Exam Question
(a) Define the terms 'pitch ratio', 'real slip ratio' and 'blade area ratio'. (6)
(b) The pitch of a ship's propeller is 6m. At 105 rev/minute the apparent slip is 10% and the real slip is 24%. Calculate the slip and the wake fraction.
Class 4 (4th Engineer)
SC&S
📅 Apr 2023
Reference Answer
### Part (a): Definitions
**(i) Pitch Ratio (PR)**
* **Definition:** The Pitch Ratio is a dimensionless geometric characteristic of a propeller, defined as the ratio of the propeller's geometric pitch (P) to its diameter (D).
$$ PR = \frac{P}{D} $$
**(i) Pitch Ratio (PR)**
* **Definition:** The Pitch Ratio is a dimensionless geometric characteristic of a propeller, defined as the ratio of the propeller's geometric pitch (P) to its diameter (D).
$$ PR = \frac{P}{D} $$
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