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Q6. (a) Explain why highly efficient diesel engines tend to produce more NOx than low performance diesel engines.

(b) Describe, with the aid of a sketch, a Selective Catalytic Reduction (SCR) unit for a marine propulsion diesel engine.

(c) Explain why accurate monitoring of the exhaust gas flows entering and leaving a Selective Catalytic Reduction unit are required and how these readings are used to control the reduction chemical supplied to the SCR unit.

Q2. With reference to diesel engine SOX exhaust gas cleaning and pollution control:

(a) State, with reasons, which system parameters are monitored, explaining where the monitoring devices are located, how the data is stored and how data is made available to regulatory authorities

(b) State how pollution of sea water can be caused by the use of SOX exhaust gas cleaning systems, explaining how such pollution is prevented.

Q3. With reference to a main engine fuel system of the high-pressure common rail type:

(a) Sketch a common rail fuel injection system from booster pump inlet to cylinder head fuel valves, labelling the MAIN components.

(b) Explain how the fuel pumps are operated and the common rail pressure is maintained;

(c) Explain how fuel injection timing and quantity is regulated for the common rail fuel system sketched in part (a).

Q4. (a) Explain how the build-up of residue in the scavenge space of a large slow speed two stroke engine is minimised by design, operation, and maintenance.

(b) Explain the possible damage which could be caused by a scavenge fire.

Q5. With reference to power Management Systems:

(a) Describe, with the aid of sketches, a starting air systems;

(b) State the precautions and conditions which must be observed when an auxiliary engine is under control of the Power Management Systems;

(c) Explain how an auxiliary engine is started when under the control of the Power Management System.­

Q6. a) For a large slow speed direct reversing engine, describe in detail the profile of a cam suitable for fuel pump operation in either the ahead or astern mode

b) With respect to cam material, describe the heat treatment employed during manufacture.

c) Explain how the position of the cam relative to the crankshaft is altered when changing from ahead to astern running,

d) State how the position of the cam would be correctly set if it were replaced.

Q7. During recent months It has been necessary to frequently retighten some main engine holding down bolts as the steel chocks have become loose: (a) Explain possible reasons for this. (b) State with reasons why re-chocking using a different material might reduce the Incidence (c) Explain the possible consequences if the situation is allowed to continue unchecked.

Q8.  With reference to fatigue of engineering components;

(a) Draw an S/N curve for steel, showing the fatigue limit and two representative stress cycle condition on the graph

(b) Explain how a component is designed to avoid fatigue failure, suiting the S/N curve drawn in part (a)

(c) Explain how poor maintenance and incorrect machinery operation can result in fatigue failure even though a component is designed to operate below the fatigue limit.

Q9.  A report on the analysis of the main crosshead engine crankcase lubricating oil indicates the following contaminants or property changes. In EACH of the following cases give reasons for the possible causes of the contamination or property change, explaining how the actual cause would be detected; .

A. The presence of fresh water; B. White metal fragments; C. Reduced alkalinity reserve; D. Reduced anti oxidation reserve.