FLOW MACHINE

Abstract: An attachment of a blade-shaped element such as a rotor blade (1) in a flow machine is achieved by means of a recess provided in the blade, into which recess there may be inserted an insert member (4) to be held therein by a form bound engagement of its side faces with the side walls of the recess. The support member of the blade, such as a support arm (9), is connected to the insert member, preferably in a pivotal manner, so as to allow adjustment of the inclination of the blade also in operation. The invention is suitable for both rotatable and stationary blades, particularly in transverse flow machines having adjustable blades.

Description: Flow machine The present invention relates to a flow machine, and more particularly to a device for attachement therein of a blade element which has a non-neglectable thickness, e.g. a blade with a drip-shaped profile (like an aeroplane wing) , and in particular a blade which in operation is adjustable as to its inclination. The term "blade" is meant to comprise, in the present description, each struc- tur member, movable or not, which irrespective of its actual function has the general shape of a blade of the above described kind. In flow machines the blade attachement is of great importance for the performance of the machine, primarily due to its influence on flow losses and on the structural strength of the machine with attendant possibilities of operation at high speeds, and with respect to the general safety, of the machine (e.g. a risk for the blade to turn loose and be thrown out of the machine) . For axial machi¬ nes with radial, non-adjustable blades, such as steam turbines or the like, solutions are known, among them a so called fur top attachement, which due to a form-locking meet highly put operational demands. Also for water tur¬ bines of the Kaplan-type are operative solutions for the attachement of adjustable blades known. The known solu¬ tions concern machines in which the blade attachement is located outside the area where the medium flows by which the actual blade is driven, or which itself is driven by the respective blade. However, if a blade, because of the general conception of the machine, has to be attached within the said flow area, considerable design problems arise, in particular with respect to unduely high flow losses. The invention is particularly concerned with the last mentioned instance. In machines through which the medium flows in a di¬ rection transversely to the rotational axis of the machine (so called transverse flow machines) , the blade attache¬ ment has a specially great importance when the machine is comparatively sparsely equipped with blades. Thus, al- ready in the French patent Nr. 604.390, relating to a so called Darrius-rotor, the importance of an (undisturbed) stream line shape for the blades has been mentioned. In transverse flow machines it is typical for the rotor bla¬ des to be during rotation subjected to a varying load, which results in a certain fatigue effect. In transverse flow machines for liquids, the structural strength of the blade attachement becomes critical for the entire const¬ ruction, due to the comparatively high density of the liquid. In particular in water turbines it is important that the blade attachement be not dimensioned only with respect to the normal operational speed, but it must be dimensioned for the racing speed (i.e. the speed which the turbine attains when the braking moment of e.g. a gene¬ rator ceases) . In water turbines, the race speed is of the order of twice the operational speed. The centrifugal forces which have to be taken into consideration when the dimensions are determined are then about four times grea¬ ter than those in the operational state. In machines with blades which are adjustable in operation, the blade at¬ tachement embodies at the same time the pivot element for the adjustment movement of the blade. To minimize wear, sufficient dimensioning of the pivot element,as well as a suitable sealing thereof against polluting agents which may be carried by the medium, is necessary. According to the present invention there is provided a blade attachement which does not or, at most, only mini¬ mally affect the flow, which has a high structural