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Title: Combustion oscillation monitoring using flame ionization in a turbulent premixed combustor

Abstract

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 runmore » over a matrix of equivalence ratios from 0.6 to 0.8, with an inlet reference velocity of 25 m/s 82 ft/ 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.« less

Authors:
; ; ;
Publication Date:
Research Org.:
National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)
Sponsoring Org.:
USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
917382
Report Number(s):
DOE/NETL-IR-2007-239
Journal ID: ISSN; 0742-4795; eISSN; 1528-8919; TRN: US200816%%372
DOE Contract Number:  
None cited
Resource Type:
Journal Article
Resource Relation:
Journal Name: Transactions of the ASME: Journal of Engineering for Gas Turbines and Power; Journal Volume: 129; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COMBUSTION KINETICS; COMBUSTION CONTROL; COMBUSTORS; FLAMES; GAS TURBINES; IONIZATION; MONITORING; NITROGEN OXIDES; AIR POLLUTION ABATEMENT; ON-LINE MEASUREMENT SYSTEMS

Citation Formats

Chorpening, B T, Thornton, J D, Huckaby, E D, and Benson, K J. Combustion oscillation monitoring using flame ionization in a turbulent premixed combustor. United States: N. p., 2007. Web. doi:10.1115/1.2431390.
Chorpening, B T, Thornton, J D, Huckaby, E D, & Benson, K J. Combustion oscillation monitoring using flame ionization in a turbulent premixed combustor. United States. doi:10.1115/1.2431390.
Chorpening, B T, Thornton, J D, Huckaby, E D, and Benson, K J. Sun . "Combustion oscillation monitoring using flame ionization in a turbulent premixed combustor". United States. doi:10.1115/1.2431390.
@article{osti_917382,
title = {Combustion oscillation monitoring using flame ionization in a turbulent premixed combustor},
author = {Chorpening, B T and Thornton, J D and Huckaby, E D and Benson, K J},
abstractNote = {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 25 m/s 82 ft/ 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.},
doi = {10.1115/1.2431390},
journal = {Transactions of the ASME: Journal of Engineering for Gas Turbines and Power},
number = 2,
volume = 129,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2007},
month = {Sun Apr 01 00:00:00 EDT 2007}
}