Principle of Turbines including the working proceures

Gas turbines, also known as internal combustion turbines, are continuous flow internal combustion engines. They produce useful work or thrust by driving generators, pumps, propellers, or aircraft engines. Compared to reciprocating engines, gas turbines are smaller and lighter for the same power output, as they deliver rotary shaft power directly without converting piston motion.

1. PRINCIPLES OF TURBINES

2. Lesson Elements Combustion Turbine principle 2

3. Lesson Objectives Describe the combustion system within a turbine Describe the principle of the turbine engine 3

4. Introduction Picture showing the 5 sections of a gas turbine 4 The gas turbine consists of many basic main subassemblies, which are connected in-line using attaching bolts or nuts at the housing or case flanges of each assembly

5. Air Inlet COMPRESSOR AND INLET AIR ASSEMBLY The inlet air on the Centaur T47 gas turbine assembly has a 360 degree annular opening, covered with a heavy mesh screen. The air inlet housing which is mounted on the forward end of the engine supports the compressor rotor shaft forward bearing and seal housing. The compressor is an eleven stage axial-flow type with one variable Inlet guide vane, two variable vane and nine stator assemblies. It also includes the 11 th stage rotor and the compressor case. 5

6. Air Inlet The variable inlet guide vanes restrict air flow during start to help in preventing surge. The vanes begin to open when pressure reaches approximately 32 psig and fully open when pressure reaches approximately 75 psig. Supported at forward and aft ends by tilt pad bearings, the rotor assembly is connected to the accessory drive gear train and to the turbine rotor shaft. 6

7. Accessary Drive Assembly The accessory drive assembly is mounted on the air inlet assembly provides input and output drives of required rotational speed through various gear ratios. Mounting pads are incorporated on the accessory housing forward face for the hydraulic oil and lube oil pump, seal oil pump, servo oil pump and the starter adapter housing. The gear train is driven by the starters through the starter clutch during start and acceleration, and driven by the compressor rotor through the pinion gear during operation 7

8. COMBUSTOR AND GAS PRODUCER TURBINE 8 A split shaft unit showing compressor and turbine blades

9. EXHAUST SECTION 9

10. COMBUSTOR AND GAS PRODUCER TURBINE The combustor and gas producer turbine assembly includes the turbine-bearing support, the combustor assembly and the two stage turbine rotor assembly. The combustion chamber is a straight through flow annular type. The gas fuel manifold is attached around the circumference of the combustor housing, ten fuel injectors are mounted on bosses around the combustor housing and protrude through and support the combustor liner assembly in the combustion chamber. 10

11. COMBUSTOR AND GAS PRODUCER TURBINE The gas producer turbine rotor assembly consists of the turbine rotor shaft and two turbine rotor disks. The assembly is securely clamped together by a thermo- stretched through bolt. The turbine nozzles are contained in a nozzle case which is cantilevered forward from the aft flange of the combustor housing. The turbine rotor bearing is supported by the bearing support assembly. Most external areas of extremely high temperatures are covered with an insulating stainless steel blanket for protection of personnel and to prevent fire. 11

12. COMBUSTOR AND GAS PRODUCER TURBINE Picture Showing cut away of the turbines internal sections. 12

13. Power Turbine and Exhaust Section The power turbine assembly consists of the single stage power turbine rotor, power turbine bearing housing, turbine exhaust diffuser and exhaust collector . The power turbine bearing housing forward end, which supports the power turbine forward rotor bearing, is attached to the turbine exhaust diffuser. The turbine exhaust diffuser is bolted to the combustor housing aft flange. The annular exhaust collector is insulated with a stainless steel blanket and is bolted to the exhaust diffuser aft flange. 13

14. Power Turbine and Exhaust Section 14

15. Power Turbine and Exhaust Section 15

16. PRINCIPLES OF OPERATION 16 A simplified illustration of a gas turbine engine

17. Air Flow and Combustion Compressed air from the compressor passes into the diffuser; here the air expands which results in a decrease of kinetic energy and a corresponding increase in static pressure. Pressurized diffuser air passes into the combustor section and fulfills two functions A bout ¼ is mixed with fuel and ignited The other ¾ are used to mix with hot combustion gasses, provide an air blanket to protect the combustor. 17

