detailed design, more rigorous thermoacoustic analysis and experimental validation are needed to confirm this.

Numerical Procedure for the Investigation of Combustion Dynamics in Industrial Gas Turbines: LES, RANS and Thermoacoustics

2015 ◽  
Author(s):  
Luca Rofi ◽  
Giovanni Campa ◽  
Vyacheslav Anisimov ◽  
Federico Daccá ◽  
Edoardo Bertolotto ◽  
...  
Keyword(s):  
Experimental Data ◽  
Gas Turbines ◽  
Numerical Procedure ◽  
Combustion System ◽  
Combustion Dynamics ◽  
Eddy Simulation ◽  
Experimental Apparatus ◽  
Industrial Gas Turbines ◽  
Computationally Intensive ◽  
Acoustic Instabilities

The necessity for a combustion system to work with premixed flames and its capability to cope with rapid load variations avoiding the occurrence of thermo-acoustic instabilities, has led to investigate the complex dynamic phenomena that occur during combustion. Thanks to numerical simulations it is possible to examine these complex mechanisms getting useful information to optimize the combustion system. The aim of this work is to describe a numerical procedure developed in Ansaldo Energia for the investigation of combustion dynamics occurring in Ansaldo Energia gas turbines. In this paper, firstly the experimental apparatus of a full scale atmospheric test rig equipped with Ansaldo Energia burner is described. Secondly, the flame behavior is studied by means of a Large Eddy Simulation (LES). Once the LES has reached a statistically stationary state, a forcing is added to the system to compute the Flame Transfer Function (FTF), in terms of amplitude n and delay time τ, related to initial phases of humming. Thirdly, the forced flame simulations are used as the input of an Helmholtz solver to analyze the acoustic behavior of the system, which is then compared to experimental data. Finally, to evaluate the feasibility of a less computationally intensive approach, a RANS simulation of the same configuration is described and the results are transferred to FEM (Finite Element Method) Helmholtz solver: a comparison between the LES approach and the RANS approach is carried out with reference to the experimental data.

Staged Combustion System for Improved Emissions Operability and Flexibility for 7HA Class Heavy Duty Gas Turbine Engine

2017 ◽  
Author(s):  
Hasan Karim ◽  
Jayaprakash Natarajan ◽  
Venkat Narra ◽  
Jun Cai ◽  
Shreekrishna Rao ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Firing Temperature ◽  
Gas Turbines ◽  
Test Facility ◽  
Engine Test ◽  
Combustion System ◽  
Operational Flexibility ◽  
Staged Combustion ◽  
Combustion Dynamics ◽  
Gas Turbine Combustion

Driven by global warming, a relentless march towards increased fuel efficiency has resulted in increased firing temperature for HA-class engines without an increase in baseload emissions. Moreover, emissions compliance for CO, NOx, and unburned hydrocarbons are desired over increased range in gas turbine load. In addition, exceptional gas turbine operational flexibility is desired to address potential intermittency due to the penetration of renewables in the electrical grid. Staged/sequential combustion is a state of the technology to provide operational flexibility and reduced emissions in power generation gas turbines. GE Power’s 7HA-class gas turbine combustion system combines GE’s proven DLN-2.6+ combustion technology, that has run reliably for over 1.3 million fired hours across more than eighty 9FA.03, 9F.05 & 7FA gas turbine engines, with an axially fuel staged system (AFS). Axially staging combustion to two zones allows for increased firing temperature at baseload (while maintaining the same NOx level) by operating the later/second stage hotter than the first/primary stage. During low load operation as the gas turbine firing temperature is reduced, percentage fuel split in the staged fuel system can either be reduced significantly or turned off and thereby keeping the overall combustion system into emissions compliance over a wider range of firing temperatures. This paper presents both the development testing of the staged combustion in the FA and HA class gas turbine combustion system rigs at GE Power’s Gas Turbine Technology Laboratory and the validation testing of staged combustion system for the 7HA.01 engine completed during Spring 2016 at GE Power’s engine test facility in Greenville, SC. The paper also discusses the significant simplification of operational principle and flexibility of startup, loading and baseload operation of the 7HA combustion system. Discussion of engine test results will show how axial fuel staging was utilized to demonstrate emissions compliance ( NOx (15% O2) < 25 ppm; CO < 9 ppm), operation from 14% load to 100% load with low combustion dynamics and also to enable wide wobbe capability, which is a normalized measure of fuel flexibility.

