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ENGINE GAS TURBINE 1ALD 20203

UNIKL MIATEngine Turbine

BY MUHAMAD SYAZWAN MAT GHANI

2OVERVIEW• OPERATION & CHARACTERISTICS OF DIFFERENT TURBINE

BLADE TYPES• BLADE TO DISK ATTACHMENT• NOZZLE GUIDE VANES• CAUSES & EFFECTS OF TURBINE BLADE STRESS & CREEP

3TURBINE SECTION• TO EXTRACT ENERGY AFTER FUEL & AIR ARE BURNED• TRANSFORM

• TURBINE ABSORBS APPROXIMATELY 60% - 80% OF TOTAL PRESSURE ENERGY FROM HOT GASES

• CONSISTS OF 4 BASIC ELEMENTSCASESTATORSHROUDROTOR

A PORTION OF KINETIC ENERGY

(HOT GASES)

MECHANICAL ENERGYINTO

ACCESSORIES

COMPRESSORRUN

4TURBINE ELEMENT

5TURBINE CASE• TO ENCLOSE TURBINE ROTOS & STATOR• HAS FLANGES ON BOTH SIDE TO PROVIDE A MEANS OF

ATTACHING THE TURBINE

6TURBINE ROTOR• CONSISTS OF:

• TURBINE DISK IS THE ANCHORING COMPONENT FOR TURBINE BLADES (EITHER BOLTED OR WELDED TO MAIN SHAFT)

• CENTRIFUGAL FORCE ACTING ON TURBINE BLADE WILL MAKE IT GROW OR CREEPING

• FIR TREE SLOTS IS MOST COMMONLY USE FOR ATTACHING TURBINE BLADES

TURBINE ROTOR / WHEEL TURBINE SHAFT

• ROTOR IS DYNAMICALLY BALANCED & TURBINE BLADES ARE MOMENT WEIGHED

• SHAFT ROTATES WITH BEARING THAT ARE LUBRICATED BY OIL

7TURBINE ROTOR

8TURBINE BLADES• AIRFOIL SHAPED DESIGNED TO EXTRACT MAXIMUM

AMOUNT OF ENERGY FROM FLOW OF HOT GASES• MADE OF STEEL FORGED or NICKEL ALLOY• FIT LOOSELY FOR EXPAND TO FIT TIGHTLY AT NORMAL

OPERATING TEMPERATURE• COMMONLY USE • BLADE CAN BE OPEN or SHROUDED AT TIP• BLADES ARE CLASSIFIED:

FIR TREE SLOT ATTACHMENT

IMPULSE BLADE

REACTION TURBINE BLADE

IMPULSE-REACTION TURBINE BLADE

9TURBINE BLADES

LOOSE FIT FIR TREE WITH OPEN END / TIP

10TURBINE BLADES

LOOSE FIT FIR TREE WITH SHROUDED END / TIP

11TURBINE BLADES – IMPULSE BLADES• IMPULSE BLADE

BLADES ONLY CHANGE THE DIRECTION OF AIRFLOW COMING FROM TURBINE NOZZLE WITH NO CHANGE OF GAS PRESSURE OR VELOCITY

TURBINE WHEEL:

