DieselShip's Online Content Library

Q7. A. What is leakage flux as it applies to the iron-core transformer? How is it taken into account in the analysis of the transformer? (6)

B. The following results were obtained on a 50 KVA transformer: open circuit test-primary voltage, 3300 V; secondary voltage, 415 V; primary power, 430 W. Short circuit test-primary voltage, 124 V; primary current, 15.3 A; primary power, 525 W; secondary current, full load value. Calculate:

(i) The efficiencies at full load and at half load for 0.7 power factor

(ii) The Voltage regulations for power factor 0.7 (i) Lagging, (ii) Leading

(iii) The secondary terminal voltages corresponding to (i) and (ii). (10)

Q6. A. Describe how water tightness is maintained where bulkheads are pierced by longitudinal beams or pipes.

B. A triangular bulkhead is 7 m wide at the top and has a vertical depth of 8 m.  Calculate the load on the bulkhead and the position of centre of pressure if the bulkhead is flooded with sea water on only side:

(i) to the top edge,               (ii) with 4 m head to the top edge.

Q9. A propeller has a pitch ratio of 0.95. When turning at 120 rev/min the real slip is 30%, the wake fraction 0.28 and the ship speed 16 knots. The thrust is found to be 400 KN, the torque 270 KN-m and the QPC 0.67. Calculate:

i. The propeller diameter;

ii. The shaft power;

iii the propeller efficiency;

iv. The thrust deduction factor.

Q10. With reference to fixed pitch propellers:
a. Explain Propeller Slip and Propeller Thrust. (6)
b. The shaft power of a ship is 3000 KW, the ship’s speed V is 13.2 knot. Propeller rps is 1.27. Propeller pitch is 5.5m and the speed of advance is 11 Knots. Find:
i. Real Slip
ii. Wake fraction
iii. Propeller thrust, when its efficiency, η = 70% (10)

Q10. A. Explain the effects on stability when a tank is partially filled with liquid.

B. A ship of 11200 tonne displacement has a double bottom tank containing oil. Whose centre of gravity is 16.5m forward and 6.6m below the centre of gravity of the ship? When the oil is used the ship’s centre of gravity moves 380mm calculate - (i) The mass of oil used; (ii) The angle which the centre of gravity moves relative to the horizontal.

Q7. The values of effective power (naked hull) given in Table Q5 refer to a ship which is to have a service speed of 17.75 knots.

The following data also apply:
appendage allowance = 8%
weather allowance = 15%
quasi propulsive coefficient = 0.7
transmission losses = 3%
engine mechanical efficiency = 85%
ratio of service indicated power to installed machinery indicated power = 0.9

A. Determine the indicated power of the engine to be installed.

B. Determine the speed obtained if all the available power of the engine is used in EACH of the following:
(i) when the ship is running on acceptance trial in calm conditions;
(ii) when operating under actual service conditions.

Q8. A. List the variables which affect the force on a rudder. B. A propeller of 4m pitch has an efficiency of 67%.  When turning at 125 rev/min the real slip is 36% and the delivered power 2800Kw.Calculate the thrust of the propeller.

Q6. A. Explain why the bilging of empty double-bottom or deep tanks below the waterline leads to an increase in GM.

B. the immersed cross-sectional area of a ship 120m long, commencing from aft are 2,40,79,100,103,104,104,103,97,58 and 0m^2 calculate - (i) Displacement; (ii) Longitudinal position of the centre of buoyancy.

Q10. A) Define torque and explain how it is developed in a D.C. Motor. Drive from first principles an expression for the torque developed in a D.C. Motor. (6)

(b) A diode valve, having the following characteristic is connected in series with a resistor of 10,000 ohm to a 240 V d.c. supply. If a resistor of 40,000 ohms is connected between the anode and cathode, determine the current through the diode.

Q6. A. With reference to dynamical stability, describe the effect of an increase in wind pressure when a vessel is at its maximum angle of roll to windward.

B. An oil tanker 160m long and 22m beam floats at a draught of 9m in seawater. Cw is 0.865. The midships section is in the form of a rectangle with 1.2m radius at the bilges. A midships tank 10.5m long has twin longitudinal bulkheads and contains oil of 1.4 m3/t to a depth of 11.5m. The tank is holed to the sea for the whole of its transverse section.  Find the new draught.

Q6. A box-shaped pontoon is 36 meters long, 4 meters wide and floats in salt water at drafts F-2.00m, A-4.00m. Find the new drafts if the pontoon now passes into fresh water.

Q9. A. Describe how the distribution of mass within the ship affects the rolling period;

B) The ½ ordinates of a water plane at 15m intervals, commencing from aft, are 1, 7, 10.5, 11, 11, 10.5, 8, 4 and 0m. Calculate:

(a). TPC;

(b). Distance of the centre of flotation from midships.

(c). Second moment of area of the water plane about a transverse axis through the centre of flotation.