Patent Description:
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.

<CIT> relates to an impeller with perforated blades; <CIT> relates to an impeller manufactured using an additive manufacturing production method.

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 defines 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 <NUM>° relative to the rotational axis. No portion of the ceiling surface need be locally between <NUM>° and <NUM>° 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.

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> and is designated generally by reference character <NUM>. Other embodiments of systems in accordance with the disclosure, or aspects thereof, are provided in <FIG>, 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 <NUM> includes a hub <NUM> defining a rotational axis A. A set of primary blades <NUM> extends in an axial direction from the hub <NUM> relative to the rotational axis A. A shroud <NUM> is supported by the primary blades <NUM>, axially across the primary blades <NUM> from the hub <NUM>. The primary blades <NUM> are circumferentially spaced apart from one another relative to the rotational axis A, as shown in <FIG>. An inlet <NUM> is defined between the shroud <NUM> and the hub <NUM> proximate a first extent or end <NUM> of the primary blades <NUM> in a radial direction relative to the rotational axis A. An outlet <NUM> is defined proximate a second extent or end <NUM> of the primary blades <NUM> opposite the first extent or end <NUM> in the radial direction. The outlet <NUM> is radially outward from the inlet <NUM>. The inlet <NUM> opens in an axial direction, i.e. generally aligned with the rotational axis A. The outlet <NUM> opens in a radially outward direction relative to the rotational axis A. The blades <NUM>, hub <NUM>, and shroud <NUM> are configured to drive aircraft fuel through the impeller <NUM> from the inlet <NUM> to the outlet <NUM>. It is also contemplated that the blades <NUM>, hub <NUM>, and shroud <NUM> can instead be configured to compress air passing through the impeller <NUM> from the inlet <NUM> to the outlet <NUM>. The impeller <NUM> can also be configured for any other suitable application.

With reference now to <FIG>, a plurality of perforated blades <NUM> extend axially from the hub <NUM>, supporting the shroud <NUM> (which is not shown in <FIG>, but see <FIG>). The perforated blades <NUM> are circumferentially spaced apart from one another. Each of the perforated blades <NUM> is circumferentially spaced apart between each circumferentially adjacent pair of the primary blades <NUM>. There are more perforated blades <NUM> than there are primary blades <NUM>, so multiple perforated blades <NUM> are circumferentially spaced apart between each circumferentially adjacent pair of the primary blades <NUM>, as shown in <FIG>. As shown in <FIG>, each of the perforated blades <NUM> is a splitter blade that is shorter in its length L1, L2, L3 in the flow direction through the impeller <NUM> than the flow passage between the circumferentially adjacent pair of the primary blades <NUM> on either side of the respective perforated blade <NUM>. In other words, the perforated blades <NUM> are shorter than the primary blades <NUM>. There are three respective perforated blades <NUM> between each circumferentially adjacent pair of primary blades <NUM>, 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 <NUM> are all shown as splitter blades that are shorter than the primary blades <NUM>, the perforated blades <NUM> can be as long as the primary blades or longer if suitable for a given application.

With reference now to <FIG>, each of the perforated blades <NUM> has a plurality of fenestrations or openings <NUM> therethrough. By way of contrast, the primary blades <NUM> (shown in <FIG>) are solid or non-perforated as they lack openings or fenestrations <NUM>. Each of the perforated blades <NUM> defines a perforated blade length L3 (or L2 or L1 as labeled in <FIG>) and defines a plurality of columns <NUM> spaced apart from one another along the perforated blade length L3. Each column <NUM> includes a capital <NUM> that tapers wide in a direction extending away from the respective base <NUM> of the column <NUM>. The base <NUM> of each column <NUM> supports the column <NUM> upon the hub <NUM> (which is labeled in <FIG>). The capitals <NUM> of the columns <NUM>, together with the primary blades <NUM> (labeled in <FIG>), support the shroud <NUM> (labeled in <FIG>). A ceiling surface <NUM> of the shroud <NUM> that is opposite from the hub <NUM> across the primary blades <NUM> is defined it its majority by the capitals <NUM>. <FIG> shows the tapered shape of the capitals <NUM> from another angle. As shown in <FIG>, each column <NUM> branches from the respective base <NUM> at the hub into multiple branches <NUM> supporting the shroud <NUM> (labeled in <FIG>). Each of the multiple branches <NUM> includes its own respective tapered capital <NUM>.