strengt and, at the same time, a secure design. The fatigue strength may be made very high, due to a low notch fatigue factor. In adjustable blades, the pivot element or pivot point may be located optimally relative to the force cent¬ re, as well in the chord direction of the blade, as trans¬ versely thereto. The invention is characterized by the features that are evident from the accompanying claims. According to the invention, the attachement point of a blade is located inside the cross-sectional face of the blade. This loca- lization results in that any type of gondola-like addi¬ tional sstructures for the blade attachement, as has been the practice hitherto, is enirely dispensed with. In flow machines for liquids such gondolas may have an extent of more than 20% of the blade length, and, depending on the dimensioning forces, the occurence of gondolas may result in a decrease of the performance of more than 30%. The invention will now be explained more in detail with reference to the accompanying diagrammatical draw¬ ings, which relate to exemplary embodiments, and in which Fig. 1 is a perspective view of a rotor according to the present invention for a flow machine which otherwise is not shown; Fig. 2 shows the cross-section II in Fig. 1 at a larger scale; Fig. 3 shows the same cross-sectinal area, prior to the assembly; Fig. 4 is a plan view of the area around the support arm 9 as seen in the direction of the arrow IV in Fig. 1 ; Figs. 5A and 5B are longitudinal sections along the plane V-V in Fig. 4 through two alternative embodiments; Fig. 5C illustrates a cutter for producing the recess according to Fig. 3; Fig. 6 is a cross-section along the plane VI-VI in Fig. 5B; Fig. 7 is a cross-section along the plane VII-VII in Fig. 5B; Fig. 8 is a plan view, in analogy to Fig. 4, of an alternative embodiment; Fig. 9 is a plan view, and Fig. 10 a side view of the pivot member of Fig. 8; Fig. 11 is a cross-section, in analogy to Fig. 2, through another alternative embodiment, and Figs. 12A, 12B, 12C are corresponding cross-sections through three other alternative embodiments. Identical or analogous parts are provided with iden¬ tical or analogous reference characters in all figures of the drawings . A flow machine, not shown more in detail, has accor¬ ding to Figs. 1 - 7 a rotor 20 which comprises a shaft 21 to which a rotor blade 1 is attached by means of two sup¬ port members (support arms) 9. For lucidity a rotor with one blade only is shown, whereas in practice, of course, a greater number of blades may be provided. In the following, the directions parallel to the shaft 21 are denoted as axial, and the directions parallel to the support arms 9 are denoted as radial. The rotor blade 1 is elongated an extends axialy while it is suppor¬ ted by the support arms 9 at a radial distance R from the shaft 21. Also the number of arms 9 may vary, and may be as well one as more than two. The arms 9 are non-rotatably attached to the shaft 21, whereas the blade 1 is so connected to the arms S, in a manner which will be desclosed more in detail below, as to be pivotable about an axis A-A. The inclination of the blade relative to the support arms 9 may be adjusted by means of a not shown adjustment device of any known kind, and the blade may be locked - if desired, also in opera¬ tion, i.e. during rotation of the rotor - in a selectee position. The blade 1 has, at least in a part of its profile, a non-neglectable thickness t_ in that it proseεεes a drip- shaped profile like an aeroplane wing. The blade 1 is limited by two end faces If, and by an outer (relative to the shaft 21) envelope face Id and an inner (relative to the shaft 21) envelope face le. Both of these envelope faces extend from the leading edge la of the blade and meet or intersect one another at the rear edge lb of the blade. In the thickest portion lc of the blade 1, and at selected distance a_ from each one of the end faces If, is an axially extending elongated recess 2 (Fig. 3) is pro¬ vided, which is limited by two side walls 2a, 2b. The recess 2 has a selected length b, and the side wal s 2a, 2b have, in the embodiment shown, the shape of cylindrical surfaces, r_cre correctly partial cylindrical surfaces pertaining to a common cylindrical