Engine Exhaust Systems
<span class="Apple-style-span" style="line-height: normal;">Engine Exhaust Systems</span><div><span class="Apple-style-span" style="line-height: normal;">**** Hidden Message *****<br></span></div> <div>Engine Exhaust Systems</div><div>Typical Oral Questions</div><div>1. Of what material are most reciprocating engine exhaust components made?</div><div>Corrosion-resistant steel.</div><div>2. How is the speed of a turbocharger controlled?</div><div>By controlling the amount of exhaust gas that flows through the turbine. This is controlled by the position of the waste gate that is in the exhaust pipe.</div><div>3. What type of actuator is used to control the position of the turbocharger waste gate?</div><div>A hydraulic actuator that uses engine oil pressure to move the piston.</div><div>4. How does a power recovery turbine increase the power of a reciprocating engine?</div><div>Exhaust-driven velocity turbines are coupled through a hydraulic drive to the engine crankshaft. Energy that would normally be lost is used to drive the turbines, and the turbines assist in turning the</div><div>crankshaft.</div><div>5. How tight should the clamps be tightened that hold sections of a reciprocating engine exhaust system together?</div><div>They should not be so tight that they will be damaged when heat expands the exhaust system components.</div><div>6. What would be the effect on engine performance of an internal failure of a muffler?</div><div>This will increase the exhaust back pressure and cause a loss of engine power.</div><div>7. What effect on turbine engine operation is caused by a change in the area of the exhaust nozzle?</div><div>Altering the area of the exhaust nozzle affects the compression ratio, the RPM, the mass airflow through the engine, and the EGT.</div><div>8. What are two types of thrust reversers that are used with turbojet engines?</div><div>Mechanical blockage (clamshell) and aerodynamic blockage (cascade).</div><div>9. How does a noise suppressor reduce the amount of noise produced by a turbojet engine?</div><div>It breaks up the low-frequency vibrations in the exhaust stream and converts them into higher frequencies. These high frequencies are dissipated by the air more easily than low frequencies.</div><div>10. What is the purpose of the ball joints and bellows in the exhaust system of a</div><div>reciprocating engine?</div><div>The ball joints and bellows allow the exhaust system components to change their dimensions without causing any leaks.</div><div>11. Why do some supersonic aircraft use a convergent-divergent exhaust duct?</div><div>A CD exhaust duct controls the gas expansion as it leaves the engine so the gases will produce thrust at supersonic velocities.</div><div>12. Why is it important that a lead pencil never be used to mark on an aircraft exhaust system?</div><div>The graphite in a lead pencil will infuse into the metal when it gets hot. It makes the metal brittle and likely to crack.</div><div>13. What type of damage is normally found in the hot section of a turbine engine?</div><div>Cracks caused by heat.</div>
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