18. Air Flow and Combustion Pressurized diffuser air is also used as a cooling medium to reduce the temperature of the 1 st stage nozzles and the turbine disks. Part of the cool air stream flows between the combustion chamber and the combustor housing. It is important to emphasize that “cool” airstreams temperatures are “cool” only relative to the much greater temperatures generated in the combustion process 18

19. Air Flow and Combustion Holes and louvers in the combustion dome are provided primary for combustion. Holes in the inner and outer liners allow the flow of secondary air, which is directed aft forming an insulating blanket, thus preventing the flame from contacting the inner surface of the liners . Air also ensures complete combustion and dilutes some of the heat of the burning fuel; this also decreases the heat of the gasses entering the turbine 19

20. Air Flow and Combustion The result of the combustion process is increased velocity and expansion of gas across the turbine section. Turbine performance is ultimately determined by the speed of gasses passing through the turbine section. The turbine section is similar to the compressor section it consists of several sets of rotating airfoils located between stationary components called nozzles. The turbine section is almost opposite in function and operation of the compressor section . The compressor section turns mechanical energy (motion) into pressure. The turbine section converts velocity into mechanical energy. 20

21. Engine External Accessories Variable Guide Vane Actuator Provides hydraulic power to the guide vanes Gas Fuel Manifold Delivers gas fuel to the fuel injectors Torch Ignitor and Spark Plug Ignites the fuel injected during the engine start cycle Fuel Injectors Injects gas fuel to support combustion 21

22. Engine External Accessories Bleed Valve and Duct Removes excess air from the combustor during acceleration by venting the air through the exhaust. The bleed valve stops the engine going into surge during start-up. T5 Thermocouples and Harness Measures temperature at the third stage turbine nozzle 22

23. Engine External Components Air Inlet Duct : Directs air into the air inlet assembly Air Inlet Assembly: Incorporates a screened housing which provides a 360-degree path for air to enter the engine and provides mounting for the accessory drive assembly. The air inlet assembly also houses the No1 seal and bearing assembly for the compressor rotor. Variable Guide Vane System: Aids in preventing stall / choke during acceleration, and helps keep maximum compressor performance during start-up. Compressor Case: Encloses the stationary and rotating components of the compressor . 23

24. Engine External Components Compressor Diffuser Case: Provides an exit pathway of air from the compressor to the combustor assembly in such a manner as to convert velocity energy to pressure energy. Compressor Bearing Support Housing: Supports the aft compressor bearing, provides for lube oil in and out of the engine and directs air flow to the combustor assembly. Turbine Bearing Support Case: Supports the forward turbine bearing and directs air flow to the combustor assembly. 24

25. Engine External Components Combustor Housing: Encloses the combustor and gas producer turbine assembly. The combustor housing also provides a mounting for thermocouples. Exhaust Collector: Provides an exit path for hot gases from the exhaust to the atmosphere 25

26. Exhaust Collector 26

27. Engine External Components 27

28. Gas Fuel System The gas fuel system delivers fuel at a required pressure and flow to the fuel injectors in the combustion chamber. The system automatically schedules fuel during acceleration and regulates fuel during operation Gas fuel flows through the strainer to the primary shut off valve and the pilot gas filter, As the engine begins rotating after the initiation of start The pilot gas opens the primary shut off valve allowing gas to the valve test pressure switch, The secondary shut off valve remains closed. The valve test switch closes at a preset pressure, verifying opening of the primary valve. 28

29. ELECTROHYDRAULIC SERVOACTUATOR The servo actuator modifies fuel flow as required to maintain specified engine speed and temperature. Electrical control signals cause the hydraulically-operated piston to retract or extend as required applying more or less fuel. During ignition sequence the actuator is energized by increasing electrical control signal from the ramp generator, beginning at the moment the torch is ignited. 29

30. ELECTROHYDRAULIC SERVOACTUATOR The actuator gradually retracts, opening the throttle valve and enriching the fuel/air mixture until combustion is able to transmit smoothly from the torch, avoiding harsh or violent light offs. When the turbine temperature reaches 350 degrees F, control of the servo actuator transfers to the main fuel actuator control and moves the throttle valve toward the maximum open position 30

31. LOADING COUPLING FLANGES The load coupling flange is located on the end of the load turbine rotor assembly. Some gas turbine engine shafts are connected directly to the pump shaft, compressor, or generator. The connection is made using a device called a coupling. 31

32. LOADING COUPLING FLANGES 32 Turbine Shaft Connections Turbines may be connected directly to the load or they may be connected through a gearbox.