surface k with an axis A'-A' wich may coincide with the above said axis A-A. The side walls 2a, 2b may be provided e.g. in such a manner that a cutter 3 (Fig. 5C) , having a spherical or toroidal cutting face, is introduced into the blade 1 through an inlet opening 10 (Figs. 4 and 7) , and is then moved essen¬ tially a distance 0,5b in either direction. Thus, the recess 2 will be terminated by two end faces 2c (Fig. 5B ) in the shape of concave spherical faces (for lucidity, the inlet opening 10 is not shown in Fig. 1) . In each one of the recesses 2 is an insert or pivot member 4 provided which, in the embodiment according to Figs. 1 - 7, is embodied by two halves 4' and 4" which are separated by a gap M, and which are non-rotatably or pivo- tally interconnected by means of a pivot pin 8 (Figs 4, 5, 7) . Each one of the two halves 4', 4" of the insert mem¬ ber is limited by two side faces 4a, 4b, two outer limi¬ ting faces 4d, 4e, one outer end face 4c, and one inner end face 4f. The side faces 4a, 4b have a convex cylind¬ rical shape with the same radius and the same axis ' -A ' as the side walls 2a, 2b of the recesses 2, and, thus they are located at the same mutual distance d as what the mutual distance £ between the side walls 2a, 2b is. The outer limitating faces 4d, 4e have the same shape as the surrounding portions of the outer envelope surfaces Id, le of the blade 1, and they are also located at the same mutual distance _ (Fig. 3) as these. The distance e_ is smaller than the smallest distance c _ (Fig. 2) between the side walls 2a, 2b. The outer end faces may either have the shape of a convex εperical surface with the same l-adius as that of the end faces 2c of the recess 2, and be located at the same mutual distance b (Fig. ) as these, or they may, in an alternative embodiment 2c' according to Fig. 5B, be flat. The inner end faces 4f are flat (Fig. 4) . Inside each half 4', 4 " of the pivot member there is provided an axially extending bore 6 for non-rotatably receiving of the pivot pin 8. In the gap M between the two halves 4', 4" is the support arm 9, which at its end is provided with an opening 9" (Fig. 7) in an eye 9' (Fig. 7), pivotally mounted on the pivot pin 8. Alternatively, and advantageously, the support arm 9 may be non-rotatably secured to a pivotally journalled pivot pin 8. The pivot member 4 is introduced into the recess 2 in such a manner that it is first turned into a position according to Fig. 3, wherein the outer limiting faces 4d, 4e extend essentially perpendicularly to the envelope faces Id, le of the blade. Then, the pivot member 4 is pushed in the direction of the arrow £ into the recess 2, and finally it is turned approximately 90° to the position according to Fig. 2, in which its outer limiting faces 4d, 4e, due to their above described design and, due to the fact that their mutual distance e_ (Fig. 3) is the same as the thickness of the blade 1 in the respective area, "mer¬ ge" with the envelope faces Id, le of the blade. The pivot member 4 is in this position retained either solely by friction (if a sutiable degree of fitting is selected) , or by means of a special locking element, such as the locking plate which will be described below. It should be noted that a rotor blade of the kind in question in opera¬ tion is not subjected to any noticeable torque about the axis A-A. The insert or pivot member 4 which in this way has been moved into its final position is retained within the recess 2 by a form-bound engagement of its side surfaces 4a, 4b with the side walls 2a, 2b of the recess. To achie¬ ve this locking effect, it is required in principle that at least one of the side walls 2a, 2b has a profile shape where an area f between its end edges 2', 2" (Fig. 3) is more spaced from the opposite side wall than is a straight connecting line σ between these two end edges, and that the side face of the insert member, located adjacent to this side wall, is designed for a direct form-bound enga¬ gement with the side wall, or a form-bound engagement with an inserted lockinσ element, which in its turn is in form- bound engagement with the side wall. The last mentioned alternative will be disclosed more in detail in connection with Figs. 12A and 12B, from which it will also