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Powerplant > Reciprocating Engine Theory > Flashcards

Reciprocating Engine Theory Flashcards

1
Q

Number of pounds of fuel burned per hour for each horsepower produced at the propeller shaft.

A

Brake specific fuel consumption.

BSFC

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2
Q

______ allow the engine to turn fast enough to develop the required power while keeping the prop speed slower.

A

Reduction gears.

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3
Q

Five events, in order, in the Otto cycle:

A 
Intake stroke,
Compression stroke,
Ignition,
Power stroke,
Exhaust stroke.
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4
Q

_______ is the time that both the intake and exhaust valves are off their seat.

A

Valve overlap

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5
Q

Valve overlap occurs at the end of the ______ and the beginning of the ______.

A

Exhaust stroke,

Intake stroke.

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6
Q

T\F

It is not possible to directly measure the amount of indicated HP an engine is producing.

A

True

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7
Q

T/F

It is not possible to directly measure the amount of brake HP an engine is producing.

A

False

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8
Q

T\F
It is possible to directly measure the amount of indicated mean effective pressure in the cylinder of a reciprocating engine.

A

True

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9
Q

T/F

It is possible for a naturally aspirated engine to have a volumetric efficiency of 100%.

A

False

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10
Q

If both the intake and exhaust valve clearances are too great, the efficiency will _______.

A

Decrease.

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11
Q

T/F

The bore of a square engine is the same as the the stroke.

A

True

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12
Q

The ratio of the volume of a cylinder above the piston at the bottom of its stroke to the volume with the cylinder at the top of its stroke is called the _____.

A

Compression ratio

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13
Q

T/F

Increasing the compression ratio of an engine decreases its thermal efficiency.

A

False

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14
Q

The practical limit to the compression ratio an engine can tolerate is determined by the ______ of the fuel.

A

Detonation characteristics.

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15
Q

Two variables over which a pilot has control to determine the HP produced by an aircraft are:

A

RPM,

Brake mean effective pressure.

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16
Q

A measure of the number of pounds of fuel burned per hour to produce each brake horsepower is called the _____.

A

Brake specific fuel consumption.

BSFC

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17
Q

Useful work is done in a heat engine when the chemical energy is released into the air and causes it to ______.

A

Expand.

18
Q

The energy release cycle used by a reciprocating engine is the _______.

A

Constant volume cycle.

19
Q

The energy release cycle used by a turbine engine is the ______.

A

Constant pressure cycle.

20
Q

Define Otto cycle.

A

The constant volume cycle of energy transformation used by reciprocating engines.

21
Q

Valve overlap is important for these 3 reasons

A

Exhaust gas scavenging. Volumetric efficiency.

Proper cooling.

22
Q

Define the acronym “PLANK”.

A 
P= IMEP in PSI. 
L= Length of stroke in feet. 
A= Area of piston head. 
N= Number of power strokes.     (RPM / 2). 
K= Number of cylinders.
23
Q

How many watts in a horsepower?

A

746

24
Q

Standard temp at sea level.

A

59 degrees F

15 degrees C

25
Q

Standard pressure at sea level.

A
  1. 92” Hg.

14. 7 psi.

26
Q

7 factors that affect engine power:

A 
Mechanical efficiency. 
Thermal efficiency. 
Volumetric efficiency. 
Air density. (Temp/Altitude)
Piston displacement. 
Compression ratio. 
Ignition timing.
27
Q

Define natural aspiration in an engine

A

Vacuum is created in the cylinder of a reciprocating engine by the downward movement of the piston, and the opening of the intake valve causes air to be forced in due to atmospheric pressure.

28
Q

For a piston to complete its 4 strokes in a reciprocating engine, the crankshaft must be turned ______ degrees during which ______ events will occur.

A

720.

5.

29
Q

Ignition of the fuel air mixture inside the cylinders of a reciprocating engine before the normal spark occurs is called?

A

Preignition.

30
Q

Uncontrolled explosion inside the cylinder of a reciprocating engine often caused by lower octane/improper fuel.

A

Detonation

31
Q

Define four stroke cycle.

A

Constant volume cycle of energy transformation that has separate strokes for intake, compression, power and exhaust.

32
Q

Define two stroke cycle.

A

A constant volume cycle of energy transformation that completes its operating cycle in two strokes of the piston. One up and one down.

33
Q

Used to increase the pressure of the air being taken into the cylinders of a reciprocating engine.

A

Supercharger

34
Q

Work =

A

Force x distance

35
Q

Theoretical HP developed by a reciprocating engine’s cylinders.

A

Indicated horsepower

IHP

36
Q

Actual horsepower delivered to the propeller shaft of a reciprocating engine.

A

Brake horsepower

BHP

37
Q

Average pressure existing inside the cylinder of a reciprocating engine during its power stroke.

A

Indicated mean effective pressure.

IMEP

38
Q

Theoretical average pressure inside the cylinder of a reciprocating engine during its power stroke.

A

Brake mean effective pressure.

BMEP

39
Q

Absolute pressure, measured in inches of mercury, of the air inside the induction system of a reciprocating engine.

A

Manifold absolute pressure.

MAP

40
Q

An engine whose bore dimensions are the same as its stroke dimensions.

A

Square engine.

Powerplant (19 decks)

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