With reference to fixed pitch propellers:
(a) Explain Propeller Slip and Propeller Thrust.
(6)
(b) The shaft power of a ship is 3000 kW, the ship's speed V is 13.2 knot. Propeller RPS is 1.27. propeller pitch is 5.5m and the speed of advance is 11 Knots. Find:
(10)
(i) Real Slip
(ii) Wake fraction
(iii) Propeller thrust, when its efficiency, η = 70%
Reference Answer
### (a) Explanation of Propeller Slip and Propeller Thrust (6 Marks) #### Propeller Slip Propeller Slip is a measure of the efficiency of a propeller's movement through water. It represents the difference between the theoretical distance the propeller should advance in one revolution and the actual distance it advances. * **Concept**: A propeller operates in a fluid medium (water), not a solid one. If it were screwing into a solid nut, it would advance a distance equal to its pitch (P) for every revolution. However, water is a yielding fluid, so the propeller 'slips' back relative to the water it acts upon. This slip is essential for generating thrust.
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