Experimental Analysis of Confinement and Swirl Effects on Premixed CH4-H2 Flame Behavior in a Pressurized Generic Swirl Burner

2017 ◽  
Author(s):  
Jon Runyon ◽  
Richard Marsh ◽  
Daniel Pugh ◽  
Philip Bowen ◽  
Anthony Giles ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Kinetic Modelling ◽  
Dynamic Pressure ◽  
Flame Stabilization ◽  
Combustion Noise ◽  
Combustion Stability ◽  
Acoustic Response ◽  
Swirl Burner ◽  
Swirl Number

The introduction of hydrogen into natural gas systems for environmental benefit presents potential operational issues for gas turbine combustion and power generation applications; in particular acceptable blending concentrations are still widely debated. The use of a generic swirl burner under conditions pertinent to a gas turbine combustor is therefore advantageous to (i) provide evidence of potential design modifications to inform future gas turbine operation on hydrogen blends and (ii) validate numerical model predictions. Building on a previous experimental combustion database consisting of methane-hydrogen fuel blends under atmospheric and elevated ambient conditions, a new scaled generic swirl burner has been designed for experimental investigation of flame stability and exhaust gas emissions at combustor inlet temperatures to 573 K, pressures to 0.33 MPa, and thermal powers to 126 kW. The geometry downstream of the modular burner is developed further to enable separate investigation under isothermal and combustion conditions of the influence of combustor outlet geometry and the effect of changing geometric swirl number. The burner confinement is modified to include both a cylindrical exit quartz combustion chamber and a conical convergent exit quartz combustion chamber, designed to provide a more representative geometric and acoustic boundary at the combustor outlet. Two inlet geometric swirl numbers of industrial relevance are chosen; namely 0.5 and 0.8. Combustion stability and heat release locations of lean premixed CH4-air and CH4-H2-air combustion are evaluated by a combination of OH planar laser induced fluorescence, OH* chemiluminescence, and dynamic pressure measurements. Changes in flame stabilization location are characterized by the use of an OH* chemiluminescence intensity centroid. Notable upstream flame movement coupled with changes in acoustic response are evident, particularly near the lean operating limit as hydrogen blending shifts lean blowoff of methane flames to lower equivalence ratios with corresponding reduction in NOx emissions. The influence of increased pressure on the lean operating point stability and emissions appear to be small over the range considered, however a power law correlation has been developed for scaling combustion noise amplitudes with inlet pressure and swirl number. Indicators of flame flashback as well as combustor acoustic response are affected considerably when the convergent combustor outlet geometry is deployed. This has been shown to alter the influence of the central recirculation zone as a flame stabilizing coherent flow structure. Chemical kinetic modelling supports the experimental observations that stable burner operation can be achieved with blended methane-hydrogen up to 15% by volume.

Experimental and Analytical Study of the Acoustic Properties of a Gas Turbine Model Combustor With a Choked Nozzle

2015 ◽  
Author(s):  
Marek Mazur ◽  
Wenjie Tao ◽  
Philippe Scouflaire ◽  
Franck Richecoeur ◽  
Sébastien Ducruix
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Dynamic Pressure ◽  
Combustion Noise ◽  
Acoustic Properties ◽  
Chamber Pressure ◽  
Flame Surface ◽  
Experimental Database ◽  
Acoustic Modes ◽  
Cavity System

Combustion is now considered as a non-negligible contributor to gas turbine noise. Combustion noise can be divided into two types: direct combustion noise directly caused by flame surface fluctuations and indirect combustion noise caused by non-homogeneities in the burnt gases, which radiate sound when interacting with the first turbine stages. The aim of the present project is to obtain an extensive experimental database as well as a better understanding of the physical phenomena inside a pressurized combustion chamber with a choked exhaust nozzle. To do so, a pressurized model scale combustor has been developed, containing a tangential admission injector creating a swirling premixed flow. Satisfactory premixing is obtained in the injection device by a porous media. The combustion chamber shows large optical accesses and various ports for pressure and temperature sensors. On the upstream side, an impedance control device is installed while, downstream, the exhaust nozzle can be easily varied to study its influence on noise generation. A mean chamber pressure higher than 2 bar can be reached for the targeted operating points. The present analysis of the flame behaviour is a first step towards the study of combustion noise. The flame dynamics are characterized by spectral analysis of the dynamic pressure in the combustion chamber. The aim of this work is to determine the dominating acoustic modes during combustion operation. With the help of analytical calculations, the test bench is first modelled as a two cavity system, and later as a five cavity system, taking into account the feeding lines. The nozzle can be assumed as choked due to the pressurization of the chamber. With this method, the majority of the acoustic modes can be identified and explained. The study shows that these modes are linked to the geometry of the whole combustor including the injection tube, the combustion chamber and the feeding lines.

