Patent Publication Number: US-11649830-B2

Title: Perforated impeller blades

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to impellers, and more particularly to impellers for applications such as fuel pumps and air compressors for use in aerospace applications and the like. 
     2. Description of Related Art 
     Shrouded impellers are typically cast as a single piece or machined as two separate pieces and brazed together. Casting a shrouded impeller is often extremely difficult due to the geometry of the impeller and/or inducer vanes. These long, thin features present solidification issues during casting, which results in poor yield and high cost. Brazed shrouded impellers often have a more repeatable, shorter lead processing path, but cost significantly more and require specialized inspection techniques and processing to verify the braze joint. Both cast and brazed impellers are limited in terms of the geometry that can be produced. Molten melt solidification limits how fine a feature can be cast. Machining stresses and access restrictions can limit how fine a feature can be cut. 
     The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved systems and methods for producing impellers. This disclosure provides a solution for this need. 
     SUMMARY 
     An impeller includes a hub defining a rotational axis. A set of primary blades extends in an axial direction from the hub relative to the rotational axis. A shroud is supported by the primary blades, axially across the primary blades from the hub. The primary blades are circumferentially spaced apart from one another relative to the rotational axis. An inlet is defined between the shroud and the hub proximate a first extent of the primary blades in a radial direction relative to the rotational axis. An outlet is defined proximate a second extent of the primary blades opposite the first extent in the radial direction. A plurality of perforated blades extend axially from the hub, supporting the shroud. The perforated blades are circumferentially spaced apart from one another. Each of the perforated blades is circumferentially between each circumferentially adjacent pair of the primary blades. Each of the perforated blades has a plurality of openings therethrough. 
     Each of the perforated blades can define a perforated blade length and defines a plurality of columns spaced apart from one another along the perforated blade length. Each column can include a capital that tapers wide in a direction extending away from the respective base of the column. The capitals of the columns of the plurality of perforated blades, together with the primary blades, can support the shroud such that a ceiling surface of the shroud that is opposite from the hub across the primary blades is defined it its majority by the capitals. No portion of the ceiling surface need be locally 90° relative to the rotational axis. No portion of the ceiling surface need be locally between 80° and 90° relative to the rotational axis. Each column can branch from the respective base of the column at the hub into multiple branches supporting the shroud. Each of the multiple branches can include its own respective tapered capital. 
     There can be more perforated blades than there are primary blades, wherein multiple perforated blades are circumferentially between each circumferentially adjacent pair of the primary blades. Each of the perforated blades that is circumferentially between each circumferentially adjacent pair of the primary blades can be a splitter blade that is shorter than a flow passage between the circumferentially adjacent pair of the primary blades. 
     The inlet can open in an axial direction and is radially inward from the outlet, and the outlet can open in a radially outward direction relative to the rotational axis. The blades, hub, and shroud can be configured to drive aircraft fuel through the impeller from the inlet to the outlet. The blades, hub, and shroud can be configured to compress air passing through the impeller from the inlet to the outlet. 
     A method of making an impeller includes additively manufacturing an impeller as described above. The method includes building the impeller in a layer by layer process in a build direction along the rotational axis starting from a base of the hub. The plurality of blades includes a plurality of perforated blades that support the shroud during additively manufacturing the impeller. The method can include installing the impeller in a fuel pump, air compressor, or the like, without removing the perforated blades from the impeller. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG.  1    is a schematic cross-sectional side elevation view of an embodiment of an impeller constructed in accordance with the present disclosure, showing the hub, the shroud, and the blades; 
         FIG.  2    is a schematic perspective view of the impeller of  FIG.  1   , showing the shroud removed to view the primary blades and the perforated blades; 
         FIG.  3    is a schematic perspective view of the impeller of  FIG.  2   , showing some of the perforated blades with the shroud removed; 
         FIG.  4    is a schematic side elevation view of a portion of the impeller of  FIG.  1   , showing one of the perforated blades; and 
         FIG.  5    is a schematic outlet end view of the perforated blade of  FIG.  4   . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an embodiment of an impeller in accordance with the disclosure is shown in  FIG.  1    and is designated generally by reference character  100 . Other embodiments of systems in accordance with the disclosure, or aspects thereof, are provided in  FIGS.  2 - 5   , as will be described. The systems and methods described herein can be used to improve manufacturability, performance, and other characteristics of impellers such as used in fuel pumps, air compressors, and the like as used in aerospace applications. 
