An Experimental and Modeling Study of Humid Air Premixed Flames

2000 ◽  
Vol 122 (3) ◽  
pp. 405-411 ◽  
Author(s):  
Anuj Bhargava ◽  
Med Colket ◽  
William Sowa ◽  
Kent Casleton ◽  
Dan Maloney
Keyword(s):  
Gas Turbine ◽  
Equivalence Ratio ◽  
Premixed Flames ◽  
Equilibrium Temperature ◽  
Network Code ◽  
Humid Air ◽  
Nox Formation ◽  
Atom Concentration ◽  
Wide Range ◽  
Modeling Study

An experimental and modeling study has been performed jointly by UTRC and DOE-FETC to determine the effect of humidity in the combustion air on emissions and stability limits of gas turbine premixed flames. This study focuses on developing gas turbine combustor design criteria for the Humid Air Turbine (HAT) cycle. The experiments were conducted at different moisture levels (0 percent, 5 percent, 10 percent, and 15 percent by mass in the air), at a total pressure of 200 psi, pilot levels (0 percent, 1 percent, 3 percent, and 5 percent total fuel), and equivalence ratio (0.4 to 0.8 depending on the moisture levels). The moisture levels were achieved by injecting steam into dry air well upstream of the fuel-air premixing nozzle. Computations were made for comparison to the experiments using GRI Mech 2.11 kinetics and thermodynamic database for modeling the flame chemistry. A Perfectly Stirred Reactor (PSR) network code was used to create a network of PSRs to simulate the flame. Excellent agreement between the measured and modeled NOx (5–10 percent) was obtained. Trends of added moisture reducing NOx and the effects of equivalence ratio and piloting level were well predicted. The CO predictions were higher by about 30–50 percent. The CO discrepancies are attributed to in-probe oxidation. The agreement between the data and model predictions over a wide range of conditions indicate the consistency and reliability of the measured data and usefulness of the modeling approach. An analysis of NOx formation revealed that at constant equilibrium temperature, Teq, the presence of steam leads to lower O-atom concentration which reduces “Zeldovich and N2O” NOx while higher OH-atom concentration reduces “Fenimore” NOx.[S0742-4795(00)00703-1]

scholarly journals An Experimental and Modeling Study of Humid Air Premixed Flames

1999 ◽  
Author(s):  
Anuj Bhargava ◽  
Med Colket ◽  
William Sowa ◽  
Kent Casleton ◽  
Dan Maloney
Keyword(s):  
Gas Turbine ◽  
Equivalence Ratio ◽  
Premixed Flames ◽  
Equilibrium Temperature ◽  
Network Code ◽  
Humid Air ◽  
Nox Formation ◽  
Atom Concentration ◽  
Wide Range ◽  
Modeling Study

An experimental and modeling study has been performed jointly by UTRC and DOE-FETC to determine the effect of humidity in the combustion air on emissions and stability limits of gas turbine premixed flames. This study focuses on developing gas turbine combustor design criteria for the Humid Air Turbine (HAT) cycle. The experiments were conducted at different moisture levels (0%, 5%, 10% and 15% by mass in the air), at a total pressure of 200 psi, pilot levels (0%, 1%, 3% and 5% total fuel), and equivalence ratio (0.4 to 0.8 depending on the moisture levels). The moisture levels were achieved by injecting steam into dry air well upstream of the fuel-air premixing nozzle. Computations were made for comparison to the experiments using GRI Mech 2.11 kinetics and thermodynamic database for modeling the flame chemistry. A Perfectly Stirred Reactor (PSR) network code was used to create a network of PSRs to simulate the flame. Excellent agreement between the measured and modeled NOx (5–10%) was obtained. Trends of added moisture reducing NOx and the effects of equivalence ratio and piloting level were well predicted. The CO predictions were higher by about 30–50%. The CO discrepancies are attributed to in-probe oxidation. The agreement between the data and model predictions over a wide range of conditions indicate the consistency and reliability of the measured data and usefulness of the modeling approach. An analysis of NOx formation revealed that at constant equilibrium temperature, Teq, the presence of steam leads to lower O-atom concentration which reduces “Zeldovich and N2O” NOx while higher OH-atom concentration reduces “Fenimore” NOx.

scholarly journals Prediction of Auto-Ignition Temperatures and Delays for Gas Turbine Applications

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Roda Bounaceur ◽  
Pierre-Alexandre Glaude ◽  
Baptiste Sirjean ◽  
René Fournet ◽  
Pierre Montagne ◽  
...  
Keyword(s):  
High Temperature ◽  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Equivalence Ratio ◽  
Process Conditions ◽  
Piping System ◽  
Gaseous Fuels ◽  
Auto Ignition ◽  
Wide Range