Combustion Stability and Emissions in a Lean Premixed Industrial Gas Turbine Burner Due to Changes in the Fuel Profile

2009 ◽  
Author(s):  
A. Lindholm ◽  
D. Lo¨rstad ◽  
P. Magnusson ◽  
P. Andersson ◽  
T. Larsson
Keyword(s):  
Pressure Drop ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Dynamic Pressure ◽  
Image Intensifier ◽  
Flame Stabilization ◽  
Combustion Stability ◽  
Fuel Profile ◽  
Industrial Gas Turbine

This paper deals with an experimental investigation of dry low emission (DLE) burners for industrial gas turbines. Changes in the fuel profile, pressure drop over the burner and external pilot flame stabilization have been investigated regarding combustion stability and emissions. This has been achieved by parallel experimental work in a water rig and a newly commissioned atmospheric combustion test rig. Some verifying tests in a high pressure rig were also conducted. The work in the water rig has been directed towards evaluating different fuel profiles at the burner exit due to changes in the fuel outlet geometry. Variations of the fuel outlet geometry were achieved by altering the effective area of the hardware configuration of the fuel outlet ports or by moving or adding fuel outlet ports. A few of the tested configurations in the water rig was chosen for further evaluation by atmospheric combustion tests with respect to combustion stability and emissions. A more general study on combustion stability and emissions was also performed for different burners, burner configurations and variations in pressure drop over the burner. The pressure drop over the burner in the test corresponds very well to the pressure drop measured over a single burner in an annular combustion chamber of an industrial gas turbine at different loads. The combustion was monitored by a high speed video camera equipped with an image intensifier. Simultaneously the dynamic pressure was measured by a piezoelectric pressure transducer, making it possible to know when each image was taken relative to the pressure. Results for different hardware configurations will be shown considering the frequency response from the flame and the dynamic pressure as well as the characteristic combustion instability close to lean blowout.

Siemens SGT-800 Industrial Gas Turbine Enhanced to 50MW: Combustor Design Modifications, Validation and Operation Experience

2013 ◽  
Author(s):  
Daniel Lörstad ◽  
Annika Lindholm ◽  
Jan Pettersson ◽  
Mats Björkman ◽  
Ingvar Hultmark
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Cooling System ◽  
Good Condition ◽  
Combined Cycle ◽  
Combustion Stability ◽  
Combustion System ◽  
Design Work ◽  
Engine Operation ◽  
Cooling Air

Siemens Oil & Gas introduced an enhanced SGT-800 gas turbine during 2010. The new power rating is 50.5MW at a 38.3% electrical efficiency in simple cycle (ISO) and best in class combined-cycle performance of more than 55%, for improved fuel flexibility at low emissions. The updated components in the gas turbine are interchangeable from the existing 47MW rating. The increased power and improved efficiency are mainly obtained by improved compressor airfoil profiles and improved turbine aerodynamics and cooling air layout. The current paper is focused on the design modifications of the combustor parts and the combustion validation and operation experience. The serial cooling system of the annular combustion chamber is improved using aerodynamically shaped liner cooling air inlet and reduced liner rib height to minimize the pressure drop and optimize the cooling layout to improve the life due to engine operation hours. The cold parts of the combustion chamber were redesigned using cast cooling struts where the variable thickness was optimized to maximize the cycle life. Due to fewer thicker vanes of the turbine stage #1, the combustor-turbine interface is accordingly updated to maintain the life requirements due to the upstream effect of the stronger pressure gradient. Minor burner tuning is used which in combination with the previously introduced combustor passive damping results in low emissions for >50% load, which is insensitive to ambient conditions. The combustion system has shown excellent combustion stability properties, such as to rapid load changes and large flame temperature range at high loads, which leads to the possibility of single digit Dry Low Emission (DLE) NOx. The combustion system has also shown insensitivity to fuels of large content of hydrogen, different hydrocarbons, inerts and CO. Also DLE liquid operation shows low emissions for 50–100% load. The first SGT-800 with 50.5MW rating was successfully tested during the Spring 2010 and the expected performance figures were confirmed. The fleet leader has, up to January 2013, accumulated >16000 Equivalent Operation Hours (EOH) and a planned follow up inspection made after 10000 EOH by boroscope of the hot section showed that the combustor was in good condition. This paper presents some details of the design work carried out during the development of the combustor design enhancement and the combustion operation experience from the first units.

