scholarly journals Effect of Pressure, Environment Temperature, Jet Velocity and Nitrogen Dilution on the Liftoff Characteristics of a N2-in-H2 Jet Flame in a Vitiated Co-flow

2014 ◽  
Vol 16 (2-3) ◽  
pp. 141 ◽  
Author(s):  
A. North ◽  
M. Magar ◽  
J.-Y. Chen ◽  
R. Dibble ◽  
A. Gruber
Keyword(s):  
Gas Turbines ◽  
Operating Conditions ◽  
Flame Stability ◽  
High Hydrogen ◽  
Jet Flame ◽  
Environment Temperature ◽  
Nitrogen Dilution ◽  
Air Mixing ◽  
Partially Premixed ◽  
Jet Velocity

<p>The CO<sub>2</sub> emission prevention advantage of generating power with high hydrogen content fuels using gas turbines motivates an improved understanding of the ignition behavior of hydrogen in premixed and partially premixed environments. Hydrogen rich fueled flame stability is sensitive to operating conditions, including environment pressure, temperature, and jet velocity. Furthermore, when premixed or partially premixed operation is needed for nitric oxide emissions reduction, a diluent, such as nitrogen, is often added in allowing fuel/air mixing prior to combustion. Thus, the concentration of the diluent added is an additional independent variable on which flame stability dependence is needed. The focus of this research is on characterizing the dependence of hydrogen jet flame stability on environment temperature, pressure, jet velocity and diluent concentration by determining the dependence of the liftoff height of lifted flames on these 4 independent parameters. Nitrogen is used as the diluent due to its availability and effectiveness in promoting liftoff. A correlation modeling the liftoff height dependence on operating conditions is developed which emphasizes the factors that bear the greatest impact on ignition behavior.</p>

Stability and Liftoff of a N2-in-H2 Jet Flame in a Vitiated Co-flow at Atmospheric Pressure

2014 ◽  
Vol 16 (2-3) ◽  
pp. 129 ◽  
Author(s):  
A. North ◽  
D. Frederick ◽  
J.-Y. Chen ◽  
R. Dibble ◽  
A. Gruber
Keyword(s):  
Flame Propagation ◽  
Equivalence Ratio ◽  
Jet Flame ◽  
Environment Temperature ◽  
Flow Equivalence ◽  
Nitrogen Dilution ◽  
Height Dependence ◽  
Jet Velocity ◽  
The Stability ◽  
Stability Regime

<p>The stability and liftoff characteristics of a nitrogen (N<sub>2</sub>) diluted hydrogen (H<sub>2</sub>) jet flame in a vitiated co-flow are investigated experimentally with particular attention focused on regimes where multiple stabilization mechanisms are active. Information gleaned from this research is instrumental for informing modeling approaches in flame transition situations when both autoignition and flame propagation influence combustion characteristics. Stability regime diagrams which outline the conditions under which the flame is attached, lifted, blown-out, and unsteady are experimentally developed and explored. The lifted regime is further characterized in determining liftoff height dependence on N<sub>2</sub> dilution, jet velocity, and co-flow equivalence ratio (or essentially, co-flow temperature). A strong sensitivity of liftoff height to N<sub>2</sub> dilution, jet velocity, and co-flow equivalence ratio is observed. Liftoff heights predicted by Kalghatgi’s correlation are unable to capture the effects of N<sub>2</sub> dilution on liftoff height for the heated co-flow cases. A uniquely formulated Damköhler number, where the chemical time scale is based on flame propagation rather than autoignition, was therefore developed which acceptably captures the effects of jet velocity, nitrogen dilution and environment temperature on liftoff height. Satisfactory agreement between the correlation results indicate that stabilization is dominated by propagation, and prior studies with similar flames, such as the research of Muñiz and Mungal (1997) indicate that the propagating flame is likely tribrachial.</p>

Investigation on Flowfield and Fuel/Air Premixing Uniformities of Low Swirl Injector for Lean Premixed Gas Turbines