As shown in <FIG>, due to the capitals <NUM>, no portion of the ceiling surface <NUM> need be locally <NUM>° relative to the rotational axis A, as indicated by the angles labeled in <FIG>. No portion of the ceiling surface <NUM> need be locally between <NUM>° and <NUM>° 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 <NUM>°-<NUM>° relative to the rotational axis A.

Even though portions of the shroud <NUM> can be <NUM>° from the rotational axis A in the cross section of the shroud <NUM>, e.g. through the centerline of that cross-section following the line of the ceiling surface <NUM> as it is schematically depicted in <FIG>, the shroud <NUM> is supported laterally by the neighboring supports (columns <NUM> and capitals <NUM>) the overhangs of which can be at an angle of <NUM>° for example.

There are some very small unsupported overhangs, e.g. <NUM>°-<NUM>°, which are allowable, e.g. at the very tip of an archway (openings <NUM>) between two pairs of adjacent blade capitols <NUM>. There can be a radius put in the ceiling surface <NUM> where the radius becomes tangent to the horizontal and this causes it to be <NUM> degrees from the build direction B of <FIG>. 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>, a method of making an impeller includes additively manufacturing an impeller such as the impeller <NUM> described above. The method includes building the impeller <NUM> in a layer by layer process, schematically indicated by the gradations <NUM> in <FIG>, depositing the layers <NUM> one after another in the build direction B along or parallel to the rotational axis A starting from a base <NUM> of the hub <NUM> and ending at the top <NUM> of the impeller <NUM> as oriented in <FIG>. The plurality of blades includes a plurality of perforated blades, e.g. perforated blades <NUM> labeled in <FIG>, and primary blades <NUM>. Both types of blades <NUM>, <NUM> support the shroud, e.g. shroud <NUM>, during additively manufacturing the impeller <NUM>.

While the perforate blades <NUM> 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 <NUM> from the impeller <NUM>. The pump, compressor, or the like is represented schematically in <FIG> by the box <NUM>. The perforated blades <NUM> are a functional element of the finished product of the impeller <NUM>.

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 <NUM> 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 <NUM> 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.

Claim 1:
An impeller (<NUM>) comprising:
a hub (<NUM>) defining a rotational axis;
a set of primary blades (<NUM>) extending in an axial direction from the hub (<NUM>) relative to the rotational axis;
a shroud (<NUM>) supported by the primary blades (<NUM>), axially across the primary blades (<NUM>) from the hub (<NUM>), wherein the primary blades (<NUM>) are circumferentially spaced apart from one another relative to the rotational axis, wherein an inlet (<NUM>) is defined between the shroud (<NUM>) and the hub (<NUM>) proximate a first extent of the primary blades (<NUM>) in a radial direction relative to the rotational axis, and an outlet (<NUM>) is defined proximate a second extent of the primary blades (<NUM>) opposite the first extent in the radial direction; characterised by
a plurality of perforated blades (<NUM>) extending axially from the hub (<NUM>) and supporting the shroud (<NUM>), wherein the perforated blades are circumferentially spaced apart from one another, and wherein each of the perforated blades is circumferentially between each circumferentially adjacent pair of the primary blades (<NUM>), wherein each of the perforated blades has a plurality of openings (<NUM>) therethrough; and wherein each of the perforated blades defines a perforated blade length and defines a plurality of columns (<NUM>) spaced apart from one another along the perforated blade length.