Marine Propellers and Propulsion Second Edition.pdf

Alternatively, you can submit your request online by visiting the Elsevier website at http://elsevier.com/locate/permissions, and selecting Obtain permission to select Elsevier material. For information on all Butterworth-Heinemann publications visit our website at http://books.elsevier.com.

Preface to the second edition

Preface to the ﬁrst edition

In each of the book's chapters, an attempt has been made to achieve a reasonable balance between theoretical and practical considerations, so that the information presented will be of value to the practitioner in marine science. This book, which represents a compilation of the subject of propulsion technology, is based on the research of many scientists and engineers around the world.

General nomenclature

Upper case

KQ Propeller torque coefficient KQS Torque coefficient KT Thrust coefficient KTN,KTD Channel thrust coefficient KTP Propeller thrust coefficient KY Lateral force coefficient L Length of vessel or channel. Vessel draft Propulsor thrust TA Aft draft TF Draft forward TN,TD Channel thrust Tp Propeller thrust UT Propeller tip speed.

Lower case

Sufﬁxes

Greek and other symbols

Section stress σa Alternating stress σF Corrosion fatigue strength σi Initial cavitation number σL Local cavitation number σMD Mean design stress. HSVA Hamburg Ship Model Base International Maritime Organization IMO International Standards Organization ISO ITTC International Tank Conference Towing.

1 The early development of

However, it is interesting to note that the general shape of the propeller is adopted. The early development of the screw propeller 7 Brunel for Britain did not follow this type.

Figure 1.1 Hooke’s screw propeller (1683)

The diameters of the propellers varied slightly, with the largest having three blades and the smallest four. This was remedied by a redesign of the propellers particularly with regard to blade shape and section shape.

2 Propulsion systems

Fixed pitch propellers
Ducted propellers
Podded and azimuthing propulsors
Contra-rotating propellers
Overlapping propellers
Tandem propellers
Controllable pitch propellers
Waterjet propulsion
Cycloidal propellers
Paddle wheels
Magnetohydrodynamic propulsion
Superconducting motors for marine propulsion

Early propeller design philosophies centered on optimizing propeller efficiency. The reverse situation is the case in the case of the deceleration channel shown in Figure 2.3(d).

Figure 2.1 Typical ﬁxed pitch propellers: (a) large four-bladed propeller for a bulk carrier; (b) high-speed patrol craft propeller; (c) seven-bladed balanced high-screw design; (d) surface piercing propeller and (e) biased high-skew, low-blade-area ratio

3 Propeller geometry

Frames of reference
Propeller reference lines
Pitch
Rake and skew
Propeller outlines and area
Propeller drawing methods
Section geometry and deﬁnition
Blade thickness distribution and thickness fraction
Blade interference limits for controllable pitch propellers
Controllable pitch propeller off-design section geometry
Miscellaneous conventional propeller geometry terminology

The projected area of the propeller is the area you see when looking forward along the shaft axis. A similar argument applies to the case where the pitch angle is increased from that of the design value.

Figure 3.1 Reference frames: (a) global reference frame and (b) local reference frame

4 The propellerenvironment

Density of water
Salinity
Water temperature
Viscosity
Vapour pressure
Dissolved gases in sea water
Surface tension
Weather
Silt and marine organisms

At the surface, the oxygen concentration is normally in the range of 0.1 to 0.6 percent. Molecule A, which is in the body of the liquid, exerts and receives uniform attraction from all directions.

Figure 4.1 Variation of density with salinity and temperature at atmospheric pressure

5 The wake ﬁeld

General wake ﬁeld characteristics

The resulting downward flow close to the hull and upward flow far from the hull give rise to a rotational movement of the flow in the propeller disc called the bilge vortex. The angle of the tangent to the fuselage surface in the plane of the axis center line (see Figure 5.2) must lie within the range 11 to 37◦.

Wake ﬁeld deﬁnition

In Figure 5.1(b) it is seen that, in contrast to the wake field produced by the 'U' shape hull, a high velocity axial flow field exists for a large part of the propeller blade except for the sector embracing top dead center. place where the flow is relatively slow and in some cases can even reverse direction. The mean axial velocity in the propeller disc is found by integrating the wake field on a volumetric basis of the form:

Figure 5.1 Typical wake ﬁeld distributions: (a) axial wake ﬁeld – U-form hull; (b) axial wake ﬁeld – V-form hull; (c) axial and in-plane wake ﬁeld – twin-screw hull (parts (a) and (b) Reproduced with permission from Reference 1)

The nominal wake ﬁeld

The frictional wake field {wv} arises from the viscous nature of the water flowing over the hull surface. Reconfirmation of the flow at the surface can then occur if the body geometry and pressure gradient become favourable.