IMPULSE FORCE ON TURBINE BLADES PUSHES TURBINE WHEEL TO ROTATE

ABSORBS THE FORCE REQUIRED TO CHANGE THE DIRECTION OF

AIRFLOW

ROTARY MOTION

CONVERT TO

12TURBINE BLADES – IMPULSE BLADES

13TURBINE BLADES – IMPULSE BLADES

14TURBINE BLADES – REACTION BLADES• REACTION BLADES

PRODUCE TURNING FORCE BASED ON AERODYNAMIC ACTION

THE TURBINE BLADES FORM A SERIES OF CONVERGENT DUCT

TURBINE BLADES ROTATE DUE TO REACTION OF AIRFLOW ACTING ON ITS AIRFOIL SHAPE

GAS VELOCITY

PRESSURE

RESULTS IN CREATING A COMPONENT OF LIFT THAT ROTATES TURBINE WHEEL

15TURBINE BLADES – REACTION BLADES

1. Turbine nozzle in a reaction turbine direct exhaust gas flow to strike turbine blades at positive angle of attack

2. Convergent shape between the turbine blades increases its gas velocity & decreases its pressure

16IMPULSE & REACTION TURBINE

17TURBINE BLADES - IMPULSE-REACTION• IMPULSE-REACTION BLADES

MOST MODERN AIRCRAFT USES THIS TYPE OF TURBINE BLADE

ADVANTAGE : WORKLOAD ALONG THE BLADE IS EVENLY DISTRIBUTED

BLADE ROOT BLADE TIPTHIS DESIGN CREATES UNIFORM VELOCITY & PRESSURE

DROP ACROSS THE ENTIRE BLADE LENGTH

IMPULSE SECTION

REACTION SECTION

18TURBINE BLADES - IMPULSE-REACTION

IMPULSE-REACTION TURBINE BLADES

19STAGGER ANGLE• TURBINE BLADE HAS STAGGER ANGLE (GREATER AT TIP

COMPARE TO ROOT)• REASON FOR TWIST

• RESULTS CERTAIN CHANGES IN VELOCITY, PRESSURE & TEMPERATURE OCCUR THROUGH TURBINE (FIG. PG.20)

• AS AIRFLOW LEAVES TURBINE BLADE, THE RESPECTIVE VELOCITY & PRESSURE ARE EQUAL BETWEEN BLADE TIP & ROOT

MAKE GAS FLOW FROM COMBUSTION SYSTEM DO EQUAL WORK AT ALL POSITIONS ALONG

THE LENGTH OF BLADE

TO ENSURE THE FLOW ENTERS EXHAUST SYSTEM WITH A UNIFORM AXIAL VELOCITY

20STAGGER ANGLE

A TYPICAL TURBINE BLADE SHOWING TWISTED CONTOUR

21STAGGER ANGLE

GAS FLOW PATTERN THROUGH NOZZLE & BLADE

22BLADE TO DISC ATTACHMENT• THE METHOD OF ATTACHING TURBINE BLADES TO TURBINE

DISC IS OF CONSIDERABLE IMPORTANCE, SINCE STRESS IN THE DISC AROUND THE FIXING OR IN BLADE ROOT HAS AN IMPORTANT BEARING ON THE LIMITING RIM SPEED

• THE BLADES ON EARLY WHITTLE ENGINE WERE ATTACHED BY THE DE LAVAL BULB ROOT FIXING

• THE BLADE IS FREE IN SERRATIONS WHEN TURBINE IS STATIONARY & STIFFENED IN ROOT BY CENTRIFUGAL LOAD

BUT THIS DESIGN WAS SOON SUPERSEEDED BY

THE “FIR TREE” – COMMONLY USED NOW

THEY ARE THEN LOCKED IN PLACE WITH RIVETS OR

METAL TABS.

