Diesel engine Flashcards
Difference between petrol and diesel engines
A Petrol engine takes in air and fuel, compresses the mixture and then ignites it with a spark plug.
Diesel takes air in, compresses it, injects fuel which causes a spontaneous combustion.
Applicators of diesel engines
- Diesel Generators
- Air Compressors
- Fire Pumps
- Main propulsion engines and Motor Boats
Layout and Cylinder Numbering:
Cylinders are numbered from the FREE END starting with 1,2,3 etc.
Layout of vee engines
With Vee Engines, A and B banks can be identified by looking from the FREE END of the engine and Bank A is on the left, Bank B is on the right
What is the engine block and cylinder block
The block holds the engine components, cylinder linings, crankshaft and suitable mounting for auxiliary systems like the cooling and lubricating systems.
Cylinder head
Closes off the cylinder at the top. It accommodates the injector and houses the intake and exhaust ports, valves and valve gear.
Cylinder head joint
Makes a water, air, oil and gas tight seal between the cylinder block and head.
The sump
The sump acts as a reservoir for oil draining back from the bearings and rocker gear.
Piston
A metal component that reciprocates inside the cylinder to compress the air and receive the pressure forces from combustion.
Piston rings
Provides a sliding seal between the outer edge of the piston and inner edge of the cylinder.
They prevent oil from the sump being burnt and lost
Assist with lubrication
They’re are usually 3 rings per piston
Connecting rod
Connects the piston to the crankshaft.
It hold the gudgeon pin, the end with the pin is called the small end
The end that holds the crankshaft is known as the big end
Gudgeon pin
Connects the connecting rod to the piston
Crankshaft
The role of the crankshaft is to change the pistons reciprocating motion to rotary.
Flywheel
The flywheel is used to promote smooth running during the non power strokes of an engine by storing kinetic energy
Camshaft
It controls the opening and closing of the intake and exhaust valves.
It is driven by the crankshaft and rotates at half the speed of the crankshaft.
Valves
The task of the valves is to open and close the intake and exhaust ports
Push rod
TRANSFERS MOTION FROM THE CAMSHAFT TO THE ROCKER ARMS
Rocker arms
The rocker arm is a pivoting arm that transfers motion from the pushrod to activate the valves
Fuel injector
INJECTS A MEASURED AMOUNT OF HIGH PRESSURE, ATOMISED FUEL INTO THE COMBUSTION CHAMBER
4 stroke cycle
Induction stroke
Compression stroke
Power stroke
Exhaust stroke
Induction stroke
The inlet valve opens, exhaust valve shuts.
Piston moves from TDC to BDC
Increase in volume causes a vacuum to draw air into cylinder
Inlet valve closes just after BDC to improve cylinder charging.
Compression stroke
Both valves are closed
Piston moves from BDC TO TDC to compress the trapped air, this causes an increase in temperature and pressure
When the piston is almost at TDC the injector sprays high pressure atomised fuel. This allows for an “Ignition Delay” of the fuel igniting.
Power stroke
Both valves are closed.
As the piston passes TDC towards BDC the fuel ignites and combustion occurs.
The burning air/ fuel mix causes a rapid increase in temperature and pressure and forces the piston down to BDC.
Exhaust stroke
The exhaust valve is open, the inlet valve is closed. The piston rises from BDC to TDC pushing waste gasses through the exhaust.
Valve overlap
This is a short period where the inlet valve is open at the start of the induction stroke and the exhaust valve is open at the end of the exhaust valve. This aids cylinder charging of fresh air for the induction stroke, and the fresh air entering the cylinder helps purge exhaust gasses and cool the exhaust valve.
Fuel service (header) tank
Maintains a supply use supply of clean, water free fuel.
Tank strainer
Prevents large coarse particles from entering the fuel system
Fuel lift pump
Takes a suction from the tank and delivers low pressure fuel to the fuel injection pump
Filters
Used to remove smaller finer particles before it enters the injectors and pumps
Fuel injection pump
Delivers high pressure fuel to the correct injector at the correct time.
