Basic systems & diesel engines Flashcards
Describe Open & Close loop systems
(Mechanical systems)
- Open Loop working fluid is consumed
- Closed Loop working fluid is reused
Name 3 types of tanks & their uses
- Header tank- resevoir to top up system
- Service tank-water free supply of fuel
- Drain tank-collect oil returning from a system
Name 3 tank gauges & their uses
- Contents gauge-indicates how much liquid remains in tank
- Sounding tube-Measure depth
- Gauge glass-visual indication of how much liquid in tank
Manometer
Gives a visual indication of pressure or vacuum
Tachometer
A device that measure speed of a substance or moving body
Rod gearing
Allows a valve to be closed manually from a remote location
Uses for Diesel engines
- Generators
- Main engines & motor boats
- Air compressers
- Fire pumps
Cylinder block
The structure that holds all other engine components
Cylinder head
- Closes the top of the cylinders
- Has the intake & exhaust ports & valves
Cylinder head joint
A water,oil,gas & air tight seal between cylinder block & head
Sump
Resevoir at the bottom of engine to collect oil
Piston
- Moves up & down in the cylinder
- Enables compression
Piston rings
- Provides a seal between piston & cylinder
- Prevent fuel from leaking into sump
- Prevents oil from the sump leaking into cylinder
- Transfer heat from piston to cylinder
Connecting Rod
- Connects piston to crankshaft
- Bearing around gudgeon pin is small end
- Bearing around crankshaft is big end
Gudgeon pin
Connects piston to con rod through small end bearing
Crankshaft
- Changes reciprocating motion from pistons to rotary motion
Flywheel
- Used for smooth running during non power strokes
- Stores energy & returns it to piston
Camshaft
- Controls opening & closing of valves
- Driven at half speed of the crankshaft
Pushrod & cam follower
Transfers motion from camshaft to the rocker arm
Rocker arm
Transfers motion from pushrod to activate valves
Diesel engine fresh water cooling system
- Cools cylinder block & cylinder head
- Closed loop system
- AL39 mixed with water 50:50
- Contains corrosion inhibitor & antifreeze
Engine block water passages
- Allow water to circulate thorugh engine for removal of heat
- Known as ‘Water jacket’
Diesel engines Salt water cooling circuit
- Open loop system
- Fitted to cool the fresh water & lub oil as they pass through the heat exchangers
What is Valve overlap?
- When the intake and exhaust valves are open at the same time
- Occurs towards the end of the exhaust stroke
- Provides more time for air to enter cylinder
Why is valve overlap needed?
Because as the speed of the engine increases there is less time spent on the induction stroke,so the intake valve opens sooner
Why does Camshaft run at halfspeed of Crankshaft?
In a four-stroke engine, the piston travels up and down the cylinder twice during each complete engine cycle, which corresponds to two full turns of the crankshaft. During that time, we only want the intake and exhaust valves to open and close once, so we only want the camshaft to turn once during the same cycle.
