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.

1.
Thornton
,
J.
,
Richards
,
G. A.
, and
Robey
,
E.
, 2000, “
Detecting Flashback in Premix Combustion Systems
,” American Flame Research Committee International Symposium, Newport Beach, CA.
2.
Thornton
,
J. D.
,
Richards
,
G. A.
,
Straub
,
D. L.
,
Liese
,
E. A.
,
,
J. L.
, and
Fasching
,
G. E.
, 2002, “
Flashback Detection Sensor for Lean Premix Fuel Nozzles
,” U.S. Patent No. 6,429,020.
3.
Thornton
,
J. D.
,
Straub
,
D. L.
,
Richards
,
G. A.
,
Nutter
,
R. S.
, and
Robey
,
E.
, 2001, “
An In-Situ Monitoring Technique for Control and Diagnostics of Natural Gas Combustion Systems
,” 2nd Joint Meeting of the U.S. Sections of the Combustion Institute, Oakland, CA, March
25
28
.
4.
Cheng
,
W. K.
,
Summers
,
T.
, and
Collings
,
N.
, 1998, “
The Fast-Response Flame Ionization Detector
,”
Prog. Energy Combust. Sci.
0360-1285,
24
, pp.
89
124
.
5.
Holm
,
T.
, 1999, “
Aspects of the Mechanism of the Flame Ionization Detector
,”
J. Chromatogr., A
0021-9673,
842
, pp.
221
227
.
6.
Calcote
,
H. F.
, 1949, “
Electrical Properties of Flames: Burner Flames in Transverse Electric Fields
,” 3rd Symposium on Combustion, Flame, and Explosion Phenomena, pp.
245
253
.
7.
Fialkov
,
A. B.
, 1997, “
Investigations on Ions in Flames
,”
Prog. Energy Combust. Sci.
0360-1285,
23
, pp.
399
528
.
8.
,
D.
, 1986, “
The Effects of Electric Fields on Combustion Processes
,”
,
, London, p.
340
.
9.
Richards
,
G.
,
Straub
,
D.
, and
Robey
,
E.
, 2003, “
Control of Combustion Dynamics Using Fuel System Impedance
,” ASME Paper No. GT2003-38521.
10.
Straub
,
D.
,
Thornton
,
J.
,
Chorpening
,
B.
, and
Richards
,
G.
, 2002, “
In-Situ Flame Ionization Measurements in Lean Premixed Natural Gas Combustion Systems
,” 2002 Spring Meeting of the Western States Section of the Combustion Institute, March 25–26, La Jolla.
11.
Benson
,
K.
,
Thornton
,
J. D.
,
Straub
,
D. L.
,
Huckaby
,
E. D.
, and
Richards
,
G. A.
, 2003, “
Flame Ionization Sensor Integrated into Gas Turbine Fuel Nozzle
,”
Proc. of TURBOEXPO 2003
, June 16–19, Atlanta,
ASME
,
New York
, ASME Paper No. GT2003-38470.