2021 ◽  
Author(s):  
Fujun Sun ◽  
Jianqin Suo ◽  
Zhenxia Liu
Keyword(s):  
Penetration Depth ◽  
Residence Time ◽  
Gas Turbines ◽  
Structural Parameters ◽  
Combustible Mixture ◽  
Operating Conditions ◽  
Flame Stability ◽  
Nox Emissions ◽  
Auto Ignition ◽  
Lean Premixed

Abstract Based on the development trend of incorporating fuel holes into swirler-vanes and the advantages of wide operating conditions as well as low NOx emissions of LSI, this paper proposes an original lean premixed LSI with a convergent outlet. The influence of key structures on flowfields and fuel/air premixing uniformities of LSI is investigated by the combination of laser diagnostic experiments and numerical simulations. The flowfields of LSI shows that the main recirculation zone is detached from the convergent outlet and its axial dimensions are smaller than that of HSI, which can decrease the residence time of high-temperature gas to reduce NOx emissions. The fuel/air premixing characteristics show that the positions and diameters of fuel holes affect fuel/air premixing by changing the penetration depth of fuel. And when the penetration depth is moderate, it can give full play to the role of swirling air in enhancing premixing of fuel and air. In addition, the increase of the length of the premixing section can improve the uniformity of fuel/ar premixing, but it can also weaken the swirl intensity and increase the residence time of the combustible mixture within the LSI, which can affect flame stability and increase the risk of auto-ignition. Therefore, the design and selection of LSI structural parameters should comprehensively consider the requirements of fuel/air mixing uniformity, flame stability and avoiding the risk of auto-ignition. The results can provide the technical basis for LSI design and application in aero-derivative and land-based gas turbine combustors.

Effect of Fuel Composition on Emissions From a Low-Swirl Burner

2007 ◽  
Author(s):  
Daniel Sequera ◽  
Ajay K. Agrawal
Keyword(s):  
Gas Turbines ◽  
Bluff Body ◽  
Swirling Flow ◽  
Flame Temperature ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Recirculation Region ◽  
Fuel Composition ◽  
High Hydrogen ◽  
Flow Recirculation

Lean Premixed Combustion (LPM) is a widely used approach to effectively reduce pollutant emissions in advanced gas turbines. Most LPM combustion systems employ the swirling flow with a bluff body at the center to stabilize the flame. The flow recirculation region established downstream of the bluff-body brings combustion products in contact with fresh reactants to sustain the reactions. However, such systems are prone to combustion oscillations and flame flashback, especially if high hydrogen containing fuels are used. Low-Swirl Injector (LSI) is an innovative approach, whereby a freely propagating LPM flame is stabilized in a diverging flow field surrounded by a weakly-swirling flow. The LSI is devoid of the flow recirculation region in the reaction zone. In the present study, emissions measurements are reported for a LSI operated on mixtures of methane (CH4), hydrogen (H2), and carbon monoxide (CO) to simulate H2 synthetic gas produced by coal gasification. For a fixed adiabatic flame temperature and air flow rate, CH4 content of the fuel in atmospheric pressure experiments is varied from 100% to 50% (by volume) with the remainder of the fuel containing equal amounts of CO and H2. For each test case, the CO and nitric oxide (NOx) emissions are measured axially at the combustor center and radially at several axial locations. Results show that the LSI provides stable flame for a range of operating conditions and fuel mixtures. The emissions are relatively insensitive to the fuel composition within the operational range of the present experiments.

Development of Low Emission Gas Turbine Combustors

2015 ◽  
Author(s):  
Seung-chai Jung ◽  
Siwon Yang ◽  
Shaun Kim ◽  
Ik Soo Kim ◽  
Chul-ju Ahn ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Flow Characteristics ◽  
Flame Stability ◽  
Fuel Distribution ◽  
Eddy Simulation ◽  
Piv Measurement ◽  
Planar Laser ◽  
Air Mixing ◽  
Industrial Gas Turbines ◽  
Combustion Tests

