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)
Q6. (a) What is the significance of GM-GZ curve. (6)
(b) The pitch of a propeller is measured by means of a batten and cord. The horizontal ordinate is found to be 40 cm while the vertical ordinate 1.15 m at a distance of 2.6 m from the centre of the boss. Calculate the pitch of the propeller and the blade width at that point. (10)
Q9. A ship's speed is increased by 20% above normal for 8 hours, reduced by 10% below normal for 10 hours and for the remaining 6 hours of the day the speed is normal. Calculate the percentage variation in fuel consumption that day from normal.
Q8. (a) Compare Direct current with Alternating current. (6)
(b) A four-pole generator has a flux of 12 mWb/pole. Calculate the value of e.m.f. generated in one of the armature conductors, if the armature is driven at 900 rev/min. (10)
Q9. a) Sketch a schematic arrangement of a three-phase alternator with star connection. (6)
b) A 500V, 3-phase, star-connected alternator supplies a star-connected induction motor which develops 45kW. The efficiency of the motor is 88 percent and the power factor is 0.9 (lagging). The efficiency of the alternator at this load is 80 percent. Determine
a) the line current
b) the power output of the alternator
c) the output power of the prime-mover. (10)
Q6. a) Explain how excitation of the rotor is produced and supplied. (6)
b) A shunt motor has an armature resistance of 0.2 ohms and with an armature current of 120 amperes runs at 750 r.p.m. off a 400-volts supply. Calculate the speed and armature current of the motor if the flux per pole is reduced to 75 per cent of its initial value, the total torque remaining unaltered. (10)
Q7. A 4 pole, lap wound shunt generator delivers 200 A at terminal voltage of 250 V. It has a field and armature resistance of 50 Ω and 0.05 Ω respectively. Determine: (16)
(a) Armature current
(b) Generated e.m.f
(c) Current per armature parallel paths
(d) Power developed
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