Principles Of Piston Engine

Question 1

What Is The Otto Cycle

Answer 1

4 Stroke Constant Volume Engine Cycle

Question 2

4 Stages in Otto Cycle

Answer 2

Induction,Compression,Power,Exhaust

Question 3

8 Throws

Answer 3

Crank Throw is the distance between crankshaft and crank pin

Question 4

Firing order of 4 cylinder engine

Answer 4

1,3,4,2

Reduces stress on crankshaft

Question 5

Advantage of a smaller stroke

Answer 5

Saves weight as less mass

Question 6

How many degree does the crankshaft turn for the cycle

Answer 6

720 degrees

Question 7

One Stroke TDC to BDC

Answer 7

180 degrees

Question 8

Crankshaft

Answer 8

Converts piston linear motion to rotary motion

Question 9

Camshaft

Answer 9

Rotates half the speed of crankshaft

Operates valves via push rods

Question 10

Crankcase

Answer 10

Main structural element of engine
Light/strong alloy magnesium
Mounting points

Question 11

Crank Assembly

Answer 11

Compromises crankshaft, piston, connecting rods

Question 12

Induction 1st stage

Answer 12

Inlet Valve Opens TDC
Volume increase/pressure/temp reduce
BDC valve closes
180 degree rotation from TDC to BDC

Question 13

Compression 2nd stage

Answer 13

Inlet Valve/Exhaust valve closed
BDC to TDC
180 degrees
Pressure/temp increases
Volume decreases

Question 14

Power 3rd stage

Answer 14

TDC to BDC
Volume increases/pressure and temp reduce
180 degree rotation

Question 15

Exhaust

Answer 15

Exhaust valve inlet opens (smaller)
Pressure/temp increase as piston returns to TDC

Question 16

Inlet Valve Lead/Lag

Answer 16

Inlet valve opened on return to TDC after exhaust stroke

Inlet valve remains open beyond BDC after induction/prior to combustion

Question 17

Exhaust Valve Lead/Lag

Answer 17

Exhaust opened at end of power stroke

Remains open after TDC

Question 18

Overlap

Answer 18

Period when inlet/exhaust open at the end of exhaust phase

“Scavenging” help draw mixture

Question 19

Ignition Timing

Answer 19

Time before TDC on compression

+ increases peak pressure/power

-Retarded on low rpm to prevent damage/ineffectiveness

Question 20

Piston engine compression ratio

Answer 20

The cylinder volume with the piston at bottom dead centre to the cylinder volume at top dead centre

Question 21

Compression Ratio

Answer 21

Largest volume to smallest volumes

Total volume to clearance volume

Volume at BDC to volume at TDC

Question 22

Clearance volume

Answer 22

Volume in cylinder at TDC

Question 23

Total Volume

Answer 23

Volume in cylinder at BDC

Question 24

Mechanical efficiency of a piston engine

Answer 24

Around 80%

Ratio of actual power produced at propeller shaft to theoretical power

Question 25

Piston engine thermal efficiency

Answer 25

33%

Ratio of work done by engine to the mechanical equivalent of heat energy released

Question 26

Detonation during flight corrective actions

Answer 26

Reduce manifold pressure (bring throttle back)
Fully enrich the mixture

Question 27

Purpose of camshaft

Answer 27

Opens the valves at half crankshaft speed

Question 28

What do valve springs do

Answer 28

Closes the valves

Question 29

The Bore

Answer 29

Area of piston and rings

Question 30

Stroke

Answer 30

From TDC to BDC

Question 31

Compression ratio

Answer 31

Is the ratio of the largest volume (total volume) to the smallest volume (clearance volume)

Question 32

Thermal Efficiency of a piston engine

Answer 32

30%

Question 33

Mechanical efficiency of a piston engine

Answer 33

95%