CHAPTER 59 



Predicting the Performance of Propulsion Devices 



59.1 Relationship to Other Chapters 332 



59 . 2 Estimate of Propulsion-Device Efficiencies . 332 



59.3 Open- Water Test Data for Model Screw 



Propellers 333 



59.4 Performance Data from Screw-Propeller 



Design Charts 335 



59 . 5 Performance Data on Paddlewheels and 



Sternwheels 335 



59 . 6 Bibliography on Paddlewheels 335 



59.7 Test Results on Rotating-Blade Propellers . 337 



59.8 Available Performance Data on Hydraulic- 



Jet, Pump-Jet, and Gas-Jet Propulsion 

 Devices 337 



59.9 Performance Data on Controllable and Re- 



versible Propellers 338 



59 . 10 Performance of Miscellaneous Propulsion 



Devices 339 



59. 11 Area Ratios, Blade Widths, and Blade-Helix 



Angles of Screw Propellers 340 



59 . 12 Pertinent Data on Flow Into Propulsion- 

 Device Positions 341 



59 . 13 Data on Induced Velocities and Differential 



Pressures 343 



59.14 The Thrust-Load Factor and Derived Data . 345 



59.15 Approximation of Screw-Propeller Thrust 



from Insufficient Data 346 



59 . 16 Relation Between Thrust at the Propeller 



and at the Thrust Bearing 347 



59.17 Estimates of Thrust and Torque Variation 



per Revolution for Screw Propellers . . . 348 



59.1 Relationship to Other Chapters. The 



form, use, behavior, and performance of many 

 types of ship-propulsion devices are described in 

 Chaps. 15, 16, and 17 of Part 1 and in Chaps. 32 

 and 33 of Part 2. A rather complete discussion of 

 the aspects of efficiency of propulsion devices in 

 general is found in Chap. 34. The application of 

 data on and values of efficiency in the powering 

 estimates for vessels is covered in Chap. 60. 

 Notes, rules, and procedures for the design, utili- 

 zation, and adaptation of the many forms of 

 propulsion device to the many types of ships are 

 described in Chaps. 69, 70, and 71 of Part 4. 

 Cavitation and its effects, as applied to screw 

 propellers in particular, are discussed in Chap. 47. 

 The present chapter endeavors to present, in 

 concise but useful form, some of the quantitative 

 information required by the marine architect 

 who sets out to design a combination of ship and 

 propulsion device. While a great deal of analytic 

 work has been done along these lines, the designer 

 who is called upon to fashion and proportion the 

 propulsion device (s) for a particular ship is to a 

 large extent forced to work ahead from the known 

 performances of existing installations. Unfortu- 

 nately, published data on the behavior of pro- 

 pulsion devices is often inadequate for purposes 

 of predictiort and design. Further, it is often 

 imreliable in the sense that the quantitative 

 data are not completely defined. For example, 

 the source may state that the power developed 



to drive a single device is x horses, without 

 specifying whether this is an indicated, brake, 

 shaft, or propeller power. 



59.2 Estimate of Propulsion-Device Efficien- 

 cies. The matters relating to and the factors 

 governing the efficiency of various kinds of ship- 

 propulsion devices are discussed at considerable 

 length in Chap. 34. For the naval architect and 

 marine engineer who wishes absolute or quantita- 

 tive values of propulsion-device efficiency, there 

 are the following: 



(a) For screw propellers, the expected open-water 

 efficiencies jjoCeta) and the probable range of 

 efficiency for selected characteristics or for charac- 

 teristics commonly used are found readily from 

 the numerous groups of screw-propeller design 

 charts listed in Sec. 70.4 



(b) For other types of mechanical propulsion 

 devices, acting directly on the water surrounding 

 the ship, there are some published data on syste- 

 matic series, such as the paddlewheel data 

 referenced in Sec. 59.6, and some comparisons of 

 efficiency to be found here and there in the tech- 

 nical literature. Two examples of these are the 

 efficiency curves for (1) screw propellers within a 

 fixed shrouding such as a Kort nozzle, (2) Voith- 

 Schneider rotating-blade propellers, and (3) 

 paddlewheels in the three sets of graphs of Figs. 

 34. M and 34. N. However, one serious short- 

 coming of data such as these is the lack of ade- 



332 



