US1031545A - Screw-propeller. - Google Patents

Description

O. G. HALVORSEN.

SCREW PROPELLER.

APPLICATION FILED NOV. 14, 1910.

Patented July 2, 1912.

2 SHEETSSHEET 1.

we R

O. G. HALVORSEN.

SCREW PROPELLER.

APPLICATION FILED NOV. 14, 1910.

Patented July 2,1912.

2 SHEETS-SHEET 2.

' ED STATES PATENT onnica.

OLE GU-NEBIUS HALVORSEN', 0F TBONDHJEM, NORWAY.

SCREW-PROPELLEB.

Specification of Letters Patent.

To all whom "it may concern:

Be it known that I, OLE GUNERIUS HALVOR- SEN, a subject of the King of Norway, residing at Trondhjem, Norway, have invented certain new and useful Improvements in Screw-Propellers; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, refer- .ence being had to the accompanying drawings, and to letters or figures of reference marked thereon, which. form a part of this specification.

This invention'relates to screw propellers and the object of the invention is to provide a screw propeller, which is so formed, that the particles nearest to the face of the propeller blades are prevented from describing paths relative to said surface, other than true screw lines lying on the surface of a cylinder, the longitudinal axis of which coincides with the axis of rotation of the propeller.

Figure 1 illustrates a propeller for determining the paths of the water particlesacross the face thereof. Fig. 2 is a diagram illustrating the method of determining at what point along the propeller blade the water will move across the same in a true helical path. Figs. 3, 4 and 5 are, respectively, a plan, a side elevation and an end view of a propeller blade made in accordance with my invention with various positions of the generatrix projected into the planes of these figures. Figs. 6 and 7 show. two forms of generatrix for a propeller face. Fig. 8 illustrates the method of determining the surface of a four bladed propeller, and Fig. 9 shows the method of determining the shape of the generatrix for the face of a propeller blade.

By experiments made by me with a propeller in water, it is substantiated that the particles of water nearest to the face during 1 the propellers rotation do not'all describe true screw lines in relation to the'axis of roopening on the pressure si e of the blade.

The'blade is coated with black asphaltum varnish and the channel in the shaft connected with a reservoir of petroleum.

The propeller is set in rotation in a suitable vessel, allowing a circulation of the water, so that it will pass thepropeller at a right angle to its plane, and thereupon petroleum is pum ed into the channel. Petroleum then will pass out in fine streams through the orifices c and take part in the movement of the water nearest to the surface of the blade; after a short while the petroleum'will have dissolved the varnish, and lines will be visible commencing at the orifices and crossing the blade, as indicated in the drawing. These lines will as shown not be concentric screw lines, but they will diverge rearwardly, assuming a uniform radial pitch and imagining the real paths of the water particles drawn on the face of the blade, the continuation of the tangents to these paths will, according to what the trials show, at all distances from the axis of rotation reckoned from the center line of the blade cut one another at the same point (point of convergence), the face of the blade being thought twisted to form 'a plane perpendicular to the axis of rotation. Thls is illustrated in Fig. 2, in which the lines m n Patented July 2, 1912.

Application filed November 14, 1910. Serial No. 592,306.

and pq represent tangents to two spontaneous actual paths described by the particles of water. The continuation of these tanents cut one another'in the point which is then the point of convergence for all of the tangents to the paths for a given pitch pitch d b f ra 1o d-iameter an a grven num er 0 blades. .If the line a 1' be drawn parallel to the Xaxis, the distance between the former and. latter will indicate the radius of the blade at which the path of the water particles naturally describe part of a true screw line or helix. At both sides of this place the real paths donot coincide with the true screw line. The special point of convergence a lies on the curve II, which contains the pointseof convergence, or is the locus of the ,fioints of convergence for all ,two bladed propalers. The experiments have also substantiated that the location of the point of convergence on one and the same curve is dependent upon the pitch ,ratio of the blade, and not upon the numloer of revolutions. The curves III and IV- are thus corresponding points of convergence for the 3-bladed and t-bladed propellers of the same pitch. It is evidentfrom this that the coordinates of the oint of convergence for the same pitch ratio vary with the number of blades of the propeller.

The peculiarity -of the curves II, III and IV is now shown by the above. If the numher of'blades and the pitch ratio of the propeller tobe constructed are agreed upon, a pointof convergence corresponding to these may be found on the curve III as for instance b,. The coordinates of this point'will now bedecisive for the,form of the propeller blades in a way, which shall be described later. The ordinate to the point I), will now, according to the above, indicate that place on the face of the blade of the ,pro-

peller, wherethe path of the water particles naturally coincides with the true screw line. By the above presentation of the real facts, it is evident that there arise during the rotation of the propeller radial movements of the particles of water nearest to the face of the blade, which do not aifect the work of propulsion of the propeller. In order to prevent the formation of the above mentioned. motion of the Water, I suggest giving the generatrix of the propeller-blade such a form, that there come into existence radial components of pressure opposite in direction and equal in magnitude to those, that produce the useless radial motions of water.

Thereby the water relative to the faceof the blade will describe paths, thatcoincide with real screw lines.

In the following I shall now proceed to explain how a. propeller blade is .to be formed in accordance with my invention.