scholarly journals Combustion-System Design for Industrial Gas Turbines

1964 ◽  
Author(s):  
R. E. Strong ◽  
C. E. Hussey
Keyword(s):  
System Design ◽  
Gas Turbines ◽  
Field Tests ◽  
Combustion System ◽  
Discharge Temperature ◽  
Industrial Gas Turbines

Some of the problems encountered in combustion-system design are discussed with particular attention to combustor discharge-temperature patterns. The results of extensive laboratory and field tests that culminated in improved temperature patterns are presented.

LNG Interchangeability in Land Based Gas Turbines: The Siemens Approach

2007 ◽  
Author(s):  
Pratyush Nag ◽  
Khalil Abou-Jaoude ◽  
Steve Mumford ◽  
Jianfan Wu ◽  
Matthew LaGrow ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Warning System ◽  
Fuel Composition ◽  
Combustion System ◽  
Fuel Gas ◽  
Combustion Dynamics ◽  
Site Specific ◽  
Fuel Characteristics ◽  
Combustion Systems

Liquefied Natural Gas (LNG) from offshore reserves is expected to expand its role in supplementing US natural gas supplies. The quality and hydrocarbon contents of the natural gas imported from these international sources, frequently differs from the compositions of domestic natural gas. With the range of variations in fuel characteristics known to exist with offshore LNG, use of this LNG in gas turbine engines could violate applicable fuel specifications, and lead to operational issues such as, but not limited to, combustion dynamics, flashback, increased emissions, or decreased component life. Another potential issue for gas turbines generating power is that rapid changes in the fuel characteristics that may occur when blending imported and domestic gas, may lead to substantial fluctuations in power output. Fuel flexibility is dominantly tied to the combustion system design. Conventional diffusion flame combustion systems are more tolerant of wide variations in fuel compositions but they are limited by their emission levels. The more advanced premixed flame combustors, the Dry Low NOxs (DLN) and Ultra Low NOx (ULN) combustion systems have significantly better performances in terms of emissions but they are also more sensitive to changes in the fuel composition and characteristics. Siemens has performed test campaigns with commercially operating engines and high pressure combustion test rigs to evaluate their commercially available combustion system configurations for LNG applicability. From these test campaigns, Siemens has defined the set of combustion hardware modifications which is robust to changes in fuel composition within the tested limits. Along with the said combustion hardware upgrade, Siemens has also designed an Integrated Fuel Gas Characterization (IFGC) system (Patent Pending). This IFGC system acts like an early warning system and feeds forward signals into the plant control system. Depending on the changes in the properties of the incoming fuel, the IFGC system is designed to adjust the engine tuning settings to compensate for these dynamic changes in the fuel. Customer implementation of the required hardware as well as associated site-specific engineering will mitigate the operational and emissions risk associated with the fuel changes. Overall, it is Siemens recommendation that LNG type fuels will be acceptable to be used in Siemens Gas Turbines with the preferred combustion hardware in place along with the Integrated Fuel Gas Characterization System. A site specific evaluation would be required to determine the optimal system depending on the expected fuels that the unit would be operating with, along with the emissions permit levels associated with the site.

Application of Continuous Combustion Dynamics Monitoring on Large Industrial Gas Turbines

2004 ◽  
Author(s):  
Jesse Sewell ◽  
Pete Sobieski ◽  
Craig Beers
Keyword(s):  
Combustion Chamber ◽  
Gas Turbines ◽  
Continuous Monitoring ◽  
Combustion System ◽  
Combustion Chambers ◽  
Combustion Dynamics ◽  
Spectral Signatures ◽  
Industrial Gas Turbines ◽  
Transition Piece ◽  
Component Failures

This paper presents results from continuous monitoring of combustion dynamics and its application in determining the health of combustion system hardware. A number of 180 MW class large industrial gas turbines operating on natural gas have been instrumented with a continuous Combustor Dynamics Monitoring (CDM) for each combustion chamber. Tuning considerations for emissions, stability and extended combustion parts life is discussed. Physical inspection of engine hardware is correlated with spectral and supervisory engine data to determine signatures in the combustion chambers that represent damaged or failing hardware. This methodology can also be used to identify potentially harmful operational profiles. Spectral examples of a pilot nozzle and transition piece failures are presented. Monitoring and recognizing the differences in spectral signatures associated with stability and component failures suggests better understanding of combustion dynamics contribution to combustor parts wear and reduction in downstream damage.

