A specific actuator able to modulate the air feed of a gas a burner at a given frequency and amplitude is presented. The Combustion Department at the Institute for Thermal Turbomachinery and Machine Dynamics at the Graz University of Technology has experience on the study of combustion instabilities in gas turbines using a flow excitor. The stability of an industrial burner is tested at elevated pressure and temperature conditions in the frame of the NEWAC project. For practical matters of operation among which the possibility to induce progressively a perturbation when the flame conditions are all set, the need was expressed to design, construct and validate a flexible actuator able to set an air flow modulation at a given frequency and at a desired amplitude level, with the possibility during operation to let these two factors vary in a given range independently from each other. This device should operate within the 0–1 kHz range and 0%–20% amplitude range at steady-state, during transients, or follow a specific time sequence. It should be robust and sustain elevated pressures. The objective is to bring a perturbation in the flow to which the combustor will respond, or not. For elevated levels of pulsation, it can simulate the presence of vortex-driven combustion instabilities. It can also act as a real-time actuator able to respond in frequency and in phase to actively damp a “natural” combustion instability. Other issues are a better and quicker mixing due to the enhanced turbulence level, and pushing forward the blow out limits at lean conditions with controlled injection dynamics. The basic construction is the one of a siren, with an elevated pressure side where the air is throttled, and a low pressure outlet where the resulting sonic jet is sheared by a rotating wheel. A mechanism allows to let vary the surface of interaction between the wheel and the jet. Two electromotors driven by Labview set both frequency and amplitude levels. This contribution describes the actuator’s principles, design, operation range and the results of the characterization campaign.

References

References
1.
Giuliani
,
F.
, 2002,
“Analysis on the Behaviour of an Aeroengine Air-Blast Injection Device with Forced Entries,”
Ph.D. thesis, ENSAE No. 346, Toulouse, France.
2.
Giuliani
,
F.
,
Leitgeb
,
T.
,
Lang
,
A.
, and
Woisetschläger
,
J.
, 2010,
“Mapping the Density Fluctuations in a Pulsed Air-Methane Flame Using Laser-Vibrometry,”
J. Eng. Gas Turbines Power
,
132
, GTP-031603.z
3.
Yu
,
K.
, 2001,
“Fundamentals and Fluid Dynamics (Experiments),”
in
Active Control of Engine Dynamics
,
RTO AVT -VKI Special Course
, pp.
59
65
. RTO-EN-020.
4.
Hermann
,
J.
, 2001,
“Application of Active Instability Control to Heavy Duty Gas Turbines,”
in
Active Control of Engine Dynamics
,
RTO AVT - VKI Special Course
, pp.
287
302
. RTO-EN-020.
5.
Garay
,
M.
,
Kokanovic
,
S.
,
Guidati
,
G.
,
Torchalla
,
S.
, and
Schuermans
,
B.
, 2006,
“Active Control System for Reduction of NOx and Pulsation Levels in Gas Turbines,”
ASME Paper No. GT2006-90895
.
6.
Evesque
,
S.
,
Park
,
S.
,
Riley
,
A.
,
Annaswamy
,
A.
, and
Dowling
,
A.
, 2004,
“Adaptive Combustion Instability Control with Saturation: Theory and Validation,”
J. Propul. power
,
20
(
6
).
7.
Hirschberg
,
A.
, and
Rienstra
,
S.
, 1994,
“Elements of Aero-Acoustics,”
Applied Aero-Acoustics
,
von Karman Institute for Fluid Dynamics
. LS 1994–04.
8.
Leitgeb
,
T.
,
Giuliani
,
F.
, and
Niederhammer
,
A.
, 2009,
“Computer Aided Dimensioning and Validation of a Versatile Test Facility for Combustion Chambers and Turbines,”
in
ASME Turbo Expo
,
Gas Turbine Technical Congress & Exposition
. GT2009-59592.
9.
Sautter
,
D.
, and
Weinerth
,
H.
, 1993,
Elektronik und Mikroelektronik
,
2nd
ed.,
VDI Verlag
,
Düsseldorf
.
10.
Wüst
,
K.
, 2003,
Mikroprozessortechnik
,
2nd
ed.,
Vieweg Verlag
,
Wiesbaden
.
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