Controllable Pitch Propellers - Revised Edition

Topics include a brief history, characteristics of CPPs and their resultant applications, forces and moments on propeller blades, constructional and working principles, hydraulic and control systems, installation, operation, ship handling, troubleshooting and maintenance. In addition, there is discussion on cavitation, erosion, noise and vibration.

The book will be a useful source of reference for personnel responsible for selecting and designing machinery systems, building and commissioning ships with CPPs, ship managers, marine engineering students, as well as ships? crews who operate and maintain CPPs.

In a controllable pitch (CP) propeller the blades can be turned simultaneously about their own axes, which are normally perpendicular to the propeller shaft, so that the angles (or pitch) of the blade can be altered. The available range of movement normally includes astern pitch angles so that a reverse thrust can be generates without the need to change the propeller?s direction of rotation.

The first CP propellers were only capable of changing pitch when they were not rotating and under minimal hydrodynamic load. Reliability was poor and such propellers are now only used on small yachts.

CP propellers that were capable of changing pitch while rotating were developed early in the 20th century after diesel engines were introduced and CP propellers became desirable as a means of reversing ships and improving manoeuvrability. These early CP propeller designs had simple mechanical pitch setting mechanisms which were hand-operated and used mainly for trawlers and other small vessels.

Later, the first hydraulically operated CP propellers were introduced and fitted to ocean-going passenger ships.

The CP propeller hub diameters, about 30% of the total propeller diameter, were larger than the hub diameters of fixed patch (FP) propellers which were typically about 20% of propeller diameter, but this was of little significance. CP propellers proved to be sufficiently reliable to be accepted by the Classification Societies and owners, and were subsequently fitted to many coasters with diesel engines to improve manoeuvrability.

After World War II interest in CP propellers increased and many types of ship are now commonly equipped with them. In particular, the use of gas turbines as prime movers for fast warships led to the widespread adoption of high powered CP propellers, which provide for effective reversing and improved manoeuvrability.

CP propellers are now fitter in about 25% of all merchant ships newbuildings, and the trend is increasing although, for some applications, there is growing competition from variable speed electric propulsion motors driving FP propellers.

The latest propeller produced to date has a diameter of 11 metres. It is a three blade propeller and absorbs 15,500 bhp (11,400 kW) at the very low rotational speed of 45 rev/min.

CP propellers are in service at 50,000 bhp (equivalent to 37,000 kW) for warships and 46,000 bhp (34,000 kW) for a merchant ship.

Acknowledgments

Greek Alphabet

List of Figures

List of Abbreviations

Chapter 1 Introduction

Chapter 2 Characteristics of CP Propellers

2.1 Bollard Pull

2.2 Manoeuvring

2.3 Windmilling

2.4 Operation with Different Machinery Modes

2.5 Astern Running

2.6 Zero Thrust Operation

2.7 Full Power Operation

2.8 Crash Stop

Chapter 3 CP Propeller Applications

Chapter 4 Economic Considerations

Chapter 5 CP Propeller Blades and Geometry

5.1 Definitions

5.2 Blade Sections

5.3 Design Pitch

5.4 Pitch Change Effects

5.5 Skew

5.6 Rake

5.7 Blade Outlines and Areas

Chapter 6 Forces and Moments on Blades 39

6.1 Thrust and Torque 41

6.2 Centrifugal Loading 42

6.3 Spindle Torque 43

6.4 Skewed Blades

Chapter 7 Working Principles

7.1 Small CP Propellers ? Inboard Actuation

7.2 Larger CP Propellers ? Servomotor in Hub

7.3 Hubs with Double-Acting Servomotor

7.4 Feathering Propellers

7.5 Adjustable Pitch Propellers

7.6 Materials

Chapter 8 Hydraulic Systems

Chapter 9 Control Systems

Chapter 10 Installation

10.1 Installation Design

10.2 Setting-up at Builder?s Trials

Chapter 11 Operation of CP Propellers

11.1 Before Main Engines are Started

11.2 Before Going to Sea

11.3 Operation at Sea

11.4 Manoeuvring in Confined Waters

11.5 Manual Control

11.6 Emergency Pitch Locking

11.7 Ship Handling Characteristics

Chapter 12 Troubleshooting

Chapter 13 Maintenance

13.1 Maintenance at Sea

13.2 Maintenance in Harbour

13.3 In Dry Dock

13.4 Blade Maintenance

Chapter 14 Cavitation, Vibration and Noise

14.1 Cavitation

14.2 Vibration

14.3 Noise

14.4 High Skew Blades

Chapter 15 Future Trends

Keith Brownlie served as Design Engineer with AEI Turbine Generators Ltd (later GEO) for 13 years, before joining Stone Manganese Marine as Chief Designer, Engineering. He then became Manager, Mechanical Applications at GEC Gas Turbines Ltd, before moving to Stone Vickers Ltd (now Rolls Royce) to become Technical Director from 1982 until his retirement in 1995.