scholarly journals Flame Ionization Sensor Integrated Into a Gas Turbine Fuel Nozzle

2005 ◽  
Vol 127 (1) ◽  
pp. 42-48 ◽  
Author(s):  
Kelly Benson ◽  
Jimmy D. Thornton ◽  
Douglas L. Straub ◽  
E. David Huckaby ◽  
Geo. A. Richards
Keyword(s):  
Gas Turbine ◽  
Low Cost ◽  
Stability Margin ◽  
Thermodynamic Efficiency ◽  
Flame Stability ◽  
Fuel Quality ◽  
Widespread Application ◽  
Combustion Dynamics ◽  
Flame Ionization ◽  
Fuel Nozzle

Recent advances in lean premix gas turbine combustion have focused primarily on increasing thermodynamic efficiency, reducing emissions, and minimizing combustion dynamics. The practical limitation on increasing efficiency at lower emissions is the onset of combustion instability, which is known to occur near the lean flammability limit. In a laboratory environment there are many sensors available that provide the combustion engineer with adequate information about flame stability, but those sensors are generally too expensive or unreliable for widespread application in the field. As a consequence, engines must be commissioned in the field with adequate stability margin such that normally expected component wear, fuel quality, and environmental conditions will not cause the turbine to experience unstable combustion. Woodward Industrial Controls, in cooperation with the National Energy Technology Laboratory, is developing a novel combustion sensor that is integrated into the fuel nozzle such that low cost and long life are achieved. The sensor monitors flame ionization, which is indicative of air–fuel ratio and most importantly flame stability.

scholarly journals Flame Ionization Sensor Integrated Into Gas Turbine Fuel Nozzle

2003 ◽  
Author(s):  
Kelly Benson ◽  
Jimmy D. Thornton ◽  
Douglas L. Straub ◽  
E. David Huckaby ◽  
Geo. A. Richards
Keyword(s):  
Gas Turbine ◽  
Low Cost ◽  
Stability Margin ◽  
Thermodynamic Efficiency ◽  
Flame Stability ◽  
Fuel Quality ◽  
Widespread Application ◽  
Combustion Dynamics ◽  
Flame Ionization ◽  
Fuel Nozzle

Recent advances in lean premix gas turbine combustion have focused primarily on increasing thermodynamic efficiency, reducing emissions, and minimizing combustion dynamics. The practical limitation on increasing efficiency at lower emissions is the onset of combustion instability, which is known to occur near the lean flammability limit. In a laboratory environment there are many sensors available which provide the combustion engineer with adequate information about flame stability, but those sensors are generally too expensive or unreliable for widespread application in the field. As a consequence, engines must be commissioned in the field with adequate stability margin such that normally expected component wear, fuel quality, and environmental conditions will not cause the turbine to experience unstable combustion. Woodward, in cooperation with NETL, is developing a novel combustion sensor which is integrated into the fuel nozzle such that low cost and long life are achieved. The sensor monitors flame ionization, which is indicative of air-fuel ratio, and most importantly flame stability.

Combustion Oscillation Monitoring Using Flame Ionization in a Turbulent Premixed Combustor

2006 ◽  
Vol 129 (2) ◽  
pp. 352-357 ◽  
Author(s):  
B. T. Chorpening ◽  
J. D. Thornton ◽  
E. D. Huckaby ◽  
K. J. Benson
Keyword(s):  
Standard Deviation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Dynamic Pressure ◽  
Pressure Oscillation ◽  
Chamber Pressure ◽  
Ion Distribution ◽  
Combustion Dynamics ◽  
Gas Turbine Combustors ◽  
Flame Ionization