Effects of Pilot Fuel and Liner Cooling on the Flame Structure in a Full Scale Swirl-Stabilized Combustion Setup

2009 ◽  
Author(s):  
Jens Fa¨rber ◽  
Rainer Koch ◽  
Hans-Jo¨rg Bauer ◽  
Matthias Hase ◽  
Werner Krebs
Keyword(s):  
Combustion Chamber ◽  
Fuel Injection ◽  
Flame Structure ◽  
Cone Angle ◽  
Flow Patterns ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Combustion Noise ◽  
Pilot Fuel ◽  
Combustor Liner

The flame structure and the limits of operation of a lean premixed swirl flame were experimentally investigated under piloted and non-piloted conditions. Flame stabilization and blow out limits are discussed with respect to pilot fuel injection and combustor liner cooling for lean operating conditions. Two distinctly different flow patterns are found to develop depending on piloting and liner cooling parameters. These flow patterns are characterized with respect to flame stability, blow out limits, combustion noise and emissions. The combustion system explored consists of a single burner similar to the burners used in Siemens annular combustion systems. The burner feeds a distinctively non-adiabatic combustion chamber operated with natural gas under atmospheric pressure. Liner cooling is mimicked by purely convective cooling and an additional flow of ‘leakage air’ injected into the combustion chamber. Both, this additional air flow and the pilot fuel ratio were found to have a strong influence on the flow structure and stability of the flame close to the lean blow off limit (LBO). It is shown by Laser Doppler Velocimetry (LDV) that the angle of the swirl cone is strongly affected by pilot fuel injection. Two distinct types of flow patterns are observed close to LBO in this large scale setup: While non-piloted flames exhibit tight cone angles and small inner recirculation zones (IRZ), sufficient piloting results in a wide cone angle and a large IRZ. Only in the latter case, the main flow becomes attached to the combustor liner. Flame structures deduced from flow fields and CH-Chemiluminescence images depend on both the pilot fuel injection and liner cooling.

Control of Lean Blowout in Partially Premixed Swirl-Stabilized Combustor Using a Fuel Rich Central Pilot Configuration

2019 ◽  
Author(s):  
Somnath De ◽  
Prasanna Mondal ◽  
Gourav Manohar Sardar ◽  
Rakin Bin Bokhtiar ◽  
Arijit Bhattacharya ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Premixed Flames ◽  
Premixed Combustion ◽  
Combustion Stability ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Lean Blowout ◽  
Partially Premixed Combustion ◽  
Partially Premixed

Abstract The main problem for using reliable and stable diffusion combustion in modern gas turbine engines is the production of NOx at a higher level which is not permissible for maintaining the healthy environment. Thus, combustion in lean premixed mode has become the most promising technology in many applications related to power generation gas turbine, industrial burner etc. Although the lean combustion minimizes NOx production, it suffers from an increased risk of lean blowout (LBO) when the requirement of thrust or load is low. It mainly occurs at the lean condition when the equilibrium between the flame speed and the unburnt air-fuel mixture velocity is broken. Current aircraft gas turbine engines operate fuel close to the combustion chamber which leads to the partially premixed combustion. Partially premixed combustion is also susceptible to lean blowout. Therefore, we have designed a swirl-stabilized dump combustor, where different lengths of fuel-air mixing are available. Our present work aims at improving the combustion stability by incorporating a secondary fuel injection through a pilot arrangement connected with the combustion chamber for premixed as well as partially premixed flames. Incorporation of the pilot system adds a small fraction of the total fuel into the combustion chamber directly. This investigation shows significant extension of the LBO limit towards leaner fuel-air mixture while the NOx emission in the combustion chamber is within the permissible limit. This result can be used for aircraft operators during the process of landing when fuel supply has to be decreased to reduce engine thrust or for power plants operating at low loads. The study of control is based on the colour variation of the flame which actually defines the changes in combustion characteristics. For early detection of LBO, the ratio between the intensity of red and blue colour obtained from flame images with a high speed camera is used. As LBO is approached, the ratio of red to blue intensity falls monotonically. When the ratio falls below a preset threshold, a small fraction of the total fuel is added to the central pilot line. This strategy allows the LBO limit to be shifted to a much lower equivalence ratio (maximum 20% and 11% for fully premixed and least premixed flames, respectively) without any significant increase in NOx production. The analysis includes a feedback control algorithm which is computed in MATLAB and the code is embedded in Labview for hardware implementation.

