DieselShip's Online Content Library

Q8. A. What is meant by “Resonance” in RLC circuits? Compare the series and parallel resonance circuits.

B. Find the frequency at which the following circuit resonates.

Q7. Two 10 MVA 3 phase Alternator operate in parallel to supply at 0.8 power factor with lagging load of 15 MVA. If the output of one Alternator is 8 MVA at 0.9 lagging. A. Calculate the output of second Alternator. B. Calculate the value of Power factor of second Alternator.

Q7. A. Describe the characteristic of d.c. generator.

B. A d.c. motor takes an armature current of 110 A at 480 V. The resistance of the armature circuit is 0.2 . The machine has six poles and the armature is lap-connected with 864 conductors. The flux per pole is 0.05 Wb. Calculate: (i) The speed; (ii) The gross torque developed by the armature

Q10. a) Describe the various resistances acting against the motion of the ship?

The following data are available from the hydrostatic curves of a vessel.

Calculate the TPC at a draught of 5.05m.

Q9. A. Describe measures which may be taken to improve the stability or trim of a damaged ships.

B. A ship 85m long displaces 8100 tonne when floating in seawater at draughts of 5.25m forward and 5.55m aft. TPC 9.0, GML 96m, LCF 2m aft of midships. It is decided to introduce water ballast to completely submerge the propeller and a draught aft of 5.85m is required. A ballast tank 33m aft of midships is available. Find the least amount of water required and the final draught forward.

Q10. A. Explain what is meant by singing of propeller.

B. A propeller 6m diameter has a pitch ratio of 0.9, BAR 0.48 and, when turning at 110 rev/min, has a real slip of 25% and wake faction 10.30. If the propeller delivers a thrust of 300 KN and the propeller efficiency is 0.65 calculate - i Blade area; ii Ship speed; iii. Thrust power; iv Shaft power v. Torque

Q8. A ship consumes an average of 70 tonne of fuel per day on main engines at a speed of 17 knots. The fuel consumption for auxiliary purposes is 8 tonne per day. When 800 nautical miles from port it is found that only 140 tonne of fuel remains on board and this will be insufficient to reach port at the normal speed. Determine, using a graphical solution, the speed at which the ship should travel to complete the voyage with 20 tonne of fuel remaining.

Q8. (a) Define coefficient of fineness of waterplane area, block coefficient and midships coefficient. (b) A box shaped vessel has length 100m and breadth 12m and floats at a range of drafts from 1m to 10m. Produce curves of KB1, BM and KM.

Q8. A. Describe the fundamental principle of a propeller. (6)

B. A propeller 6m diameter has a pitch ratio of 0.9, BAR 0.48 and, when turning at 110 rev/min, has a real slip of 25% and wake faction 0.30. If the propeller delivers a thrust of 300 KN and the propeller efficiency is 0.65. Calculate - i Blade area; ii Ship speed; iii. Thrust power; iv Shaft power v. Torque (10)

Q9. Describe the effect of cavitaion on: i. The thrust and ordque; ii. The propeller blades B. A ship 150m long and 19m beam floats at a draught of 8m and last a block coefficient of 0.68 i) if the admicatry coefficient is 600 calculate the shaft power required at 18 knots; ii) If the speed is now increased to 21 knots, and within this speed range resistance varies as speed find the new shaft power.

Q5. In some circumstances electrical current may be induced into the shafting of rotating machinery.

a) State the problem that may be caused by this current. (6)

b) Explain with aid of sketches, how currents may be avoided or reduced in the following instances:

(i) D.C machines

(ii) Main shafting fitted with a bronze propeller (10)

Q6.a) Define centre of buoyancy and show with the aid of sketches how a vessel which is Stable will return to the upright after being heeled by an external force (6)

b. An oil tanker of 17000 tonne displacement has its centre of gravity 1 m aft of midships and has 250 tonne of oil fuel in its forward deep tank 75 m from midships. This fuel is transferred to the after oil fuel bunker whose centre is 50 m from midships. 200 tonne of fuel from the after bunker is now burned. (10)

Calculate the new position of the centre of gravity:

(a) after the oil has been transferred

(b) after the oil has been used.