Synchronization During Multi-Mode Thermoacoustic Oscillations in a Liquid-Fueled Gas Turbine Combustor at Elevated Pressure

2019 ◽  
Author(s):  
Mitchell L. Passarelli ◽  
J. D. Maxim Cirtwill ◽  
Timothy Wabel ◽  
Adam M. Steinberg ◽  
A. J. Wickersham
Keyword(s):  
Heat Release ◽  
Gas Turbine ◽  
Heat Release Rate ◽  
Release Rate ◽  
High Speed ◽  
Elevated Pressure ◽  
Fuel Injector ◽  
Frequency Pulling ◽  
Industrial Gas Turbine ◽  
Thermoacoustic Oscillations

Abstract This paper analyzes intermittent self-excited thermoacoustic oscillations in which the pressure (P′) and heat release rate (q̇′) fluctuations are harmonically coupled. That is to say, P′ and q̇′ do not oscillate at the same frequencies, but rather at frequencies in integer ratios. Thus, this system represents a case dominated by nonlinear cross-mode coupling. The measurements were obtained in an optically-accessible combustor equipped with an industrial gas turbine fuel injector operating with liquid fuel under partially-premixed conditions at elevated pressure. High-speed chemiluminescence (CL) imaging of OH* was used as an indicator of the heat release rate. The data was processed using spectral proper orthogonal decomposition (SPOD) to isolate the dominant heat release and pressure modes. Synchronization theory was used to determine when the modes are coupled and how their interaction manifests in the measurements, particularly how it relates to the observed intermittency. The results show three distinct intervals of synchronized oscillation shared by all the mode pairs analyzed. The first interval exhibits the same characteristics as a pair of noisy, phase-locked self-oscillators, with phase-slipping and frequency-pulling. While the behaviour of the second interval differs among mode pairs, strong frequency-pulling is observed during the third interval for all pairs.

Dynamics and mechanisms of pressure, heat release rate, and fuel spray coupling during intermittent thermoacoustic oscillations in a model aeronautical combustor at elevated pressure

2017 ◽  
Vol 185 ◽  
pp. 319-334 ◽  
Author(s):  
Sina Kheirkhah ◽  
J. D. Maxim Cirtwill ◽  
Pankaj Saini ◽  
Krishna Venkatesan ◽  
Adam M. Steinberg
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Elevated Pressure ◽  
Fuel Spray ◽  
Thermoacoustic Oscillations

4D Measurements and Analysis of Heat Release Rate in a Model Gas Turbine Combustor

2020 ◽  
Author(s):  
Rongxiao Dong ◽  
Qingchun Lei ◽  
Yeqing Chi ◽  
Qun Zhang ◽  
Wei Fan
Keyword(s):  
Heat Release ◽  
Gas Turbine ◽  
Surface Area ◽  
Heat Release Rate ◽  
Release Rate ◽  
Flame Surface ◽  
Global Instability ◽  
Gas Turbine Combustor ◽  
Model Gas Turbine Combustor ◽  
Edge Contours

Abstract Time-resolved volumetric measurements (4D measurements) were performed to study the heat release rate characteristics in a model gas turbine combustor at 10 kHz. For this purpose, a high-speed camera combined with an image intensifier and a set of customized fiber probes were employed to continuously capture the CH* chemiluminescence signals from nine different viewing angles. Based on the measurements, the computed tomography program was performed to reconstruct the shot-to-shot 3D distributions of the CH* signals. Specific focuses have been made to demonstrate the capabilities of the current tomographic technique in applications of a realistic combustor, in which the full optical access was usually not available for every viewing angle. The results showed that the 3D reconstruction can successfully retrieval the flame edge contours rather than the signal intensity. The flame surface area was then calculated based on the reconstructed flame edge contours and used to infer the heat release rate. The fluctuation of global/local flame surface area indicated that there existed distinct difference between the global instability and local instabilities at various locations in the non-symmetric combustor. The global instability appears to be an integration of those local instabilities.

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.

scholarly journals On the Local Heat Release Rate in a Combustion Chamber of Gas Turbine

1962 ◽  
Vol 5 (19) ◽  
pp. 505-510
Author(s):  
Takashi SATO ◽  
Itaru MICHIYOSHI ◽  
Ryuichi MATSUMOTO
Keyword(s):  
Heat Release ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Heat Release Rate ◽  
Release Rate ◽  
Local Heat

Determination of the Start and End of Combustion in a Direct Injection Diesel Engine Using the Apparent Heat Release Rate

2017 ◽  
Author(s):  
Joseph Gerard T. Reyes ◽  
Edwin N. Quiros
Keyword(s):  
Diesel Engine ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Direct Injection ◽  
Injection Timing ◽  
Fuel Injector ◽  
Direct Injection Diesel Engine ◽  
Crank Angle ◽  
Start Of Combustion

The combustion duration in an internal combustion engine is the period bounded by the engine crank angles known as the start of combustion (SOC) and end of combustion (EOC), respectively. This period is essential in analysis of combustion for the such as the production of exhaust emissions. For compression-ignition engines, such as diesel engines, several approaches were developed in order to approximate the crank angle for the start of combustion. These approaches utilized the curves of measured in-cylinder pressures and determining by inspection the crank angle where the slope is steep following a minimum value, indicating that combustion has begun. These pressure data may also be utilized together with the corresponding cylinder volumes to generate the apparent heat release rate (AHRR), which shows the trend of heat transfer of the gases enclosed in the engine cylinder. The start of combustion is then determined at the point where the value of the AHRR is minimum and followed by a rapid increase in value, whereas the EOC is at the crank angle where the AHRR attains a flat slope prior to the exhaust stroke of the engine. To verify the location of the SOC, injection line pressures and fuel injection timing are also used. This method was applied in an engine test bench using a four-cylinder common-rail direct injection diesel engine with a pressure transducer installed in the first cylinder. Injector line pressures and fuel injector voltage signals per engine cycle were also recorded and plotted. By analyzing the trends of this curves in line with the generated AHRR curves, the SOC may be readily determined.