To achieve very low NOx emission levels, lean-premixed gas turbine combustors have been commercially implemented that operate near the fuel-lean flame extinction limit. Near the lean limit, however, flashback, lean blow off, and combustion dynamics have appeared as problems during operation. To help address these operational problems, a combustion control and diagnostics sensor (CCADS) for gas turbine combustors is being developed. CCADS uses the electrical properties of the flame to detect key events and monitor critical operating parameters within the combustor. Previous development efforts have shown the capability of CCADS to monitor flashback and equivalence ratio. Recent work has focused on detecting and measuring combustion instabilities. A highly instrumented atmospheric combustor has been used to measure the pressure oscillations in the combustor, the OH emission, and the flame ion field at the premix injector outlet and along the walls of the combustor. This instrumentation allows examination of the downstream extent of the combustion field using both the OH emission and the corresponding electron and ion distribution near the walls of the combustor. In most cases, the strongest pressure oscillation dominates the frequency behavior of the OH emission and the flame ion signals. Using this highly instrumented combustor, tests were run over a matrix of equivalence ratios from 0.6 to 0.8, with an inlet reference velocity of 25m∕s(82ft∕s). The acoustics of the fuel system for the combustor were tuned using an active-passive technique with an adjustable quarter-wave resonator. Although several statistics were investigated for correlation with the dynamic pressure in the combustor, the best correlation was found with the standard deviation of the guard current. The data show a monotonic relationship between the standard deviation of the guard current (the current through the flame at the premix injector outlet) and the standard deviation of the chamber pressure. Therefore, the relationship between the standard deviation of the guard current and the standard deviation of the pressure is the most promising for monitoring the dynamic pressure of the combustor using the flame ionization signal. This addition to the capabilities of CCADS would allow for dynamic pressure monitoring on commercial gas turbines without a pressure transducer.

Combustion Oscillation Monitoring Using Flame Ionization in a Turbulent Premixed Combustor

2004 ◽  
Author(s):  
B. T. Chorpening ◽  
J. D. Thornton ◽  
E. D. Huckaby ◽  
K. J. Benson
Keyword(s):  
Standard Deviation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Dynamic Pressure ◽  
Pressure Oscillation ◽  
Chamber Pressure ◽  
Ion Distribution ◽  
Combustion Dynamics ◽  
Gas Turbine Combustors ◽  
Flame Ionization

To achieve very low NOx emission levels, lean-premixed gas turbine combustors have been commercially implemented which operate near the fuel-lean flame extinction limit. Near the lean limit, however, flashback, lean blowoff, and combustion dynamics have appeared as problems during operation. To help address these operational problems, a combustion control and diagnostics sensor (CCADS) for gas turbine combustors is being developed. CCADS uses the electrical properties of the flame to detect key events and monitor critical operating parameters within the combustor. Previous development efforts have shown the capability of CCADS to monitor flashback and equivalence ratio. Recent work has focused on detecting and measuring combustion instabilities. A highly instrumented atmospheric combustor has been used to measure the pressure oscillations in the combustor, the OH emission, and the flame ion field at the premix injector outlet and along the walls of the combustor. This instrumentation allows examination of the downstream extent of the combustion field using both the OH emission and the corresponding electron and ion distribution near the walls of the combustor. In most cases, the strongest pressure oscillation dominates the frequency behavior of the OH emission and the flame ion signals. Using this highly instrumented combustor, tests were run over a matrix of equivalence ratios from 0.6 to 0.8, with an inlet reference velocity of 25 m/s. The acoustics of the fuel system for the combustor were tuned using an active-passive technique with an adjustable quarter-wave resonator. Although several statistics were investigated for correlation with the dynamic pressure in the combustor, the best correlation was found with the standard deviation of the guard current. The data show a monotonic relationship between the standard deviation of the guard current (the current through the flame at the premix injector outlet) and the standard deviation of the chamber pressure. Therefore, the relationship between the standard deviation of the guard current and the standard deviation of the pressure is the most promising for monitoring the dynamic pressure of the combustor using the flame ionization signal. This addition to the capabilities of CCADS would allow for dynamic pressure monitoring on commercial gas turbines without a pressure transducer.

Design and Performance of Low Heating Value Fuel Gas Turbine Combustors

1996 ◽  
Author(s):  
Robert A. Battista ◽  
Alan S. Feitelberg ◽  
Michael A. Lacey
Keyword(s):  
Gas Turbine ◽  
Coal Gasification ◽  
Combined Cycle ◽  
Flame Stability ◽  
Load Range ◽  
Fuel Gas ◽  
Heating Value ◽  
Gas Turbine Combustors ◽  
Fuel Nozzle ◽  
Combustor Liner

