Q1. Marine diesel engines run on the diesel cycle. With the introduction of natural gas as marine fuel, Otto cycle is also employed in some engines. Explain the difference between the two cycles and elaborate on the suitability of natural gas as a fuel in such engines. (16)
Q8. Explain why the use of residual fuels for the operation of large slow speed or of medium speed engines, may be responsible for the following problems with turbocharger nozzles, shrouds and blades and how in each, the problem may be minimized:
A. Build-up of deposits.
B. Hot corrosion.
C. Erosion (16)
Q9. a). If an auxiliary diesel generator over-speeds and runs away while off the load, explain: - i. How it can be stopped,
ii. What is likely to be the reasons for the failure.
b). Give-details of what cheeks are made after the machine has been stopped:
(i) Mechanically, (ii) Electrically.
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. With reference to crankcase diaphragm glands: Explain why effectiveness deteriorates in service.
A. Describe the procedure for renewal of parts so that efficiency is restored. (6)
B. Describe how effectiveness is restored if spares are unavailable. (5)
C. Explain the functions of the upper and lower sections. (5)
Q1. A) Explain with a simple sketch the principle of a hybrid turbo charger, what are the advantages? What are the challenges? (8)
b) Discuss the statement in detail, “Hybrid turbo charger will improve overall plant efficiency”(8)
Q9. If a main engine piston seizes in its liner at sea and it is not possible to replace the unit, explain, in detail, what provisions are made in the engine, to enable the ship to reach port?
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)
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