DieselShip's Online Content Library

Q9. A. Show how the power that is transferred across the air gap of the three-phase induction motor is represented. Explain the terms. What portion of this is useful power? B. The primary and secondary windings of a 500 Kva transformer have resistance of 0.42 and 0.0019 respectively. The primary and secondary voltages are 11 000 V and 415 V respectively and the core loss is 2.9 Kw, assuming the power factor of the load to be 0.8. Calculate the efficiency on (i) Full load; (ii) Half load;

Q8. A. What is meant by the Admiralty Coefficient and the Fuel Coefficient? (6)

B. A ship of 14900 tonne displacement has a shaft power of 4460 kW at 14.55 knots. The shaft power is reduced to 4120 kW and the fuel consumption at the same displacement is 541 kg/h. Calculate the fuel coefficient for the ship. (10)

Q7. A. Describe the stability requirements of a ship for dry-docking.

(b) A double bottom tank containing seawater is 6m long, 12m wide and 1m deep. The inlet pipe from the pump has its center 75mm above the outer bottom. The pump has a pressure of 70 kN/m2 and is left running indefinitely. calculate the load on the tank top:

 (i) If there is no outlet.

(ii) If the overflow pipe extends 5m above the tank top.

Q6. (a) Describe the relationship between frictional resistance and

(i) Ship’s speed;

(ii) the wetted area;

(iii) surface roughness;

(iv) The length of the vessel.

b) A ship 150m long and 8.5m draught has a rudder whose area is one sixtieth of the middle-line plane and diameter of stock 320mm. Calculate the maximum speed at which the vessel may travel if the maximum allowable stress is 70 MN/m? the centre of stock 0.9m from the centre of effort and the maximum rudder angle is 35 degrees. (10)

Q6. The force acting normal to the centerline plane of a rudder is given by the expression:

Fn = 15.5 A v2 α newtons

Where, A = Rudder area (m2)

v = Ship speed (m/s)

α = Rudder helm angle (degrees)

A ship travelling at a speed of 20 knots has a rudder configuration as shown in Fig Q4. The center of effort for areas A1 and A2 are 32% of the width from their respective leading edges. The rudder angle is limited to 35º from the ship's centerline.

Calculate EACH of the following:

(a) The diameter of the rudder stock required for a maximum allowable stress of 77 MN/m2;

(b) The drag component of the rudder force when the rudder is put hard over at full speed.

Q9. (a) Describe the effects on centre of gravity of slack tanks. (b) A box-shaped vessel 100-meter-long x 20 meters wide X 12 meters deep is floating in salt water on an even keel at 6 meters’ draft. A forward compartment is 10 meters long, 12 meters wide and extends from the outer bottom to a watertight flat, 4 meters long 12 meters wide and extends from the outer bottom to a watertight flat, 4 meters above the keel. the compartment contains cargo of permeability 25%. find the new draft if this compartment is bilged.

Q6. A. Describe how the distribution of mass within the ship affects the rolling period B. A ship of 14000 tonne displacement is 125 m long and floats at draughts of 7.9 m forward and 8.5 m aft. The TPC is 19, GML 120 m and LCF 3 m forward of midships. It is required to bring the vessel to an even keel draught of 8.5m. Calculate the mass which should be added and the distance of the distance of the centre of the mass from midships.

Q10. The end bulkhead of the wing tank of an oil tanker has the following widths at 3m intervals commencing at the deck: 6.0, 6.0, 5.3, 3.6 and 0.6 m. Calculate the load on the bulkhead and the position of the centre of pressure if the tank is full of oil rd 0.8.

Q8. A. What are semiconductor devices? What are its advantages over thermionic devices?

What are semiconductor devices?

B. A 20kVA, 2000/220V, single-phase transformer has a primary resistance of 2.1Ω and a secondary resistance of 0.026Ω. The corresponding leakage reactance’s are 2.5Ω and 0.03Ω. Estimate the regulation at full load under power-factor conditions of.

(a) Unity;

(b) 0.5 (lagging) and

(c) 0.5 (leading).

Q9. a) Explain the concept of Dynamical stability. (6)

b) The wetted surface area of a container ship is 5946 m2, when travelling at its service speed, the effective power required is 11250 KW with frictional resistance 74% of the total resistance and specific fud consumption of 0.22 Kg/kW h. To conserve fuel, the ship speed is reduced by 10%, the daily fuel consumption is then found to be 83.0 tonne

Frictional coefficient in sea water is 1.432.

Speed in m/s with index (n) 1.825.

Propulsive coefficient may be. assumed constant at 0.6.

Determine

the service speed of the ship

the percentage increase in specific: fuel consumption when running at reduced speed. (10)

Q5. A. Explain why the GM must remain positive until the critical instant at which the ship takes the blocks overall.

B. A ship of displacement 10,010 tones has a container of 10t at KG = 7.5m. The container is shifted transversely. A pendulum of length 7.5m defects through 13.5m. GM of ship = 0.76m, KM = 6.7m. Find the distance through which the container shifted. Also find the new KG if the container is removed.

Q7. A. What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance.

b) An 8kw, 230V, 1200 rpm d.c shunt motor has Ra = 0.7W. The field current is adjusted until, on no-load with a supply of 250V, the motor runs at 1250 rpm and draws armature current of 1.6 amps. A load torque is then applied to the motor shaft which causes la to raise to 40 A and the speed falls to 1150 rpm. Determine the reduction in the flux per pole due to the armature reaction.