General Electric Company is developing and testing low heating value fuel gas turbine combustors for use in integrated gasification combined cycle power generation systems. This paper presents the results of a series of combustion tests conducted at the pilot scale coal gasification and high temperature desulfurization system located at GE Corporate Research and Development in Schenectady, New York. Tests were performed in a modified GE MS6000 combustor liner operating at a pressure of 10 bar and over a wide load range (combustor exit temperatures from 760 to 1400°C). The primary objective of these tests was to compare and contrast the performance (emissions, flame stability, and combustor liner temperatures) of six different low heating value fuel nozzle designs, representing three distinct nozzle concepts. With 2200 to 4600 ppmv NH3 in the fuel, the conversion of fuel NH3 to NOx was roughly independent of fuel nozzle type, and ranged from about 70% at low combustor exit temperatures to about 20% at high combustor exit temperatures. For all of the fuel nozzles, CO emissions were typically less than 5 ppmv (on a dry, 15% O2 basis) at combustor exit temperatures greater than 980°C. Significant differences in CO emissions were observed at lower combustor exit temperatures. Some differences in liner temperatures and flame stability were also observed with the different nozzles. In general, nozzles which produced lower CO emissions and greater flame stability had higher fuel swirl angles and resulted in higher combustor liner temperatures. The nozzle with the best overall performance (consisting of concentric axial air and fuel swirlers and an air cooled mixing cup) has been selected for use at a commercial site.

Detection of Lean Blowout and Combustion Dynamics Using Flame Ionization

2005 ◽  
Author(s):  
B. T. Chorpening ◽  
D. L. Straub ◽  
E. D. Huckaby ◽  
K. J. Benson
Keyword(s):  
Environmental Conditions ◽  
Equivalence Ratio ◽  
In Situ Monitoring ◽  
Fuel Quality ◽  
Combustion Control ◽  
Stability Boundaries ◽  
Combustion Dynamics ◽  
Lean Blowout ◽  
Flame Ionization ◽  
Lean Premixed

The implementation of sophisticated combustion control schemes in modern gas turbines is motivated by the desire to maximize thermodynamic efficiency while meeting NOx emission restrictions. To achieve target NOx levels, modern turbine combustors must operate with a finely controlled fuel-air ratio near the fuel-lean flame extinction limit, where the combustor is most susceptible to instabilities. In turbine configurations with multiple combustors arranged around the annulus, differences in flow splits caused by manufacturing variations or engine wear can compromise engine performance. Optimal combustion control is also complicated by changes in environmental conditions, fuel quality, or fuel type. As a consequence, engines must be commissioned in the field with adequate stability margin such that manufacturing tolerances, normally expected component wear, fuel quality, and environmental conditions will not cause unstable combustion. A lack of robust combustion in-situ monitoring has limited the ability of modern turbines to achieve stable ultra-low emission performance over the entire load range. Of particular concern is the avoidance of lean blowout (LBO) and combustion dynamics. To minimize combustion temperature and NOx production, it is necessary to approach the LBO boundary. This paper describes continuing work on incipient lean blowout detection using flame ionization, investigating the impact of three different piloting and equivalence ratio reduction strategies applied in a pressurized, lean premixed combustor. This work builds upon previous research in the development of the Combustion Control and Diagnostic Sensor (CCADS). In previous papers, the detection of flashback, equivalence ratio, combustion dynamics, and lean blowout using CCADS has been investigated and described. Previous investigation of lean blowout, however, has been limited to a side pilot configuration. In this paper, lean blowout behavior for a side pilot and a centerbody tip pilot are compared. In addition, two different methods for decreasing equivalence ratio to approach LBO are investigated. These cases are found to have differing lean blowout behavior, and differing CCADS signatures. This paper also reports on the ion signal behavior due to combustion dynamics observed during the equivalence ratio sweeps, including passing through stability boundaries. Tests were performed at 5 atm using an industrial style, lean premixed combustor nozzle, equipped with CCADS electrodes, in a water-cooled, natural gas fueled, acoustically noisy combustor. Testing included sweeps of equivalence ratio from 0.65 to 0.45, crossing one or more stability boundaries. LBO was approached for configurations with a side pilot (on the inlet wall of the combustor, but set away from the premixer) and a centerbody tip pilot. The centerbody tip pilot and the side pilot both helped stabilize combustion, but combustion dynamics still occurred. Incipient LBO was apparent in all cases; however, the different flame structure encountered with each pilot configuration and fuel control strategy made the flame ionization signature differ for each case.