Impact of Fuel Supply Impedance on Combustion Stability of Gas Turbines

2008 ◽  
Author(s):  
Andreas Huber ◽  
Wolfgang Polifke
Keyword(s):  
Gas Turbines ◽  
Equivalence Ratio ◽  
Cfd Simulation ◽  
Transfer Functions ◽  
Combustion Stability ◽  
Reacting Flow ◽  
Efficient Manner ◽  
Combustion Dynamics ◽  
Thermoacoustic Instabilities ◽  
Fuel Supply

In the development of gas turbines the prevention of thermoacoustic instabilities plays an important role. The present study analyzes the influence of the acoustic impedance of the fuel supply system on combustion stability in a generic configuration representative of practical lean-premix combustors. Transient Computational Fluid Dynamics (CFD) of turbulent reacting flow and system identification (SI) are combined to obtain a description of the combustion dynamics in terms of two flame transfer functions, which describe the response of heat release rate to fluctuations of velocity and equivalence ratio, respectively. In this way, the mixing and transport of the fuel from the injector to the flame, the kinematic response of the flame to upstream flow fluctuations, and combined effects like the perturbation of flame speed and position due to equivalence ratio perturbations are all captured. The flame transfer functions obtained are combined with a network model for the system acoustics in such a way that results from a single CFD simulation can be used to investigate a wide variety of combustor and fuel supply configurations in a quantitative and very efficient manner. It is demonstrated that a change of the fuel supply impedance can significantly influence the amplitude of equivalence ratio fluctuations as well as the relative phase of the two transfer functions, and thereby provide a means for control of combustion instabilities.

Burner Development for Flexible Engine Operation of the Newest Siemens Gas Turbines

2003 ◽  
Author(s):  
Bernd Prade ◽  
Ju¨rgen Meisl ◽  
Peter Berenbrink ◽  
Holger Streb ◽  
Stefan Hoffmann
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Liquid Fuel ◽  
Fuel Quality ◽  
Nox Emissions ◽  
Combustion System ◽  
Engine Operation ◽  
Water Emulsion ◽  
Combustion Dynamics ◽  
Wide Range

The newest Siemens gas turbine family has already been well received by the market. Nevertheless, the market drives continuing development of the family and the combustion system. Central focus is put on further increasing reliability and component lifetime and on increased inspection cycles, as well as increasing the engine power output and efficiency, which is directly linked to higher turbine inlet temperatures. Increasing attention, however, is given to the flexibility concerning fuel quality and according fluctuations. Additionally, more and more strict emission requirements must be considered. This paper especially reports on demonstration of the capability of the Siemens gas turbines with an annular combustion system to fulfil the requirements for the highest operational flexibility. Thus, the combustion system has been tested and qualified for the highest operating flexibility with special fuel requirements such as burning Naphtha, Light Oil #2 and Natural gas with an extremely wide range of heating values as well. Also special operation modes such as fuel changeover, fastest load changes for island grid operation, frequency response and load rejection require this highly flexible combustion system without any hardware exchange. In different frames when fired with natural gas, base load is reached with the NOx emissions ranging well below 25 ppmvd, confirming the high potential of this advanced hybrid burner. In liquid fuel operation, dry NOx emissions of 75ppmvd were demonstrated but by injecting fuel / water emulsion NOx emissions were reduced to below 42 ppmvd with different liquid fuel qualities. Combustion dynamics, unburned Hydrocarbons, CO and soot emissions remained always below the required limits.

