Patent Publication Number: US-11377960-B2

Title: Shroud having elevations, for a turbomachine compressor

Description:
This application claims priority under 35 U.S.C. § 119 to Belgium Patent Application No. 2017/5764, filed 26 Oct. 2017, titled “Shroud Having Elevations, for a Turbomachine Compressor,” which is incorporated herein by reference for all purposes. 
     BACKGROUND 
     1. Field of the Application 
     The present application relates to a compressor having a profile between-vanes surface. The present application also deals with an axial-flow turbomachine, in particular a turbine engine for an aeroplane or a turboprop for an aircraft. 
     2. Description of Related Art 
     Document US 2007/0059177 A1 discloses a jet engine compressor. The compressor has an annular row of vanes. A platform is associated with each vane and has a three-dimensional relief extending between two successive vanes. Each relief has two elevations that are separated by a sinusoidal channel carved radially into the platform. This geometry improves the aerodynamic efficiency of an axial-flow compressor blading. However, it results in a separation of the flow at the extrados of the vanes. 
     Although great strides have been made in the area of axial flow turbomachine compressors, many shortcomings remain. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an axial-flow turbomachine according to the invention. 
         FIG. 2  is a diagram of a turbomachine compressor according to the invention. 
         FIG. 3  shows two compressor vanes bounding a connecting surface according to the invention. 
         FIG. 4  is a section through  FIG. 3 , as per the line IV-IV. 
         FIG. 5  is a section through  FIG. 3 , as per the line V-V. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present application aims to solve at least one of the problems presented by the prior art. More specifically, the invention has the object of optimizing the compression ratio and corner flow separations at the suction surface. The invention also has the object of proposing a solution that is simple, durable, lightweight, economical, reliable, easy to produce, and simple to maintain. 
     Overall, the invention can be understood as being an elevation having two main peaks—and/or a convex portion having two radial extrema—between two consecutive vanes of a compressor. 
     The invention relates to an axial-flow turbomachine compressor, in particular a low-pressure compressor of an axial-flow turbomachine, the compressor comprising: a rotor rotating around an axis, a stator comprising an annular row of vanes, each vane comprising a leading edge, a trailing edge, a pressure surface and a suction surface extending from the leading edge to the trailing edge, a between-vanes passage with a connecting surface that links the pressure surface of a first vane to the suction surface of a second vane of the row, noteworthy in that the connecting surface comprises: a main protuberance, the main protuberance comprising a first elevation having a first peak and a second elevation having a second peak; an upstream zone upstream of the protuberance and a downstream zone downstream of the protuberance, said zones each being of constant radius RC; a col that links the first elevation and the second elevation, the col having a curve of shortest length linking the first peak to the second peak, all the points of said curve being radially at a distance to the axis that is greater than the constant radius RC of the upstream and downstream zones. 
     According to advantageous embodiments of the invention, the compressor may comprise one or more of the following features, taken alone or in any possible technical combination: 
     The protuberance extends over the majority of the connecting surface. 
     The first elevation and the second elevation are arranged in an upstream half of the protuberance and/or of the vanes of the row. 
     The first elevation extends radially further than the second elevation, from the protuberance and/or from the general level of the connecting surface. 
     The first elevation extends from the pressure surface of the first vane, and may comprise a first peak at a distance from said pressure surface. 
     The second elevation extends from the suction surface of the second vane, and comprises in particular a second peak immediately adjoining said suction surface. 
     The connecting surface has an upstream third extending from the leading edges, the first elevation and the second elevation being contained in said upstream third. 
     The connecting surface comprises four corners defining a median plane, said corners being located at the leading edges and the trailing edges of the vanes, with the protuberance forming a radial increase in material of the connecting surface compared to said median plane, in particular the general plane. 
     Axially, the length of the first elevation is between 30% and 50%—inclusive—of the length of the first vane. 
     Circumferentially, the width of the first elevation is between 40% and 60%—inclusive—of the width of the between-vanes passage. 
     Axially, the length of the second elevation is between 15% and 25%—inclusive—of the length of the second vane. 
     Circumferentially, the width of the second elevation is between 5% and 15%—inclusive—of the width of the between-vanes passage. 
     The surface of the second elevation is at most 5% of the surface of the protuberance. 
     The maximum radial height of the first elevation is greater than or equal to three times the maximum radial height of the second elevation, and/or greater than or equal to ten times the maximum height of the protuberance measured outside the elevations. 
     The compressor comprises a stator having a shroud, in particular an inner shroud, connected to the annular row of vanes, the connecting surface being formed on said shroud. 
