Q1. Crankcase oil mist detectors have undergone a lot of changes in recent years. Compare the modern types with multiple sensor units with the traditional single sensor type, where sampling was done sequentially. What is meant be addressable sensors.
Q2.a) With the aid of a block diagram describe the operation of an electronic governor fitted to a main engine
b) An engine fitted with an electronic governor behaves erratically during load changes. Explain the possible causes
c) Describe a device fitted in order to safeguard an engine in the event of sudden and complete removal of its load.
Q9. (a) Explain the principles behind de-rating a ship propulsion engine and the benefits. Can a derated engine be run at full power? If yes, under what conditions?
(b) Briefly explain approved procedures for de-rating of an existing propulsion engine.
Q4. Explain each of the following:
A. Why wear down in main bearings is critical to the condition of the crankshaft and propeller shaft system.
B. Why total reliance is placed on frictional grip in conventional built up crankshaft
C. Why hole oils are given large fillets in crankpin and journals.
Q5. A. Briefly describe any one of the manufacturing process involved in semi built or welded construction of crankshaft of large marine engine; B. Give a composition of material used; C. Draw a stress diagram for stress in web of a crankshaft.
Q6. Express your reactions and state the subsequent investigation you would make if a laboratory report on a used diesel engine oil sample indicated the presence of appreciable amounts of:
A. Iron; B. Copper, C. Antimony and Tin; D. Silicon; E. n-pentane and toluene insoluble
Q7. Evaluate the influence of the following factors upon cylinder and piston ring wear rates. (16)
A. Position of rings in relation to piston crown.
B. Spread and proximity of coolant passages from liner wall.
C. Flow rate and specific heat of coolant.
D. Chromium plating of ring faces.
Q8. With respect to VIT in fuel injection give your comments on the following statements.
a) By using VIT 100% peak pressure is achieved at 85% rpm. Thus 100% power is achieved at 85% rpm. This results in fuel saving.
b) VIT is not possible nor used in alternator engines as they run at constant rpm.
c) Breakpoint is the point at which maximum break horsepower is achieved.
d) VIT system can ensure the correct Pmax is achieved irrespective of the fuel used.
e) Electronically controlled engines do not have VIT.
Q9. NOx Tier – III requirements are getting mandatory as per MARPOL Annex IV. IN this context, briefly explain the following: -
a) Working principles and Components in a SCR system.
b) Operational sequence of a NOx control SCR plant.
c) Operational difficulties in SCR systems.
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