Set 12 MEK motor MEO Class4 E pariksha uestions

1. In a uniflow scavenged marine 2-stroke diesel engine, the scavenge ports in a cylinder liner are machined:
Only for a part of the circumference, at an angle almost tangential to the circumference of the liner
All around the circumference at right angles to the circumference of the liner
only for a part of the circumference, at right angles to the circumference of the liner
All around the circumference at an angle almost tangential to the circumference of the liner

2. In order to reduce thermal loading on the upper part of the liner and increase the effectiveness of cylinder lubrication, modern 2-stroke marine diesel engines are designed to have:
Cermet coated piston rings, bore cooled liners and uniflow scavenging
High top land of piston crown and deeper cylinder cover with top land of crown extending into cylinder cover at TDC
Low top land of the piston crown with bore cooled cylinder liner
Bore cooled cylinder liner and bore cooled piston crown with toroidal shape combustion chamber

3. Which of the following statements correctly describes the phenomenon of surging in a 2-stroke crosshead type engine?
Due to sudden increase in engine load the exhaust gases may flow back through scavenge ports causing surge
Due to sudden decrease in engine load the turbocharger pressure ratio drops . This causes high pressure downstream of T/C in scavenge trunk causing flow reversal of scavenge air
Due to sudden increase in engine load , the T/C turbine rpm may increase suddenly increasing the compressor pressure ratio to surge
Due to sudden decrease in engine load , the turbocharger may stall as the higher pressure downstream in exhaust system may cause reversal of flow of exhaust gases

4. What is meant by elastohydrodynamic lubrication?
Formation of hydrodynamic film under high pressure with minor elastic deformation of mating surfaces, distributing load over a greater area
Addition of extreme pressure additive (EP) to the lubricant
Addition of Viscosity index improvement additive
Addition of elastomer based additives

5. Which of the following will be required to be done in order to reduce sulphur corrosion of Main Engine components
Increasing the atomization pressure of fuel injectors
Fitting exhaust valves with valve rotators
Running engine at or near normal sea load
Decreasing the F.O. purifier feed rate , running two purifier in series one acting as purifier and other as clarifier

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Correct answers: