Propulsion

Question 1

water passes through a series of tubes surrounded by combustion gas used to transfer heat energy and produce steam. It is the most common type of main propulsion boiler.

Answer 1

watertube boiler

Question 2

combustion gases pass inside a series of tubes surrounded by water to produce steam. Used as an auxiliary boiler.

Answer 2

firetube boiler

Question 3

3 types of watertube boilers

Answer 3

A-type, D-type, O-type

Question 4

a turbine that is driven by nozzle jets direct against the blades

Answer 4

impulse turbine

Question 5

turbines that develop torque by reacting to the gas or fluid’s pressure or mass. The pressure of the gas or fluid changes as it passes through the turbine rotor blades

Answer 5

Reaction turbines

Question 6

the current flow of one ampere with a voltage of one volt

Answer 6

One Watt

Question 7

Shaft horsepower is converted to a rotary force (or moment) applied to the propeller. The rotary force necessary to turn the shaft

Answer 7

torque

horsepower multiplied by 5252 divided by speed (rpm)

Question 8

5 TYPES OF PROPULSION UNITS

Answer 8

A. Diesel Engines
B. Steam Engines
C. Diesel Electric
D. Gas Turbines
E. Combined Systems

Question 9

design considerations in propulsion systems

Answer 9

economic and ship purpose/type

Question 10

A rotary engine in which the kinetic energy of a moving fluid or gas (vapor) is converted into mechanical energy by causing a bladed rotor to rotate.

Answer 10

propulstion engine

Question 11

extracts energy from a flow of combustion gas. It has an upstream compressor coupled to a downstream turbine, and a combustion chamber in-between

Answer 11

gas turbine

Question 12

a thermodynamic cycle that describes the workings of a constant pressure heat engine

Answer 12

The Brayton Cycle

Question 13

a pressure-velocity compounded, single axial flow, non-condensing impulse turbine

Answer 13

high-pressure turbine

Question 14

turbine blading that causes a series of pressure drops and velocity drops

Answer 14

pressure-velocity compounding

Question 15

steam flows in one direction, from forward end to after end

Answer 15

single axial flow

Question 16

exhaust condition where exhaust moves into crossover pipe

Answer 16

non-condensing exhausting condition

Question 17

blades are half-moon shaped. steam loses velocity without losing pressure

Answer 17

impulse blading

Question 18

first stage in a HP turbine where a nozzle block pushes steam through to the moving blades. The stage is velocity compounded, as the steam moves through the impulse blades, velocity drops and pressure remains the same

Answer 18

curtis stage

Question 19

remaining stages in a HP turbine where a nozzle diaphragm pushes steam through to the moving blades. The stage is pressure compounded, as the steam moves through the impulse blades, pressure drops and velocity remains the same

Answer 19

rateau stage

Question 20

a pressure compounded, single or dual axial flow, condensing reaction turbine

Answer 20

low-pressure turbine

Question 21

steam enters the center of the turbine and flows in opposite directions

Answer 21

dual axial flow

Question 22

condition where steam exhausts into the main condenser

Answer 22

condensing turbine exhausting condition

Question 23

blading that causes steam to move through similar to a jet engine. the blades take in air, compress it, heat it, and expel it with a lower pressure

Answer 23

reaction blading

Question 24

a velocity compounded, single axial flow, condensing impulse turbine, consisting of one or two curtis stages, located on the forward and/or after end of the LP turbine

Answer 24

astern turbine

Question 25

how does a propeller work? (basic)

Answer 25

A propeller transforms TORQUE into THRUST.

A propeller has rotating lifting surfaces that pull water from ahead and push it aft, creating a moving water column or slipstream. The slipstream moves thru the propeller like a screw, at a rate that is proportional to the PITCH and rpm of the propeller. But unlike a screw, while acting upon a less dense liquid verses a solid, there is SLIP, which reduces the expected distance that the propeller will travel.

Question 26

Propeller Pitch

Answer 26

the distance a propeller travels in a complete spin of 360° degrees

Question 27

Propeller Slip

Answer 27

The difference between the theoretical distance the propeller should travel in one revolution and the actual distance the vessel travels. Expressed as a percentage.

(E-A) / E x 100.
Where,
E = Expected distance per propeller revolution = pitch.
A = Actual distance covered (measured by speed log)

Question 28

Helical gears

Answer 28

All marine propulsion gears. single row of gears cut at an angle. High power applications will certainly be Double Helical (2 rows of gears, each cut with the opposite “hand”), in order to minimize axial forces.

Question 29

Involute gear tooth profile

Answer 29

The tooth profile of all marine propulsion gears, creates a smooth rolling motion of the gear contact during tooth engagement. An Involute profile enables the transfer of force from the driving gear tooth to the driven gear tooth is be centered along the “Line of Action”

Question 30

Gear Ratio

Answer 30

the number of times greater that the driving gear is rotating faster than the driven gear. the driving gear (pinion) is always smaller than the driven gear. Gear Ratio is driven DIVIDED BY driving, and so will always be a number greater than 1.

the rotational speed (rpms) of the engine relative to the rotational speed (rpms) of the propeller shaft. Therefore, a 3:1 gear ratio means an engine running at 750 rpms will turn the propeller shaft at 250 rpms.

Input: Greater rpms, Smaller gear diameter gear, Less gear teeth. Output: Fewer rpms, Larger gear diameter, More gear teeth. (the 2 matching gear have the same pitch, any change of one gear’s diameter will have to have proportionally less teeth, and vice versa.)

Question 31

gear pitch

Answer 31

gears must have the same pitch to operate correctly

Question 32

typical shaft properties

Answer 32

built in sections, solid or hollow

Question 33

fairwater

Answer 33

shaft casing, light construction, for streamlining and to reduce turbulence

Question 34

fluid film hydrodynamic bearings

Answer 34

self-generating pressure bearings

Question 35

fluid film hydrostatic bearings

Answer 35

sleeve bearings (journal bearings). efficient and reliable. wear when rotational speed too low and fluid film low

Question 36

roller bearings

Answer 36

rolling element transmits load from moving parts to stationary

Question 37

line shaft bearings

Answer 37

• radial bearings
• support and position shaft
• sometimes called spring bearings
• self contained with sump in bottom
• lubricated with oil rings that “sling” oil

Question 38

thrust bearings

Answer 38

delivers axial thrust to ships hull

Question 39

stern tube bearings

Answer 39

oil or water lubricated and cooled

Question 40

strut bearings

Answer 40

Strut bearings may be water or oil-lubricated. The construction is similar to that of stern-tube bearings.

Question 41

a propulsion system for ships using a combination of steam turbines and gas turbines to power the shafts. A gearbox and clutches enable either of the engines or both of them together to drive the shaft. It has the advantage of the cruising efficiency and reliability of steam and the rapid acceleration and start-up time of gas.

Answer 41

Combined Steam and Gas (COSAG)

Question 42

suction side of the propeller

Answer 42

leading side

Question 43

pressure side of the propeller

Answer 43

trailing side

Question 44

inner gears revolve inside outer gear

Answer 44

planetary gear

Question 45

useful when the direction of a shaft’s rotation needs to be changed. They are usually mounted on shafts that are 90 degrees from each other

Answer 45

Bevel gears