FLOX ® Combustion at High Pressure With Different Fuel Compositions

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Rainer Lückerath ◽  
Wolfgang Meier ◽  
Manfred Aigner
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Gas Turbine ◽  
Flue Gas ◽  
Operating Conditions ◽  
Atmospheric Conditions ◽  
Relative Temperature ◽  
Planar Laser ◽  
Gas Recirculation ◽  
First Time

In flameless oxidation (FLOX®) the combustion is distributed over a large volume by a high internal flue gas recirculation. This technology has been successfully used for many years in technical furnaces under atmospheric conditions with very low NOx emissions. In the work presented here, FLOX® combustion was for the first time investigated at high pressure in order to assess its applicability for gas turbine combustors. A FLOX® burner was equipped with a combustion chamber with quartz windows and installed into a high pressure test rig with optical access. The burner was operated under typical gas turbine conditions at a pressure of 20bar with thermal powers up to 475kW. Natural gas, as well as mixtures of natural gas and H2 were used as fuel. The NOx and CO emissions were recorded for the different operating conditions. OH* chemiluminescence imaging and planar laser-induced fluorescence of OH were applied in order to characterize the flame zone and the relative temperature distributions. The combustion behavior was investigated as a function of equivalence ratio and fuel composition, and the influence of the gas inlet velocity on mixing and emissions was studied. For various operating conditions, the lean extinction limits were determined.

FLOX® Combustion at High Pressure With Different Fuel Compositions

2007 ◽  
Author(s):  
Rainer Lu¨ckerath ◽  
Wolfgang Meier ◽  
Manfred Aigner
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Gas Turbine ◽  
Flue Gas ◽  
Operating Conditions ◽  
Atmospheric Conditions ◽  
Relative Temperature ◽  
Planar Laser ◽  
Gas Recirculation ◽  
First Time

In Flameless Oxidation (FLOX®) the combustion is distributed over a large volume by a high internal flue gas recirculation. This technology has been successfully used for many years in technical furnaces under atmospheric conditions with very low NOx emissions. In the work presented here, FLOX® combustion was for the first time investigated at high pressure in order to assess its applicability for gas turbine combustors. A FLOX® burner was equipped with a combustion chamber with quartz windows and installed into a high pressure test rig with optical access. The burner was operated under typical gas turbine conditions at pressure of 20 bar with thermal powers up to 475 kW. Natural gas as well as mixtures of natural gas and H2 were used as fuel. The NOx and CO emissions were recorded for the different operating conditions. OH* chemiluminescence imaging and planar laser-induced fluorescence of OH were applied in order to characterize the flame zone and the relative temperature distributions. The combustion behaviour was investigated as a function of equivalence ratio and fuel composition, and the influence of the gas inlet velocity on mixing and emissions was studied. For various operating conditions the lean extinction limits were determined.

Comparison of Methane and Natural Gas Combustion Behavior at Gas Turbine Conditions With Flue Gas Recirculation

2010 ◽  
Author(s):  
Dieter Winkler ◽  
Simon Reimer ◽  
Pascal Mu¨ller ◽  
Timothy Griffin
Keyword(s):  
Natural Gas ◽  
Flame Front ◽  
Gas Turbine ◽  
Flue Gas ◽  
Power Plants ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Synthetic Natural Gas ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

The efficiency and economics of carbon dioxide capture in gas turbine combined cycle power plants can be significantly improved by introducing Flue Gas Recirculation (FGR) to increase the CO2 concentration in the flue gas and reduce the volume of the flue gas treated in the CO2 capture plant [1], [2]. The maximum possible level of FGR is limited to that corresponding to stoichiometric conditions in the combustor. Reduced excess oxygen, however, leads to negative effects on overall fuel reactivity and thus increased CO emissions. Combustion tests have been carried out in a generic burner under typical gas turbine conditions with methane, synthetic natural gas (mixtures of methane and ethane) and natural gas from the Swiss net to investigate the effect of different C2+ contents in the fuel on CO burnout. To locate the flame front and to measure emissions for different residence times a traversable gas probe was designed and employed. Increasing the FGR ratio led to lower reactivity indicated by a movement of the flame front downstream. Thus, sufficient flame burnout—indicated by low emissions of unburned components (CO, UHC)—required a longer residence time in the combustion chamber. Adding C2+ or H2 to the fuel moved the flame zone back upstream and reduced the burnout time. Tests were performed for the various fuel compositions at different FGR ratios and oxidant preheat temperatures. For all conditions the addition of ethane (6 and 16% vol.) or hydrogen (20% vol.) to methane shows comparable trends. Addition of hydrogen to (synthetic) natural gas which already contains C2+ has less of a beneficial effect on reactivity and CO burnout than the addition of hydrogen to pure methane. A simple ideal reactor network based on plug flow reactors with internal hot gas recirculation was used to model combustion in the generic combustor. The purpose of such a simple model is to generate a design basis for future tests with varying operating conditions. The model was able to reproduce the trends found in the experimental investigation, for example the level of H2 required to offset the effect of oxygen depletion due to simulated FGR.

