US1441788A - Multiple-blade helicoidal propeller - Google Patents

Description

HLE D APR. 29, I920- FL I Jan. 9, 1923.

M DE CON INCK MULTIPLE BLADE'HELICOIDAL PROPELLER.

lal lldld vrano nn .DE common, or LE Haven. FRANCE.

l MULTIPLE-heaps nnnreolnar, Har man,

. To all whom iii/nary concern Be it known that l, lit lanolin nn :GoNiNon, of 46 .ltlue gid elixl laure, Le ,I larre lfrance, engineer, have invented new anduse 'l ul lint 111K) veinents in .-a lll ultiple l'llade *l'lelicoidal Propeller, which improvements are fully set torth in the following specifieation.

llroni' consideration of a theoretical screw pi o ieller with iili'initely *thin blades it is seelrthat the angleoif incidence-of the liquid ontheblades or the angle of attack is very sinallglior a linoderate anountoftslip. For tt1Tl])l%, fO 21 slip of the sine oil the angle olf attack will vary t'r oni flo to .075. the (maximum value .col'respoinling to that part olirthe. blade whose; inclination is} about l-fiim i dn screws of the lusual ctorin in which the angle oi the leadiirs edge otthe blade is substai'itially greater than the angles of at tackunentioned above, the back of the blade, in theoaseoit a moderate :sllp, will bBSHlP jet-t tola-pressure, the elfectio'l Ewhichis ob vio only detrimental i to el'liciency, seeing that to obtain a given pressure the slip lnnst be increased and this reduces the elhciency.

The object o itithe present invention is to provideia screw propeller whichshallhave an increased efficiency and at the same time which possesses great damping power. 'The blades of propellersconstructed in accordance with this invention are of fusiforl'n section and: have the angle oftheir leading edges of the same order as the angle of attack c01 responding to a n'ioderate slip and are1connected together by. rings so as to ii01111yfl rigid whole. @wing; to the abseneel of 7 objectionable pressures on the backs of the blades the slip necessary for. given thrust \vitlra screw, otgiven diai'neter will be dininished and ,theefliciency oi the scre'wiin" moved in proportion. The ringsare necessary for imparting the desired rigidity to the:bladeswhich arevery thin. Their number; arrangement and dimensions will loose chosen .as to ensure a sufiicient strength. Probably the number of blades is so great that-the width ol. thebla'des canbe reduced.

lhis is of. importanee from the point of view of the utilization ofthepropulsive section (that to say, offthe section otthe cylinder circuinscribing the propeller) hy reasonofthe diminution of the radial dispersionwoli the streams of liquid. rlllurther, by reducing; the width; of the blades the reaction which uthey exert on the hull: which hull, and consequently a greater diameterand a larger propulsive section inay be given to the propeller hllhe slip will then be less to r r. a given thrust and eiiiciency will will beiiiereased.

flll'ieiwdth of the .blades decreases from thegboss to. thel tips .so as to reduce the losses XVlllCll {are due to friction oflthe-water and which occninniostlyat the tips otlfthe blades. ll fer-ably the section of ,the blades e convenand sy n n' etrical so that the 'ust na-(1e up in-substantially equal propo ions of a pressiinre intone lface of the bla ile and .a reduction of pressure or reversed pifis fi' lllQ/r tfll the opposite face. These pressures will be nearly universal. over the whole lengthot theiblade contrary to what happens in lscrew's of the nsualflforrn where theproportions of these pressures may he very unequalbandmay give rise ;to the phen. nenon fo l cavitation if the. decrease of pressurerin certain regions exceeds the pres sure of the atmosphere.

. "Vi ith; a screw constructedin accordance witl this invention, and having small slip, cavitation will be practically eliminated and the propeller may have a large capacity :for overload that ;is to say, in caseof need a thrust"considerably iirencess of the thrust duringnornial working canbe obtained, ii.

the engines;are;capableotf renerating sub stantial overload power. Another advantagein a propeller vaitlraysnlallislip resides .the su'l'istai-itial lessening of the suction eli 'ect exerted by V the screw on the hull.

ll loreover. with this a type of propeller =the a very greattendency to les-sen then-oiling 1J'lfli3,l 0llr)f the ship, especially'lf the ship is provided withseverel screws; the rolling): beingrapidly damped; he etliciencyof propeller-ls asgthe mpingis concerned be increaseth or, z'l or a gi ven slip the thrust-- ship; flhese rings in effect possess will be tar superion to that PDSSBSSQITldDy the i that is to say, proportional to V1) or UX 5 \Vith equality of surface the advantage rela- Fig. 3.

tively to anti-rolling keels will be measured by the ratio Which will rarely be less than 10, and of which the value will be so much the greater as the amplitude of roll is less and the speed of the shi is is greater.