Shear Layer Mixing for Low Emission Gas Turbine Primary Zones

1984 ◽  
Author(s):  
N. A. Al-Dabbagh ◽  
G. E. Andrews ◽  
R. Manorharan
Keyword(s):  
Shear Layer ◽  
Gas Turbine ◽  
Fuel Injection ◽  
Flame Temperature ◽  
Stability Margin ◽  
Air Injection ◽  
Flame Stability ◽  
Nox Emissions ◽  
Primary Zone ◽  
Air Mixing

Shear layer turbulent fuel and air mixing has been utilised in a simulated gas turbine primary zone combustor. Two methods of fuel injection and two values of the number of air injection holes have been investigated at a constant pressure loss of 4% at a reference Mach number of 0.047. The method of fuel injection and the number of air injection holes was found to influence the flame stability and NOx emissions. A large number of holes produced much higher NOx emissions which was not compensated for by the ability to operate at weaker equivalence ratios due to the greater flame stability. An optimum primary zone operating condition, for very low NOx and high combustion efficiencies involving a flame temperature of approximately 1600K was identified and there was a wide flame stability margin on this condition.

Flame Ionization Distribution and Dynamics Monitoring in a Turbulent Premixed Combustor

2006 ◽  
Author(s):  
B. T. Chorpening ◽  
E. D. Huckaby ◽  
M. L. Morris ◽  
J. D. Thornton ◽  
K. J. Benson
Keyword(s):  
Standard Deviation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Control Technique ◽  
Operating Parameters ◽  
Pressure Oscillations ◽  
Combustion Dynamics ◽  
Gas Turbine Combustors ◽  
Flame Ionization ◽  
Flame Emission

To achieve very low NOx emission levels, lean-premixed gas turbine combustors have been commercially implemented which operate near the fuel-lean flame extinction limit. Near the lean limit, however, flashback, lean blowoff, and combustion dynamics have appeared as problems during operation. To help address these operational problems, a combustion control and diagnostics sensor (CCADS) for gas turbine combustors is being developed. CCADS uses the electrical properties of the flame to detect key events and monitor critical operating parameters within the combustor. Previous development efforts have shown the capability of CCADS to monitor flashback and equivalence ratio, and progress has been made on detecting and measuring combustion instabilities. In support of this development, a highly instrumented atmospheric combustor has been used to measure the pressure oscillations in the combustor, the ultraviolet flame emission, and the flame ion field at the premix injector outlet and along the walls of the combustor. This instrumentation allows examination of the downstream extent of the combustion field using both the ultraviolet (mostly OH*) emission and the corresponding electron and ion distribution near the walls of the combustor. During testing the combustion dynamics were controlled using a fuel feed impedance control technique. This provided flame ionization measurements for both steady and unsteady combustion, without changing the operating parameters of the combustor. Previous testing in this combustor had fewer data acquisition channels, and did not include a full implementation of a CCADS centerbody. This testing included both the guard and sense CCADS electrodes installed on the nozzle centerbody, and an array of 14 wall mounted spark plugs to monitor the flame ionization downstream along the walls of the combustor. This paper reports the results of this testing, focusing on the relationship between the flame ionization, ultraviolet flame emission, and pressure oscillations. Tests were run over a matrix of equivalence ratios from 0.6 to 0.8, with inlet reference velocities of 20 and 25 m/s. The acoustics of the fuel system for the combustor were tuned using an active-passive technique with an adjustable quarter-wave resonator. Data processing included computing the logarithm of the real-time current signal from the guard electrode, to compensate for the exponential decay of the potential field from the electrode. The data show the standard deviation of the guard current to be the most promising statistic investigated for correlation with the standard deviation of the chamber pressure. This correlation could expand the capabilities of CCADS to allow for dynamic pressure monitoring on commercial gas turbines without a pressure transducer.

scholarly journals Coal-Fueled Gas Turbine Program

1984 ◽  
Author(s):  
F. W. Crouse ◽  
J. S. Halow ◽  
J. S. Wilson
Keyword(s):  
Electric Power ◽  
Gas Turbine ◽  
Cost Sharing ◽  
System Development ◽  
Low Cost ◽  
Department Of Energy ◽  
Basic Data ◽  
Fuel Quality ◽  
Economic Implications ◽  
Economic Studies

