Marine Engineering

Question 1

Continuous crankshaft diagram 4 stroke

Answer 1

Question 2

Crankshaft diagram of 4 stroke

Answer 2

Question 3

2 stroke scavenging

Answer 3

2 stroke:
Combustion air must be supplied under pressure

Question 4

2 stroke crankshaft diagram

Answer 4

Question 5

crosshead vs trunk piston

Answer 5

Question 6

dry vs wet cylinder liner

Answer 6

Question 7

Piston: parts

Answer 7

Question 8

crankshaft to connecting rod to piston

Answer 8

Question 9

crankcase

Answer 9

Question 10

cylinder head

Answer 10

Question 11

in-/outlet valves

Answer 11

Question 12

valve controls

Answer 12

Question 13

valve control with pushrod

Answer 13

Question 14

cam profile: overlap

Answer 14

overlap : inlet /exhaust both open at the same time

Question 15

cam profile plotted horizontally

Answer 15

Question 16

valve clearance

Answer 16

too small: thermal overload
too big: mechanical overload

Question 17

different ways to drive camshaft

Answer 17

Question 18

Mechanical injector:
buildup

Answer 18

Injector includes nozzle, which houses the needle

Fuel pressure (150-200 bar) exerted on needle in the high pressure chamber lifts the needle against the spring load

Question 19

Nozzle types

Answer 19

1. Pintle type nozzle (mostly for indirect injection)
2. Multi hole nozzle (mostly direct injection)

a very small amount of fuel leaks along the pressure pin (2) to lubricate it.

Question 20

Different ways of injecting

Answer 20

Question 21

Fuel pumps:
Types

Answer 21

Regulation of pressure, amount, timing :

1. Mechanically
   1.1 Jerk / Reciprocating plunger pump
   1.2 Rotary plunger pump
2. Electrically

Question 22

Jerk type fuel pump

Answer 22

Amount of fuel is determined by radial position of plunger (helix); the stroke is always constant

If vertical groove is in front of spill port then no pressure buildup

Question 23

Injection
Principles, delays, etc

Answer 23

Movement of plunger from lowest position to beginning the delivery stroke is called press delay

Injection timing is determined by position of pump camshaft vs crankshaft. Injection amount is controlled through radial position of the plunger

=> the longer the plunger stroke before the helix opens the spill port, the more fuel is pumped

Although incompressible, it takes the pressure increase (a microsecond) to open the fuel injector: injection delay

The delivery valve in the fuel pump causes the pressure in the fuel line and injector to fall abruptly at the end of each delivery stroke

Question 24

Fuel system
Schematic

Answer 24

Question 25

Lubrication:
Functions

Answer 25

1. Lubrication: separating parts to not come into contact for e.g. metal/metal contact. (vgl: Aquaplaning)
2. Removal of combustion residues
3. Heat dissipation

Question 26

Bearing types

Answer 26

1. Ball bearing
2. Roller bearings, 1+x l/d (higher radial load bearing - but worse wit axial axial load bearing and capacity deteriorating if inner/outer races misaligned)
   including
   
   • spherical roller bearing (stronger axial forces)
   • needle bearings (4x)

Question 27

Good lubrication:
prerequisites

Answer 27

1. sufficient volume of luboil
2. of correct quality and viscosity
3. sufficient shaft rotational speed to form the wedge (aquaplaning)

Question 28

Types of water cooling systems

Answer 28

1. Open / Direct cooling water system
2. Closed cooling water systems
   2.1 Keel or skin cooling
   2.2 Indirect cooling

Question 29

Open / Direct cooling systems:
Disadvantages

Answer 29

1. Cooling water temperature not adjustable
2. Overboard cooling water not clean
3. Sediments in the water
4. Oxygen in cooling water leads to corrosion

Question 30

Closed cooling water systems:
Principles

Answer 30

• Require expansion / header tank
• more expensive (extra cooling pump, heat exchanger, etc)
• requires thermostatic valve

Question 31

Ignition delays engine

Answer 31

1. press delay
2. injection delay
3. combustion delay

Question 32

What is a governor

Answer 32

RPM maintainer, based on centrifugal equilibrium

Question 33

Drive train

Answer 33

Question 34

Flexible coupling
Purpose

Answer 34

Absorb small movements, vibrations, and misalignments of the engine relative to the propeller shaft

Question 35

Gearbox
Function

Answer 35

To couple/uncouple the propeller shaft to/from the engine, reverse the direction of rotation of the propeller shaft, and possibly reduce RPM

Question 36

Thrust bearing
Function

Answer 36

Purpose: transfer the propeller thrust to the hull of the ship

Trust bearings of smaller vessels: spherical = tapered bearings

Question 37

Propeller shaft seals:
Purpose and types

Answer 37

Purpose: prevent outboard water from entering the ship along the propeller shaft

Types:
1. Stern tube seal (= lip seal)
2. Shaft seal (=mechanical seal)
3. Stuffing box

Question 38

Sterntube seal

Answer 38

= lip ring seal

Question 39

Shaft seal

Answer 39

= mechanical seal

Question 40

Stuffing box seal

Answer 40

packing Glen; Glencore; … under a lantern 😬