Combustion Dynamics Diagnostics and Mitigation on a Prototype Gas Turbine Combustor

2012 ◽  
Author(s):  
Bassam S. Mohammad ◽  
Preetham Balasubramanyam ◽  
Keith McManus ◽  
Jeffrey Ruszczyk ◽  
Ahmed M. Elkady ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Flame Temperature ◽  
Operating Conditions ◽  
Published Data ◽  
Stable Operation ◽  
Nox Emissions ◽  
Gas Turbine Combustor ◽  
Combustion Dynamics ◽  
The Impact ◽  
Intermittent Mode

Combustion dynamics have detrimental effects on hardware durability as well as combustor performance and emissions. This paper presents a detailed study on the impact of combustion dynamics on NOx and CO emissions generated from a prototype gas turbine combustor operating at a pressure of 180 psia (12.2 bars) with a pre-heat temperature of 720 F (655.3 K) (E-class machine operating conditions). Two unstable modes are discussed. The first is an intermittent mode, at 750 Hz, that emerges at flame temperatures near 2900°F (1866.5 K), resulting in high NOx and CO emissions. With increasing fuel flow, NOx and CO emissions continue to increase until the flame temperature reaches approximately 3250°F (2061 K), at which point the second acoustic mode begins to dominate. Flame images indicate that the intermittent mode is associated with flame motion which induces the high NOx and CO emissions. The second mode is also a 750 Hz, but of constant amplitude (no intermittency). Operation in this second 750 Hz mode results in significantly reduced NOx and CO emissions. At pressures higher than 180 psia (12.2 bars), the intermittent mode intensifies, leading to flashback at flame temperatures above 2850°F (1839 K). In order to mitigate the intermittent mode, a second configuration of the combustor included an exit area restriction. The exit area restriction eliminated the intermittent mode, resulting in stable operation and low emissions over a temperature range of 2700–3200°F (1755–2033 K). A comparison of the NOx emissions, as function of flame temperature, with previous published data for perfectly premixed indicates that, while the low amplitude 750 Hz oscillations have little effect, the intermittent mode significantly increases emissions. Mode shape analysis shows that the 750 Hz instability corresponds to the 1/4 wave axial mode. In the current research a ceramic liner is used while the previous published data was collected with a quartz liner. Typically, quartz is avoided due to reductions in effective flame temperature by radiation losses. Experiments showed that NOx emissions were not affected by the combustor liner type. This agreement between the quartz and ceramic liners data indicates limited effect from the radiation heat losses on NOx emissions.

Experimental Study of a Flameless Gas Turbine Combustor

2006 ◽  
Author(s):  
Guoqiang Li ◽  
Ephraim J. Gutmark ◽  
Nick Overman ◽  
Michael Cornwell ◽  
Dragan Stankovic ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Flame Temperature ◽  
Nox Emissions ◽  
Preheat Temperature ◽  
Gas Turbine Combustor ◽  
Flameless Combustion ◽  
Combustion Dynamics ◽  
Flow Rates ◽  
Air Mass ◽  
Chamber Diameter

This paper presents experimental data, performed at atmospheric conditions, on a novel flameless combustor with application to gas turbine engines. Flameless combustion is characterized by distributed flame and even temperature distribution achieved at conditions of high preheat air temperature and sufficiently large amounts of recirculating low oxygen concentration exhaust gases. Extremely low emissions of NOx, CO, and UHC are reported in this paper for flameless combustion in a multiple jets premixed gas turbine combustor. Measurements of the flame chemiluminescence, CO and NOx emissions, acoustic pressure, temperature field, and velocity field reveal the influence of various parameters including: preheat temperature, inlet air mass flow rate, combustor exhaust nozzle contraction ratio, and combustor chamber diameter on emissions and combustion dynamics. The data indicate that greater air mass flow rates, thus larger pressure drop, promotes the formation of flameless combustion and lower NOx emissions for the same flame temperature. This flameless combustor is basically a premixed combustion in which NOx emissions is an exponential function of the flame temperature regardless of different air preheating temperatures. High preheat temperature and flow rates also help in forming stable combustion which is another advantageous feature of flameless combustion. The effects of the combustor exhaust contraction and the combustion chamber diameter on emissions and combustion dynamics are discussed.

