DieselShip's Online Content Library

Q1.a) Describe the procedures and equipment used to ensure a ship’s NOx emissions comply with international standards. (8)

b) List and describe the key methods used on board ships to reduce NOx emissions. Discuss how each method functions to lower NOx levels in exhaust gases. (8)

Q2.a) Explain the function of thrust bearings in marine engines and why they are critical for the propulsion system. Define the roles of ahead and astern thrust bearings in marine propulsion systems. Why is it essential to have both types of thrust bearings in a ship’s main engine setup. (8)

b) Explain how the ahead and astern thrust bearings handle the directional thrust generated by the propeller. Discuss the procedures for monitoring their condition and ensuring they are adequately supporting the load in both operational directions. (8)

Q3. a) Describe the purpose and function of an air start distributor in a marine diesel engine. Why is it critical for engine starting operations? (6)

b) Explain how the air start distributor works, including its role in timing the supply of compressed air to the engine cylinders. Discuss how it ensures the correct firing order and timing during the start-up sequence. (5)

c) Describe how the cam profile and rotation are designed to ensure proper firing order and timing in the air start distributor. (5)

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.

Q5. With reference to the crankshaft and running gear of an engine, explain static balance, Dynamic balance, Torque reaction couple, and Critical speed

Q6. Variable injection timing was introduced to bring down SFOC figures, especially over a wide range of power. Explain with a graph the variation in Pmax with respect to engine power, with VIT in use and without.

Explain clearly how the fuel consumption is reduced. How is VIT and FQS achieved in camshaft less engines. (16)

Q6. What is "virtual tappet" in the hydraulically actuated air spring return exhaust valves, and how is it set. Explain why the damage occurs to the seats of the exhaust valves due to furrowing and cutting and how an incident of "valve drop" leading to extensive damage to running gear can occur.

Q3. Describe the developments that have taken place in the design of bearings of slow speed marine diesel engines, including geometry and material, focusing on the reasons for such changes.

Q4. A. Discuss the nature of the forces to which a main engine crankshaft is subjected in normal service and explain how the resulting stress are maintained at a safe limit by design and efficient maintenance respectively.

B. Indicate the circumstances under which the crankshaft may--

i. over stressed; ii. Become defective without being over stressed.