gas turbine

FOUR MAJOR COMPONENTS OF A GAS TURBINE ENGINE:
1. Compressor
2. Combustor
3. Turbine
4. Accessory Drive Assembly

COMPRESSOR:
->Function: Provides required air mass at the appropriate pressure to burn the required amount of fuel and to control combustion temperature
->Two types
–Axial Flow
–Centrifugal or Radial Flow


radial flow compressor

axial flow compressor






Axial flow v. Radial flow:
*Centrifugal compressors are simple, inexpensive, lightweight, and have a high pressure rise per stage
*Centrifugal compressors experience large inter-stage losses and require a large frontal area; they are typically less efficient than multistage axial compressor
*Multistage axial compressors can achieve larger compression ratios and are better suited for high-power marine applications

Uses of Compressed Air:
*PRIMARY AIR
–Typically 30% of all compressed air
–Passed directly to combustor, mixed with fuel, and burned
*SECONDARY AIR
–Approximately 70%
–Passes through holes in inner shell and mixes with combustion gases
–Two purposes
•Places an air film between the inner shell and combustion gases to prevent overheating of the inner shell
•Cools combustion gases to an acceptable inlet temperature for the turbine
*FILM AIR
–A small percentage of compressed air may be used to cool turbine blades


COMBUSTION CHAMBER:
*Function: mixes fuel and air and burns this mixture to produce hot combustion gases
*Consists of a casing, perforated inner shell, and fuel nozzles
*Arrangement
–Annular
–Can or Tubular
–Can-annular

TURBINE:
*Develops shaft rotational energy from the kinetic energy of the hot combustion gases entering through the vanes
*Usually of axial flow design
*Drives the compressor and various engine accessories
*The remaining useful energy can be used as jet thrust or shaft mechanical work

Turbine Construction:
*STATOR
–Stationary guide nozzles (vanes) discharge gas at high velocity onto the moving blades
–Attached to turbine casing
*ROTOR
–Consists of a shaft and bladed wheel (disc)
–Attached to the main power-transmitting shaft




Stator Rotor

ACCESSORY DRIVE ASSEMBLY:
*Provides the space for mounting and the motive force for driving the accessories required for the operation and control of the gas turbine engine
*May be used to drive the fuel pump, lube oil pump, etc.


Advantages:
*Weight reduction of 70% when compared to a steam plant of comparable horsepower
*Simplicity
*Reduced manning requirements with more highly automated equipment
*Quicker response time
*Faster acceleration/deceleration
*Modular replacement
*More economical

Disadvantages:
*Many parts under high stress
*High pitched noise
*Needs large quantities of air
*Large heat source