Turbocharger

Question 1

1. With reference to main engine turbochargers:

a) Explain their function.

Answer 1

a) To make use of and reduce the amount of waste energy from exhaust gas.
To provide a high pressure air charge for efficient scavenging

Question 2

1. With reference to main engine turbochargers:
   a) Explain their function.
   b) State two advantage of fitting them.

Answer 2

b) Increase the efficiency of the engine Reduce wastages found within older mechanical driven superchargers

Question 3

1. With reference to main engine turbochargers:
   a) Explain their function.
   b) State two advantage of fitting them.
   John Willison IAMI Revision 18
   c) Explain how they are cooled and lubricated.

Answer 3

c) The bearing journals are lubricated from the main engine lubrication oil system via a header, to maintain lubrication after the engine is stopped.
Some older turbines have build in pumps driven from the turbine ends with a small oil reserve.
The casings of older turbochargers are cooled with a water jacket off of the HT system of the main engine.
Newer turbines air from the compressor side is circulated as a cooling medium

Question 4

b) State the function of each of the following turbocharger system components: (i) Suction filters; (2)

Answer 4

b) State the function of each of the following turbocharger system components: (i) Suction filters; (2)

Question 5

b) State the function of each of the following turbocharger system components: (i) Suction filters; (2)
(ii) Exhaust grids; (2)

Answer 5

ii) To collect any foreign debris, metal or otherwise after combustion.

Question 6

b) State the function of each of the following turbocharger system components: (i) Suction filters; (2)
(ii) Exhaust grids; (2)
(iii) Charge air cooler. (2)

Answer 6

iii) To cool the charge air, enabling a larger volume of air for scavenge purposes.

Question 7

3. a) State two reasons for fitting an exhaust gas turbocharger to an engine.
   b) Describe the effect of dirty or restricted:
   (i) Air filters;
   (ii) Exhaust gas turbine.
   c) Outline how the exhaust gas turbine is cleaned.

Answer 7

a) Fewer mechanical losses than mechanically driven superchargers.
Recovery of energy from exhaust gas reducing waste.
b)
i) Loss of engine power, reduced combustion efficiency.
ii) Excessive turbine vibration, potential for sparks within uptake.
c) A measured quantity of solid cleaning media specified by the manufacturer is admitted via a fixed vessel at full load speed.

Question 8

4. With respect to main propulsion engine, state the immediate action to be taken as an EOOW in the event of the following, stating one reason for each. (Any 4 could be asked) a) Turbocharger repeatedly surging;
   b) Excessive vibration from turbocharger at full sea speed;
   c) Air start manifold/branch pipe overheating local to one unit;
   d) Low scavenge air temperature alarm;
   e) Engine misfires “fuel rail pressure low” alarm activates booster pump pressure high. f) Excessive vibration of air start branch pipe to one cylinder during manoeuvring. g) High Main Bearing Temperatures.

Answer 8

a) Contact the bridge and chief engineer; request the engine load be reduced. One unit is producing more power and other is producing less. Due to this the air consumption required by both the turbochargers differs, which leads to surging.
b) Contact the bridge and chief engineer, request the engine load to be reduced as much as possible until vibration stops. Caused by propeller being crashed into water in rough weather.
c) Contact the bridge and chief engineer, request the engine to be slowed or stopped, shut off fuel to the effected unit observe unit down running procedures.
d) Reduce the cooling water flow rate/increase the temperature of the cooling water to prevent water moisture condensing on the liner and washing off the lubricating oil. This prevents scuffing and corrosion caused by the removal of lubrication oil.
e) Inform the bridge and C/E, request the engine speed t be reduced. Change to the second fuel filters in the booster pump. Check water in F.O. service tank, and ensure all valves are in line to the M/E fuel rail. This is caused by blocked booster filters.
f) Inform the bridge and C/E, shut off fuel to the affected unit until manoeuvring is complete then try and source the problem.
g) Contact the bridge and chief engineer, ask the engine loading to be reduced or stopped. Check lubrication oil flows, pressures and temperature