Investigation Into Advanced Combustion System Health Monitoring

2019 ◽  
Author(s):  
David Noble ◽  
Leonard Angello ◽  
Scott Sheppard ◽  
Jared Kee ◽  
Benjamin Emerson ◽  
...  
Keyword(s):  
Real Time ◽  
Health Monitoring ◽  
Gas Turbines ◽  
Dynamic Pressure ◽  
Health Indicators ◽  
Combustion System ◽  
Additional Time ◽  
Combustion Dynamics ◽  
System Health Monitoring ◽  
Diagnostic Work

Abstract Dry, low NOx gas turbines are extremely complex machines that are heavily relied upon in the power industry as baseload, cycling, and/or peaking units. These low-emission gas turbines present potential maintenance and monitoring challenges due to the intrinsically harsh pressure and temperature environments, which make diagnostics and prognostic capabilities extremely difficult. One such challenge involves understanding and interpreting combustion dynamics data. This paper focuses on gas turbine combustion dynamics monitoring (CDM) and describes an algorithm to determine combustor health based upon dynamic pressure. The ongoing CDM and diagnostic work has progressed from taking basic binned FFT data and transforming this data to statistically-based health indicators that can be continuously calculated to determine combustion system anomalies. These anomalies can be detected hours, days, and sometimes even weeks before passive CDM alarm levels are reached, thus, giving additional time to plan for shutdown, inspection, and repair. The paper will discuss real-time observed successes and challenges associated with combustor health monitoring, including sensor health determination and factors associated with the non-linear nature of combustion dynamics. Overall, this work is helping to better alleviate the user’s “black box” perspective of combustion dynamics monitoring systems through automated, real-time interpretation for combustion system health for can annular gas turbines.

Numerical Investigation of Potential Cause of Instabilities in a Hydrogen Micromix Injector Array

2021 ◽  
Author(s):  
Xiaoxiao Sun ◽  
David Abbott ◽  
Abhay Vir Singh ◽  
Pierre Gauthier ◽  
Bobby Sethi
Keyword(s):  
Boundary Conditions ◽  
High Frequency ◽  
Gas Turbines ◽  
Diffusion Flames ◽  
Laminar Flame ◽  
Early Stage ◽  
Flammability Limits ◽  
Small Diffusion ◽  
Combustion Dynamics ◽  
Rans Simulations

Abstract Hydrogen micromix combustion is a promising concept to reduce the environmental impact of both aero and land-based gas turbines by delivering carbon-free and ultra-low-NOx combustion. The high-reactivity and wide flammability limits of hydrogen in a micromix combustor can produce short and small diffusion flames at lean overall equivalence ratios. There is limited published information on the instabilities of such hydrogen micromix combustors. Diffusion flames are less prone to flashback and autoignition problems than premixed flames as well as combustion dynamics issues. However, with the high laminar flame speed of hydrogen, lean fuel air ratio (FAR) and very compact flames, the risk of combustion dynamics for micromix flames should not be neglected. In addition, the multi-segment array arrangement of the injectors could result in both potential causes and possible solutions to the instabilities within the combustor. This paper employs numerical simulations to investigate potential sources of instabilities in micromix flames by modelling an extended array of injectors, represented by either single or multiple injectors with appropriate boundary conditions at elevated pressure and temperature. Both RANS and LES simulations were performed and used to derive the Flame Transfer Function (FTF) of the micromix flames to inform lower order thermoacoustic modelling of micromix combustion. LES simulations indicate that the gain of the FTF is lower than predicted from the RANS simulations indicating a lower risk of high frequency thermoacoustic issues than suggested by RANS. When LES simulations are conducted for certain representative configurations it is observed that there are persistent high-frequency instabilities due to the interaction of the flames. This phenomenon is not observed when only a single injector is modelled. LES simulations for two injectors are conducted with various geometries and radial boundary conditions to identify the cause of the instabilities. It is concluded that the observed high-frequency instabilities are related to aerodynamic jet instabilities enhanced by both aerodynamic and acoustic feedback and key geometric features affecting the occurrence of the instabilities are identified. Only transient simulations such as LES are able to capture such effects and RANS simulations typically used in early stage design will not identify this issue.

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