Flue Gas Recirculation of the Alstom Sequential Gas Turbine Combustor Tested at High Pressure

2011 ◽  
Author(s):  
Felix Guethe ◽  
Dragan Stankovic ◽  
Franklin Genin ◽  
Khawar Syed ◽  
Dieter Winkler
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Flue Gas ◽  
Operating Conditions ◽  
Limiting Factors ◽  
Combustion System ◽  
Flue Gas Recirculation ◽  
Wide Range ◽  
Gas Recirculation ◽  
The Impact

Concerning the efforts in reducing the impact of fossil fuel combustion on climate change for power production utilizing gas turbine engines Flue Gas Recirculation (FGR) in combination with post combustion carbon capture and storage (CCS) is one promising approach. In this technique part of the flue gas is recirculated and introduced back into the compressor inlet reducing the flue gas flow (to the CCS) and increasing CO2 concentrations. Therefore FGR has a direct impact on the efficiency and size of the CO2 capture plant, with significant impact on the total cost. However, operating a GT under depleted O2 and increased CO2 conditions extends the range of normal combustor experience into a new regime. High pressure combustion tests were performed on a full scale single burner reheat combustor high-pressure test rig. The impact of FGR on NOx and CO emissions is analyzed and discussed in this paper. While NOx emissions are reduced by FGR, CO emissions increase due to decreasing O2 content although the SEV reheat combustor could be operated without problem over a wide range of operating conditions and FGR. A mechanism uncommon for GTs is identified whereby CO emissions increase at very high FGR ratios as stoichiometric conditions are approached. The feasibility to operate Alstom’s reheat engine (GT24/GT26) under FGR conditions up to high FGR ratios is demonstrated. FGR can be seen as continuation of the sequential combustion system which already uses a combustor operating in vitiated air conditions. Particularly promising is the increased flexibility of the sequential combustion system allowing to address the limiting factors for FGR operation (stability and CO emissions) through separated combustion chambers.

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.

scholarly journals Observations of Flame Behavior in a Laboratory-Scale Pre-Mixed Natural Gas/Air Gas Turbine Combustor From PLIF Measurements of OH

2002 ◽  
Author(s):  
Paul O. Hedman ◽  
Thomas H. Fletcher ◽  
Stewart G. Graham ◽  
G. Wayne Timothy ◽  
Daniel V. Flores ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Flame Structure ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Airflow Rate ◽  
Gas Turbine Combustor ◽  
Planar Laser ◽  
Swirl Injector ◽  
Order Of Magnitude

The objective of this study was to obtain instantaneous planar laser induced fluorescence (PLIF) images of OH in a laboratory-scale, gas-turbine combustor (LSGTC) with a pre-mixed, swirl-stabilized, natural gas flame. Instantaneous PLIF images of OH were obtained at each of four operating conditions (high swirl and medium swirl at fuel equivalence ratios of 0.80 and 0.65). Comparison of the instantaneous images illustrates the stochastic nature of the flame structure. Pixel by pixel statistical analysis of each collection of images allowed both mean and standard deviation images to be generated, and analysis at selected locations has allowed probability density functions to be obtained in various regions of the flame structure. PLIF images of OH, along with visual photographs and video recordings, showed a wide variation in flame structure for the different operating conditions. The variations in flame shapes are primarily a result of the effect of the swirl intensity and fuel equivalence ratio. Changes in the airflow rate over an order of magnitude do not seem to affect the visual flame structure in this experiment. Operation at φ = 0.80 produced the most stable flames with both injectors. The flame with the high swirl injector was more coalesced and closer to the injector than with the medium swirl injector. At φ = 0.65, the flame was quite unstable for both swirl injectors. With the medium swirl injector, the flame would oscillate between two different flame structures, one that was more or less attached to the vortex funnel, and one that was lifted well above the vortex funnel. The MS case at φ = 0.65 was at the very edge of the lean flammability limit, and would on occasion extinguish.