be evident that a cylindrical, or in general "round", shape is not the only answer to the above said requisite. When the end faces 2c of the recess are shaped as a concave sperical surface, and the end faces 4c of the insert member 4 are given a corresponding convex shape, then the measure must be taken that the concave spherical surfaces 2c are in one direction, i.e. towards on of the envelope faces le, Id, cut away into flat surfaces or, at least, into a concave cylindrical surface 2cc having at least the same radius as the remaining portion of the spherical surface, in order to allow insertion of the in¬ sert member 4 into the recess 2 (Figs. 4 and 5A) . The just mentioned measure will not be necessary if the end faces 4c' (Fig. 5B) of the insert member 4 are made flat. To lock hte insert member against turning out of the end position, and also to achieve a good stabiliza¬ tion of the insert member 4 in axial direction, locking plates 13 are pushed in along the flat faces 4c, or in straight slots 17 proided in these end surfaces 4c' . The locking plates 13 have deflected end portions 13a which are recessed into the envelope faces Id, le by resting in slots 18 in these envelope faces. At least one end por¬ tion 13a of a locking plate 13 is deflected at first after the plate has been inserted into its place. Similar locking plates may also be utilized with insert members 4 having spherical end faces 4 c , if straight slots 17 are provided also in these end faces, the bottom 17' of which slots then forms a chord to the arc C which, in an axial section, limits the convex end faces, as is shown by a dashed line in Fig. 5A . Due to the shape of the recess 2 having a radius which is big relative to the dimensions of the blade 1, a high degree of fatigue strength is achieved. Seals 11 for the pivot pin 8 are provided in the inner end faces 4f of the insert member 4 . Fig. 8 illustrates the same area as Fig. 4 when a modified insert member 40 according to Figs. 9 and 10 is used. This insert member 40 is introduced into its recess 20 in the sa ' e direction as according to Fig. 3, and is then locked by means of a short, straight-lined displace¬ ment relative to the blade 1. The pivot or insert member 40 consists in the example shown of three zones 40A with hexagonal cross-section, which alternate with two zones 40B with rectangular cross-section. The zones 403 limited by straight side walls are narrower than the broader zones 40A, in which the periphery of the side walls projects beyond the periphery of the side walls of the narrower zones, as will be best seen from Fig. 10. The recess 20 has, in at least one of the envelope faces Id, le, such an opening 21, limited by end edges 20', which comprises alternating narrower zones 20B, the width of which corresponds to the width of the narrower zones 40B of the insert member, and broader zones 20A, the width of which corresponds to the maximum width of the wider zones 40A of the insert member. The narrower zones 20B of the insert member 20 have a selected length 1 and the broader zones 20A have a selec¬ ted length j , whereby both lengths conveniently may be the same. The broader zones 20A of the opening 21 have a length k which is at least equal to the length j, and the narrower zones 20B thereof have a lengt m which is equal to the length i. The recess 20 has along its entire ex¬ tent, such a profile, visible in Fig. 10, which allows accomodation of of the wider zones 40A of the insert mem¬ ber. The zones 20A of the insert member 20 have been provided by removing there the portions o, limited by cashed lines in Fig. 10. The insert member 40 is introduced into the recess 20 with a similar straight-lined movement as in Fig. 3, and more precisely in a position in which its zones 40A and 40B fit into the recess via the∑oneε 20A and 20B, where¬ upon the insert member 40 is displaced axially in tht direction of the arrow F' a distance correrpondi σ to tht- distance m, untill the zones 40A of the insert member are situated in the zones 20B of the recess and are retained there by a form-bound engagement between the respective hexagonal contours abutting one with another. Then, the insert member is, by a suitable locking element, not shown, locked against undeεired axial