Moreover. the effect of campin exerted by the propeller on'the pitching of the ship will be very eificient. The bridge of the ship will remain practically parallel to the surfacerof the swell. There will result from it a sensible reduction of the excess of power necessary to maintain speed in heavy weather and a possibility of increasing the mean speed of the ship. 1

The ship, when fitted with a propeller made according to this invention may have fine lines without detriment to the maintenance of speed in heavy weather. This results in economy in the power necessary for propulsion.

1 Even when the ship is at anchor, the rin s of the propeller will ensure a considerab e damping effect on the rolling by their action on water agitated by a swell.

Amongst other advantages can becited the checking of falling ofl' at the moment of movement of the helm and the reduction of yawing.

In the accompanying drawing Fig. 1 is an end view and Fig. 2 a section through the axis of a propeller having a plurality of blades according to this invention.

Figs. 3 and 4: are detail views of a portion of a blade and ring, Fig. 3 being an elevation and Fig. 4 a section on the line A'-B, Fig. 5 is an explanatory diagram illustrative of the principle involved in the shape of the propeller blade. The thicknesses have been exaggerated in the drawing for the sake of clearness. The angle of acuteness which varies according to the distance from the axis of the section considered is represented by a.

The propeller consists of a certain number of blades at whose width (Fig; 2) increases from the periphery to the centre. These blades are otfusiform section, preferably symmetrical (Fig. 4) havingja very small angle of acuteness, of the order of'the angle of attack corresponding to a small slip.

Referring to the diagram Fig. 5:

Take for example a section AB of a propeller blade of an infinitely small thickness. Let BC represent the tangential speed of said section AB, and let CD represent the ships speed 0. water with respect to the section .\B is given by BD forming with All the angle generally known as the angle of attack.

For a given ships speed, the said angle of attack will be greater. the greater the tangential speed of the section AB. This angle of attack, and conse uently the specific thrust of the section A. 3. become zero when the tangential speed is equal to BC. such that the point D becomes D. situated on the prolongation of AB.

The ratio g-g gives what is known as the slip. If this ratio is low. the angle of attack will be very small. In practice. the blade must have a certain thickness and the section is more or less a segment of a circle. For a proper working of the propeller. it is desirable that the relative-speed of the water should be tangent to the back of. the blade, in order to avoid a negative thrust. i. e., the angle of acuteness a of the blades edge should be equal to the angle of attack.

One of the characteristics of my pro .ller is the use of blades of small thickness in relation to their width, such that the angle of. acuteness diflers. but slightly from the angle of attack 7 corresponding to a low value of I the slip It is known that the theoretical el'liciency is greater. the smaller the value of the slip. For instance. if the slip ratio BC is equal to 10%, the theoretical elliciency equal to 10:90%.

The blades are connected to each other by annular rings 7/ also preferably of fusitorni section. fixed to the blades in any suitable manner. for example, by autogenous weldmg.

In Fig. 3. the blades are formed of segments having a helicoidal surface such as a mounted and fixed by autogenous welding between two rings 7;, the successive segments of the blade such as (L2 being of greater width as they approach the centre.

Claims:

1. In a helicoidal propeller. the combination of a large number of thin blades of tusiform section and a pluraltiy of rings connecting the blades.

2. In a helicoidal propeller. the combination of a large number of thin blades of fusiform section having an angle of acuteness of the same order as the angle of attack corresponding to a small slip. and a plurality ofrings connecting the blades.

In a helicoidal propeller. the combination of a large number of thin blades of. fusiforin section and of increasing width The relative speed of the from the tip to the root and a plurality of rings connecting the blades.

4. In a helicoidal propeller, the combination of a large number of thin blades of fusiiorm section having an angle of acuteness of the same order as the angle of attack corresponding to a small slip and of increasing width from the tip to the root and a plurality of rings connecting the blades.

In a helicoida]. propeller, the combination of alarge number of thin blades of fusiform section, each blade being formed of a plurality of segn'ients, and a plurality of rings connecting each segment of one blade to the corresponding segment of the other blades.

6. In a helicoidal propeller, the combination of a large number of thin blades of 'lusitorm section having an angle of acuteness of the same order as the angle of attack corresponding to a small slip, each blade being formed of a plurality of segments, and

a plurality of rings connecting each segment of one blade to the corresponding seg ment of the other blade.

7. In a helicoidal propeller, the combination of a large number of thin blades of tusiform section and of increasing width from the 'tip to the root, each blade being formed of a plurality of segments and a plurality of rings connecting each segment of one blade to the corresponding segment of the other blades.

.8. In a helicoidal propeller, the combination of a large number of thin blades of ltusiform section having an angle of acuteness of the same order as the angle of attack corres mnding to a small slip and of increas .ing width from the tip to the root, each blade being formed of a plurality of segments, and a plurality of rings connecting each segment of one blade to the correspond ing segment of the other blades.

In testimony whereof I have signed this specification.

MARCEL na CONTNCK.

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