The U.S. Department of Energy has initiated a program to stimulate the development of integrated coal-fueled gas turbine systems for generation of low-cost electric power. This paper describes the rationale and elements contained in this program. The incentives for the (DOE) coal-fueled gas turbine program are a perceived need for modular, low-cost electric generating capacity for the mid-to-late 1990’s, which will not increase the consumption of oil and the need for a low-cost option to long lead time conventional electric power generating systems. The coal-fueled gas turbine also offers the potential to repower existing electric generating facilities as well as for industrial cogeneration applications. The primary fuels being considered are coal slurries and coal gasifier fuels under three program elements: (1) basic data studies, (2) systems and economic studies, and (3) component/system development. The basic data element is designed to address needed information on the effects of the coal and coal-derived combustion contaminants on turbine components. Basic combustion phenomena tests are being carried out by the Morgantown Energy Technology Center and by various industrial organizations to accomplish this goal. The systems and economic studies element of the program is an ongoing effort to provide program assessment and direction. Several major equipment manufacturers are parametrically examining various system configurations and fuel quality to determine process and economic implications. The component development element of the program is planned to start in 1984. Ultimately, the success of the program will be measured by the extent of interest and willingness of the various industrial concerns to participate in the development of commercial systems. The industrial interest to date has been good, as shown by the willingness of private companies to provide cost sharing in each element of the program. This cost sharing criterion will continue as the program progresses.

The Development of an Ultra Low Emissions Liquid Fuel Combustor for the OPRA OP16 Gas Turbine

2002 ◽  
Author(s):  
Sikke Klein ◽  
Ivar Austrem ◽  
Jan Mowill
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Diesel Fuel ◽  
Fuel Injection ◽  
Flame Temperature ◽  
Single Digit ◽  
Combustion Dynamics ◽  
Injection Nozzle ◽  
Fuel Nozzle ◽  
Pressure Swirl

During the last few years OPRA has been working intensively on the development of an ultra low emissions combustor for the OP16 gas turbine. The main focus has been on the combustion of liquid fuels (diesel fuel #2), but a natural gas and a dual fuel system has also been developed. The most important aspect of the development has been the patented Controlled Fuel Air Ratio (COFAR) system incorporating the venturi premixer, the air valve and the fuel injection nozzle. The original diesel fuel injection nozzle of the OP16 was a hybrid design, comprising a pressure swirl central injector surrounded by a classic air-blast atomizer. While the emissions with this fuel nozzle were quite good (30 ppm up to 85% load), subsequent natural gas tests demonstrating single digit emissions, while running at a higher average flame temperature indicated that there was scope for improvement of the fuel preparation system. It was clear that atomization, evaporation and mixing of the diesel fuel could be further improved. For better understanding of the combustion of diesel fuel, an atomization and mixing model was developed, to study the quality of the fuel/air mixture leaving the pre-mixer. Based on the results of this study, a fuel nozzle system, using multipoint injection with small pressure swirl nozzles was selected. Three different sets of atomizers have been evaluated and a nozzle arrangement comprising five identical pressure swirl nozzles showed the best results. The emissions on diesel fuel with the new injector proved very satisfactory. The NOx concentration was kept below 25 ppm from 50% load up to 90% load and below 30 ppm at full load. CO and UHC were well below 10 ppm. These low emissions were achieved by running at a low flame temperature (below 1820K). Furthermore, no combustion dynamics or flame instability was observed.

A Study on Design and Test for Combustor and Fuel Nozzles of a Small Aircraft Gas Turbine

1997 ◽  
Author(s):  
C. D. Kong ◽  
S. K. Kim
Keyword(s):  
Gas Turbine ◽  
Optimal Combination ◽  
Flame Stability ◽  
Design Requirement ◽  
Flammability Limit ◽  
Fuel Nozzle ◽  
Design Requirements ◽  
Firing Tests ◽  
Hot Test ◽  
Small Aircraft

A combustor and a fuel nozzle for a small aircraft gas turbine were designed and appropriateness for design requirements were evaluated and confirmed through the cold and hot test. For the purpose of studying the flame stability of a pilot atomizer under ignition, firing tests were carried out at the various fuel supply pressures. As the results of the experiment and design revision, the optimal combination of the fuel nozzle which is suitable to the design requirement was obtained without the fuel splash phenomena and unstable flame. The combustor was designed and evaluated with detailed investigations and experiments for design requirements. As the results of the hot test, it was confirmed that the combustor in this study had proper profile and pattern factors, flammability limit, total pressure loss and combustor efficiency within design requirements.

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