Combustion Characteristics of Small Size Gas Turbine Combustor Fueled by Biomass Gas Employing Flameless Combustion

2007 ◽  
Author(s):  
Masato Hiramatsu ◽  
Yoshifumi Nakashima ◽  
Sadamasa Adachi ◽  
Yudai Yamasaki ◽  
Shigehiko Kaneko
Keyword(s):  
Gas Turbine ◽  
Combustion Efficiency ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Gas Turbine Combustor ◽  
Flameless Combustion ◽  
Engine Exhaust ◽  
Micro Gas Turbine

One approach to achieving 99% combustion efficiency (C.E.) and 10 ppmV or lower NOx (at 15%O2) in a micro gas turbine (MGT) combustor fueled by biomass gas at a variety of operating conditions is with the use of flameless combustion (FLC). This paper compares experimentally obtained results and CHEMKIN analysis conducted for the developed combustor. As a result, increase the number of stage of FLC combustion enlarges the MGT operation range with low-NOx emissions and high-C.E. The composition of fuel has a small effect on the characteristics of ignition in FLC. In addition, NOx in the engine exhaust is reduced by higher levels of CO2 in the fuel.

Experimental Assessment of the Emissions Benefits of a Ceramic Gas Turbine Combustor

1996 ◽  
Author(s):  
K. O. Smith ◽  
A. Fahme
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Gas Turbine Combustor ◽  
Experimental Assessment ◽  
Industrial Gas Turbine ◽  
Combustor Liner

Three subscale, cylindrical combustors were rig tested on natural gas at typical industrial gas turbine operating conditions. The intent of the testing was to determine the effect of combustor liner cooling on NOx and CO emissions. In order of decreasing liner cooling, a metal louvre-cooled combustor, a metal effusion-cooled combustor, and a backside-cooled ceramic (CFCC) combustor were evaluated. The three combustors were tested using the same lean-premixed fuel injector. Testing showed that reduced liner cooling produced lower CO emissions as reaction quenching near the liner wall was reduced. A reduction in CO emissions allows a reoptimization of the combustor air flow distribution to yield lower NOx emissions.

scholarly journals Scaling of an Aviation Hydrogen Micromix Injector Design for Industrial GT Combustion Applications

2021 ◽  
Author(s):  
Johannes Berger
Keyword(s):  
Renewable Energy ◽  
Gas Turbine ◽  
Power Plants ◽  
Supply And Demand ◽  
Pressure Ratio ◽  
Flame Temperature ◽  
Orifice Diameter ◽  
Design Parameters ◽  
Nox Emissions ◽  
The Impact

AbstractDecarbonising the energy grid through renewable energy requires a grid firming technology to harmonize supply and demand. Hydrogen-fired gas turbine power plants offer a closed loop by burning green hydrogen produced with excess power from renewable energy. Conventional dry low NOx (DLN) combustors have been optimized for strict emission limits. A higher flame temperature of hydrogen drives higher NOx emissions and faster flame speed alters the combustion behavior significantly. Micromix combustion offers potential for low NOx emissions and optimized conditions for hydrogen combustion. Many small channels, so-called airgates, accelerate the airflow followed by a jet-in-crossflow injection of hydrogen. This leads to short-diffusion flames following the principle of maximized mixing intensity and minimized mixing scales. This paper shows the challenges and the potential of an economical micromix application for an aero-derivative industrial gas turbine with a high-pressure ratio. A technology transfer based on the micromix combustion research in the ENABLEH2 project is carried out. The driving parameter for ground use adaption is an increased fuel orifice diameter from 0.3 mm to 1.0 mm to reduce cost and complexity. Increasing the fuel supply mass flow leads to larger flames and higher emissions. The impact was studied through RANS simulation and trends for key design parameters were shown. Increased velocity in the airgates leads to a higher pressure drop and reduced emissions through faster mixing. Altering the penetration depth shows potential for emission reduction without compromising on pressure loss. Two improved designs are found, and their performance is discussed.