     The impeller  100  includes a hub  102  defining a rotational axis A. A set of primary blades  104  extends in an axial direction from the hub  102  relative to the rotational axis A. A shroud  106  is supported by the primary blades  104 , axially across the primary blades  104  from the hub  102 . The primary blades  104  are circumferentially spaced apart from one another relative to the rotational axis A, as shown in  FIG.  2   . An inlet  108  is defined between the shroud  106  and the hub  102  proximate a first extent or end  110  of the primary blades  104  in a radial direction relative to the rotational axis A. An outlet  112  is defined proximate a second extent or end  114  of the primary blades  104  opposite the first extent or end  110  in the radial direction. The outlet  112  is radially outward from the inlet  108 . The inlet  108  opens in an axial direction, i.e. generally aligned with the rotational axis A. The outlet  112  opens in a radially outward direction relative to the rotational axis A. The blades  104 , hub  102 , and shroud  106  are configured to drive aircraft fuel through the impeller  100  from the inlet  108  to the outlet  112 . It is also contemplated that the blades  104 , hub  102 , and shroud  106  can instead be configured to compress air passing through the impeller  100  from the inlet  108  to the outlet  112 . The impeller  100  can also be configured for any other suitable application. 
     With reference now to  FIG.  2   , a plurality of perforated blades  116  extend axially from the hub  102 , supporting the shroud  106  (which is not shown in  FIG.  2   , but see  FIG.  1   ). The perforated blades  116  are circumferentially spaced apart from one another. Each of the perforated blades  116  is circumferentially spaced apart between each circumferentially adjacent pair of the primary blades  104 . There are more perforated blades  116  than there are primary blades  104 , so multiple perforated blades  116  are circumferentially spaced apart between each circumferentially adjacent pair of the primary blades  104 , as shown in  FIG.  3   . As shown in  FIG.  2   , each of the perforated blades  116  is a splitter blade that is shorter in its length L 1 , L 2 , L 3  in the flow direction through the impeller  100  than the flow passage between the circumferentially adjacent pair of the primary blades  104  on either side of the respective perforated blade  116 . In other words, the perforated blades  116  are shorter than the primary blades  104 . There are three respective perforated blades  116  between each circumferentially adjacent pair of primary blades  104 , however those skilled in the art will readily appreciate that any suitable number one or more can be used instead of three. Moreover, while the perforated blades  116  are all shown as splitter blades that are shorter than the primary blades  104 , the perforated blades  116  can be as long as the primary blades or longer if suitable for a given application. 
     With reference now to  FIG.  4   , each of the perforated blades  116  has a plurality of fenestrations or openings  118  therethrough. By way of contrast, the primary blades  104  (shown in  FIGS.  1 - 3   ) are solid or non-perforated as they lack openings or fenestrations  118 . Each of the perforated blades  116  defines a perforated blade length L 3  (or L 2  or L 1  as labeled in  FIG.  2   ) and defines a plurality of columns  120  spaced apart from one another along the perforated blade length L 3 . Each column  120  includes a capital  126  that tapers wide in a direction extending away from the respective base  124  of the column  120 . The base  124  of each column  120  supports the column  120  upon the hub  102  (which is labeled in  FIGS.  1 - 3   ). The capitals  126  of the columns  120 , together with the primary blades  104  (labeled in  FIGS.  1 - 3   ), support the shroud  106  (labeled in  FIG.  1   ). A ceiling surface  128  of the shroud  106  that is opposite from the hub  102  across the primary blades  104  is defined it its majority by the capitals  126 .  FIG.  5    shows the tapered shape of the capitals  126  from another angle. As shown in  FIGS.  4  and  5   , each column  120  branches from the respective base  120  at the hub into multiple branches  130  supporting the shroud  106  (labeled in  FIG.  1   ). Each of the multiple branches  130  includes its own respective tapered capital  126 . 
