Turbine Engines
<span class="Apple-style-span" style="line-height: normal;">Turbine Engines</span><div><span class="Apple-style-span" style="line-height: normal;">**** Hidden Message *****<br></span></div> <div>Turbine Engines</div><div>Typical Oral Questions</div><div>1. What are the two basic sections of a turbine engine</div><div>The hot section and the cold section.</div><div>2. What are the two basic types of compressors that are used in aircraft turbine engines</div><div>Axial-flow and centrifugal.</div><div>3. What is the purpose of the stators in an axial-flow compressor</div><div>The stators convert some velocity energy into pressure energy and change the direction of the air so it is proper for the next stage of rotors.</div><div>4. What are three types of combustors used on aircraft turbine engines</div><div>Can-type, annular-type, and can-annular-type.</div><div>5. How many igniters are there normally in an aircraft turbine engine</div><div>Two.</div><div>6. What is the main purpose of the turbine nozzle in an aircraft turbine engine</div><div>The turbine nozzle directs the hot gases as they leave the combustors so they will turn the turbine wheel with maximum efficiency.</div><div>7. What is meant by a free-turbine turboshaft engine</div><div>A turboshaft engine that has a turbine wheel, or stage of turbine wheels, that is not used to drive the compressor of the gas generator section of the engine. This free turbine drives the propeller in a turboprop engine or the transmission and rotor of a helicopter.</div><div>8. Why do some axial-flow turbine engines have more than one set of turbines and compressors</div><div>A two-spool turbine engine has a low-pressure and a high-pressure compressor, each driven by its own turbine. The two independent systems operate at the speed at which they are most efficient.</div><div>9. What kind of bearings are used to support the rotor shaft of an aircraft turbine engine</div><div>Anti-friction bearings, such as ball bearings or roller bearings.</div><div>10. What is meant by a turbofan engine</div><div>An axial-flow turbine engine in which the first stage of compressor blades are lengthened, so they can force air around the outside of the gas generator portion of the engine.</div><div>11. Where can you find the limits of repair allowed for the compressor blades of an aircraft turbine engine</div><div>In the FAA-approved service manual issued by the manufacturer of the engine.</div><div>12. Why is it important that a turbojet engine be allowed to cool before it is shut down after it has been operated at a high power setting</div><div>If the engine is shut down while it is hot, there is a possibility that the shroud will contract around the turbine wheel and seize the rotor.</div><div>13. What is meant by a hung start in a turbine engine</div><div>A start in which ignition occurs, but the engine does not accelerate to a self-sustaining speed.</div><div>14. What is meant by a hot start in a turbine engine</div><div>A start in which ignition occurs, but the internal temperatures go high enough that they can damage the engine.</div><div>15. What is meant by creep of the turbine blades</div><div>A condition of permanent elongation of the turbine blades. Creep is caused by the high temperatures and the high centrifugal loading imposed on the blades.</div><div>16. How is the compressor of a turbine engine cleaned</div><div>An emulsion-type cleaner is sprayed through the engine while it is being motored by the starter or operated at a low speed. The wash is followed by a clean water rinse.</div><div>More vigorous cleaning is done by injecting a mild abrasive, such as ground-up apricot pits or walnut shells, into the engine while it is operating at low speed.</div><div>17. Where is water injected into a turbine engine for cooling</div><div>purposes</div><div>Into the compressor inlet and into the engine diffuser case.</div><div>18. At what point in a turbine engine is the temperature the highest</div><div>At the inlet to the high-pressure turbine.</div><div>19. What is the function of the interconnect tubes between the cans of a turbine engine that uses can-type combustors</div><div>These tubes allow the flame to travel from the cans that contain the igniters to all of the other cans when the engine is being started.</div><div>20. What are two types of thrust reversers that are used on turbojet engines</div><div>The mechanical blockage-type and the aerodynamic blockage-type.</div><div>21. What is meant by trimming a turbojet engine</div><div>Adjusting the fuel control to get the correct idling and maximum-thrust RPM.</div>
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