DieselShip's Online Content Library

Q7. A. Which of the following three motors has the poorest speed regulation: shunt motor, series Motor or cumulative compound motor? Explain.

B. A 440V shunt motor takes an armature current of 30A at 700 rev/min. The armature resistance is 0.7ohm. If the flux is suddenly reduced by 20 per cent, to what value will the armature current rise momentarily? Assuming unchanged resisting torque to motion, what will be the new steady values of speed and armature current? Sketch graphs showing armature current and speed as functions of time during the transition from initial to final, steady-state conditions.

Q8. An AC Voltage Of 24 V is connected in series with the silicon diode and load resistance 500 Ohm having forward resistance 1O Ohms. Calculate the peak output voltage.

Q6. A. A series circuit having resistance, Inductance and capacitance is to be operated on a constant voltage supply of available frequency. Indicate graphically how changes will take place in the terms, Reactive terms, i.e. Capacitive reactance and inductance reactance; B. A resistance of 130 ? and a capacitor of 30µF are connected in parallel across a 230 Volt, 50Hz supply. Find the current in each component, total current, phase angle and the power consumed.

Q6. A. What is Prismatic Co-efficient (C_P). Derive the formula C_P = C_b/C_m , where  C_b= Co-efficient of fineness and C_m = midship section area co-efficient.

B. The length of a ship is 18 times the draught. while the breadth is 2.1 times the draught. At the load water plane, the water plane area co-efficient is 0.83 and the difference between the TPC in sea water and the TPC in fresh water is 0.7. Determine the length of the ship and the TPC in fresh water.

Q10. (a). Explain the various efficiencies associated with propeller and shafting arrangement.

(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.

Q8. With the aid of sketches:
a. Explain various lines plan.
b. The half -breadths of waterplane of a ship of 120m length ad 15m breadth are given below:

Calculate i) Water plane area ii) TPC in salt water iii) Cw iv) LCF from Mid-ship

Q9. At a draught of 1.0 m in sea water of density 1025 kg/M3 the displacement of a ship is 900 tonne and the height of the centre of buoyancy above the keel (KB) is O.6m. Values of tonne per centimetre immersion (TPC) in sea water for a range of draughts are given in Table Q1.

(a) Calculate EACH of the following for a draught of 6. Om in sea water:

(î) the displacement; (ii) the height of the centre of buoyancy above the keel (KB).

(b) At a draught of 6.0 m, the height of the longitudinal metacentre above the keel (KML) is 128m and the second moment of area of the waterplane about a transverse axis through midships is 996 728 m4. The centre of flotation is aft of midships.

Calculate the distance of the centre of flotation (LCF) from midships.

Q10. A ship 120m long displaces 12000 tonne. The following data are available from trial results:

V (knots) 10  11  12  13  14  15
sp (kw) 880  1155  1520  2010  2670  3600
(a) Draw the curve of admiralty coefficients on a base of speed

(b) Estimate the shaft power required for a similar ship 140m long at 14 knots.

Q9. A. Explain what is meant by: i. Wave making resistance; ii. Frictional resistance; iii. Eddy-making resistance (6)

B. When a ship is 800 nautical miles from port, its speed is reduced by 20%, thereby reducing the daily fuel consumption by 42 tonne and arriving in port with 50 tonne on board. If the fuel consumption in t/h is given by the expression (0.136+0.001 V3) where V is the speed in knots, estimate: (i) The reduced consumption per day; (ii) The amount of fuel on board when the speed was reduced; (iii) The percentage decrease in consumption for the latter part of the voyage; (iv) The percentage increases in time for this latter period. (10)

Q9. A. State what is meant by the term floodable length illustrating your answer by drawing a typical curve of floodable length of a ship. B. A vessel has a maximum allowable draught of 8.5m in fresh water and 8.25m in seawater of 1.025/m3, the TPC in the sweater being 27.5. The vessel is loaded in never water of 1.012 t/m2 to a draught of 8.44m. If it now moves into seawater, is it necessary to pump out any ballast and if 50, how much?

Q6. A. Explain the significance of the root- mean- square value of an alternating current or voltage waveform: Define the form factor of such a wave form. (6)

B. Draw the circuit of Half-wave rectifier and its output waveform. A diode whose internal resistance is 20𝛀 is to supply power to 1000 𝛀 load from 110 V (RMS) source. Calculate

(i) peak load current, (ii) DC load current, (iii) AC load current. (10)

Q7. 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.