Gas Turbine Combustion Section

General
The combustion system is of the reverse-flow type with 14 combustion chambers arranged around the periphery of the compressor discharge casing. This system also includes fuel nozzles spark plug ignition system, flame detectors, and crossfire tubes. Hot gases, generated from burning fuel in the combustion chambers, are used to drive the turbine. High pressure air from the compressor discharge is directed around the transition pieces and

into the combustion chambers liners. This air enters the combustion zone through metering holes for proper fuel combustion and through slots to cool the combustion liner. Fuel is supplied to each combustion chamber through a nozzle designed to disperse and mix the fuel with the proper amount of combustion air.

Orientation of the combustion chambers around the periphery of the compressor is shown on figure next page. Combustion chambers are numbered counter-clockwise when viewed looking down-stream and starting from the top of the machine. Spark plugs and flame detectors locations are also shown.

 

Combustion Chamber and Crossfire Tubes

 Combustion wrapper
The combustion wrapper forms a plenum in which the compressor discharge air flow is directed to the combustion chambers. Its secondary purpose is to act as a support for the combustion chamber assemblies. In turn, the wrapper is supported by the compressor discharge casing and the turbine shell.

Combustion chambers

Discharge air from the axial flow compressor flows into each combustion flow sleeve from the combustion wrapper (see figure). The air flows up-stream along the outside of the combustion liner toward the liner cap. This air enters the combustion chamber reaction zone through the fuel nozzle swirl tip, through metering holes in both the cap and liner and through combustion holes in the forward half of the liner.

The hot combustion gases from the reaction zone pass through a thermal soaking zone and then into a dilution zone where additional air is mixed with the combustion gases. Metering holes in the dilution zone allow the correct amount of air to enter and cool the gases to the desired temperature. Along the length of the combustion liner and in the liner cap are openings whose function is to provide a film of air for cooling the walls of the liner and cap as shown in figure. Transition pieces direct the hot gases from the liners to the turbine nozzles. All fourteen combustion liners, flow sleeves and transition pieces are identical.

Crossfire tubes

All fourteen combustion chambers are interconnected by means of crossfire tubes. These tubes enable flame from the fired chambers to propagate to the unfired chambers.