Estimation of wake ﬁeld parameters

The wake component due to wave action {ww} is due to the movement of water particles in the system of gravity waves set up by the ship on the surface of the water. In the absence of model tests, the radial distribution of the mean wake field, that is the average wake value at each radial location, is difficult to determine.

Figure 5.5 The wake and thrust deduction coefﬁcient for single-screw ships (Reproduced with permission from Reference 9)

Effective wake ﬁeld

These methods calculate the full velocity field by solving the Euler and continuity equations that describe the flow near the propeller. It is clear that effective wake field evaluation methods such as V-segment, force field and (T–I) approaches are essential to propeller design.

Figure 5.6 Van Lammeren’s curves for determining the radial wake distribution (Reproduced with permission from Reference 6)

Wake ﬁeld scaling

In Hoekstra's method, the component contractions are determined based on the harmonic content of the wakefield. In most design or analysis situations, the engineer is in possession of the model's nominal wake and wants to derive the ship's or full-scale effective wake characteristics.

Figure 5.11 Comparison of model and full-scale wake ﬁelds – meteor trials (1967)

Wake quality assessment

His criteria mainly concern the very important area of the wake peak in the upper part of the propeller disc. The definition of the wake peak for different wake distributions is shown schematically in Figure 5.15.

Figure 5.15 Deﬁnition of the width of the wake peak: (a) single-wake peak and (b) double-wake peak (Reproduced with permission from Reference 19)

Wake ﬁeld measurement

When the direction of flow is important, since all the above pipes are unidirectional, special measuring pipes can be used. They usually comprise main pipes with three or five holes; an example of the latter is shown in Figure 5.19.

6 Propeller performance characteristics

General open water characteristics

It is not propeller rotation speed in (rpm) Start propeller rotation speed in (rev/s) Propeller diameter in (ft). No propeller rotation speed (rpm) Start propeller rotation speed (rev/s) Propeller diameter (m).

Figure 6.1 Open water diagram for Wageningen B5-75 screw series (Courtesy: MARIN)

The effect of cavitation on open water characteristics

Consequently, the line in the diagram defined byφ=0 represents the pole pull condition for the propeller. Vais propeller advance speed in (knots) vais propeller advance speed in (ft/s).

Propeller scale effects

It has been shown that significant differences can occur between the results of the various procedures. When it comes to a ducted propeller, the interaction between the propeller, the duct and the hull is of particular concern and importance.

Figure 6.4 Curves of K T , K Q and η and cavitation sketches for KCD 4 (Reproduced from Reference 15)

Speciﬁc propeller open water characteristics

Fixed pitch propellers
Controllable pitch propellers
Ducted propellers
High-speed propellers

If this is done, this will minimize any trailing edge flow separation or laminar flow on the suction side of the blade. Since the centrifugal component is only a mechanical property of the blade, it is apparently independent of the advance coefficient.

Figure 6.6 Typical controllable pitch propeller characteristic curves

Standard series data

Wageningen B-screw series
Japanese AU-series
Gawn series
KCA series
Lindgren series (Ma-series)
Newton–Rader series
Other ﬁxed pitch series and data
Tests with propellers having signiﬁcant shaft incidence
Wageningen ducted propeller series A very extensive set of ducted propeller standard series
Gutsche and Schroeder controllable pitch propeller series
The JD–CPP series
Other controllable pitch propeller series tests

Each of the propellers in the series was tested in a cavitation tunnel at nine different cavitation numbers;. The main propeller pitch ratios ranged from 0.8 to 1.4 and tests were conducted on SSPA No.

Figure 6.10 Thrust eccentricity and side forces on a raked propeller

Multi-quadrant series data

In the case of the controllable pitch propeller, the number of quadrants is reduced to two, since this type of propeller is unidirectional in terms of rotational speed. Using the fixed pitch definition of quadrants, the two of interest for controllable pitch propeller work are the first and the fourth, since the advance angle is in the range 90◦≤β≤ −90◦ .