Gas turbines burn a large variety of gaseous fuels under elevated pressure and temperature conditions. During transient operations, variable gas/air mixtures are involved in the gas piping system. In order to predict the risk of auto-ignition events and ensure a safe operation of gas turbines, it is of the essence to know the lowest temperature at which spontaneous ignition of fuels may happen. Experimental auto-ignition data of hydrocarbon–air mixtures at elevated pressures are scarce and often not applicable in specific industrial conditions. Auto-ignition temperature (AIT) data correspond to temperature ranges in which fuels display an incipient reactivity, with timescales amounting in seconds or even in minutes instead of milliseconds in flames. In these conditions, the critical reactions are most often different from the ones governing the reactivity in a flame or in high temperature ignition. Some of the critical paths for AIT are similar to those encountered in slow oxidation. Therefore, the main available kinetic models that have been developed for fast combustion are unfortunately unable to represent properly these low temperature processes. A numerical approach addressing the influence of process conditions on the minimum AIT of different fuel/air mixtures has been developed. Several chemical models available in the literature have been tested, in order to identify the most robust ones. Based on previous works of our group, a model has been developed, which offers a fair reconciliation between experimental and calculated AIT data through a wide range of fuel compositions. This model has been validated against experimental auto-ignition delay times corresponding to high temperature in order to ensure its relevance not only for AIT aspects but also for the reactivity of gaseous fuels over the wide range of gas turbine operation conditions. In addition, the AITs of methane, of pure light alkanes, and of various blends representative of several natural gas and process-derived fuels were extensively covered. In particular, among alternative gas turbine fuels, hydrogen-rich gases are called to play an increasing part in the future so that their ignition characteristics have been addressed with particular care. Natural gas enriched with hydrogen, and different syngas fuels have been studied. AIT values have been evaluated in function of the equivalence ratio and pressure. All the results obtained have been fitted by means of a practical mathematical expression. The overall study leads to a simple correlation of AIT versus equivalence ratio/pressure.

CFD Simulation of Humid Air Premixed Flame Combustion Chamber for Evaporative Gas Turbine Cycles

2001 ◽  
Author(s):  
M. Bianco ◽  
S. M. Camporeale ◽  
B. Fortunato
Keyword(s):  
Combustion Chamber ◽  
Equivalence Ratio ◽  
Flame Temperature ◽  
Oxidation Mechanism ◽  
Premixed Flame ◽  
Inlet Temperature ◽  
Nox Emissions ◽  
Humid Air ◽  
Nox Formation ◽  
Operation Conditions

Evaporative cycles, such as Recuperated Water lnjected (RWI) cycle, Humid Air Turbine (HAT) cycle, Cascaded Humidified Advanced Turbine (CHAT) offer the attractive possibility to increase plant efficiency without the use of a steam turbine, necessary for gas-steam combined cycles, appearing, therefore, as an interesting solution for industrial power applications such as electric utilities and independent power producers. It is expected that water addition may contribute to reduce NOx emissions in premixed flame combustors. In order to analyse this solution, a lean-bum combustor, fed with an homogeneous mixture formed by methane and humid air, has been analysed through CFD simulations, in order to predict velocity field, temperatures and emissions. The study has been carried out under the hypothesis of a two-dimensional, axisymmetric combustion chamber assuming, as set of operation conditions, atmospheric pressure, inlet temperature of 650 K, fuel-air equivalence ratio of the methane-air mixture ranging from 0.5 to 0.7 and water-air mass ratio varying from 0% to 5%. In the simulation, the presence of turbulence in the flow has been taken into account using a RNG k-ε model, whilst the chemical behaviour of the system has been described by means of a five-step global reduced mechanism including the oxidation mechanism and the NOx formation mechanism. The analysis of the results shows that the moisture in the premixed flow reduces both NOx and CO emissions at constant equivalence ratio; moreover the lean blow-out limit is shifted toward higher equivalence ratio. The main effect of the water seems to be the increase of the specific heat the mixture which causes a reduction in flame temperature, slowing the chemical reactions responsible of NOx formation. The reasonable agreement has been found between the simulation results concerning NOx emissions and recent experimental results carried out on premixed flamed with humid air. A discussion is also provided about the adopted turbulence models and their influence on the emission results.

Experimental Characterization of the Combustion in Fuel Flexible Humid Power Cycles

2021 ◽  
Author(s):  
Simeon Dybe ◽  
Felix Güthe ◽  
Michael Bartlett ◽  
Panagiotis Stathopoulos ◽  
Christian Oliver Paschereit
Keyword(s):  
Natural Gas ◽  
Equivalence Ratio ◽  
High Efficiency ◽  
Full Potential ◽  
Nox Emissions ◽  
Nox Formation ◽  
Fuel Blend ◽  
Power Cycles ◽  
Wide Range ◽  
Renewable Electricity Generation