Experimental Investigation of a Fuel Flexible Generic Gas Turbine Combustor With External Flue Gas Recirculation

2014 ◽  
Author(s):  
Stefan Fischer ◽  
David Kluß ◽  
Franz Joos
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Flue Gas ◽  
Power Plants ◽  
Numerical Study ◽  
Combined Cycle ◽  
Gas Turbine Combustor ◽  
Combustion Behavior ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

Flue gas recirculation in combined cycle power plants using hydrocarbon fuels is a promising technology for increasing the efficiency of the post combustion carbon capture and storage process. However, the operation with flue gas recirculation significantly changes the combustion behavior within the gas turbine. In this paper the effects of external flue gas recirculation on the combustion behavior of a generic gas turbine combustor was experimentally investigated. While prior studies have been performed with natural gas, the focus of this paper lies on the investigation of the combustion behavior of alternative fuel gases at atmospheric conditions, namely typical biogas mixtures and syngas. The flue gas recirculation ratio and the fuel mass flow were varied to establish the operating region of stable flammability. In addition to the experimental investigations, a numerical study of the combustive reactivity under flue gas recirculation conditions was performed. Finally, a prediction of blowout limits was performed using a perfectly stirred reactor approach and the experimental natural gas lean extinction data as a reference. The extinction limits under normal (non-vitiated) and flue gas recirculation conditions can be predicted well for all the fuels investigated.

scholarly journals Numerical Analysis of Turbulent Combustion in a Model Swirl Gas Turbine Combustor

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Ali Cemal Benim ◽  
Sohail Iqbal ◽  
Franz Joos ◽  
Alexander Wiedermann
Keyword(s):  
Experimental Data ◽  
Natural Gas ◽  
Gas Turbine ◽  
Turbulence Model ◽  
Flue Gas ◽  
Numerical Study ◽  
Mixture Fraction ◽  
Gas Turbine Combustor ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

Turbulent reacting flows in a generic swirl gas turbine combustor are investigated numerically. Turbulence is modelled by a URANS formulation in combination with the SST turbulence model, as the basic modelling approach. For comparison, URANS is applied also in combination with the RSM turbulence model to one of the investigated cases. For this case, LES is also used for turbulence modelling. For modelling turbulence-chemistry interaction, a laminar flamelet model is used, which is based on the mixture fraction and the reaction progress variable. This model is implemented in the open source CFD code OpenFOAM, which has been used as the basis for the present investigation. For validation purposes, predictions are compared with the measurements for a natural gas flame with external flue gas recirculation. A good agreement with the experimental data is observed. Subsequently, the numerical study is extended to syngas, for comparing its combustion behavior with that of natural gas. Here, the analysis is carried out for cases without external flue gas recirculation. The computational model is observed to provide a fair prediction of the experimental data and predict the increased flashback propensity of syngas.

Flow Analysis of High Pressure Catalytic Combustor for Gas Turbine

1995 ◽  
Author(s):  
Y. Tsujikawa ◽  
S. Fujii ◽  
H. Sadamori ◽  
S. Ito ◽  
S. Katsura
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Gas Turbine ◽  
Flow Analysis ◽  
Methane Combustion ◽  
Single Step ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Gas Temperature ◽  
Radial Convection

The objective of this paper is modeling the mechanism of high temperature catalytic oxidation of natural gas, or methane. The model is two-dimensional steady-state, and includes axial and radial convection and diffusion of mass, momentum and energy, as well as homogeneous (gas phase) and heterogeneous (gas-surface) single step irreversible chemical reactions within a catalyst channel. Experimental investigations were also made of natural gas, or methane combustion in the presence of Mn-substituted hexaaluminate catalysts. Axial profiles of catalyst wall temperature, and gas temperature and gas composition for a range of gas turbine combustor operating conditions have been obtained for comparison with and development of a computer model of catalytic combustion. Numerical calculation results for low pressure agree well with experimental data. The calculations have been extended for high pressure (10 atms) operating conditions of gas turbine.

