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.

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.

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.

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.

Modelling the Effect of External Flue Gas Recirculation on NOx and CO Emissions in a Premixed Gas Turbine Combustor With Chemical Reactor Networks

2018 ◽  
Author(s):  
V. Prakash ◽  
J. Steimes ◽  
D. J. E. M. Roekaerts ◽  
S. A. Klein
Keyword(s):  
Gas Turbine ◽  
Flue Gas ◽  
Recirculation Zone ◽  
Chemical Reactor ◽  
Inlet Temperature ◽  
Part Load ◽  
Flue Gas Recirculation ◽  
Reactor Networks ◽  
Gas Recirculation ◽  
The Impact

The increasing amount of renewable energy and emission norms challenge gas turbine power plants to operate at part-load with high efficiency, while reducing NOx and CO emissions. A novel solution to this dilemma is external Flue Gas Recirculation (FGR), in which flue gases are recirculated to the gas turbine inlet, increasing compressor inlet temperature and enabling higher part load efficiencies. FGR also alters the oxidizer composition, potentially leading to reduced NOx levels. This paper presents a kinetic model using chemical reactor networks in a lean premixed combustor to study the impact of FGR on emissions. The flame zone is split in two perfectly stirred reactors modelling the flame front and the recirculation zone. The flame reactor is determined based on a chemical time scale approach, accounting for different reaction kinetics due to FGR oxidizers. The recirculation zone is determined through empirical correlations. It is followed by a plug flow reactor. This method requires less details of the flow field, has been validated with literature data and is generally applicable for modelling premixed flames. Results show that due to less O2 concentration, NOx formation is inhibited down to 10–40% and CO levels are escalated up to 50%, for identical flame temperatures. Increasing combustor pressure leads to a rise in NOx due to thermal effects beyond 1800 K, and a drop in CO levels, due to the reduced chemical dissociation of CO2. Wet FGR reduces NOx by 5–10% and increases CO by 10–20%.

Investigation of a Gas Turbine Process With Reheat Combustion at Flue Gas Recirculation and Oxyfuel-Conditions

2017 ◽  
Author(s):  
Florian Beenken ◽  
Franz Joos
Keyword(s):  
Gas Turbine ◽  
Flue Gas ◽  
Co2 Sequestration ◽  
Fossil Fuels ◽  
Pressure Ratio ◽  
Electrical Power ◽  
Exhaust Gas ◽  
Power Station ◽  
Flue Gas Recirculation ◽  
Gas Recirculation

In near future electrical power generation will still be supplied by fossil fuels. To reach the targets of the conference on climate change in Paris 2015 one method proposed is the CO2 sequestration and usage or alternatively storage. Compared to coal-fired power station the amount of CO2 in the exhaust gas of gas turbine power station is much less and therefore more difficult to remove. To enhance the efficiency of the CO2-sequestration process enrichment of the CO2 in the exhaust gas could be a solution. This can be achieved by exhaust gas recirculation or by burning with pure O2 instead of air avoiding a lot of N2 in the exhaust gas, called Oxyfuel process. The work concerns to investigations of a reheat gas turbine operating with flue gas recirculation as well as with Oxyfuel operation. The thermodynamic process has been modeled in detail considering the additional demand of cooling of the combustors and the turbines at Oxyfuel process. Additional combustion experiments have been carried out with flue gas recirculation as well as with Oxyfuel conditions burning Natural Gas with O2 in a CO2 environment to investigate the flame stability and extinction limit. The thermophysical properties, like specific heat capacity and sound velocity, are strongly altered by the high content of CO2 and H2O in the fluid of the turbine as well as of the compressor. For example during Oxyfuel conditions the pressure ratio is expected to decrease to about 78% of air operation. The influence of flue gas recirculation and Oxyfuel process to the gas composition as well as to the heat transfer and exit conditions are discussed.

A Novel Intake Concept for Flue Gas Recirculation to Enhance CCS in an Industrial Gas Turbine

2014 ◽  
Author(s):  
Robin C. Payne ◽  
Manuel Arias ◽  
Vassilis Stefanis
Keyword(s):  
Gas Turbine ◽  
Flue Gas ◽  
Carbon Capture ◽  
Low Cost ◽  
Co2 Concentration ◽  
Combined Cycle ◽  
Flue Gas Recirculation ◽  
Novel Approach ◽  
Inlet Conditions ◽  
Gas Recirculation

For the next generation of combined cycles, it is essential to not only improve the performance of a gas turbine combined cycle power plant, but also reduce its environmental impact. Flue Gas Recirculation is a useful method to increase CO2 concentration in the exhaust stream, allowing a smaller and lower cost carbon capture plant than would be required without FGR. Conventional FGR methodology requires a complex mixer with long mixing section to achieve acceptable inlet conditions for the GT compressor. A novel approach is presented, where the method of introducing the flue gas to the compressor has been substantially rethought to provide a low cost and robust FGR solution for carbon capture and sequestration applications. In this paper, CFD analysis of the flow in the intake section is used to demonstrate the operating principle of such a method, and cycle modelling calculations to compare its performance with a more conventional approach.

scholarly journals Combustion Characteristics of 0.5 MW Class Oxy-Fuel FGR (Flue Gas Recirculation) Boiler for CO2 Capture

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4333
Author(s):  
Joon Ahn ◽  
Hyouck-Ju Kim
Keyword(s):  
Natural Gas ◽  
Flue Gas ◽  
Power Plants ◽  
Fuel Combustion ◽  
Upstream Region ◽  
Exhaust Gas ◽  
Flue Gas Recirculation ◽  
Partial Load ◽  
Industrial Boilers ◽  
Gas Recirculation

A 0.5 MW class oxy-fuel boiler was developed to capture CO2 from exhaust gas. We adopted natural gas as the fuel for industrial boilers and identified characteristics different from those of pulverized coal, which has been studied for power plants. We also examined oxy-fuel combustion without flue gas recirculation (FGR), which is not commonly adopted in power plant boilers. Oxy-fuel combustion involves a stretched flame that uniformly heats the combustion chamber. In oxy-natural-gas FGR combustion, water vapor was included in the recirculated gas and the flame was stabilized when the oxygen concentration of the oxidizer was 32% or more. While flame delay was observed at a partial load for oxy-natural-gas FGR combustion, it was not observed for other combustion modes. In oxy-fuel combustion, the flow rate and flame fullness decrease but, except for the upstream region, the temperature near the wall is distributed not lower than that for air combustion because of the effect of gas radiation. For this combustion, while the heat flux is lower than other modes in the upstream region, it is more than 60% larger in the downstream region. When oxy-fuel and FGR combustion were employed in industrial boilers, more than 90% of CO2 was obtained, enabling capture, sequestration, and boiler performance while satisfying exhaust gas regulations.

scholarly journals Experimental and numerical study on the combustion of a 32 MW wood-chip grate boiler with internal flue gas recirculation technology

2017 ◽  
Vol 143 ◽  
pp. 591-598 ◽  
Author(s):  
Yaojie Tu ◽  
Anqi Zhou ◽  
Mingchen Xu ◽  
Wenming Yang ◽  
Keng Boon Siah ◽  
...  
Keyword(s):  
Flue Gas ◽  
Numerical Study ◽  
Wood Chip ◽  
Flue Gas Recirculation ◽  
Gas Recirculation
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