Alexandria University جامعة االسكندرية
Faculty of Engineering كلية الھندسة
Naval Arch. & Marine Eng. Dept. قسم الھندسة البحرية وعمارة السفن
Ship propulsion systems MR351 منظومات دفع السفن
3rd Year الفرقة الثالثة
Final exam 2007 ٢٠٠٧ امتحان نھاية الفصل الدراسي
Time allowed: 3 hrs ثالث ساعات:زمن االمتحان
Attempt in all questions. Total: 90 marks
Question I [15 marks]
A) Answer by true (T) or false (F)
1. LNG carriers are the main commercial vessels type using steam power
plant
2. Diesel engines can only be operated by light fuels
3. Sleeve bearings use rollers to support the shaft
4. Water lubricated stern tubes are rarely used in commercial vessels
5. For same shaft diameter, roller bearing is larger than sleeve bearing
6. Reversing mechanism is essential with VSP
7. FPP are more suitable for low speed maneuverability of the ship
8. Flexible coupling are fitted mainly to reduce the system weight
9. The transmission system is simpler in case of diesel electric plant
10. A solid shaft can be used with CPP
11. 500 CSt is the viscosity needed for fuel injection
12. More treatment is needed in case of distillate fuels than residual fuels
13. Hydrogen as fuel has low emissions than natural gas
14. Vibration and noise are not important in marine propulsion system
15. The prime mover in nuclear power plants is the reactor
B) Choose the correct answer:
1. Which type of ships is preferred to have multiple engine configuration:
a) Oil tankers b) Tug boats c) Bulk carriers
2. A tug boat is preferably fitted with:
a) FPP b) VSP c) Water jet
3. A nuclear power plant should have a:
a) Gas turbine b) Condenser c) Boiler
4. In an LNG ship, the fuel of the plant is:
a) Diesel b) Steam c) LNG
5. Of the advantages of diesel engines is:
a) Low cost b) Low emissions c) Low noise
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6. All diesel engines have:
a) Turbocharger b) Piston c) Crosshead
7. For a gas turbine plant, the gearbox ratio is in the range of:
a) 1:3 b) 1:6 c) 1:30
8. Hollow shafts may be used to:
a) Reduce weight b) Reduce vibration c) Transfer of fuel
9. Used to reduce the effect of misalignment between engine and gearbox:
a) Thrust bearing b) Flexible coupling c) Muff coupling
10. The prime mover is located outboard in the case of:
a) Podded propellers b) VSP c) CPP
11. Which of the following has more calorific value:
a) Gasoline b) HFO c) MDO
12. Which of the following has more stoichiometric ratio:
a) C2H2 b) C8H8 c) They are equal
13. For the same power and speed, which engine is smaller:
a) Low speed engine b) High speed engine c) Medium speed engine
14. Which part of the engine is subjected to more stresses:
a) Flywheel b) Connecting rod c) Fuel pump
15. In order to reduce the engine emissions, which is used:
a) Exhaust gas boiler b) Exhaust cooling c) Exhaust gas recirculation
Question II [15 marks]
A) Differentiate between the following using neat sketches whenever possible:
1. Two and four stroke cycles
2. Constant pressure and pulse system turbocharging
3. Trunk and cross head pistons
B) What are the suitable methods for the astern operation for the following ships?
1. Large oil tanker
2. RORO ship
3. High speed leisure yacht
C) Classify the following marine diesel engine according to the five main
classification points:
Brake power = 4500 kW
Speed = 600 rpm
bmep = 25.9 bar
no. of cylinders = 9
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Question III [15 marks]
A) A diesel engine produce 5000 BHP @ 500 rpm, it is connected to the propeller
with a 1.5m thrust shaft with 40cm diameter, a 6m line shaft with 35cm
diameter and a 2.5m tail shaft with 45cm diameter.
Find:
- The equivalent shaft diameter
- The system natural frequency ( IE = 2IP and K=2.7x109)
- The node position
B) Draw a simplified fuel system for a twin screw large container ship
C) State only:
1. The types of power transmission shafts in ships.
2. Types of propulsors used in ships.
3. Functions of the transmission system.
4. The primary de-NOx technologies used with diesel engines.
5. Types of propeller shaft bearings.
Question IV [15 marks]
A) What is meant by:
1. COGAS power plant
2. Noise sources onboard ships
3. Right handed propeller
4. DMA and RMA
5. Timing diagram of a 4-stroke diesel engine
B) Prove that for a fuel on the form CnH2n+2 the A/F ratio is given by
4
34.8 1
7 1
C) For the engine cross section shown next:
1. State the type of this engine (2 or 4 stroke)
2. State each number refers to which of the following components:
Piston – Crankshaft – exhaust manifold – camshaft – inlet manifold – fuel
injector – rocker arm – connecting rod
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Question V [20 marks]
You are given the following test data for the 8RTA-48T low speed engine.
Load [%] 50 75 100 110
Torque [kN.m] 528 692 837 893
Speed [rpm] 98 113 124 128
Fuel flow rate [kg/h] 957 1362 1860 2070
Cooling water temp. diff. 9.4 15 22 24.6
Radiation percentage [%] 1.119 0.786 0.576 0.517
The fuel used has 42.7 MJ/kg calorific value, the cooling water flow rate is
constant at 78 kg/sec.
- Draw the engine heat balance ratios (ηbth, Qcw, Qex, Qrad) vs. brake power
- Find the engine mechanical efficiency at full load
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Question VI [20 marks]
The AIDA DIVA cruise ship has 4 medium speed diesel engines, she travels for
2200 nautical miles at 22 knots.
The following data are given for each of the engines and the operating
conditions:
Brake power 9000 kW
No. of cylinders 9
Speed 514 rpm
Stroke to bore ratio 1.419
bsfc 178 g/kWh
Volumetric efficiency 98 %
Cooling water temp. rise 15.5°C
Radiation losses 4%
Cooling water flow rate 36 kg/kWh
Compressor efficiency 85%
Turbine efficiency 90%
Ambient temperature 20°C
Ambient pressure 1 bar
Charge air pressure 3.5 bar
Exhaust temperature after cylinder 405°C
Exhaust temperature after turbine 295°C
Air specific heat at constant pressure 0.24 kCal/kg.K
Exhaust specific heat at constant pressure 0.25 kCal/kg.K
Air specific heats ratio 1.4
Exhaust specific heats ratio 1.33
The fuel used has 42.7 MJ/kg calorific value, 13.89 stoichiometric ratio and 0.93
specific weight.
Find the following:
‐ Engine dimensions ‐ Turbocharger heat balance
‐ Engine heat balance ‐ Volume of fuel tanks
‐ Brake mean effective pressure
‐ Excess air factor
‐ Engine critical speed
Good Luck
Dr. Mohamed Morsy El-Gohary
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