     As shown in  FIG.  4   , due to the capitals  126 , no portion of the ceiling surface  128  need be locally 90° relative to the rotational axis A, as indicated by the angles labeled in  FIG.  4   . No portion of the ceiling surface  128  need be locally between 80° and 90° relative to the rotational axis A. There are small exceptions possible, where the machine performing a build can tolerate small unsupported ceiling portions at around 80°-90° relative to the rotational axis A. 
     Even though portions of the shroud  106  can be 90° from the rotational axis A in the cross section of the shroud  106 , e.g. through the centerline of that cross-section following the line of the ceiling surface  128  as it is schematically depicted in  FIG.  4   , the shroud  106  is supported laterally by the neighboring supports (columns  120  and capitals  126 ) the overhangs of which can be at an angle of 45° for example. 
     There are some very small unsupported overhangs, e.g. 80°-90°, which are allowable, e.g. at the very tip of an archway (openings  118 ) between two pairs of adjacent blade capitols  126 . There can be a radius put in the ceiling surface  128  where the radius becomes tangent to the horizontal and this causes it to be 90 degrees from the build direction B of  FIG.  1   . In cases where it is a very small distance, the build will have enough support from the closest neighbors to still allow it to build properly. 
     With reference again to  FIG.  1   , a method of making an impeller includes additively manufacturing an impeller such as the impeller  100  described above. The method includes building the impeller  100  in a layer by layer process, schematically indicated by the gradations  132  in  FIG.  1   , depositing the layers  132  one after another in the build direction B along or parallel to the rotational axis A starting from a base  134  of the hub  102  and ending at the top  136  of the impeller  100  as oriented in  FIG.  1   . The plurality of blades includes a plurality of perforated blades, e.g. perforated blades  116  labeled in  FIG.  2   , and primary blades  104 . Both types of blades  104 ,  116  support the shroud, e.g. shroud  106 , during additively manufacturing the impeller  100 . 
     While the perforate blades  116  serve as support structures during additive manufacture of the impeller, the method can include installing the impeller in a fuel pump, air compressor, or the like, e.g. on an aircraft, without removing the perforated blades  116  from the impeller  100 . The pump, compressor, or the like is represented schematically in  FIG.  1    by the box  138 . The perforated blades  116  are a functional element of the finished product of the impeller  100 . 
     The perforated blade as disclosed herein allows for using the additive manufacturing techniques in producing centrifugal pump impellers and the like, while maintaining the same hydraulic performance of a standard design in which there are only solid impeller blades. In terms of function, the use of the perforated blades can be beneficial, e.g. to pump stability at high turn down flows by the increase in the boundary layer viscous drag effects. While branching columns  120  are shown and described herein, any suitable perforated or fenestrated blade geometry can be used without departing from the scope of this disclosure. Beneficial structures can reduce a full solid blade to a grid or lattice of supporting structures that allow supporting the roof surfaces in the additive manufacturing process, but can be designed to introduce little to no pressure loading, or work, to the operating fluid. 
     The perforated blades  116  act as a support structure for the impeller shroud surfaces that face downward relative to gravity during the additive manufacturing process. The perforated blades can create a more robust fluid boundary layer, thereby reducing boundary layer separation at lower flow rates and improving impeller flow stability. The perforated blades can also reduce overall weight of the impeller. The perforated blades can allow for the baseline impeller blade configuration to be maintained, thereby reducing design re-work when utilizing techniques disclosed herein. 
     The methods and systems of the present disclosure, as described above and shown in the drawings, provide for improved manufacturability, performance, and other characteristics of impellers such as used in fuel pumps, air compressors, and the like as used in aerospace applications. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.