INTAKE GRATE FOR UNDERWATER VEHICLE VECTOR-FLOW THRUSTER

Abstract

A propulsion system is provided. The propulsion system includes a housing and a rotatable vector-flow nozzle that extends from the housing and is configured to eject a fluid in a plurality of directions. The propulsion system also has a propeller disposed within the housing and in fluid communication with the rotatable vector-flow nozzle. The propeller includes a blade that pitches in a first direction. A fluid intake is located at an end of the propulsion system housing and opposite the rotatable vector-flow nozzle. The propulsion system also has an intake grate at the fluid intake where the intake grate defines a hub and a rim spaced apart and about the hub. The intake grate includes a plurality of intake grate blades that pitch in a second direction opposite the first direction.

Claims

1. A marine propulsion system comprising: a housing; a rotatable vector-flow nozzle extending from the housing and configured to eject a fluid in a plurality of directions; a propeller disposed within the housing and in fluid communication with the rotatable vector-flow nozzle, the propeller having a blade that pitches in a first direction; a fluid intake disposed at an end of the housing and opposite the rotatable vector-flow nozzle; and an intake grate disposed at the fluid intake, the intake grate having an asymmetrical configuration defining a hub and a rim spaced apart and about the hub, the intake grate comprising: a first plurality of intake grate blades wherein: blades of the first plurality of intake grate blades pitch in a second direction that is opposite the first direction; and the blades of the first plurality of intake grate blades have a hub intake grate angle and a first intake grate rim angle; a second plurality of intake grate blades wherein: blades of the second plurality of intake grate blades pitch in the second direction; and the blades of the second plurality of intake grate blades have the hub intake grate angle and a second intake grate rim angle that is different from the first intake grate rim angle.

2. The marine propulsion system of claim 1, wherein the blades of the first plurality of intake grate blades have a first length and the blades of the second plurality of intake grate blades have a second length that is different from the first length.

3. The marine propulsion system of claim 1, wherein the rotatable vector-flow nozzle has a rotatable span of 360 degrees relative to the housing and the marine propulsion system is configurable to produce thrust via the rotatable vector-flow nozzle that varies in a range between one percent and ten percent throughout the rotatable span.

4. The marine propulsion system of claim 1, wherein the fluid intake includes a first taper disposed about a periphery of the fluid intake.

5. The marine propulsion system of claim 4, wherein the blades of the first plurality of intake grate blades have a second taper at a distal end, the second taper mirroring the first taper.

6. The marine propulsion system of claim 1, wherein the hub intake grate angle is in a range between one degree and thirty degrees.

7. The marine propulsion system of claim 6, wherein the first intake grate rim angle is in a range between thirty degrees and sixty degrees.

8. The marine propulsion system of claim 6, wherein the second intake grate rim angle is in a range between thirty degrees and sixty degrees.

9. The marine propulsion system of claim 1, wherein the intake grate is in a shape of an oval or a polygon.

10. A marine propulsion system comprising: a housing; a rotatable vector-flow nozzle extending from the housing and configured to eject a fluid in a plurality of directions; a propeller disposed within the housing and in fluid communication with the rotatable vector-flow nozzle, the propeller having a blade that pitches in a first direction; a fluid intake disposed at an end of the housing and opposite the rotatable vector-flow nozzle; and an intake grate disposed at the fluid intake, the intake grate defining a hub and a rim spaced apart and about the hub, the intake grate comprising a plurality of intake grate blades wherein the plurality of intake grate blades: pitch in a second direction that is opposite the first direction; and have a hub intake grate angle at the intake grate hub and a rim intake grate angle at the intake grate rim, the hub intake grate angle being different from the rim intake grate angle.

11. The marine propulsion system of claim 10, wherein the intake grate has an asymmetrical configuration and the plurality of intake grate blades includes a first plurality of intake grate blades having a first length and a second plurality of intake grate blades having a second length less than the first length.

12. The marine propulsion system of claim 11, wherein the first plurality of intake grate blades has a first rim intake grate angle and the second plurality of intake grate blades have a second rim intake grate angle that is less than the first rim intake grate angle.

13. The marine propulsion system of claim 10, wherein the rotatable vector-flow nozzle has a rotatable span of 360 degrees relative to the housing and the marine propulsion system is configurable to produce thrust via the rotatable vector-flow nozzle that varies in a range between one percent and ten percent throughout the rotatable span.