Abstract Modified humid power cycles provide the necessary boundary condition for combustion to operate on a wide fuel spectrum in a steam-rich atmosphere comprising hydrogen and syngas from gasification besides natural gas as fuels. Thus, these cycles with their high efficiency and flexibility fit in a carbon-free energy market dominated by renewable electricity generation, providing dispatchable heat and electric power. To realize their full potential, the combustor utilized in such power cycles must fulfill the emission limits as well as demands of stable combustion over a wide range of fuel and steam ratios. The operation is limited by the risk of lean blowout for highly diluted syngas with low reactivity, and flashback for highly reactive hydrogen. Further, the gasification product gas can contain unwanted pollutants such as tars and nitrogen containing species like ammonia (NH3). Tars carry a considerable portion of the feedstock’s energy but are associated with detrimental operational behavior. The presence of ammonia in the combustion increases the risk of high NOx-emission at already small ammonia concentrations in the fuel. In this work, humid hydrogen flames are analyzed for their stability and emissions. Stable hydrogen flames were produced over a wide equivalence ratio and steam ratio range at negligible NOx-emissions. Further, natural gas, and a fuel blend substituting bio-syngas, was doped with ammonia. The combustion is analyzed with a focus on emissions and flame position and stability. The addition of ammonia causes high NOx-formation from fuel bound nitrogen (FBN), which highly increases NOx-emissions. The latter decrease with increasing NH3 content and increasing equivalence ratio.

Performance and Emissions of Drop-in Aviation Biofuels in a Lab Scale Gas Turbine Combustor

2020 ◽  
Author(s):  
Joseph S. Feser ◽  
Ashwani K. Gupta
Keyword(s):  
Gas Turbine ◽  
High Intensity ◽  
Gas Turbines ◽  
Equivalence Ratio ◽  
Fossil Fuels ◽  
Reverse Flow ◽  
Aviation Industry ◽  
Wide Range ◽  
Performance And Emissions ◽  
Aviation Biofuels

Abstract There is a growing need for drop-in biofuels for gas turbines for enhanced energy security and sustainability. Several fuels are currently being developed and tested to reduce dependency on fossil fuels while maintaining performance, particularly in the aviation industry. The transition from traditional fossil fuels to sustainable biofuels is much desired for reducing the rapidly rising CO2 levels in the environment. This requires biofuels to be drop-in ready, where there are no adverse effects on performance and emissions upon replacement. In this study the performance and emissions of four different aviation drop-in biofuels was evaluated. They include: UOP HEFA-SPK, Gevo ATJ, Amyris Farnesane, and SB-JP-8. These aviation biofuels are currently being produced and tested to be ready for full or partial drop-in fuels as the replacement of traditional jet fuels. The characteristic performance of each fuel from the prevaporized liquid fuels was performed in a high intensity (20 MW/m3-atm) reverse flow combustor. The NO emissions showed near unity ppm levels for each of the fuels examined with a minimum at an equivalence ratio of ∼0.6, while CO levels were in the range of 1000–1300 ppm depending on the fuel at an equivalence ratio between 0.75–0.8. For an equivalence ratio range between 0.4 and 0.6, NO and CO emissions remained very low (between 1–2ppm NO and 2400–2900ppm CO) depending on the fuel. The examined biofuels did not show any instability over a wide range of equivalence ratios from lean to near stoichiometric condition. These results provide promising results on the behavior of these drop-in aviation biofuels for use in high intensity gas turbine combustors providing stability and cleaner performance without any modification to the combustor design.

The Nature of NOx Formation Within an Industrial Gas Turbine Dry Low Emission Combustor

2005 ◽  
Author(s):  
Khawar J. Syed ◽  
Eoghan Buchanan
Keyword(s):  
Gas Turbine ◽  
Fluid Dynamic ◽  
Chemical Reactor ◽  
Inlet Temperature ◽  
Nox Formation ◽  
Stirred Reactor ◽  
Low Emission ◽  
Wide Range ◽  
Air Mixing ◽  
Industrial Gas Turbine

The NOx formation within a practical lean premixed gas turbine combustor concept has been investigated. The effects of chemical kinetics and fuel/air mixing have been isolated, by adopting an approach, which combines high pressure combustion testing, CFD and chemical reactor modelling. Given the complexities of the underlying fluid dynamic and chemical processes and their interactions, consistency has been sought between experimental and numerical approaches, prior to drawing any conclusions. Two variants of Siemens Industrial Turbomachinery’s dry low emissions combustor have been investigated, one exhibiting near-ideally premixed combustion over a wide range of combustor pressure drop. Perfectly Stirred Reactor analysis, utilising the GRI 3.0 NOx mechanism, shows that NOx formation is dominated by the N2O and Zeldovich routes, with the N2O route being the larger at flame temperatures below 1800–1900K, for systems operating at 14bars, 400°C inlet temperature and at residence times of interest. Other reactions involving H-N-O chemistry are also significant, however the C-H-N-O chemistry has a negligible impact.

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