Fig. 3 shows the projection of the face of a propeller blade on 'a plane perpendicular to the axis of rotation of the propeller. The lines O6, 0-7, 0-8, etc., represent the generatrix of the face in different angular ositions. The projection of the generatrix in this plane is a straight line. Fig. 4 shows the projection of the same face on a radial plane. The projection of the generatrix in this plane will be the curved line O5, the

position of which, 0-6, O -7, etc., corresponds to 0-6, 0-7, etc., in Fig. 3. Fig. 5 shows an end view of the face, and the generatrix in different angular positions projected on the plane of the paper.

Regarding the form of curvature of the generatrix this must be made in-such a way, according to the preceding, that there occur as a consequence of the curvature ofthe generatrix, radial pressure components equal in value but reverse in direction to the previously mentioned forces, which'produce the radial motions of the water. Fig. 4 shows that the generatrix has a tangent per endicular to the axis of rotation 00 of t e propeller. This tangent touches the generatrix at the point 03, the distance of which, from the axis of rotation, is equal to the ordinate of the point of convergenceras a't'this distance from the axis of rotation the particles of Water,according to the above, moverelatively to the face in a true screw line. The special case shown in Fig. 4 holds good for a 3-bladed propeller, where the relation between the dialneter of the-propeller and the pitch is for instance 0,8. For this case the point of convergence then is to be found on the curve III and is marked 6,, Fig. 2. As, according to Fig.1 the water within the neutral line b,s (the line parallel to X-axis through the point of convergence 6, has a tendency to be sucked in toward the center of rotation, a tendency, the degree of which is dependent on the distance of the point considered from the axis of rotation, the generatrix must be' givensucha form that there arises all over on this part a radial outward pointing pressure componentflthe magnitude of which is equal tothe above mentioned, inward striving tendency of the water at the point considered. In the same -manner the part of the generatrix outside the neutral line b,s must be given a form. which produces radial inward pointing pressure components. For this special case, with the point of convergence b the generatrix will then obtain the form shown in Fig.

4, viz. O5, where distance of'ol from OO is equal to the ordinate to b, in Fig. 2. The form of the generatrix will, as the preceding representation shows, be corripletely dependent upon the number of blades and the x location of the pointof convergence on the obtain the form for instance of Fig. 6, for the point of convergence (2 on the curve II,

Fig. 2 (for a 2-bladedprop'eller), where the relation between the diameter of the propeller and pitch is for instance :0,3 and the form-of'Fig. 7 for the point of convergence 0, on the curve IV, Fig. i2 (for a l-bladed propeller), where the relation between the diameter of the propeller and pitch is for instance =1,0. Fig.6 shows that the outer convergence point d (see above) falls outside the diameter of the propeller, which is easily seen by Fig. 2, as the ordinate of the point of convergence (1 is larger than the radius of the propeller.

I shall now give the necessary particulars for designing a fourbladed propeller according to the principles above explained. Referring to Fig. 8, the curve IV may be drawn by means of the following table, which gives the coordinates w and 3 for the point of convergence for six different pitch ratios. The first column contains the figure represent- .105 curves II, III and IV, Fig. 2. The consequence of this is, that the generatrix will pendicular to the same.

ing the ratio between the diameter of the propeller and the pitch ratio.

The form of the generatrix maybe determined by means of the following table, reference being had to Fig. 9. m represents the y- I ?;-',%==0,5= 1,440 0, 00 ordlnates expressed as a fraction of the ra- -0,0; 1 502 0 707 D =0,7= 11010, 01000 d1us and 70 represents the absc1ssse. =0,a: 1,025 0,001 2 0,0: 2,020 0,5 0

m=Q.3 "m=0,4 1n=0,5 m==0.6 m=0,7 m=0,8 m=0,9 I m=-1,i) 1 l 1,11: I

| Diameter l =a7 0, 050 0,004 0, 010 0,002 0 0,010 0, 004 1 0, 074 -0,s... 0,000 0,011 0,004 0 0,000 0,020 0,000 0,100 =0,e0.. 0,025 0,0010 0,0010 0,000 0,000 0,000 0,110 =0,9... 0,017 0,000 0 0,002 0,013 0,030 0,071 0,125 =1,o 0,000 0,001 0,002; 0,004 0,015 0,034 0,003 0,102

The numerals in both tables are the actual measures in feet or meters for a propeller radius measuring 1 foot or 1 meter respectively. To find the actual measures for a, propeller of another radius, the numerals must be multiplied by the radius in question.

It will also be understood from the above account that the generatrix need not necessarily be bent in a plane through the axis of rotation as considered above. The same eflz'ect on the water-particles can also be obtained by curving the generatrix in a plane perpendicular to the axis of rotation, a curvature, which in the same manner is based on the principle treated above and shown in Figs. 1 and 2. The projection of the generatrix in a plane through the axis of rotation will then be a straight line per- Finally the same effect on the particles of water can be produced by varying the radial pitch of the blade, a variation which will likewise be determined according to the above treated law shown in Figs. land 2.

Experiments have proved, that the same.

result as in water is obtained movlng 111a1r.

What I clalm is:

by a propeller formed by a curved generatrix dependent upon the angle formed between a radius and a tangent to the generatrix at the point in question, said generatrix varying from point to point in accordance with the relative magnitude of radially directed forces OLE GUN ERIUS HALVOBSEN.

Witnesses:

JOHN Honsr,

Inonnonc ROKNESS.

acting on the particles of the medium in F A screw propeller the blades of which are

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