Q1. Common rail fuel injection systems have made a come back in marine diesel engines, the older mechanically controlled system have been replaced by electronic/hydraulic controlled system. Describe, with a line diagram any one type of a modern CR system, mentioning the engine type.
b) Compare the advantages and disadvantages of the common rail fuel injection system with the jerk type of injection system. Give examples of their use in modern diesel engines.
Q2. A. Explain the term Variable Injection Timing (VIT) when applied to fuel pumps and state why a change in timing of fuel injection may be required.;
B. Describe, with the aid of sketches a VIT fuel pump and explain how the change in timing is achieved whilst the pump is in operation
C. Explain how it may be determined that individual fuel pumps are injecting the correct quantity of fuel with the correct timing at a particular pump setting.
Q3. With reference to main Thrust bearing of the pivoting pad type, explain with sketches where necessary –
a) The principle of operation of the bearing
b) The critical clearances and why they are critical?
c) How these clearances are adjusted
d) Why such bearings sometime overheat although the clearances are adequate?
e) How is the lubrication film between faces of collar and thrust pad maintained?
Q4. a) Describe, with the aid of a sketch, an external system for reducing engine NOx emission, explaining the chemistry of the process
b) Explain why Urea is used in the selective catalytic reduction process instead of ammonia.
(c) Explain why the exhaust gas quality must be monitored before and after the selective catalytic reduction unit, stating how such monitoring influences operation of the SCR unit.
Q5. a) Describe, with the aid of a sketch, the arrangement of the Gas and liquid fuel systems at the cylinder of a dual fuel 4-stroke engine, stating the input and output signals at the controller.
(b) Describe the arrangement of the gas fuel piping system used for a 4 stroke dual fuel engine with safety features incorporated.
Q6. Draw a line diagram of a Boiler combustion control system labelling the principal items, explain how the system functions and in particular how feed water supply, fuel supply and air/fuel ratio are regulated to match steam pressure and flow variation.
Explain how these controls can be tested for alarm conditions without upsetting the balance of the system.
Q7. What is meant by ‘Power balancing’ with respect to reciprocating engines? Why is balance desirable and how is it obtained in the case of a large marine engine? What difficulties may be experienced in balancing an engine running at about 500 R.P.M. and how can these difficulties be overcome?
Q8. With reference to Main engine crankshafts:
a) Explain the term axial vibration
b) Describe, with the aid of a sketch, how axial vibration may be minimised
c) State with reasons which bearing would be most at risk due to the effects of axial vibration
d) Describe how damage to the bearing stated in part (c) may be repaired.
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.
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