Reciprocating Engine Theory

Question 1

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

Answer 1

Brake specific fuel consumption.

BSFC

Question 2

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

Answer 2

Reduction gears.

Question 3

Five events, in order, in the Otto cycle:

Answer 3

Intake stroke,
Compression stroke,
Ignition,
Power stroke,
Exhaust stroke.

Question 4

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

Answer 4

Valve overlap

Question 5

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

Answer 5

Exhaust stroke,

Intake stroke.

Question 6

T\F

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

Answer 6

True

Question 7

T/F

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

Answer 7

False

Question 8

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

Answer 8

True

Question 9

T/F

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

Answer 9

False

Question 10

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

Answer 10

Decrease.

Question 11

T/F

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

Answer 11

True

Question 12

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 _____.

Answer 12

Compression ratio

Question 13

T/F

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

Answer 13

False

Question 14

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

Answer 14

Detonation characteristics.

Question 15

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

Answer 15

RPM,

Brake mean effective pressure.

Question 16

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

Answer 16

Brake specific fuel consumption.

BSFC

Question 17

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

Answer 17

Expand.

Question 18

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

Answer 18

Constant volume cycle.

Question 19

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

Answer 19

Constant pressure cycle.

Question 20

Define Otto cycle.

Answer 20

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

Question 21

Valve overlap is important for these 3 reasons

Answer 21

Exhaust gas scavenging. Volumetric efficiency.

Proper cooling.

Question 22

Define the acronym “PLANK”.

Answer 22

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.

Question 23

How many watts in a horsepower?

Answer 23

746

Question 24

Standard temp at sea level.

Answer 24

59 degrees F

15 degrees C

Question 25

Standard pressure at sea level.

Answer 25

29. 92” Hg. | 14. 7 psi.

Question 26

7 factors that affect engine power:

Answer 26

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

Question 27

Define natural aspiration in an engine

Answer 27

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.

Question 28

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

Answer 28

720. | 5.

Question 29

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

Answer 29

Preignition.

Question 30

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

Answer 30

Detonation

Question 31

Define four stroke cycle.

Answer 31

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

Question 32

Define two stroke cycle.

Answer 32

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

Question 33

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

Answer 33

Supercharger

Question 34

Work =

Answer 34

Force x distance

Question 35

Theoretical HP developed by a reciprocating engine’s cylinders.

Answer 35

Indicated horsepower | IHP

Question 36

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

Answer 36

Brake horsepower | BHP

Question 37

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

Answer 37

Indicated mean effective pressure. | IMEP

Question 38

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

Answer 38

Brake mean effective pressure. | BMEP

Question 39

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

Answer 39

Manifold absolute pressure. | MAP

Question 40

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

Answer 40

Square engine.