Extension of Fuel Flexibility by Combining Intelligent Control Methods for Siemens SGT-400 Dry Low Emission Combustion System

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Kexin Liu ◽  
Phill Hubbard ◽  
Suresh Sadasivuni ◽  
Ghenadie Bulat
Keyword(s):  
Gas Turbine ◽  
Operating Conditions ◽  
Combustion System ◽  
Combustion Dynamics ◽  
Heating Value ◽  
Fuel Flexibility ◽  
Wide Range ◽  
Wobbe Index ◽  
Industrial Gas Turbine ◽  
The Impact

Extension of gas fuel flexibility of a current production SGT-400 industrial gas turbine combustor system is reported in this paper. A SGT-400 engine with hybrid combustion system configuration to meet a customer's specific requirements was string tested. This engine was tested with the gas turbine package driver unit and the gas compressor-driven unit to operate on and switch between three different fuels with temperature-corrected Wobbe index (TCWI) varying between 45 MJ/m3, 38 MJ/m3, and 30 MJ/m3. The alteration of fuel heating value was achieved by injection or withdrawal of N2 into or from the fuel system. The results show that the engine can maintain stable operation on and switching between these three different fuels with fast changeover rate of the heating value greater than 10% per minute without shutdown or change in load condition. High-pressure rig tests were carried out to demonstrate the capabilities of the combustion system at engine operating conditions across a wide range of ambient conditions. Variations of the fuel heating value, with Wobbe index (WI) of 30 MJ/Sm3, 33 MJ/Sm3, 35 MJ/Sm3, and 45 MJ/Sm3 (natural gas, NG) at standard conditions, were achieved by blending NG with CO2 as diluent. Emissions, combustion dynamics, fuel pressure, and flashback monitoring via measurement of burner metal temperatures, were the main parameters used to evaluate the impact of fuel flexibility on combustor performance. Test results show that NOx emissions decrease as the fuel heating value is reduced. Also note that a decreasing fuel heating value leads to a requirement to increase the fuel supply pressure. Effect of fuel heating value on combustion was investigated, and the reduction in adiabatic flame temperature and laminar flame speed was observed for lower heating value fuels. The successful development program has increased the capability of the SGT-400 standard production dry low emissions (DLE) burner configuration to operate with a range of fuels covering a WI corrected to the normal conditions from 30 MJ/N·m3 to 49 MJ/N·m3. The tests results obtained on the Siemens SGT-400 combustion system provide significant experience for industrial gas turbine burner design for fuel flexibility.

Impact of Secondary Air Flow on Combustor Emissions

2020 ◽  
Author(s):  
Bassam S. Mohammad ◽  
Brian Volk ◽  
Keith McManus
Keyword(s):  
Flame Temperature ◽  
Operating Conditions ◽  
Published Data ◽  
Inlet Temperature ◽  
Combustion System ◽  
Combustion Emissions ◽  
Exit Temperature ◽  
Combustion Systems ◽  
Secondary Air ◽  
The Impact

Abstract It is a common practice to relate emissions performance of Dry Low Emissions (DLE) combustion systems to the flame temperature that is estimated from the mass flows of air and fuel flowing through the premixer. In many combustion systems, the exit temperature (or turbine nozzle inlet temperature) is quite low and is not a good parameter for estimating combustion emissions. The difference between the combustion flame temperature and exit temperature is mainly due to secondary air dilution. To our knowledge there are no detailed published data that quantify the impact of this temperature difference on combustion emissions. The target of this study is to quantify the impact of secondary air variation on emissions, both globally and locally. High pressure experiments are conducted at H class gas turbine operating conditions using a DLE combustion system. In the context of this DLE system, secondary air refers to cooling and leakage flows because direct air dilution of the combustion gasses is not necessary. This is because the flame stabilized downstream of the premixer is well mixed and fuel-lean. With NOx requirements moving toward single digit (ppm) levels, it becomes essential to accurately quantify the impact of reducing the secondary air percentage on emissions performance. In addition to the need to carefully study the impact of local interaction of the secondary air with the flame. The combustion system is configured with two independently controlled mixers along with a variable secondary air circuit that can change the secondary air fraction from 14 to 8%. Multiple emissions rakes are used at the combustor exit to delineate the interaction and relate it to the flame structure. The system is configured to enable sampling from individual rakes to study local emissions and the rakes can be ganged together to measure the bulk-averaged combustion emissions. This research provides a quantification of the improvement of the NOx margin with a decrease in the secondary air percentage. The study shows that the increase in margin is not a simple re-estimate of the combustor emissions using the NOx design curve due to flame quenching effects. The results also show that the secondary air can be used to improve the NOx emissions via controlling the interaction with the primary flame. The impact is quantified in terms of emissions, acoustics and metal temperatures.