Due to increasing environmental concerns, clean technology has become a key feature in industrial gas turbines. Swirler design is directly associated with the combustion performance for its roles in fuel distribution and flame stability. In this study, the development process of three new conceptual swirlers from Samsung Techwin is presented. Each swirler has unique features to enhance fuel-to-air mixing; Swirler 1 uses tangential air-bypass, Swirler 2 minimizes pressure loss using impeller-like design, and Swirler 3 has combined flow characteristics of axial and radial swirlers. Using extensive computational fluid dynamics (CFD) analysis, lead time and cost in manufacturing the prototypes were significantly reduced. The numerical methods were verified with a lab-scale combustion test; particle image velocimetry (PIV) measurement of cold flow, direct flame images, and OH planar laser induced fluorescence (PLIF) images were compared with result of large-eddy simulation (LES), and they showed good agreement. After design optimization using CFD, full-scale combustion tests were performed for all three swirlers. Flame from each swirler was visualized using a cylindrical quartz liner; direct images and OH chemiluminescence images of flames were obtained. Flame stability and blow-off limit at various air load were examined by gradually lowering the equivalence ratio. NOx and CO concentration were measured at the exhaust. All three swirlers satisfied low NOx and CO levels at the design conditions. The performance maps bounded by the NOx and CO limits and blow-off limit were obtained for all swirlers. Further efforts to maximize the combustors performance will be made.

Evaluation of a Turbulent Jet Flame Flashback Correlation Applied to Annular Flow Configurations with and Without Swirl

2020 ◽  
Author(s):  
Elliot Sullivan Lewis ◽  
Vincent McDonell ◽  
Alireza Kalantari ◽  
Priyank Saxena
Keyword(s):  
Hydrogen Content ◽  
Gas Turbines ◽  
Annular Flow ◽  
Jet Flames ◽  
High Hydrogen ◽  
Jet Flame ◽  
High Hydrogen Content ◽  
Round Jet ◽  
Significant Difference ◽  
Flow Configurations

Abstract The adaptation of high hydrogen content fuels for low emissions gas turbines represents a potential opportunity to reduce the carbon footprint of these devices. The high flame speed of hydrogen air mixtures combined with the small quenching distances poses a challenge for using these fuels in situations where significant premixing is desired. Flashback along the walls (i.e., boundary layer flashback) can be exacerbated with high hydrogen content fuels. In the present work, the ability of a flashback correlation previously developed for round jet flames is evaluated for its ability to predict flashback in an annular flow with and without swirl. Flashback data are obtained for various mixtures of hydrogen and methane and hydrogen and carbon monoxide for all the annular flow configurations. Pressures from 3-8 bar are tested with mixture temperatures up to 750 K. Flashback is induced by slowly increasing the equivalence ratio. The results obtained show that the same form of the correlation developed for round jet flames can be used to correlate flashback behavior for the annular flow case with and without swirl despite the presence of the centerbody. Adjustments to some of the constants in the original model were made to obtain the best fit, but in general, the correlation is quite similar to that developed for the round jet flame. A significant difference with the annular flow configurations is the determination of the appropriate gradient at the wall, which in the present case is determined using a cold flow CFD simulation.

The Degradation Simulation of Compressor Salt Fog Fouling for Marine Gas Turbine

2017 ◽  
Author(s):  
Yunpeng Cao ◽  
Lie Chen ◽  
Jianwei Du ◽  
Fang Yu ◽  
Qingcai Yang ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Cost Estimation ◽  
Gas Turbines ◽  
Operating Cost ◽  
Operating Time ◽  
Performance Degradation ◽  
Operating Conditions ◽  
Degradation Factor ◽  
Environment Temperature ◽  
Salt Fog

When a gas turbine operates in a marine environment, gradual performance degradation occurs due to salt fog in the compressor and turbine. Regular water washing of a gas turbine can effectively restore the performance loss caused by compressor salt fog fouling on the flow passage. However, inappropriate washing will increase maintenance costs, cause unnecessary down time and premature erosion of leaf surfaces. In this paper, a coefficient matching method for a three shaft marine gas turbine salt fog fouling degradation factor model is proposed, which can establish a model of salt fog fouling degradation factor according to a change in operating time and exhaust temperature in the washing cycle. The influences of load, environment temperature, inlet pressure loss and salt fog fouling rate on the performance degradation of the gas turbine are simulated and analyzed; then, the degradation regularity of the performance parameters of the gas turbine under different operating conditions and fouling degrees is obtained. Finally, a method of operating cost estimation for marine gas turbines is proposed that can estimate the cost of transient change and cumulative change in the cleaning cycle caused by the salt fog fouling, which can help the operator to determine the cleaning strategy and reduce the operation cost of the gas turbine.

