Patent Application
20100293952
The present application relates generally to gas turbine engines and more particularly relates to a swirler for a combustor that absorbs high frequency pressure waves as a resonator.
Current designs of Dry Low NOx (DLN) gas turbines generally operate with a lean fuel air mixture. The lean fuel air mixture includes an amount of fuel premixed with a large amount of excess air that is burned in a combustion chamber. Although such a lean mixture reduces the amount of NOx emissions, low and high frequency combustion instabilities may result. The high frequency combustion instabilities may be referred to as screech. These instabilities may be caused by burning rate fluctuations coupled with fuel-air flow fluctuations and combustor acoustics. This coupling may result in a very high amplitude of low frequency combustion instability and screech inside the combustor. Even a small amplitude of screech inside the combustor may quickly reduce the life of the components of the combustor.
To reduce the amplitude of such screech instabilities, carefully located damping or resonating devices may be used about the combustor. These known resonating devices, however, have not been completely effective in completely absorbing the high frequencies.
There thus is a desire for an improved resonating device, particularly for the combustor of a Dry Low NO turbine. Such a resonating device preferably should absorb high frequency screech while promoting overall turbine efficiency and performance.
The present application thus provides a swirler for a turbine combustor. The swirler may include an outer wall, a passage defined by the outer wall, and an end wall. The end wall may include a number of apertures therethrough.
The present application further provides for a swirler for a turbine combustor. The swirler may include an outer wall, an inner wall, a cavity defined by the outer wall and the inner wall, and an end wall. The outer wail may include a number of outer wall apertures therethrough.
The present application further provides for an outer swirler for a secondary nozzle of a turbine combustor. The swirler may include an outer wall, a nozzle wall, a passage defined by the outer wall and the nozzle wall, and an end wall. The end wall may include a number of apertures therethrough such that the swirler may include a resonance frequency therethrough.
These and other features of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken conjunction with the several drawings and the appended claims.
Referring now to the drawings, in which like numbers refer to like elements throughout the several views
As is shown in
The apertures 120 of the swirler 100 thus may act as a type of a Helmholtz resonator. A Helmholtz resonator provides a closed cavity having a sidewall with openings therethrough. The fluid inertia of the gasses within the pattern of the apertures 120 may be reacted by the volumetric stiffness of the swirl passage 110 so as to produce a resonance in the swirl passage 110 that may be an effective mechanism for absorbing acoustic energy. The number, length, diameter, shape, and position of the apertures 120 may vary with respect to the volume of the swirl passage 110. Specifically, the design criteria includes the site of the apertures 120, the diameter of the apertures 120, the number of apertures 120, the mass flow through the swirl passage 110, and the volume of the swirl passage 110. In this example, the apertures 120 may have a diameter of about 0.15 inches (about 3.8 millimeters), a thickness of about 0.65 inches (about 16.5 millimeters), and a flow therethrough of about 2 lbm/sec (about (0.9 kgm/sec) so as to absorb a screech frequency of about 2400 Hz Other dimensions and frequencies may be used herein.
The apertures 120, 126 thus may be designed to absorb one or more frequencies of interest. Specifically, the swirler 100 may be designed for a broad range of frequencies, such as the screech tone around 2400 Hertz and otherwise. The swirler 100 thus provides swirl to the fuel-air flow while mitigating combustion dynamics. Mitigating the combustion dynamics may improve the operability window of the gas turbine engine 10 as a whole. Moreover, the use of a separate resonating device is not needed. Likewise, no modifications may be required for or about the secondary nozzle wall 85.
It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