scholarly journals The Role of Fuel Preparation in Low Emissions Combustion

1995 ◽  
Author(s):  
A. H. Lefebvre
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Fuel Injection ◽  
Flame Temperature ◽  
Pollutant Emissions ◽  
Alternative Methods ◽  
Nox Emissions ◽  
Oxides Of Nitrogen ◽  
Lean Burn ◽  
The Impact

The attainment of very low pollutant emissions, in particular oxides of nitrogen (NOx), from gas turbines is not only of considerable environmental concern but has also become an area of increasing competitiveness between the different engine manufacturers. For stationary engines, the attainment of ultra-low NOx has become the foremost marketing issue. This paper is devoted primarily to current and emerging technologies in the development of ultra-low emissions combustors for application to aircraft and stationary engines. Short descriptions of the basic design features of conventional gas turbine combustors and the methods of fuel injection now in widespread use are followed by a review of fuel spray characteristics and recent developments in the measurement and modeling of these characteristics. The main gas turbine generated pollutants and their mechanisms of formation are described, along with related environmental risks and various issues concerning emissions regulations and recently-enacted legislation for limiting the pollutant levels emitted by both aircraft and stationary engines. The impact of these emissions regulations on combustor and engine design are discussed first in relation to conventional combustors and then in the context of variable-geometry and staged combustors. Both these concepts are founded on emissions reduction by control of flame temperature. Basic approaches to the design of “dry” low NOx and ultra-low NOx combustors are reviewed. At the present time lean, premix, prevaporize, combustion appears to be the only technology available for achieving ultra-low NOx emissions from practical combustors. This concept is discussed in some detail, along with its inherent problems of autoignition, flashback, and acoustic resonance. Attention is also given to alternative methods of achieving ultra-low NOx emissions, notably the rich-bum, quick-quench, lean-burn and catalytic combustors. These concepts are now being actively developed, despite the formidable problems they present in terms of mixing and durability. The final section reviews the various correlations which are now being used to predict the exhaust gas concentrations of the main gaseous pollutant emissions from gas turbine engines. Comprehensive numerical methods have not yet completely displaced these semi-empirical correlations but are nevertheless providing useful insight into the interactions of swirling and recirculating flows with fuel sprays, as well as guidance to the combustion engineer during the design and development stages. Throughout the paper emphasis is placed on the important and sometimes pivotal role played by the fuel preparation process in the reduction of pollutant emissions from gas turbines.

Development and Operation of a Pressurized Optically-Accessible Research Combustor for Simulation Validation and Fuel Variability Studies

2005 ◽  
Author(s):  
T. Sidwell ◽  
K. Casleton ◽  
D. Straub ◽  
D. Maloney ◽  
G. Richards ◽  
...  
Keyword(s):  
Natural Gas ◽  
Boundary Conditions ◽  
Experimental Testing ◽  
Flame Temperature ◽  
Heat Losses ◽  
Department Of Energy ◽  
Stable Operation ◽  
Pure Hydrogen ◽  
Nox Emissions ◽  
Combustion Dynamics

