Exam 4 Flashcards
With respect to the combustion process, how do turbine engines differ from reciprocating (piston) engines?
- In turbine engines combustion takes place at near constant velocity, while in a reciprocating engine combustion takes place at an increasing temperature.
- In turbine engines combustion takes place at near constant pressure, while in a reciprocating engine combustion takes place at a constant volume.
- In turbine engines combustion takes place at near constant temperature, while in a reciprocating engine combustion takes place at an increasing pressure.
- In turbine engines combustion takes place at near constant volume, while in a reciprocating engine combustion takes place at an increasing pressure.
B
Typically, the fuel system in a turbine engine will contain filters just before and just after the main fuel pump. The high pressure filter will contain a special safety feature. What is it?
- A fusable plug that melts if the temperature gets too high.
- A bypass system that will open if the filter becomes blocked.
- A bypass system that will operate when the fuel flow is low.
- A bypass system that operates during engine start to provide higher fuel flow to the nozzles.
B
The practical application of Newton’s third law, as it applies to a turbofan engine, is called:
- power.
- RAM effect.
- thrust.
- momentum.
C
Multiple, separate interconnected chambers within a common air casing, encircling the turbine shaft, describes:
- a can combustion chamber.
- a can-annular combustion chamber.
- an annular combustion chamber.
- axial flow combustion chamber.
B
Injecting water/methanol into the combustion chamber of a turboprop engine:
- increases the temperature of the air, thereby decreasing the density and therefore the weight (mass) of the gas flow through the engine.
- cools the air, thereby increasing the density and therefore the weight (mass) of the gas flow through the engine.
- increases the velocity of the air, thereby increasing the weight (mass) of the gas flow through the engine.
- increases the pressure of the air, thereby decreasing the density and therefore the weight (mass) of the gas flow through the engine.
B
What are the three stages of turbine blade creep?
- First, second and third.
- Status, gradual and final.
- Primary, secondary and tertiary.
- Initial, developed and terminal.
C
What is Boyle’s Law?
- For gas at a constant pressure, the volume of a given mass of gas is directly proportional to its absolute temperature.
- For gas at a constant volume, the pressure of a given mass of gas is directly proportional to its absolute temperature.
- For a gas at a constant temperature, the pressure in a closed vessel will be inversely proportional to its volume.
- Equal volumes of ideal or perfect gases, at the same temperature and pressure, contain the same number of particles, or molecules.
C
Which of the following is most likely to cause a compressor stall?
- A bird ingestion (strike).
- Starting the engine with a significant tailwind.
- Starting the engine at an airfield with a high pressure elevation.
- Landing in gusty crosswind conditions.
A
What is the primary function of the nozzle diaphragm?
- To increase the pressure of the exhaust gases.
- To decrease the velocity of heated gases flowing past this particular point.
- To prevent choking of the heated gases flowing past this particular point, thereby reducing the possibility of turbine and compressor stall.
- To maximise the velocity of the gas exiting the combustion section ,and to direct the gases at the optimum angle onto the turbine blades
D
Which part of a turbine engine is most susceptible to damage as the result of an over-temp condition?
- The compressor inlet guide vanes.
- The first stage turbine nozzle.
- The exhaust duct.
- The diffuser.
B
What is the definition of compressor pressure ratio?
- The ratio of stage one outlet pressure to stage two inlet pressure.
- The ratio of the final stage outlet pressure to first stage inlet pressure.
- The ratio of combustion chamber outlet pressure to the engine inlet pressure.
- The ratio of the inlet pressure to the first stage compressor outlet pressure.
B
How are modern turbine blades cooled in a turbofan engine?
- Oil is splashed over them.
- Bleed air from the compressor is blown over and/or through them.
- Fan air is blown over and through them.
- Secondary combustion air is blown over and through them
B
How is the residual temperature of the exhaust gases utilised?
- Exhaust gases are used for airframe ice protection systems.
- It is not used at all, but rather it is lost to the atmosphere.
- Exhaust gases are used for engine ice protection systems.
- On turboprops the temperature of the exhaust gases can contribute to forward thrust, but on helicopters they serve no useful purpose
B
Which of the following is NOT a symptom of a compressor stall/surge?
- Fluctuating RPM.
- A surging/popping noise.
- Increasing turbine temperature.
- Increasing EPR
D
How do clamshell reversers function?
- By cascade vanes in the nacelle surrounding the bypass duct opening to allow the cold fan air to flow outward and forward.
- By blocker doors external to the exhaust duct moving to blank off the hot exhaust gases redirecting them forward.
- By blocker doors inside the exhaust duct moving to blank off the hot exhaust gases redirecting them forward.
- By blocker doors in the bypass duct moving to blank off the cold fan air redirecting it forward.
C