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AMT 225 > Engine induction and cooling > Flashcards

Engine induction and cooling Flashcards

1
Q

What is a mixture ratio?

A

The composition of the fuel/air mixture

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2
Q

What is the perfect mixture for combustion?

A

15:1

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3
Q

What is a stoichiometric mixture?

A

A mix where all the fuel and all the oxygen in the air is completely used in the combustion process

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4
Q

What are the two types of induction systems on recip engines?

A

Naturally aspirated
Supercharged

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5
Q

What is a naturally aspirated engine?

A

An engine that uses atmospheric pressure to force fuel-air charge into the cylinder

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6
Q

What is a function of an air scoop?

A

Used to convert some ram air pressure into a pressure that forces air into the cylinders

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7
Q

What are three common types filters?

A

Metal mesh
Dry papers
Foam filters

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8
Q

Should foam filters be cleaned?

A

No they should be replaced

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9
Q

Is changing the type of filter a major alteration?

A

Yes and requires and STC

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10
Q

How is icing prevented in a float carburetor?

A

By passing induction air through a heat muff around the exhaust system

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11
Q

When is carb heat normally not used?

A

On the ground

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12
Q

What are two downsides to carb heat?

A

Loss of power
Possible detonation

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13
Q

What is the purpose of an alternate air system?

A

To bypass the filter when its clogged and is also non-filtered air

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14
Q

What is the function of an intake manifold?

A

To equalize the fuel-air mixture flow to each cylinder on the engine

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15
Q

What is manifold pressure?

A

The absolute pressure in the induction system which forces the air into the cylinders

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16
Q

The higher the manifold pressure, the greater?

A

Density of air pressure being taken into the cylinders

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17
Q

The amount fuel burnt by an engine is directly proportion to?

A

The amount of air consumed by the eninge

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18
Q

What is forced induction and why is it used?

A

The air is compressed using a compressor to increase airflow into the cylinders. The air pressure is lower at higher altitudes

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19
Q

What is volumetric efficiency?

A

The actual amount of air flowing through an engine compared to theoretical maximum

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20
Q

How does an naturally aspirated engine work?

A

It uses atmospheric pressure to force the mixture into the cylinders

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21
Q

What is MAP?

A

The pressure in the intake manifold

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22
Q

What is critical altitude?

A

Altitude above which a recip engine will no longer produce rated horsepower with its throttle wide open

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23
Q

What are the two types of superchargers?

A

Internal gear-driven superchargers
External exhaust gas-driven turbocharges

24
Q

What are the three components of a supercharger?

A

Impeller
Diffuser
Manifold

25
Q

What is a supercharger and how is it driven?

A

Uses a gear driven centrifugal compressor placed between the carb and the intake pipes.

It is driven by the crankshaft through gears

26
Q

How does a turbo charger work?

A

It uses a small radial inflow turbine in the exhaust system to drive a centrifugal air compressor. Driven by the velocity of the exhaust gases.

27
Q

What are the main components of a turbo?

A

Compressor assembly
Turbine wheel assembly
A full floating shaft bearing assembly

28
Q

What is the function of lubrication oil in a turbo?

A

Lube the bearings
Transfer heat away from the turbocharger

29
Q

How is the speed of a turbocharger controlled?

A

By controlling the amount of exhaust gases allowed to flow through the turbine.

30
Q

How does a turbo divert exhaust gases to or around the turbo to control the boost?

A

By using a waste gate valve parallel with the turbine

31
Q

When the wast gate is wide open what happens with the exhaust?

A

Gasses bypass the turbine and pass overboard providing little or no boost

32
Q

What happens when the waste gate is fully closed?

A

all the gases are forced through the turbine to provide max boost

33
Q

When a turbocharged engine is started what position is the waste gate valve in?

A

wide open

34
Q

What is the upper deck pressure and what is it also referred to as?

A

The pressure in the intake manifold before the throttle valve.

Turbocharger discharge pressure

35
Q

What is overboost?

A

A condition of excessive manifold pressure

36
Q

What are the three common methods to control the amount of boos in a turbo?

A

Waste gate restrictor
Manually controlled waste gate valve
Automatically controlled wast gate

37
Q

How do you prevent over boosting?

A

An upper deck pressure relief valve is used

38
Q

How does Lycoming refer to a waste gate valve?

A

Exhaust bypass valve

39
Q

What are the key control components to turbo control system?

A

Absolute pressure controller
Rate-of-change controller
Pressure ratio controller

40
Q

How is a waste gate held opened and closed?

A

Held open by a spring

Closed by engine oil pressure

41
Q

When can’t manifold pressure increased any further?

A

When it reaches the critical altitude

42
Q

What is the function of the absolute pressure controller?

A

It slows down the compressor, so the upper deck pressure and the manifold pressure is regulated

43
Q

What is the function of the rate of change controller?

A

Prevents inadvertent overboosting

44
Q

What are the key components in a lycoming turbo system?

A

Density controller
Differential pressure controller

45
Q

What is the function of the density controller?

A

Only controls the engine during full throttle operation

46
Q

How do you prevent boostrapping?

A

A differential pressure controller

47
Q

What is bootstraping?

A

A transient increase in engine power will cause the turbocharger to speed up which in turn causes the engine to produce more power.

48
Q

Excessive heat in a recip engine could lead to?

A

Detonation
Loss of power
Excess wear

49
Q

What are the two types of cooling systems?

A

Air
Liquid

50
Q

What are the advantages of air cooled engines?

A

Simpler
Lighter
Less prone to failure
Cheaper to maintain

51
Q

What are the key components on an air cooled engine?

A

Cooling fins
Engine cowling
Baffles

52
Q

How do cooling fins work?

A

By increasing the exposed surface area for efficient cooling

53
Q

What is the main purpose of an engine cowling?

A

Streamlines the airflow around the engine reducing the drag considerably

54
Q

How does a pressure cooling system work?

A

Causes a pressure differential between the upper and lower compartments

55
Q

In what position should cowl flaps be while on the ground any why?

A

Wide open for more cooling

56
Q

Where is the highest temperature on a turbine engine?

A

At the turbine inlet

57
Q

What is active clearance control on a turbine engine?

A

A stream of cold air is blown around the case to shrink the case to minimize tip losses

AMT 225 (8 decks)

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