Engine Exhaust Systems

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Engine Exhaust Systems

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Engine Exhaust Systems

Typical Oral Questions

1. Of what material are most reciprocating engine exhaust components made?

Corrosion-resistant steel.

2. How is the speed of a turbocharger controlled?

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.

3. What type of actuator is used to control the position of the turbocharger waste gate?

A hydraulic actuator that uses engine oil pressure to move the piston.

4. How does a power recovery turbine increase the power of a reciprocating engine?

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

crankshaft.

5. How tight should the clamps be tightened that hold sections of a reciprocating engine exhaust system together?

They should not be so tight that they will be damaged when heat expands the exhaust system components.

6. What would be the effect on engine performance of an internal failure of a muffler?

This will increase the exhaust back pressure and cause a loss of engine power.

7. What effect on turbine engine operation is caused by a change in the area of the exhaust nozzle?

Altering the area of the exhaust nozzle affects the compression ratio, the RPM, the mass airflow through the engine, and the EGT.

8. What are two types of thrust reversers that are used with turbojet engines?

Mechanical blockage (clamshell) and aerodynamic blockage (cascade).

9. How does a noise suppressor reduce the amount of noise produced by a turbojet engine?

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.

10. What is the purpose of the ball joints and bellows in the exhaust system of a

reciprocating engine?

The ball joints and bellows allow the exhaust system components to change their dimensions without causing any leaks.

11. Why do some supersonic aircraft use a convergent-divergent exhaust duct?

A CD exhaust duct controls the gas expansion as it leaves the engine so the gases will produce thrust at supersonic velocities.

12. Why is it important that a lead pencil never be used to mark on an aircraft exhaust system?

The graphite in a lead pencil will infuse into the metal when it gets hot. It makes the metal brittle and likely to crack.

13. What type of damage is normally found in the hot section of a turbine engine?

Cracks caused by heat.