Investigation of Flame Stabilization in a High-Pressure Multi-Jet Combustor by Laser Measurement Techniques

2014 ◽  
Author(s):  
Oliver Lammel ◽  
Tim Rödiger ◽  
Michael Stöhr ◽  
Holger Ax ◽  
Peter Kutne ◽  
...  
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Recirculation Zone ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Single Shot ◽  
Optical Access

In this contribution, comprehensive optical and laser based measurements in a generic multi-jet combustor at gas turbine relevant conditions are presented. The flame position and shape, flow field, temperatures and species concentrations of turbulent premixed natural gas and hydrogen flames were investigated in a high-pressure test rig with optical access. The needs of modern highly efficient gas turbine combustion systems, i.e., fuel flexibility, load flexibility with increased part load capability, and high turbine inlet temperatures, have to be addressed by novel or improved burner concepts. One promising design is the enhanced FLOX® burner, which can achieve low pollutant emissions in a very wide range of operating conditions. In principle, this kind of gas turbine combustor consists of several nozzles without swirl, which discharge axial high momentum jets through orifices arranged on a circle. The geometry provides a pronounced inner recirculation zone in the combustion chamber. Flame stabilization takes place in a shear layer around the jet flow, where fresh gas is mixed with hot exhaust gas. Flashback resistance is obtained through the absence of low velocity zones, which favors this concept for multi-fuel applications, e.g. fuels with medium to high hydrogen content. The understanding of flame stabilization mechanisms of jet flames for different fuels is the key to identify and control the main parameters in the design process of combustors based on an enhanced FLOX® burner concept. Both experimental analysis and numerical simulations can contribute and complement each other in this task. They need a detailed and relevant data base, with well-known boundary conditions. For this purpose, a high-pressure burner assembly was designed with a generic 3-nozzle combustor in a rectangular combustion chamber with optical access. The nozzles are linearly arranged in z direction to allow for jet-jet interaction of the middle jet. This line is off-centered in y direction to develop a distinct recirculation zone. This arrangement approximates a sector of a full FLOX® gas turbine burner. The experiments were conducted at a pressure of 8 bar with preheated and premixed natural gas/air and hydrogen/air flows and jet velocities of 120 m/s. For the visualization of the flame, OH* chemiluminescence imaging was performed. 1D laser Raman scattering was applied and evaluated on an average and single shot basis in order to simultaneously and quantitatively determine the major species concentrations, the mixture fraction and the temperature. Flow velocities were measured using particle image velocimetry at different section planes through the combustion chamber.

CFD Simulation of Noise in Gas Turbine Combustors by Means of Turbulence Refluctuation Method

2008 ◽  
Author(s):  
Stefano Tiribuzi
Keyword(s):  
Gas Turbine ◽  
Local Level ◽  
Computing Time ◽  
Combustion Noise ◽  
Qualitative Description ◽  
Combustion Stability ◽  
Medium Size ◽  
Pure Hydrogen ◽  
Computational Domain ◽  
Gas Turbine Combustors

The paper describes a numerical simulation methodology based on CFD for deriving and analyzing the spectral and spatial characteristics of combustion noise in industrial gas turbine combustors. ENEL is testing the combustion section of a medium size pure hydrogen-fed gas turbine, during which pressure fluctuation levels are also measured to asses the combustion stability. Pressure probes are located in colder zones only, but information on the fluctuations levels throughout the whole component are also desired. For this purpose, a simple empirical and, to the knowledge of the author, original method, based solely on CFD modelling, was developed for reproducing in a realistic way the spatial and transient characteristics of the acoustic flow field inside the combustor volumes. The method employs a sparse and persistent excitation on a wide frequency spectrum, by imposing a stochastic fluctuating component to the velocity computed on each grid node throughout the entire computational domain. The intensity of this additional component is proportional to the local level of the modelled turbulent velocity, so the method will be shortly designated as PRMT (Partial Refluctuation of Modelled Turbulence). This method requires that all the acoustically connected volumes be included in the computational domain and that transients be protracted for a time sufficient to provide meaningful spectral information. KIEN, an in-house low diffusive URANS code capable of simulating 3D reactive flows, was used. The adopted Very Rough Grid approach made it possible to protract the simulated transient for a long time, with an affordable computing time. Comparison with in-plant measured data shows that the refluctuation method provides a realistic qualitative description of the noise spectrum. The spatial distribution of computed acoustic field is also derived and analyzed.