14. The marine propulsion system of claim 10, wherein the hub intake grate angle is in a range between one degree and thirty degrees.

15. The marine propulsion system of claim 14, wherein the rim intake grate angle is in a range between thirty degrees and sixty degrees.

16. A marine propulsion system comprising: a housing; a rotatable vector-flow nozzle extending from the housing and configured to eject a fluid in a plurality of directions; a propeller disposed within the housing and in fluid communication with the rotatable vector-flow nozzle, the propeller having a blade that pitches in a first direction; a fluid intake disposed at an end of the housing and opposite the rotatable vector-flow nozzle; and an intake grate disposed at the fluid intake, the intake grate defining a hub and a rim spaced apart and about the hub, the intake grate comprising a plurality of intake grate blades, wherein the plurality of intake grate blades pitch in a second direction that is opposite the first direction.

17. The marine propulsion system of claim of claim 16, wherein the plurality of intake grate blades has a hub intake grate angle at the intake grate hub and a rim intake grate angle at the intake grate rim, the hub intake grate angle being less than the rim intake grate angle.

18. The marine propulsion system of claim 16, wherein the rotatable vector-flow nozzle has a rotatable span of 360 degrees relative to the housing and the marine propulsion system is configurable to produce thrust via the rotatable vector-flow nozzle that varies in a range between one percent and ten percent throughout the rotatable span.

19. The marine propulsion system of claim 16, wherein the intake grate has an asymmetrical configuration and the plurality of intake grate blades includes a first plurality of intake grate blades having a first length and a second plurality of intake grate blades having a second length less than the first length.

20. The marine propulsion system of claim 19, wherein the first plurality of intake grate blades has a first rim intake grate angle and the second plurality of intake grate blades have a second rim intake grate angle that is less than the first rim intake grate angle.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0004] FIG. 1 illustrates, by way of example, a propulsion system.

[0005] FIG. 2 shows an intake grate of the propulsion system of FIG. 1.

[0006] FIG. 3 shows a propeller and a propeller blade of the propulsion system of FIG. 1.

[0007] FIG. 4 is a diagram comparing a pitch of intake grate blades of the intake grate of FIG. 2 with a pitch of the propeller blade of propeller of FIG. 3.

[0008] FIG. 5 shows an intake grate hub angle of intake grate blades of the intake grate of FIG. 2.

[0009] FIGS. 6A and 6B show intake grate rim angles of intake grate blades of the intake grate of FIG. 2.

[0010] FIG. 7 shows an intake grate of the propulsion system of FIG. 1.

[0011] FIGS. 8 and 9 illustrate a comparison of thrust output between a propulsion system having an intake grate with blades that pitch in the same direction as blades of a propeller and thrust output between a propulsion system having an intake grate with blades that pitch in a direction that is opposite to blades of a propeller.

[0012] FIG. 10 shows a propulsion system where an intake grate has clocked configuration.

DETAILED DESCRIPTION

[0013] The following description and the drawings sufficiently illustrate teachings to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some examples may be included in, or substituted for, those of other examples. Teachings set forth in the claims encompass all available equivalents of those claims.

[0014] Examples relate to an intake grate for a propulsion system having a propeller and a rotatable vector-flow nozzle. The intake grate can have a plurality of angled intake grate blades extending from a hub of the intake grate towards a rim of the intake grate. Each of the intake grate blades can have a pitch in a first direction. The propeller can include blades and function to draw fluid into the propulsion system via the intake grate. The propeller blades can have a pitch that is opposite to the pitch of the intake grate blades. The propeller blades can have a pitch in a second direction that is opposite to the first direction. The rotatable vector-flow nozzle can function to eject a high-pressure stream of fluid. By virtue of the intake grate blades having a pitch that is opposite a pitch of the propeller, an amount of fluid ejected from the rotatable vector-flow nozzle that can be drawn into the propulsion system by the propeller is minimized.

[0015] The pitch angle of the intake grate blades can increase or decrease as the intake grate blades extend from the intake grate hub towards the intake grate rim. A pitch angle can be a twist angle of the blade relative to the horizontal plane normal to the axis of the hub. Thus, a pitch angle of the intake grate blade can a twist angle of the intake grate blade relative to a hub of the intake grate while a pitch angle of the propeller can be a twist angle of the blade relative to a hub of the propeller.