     The upstream zone and the downstream zone have a constant radius RC over the circumference and over the axis. 
     The col extends over 40% to 60%—inclusive—of the between-vanes passage. 
     The first and second peaks are arranged axially at the same position. 
     Circumferentially, the first elevation is located opposite the second elevation in the between-vanes passage. 
     The connecting surface, in particular the elevations and the protuberance, is/are in contact with the flow of the compressor. 
     The maximum radial height of the second elevation is greater than or equal to three times the maximum radial height of the protuberance measured outside the elevations. 
     With respect to the connecting surface, the protuberance forms an increase in thickness of 0.30 mm. 
     The protuberance has a downstream half and an upstream half in which the first elevation and the second elevation are contained. 
     The protuberance crosses the passage and/or connects the vanes in the circumferential direction. 
     Each vane has a chord whose angle of inclination with respect to the axis of rotation is less than or equal to: 15°, or 30°, or 40°. 
     The connecting surface is free from hollows, in particular hollows extending over at most: 20%, or 10%, or 5% or 1% of the connecting surface, each hollow being in particular understood as an absence of material when compared to the general plane. 
     At all points, the connecting surface has a quantity of material that is positive or zero when compared to the general plane. 
     The passage comprises an upstream axis connecting the leading edges and a downstream axis connecting the trailing edges, which axes constitute the axial limits of the connecting surface. 
     The first vane and the second vane are vanes that are consecutive and/or adjacent, and/or inclined circumferentially by at most 10° or 5° with respect to one another. 
     The vanes of the annular row are aligned circumferentially, their leading edges and their trailing edges are aligned circumferentially. 
     Axially at the trailing edge, the pressure surface and/or the suction surface is parallel to the axis of rotation of the compressor. 
     Each elevation and/or the protuberance are at an axial distance from the leading edges and the trailing edges. 
     Each vane comprises a joining radius, with the connecting surface extending from the joining radii of the first vane and of the second vane. 
     The elevation is convex, in at least two directions, and/or forms a region of increased thickness on the support. 
     Each vane comprises a chord and a space between its pressure surface and said chord, the first peak being predominantly or entirely within said space, and/or the first elevation being predominantly outside said space. 
     Perpendicular to the chord, the span of the second elevation is smaller than the span of the vane. 
     With respect to the general plane, the elevations have inclinations greater than those of the protuberance. 
     The invention also relates to a turbomachine, in particular an aircraft jet engine, comprising a compressor, this being noteworthy in that the compressor is in accordance with the invention, preferably the row of vanes comprises at least: fifty or eighty vanes. 
     Overall, each embodiment of the invention can be combined with each item of the invention. 
     Compression in the passage increases, as does the flow rate passing through it. Under operating conditions of a compressor, the protuberance and the elevations manage the phenomena of turbulence and flow separation. The flow passing through the passage returns to the suction surface during compression, which limits corner flow separation. 
     In the following description, the terms “inner” and “outer” refer to a position relative to the axis of rotation of an axial-flow turbomachine. The axial direction corresponds to the direction along the axis of rotation of the turbomachine. The radial direction is perpendicular to the axis of rotation. Upstream and downstream refer to the principal flow direction of the flow in the turbomachine. 
       FIG. 1  is a simplified depiction of an axial-flow turbomachine. This specific case is that of a turbofan engine. The jet engine  2  comprises a low-pressure compressor  4 , a high-pressure compressor  6 , a combustion chamber  8  and one or more turbine stages  10 . In operation, the mechanical power of the turbine  10 , transmitted via the central shaft to the rotor  12 , moves the two compressors  4  and  6 . The latter comprise multiple rows of rotor vanes associated with rows of stator vanes. The rotation of the rotor about its axis of rotation  14  thus makes it possible to generate a flow of air and to progressively compress the latter up to the inlet to the combustion chamber  8 . 
     A fan  16  is coupled to the rotor  12  and generates a flow of air which is split into a core flow  18  and a bypass flow  20  that passes through an annular duct (shown in part). The bypass flow can be accelerated so as to produce a thrust reaction which an aeroplane needs to fly. The core flow  18  and the bypass flow  20  are annular. 
       FIG. 2  is a section view of a compressor of an axial-flow turbomachine such as that of  FIG. 1 . The compressor may be a low-pressure compressor  4 . The figure shows a portion of the fan  16  and the splitter  22  for separating the core flow  18  from the bypass flow  20 . 