Numerical Simulations of Turbulent Mixing and Autoignition of Hydrogen Fuel at Reheat Combustor Operating Conditions

2011 ◽  
Author(s):  
Elizaveta Ivanova ◽  
Berthold Noll ◽  
Peter Griebel ◽  
Manfred Aigner ◽  
Khawar Syed
Keyword(s):  
Natural Gas ◽  
Numerical Simulations ◽  
Flue Gas ◽  
Turbulent Mixing ◽  
Turbulence Modeling ◽  
Numerical Study ◽  
Operating Conditions ◽  
Fuel Blend ◽  
Flow Configuration ◽  
Modeling Methods

Turbulent mixing and autoignition of H2-rich fuels at relevant reheat combustor operating conditions are investigated in the present numerical study. The flow configuration under consideration is a fuel jet perpendicularly injected into a crossflow of hot flue gas (T > 1000K, p = 15bar). Based on the results of the experimental study for the same flow configuration and operating conditions two different fuel blends are chosen for the numerical simulations. The first fuel blend is a H2/natural gas/N2 mixture at which no autoignition events were observed in the experiments. The second fuel blend is a H2/N2 mixture at which autoignition in the mixing section occurred. First, the non-reacting flow simulations are performed for the H2/natural gas/N2 mixture in order to compare the accuracy of different turbulence modeling methods. Here the steady-state Reynolds-averaged Navier-Stokes (RANS) as well as the unsteady scale-adaptive simulation (SAS) turbulence modeling methods are applied. The velocity fields obtained in both simulations are directly validated against experimental data. The SAS method shows better agreement with the experimental results. In the second part of the present work the autoignition of the H2/N2 mixture is numerically studied using the 9-species 21-steps reaction mechanism of O’Conaire et al. [1]. As in the reference experiments, autoignition can be observed in the simulations. Influences of the turbulence modeling as well as of the hot flue gas temperature are investigated. The onset and the propagation of the ignition kernels are studied based on the SAS modeling results. The obtained numerical results are discussed and compared with data from experimental autoignition studies.

Lean Blowout Limit and NOx-Production of a Premixed Sub-ppm NOx Burner With Periodic Flue Gas Recirculation

2004 ◽  
Author(s):  
Jochen R. Kalb ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Flue Gas ◽  
Gas Content ◽  
Stable Operation ◽  
Reacting Flow ◽  
Nox Emissions ◽  
Lean Blowout ◽  
Fresh Mixture ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

The technological objective of this work is the development of a lean-premixed burner for natural gas. Sub-ppm NOx emissions can be accomplished by shifting the lean blowout limit (LBO) to slightly lower adiabatic flame temperatures than the LBO of current standard burners. This can be achieved with a novel burner concept utilizing periodic flue gas recirculation: Hot flue gas is admixed to the injected premixed fresh mixture with a mass flow rate of comparable magnitude, in order to achieve self-ignition. The subsequent combustion of the diluted mixture again delivers flue gas. A fraction of the combustion products is then admixed to the next stream of fresh mixture. This process pattern is to be continued in a cyclically closed topology, in order to achieve stable combustion of e.g. natural gas in a temperature regime of very low NOx production. The principal ignition behavior and NOx production characteristics of one sequence of the periodic process was modeled by an idealized adiabatic system with instantaneous admixture of partially or completely burnt flue gas to one stream of fresh reactants. With the CHEMKIN-II package a reactor network consisting of one perfectly stirred reactor (PSR, providing ignition in the first place) and two plug flow reactors (PFR) has been used. The effect of varying burnout and the influence of the fraction of admixed flue gas have been evaluated. The simulations have been conducted with the reaction mechanism of Miller and Bowman and the GRI-Mech 3.0 mechanism. The results show that the high radical content of partially combusted products leads to a massive decrease of the time required for the formation of the radical pool. As a consequence, self-ignition times of 1 ms are achieved even at adiabatic flame temperatures of 1600 K and less, if the flue gas content is about 50%–60% of the reacting flow after mixing is complete. Interestingly, the effect of radicals on ignition is strong, outweighs the temperature deficiency and thus allows stable operation at very low NOx emissions.

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