The U.S. Department of Energy Turbines Program has established very stringent NOx emissions goals of less than 3 ppmv for future turbine power generation. These future turbine power plants may operate on hydrogen-rich fuels, such as coal-derived synthesis gas (syngas), or pure hydrogen derived from shifting the syngas. Achieving these goals is expected to require improved combustor concepts which may be dramatically different than current combustor designs. Significant and costly experimental testing is usually required to assess new combustor concepts. Ideally, new concepts could be evaluated with numeric simulations to reduce development time and cost. However, current simulation capabilities are not sufficient to reliably capture the effects of fuel variations on flame extinction, emissions levels, and dynamic stability. Furthermore, very little data with controlled boundary conditions are available to check numeric predictions at actual turbine engine conditions, or simply to assess combustor performance without ambiguous boundary conditions. This paper presents a description of the development and operation of an optically-accessible research combustor, which is designed to provide fundamental combustion data at elevated pressure and inlet air temperature, and with precisely determined thermal, acoustic, and flow boundary conditions. The effects of fuel composition variations are investigated by blending of controlled quantities of hydrogen with natural gas. Recent test results — emissions data, dynamics data, and heat losses for hydrogen addition from 0 to 40% by fuel volume at two combustor pressures — and a description of future testing are also presented. The results show that the addition of hydrogen to natural gas in percentages as low as 5% of total fuel volume can significantly decrease the lean extinction limit, and promote stable operation at lower equivalence ratios while promoting lower NOx emissions. Dynamic pressures were measured, but combustion dynamics were not present due to the combustor configuration. The effect of heat losses on flame temperature and emissions were quantified.

A New Procedure for Predicting NOx Emission in Preliminary Gas Turbine Combustor Design

2013 ◽  
Author(s):  
Kang Xu ◽  
Suhua Shen ◽  
Chenkai Li ◽  
Lipeng Zheng
Keyword(s):  
Gas Turbine ◽  
Plug Flow ◽  
Chemical Reactor ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Gas Turbine Combustor ◽  
Flow Reactors ◽  
Reactor Networks ◽  
Novel Method ◽  
Simulation Time

A novel method has been developed for predicting flow field by a set of physics-based and empirical equations which provide inputs to a chemical reactor networks (CRN) composed of Perfectly Stirred Reactors (PSR) and Plug Flow Reactors (PFR), allowing rapid and reasonable analysis of NOx emissions. The method is applied to a rectangular section of a gas turbine combustor and the simulation results are compared with experimental results. The CRN has been established and successfully validated for baseline operating conditions. This methodology has shown to be efficient for estimating NOx emissions with a short simulation time (few minutes) and small CPU requirements.

Preliminary Analysis of a New Methodology for Flameless Combustion in Gas Turbine Combustors

2007 ◽  
Author(s):  
Yeshayahou Levy ◽  
G. Arvind Rao ◽  
Valery Sherbaum
Keyword(s):  
Gas Turbine ◽  
Oxygen Concentration ◽  
Combustion Zone ◽  
Flame Temperature ◽  
Carbon Dioxide Concentration ◽  
Operating Conditions ◽  
Gas Turbine Combustor ◽  
Flameless Combustion ◽  
Gas Turbine Combustors ◽  
Wide Range

Flameless combustion is one of the most promising technologies that can meet the stringent demands of reduced pollution and increased reliability in future gas turbine engines. Although this new combustion technology has been successfully applied to industrial furnaces, there are inherent problems that prevent application of this promising technology in a gas turbine combustor. One of the main problems is the need for recirculating large amount of burnt gases with low oxygen content, within limited volume, and over a wide range of operating conditions. In the present paper, thermodynamic analysis of a novel combustion methodology operating in the flameless combustion regime for a gas turbine combustor is carried out from the first principles, with an objective to reduce oxygen concentration and temperature in the primary combustion zone. The present analysis shows that unlike in the conventional gas turbine combustor, transferring heat from primary combustion zone to secondary (annulus) cooling air can substantially reduce oxygen concentration in reactants and the combustion temperature, thus reducing NOx formation by a large margin. In addition, to reduce the peak temperature, the proposed methodology is conceptualised / designed such that energy from fuel is released in two steps, hence reducing the peak flame temperature substantially. The new proposed methodology with internal conjugate heat transfer is compared vis-a`-vis to other existing schemes and the benefits are brought out explicitly. It is found that transferring heat from the combustion zone reduces oxygen concentration and increases carbon-dioxide concentration in the combustor, thus creating an environment conducive for flameless combustion. In addition, a schematic of a practical engineering design working on the new proposed methodology is presented. This new methodology, which calls for transfer of heat from the primary combustion zone to alternative air streams, is expected to change the way gas turbine combustors will be designed in the future.

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