Effects of Nozzle Helmholtz Number on Indirect Combustion Noise by Compositional Perturbations

2017 ◽  
Author(s):  
Luca Magri ◽  
Jeffrey O’Brien ◽  
Matthias Ihme
Keyword(s):  
Velocity Profile ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Transfer Functions ◽  
Mixture Fraction ◽  
Supersonic Nozzle ◽  
Noise Pollution ◽  
Combustion Noise ◽  
Dipole Source ◽  
Thermoacoustic Oscillations

By modeling a multi-component gas, a new source of indirect combustion noise is identified, which is named compositional indirect noise. The advection of mixture inhomogeneities exiting the gas-turbine combustion chamber through subsonic and supersonic nozzles is shown to be an acoustic dipole source of sound. The level of mixture inhomogeneity is described by a difference in composition with the mixture fraction. An n-dodecane mixture, which is a kerosene fuel relevant to aeronautics, is used to evaluate the level of compositional noise. By relaxing the compact-nozzle assumption, the indirect noise is numerically calculated for Helmholtz numbers up to 2 in nozzles with linear velocity profile. The compact-nozzle limit is discussed. Only in this limit, it is possible to derive analytical transfer functions for (i) the noise emitted by the nozzle and (ii) the acoustics travelling back to the combustion chamber generated by accelerated compositional inhomogeneities. The former contributes to noise pollution, whereas the latter has the potential to induce thermoacoustic oscillations. It is shown that the compositional indirect noise can be at least as large as the direct noise and entropy noise in chocked nozzles and lean mixtures. As the frequency with which the compositional inhomogeneities enter the nozzle increases, or as the nozzle spatial length increases, the level of compositional noise decreases, with a similar, but not equal, trend to the entropy noise. The noisiest configuration is found to be a compact supersonic nozzle.

Large Eddy Simulation and Experimental Analysis of Combustion Dynamics in a Gas Turbine Burner

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Daniel Moëll ◽  
Andreas Lantz ◽  
Karl Bengtson ◽  
Daniel Lörstad ◽  
Annika Lindholm ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Cross Flow ◽  
Flame Stabilization ◽  
Large Eddy Simulations ◽  
Combustion Dynamics ◽  
Flamelet Generated Manifold ◽  
Large Eddy ◽  
Gas Turbine Burner

Large eddy simulations (LES) and experiments (planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) and pressure transducer) have been carried out on a gas turbine burner fitted to an atmospheric combustion rig. This burner, from the Siemens SGT-800 gas turbine, is a low NOx, partially premixed burner, where preheat air temperature, flame temperature, and pressure drop across the burner are kept similar to engine full load conditions. The large eddy simulations are based on a flamelet-generated manifold (FGM) approach for representing the chemistry and the Smagorinsky model for subgrid turbulence. The experimental data and simulation data are in good agreement, both in terms of time averaged and time-resolved quantities. From the experiments and LES, three bands of frequencies of pressure fluctuations with high power spectral density are found in the combustion chamber. The first two bands are found to be axial pressure modes, triggered by coherent flow motions from the burner, such as the flame stabilization location and the precessing vortex core (PVC). The third band is found to be a cross flow directional mode interacting with two of the four combustion chamber walls in the square section of the combustion chamber, triggered from general flow motions. This study shows that LES of real gas turbine components is feasible and that the results give important insight into the flow, flame, and acoustic interactions in a specific combustion system.

Improvement of Gas Turbine Injection Systems by Combined Experimental/Numerical Approach

2002 ◽  
Author(s):  
G. Riccio ◽  
P. Adami ◽  
F. Martelli ◽  
D. Cecchini ◽  
L. Carrai
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Fuel Injection ◽  
Numerical Approach ◽  
Combustion Stability ◽  
Pollutant Emissions ◽  
Injection System ◽  
Flame Stability ◽  
Fuel Injection System ◽  
Joint Application

An aerodynamic study for the premixing device of an industrial turbine gas combustor is discussed. The present work is based on a joint application of numerical CFD and experimental investigation tools in order to verify and optimize the combustor gaseous fuel injection system. The objective is the retrofit of an old generation gas turbine combustion chamber that is carried out considering new targets of NOx emission keeping the same CO and combustion stability performances. CFD has been used to compare different premixing duct configurations for improved mixing features. Experimental test has been carried out in order to assess the pollutant emissions, flame stability and pattern factor characteristics of the full combustion chamber retrofitted with the modified injection system.

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