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POWERPLANT ORALS
CHAPTER 3 - TURBINE ENGINES
| Question | Answer |
|---|---|
| EXPLAIN THE MAIN DIFFERENCE AND ADVANTAGE OF TURBOFAN OVER TURBOJET ENGINES. | A TURBOFAN ENGINE USES A FAN TO BYPASS SOME AIR AROUND THE ENGINE CORE AND TO PROVIDE THRUST. THE ADVANTAGE IS THAT THIS PROVIDES ADDITIONAL THRUST WITHOUT INCREASING FUEL FLOW. |
| NAME THE MAJOR COMPONENTS IN A GAS TURBINE ENGINE. | AIR INLET, COMPRESSOR SECTION, COMBUSTION SECTION, TURBINE SECTION, EXHAUST SECTION, GEARBOX AND ACCESSORY SECTION. |
| WHAT DETERMINES THE AMOUNT OF AIRFLOW THROUGH A TURBINE ENGINE? | THE FORWARD SPEED OF THE AIRCRAFT, COMPRESSOR SPEED, AND AIR DENSITY. |
| NAME THE TWO TYPES OF COMPRESSORS COMMONLY USED IN TURBINE ENGINES. | AXIAL AND CENTRIFUGAL FLOW COMPRESSORS. |
| NAME TWO DIFFERENT METHODS FOR ATTACHING TURBINE ENGINE ROTOR BLADES TO THE ROTOR DISKS. | DOVETAIL ROOT, BULB TYPE ROOT, OR FIR TREE ROOT. |
| WHAT IS A SPLIT COMPRESSOR SYSTEM? | ALSO CALLED DUEL OR TWIN SPOOL COMPRESSORS, THESE ARE CONNECTED TO THE TURBINE SECTION WITH TWO ROTOR SHAFTS, ONE INSIDE THE OTHER. |
| WHAT ARE THE DIFFERENT TYPES OF COMBUSTION CHAMBERS USED IN TURBINE ENGINES? | CAN, ANNULAR, CAN-ANNULAR, AND REVERSE FLOW ANNULAR. |
| WHAT PREVENTS THE COMBUSTION CHAMBERS FROM BURNING? | COOLING AIR ALONG THE INSIDE OF THE LINER. |
| WHAT IS THE PURPOSE OF THE INTERCONNECTING TUBES ATTACHED BETWEEN CAN-TYPE COMBUSTION CHAMBERS? | FOR FLAME PROPAGATION DURING START. |
| WHAT FUNCTION DO AXIAL FLOW TURBINE NOZZLES PERFORM? | THEY DIRECT THE MASS AIRFLOW TO DRIVE THE TURBINE ROTOR AT A SPECIFIC ANGLE. |
| HOW IS THERMAL STRESS RELIEVED ON A TURBINE DISC? | BY DIRECTING BLEED AIR ONTO THE FACE OF THE DISK, OR BY GROOVES BEING CUT IN THE DISK. |
| WHAT ARE CARBON SEALS USED FOR IN TURBINE ENGINES? | THEY ARE USED AS OIL SEALS FOR THE ROTOR SHAFT BEARINGS. |
| WHAT IS SHAFT HORSEPOWER? | IT IS AN INDICATION OF THE TORQUE DEVELOPED BY A TURBOPROP OR TURBOSHAFT ENGINE. |
| NAME THE MAIN COMPONENTS OF A TYPICAL APU. | A SMALL POWER TURBINE FOR POWER AND BLEED AIR, AND AN ELECTRICAL GENERATOR. |
| WHEN IS THE GREATEST DEMAND PLACED ON AN APU? | WHEN SUPPLYING BLEED AIR. |
| HOW IS AN APU GENERALLY STARTED? | WITH ITS OWN ELECTRICAL STARTER AND BATTERY POWER. |
| WHERE DOES THE APU GET ITS FUEL SUPPLY? | FROM ONE OF THE AIRCRAFTS MAIN FUEL TANKS. |
| AT WHAT SPEED DOES A GAS TURBINE APU OPERATE AND HOW IS THIS SPEED MAINTAINED? | AT OR NEAR ITS RATED SPEED REGARDLESS OF ELECTRICAL OR PNEUMATIC LOADS IMPOSED. THE APU FUEL CONTROL AUTOMATICALLY ADJUSTS THE FUEL FLOW TO MAINTAIN THE RATED SPEED. |
| WHAT IS USED TO PREVENT A HEAVILY LOADED APU FROM EXCEEDING ITS MAXIMUM EGT? | A LOAD CONTROL VALVE MODULATES THE PNEUMATIC LOAD TO MAINTAIN EGT'S WITHIN LIMITS. |
| HOW IS AN APU SHUT DOWN? | AFTER THE APU IS UNLOADED BY CLOSING THE BLEED AIR VALVE, IT IS RUN FOR A SPECIFIED AMOUNT OF TIME TO ALLOW THE EGT TO COOL AND STABILIZE. THIS COOL DOWN PERIOD IS TYPICALLY THREE MINUTES. |
| WHY IS THE APU SHUTDOWN PROCEDURE USED? | IF A HEAVILY LOADED APU IS ABRUPTLY SHUT DOWN W/O A COOL DOWN PERIOD, DAMAGE COULD OCCUR AS A RESULT OF THERMAL SHOCK. |
| WHAT POWERS THE VARIABLE INLET GUIDE VANES USED ON SOME APU'S TO REGULATE COMPRESSOR INTAKE AIRFLOW? | FUEL PRESSURE. |
| WHAT IS FAN BLADE SHINGLING? | IT IS THE OVERLAPPING OF THE MIDSPAN SHROUDS OF THE FAN BLADE. |
| WHEN A TURBOFAN OR TURBOJET ENGINE IS SHUT DOWN, WHAT SHOULD A MECHANIC LISTEN FOR DURING COASTDOWN? | ANY RUBBING SOUND OR OTHER UNUSUAL NOISES FROM THE ENGINE. |
Created by:
brookburns34924
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