     The rotor  12  comprises multiple rows of rotor vanes  24 , in this case three. It may be a bladed drum, or comprise vanes attached by means of a dovetail arrangement. The rotor vanes  24  may extend radially from an individual platform, or from an inner crown  25  of the rotor  12 . 
     The low-pressure compressor  4  comprises multiple stators, in this case four, each of which contains one row of stator vanes  26 . The stators are associated with the fan  16  or with a row of rotor vanes in order to redirect the flow of air so as to convert the velocity of the flow into pressure, in particular into static pressure. 
     The stator vanes  26  extend essentially radially from an outer casing  28 . They can be secured and immobilized thereon by means of attachment such as spindles  30 . They extend radially through the core flow  18 . The stator vanes may have a fixed orientation with respect to the casing  28 . Advantageously, the vanes of a single row are identical and aligned. Each row may comprise one hundred and twenty vanes ( 26 ;  24 ). 
     Inner shrouds  32  may be suspended from the inner ends of the stator vanes  26 . The inner shrouds  32  may engage in a leak-proof manner with the rotor  12  in order to improve the compression ratio of the compressor  4 . 
       FIG. 3  is a diagrammatic depiction of two vanes  26  that are representative of an annular row. 
     The row may be one of the rows presented in the context of the preceding figures. The vanes and their support, which may be the inner shroud  32 , are shown in plan view. The axis of rotation  14  is inscribed in a figurative position and provides a spatial reference. 
     Each vane  26  comprises a leading edge  34 , a trailing edge  36 , a pressure surface  38  and a suction surface  40 . These surfaces ( 38 ;  40 ) may be, respectively, concave and convex. Each of these surfaces extends from the leading edge  34  to the corresponding trailing edge  36 . The vane  26  may comprise a stack of cambered aerodynamic profiles  41 , the sides of which generate the pressure surface  38  and the suction surface  40 . At the trailing edges  36 , the contours of the profiles  41 , at the pressure surface and/or at the suction surface, are parallel and/or tangential to the axis of rotation  14  of the compressor. 
     The consecutive vanes  26  of the annular row define between them a passage  42 , which is also referred to as the between-vanes passage  42 . This passage  42  is enclosed circumferentially by the vanes  26  and delimited by the pressure and suction surfaces. The passage  42  may have a connecting surface  44  between the two consecutive vanes  26 , and may link the pressure surface  38  facing the suction surface  40  via the passage  42 . 
     The connecting surface  44  may be delimited axially by an upstream axis  46  and a downstream axis  48  which respectively connect the leading edges  34  and the trailing edges  36 . These axes ( 46 ;  48 ) may be parallel, and may in general define a parallelogram or a trapezium. The connecting surface  44  may be generally planar. 
     More precisely, the connecting surface  44  may be a portion of a tubular surface or a portion of a conical surface, in particular owing to the radius of the shroud and the optional variation in diameter of the shroud  32  along the axis of rotation  14 . It may comprise four corners  50  corresponding to the points where the edges ( 34 ;  36 ) and the support—in this case the shroud  32 , which may be an inner shroud—meet. 
     The connecting surface  44  may comprise an upstream zone  47  extending downstream from the upstream axis  46 , and a downstream zone  49  extending upstream from the downstream axis  48 . 
     The connecting surface  44  has axial asymmetry with respect to the axis of rotation  14 . It has a protuberance  52 , in particular a main protuberance  52 . This protuberance  52  may occupy the majority of the connecting surface  44 . The axial majority of the protuberance  52  may be contained within the upstream half of the row of vanes  26 . It forms a radial addition of material on the connecting surface  44 . The addition of material may be observed with regard to zones  47  and  49 . 
     The protuberance  52  also comprises a first elevation  54  having a first peak  56 , and a second elevation  58  having a second peak  60 . These elevations  54  and  58  may be the main elevations of the protuberance  52 , that is to say that they form the main volume reliefs thereof. 
     The elevations ( 54 ;  58 ) may extend over at most the axial majority of the vanes  26 . The first elevation may extend axially over 30% of the chord  62  of the first vane  26 , and/or the second elevation  58  may extend axially over 20% of the chord  62  of the second vane  26 . These elevations ( 54 ;  58 ) may be axially set back from the leading edges  34 , in particular by 10% of the axial length of a chord  62 . The first peak  56  may have a main elongation parallel to the chord  62  of the first vane  26 . 
