Catalytically stabilized gas turbine combustor

The present application relates generally to gas turbine engines and more particularly relates to a combustor for a gas turbine that is catalytically stabilized.

At temperatures above about 2800 degrees Fahrenheit (about 1538 degrees Celsius), the oxygen and nitrogen present in the air combine to form nitrogen oxides (NO and NO₂, collectively known as NO_x.) As a result, modem low emission gas turbines generally use a very lean, premixed flame for low NO_x combustion. Operational boundaries include “Lean Blow Out” (“LBO”), which may result in a partial or a complete blowout of the flame in one or more combustors. Another boundary is acoustic pressure oscillations or combustion dynamics. These combustion dynamics may influence the operability or durability of the combustion system as a whole. As a result, it may be necessary to tune individually each gas turbine to remain operational while still satisfying emissions controls. Tuning, however, can influence not only the time required for commissioning, but also may be needed to address ambient or load variations.

Both the LBO and combustion dynamics boundaries can be influenced by providing a stable anchoring flame for the combustor. In older low NO_x combustors, this anchoring flame may be provided by a piloting diffusion flame. This type of pilot, however, may cause NO_x emissions to be higher than desired or permitted. Specifically, the use of a diffusion pilot makes it difficult to reach the desired single digit NO_x emissions in modem gas turbines with high firing temperatures.

Thus, there is a desire for a more stable anchoring flame for low NO_x combustors. Such a stable anchoring flame should reduce blow out tendency, increased hot section life, relax tuning requirements, and enhance the low NO_x operating range.

The present application thus provides a combustor for a gas turbine. The gas turbine combustor may include a central combustion nozzle with a catalyst therein and a number of outer combustion nozzles surrounding the central combustion nozzle.

The present application further provides for operating a gas turbine combustor with a central combustion nozzle and a number of outer combustion nozzles. The method includes the steps of positioning a catalyst within the central combustion nozzle and modulating a fuel-air mixture exiting the central combustion nozzle to a temperature range of about 1000 to about 1500 degrees Fahrenheit (about 538 to about 816 degrees Celsius).

The present application further provides for a gas turbine combustor. The gas turbine combustor may include a catalytic combustion nozzle with a catalyst therein and a number of non-catalytic combustion nozzles positioned about the catalytic combustion nozzle.

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 in conjunction with the several drawings and the appended claims.

Referring now to the drawings, in which like numerals refer to like elements throughout the several views, FIG. 1 shows a portion of a gas turbine engine 100. Generally described, the gas turbine engine 100 includes a compressor 110. The compressor 110 compresses an incoming airflow. The airflow is then discharged to a combustor 120. The combustor 120 includes a number of combustion cans 130. The compressed air and fuel are ignited in the combustion cans 130 and used to drive a turbine section 140. In the turbine section 140, the energy of the hot combustion gases is converted into mechanical work. Some of the work is used to drive the compressor 110 via a shaft 150 with the remainder being available to drive a load such as a generator. By way of example, the gas turbine engine 100 may be a 7FA+e utility gas turbine engine available from General Electric Company of Schenectady, N.Y. Other types of gas turbine engines 100 with a combustor 120 may be used herein.