This presentation tells all about basic principle behind Gas Turbine, their working, operation and construction. How they came into existence and where are they used.
2. Introduction
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Comprehend the thermodynamic
processes occurring in a gas turbine
Comprehend the basic components of gas
turbine engines and their basic operation
Comprehend the support systems
associated with gas turbine engines
3. Background
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Aircraft turbojet/turbofan engines are precursors
to gas turbines
Installed for propulsion in:
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FFG’s
DD’s
DDG’s
CG’s
M-1 tanks
Also used for electrical generation & auxiliary
applications
4. Advantages of GTE’s
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W
eight reduction of 70%
Simplicity
Reduced manning requirements
Quicker response time
Faster Acceleration/
deceleration
Modular replacement
Less vibrations
More economical
5. Disadvantages of GTE’s
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Many parts under high stress
High pitched noise
Needs large quantities of air
Large quantities of hot exhaust (target)
Cannot be repaired in place
6. Brayton Cycle
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Unlike diesels, operate on STEADY-FLOW cycle
Open cycle, unheated engine
1-2: Compression
2-3: Combustion
3-4: Expansion through
Turbine and Exhaust
Nozzle
(4-1: Atmospheric
Pressure)
13. Compressor
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Radial/centrifugal flow
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Adv: simple design, good
for low compression
ratios (5:1)
Disadvantage: Difficult to
stage, less efficient
Axial flow
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Good for high
compression ratios (20:1)
- Most commonly used
14. Compressor
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Controlling Load on Compressor
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To ensure maximum efficiency and allow for
flexibility, compressor can be split into HP &
LP sections
Vane control: inlet vanes/nozzle angles can be
varied to control air flow
Compressor Stall
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Interruption of air flow due to turbulence
15. Use of Compressed Air
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Primary Air (30%)
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Secondary Air (65%)
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Passes directly to combustor for combustion
process
Passes through holes in perforated inner shell
& mixes with combustion gases
Film Cooling Air (5%)
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Insulates/cools turbine blades
16. Combustion Chambers
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Where air & fuel are mixed, ignited, and
burned
Spark plugs used to ignite fuel
Types
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Can: for small, centrifugal compressors
Annular: for larger, axial compressors (LM
2500)
Can-annular: for really large turbines
21. Turbines
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Split Shaft
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Gas generator turbine drives compressor
Power turbine separate from gas generator turbine
Power turbine driven by exhaust from gas generator
turbine
Power turbine drives power coupling
22. Single Shaft
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Efficiently operates at constant speeds
Used in GTGS (gas turbine generator systems)
Single shaft
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Power coupling on same shaft as turbine
Same shaft drives rotor of compressor and power
components
*Primarily used for electric power because of
constant speed, regardless of load.
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24. Split Shaft
Best where speeds and loads vary
• Used in LM-2500
• Power shaft is decoupled from compressor
• Allows both to operate at efficient speeds (not
the same)
*More suitable for main propulsion applications
due to the fact that the gas generator turbine and
power turbine operate near their most efficient
speeds throughout a RANGE of load demands.
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26. Accessory Drive Assembly
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Purpose - Provides motive force for driving
the accessories required for operation and
control of engine
Attached Accessory Equipment
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Fuel oil pump
Lube oil pump
Starter (pneumatic, electric, hydraulic)
27. Gas Turbine Systems
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Air System
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Fuel System
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Air intakes are located high up & multiple
filters
Exhaust discharged out stacks
Uses either DFM or JP-5
Lubrication System
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Supply bearings and gears with oil
28. Gas Turbine Systems
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Starting System
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To get compressor initially rotated, HP air
used (can use electrical also)
Once at certain RPM, fuel injected and spark
ignited
Power Transmission System
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Reduction gears used to transfer torque
With split shaft, turbines can run @ different
speeds
Air is drawn into the front of the compressor. Each succeeding stage is smaller increasing velocity (recall Bernoullis equation).
Between each rotating stage is a stationary stage or stator. The stator partially converts the high velocity to pressure and directs the air to the next set of rotating blades.
The rotor imparts velocity to the air (like a fan). Each stage consists of a rotor and stator and results in a pressure increase.
Air exits the compressor and enters the diffuser. Suddenly, the air moves from a narrow passage into a wide area. By bernoulli, the air loses velocity and expands in volume and increases pressure. Now, the air is slow moving and high pressure, usually about 19:1. Fuel is injected here and the mixture is ignited by a spark. The spark causes a rapid increase in the volume of the air an combustion gases (at constant pressure).
The combustion mixture goes rearward to a nozzle which directs the gas onto the turbine blades and accelerates the gases. The gases are now high velocity, high temperature, low pressure and are used to turn the turbine. The kinetic and thermal energy of the gases are transferred the turbine blades. The turbine is multistaged to remove as much of the energy from the gas as possible.
Radial flow or centrifugal compressor- compressor draws in the entering air at the hub of the impeller and accelerates it radially outward by centrifugal force through the impeller. Reasonably efficient for high pressure ratios developed in a single stage.
Axial flow- Rotor has fixed blades which force the air rearward much like an aircraft propeller. The stator directs the air rearward to the next stage. Very much like a turbine used in reverse. Used in multistage arrangements and pressure ratios increase with the number of stages.
Can Type- Individual liners and cases mounted around the engine each with its own fuel nozzle.
Annular type- Liner consists of an undivided circular shroud extending all the way around the outside of the turbine shaft housing. The dome of the liner has small slots and holes to admit primary air. There are also holes in the dome for the fuel nozzles to extend through into the combustion area. The combustion space is formed by the inner and outer liners. The inner liner prevents flame from contacting the turbine shaft housing.
Can-annular type- Designed to deal with split spool compressor. Individual cans are placed inside an annular case. Combines the strength of annular design with the convenience of maintenance of the can. Also keeps high temperatures in the inner can.
Turbines, like compressors, consist of stator and rotor elements. Stators prepare the mass flow for harnessing of power through the turbine rotor. The nozzles take the high pressure, high-energy mixture and give it velocity for driving the rotor. Also deflects the gases to a specific angle in the direction of the turbine wheel rotation.
Rotors consist of a shaft and bladed wheel. Turbine operates at high speed
Single- Aircraft and electric power- constant speed independent of load
Split- allows the compressor to run at different speed that power turbine maximizing the efficiency of operation.
Provides the space for mounting and the motive force for driving the accessories required for the operation and control of the engine
Discuss the following accessory equipment attached at the assembly:
Fuel oil pump
Lube oil pump
Starter (pneumatic, electric, hydraulic)