Advanced Gas Turbine Combustion System Development for High Hydrogen Fuels

2007 ◽  
Author(s):  
Jianfan Wu ◽  
Phillip Brown ◽  
Ihor Diakunchak ◽  
Anil Gulati ◽  
Martin Lenze ◽  
...  
Keyword(s):  
Gas Turbines ◽  
System Development ◽  
Low Cost ◽  
Cost Effective ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Combustion System ◽  
High Hydrogen ◽  
Operating Range ◽  
Hydrogen Fuels

Integrated Gasification Combined Cycle (IGCC) technology makes possible the utilization of low cost coal and opportunity fuels, such as petroleum coke, residual oil and biomass, for clean efficient and cost effective electricity generation. Siemens is a leading supplier of products and services for IGCC plants and it is adapting its most advanced gas turbines for successful integration into IGCC plants. To expedite this, Siemens is pursuing combustion system development for application in IGCC plants operating on syngas/hydrogen fuels. Detailed combustion system testing has been carried out during 2005 and 2006 on syngas/hydrogen fuels derived from different feed stocks and gasification processes. The test programs addressed both the F- and G-Class firing temperatures and operating conditions. Fuel transfer capability to and from natural gas, which is the startup and backup fuel, and syngas was explored over the operating range. Optimization studies were carried out with different diluent (H2O and N2) addition rates to determine the effect on emissions and operability. The focus of this development was to ensure that only combustion system modifications would be required for successful enriched hydrogen syngas fuel operation. This paper summarizes the results from the Siemens combustion system development programs to demonstrate that low emissions and wide engine operating range can be achieved on hydrogen fuel operation in advanced 50 Hz and 60 Hz gas turbines in IGCC applications with carbon dioxide capture.

Evaluation of a Turbulent Jet Flame Flashback Correlation Applied to Annular Flow Configurations With and Without Swirl

2020 ◽  
Author(s):  
E. Sullivan Lewis ◽  
Vincent G. McDonell ◽  
Alireza Kalantari ◽  
Priyank Saxena
Keyword(s):  
Hydrogen Content ◽  
Gas Turbines ◽  
Annular Flow ◽  
Jet Flames ◽  
High Hydrogen ◽  
Jet Flame ◽  
High Hydrogen Content ◽  
Round Jet ◽  
Significant Difference ◽  
Flow Configurations

Abstract The adaptation of high hydrogen content fuels for low emissions gas turbines represents a potential opportunity to reduce the carbon footprint of these devices. The high flame speed of hydrogen air mixtures combined with the small quenching distances poses a challenge for using these fuels in situations where significant premixing is desired. In particular flashback in either the core flow or along the walls (i.e., boundary layer flashback) can be exacerbated with high hydrogen content fuels. In the present work, the ability of a flashback correlation previously developed for round jet flames is evaluated for its ability to predict flashback in an annular flow. As a first step, an annular flow is generated with a centerbody located at the centerline of the original round jet flame. Next, various levels of axial swirl is added to that annular flow. Additional flashback data are obtained for various mixtures of hydrogen and methane and hydrogen and carbon monoxide for all-the annular flow configurations. Pressures from 3–8 bar are tested with mixture temperatures up to 750 K. Flashback is induced by slowly increasing the equivalence ratio. The results obtained show that the same form of the correlation developed for round jet flames can be used to correlate flashback behavior for the annular flow case with and without swirl despite the presence of the centerbody. Adjustments to some of the constants in the original model were made to obtain the best fit, but in general, the correlation is quite similar to that developed for the round jet flame. A significant difference with the annular flow configurations is the determination of the appropriate gradient at the wall, which in the present case is determined using a cold flow CFD simulation.

