fuel, timing and engine performance Flashcards
2 ancillary equipment that can be driven by timing chain
lo pumps
cooling water pump
camshaft
speed of cam shaft on 4 stroke and 2 stroke
4 stroke is 2:1
2 stroke is 1:1
importance of maintaining fuel at correct viscosity for injection
Good atomisation
less fuel used
importance of testing lube oil regularly
check for water, water can cause corrosion. check for fuel, hfo can cause sludge, mgo can thin the oil and cause a crank case explosion, check the condition of the oil. and you will be able to check the condition of the engine Incase of any metal fragments.
importance of ensuring the rotation of the exhaust valves
creates a more uniform wear to the valve rather than concentrated wear.
prevents sticking
reduces high thermal stress on the valve
actions for the turbo charger repeatedly surging
causes, no fans on, dirty filter, dirty compressor, dirty turbine, EGB blockage.
if it happens you should slow down the engine, this will slow the turbine, then the requirement for air will be lower, start blowers, investigate and do cleaning
air start manifold pipe overheating in one unit
this means that the air start valce is open, stop the engine or on a 2 stroke you can also lift the cam follower off of the cam. this is to prevent an air manifold explosion
actions in a low scavenge air temperature alarm
you would change the charge air cooler temp by the valve to stop the air being as cool
actions for engine miss fires, fuel rail pressure low alarm activates, booster pump pressure is high
this would mean that the filter is high so swap over the filter, and clean the blocked filter
actions for turbo charger repeatedly surging in heavy weather
slow down the engine to reduce the effects of the turbo charger speeding up and slowing down
actions for a turbo charger excessively vibrating at full sea speed
reduce the load, if this works then the it indicates the turbo charger is dirty, so do a turbo wash. if no it indicates damage to the turbo charger.
actions when there is overheating of an air start branch pipe to one cylinder during manouvering
air start valve open
ask bridge to stop and change over engine
actions for high main bearing temperature
slow Down the engine to prevent a crankcase explosion, reduce the load, monitor the temperatures.
how to calculate PLANN
mean effective pressure p=a/l use plannimeter to find area a=lxp length of stroke divided by piston bore speed in revs per second if a 4 stroke divide by 2
effect of early injection
higher to tdc to higher pmax
overloads the unit Imbalance in the unit
possible vibrations
effect of late injection
injection further away from tdc lower pmax
incomplete combustion
high exhaust temps
on a 4 stroke why are tappet clearances essential
they allow for thermal expansion and they control the correct timing of valves and allow the correct combustion
if a tappet clearance is too large
causes late opening, not enough air in and out.
a late opening and early close close can effect combustion
creates shock loads throughout valve spindle
if a tappet clearance is too small
when the valve heats up it will expand and the valve will be held off of the seat.
gases can eat away at the valve.
open early and late close
procedure to start a small diesel engine using a staring handle
check fuel oil level coolant all valves are open engage the handle open the decompression level using lever get up to Speed close decompression lever engine will start
eight reasons for difficulty starting a small engine with the lever
not turning the lever fast enough cold starting conditions no fuel fuel pump not working jacket water not working flooded with fuel dirty fuel filter air filter blocked
tests carried out on a fuel injector after a overhaul
put in test rig
pump up to the breaking pressure
check if it operates, check for dribbling,
check for good atomisation, check there’s no dribbling after the operation
