Diesel Engines Flashcards
State the three speed ranges of a marine diesel engine.
Low speed(0-200RPM), Medium speed(201-1000RPM), High speed(1000+ RPM)
What is turbo charging?
When an exhaust gas driven turbine to pressurise air flow into the engine cylinders.
What is the purpose of lubricating oil in the main engine.
To minimize the amount of friction between moving components.
What is the purpose of piston rings?
Sealing the combustion chamber so that there is minimal loss of gases to the crank case.
Describe symptoms that would indicate a scavenge fire
hot combustion gases and sparks which by-passed the piston rings into the scavenge space.
How would a Scavenge fire like this be extinguished?
Reduce engine power, cut fuel supply to indicated cylinder, increase oil lubrication, prime C02 system, wait 15-20 minutes.
What is the flash point of oil?
between 200-280 Degrees C
What is a stuffing box and its function ?
Separates the Scavenge space from the crank case.
What is the minimum number of air stars on a 2 and 4 stroke engine?
2 Stroke - 12
4 Stroke - 6
Fill in the blank
When the engine is running, the lube oil ——— supplies oil to the main
bearings, ——- end bearings piston, camshaft and in the case of 4 stroke
engines, splash lubrication is taking place to the cylinder liners, gudgeon
pin etc.
System, Bottom
Fill in the blank
Two stroke engines have separate cylinder lubrication. The main lube oil
system supplies lubrication to the ——head bearings and main ——
Crankcase, Bearings
Fill in the blank ( HT & LT)
—— Fresh water to cool the cylinder heads and turbochargers
Filtered
What are the two methods of slow speed propulsion in two stroke engines?
fixed gear and CPP
what problems are faced when using seawater for cooling.
there can be a buildup of weed and or silt which can build up in the strainers and filters.
Give 4 reasons why we need to use purifier for heavy fuel oil. or why dose
the fuel purification is needed ?
It separates light liquid fuel form solids and sediments.
List 4 safety features of air starting system and explain each of the items.
- Flame Trap
- Spring loaded safety valve or bursting disc
- Staring airline drain valve
- Turning gear interlock (pip-pin)
Describe the two water cooling circuits are used in an auxiliary diesel
engine
The propulsion system is cooled by 2 centrifugal pumps maintaining 4 bar.
Main engine is cooled by fresh water generated from the boiler.
What are the step (Before, during and after) you will follow for carrying
out the inspection of the scavenge space on a large two stroke diesel
engine
Check condition of cylinder liner wall through scavenge ports using mirror.
Slowly bring the piston up from BDC.
Inspect piston top land and piston skirt.
When piston rings are visible through scavenge ports, move piston up and down several times to ensure that rings are freely moving in the piston grooves.
What pressure does the air start require?
20-30 Bar
The downcomer pipes in a water tube boiler are situated between the:
Steam and water drums inside the furnace.
A water tube boiler requires soot-blowing to be carried out:
On a regular and frequent basis.
In a direct drive slow-speed marine diesel engine, how is the propulsion changed from ahead to astern?
By reversing the engines direction of rotation.
Which type of marine engines do scavenge fires occur?
Low speed, large bore 2 stroke diesel engines.
In a steam system water tube boiler, the feed pump…
Pumps the boiler feed water before it enters the steam drum.
What is the temperature for both HFO and DMO
HFO - 130’C
MDO - 25’C
what is the 1-7 of 2 stroke combustion
1-2 Completion of scavenge
2-3 Post scavenge
3-4 Compression
4-6 Fuel injection
6-7 Expansion
7-8 Exhaust blow-down
8-1 Scavenge