displacement back into its position of insertion. It is evident from the drawings that the exact shape of the side walls of the broader zones may be selected within wide limits, the illustrated hexagonal shape being an example only. These side walls may, for example, very well be convex cylindrical, as is shown in e.g. Fig. 3, and the side walls of the recess 20 may be concave cylind¬ rical . The support arm 9 may be secured to the insert member 40 in the same manner as in Figs, 1 - 7, e.g. in that the insert member 40 aε shown defines ' one of two identical halves which are united by means of a pivot pin introduced into the bore 6, or, with non-adjustable blades, the sup¬ port arm 9 may be welded to the surface le, as indicated at ' . It should be noted that in the last mentioned instance the recess 20 and the insert member 40 may also extend perpendicularly to the longitudinal direction of the blade 1, viz. in the direction of the cross-section II in Fig. 1, as shown at 9". Of course, the bore 6 is omit¬ ted if the support arm 9 is welded in place. In Fig. 11 there is shown an insert member 41 in a recess 21, which both are limited by cylindrical side walls or faces which are arcuated in the same direction and which have two different radii. If these radii extend from the same axis (which is now situated outside th<r recess 21) , i.e. if all cylindrical surfaces are concent¬ ric, then the insert member 41 may be inserted into th-r recess 21 in a similar manner as in Fig. 3, and more pre¬ cisely by a movement along an arcuate path in the direc¬ tion of the arrow F" . If the cylindrical surfaces are not concentric, e.g. when they all have the same radius, ther- the recess 21 must issue from the end face If of tht t.-lεύt 1 (Fig. 1) , (i.e. the distance a . becomes zero) , and the insert member 41 is inserted into the recess 21 by an axial movement, which is then considerably longer than was the case according to Fig. 8. In Figs 12A and 12B, finally, are shown embodiments with one or two locking elements 30 and 31, inserted bet¬ ween the insert member 42 and 43, respectively, and the recess 22 and 2, respectively. These locking elements have side faces with the same shape as, on the one hand, the adjacent side walls of the recess 22 and 2, respectiv¬ ely, and, on the other hand, as the adjacent side faces of the insert member 42 and 43, respectively. It should be noted that also with all the illustrated shapes of thest side faces, the above mentioned requisite concerning the line σ and the area f_ is met. In Fig. 12C is an exemplary embodiment shown wherein the recess 2a does not occupy the full thickness of the blade 1, so that it penetrates only one envelope face le of the blade 1 with only two end edges 2', 2'a. Also in this instance at least one of the side walls of the recess has to be undercut (in the example shown, both side walls are undercut) and then the reσuisite may be formulated so, that one area fhas to be located further away from the opposite side wall, than does a straight line σj_ which at the respective end edge 2' at right angles intersects a connection line z . between the two existing end edges 2', 2'a (i.e. which in practice defines a tangent to the res¬ pective envelope face le) . Thus, the undercut may gener¬ ally be defined in such a manner that there exists an area f_, spaced from an adjacent end edge, which is situated further from the oppositely located side wall than a refe¬ rence line g_, σ__ which passes through the respective end edge 2' (the reference line in the recesses that penetrate both envelope surface being a connecting line σ to the other end edge of the same side wall, and in recesses that penetrate only one envelope face, being a normal to the connecting line to the other end edge of the recess) . The insert member 44 has, of course, also in tht embodiment according to Fig. 12C the same shape as the re¬ cess 2A, and exhibits only one outer limiting face 44e. As a rule, the embodiments according to Figs. 12A- 12C require that the recesses 2, 2A, 22 start from the end face If of the blade, the elements 30, 31 being conveni¬ ently dimensioned so that they in their final position exert a wedge action, and thus lock the insert member in the respective recess.