[0016] The pitch angle of the intake grate blades at the intake grate hub can vary in comparison to such as being less than an angle of the intake grate blades at the intake grate rim. If the intake grate is symmetrical where the intake grate blades each have the same length, each of the intake grate blades can have the same hub intake grate rim angle and the same intake grate rim angle such that the intake grate rim angle among different intake grate blades does not change and instead remains the same. A length of the intake grate blades can vary based on a shape of the intake grate such that rim intake grate blade angles can vary among groups of the intake grate blades. For example, if the intake grate is asymmetrical, the first group of intake grate blades can have a first length while a second group of intake grate blades can have a second length that is different from the first length. Since the pitch can vary according to length, the first group of intake grate blades can have an intake grate rim angle that is different from an intake grate rim angle of the second group of intake grate blades. Furthermore, the first and second groups of the intake grate blades can have the same hub intake grate angle.

[0017] Now referring to FIG. 1, a propulsion system 100 that can be used for a vehicle, such as a vehicle having marine applications, is shown. The propulsion system 100 can include an intake grate 102 at a fluid intake 104 of the propulsion system 100. The intake grate 102 along with the fluid intake 104 can be disposed at an end 106 of a housing 108 of the propulsion system 100.

[0018] Fluid F can be drawn into the propulsion system 100 via a propeller 110 of the propulsion system 100. The propeller 110 can be powered by a motor 112 and draw the fluid F into chambers 114 defined by the propulsion system housing 108. The propeller motor 112 can rotate the propeller 110 in either a clockwise or counterclockwise direction. As the propeller 110 rotates, a pressure differential within the propulsion system chamber 114 and an area outside of the propulsion system 100 is created. The pressure differential can draw the fluid F into the propulsion system chamber 114.

[0019] The propulsion system 100 can also have a vector-flow nozzle 116 extending from the propulsion system housing 108 and opposite the fluid intake 104 at the propulsion system housing 108. The vector-flow nozzle 116 can provide thrust for a vehicle that uses the propulsion system 100. The vector-flow nozzle 116 can be in fluid communication with the propeller 110. The vector-flow nozzle 116 can be coupled to a vector-flow nozzle motor 118 that can rotate the vector-flow nozzle 116 along direction Z in a rotatable span of 360 degrees relative to the propulsion system 100.

[0020] The vector-flow nozzle 116 can provide thrust to a vehicle that uses the propulsion system 100 in directions throughout the rotatable span of 360 degrees relative to the propulsion system 100. As the propeller 110 draws the fluid F into the propulsion system chamber 110, by virtue of the rotation of the propeller 110 and the propeller 110 being in fluid communication with the vector-flow nozzle 116, the propeller 110 can force the fluid F into the vector-flow nozzle 116. The vector-flow nozzle 116 can then eject pressurized thrust fluid TF, which can provide thrust for a vehicle that uses the propulsion system 100. Since the vector-flow nozzle 116 can rotate 360 degrees relative to the propulsion system 100, the vector-flow nozzle 116 is capable of ejecting the thrust fluid TF in a plurality of directions.

[0021] As can be seen with reference to FIG. 1, in some configurations, the thrust fluid TP can flow over the intake grate 102. Moreover, the propeller 110 can be rotating and draw the fluid F into the intake grate 102 and the propulsion system chamber 110. However, the intake grate 102 can be configured to minimize the amount of the thrust fluid TP that is drawn into the intake grate 102 and the propulsion system chamber 110.

[0022] Both the intake grate 102 and the propeller 110 can have blades. For example, the intake grate 102 can include intake grate blades 200 and 202 while the propeller 110 can include a blade 300. The propeller blade 300 can define a propeller blade pitch 400 and the intake grate blades 200 and 202 can define an intake grate blade pitch 402. As can be seen with reference to FIG. 4, the propeller blade pitch 400 can be in a first direction while the intake grate blade pitch 402 can be in a second direction that is opposite to the first direction. To further illustrate, the propeller blade pitch 400 can extend in a positive direction along an X-axis while the intake grate blade pitch 402 can extend in a negative direction along the X-axis.