Testing of a Hydrogen Dilute Diffusion Array Injector at Gas Turbine Conditions

2011 ◽  
Author(s):  
Nathan T. Weiland ◽  
Todd G. Sidwell ◽  
Peter A. Strakey
Keyword(s):  
Pressure Drop ◽  
Gas Turbine ◽  
Residence Time ◽  
Firing Temperature ◽  
Gas Turbines ◽  
Advanced Technology ◽  
Nox Emissions ◽  
High Hydrogen ◽  
Air Jet ◽  
Nitrogen Dilution

The U.S. Department of Energy’s Turbines Program is developing advanced technology for high-hydrogen gas turbines to enable integration of carbon sequestration technology into coal-gasifying power plants. Program goals include aggressive reductions in gas turbine NOx emissions: less than 2 ppmv NOx at 15% oxygen and 1750 K firing temperature. The approach explored in this work involves nitrogen dilution of hydrogen diffusion flames, which avoids problems with premixing hydrogen at gas turbine pressures and temperatures. Thermal NOx emissions are partially reduced through peak flame temperature control provided by nitrogen dilution, while further reductions are attained by minimizing flame size and residence time. The injector design includes high-velocity coaxial air injection from lobes surrounding the central fuel tube in each of the 48 array units. This configuration strikes a balance between stability and ignition performance, combustor pressure drop, and flame residence time. Array injector test conditions in the optically accessible Low Emissions Combustor Test & Research (LECTR) facility include air preheat temperatures of 500 K, combustor pressures of 4, 8 and 16 atm, equivalence ratios of 0.3 to 0.7, and three hydrogen/nitrogen fuel blend ratios. Test results show that NOx emissions increase with pressure and decrease with increasing fuel and air jet velocities, as expected. The magnitude of these emissions changes deviate from expected NOx scaling relationships, however, due to active combustor cooling and array spacing effects. At 16 atm and 1750 K firing temperature, the lowest NOx emissions obtained is 4.4 ppmv at 15% O2 equivalent (3.0 ppmv if diluent nitrogen is not considered), with a corresponding pressure drop of 7.7%. While these results demonstrate that nitrogen dilution in combination with high strain rates provides a reliable solution to low NOx hydrogen combustion at gas turbine conditions, the injector’s performance can still be improved significantly through suggested design changes.

Stratified and hydrogen combustion techniques for higher turndown and lower emissions in gas turbines

2021 ◽  
pp. 1-42
Author(s):  
Medhat A. Nemitallah ◽  
Md Azazul Haque ◽  
Muzafar Hussain ◽  
Ahmed Abdelhafez ◽  
Mohamed A. Habib
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Hydrogen Gas ◽  
Operating Conditions ◽  
Flame Stability ◽  
Nox Emissions ◽  
Complete Combustion ◽  
Complete Control ◽  
Low Load ◽  
Combustion Technique

Abstract This review overviews combustion technologies for reduced emissions and better fuel economy in industrial gas turbine. Lean premixed combustion (LPM) technology is introduced as a low-temperature combustion technique to control NOx emissions. The Dry Low NOx (DLN) is one of the most promising LPM-based combustors for controlling NOx emissions. However, DLN combustors suffer from limited flame stability, especially under low load (near blowout) operating conditions, in addition to the difficulty of separating CO2 from the exhaust stream for reducing the gas-turbine carbon footprint. Trying to overcome such difficulties, the gas turbine manufacturers developed enhanced-design burners for higher turndown and lower NOx emissions, including the Dual Annular Counter Rotating Swirl (DACRS) and environmental-Vortex (EV) burners. The volume of the DACRS combustors is almost twice the conventional burners, which provide ample residence time for complete combustion. The mixing effectiveness is improved in EV-burners resulting in higher flame stability at low load or startup conditions. To widen the operability, control the emissions, and improve the turndown ratio of gas turbine combustors, the concept of flame stratification, i.e., heterogenization of the overall equivalence ratio, was introduced. This technique can widen the stability range of existing LPM flames for industrial applications. Integrating stratified combustion technique with oxy-fuel combustion technology is a way forward that may result in complete control of gas turbine emissions with higher operability turndown ratio. The recent developments and challenges towards the application of hydrogen gas turbine are introduced.

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