Claims: Claims 1. A device for attachment in a flow . machine, by means of at least one support member (9) , of a blade-sha¬ ped element, such as a rotor blade (1) , which is limited by two envelope faces (Id, le) and two end faces (If) , and which has, in at least one portion of its profile, an area (lc) with a non-negligable thickness (t) , characterized in that there is in the blade element, at an attachement point and within the said area, provided a recess (2, 20, 21, 22) which is limited by two side walls (2a, 2b) which along two end edges (2', 2", 2 'a, 20') intersect at least one of the two envelope facess, and by at least one end face (2c, 2cc) which connects the two side walls with each other, at least one of said side walls being undercut in that it has, specedly from its end edge, an area (f) that is located further away from the opposite side wall than is a straight reference line (g, g') which passes through the said end edge, and in that a pivot or insert member (4, 40 - 44) is provided which is limited by two side faces (4a, 4b) , at least one outer limiting face (4d, 4e) and two end faces (4c) , and which insert member is insert- able into the recess up to a final position in which it is locked against withdrawal from the recess by a force act¬ ing perpendicularly to the said envelope faces, due- to a form-bound engagement effect, caused by said undercut, relative to the opposing side face of the insert member, where appropriate via an inserted locking element (30, 315 having a profil shape which establishes a form-bound enga¬ gement with the adjacent side wall and side face, the outer limiting face or faces of the insert member having such a 'shape, and being located in such a manner, that they, in the final position of the insert member, at least approximately form a continuation of the surrounding enve¬ lope face, and that the support member is connectablt to the insert member. 2. A device as claimed in claim 1, characterized in that the side walls of the recess intersect both envelop-; faces, and that the said reference line (g) is a straight connection line between the end edges of the respective side wall at the two envelope faces. 3. A device as claimed in claim 1, characterized in that the maximum depth of the recess is smaller than the thickness of the blade element in the respective area, so that the recess [ A4 ) intersects along two end edges (2 1 , 2'a) only one envelope face, and that the said reference line is a normal which, at the respective end edge, inter¬ sects a connection line (z) to the other end edge. 4. A device as claimed in one or more of the prece¬ ding claims, characterized in that the side walls and the side faces have mutually corresponding cylindrical shapes, and in that one of the side walls is concave, and the side face, which in the final position of the insert is adja¬ cent thereto, is convex. 5. A device as claimed in one or more of the prece¬ ding claims, characterized in that the at least one end surface has at least in part a concave spherical shape, and that the possibly remaining part has concave cylindri¬ cal shape with the same radius. 6. A device as claimed in one or more of the prece¬ ding claims, characterized in that the insert member com¬ prises two halves (4', 4") which are spacedly (M) inter¬ connected by means of a pivot pin, and that the support member is pivotally connected to the pivot pin in said space. 7. A device as claimed in one or more of the prece¬ ding claims, characterized in that the pivot pin is sealed off in the two halves by means of seals (11) in the inner faces (4f) of the two halves. 8. A device as claimed in one or more of the prece¬ ding claims, characterized in that the smallest mutual distance (c') between the side walls of the recess iε greater than is the mutual distance (e) between the outer faces of the insert member, so that the insert member may be inserted into the recess in a direction at right angles to the said envelope faces, and then by a turn of about 90° may be brought into its final position. 9. A device as claimed in one or more of the prece¬ ding claims, characterized in that the insert member is locked in its final position by means of at least one locking plate (13) arranged at at least one end thereof, and which locking plate is inserted into a slot (17) in the end face of the insert member and has end portions (13a) which are deflected in the direction of the envelope faces, and preferably are recessed into the envelope fa¬ ces. 10. A device as claimed in claim 1, characterized in that the insert member has a plurality of narrower zones (40B) with a predetermined length and straight side faces, which zones alternate with broader zones (40A) with side faces which have a periphery projecting beyond the peri¬ phery of the straight side faces, and in that the recesε (20) along its entire extent has a profile that allows accomodation of the broader zones, the opening limited by the end edges (20') of the recess exhibiting at at least one of the envelope surfaces alternating broader and nar¬ rower zones (20A, 20B) , of which the broader zones allow passage to the broader zones of the insert member and are provided in the same number as these, whereas the narrower zones allow passage only to the narrower zones of the recess, and are provided in a corresponding number, so that the insert member, in a position where its different zones are situated at the corresponding zones of said opening, may be inserted into the recess in a direction perpendicularly to the envelope faces, and may then be f locked against withdrawal in this direction by a straight- lined displacement corresponding to the length (j) of one zone.

Inventors: JONSSON ARNE FREDRIK, JONSSON, ARNE, FREDRIK
Applicants: JONSSON PUMPKONSULT
Application year: 1988
Main classification: F01D7
IPC codes: F01D5, F01D7, F01D17, F03D3