Exam Question

A ship 150 m in length, 24 m breadth, displaces 25000 tonne when floating at a draft of 9 m in, sea water of density 1025 kg/m3. The ship's propeller has a diameter of 5.8 m, a pitch ratio of 0.9 and a blade area ratio of 0.45. With the propeller operating at 2 revs/sec, the following results were

recorded:

Apparent slip = 0.06

Thrust power = 3800 Kw

Propeller efficiency = 64%

The taylor wake fraction Wt = 0.5Cb-0.05

Calculate each of the following for the above condition:

(a) The ship's speed

(b) The real slip ratio

(c) The thrust per unit are of blade surface

(d) The torque delivered to the propeller