Table 6.17 Coefﬁcients for duct Nos. 19A and 37 for equation (6.19) – K a propeller 4-70 (taken from Reference 26)

Slipstream contraction and ﬂow velocities in the wake

As discussed earlier, the amount of standard series data for controllable pitch propellers in the public domain is relatively small; the work of Gutsche and Schroeder (Reference 27), Yazaki (Reference 29) perhaps the most prominent. The coefficients and further equation (6.24) are defined in Table 6.20 for use in the equations; however, it has been found unnecessary for most purposes to be used.

Table 6.18 Fourier coefﬁcients for K a 4-70 propeller in 19A duct (Oosterveld (Reference 25)) [AQ2]

Behind-hull propeller characteristics

Figure 11.5 shows the thrust eccentricity orbit with respect to the centerline of the shaft for a merchant ship. A typical such pattern is shown in Figure 6.25, from which it can be seen that the asymmetry caused by the wake is also manifested here in the growth and decline of the cavity volume.

Propeller ventilation

As expected, the effect of the mixed wake field on the propeller causes a series of fluctuating load components due to the changing nature of the angles of attack of the flow on the blade sections. 2-blade and 5-blade propellers – extension of the 3- and 4-blade B-series.Trans.

Figure 6.24 Typical ﬂuctuation in bearing forces and moments for a propeller working in a wake ﬁeld

7 Theoretical

Basic aerofoil section characteristics

In equation (7.4), the term xcpi is defined as the center of pressure of the airfoil and is the location of the point where the resultant of the distributed load over the section is effective. As expected, the drag coefficient of the section is also affected by the proximity of the other blades.

Figure 7.2 Experimental single aerofoil characteristics (NACA 65-209) (Reproduced with permission from Reference 11)

Vortex ﬁlaments and sheets

The idea of a line vortex or vortex filament can be extended to that of a vortex sheet. The circulation around the vortex sheet is equal to the sum of the powers of all elementary vortices located between aandb and is given by.

Figure 7.5 Vortex ﬂows: (a) two-dimensional vortex and (b) line vortex

Field point velocities

In the case of a vortex sheet, there is a discontinuity in the tangential component of velocity across the sheet. For example, one such theory of aerofoil action might be to replace the aerofoil with a variable strength vortex sheet, as shown in Figure 7.8.

Figure 7.10 Application of the Biot–Savart law to a semi-inﬁnite line vortex ﬁlament

The Kutta condition

146 Propellers and propulsion Ditto. 7.10) These two examples are sufficient to illustrate the procedure behind the calculation of the field point velocities in inviscous flow. However, when a number of eddy filaments are used in combination with a free-flow flow function, it becomes possible to synthesize a flow that has a practical propeller application.

The starting vortex

However, the initial vortex is formed during the starting process and then continues to move steadily downstream away from the aerofoil. Let us now consider C2 divided into two regions, C3 enclosing the initial vortex and C4 the aerofoil.

Thin aerofoil theory

Therefore, the total velocityωn(x) arising from all the vorticity contributions along the airfoil chord is given by. From Figure 7.16 we see that the moment per unit span of the wing is given by.

Figure 7.13 Thin aerofoil representation of an aerofoil

Pressure distribution calculations

The derivation of the relationship between the flow in z-plane and the flow in the true circular plane (z-plane). A velocity distribution corresponding to the additional load distribution associated with the angle of attack of the airfoil.

Boundary layer growth over an aerofoil

When the transition between laminar and turbulent flow occurs, it occurs over a limited distance, and the position of the transition is of considerable importance for the growth of the boundary layer. In the case of the turbulent flow regime, the flow will separate from the airfoil surface in the presence of an adverse pressure gradient, this is where the pressure increases.

The ﬁnite wing

This component is directly related to the lift force and not to the viscosity of the fluid. Figure 7.24 showed that there was a flow divergence on the pressure and suction surfaces.

Models of propeller action

To solve the analysis problem, it is often the case that the longitudinal and time-dependent properties of the effective inflow field are ignored. Vortex lattice models, Figure 7.30, represent one of the more recent developments in propeller theory models.

Source and vortex panel methods

On each of the plates, the circulation density varies from one limit point to. Calculated and measured midspan pressure distributions of a NACA 4412 wing.

8 Theoreticalmethods –

Blade element theory – W. Froude (1878)
Propeller Theoretical development (1900–1930)
Burrill’s analysis procedure (1944)
Lerbs analysis method (1952)

Rankine proposed a simple theory of propeller operation based on the axial motion of the water flowing through the propeller disc. A similar, albeit slightly more complex, result can be derived for the contraction of the slipstream after the propeller.