INVOLVES VERY ACCURATE MACHINING TO ENSURE THAT THE LOADING IS SHARED BY

ALL THE SERRATIONS

23BLADE TO DISC ATTACHMENT

VARIOUS METHODS OF ATTACHING BLADES TO TURBINE DISCS

24TURBINE STATOR/NOZZLE GUIDE VANES• REFERRED TO TURBINE NOZZLE / TURBINE GUIDE

VANES / NOZZLE DIAPHRAGM• LOCATED DIRECTLY AFT OF COMBUSTION SECTION &

FORWARD OF TURBINE WHEEL

• PURPOSE

• FORMS A NUMBER OF CONVERGING NOZZLE THAT CONVERT SOME OF EXHAUST GASES PRESSURE TO VELOCITY ENERGY

EXPOSED TO HIGH TEMPERATURE IN A GAS TURBINE ENGINE

COLLECT HIGH ENERGY AIRFLOW FROM COMBUSTORS & DIRECT THE FLOW TO STRIKE THE TURBINE ROTOR AT APPROPRIATE ANGLE

25TURBINE STATOR/NOZZLE GUIDE VANES

26SHROUD• TURBINE NOZZLE ASSEMBLY CONSISTS OF AN INNER &

OUTER SHROUD THAT RETAINS & SURROUND THE NOZZLE VANE

• THE NOZZLE VANES MUST BE CONSTRUCTED LOOSELY TO ALLOW FOR THERMAL EXPANSION

• OUTER SHROUD IS CUT INTO SEGMENTS TO ALLOW FOR EXPANSION

• WITHOUT ALLOWING FOR THERMAL EXPANSION, THE HIGH ENGINE TEMPERATURE WILL CAUSE SEVERE DISTORTION OR WARPING

27TURBINE NOZZLE / TURBINE STATOR

28TURBINE NOZZLE / TURBINE STATOR

29CAUSES & EFFECTS OF STRESS & CREEP• TURBINE SECTION

AREA THAT SUBJECT TO GREAT DEAL OF HEAT & STRESSCRACKING IS MOST COMMON TYPE OF DAMAGE

FOLLOWED BY EROSIONTO CARRIED OUT THE INSPECTION OF THE COMPLETE

TURBINE SECTION; IT IS BEST TO INSPECT TURBINE NOZZLE VANE, TURBINE DISK & TURBINE BLADE SEPARATELY

30CAUSES & EFFECTS OF STRESS & CREEP

HOTTEST GASES PASS THROUGH THE FIRST TURBINE NOZZLE VANE

NORMALLY SMALL CRACK ARE FREQUENTLY FOUND (CHECK LIMITATION)

CERTAIN TURBINE NOZZLE VANE ARE CRACKING BY HIGH SPEED GASES CAUSING BOWING & WARPING

THIS BOWED & WARPAGE IS MEASURED ON THE TRAILING EDGE BY USING FLAT PLATE FIXTURE & THICKNESS GAUGE (CHECK LIMITATION)

TURBINE NOZZLE VANE

31CAUSES & EFFECTS OF STRESS & CREEP

INSPECTED BY USING STRONG INSPECTION LIGHT & MAGNIFYING GLASS

ANY CRACK ON TURBINE DISK CAUSES REJECTION & REPLACEMENT

SLIGHT PITTING EXIST CAN BE BLENDED BY STONING & POLISHING

TURBINE DISK

32CAUSES & EFFECTS OF STRESS & CREEP

• POTENTIAL TO CATASTROPHIC ENGINE FAILURE• CRACKING ARE NOT PERMITTED ON TURBINE BLADE• STRESS RUPTURE CRACKS TO BE CARRIED OUT ON

LEADING & TRAILING EDGE INCLUDE EXCESSIVE TEMPERATURE OR CENTRIFUGAL LOADING

• TURBINE BLADE ARE PRONE TO BLADE CREEP (HIGH TEMPERATURE) & CENTRIFUGAL LOADING DURING EACH CYCLE (SLIGHTLY LONGER)

• BLADE CREEP CAN BE DIVIDEDINTO 3 STAGES :

TURBINE BLADE

PRIMARY

SECONDARY

TERTIARY

33CAUSES & EFFECTS OF STRESS & CREEPPRIMARY CREEP

OCCURS DURING FIRST RUN WHEN NEW BLADES EXPERIENCE OPERATIONAL STRESS FOR THE FIRST TIME

SECONDARY CREEP OCCURS SLOWLY DURING MANY HOURS OF OPERATION

TERTIARY CREEP OCCURS AT AN ACCELERATED RATE AFTER A PERIOD OF

SECONDARY CREEP DUE TO ATTRIBUTION OF HOT START, OVER TEMPERATURE, OPERATION AT HIGH POWER SETTING CONTINUOUSLY & BLADE EROSION

34CAUSES & EFFECTS OF STRESS & CREEP• TURBINE BLADE & VANE ALSO MUST BE CHECKED FOR

UNTWIST WHICH RESULTING DECREASE BLADE EFFICIENCY & DETERIORATION

• OTHER INSPECTION FOR TURBINE BLADE ARE CURLING OF BLADE TIP, CRACKING & BREAKING BLADE TIP

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THANK YOU FOR YOUR ATTENTION

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