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Q9. A. Briefly describe the maintenance routines carried out for emergency batteries onboard.

B. A power of 36 W is to be dissipated in a register connected across the terminals of a battery, having emf of 20V and an internal resistance of 1Ω. Find (i) What value of resistance will satisfy this condition. (ii) The terminal voltage of the battery for each of the resistances and (iii) The total power expenditure in each case.

Q6. For the network shown in Fig.Q1 calculate each of the following: (a) The current drawn from each battery; (b) The potential difference across the 40Ωresistor and across the 50Ωresistor; (c) The power dissipated in the 60Ωresistor.

Q9.  A. Explain how the voltage regulation of a transformer is defined. Is this quantity large or small for the iron-core transformer? Explain B. A single-phase transformer has 480 turns on the primary and 90 turns on the secondary. The mean length of the flux path in the core is 1.8m and the joints are equivalent to an air gap of 0.1mm. The value of the magnetic field strength for 1.1T in the core is 400 A/m, the corresponding core loss is 1.7W/Kg at 50Hz and the density of the core is 7800 Kg/m3

Q9. A. Describe the situations in which hand regulation might be desirable for operation of generators. (6)

B. Three conductors fitted side by side in the stator of a salient-pole alternator. Each generates maximum voltage of 200V (sinusoidal). The angle subtended at the centre of the stator between adjacent conductors is 20 electrical degrees. If the three conductors are connected in series, find (i) the r.m.s. value of the effective voltage and (ii) the ‘breadth factor’ Using the theory that is the basis of this problem, give one reason why three-phase current has been introduced. (10)

Q10. (a) Explain what is meant by left and right handed propellers, and also explain the rotation of propellers in a twin-screw ship.

(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.

Q7. A box barge 45 m long and 15 m wide floats at a level keel draught of 2 m in sea water, the load being uniformly distributed over the full length. Two masses, each of 30 tonne, are loaded at 10 m from each end and 50 tonne is evenly distributed between them. Sketch the shear force diagram and give the maximum shear force.

Q6. The following data applies to a ship operating on a particular voyage with a propeller of 6 m diameter having a pitch ratio of 0.95:

Propeller speed = 1.8 revs/s

Real slip = 34%

Apparent slip = 7%

Shaft power = 10000 kW

Specific fuel consumption = 0.22 kg/kW-hr

Calculate EACH of the following:

(a) The ship speed in knots;

(b) The Taylor wake fraction;

(c) The reduced speed at which the ship should travel in order to halve the voyage consumption;

(d) The voyage distance if the voyage takes 3 days longer at the reduced speed;

(e) The amount of fuel required for the voyage at the reduced speed.

Q1. A RO-RO ferry of length 80 m has a displacement of 3800 tonne in sea water of density 1025 kg/m3 with BM = 3.4 m. The breadth of the ship at the waterline, between sections 3 and 7 is constant at 13 m. To increase stability, sponsons, 1.8 m deep and of constant plan area are to be fitted as shown in Fig Q1.

The sponsons extend over the midships length between sections 3 and 7, with sponson widths as shown in Table Q1.

For the new condition, there is no change in draught and the load waterline is at mid-depth of the sponson. Calculate the increase in BM due to the sponsons.

Q6. A. What factors influence the frictional resistance of a ship and what formula is used to calculate the resistance? B. A ship of 12000 tonne displacement has a rudder 15m2 in area, whose centre is 5m below the waterline.  The metacentric height of the ship is 0.3m and the centre of buoyancy is 3.3m below the waterline.  When travelling at 20 knots the rudder is turned through 30 .  Find the initial angle of heel if the force Fn perpendicular to the plane of the rudder is given by:  Fn=577 Av2 sin  N, Allow 20% for the race effect.

Q6. A propeller has a pitch of 4.57m. At 100rev/min the real slip is 20 percent and wake speed is I knot.  Calculate the apparent slip percentage

Q10: A. Define hull efficiency and propeller efficiency. B. A ship of 2890 tonne displacement and speed of 14 knots has a machinery mass of 410 tonne. The mass of ship’s machinery is given by the formula: m=  V3 tonne;(i) Calculate the mass of the machinery of a similar ship of 3000 tonne displacement at the corresponding speed; (ii) if the 2890 tonne ship required 2920 Kw shaft power, calculate the shaft power required by the 3000 tonne ship.

Q10: A. What is meant by the Admiralty Coefficient and the Fuel Coefficient?

B. A rectangular watertight bulkhead 9 m high and 14.5 m wide bas sea water on both sides, the height of water on one side being four times that on the other side. The resultant centre of pressure is 7 m from the top of the bulkhead. Calculate:

i) The depths of water

ii)  the resultant load on the bulkhead