Injectors
Delivers high pressure atomised fuel to the cylinders, returns some fuel via the spill return, the returned fuel cools and lubricates the working parts.
Sump strainer
Prevents large coarse particles entering the sump and lub oil system
Lub oil pump
Supplies high pressure oil to the engine bearings, provides low pressure oil to other parts of the engine.
It is a positive displacement pump.
Has a valve on the discharge side which allows oil to enter the sump.
Priming pump
Provides a method of supplying lub oil to the bearing
Lub oil cooler
Used to cool the oil using a thermostat therefore maintaining temperature.
Reducing valve
Reduces the pressure of the lub oil for specific requirements
Routine lub oil system tests
The test is called kittewake, it tests for water, acidity, insolubles, viscosity and dilution.
Tests are taken every week, results are put in the engine logbook.
Fresh water cooling system
Cools the cylinder block
constructed as a closed loop system
The water is mixed 50/50 with etyhlene glycol. This acts as an antifreeze and corrosion inhibitor.
Fresh water pump
Pumps fresh water around the system under high pressure
Engine block water passages
Allows water to circulate through the engine for the removal of heat
Header tank
Acts as a reservoir to make up system losses and allow for expansion as the water temperature rises.
Heat exchanger
Removes excess heat from the water, cooling is provided by the salt water system circuit
Vent cocks
Used for venting off air when filling the system
Allowing air into the system when draining down the engines coolant for maintenance.
Salt water cooling system
Its a direct flow from the sea, circulates through the coolers and then back into the sea
Fitted to cool the fresh water and lub oil system through heat exchangers
Sea cock
Used to isolate the suction side of the system from the sea
Salt water circulation pump
Circulates the salt water through the system
Lub oil cooler
The lub oil cooler removes the heat from lub oil
Discharge overboard valve
Its purpose is to isolate the discharge side of the system from the sea
Emergency cooling
If the belts on the diesel engine salt water pump fail, the salt water system can be supplied by the main HPSW to keep the engine running.
Coolant testing
The coolant is tested weekly for salinity, density and acidity.
Results are recorded in the engines log book
Safety device- low lub oil pressure
If the pressure falls too low an alarm will be set off, if it falls further the engine will trip.
Inform the MEOOW
Low coolant pressure
If it falls too low an alarm will set off, if it falls further the engine will trip.
Inform the MEOOW
High lub oil temperature
Should the temperature of the oil rise an alarm will be set off, if it continues to rise the engine will trip.
Inform the MEOOW
High coolant temperature
If the temperature rises an alarm will be set off.
If it continues to rise it will trip the engine.
Inform the MEOOW
Engine overspeed
If the speed of the engine exceeds a safe working limit an overspeed device operates to trip the engine.
The engine cannot be restarted until the cause is investigated and removed and the trip is reset.
Diesel engine hazards: Hearing
Ear defenders are to be worn to avoid deafness of the ears.
Diesel engine hazards: High speed rotating and moving machinery parts
Have to be fitted with protective guards around them.
Diesel engines hazards: Fire and heat
High pressure air and fuel is a fire and explosive hazard, engines also reach very high temperatures so safety is important when near the engine and its exhaust system.
Precautions for hazards
Mop up any leaks or spillages to prevent fires.
Protective guards to protect against hazardous machinery parts.
Wear clean overalls, no watches or jewellery and protected toe cap boots.
Store any oily rags in a safe place.
PPE
Eye protection e.g. goggles Hearing protection e.g. ear defenders Hand protection e.g. gloves Respiratory system e.g. dust mask Foot protections e.g. Boots with protective toecaps
Tools
Select the right tool Use it for what its designed for Use in a correct and safe manner Do not leave them laying around Stow them after use Regularly inspect for damgage