Effect of cetane number improver on heat release rate and emissions of high speed diesel engine fueled with ethanol–diesel blend fuel

Fuel ◽  
2004 ◽  
Vol 83 (14-15) ◽  
pp. 2013-2020 ◽  
Author(s):  
Lü Xing-cai ◽  
Yang Jian-guang ◽  
Zhang Wu-gao ◽  
Huang Zhen
Keyword(s):  
Diesel Engine ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
High Speed ◽  
Cetane Number ◽  
High Speed Diesel ◽  
Blend Fuel

Flame Area Fluctuation Measurements in Velocity-Forced Premixed Gas Turbine Flames

2015 ◽  
Author(s):  
Alexander J. De Rosa ◽  
Janith Samarasinghe ◽  
Stephen J. Peluso ◽  
Bryan D. Quay ◽  
Domenic A. Santavicca
Keyword(s):  
Heat Release ◽  
Gas Turbine ◽  
Heat Release Rate ◽  
Release Rate ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Small Scale ◽  
Flame Velocity ◽  
Unstable Combustion

Fluctuations in the heat release rate that occur during unstable combustion in lean premixed gas turbine combustors can be attributed to velocity and equivalence ratio fluctuations. For a fully premixed flame, velocity fluctuations affect the heat release rate primarily by inducing changes in the flame area. In this paper, a technique to analyze changes in flame area using chemiluminescence-based flame images is presented. The technique decomposes the flame area into separate components which characterize the relative contributions of area fluctuations in the large scale structure and the small scale wrinkling of the flame. The fluctuation in the wrinkled area of the flame which forms the flame brush is seen to dominate its response in the majority of cases tested. Analysis of the flame area associated with the large scale structure of the flame resolves convective perturbations that move along the mean flame position. Results are presented that demonstrate the application of this technique to both single-nozzle and multi-nozzle flames.

The Effects of Forcing Direction on the Flame Transfer Function of a Lean-Burn Spray Flame

2021 ◽  
Author(s):  
Nicholas C. W. Treleaven ◽  
André Fischer ◽  
Claus Lahiri ◽  
Max Staufer ◽  
Andrew Garmory ◽  
...  
Keyword(s):  
Transfer Function ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Fuel Injector ◽  
Lean Burn ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Good Reproduction ◽  
Small Change

Abstract The flame transfer function (FTF) of an industrial lean-burn fuel injector has been computed using large eddy simulation (LES) and compared to experimental measurements using the multi-microphone technique and OH* measurements. The flame transfer function relates the fluctuations of heat release in the combustion chamber to fluctuations of airflow through the fuel injector and is a critical part of thermoacoustic analysis of combustion systems. The multi-microphone method derives the FTF by forcing the flame acoustically, alternating from the upstream and downstream side. Simulations emulating this methodology have been completed using compressible large eddy simulations (LES). These simulations are also used to derive an FTF by measuring the fluctuations of mass flow rate and heat release rate directly which reduces the number of simulations per frequency to one, significantly reducing the simulation cost. Simulations acoustically forced from downstream are shown to result in a lower value of the FTF gain than simulations forced from upstream with a small change in phase, this is shown to be consistent with theory. Through using a slightly different definition of the FTF, this is also shown to be consistent with measurements of the heat release rate using OH* chemiluminescence however these results are inconsistent with the multi-microphone method result. The discrepancy comes from not having an accurate measurement of the acoustic impedance at the exit plane of the injector and from certain convective phenomena that alter the downstream velocity and pressure field with respect to the purely acoustic signal. All simulations show a lower gain in the FTF than the experiments but with good reproduction of phase. Previous work suggests this error is likely due to fluctuations of the fuel spray atomisation process due to the acoustic forcing which is not modelled in this study.

Adjoint Methods for Elimination of Thermoacoustic Oscillations in a Model Annular Combustor via Small Geometry Modifications

2018 ◽  
Author(s):  
José G. Aguilar ◽  
Matthew P. Juniper
Keyword(s):  
Sensitivity Analysis ◽  
Time Delay ◽  
Heat Release ◽  
Combustion Chamber ◽  
Heat Release Rate ◽  
Release Rate ◽  
Gas Turbines ◽  
Acoustic Pressure ◽  
Annular Combustor ◽  
Thermoacoustic Oscillations

In gas turbines, thermoacoustic oscillations grow if moments of high fluctuating heat release rate coincide with moments of high acoustic pressure. The phase between the heat release rate and the acoustic pressure depends strongly on the flame behaviour (specifically the time delay) and on the acoustic period. This makes the growth rate of thermoacoustic oscillations exceedingly sensitive to small changes in the acoustic boundary conditions, geometry changes, and the flame time delay. In this paper, adjoint-based sensitivity analysis is applied to a thermoacoustic network model of an annular combustor. This reveals how each eigenvalue is affected by every parameter of the system. This information is combined with an optimization algorithm in order to stabilize all thermoacoustic modes of the combustor by making only small changes to the geometry. The final configuration has a larger plenum area, a smaller premix duct area and a larger combustion chamber volume. All changes are less than 6% of the original values. The technique is readily scalable to more complex models and geometries and the inclusion of further constraints, such that the combustion chamber itself should not change. This demonstrates why adjoint-based sensitivity analysis and optimization could become an indispensible tool for the design of thermoacoustically-stable combustors.

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