     Along the circumference  15 , the first elevation  54  may extend over 50% of the between-vanes passage  42  and may extend from the pressure surface  38 . Its peak  56  may be spaced apart from the pressure surface  38 . A channel  64  may be formed against the first elevation  54 , between the pressure surface  38  of the first vane  26  and the first peak  56 . The second elevation  58  may extend circumferentially over 10% of the passage  42 , its peak  60  may immediately adjoin the suction surface  40  of the second vane  26 . 
     The first elevation  54  and the second elevation  58  may be at the same axial level. Their peaks ( 56 ;  60 ) may be axially aligned. The elevations ( 54 ;  58 ) may be separated from one another, and in particular circumferentially remote from one another. A col  66 , such as a mountain col, may separate them in the circumferential direction. 
     The curve noted  67  of the col  66  is the curve connecting the peaks  56 ,  60  that has the shortest length. This curve  67 , as well as all the points of the col  66  are raised above the regular radius of the inner shroud as represented by the radius RC of the zones  47  and  49 . 
     The elevations ( 54 ;  58 ) and the protuberance  52  are represented by contour lines  68 . These contour lines  68  mark variations in radial level with respect to a reference surface, in this case the connecting surface  44 . 
       FIG. 4  is a section through  FIG. 3 , as per the line IV-IV. Both the position and the inclination of the axis of rotation  14  are figurative and may vary in concrete embodiments. 
     In general, the vanes may comprise joining radii  70  at their radial ends. The joining radii  70  may surround their respective vane  26 . The connecting surface  44  may extend from the joining radii  70  so as to connect them in pairs. The radial thickness of the joining radii  70  is smaller than that of the elevations and possibly of the protuberance  52 . 
     The leading edge  34  and the trailing edge  36  of the first vane extending radially from the annular surface  33  of the inner shroud  32 . This annular surface  33  may have a constant radius RC outside the passages. The annular surface  33  may have axial symmetry. The zones  47  and  49  may extend the annular surface  33  and be axially tangential thereto. They may have arcs of constant radius RC over the circumference. 
     A first dotted line  72  extends and connects the zones  47  and  49 . A second dotted line  74  illustrates the general profile of the protuberance  52 . The radial distance between these dotted lines ( 72 ;  74 ) illustrates the additional material, that is to say the radial extension formed by the protuberance  52  on the connecting surface  44 . Similarly, the solid line  76  which is spaced apart from the second dotted line  74  illustrates the radial extension formed by the first elevation  54  on the protuberance  52 , that is to say the local thickening of the connecting surface  44 . The solid line  76  may pass through the first peak  56 . This peak may be flat. 
     The radial thickness proper of the first elevation  54  may be two times greater than the thickness proper of the protuberance  52 . These thicknesses may be maximum thicknesses. 
     With respect to the general plane  80  of the connecting surface  44 , the elevations ( 54 ;  58 ) have inclinations greater than those of the protuberance  52 . The general plane  80  may join at least one or multiple or every corner of the connecting surface  44 . Upstream and downstream, the protuberance  52  has slopes that are shallower than the adjacent slopes of the elevations. 
     The present teaching may also be applied to an outer shroud or to a casing via symmetry with respect to the axis A-A. 
       FIG. 5  is a section through  FIG. 3 , as per the line V-V. The section is perpendicular to the axis of rotation  14 , and passes through both the elevations ( 54 ;  58 ) and the protuberance  52 . 
     About the axis of rotation  14 , the connecting surface  44  is of constant radius RC. This constant radius RC may correspond to that of the first zone  47  and/or to that of the second zone  49 . At the elevations ( 54 ;  58 ), it is of variable radius RV. The first peak  56  of the first elevation  54  is arranged between the col  66  and the channel  64 . 
     The connecting surface  44  is profiled. It has a radial increase in material compared to its base, generated in particular by the zones ( 47 ;  49 ). At a given point of the axis of rotation  14  located at the level of the elevations, the radius RV of the connecting surface  44  may vary when it crosses the connecting surface  44  in the circumferential direction  15 , in particular when moving from one vane  26  to the adjacent vane, that is to say between the pressure surface  38  and the suction surface  40 . 
     Although only two vanes are shown, the present teaching may apply to all of their annular row, or to multiple vanes, or to every annular row of stator vanes of the compressor. Similarly, the connecting surface may be reproduced in identical fashion between each adjacent vane of a single row. This may form multiple annular rows of elevations ( 54 ;  58 ) that are identical, and multiple annular rows of protuberances  52  that are identical. 
     The teaching of each figure may be combined independently with the teaching of each of the other figures. The invention provides for a combination of the teaching of all of the figures and/or with a combination of the entirety of the technical solution.