DieselShip's Online Content Library

Q9. A) Define longitudinal centre of gravity (LCG) and longitudinal centre of buoyancy (LCB).(6) B) A vessel, when floating at a draught of 3.6 m has a displacement of 8172 tonne, KB 1.91 m and LCB 0.15 m aft of midships. From the following information, calculate the displacement, KB and position of the LCB for the vessel when floating at a draught of 1.2rn. (10)

Q9. A. Describe the procedure for speed, Power and fuel consumption trials. 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.

Q7. A. Explain how wave profile affects the shear force and bending moment curves.

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 fuel 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

(i) the service speed of the ship

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

Q10. (A) Explain the concept of dynamical stability.

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.

Q6. A. What are factors on which the speed of a motor depends? Discuss them for series and shunt motors. (6)

b) Three equal resistors are connected to a three-phase system, if one resistor is removed find the reduction in load if they are connected in (a) Star, (b) Delta. (10)

Q9. A. Explain the effects on stability when a tank is partially filled with liquid. (6)

B) 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. (10)

Q8. (a) Describe the function of the stern frame. (6)

(b) The water plane area of a ship at 8.4 m draught is 1670 m2. The area of successive water planes at 1.40 m intervals below this are 1600,1540, 1420, 1270, 1080 and 690 m2 respectively. Calculate the displacement in fresh water at 8.4 m draught and the draught at which the ship would lie in sea water with the same displacement. (10)

Q6. A ballast tank is 15 m long, 12 m wide and 1.4 m deep and is filled with fresh water. Calculate the load on the top and short side, if:

a) the tank is just completely full

b) there is a head of 7m of water above the tank top. (16)

Q9. (a) Shunt generators having drooping characteristics are best suited for parallel operation. Discuss (6)

(b) Two 220 V D.C. generators each having linear external characteristics, operated in parallel. One machine has a terminal voltage of 270 V, on no-load and 220 V at a load current of 35 A, while the other has a voltage of 280 V at no-load and 220 V at 50 A. Calculate the output current of each machine and the bus bar voltage when the total load is 60 A. What is the kW output of each machine under this condition. (10)

Q6. (a) Define Centre of Flotation. What happens to the draught and trim of a ship if a small mass is added to the ship at the Centre of Flotation? (6)

(b) A ship of displacement 10010 tonnes has KM 6.7m and GM 0.76m. A mass of 10 tonnes having KG 7.6m is shifted transversely. The deflection of a pendulum of length 7.6m is 0.125m. Find the distance through which the mass is shifted. Also find the position of the new centre of gravity above the keel due to the removal of the same mass. (10)

Q7. (a) Compare constant current method and constant voltage method of charging batteries. (6)
(b) A 24V emergency battery is to be charged from the 110V ship's mains when the e.m.f. per cell has fallen to a minimum value of 1.8V. The battery consists of 12 cells in series, has a capacity of 100 Ahr at a 10 hr rate and the internal resistance is 0.03Ω/cell. If charging continues until the voltage per cell rises to 2.2V, find the value of the variable resistor needed to control the charging. The charging current can be assumed to be equal to the maximum allowable discharge current (10)

Q6. (a) Explain the principle of conservation of charge and its relationship to Kirchoff's current law. (6)

(b) The open-circuit voltage of a cell as measured by a voltmeter of 100 ohm resistance, was 1.5 V, and the p.d. when supplying current to a 10 ohm resistance was 1.25 V, measured by the same voltmeter. Determine the e.m.f. and internal resistance of the cell. (10)