DieselShip's Online Content Library

Q6. A. Sketch and describe a flywheel that would be fitted to a large marine diesel engine; B. Show in the sketches how it is fitted and secured; C. What is the purpose of the flywheel? Recently some engine makers have considerably reduced the size of the flywheel. Explain how this can be done.

Q1. With reference to an engine air starting system

(a) Explain why a slow turning is fitted

(b) State, with reasons, when a slow turning system operates

(c) Describe, with the aid of a sketch, an air starting system, explaining how the slow turning system operates.

Q8. a. Explain why top bracing is used for large crosshead engines. (4)

b. Describe, with the aid of a sketch, a hydraulic top bracing unit for a large crosshead engine indicating where the top bracing is fitted and how it operates. (6)

C. Write instructions for the checking of a large crosshead engine top bracing system and a holding down system. (6)

Q9. (a) Explain why variable exhaust valve closing can be advantageous in the operation of large slow speed main engines.

(b) Explain, with the aid of a sketch, how variable exhaust valve closing is achieved.

(c) Explain how high impact is avoided as the valve closes. (2)

Q9. With reference to tubular heat exchangers explain:

a) How differential movement tubes and body is accommodated when the tube plates are rigidly located in the body,

b) How and why turbulence is imparted to fluid flow through the tubes,

c) Why it has become possible to discard sacrificial anodes in sea water coolers,

d) What is meant by the term ‘guided flow’, with particular reference to oil heaters.

Q4. With respect to piston cooling in large two stroke marine engines;

A. Briefly discuss the relative advantages and disadvantages of oil and water for piston cooling.

B. Sketch a piston for a large two-stroke crosshead engines indicating the coolant flow.

C. State the causes of piston cracking and burning and how it can be avoided.

Q8. a) State the reasons for persistent slackening of holding down bolts of a main engine. (6)

b) i) State the advantages of using non-metallic choking for main engines. (5)

ii) State precautions to be observed when fitting non-metallic chocks in order to ensure accurate chocking. (5)

Q7. Analyse the problem of cylinder liner lubrication with reference to oil injection timing relative to piston position, speed and direction of motion. Describe the worst effects of inaccurate lubricant injection timing and how it can have a detrimental effect on developed power in the cylinder. Describe with sketches the arrangement for conveying the oil through the cylinder jacket. (16)

Q2. With reference to four stroke diesel engine emission control:

(a) Describe how the Miller Cycle operates to control NOx emissions;

(b) Describe, with reasons, the modifications needed for a medium speed engine to operate on the Miller Cycle;

(c) give the advantages and disadvantages of closed against open scrubber systems.