Stationary turbines

Combustion chamber/Turbine

An industrial gas turbine is an internal combustion engine that uses a continuous combustion process. The combustor is fed high pressure air from the compression system, adds fuel, ignites, and burns the mixture. The hot compressed air generated in the combustion chamber passes into the turbine where it expands. The function of the turbine is to extract power from the hot air flow.

Heat resistant materials are employed, and thermal barrier spray coatings are applied to extend operational life and provide corrosion resistance. Fuel nozzles and mixers are constructed using advanced metal joining processes such as vacuum brazing and electron beam welding techniques.

• Fuel mixers
• Fuel nozzles
• Fuel pipes
• Combustion chamber
• Turbine blades
• Discs
• Drums
• Blades
• Vanes

Blades and vanes

The compressor comprises of various stages of stationary vanes and rotating blades, each stage progressively increasing the air pressure prior to mixing with fuel and igniting. Blades must operate at high rotating speeds and temperatures, while vanes direct the stream propelled by the rotating blades to the next turbine stage with optimum efficiency. Both blades and vanes must be resistant to oxidation, corrosion and wear, and provide longevity in service.

Thermal processing is vital and widely used in the compressor components. HIP rejuvenation of cast vanes and blades removes internal defects thereby improving performance and extending the operational life. Vacuum brazed honeycomb seals reduce back streaming between stages, additionally vacuum brazing allows the assembly of complex vane geometries to provide inter-stage cooling. Wear resistant, thermal barrier and anti-fretting coatings are widely used to protect blades. Aero derivative engines employ single crystal turbine blades that are heat treated to achieve optimum high temperature strength and durability. Typical treated parts include:

• Turbine blades
• High and low pressure blades
• Nozzle segments
• Vane segments
• Nozzle guide vanes
• Stator vanes
• Compressor cases

Seals and bearings

Honeycomb/Abradable seals are primarily used for sealing the tips of rotating parts such as blades and knife edge seals. Maintaining pressure differentials between sections of the turbine is the primary function, thus improving operational efficiencies during operation.

Thermal processing improves strength, efficiency, corrosion and wear resistance of the components. Brazing of corrosion/oxidation resistant honeycomb structures to rings or segments is common. Knife edge seals may require surface treatments such as nitriding or coatings to improve wear and/or corrosion resistance. Typical treated parts include:

• Rotating air seals stationary air seals
• Shrouds
• Bearings

Shafts

The turbine shaft is a critical component as all rotating blade stages are driven from it, with each stage operating at different pressures. Labyrinth seals are used to maintain these differentials.

The shaft must be thermally processed to achieve optimum mechanical properties. Nitriding is often employed to improve wear resistance. Thermal sprayed coatings are widely used to provide corrosion resistance. Typical treated parts include:

• Shafts
• Labyrinth seals