[0023] Returning attention to FIG. 2, the intake grate 102 can also include an intake grate hub 204 that is spaced apart from an intake grate rim 206. The intake grate rim 206 can be disposed about the intake grate hub 204, as shown with reference to FIG. 2. The intake grate blades 200 and 202 can extend from the intake grate hub 204 toward and to the intake grate rim 206. The intake grate blades 200 and 202 can be disposed at an intake grate hub angle 500 relative to the intake grate hub 204. In examples, the hub intake grate hub angle 500 can be in a range of about 1 to about 30.

[0024] For purposes of explanation, the propeller blade pitch 400 can be defined as the propeller blade 300 extending from a point 404 along a Y-axis to a propeller blade point 406 along the X-axis. The propeller blade point 406 can be along a positive position of the X-axis relative to an intersection of the X-axis with the Y-axis defined by a point 408. In an example, the point 404 can correspond to the intake grate hub 202. Moreover, the point 404 can correspond to an outer point 302 (FIG. 3) of the propeller 300.

[0025] The intake grate blade pitch 402 can be defined as the intake grate blades 200 and 202 extending from the point 404 to an intake grate blade point 410 along the X-axis. The intake grate blade point 410 can be along a negative position of the X-axis relative the point 408. As can be seen with reference to FIG. 4, the propeller blade pitch 400 and the intake grate blade pitch 402 are opposite to each other.

[0026] In addition, each of the intake grate blades 200 and 202 can contact the intake grate rim 206 at an intake grate rim angle. The intake grate blade 200 can contact the intake grate rim 206 at an intake grate rim angle 600 (FIG. 6A). Moreover, the intake grate blade 202 can contact the intake grate rim 206 at an intake grate rim angle 602 (FIG. 6B).

[0027] As discussed above, each of the intake grate blades 200 and 202 can have the intake grate blade pitch 402. The intake grate blade pitch 402 can correlate to the intake grate hub angle 500 and/or the intake grate rim angles 600 and 602 where the angles 500, 600, and 602 can have a linear relationship with a distance between the point 408 and the intake grate blade point 410. Thus, the greater value of the angles 500, 600, and 602 the greater the distance between the point 408 and the intake grate blade point 410.

[0028] In examples, the intake grate blade pitch 402 can vary along a length of the intake grate blades where the intake grate blade pitch 402 can increase as a length of the intake grate blade increases. Thus, the intake grate blade pitch 402 can have a value at the intake grate hub 204 that correlates with the intake grate hub angle 500. In addition, the intake grate blade pitch 402 can have a value at the intake grate rim 206 that correlates with the intake grate rim angle 600 or the intake grate rim angle 602, which can be different from the intake grate hub angle 500. The intake grate rim angle value can be greater than the intake grate hub angle value, which can correlate to the intake grate rim angles 600 and 602 being greater than the intake grate hub angle 500.

[0029] The intake grate 102 can have an asymmetrical configuration, such as an oval, where the intake grate blade 200 has a length 208 that is different from a length 210 of the intake grate blade 202. The intake grate blade length 208 can be longer or shorter than the intake grate blade length 210. In FIG. 2, the intake grate blade length 208 is larger than the intake grate blade length 210. Moreover, the intake grate 102 can have any standard polygon shape or non-standard polygon shape. Here, since the intake grate blade length 208 is larger than the intake grate blade length 210 and the intake grate blade pitch 402 can vary, such as in a linear fashion and here, as a function of a length, the intake grate rim angle 600 can be larger than the intake grate rim angle 602. In examples, the intake grate rim angle 600 and the intake grate rim angle 602 can be in a range between about 30 and about 60. When the intake grate rim angle 600 differs from the intake grate rim angle 602, the intake grate rim angle 600 can be a first value within the range of about 30 and about 60 while the intake grate rim angle 600 can be a second value within the range of about 30 and about 60 that is different from the first value.

[0030] The intake grate blades can also have a taper 212 that can complement a shape of the fluid intake 104. More specifically, in examples where the intake grate 102 has an asymmetrical configuration and the fluid intake 104 also has an asymmetrical configuration, the fluid intake 104 can include a wall 700 having an angled configuration that defines a taper. To allow fitment of the intake grate 102 onto the fluid intake 104, the intake grate blades 200/202 can have the intake grate blade taper 212 that can mirror the fluid intake wall 700.

[0031] As noted above, by virtue of the intake grate blades 200/202 having a pitch that is opposite to a pitch of the propeller blade 300, the intake of the thrust fluid TF by the intake grate 104 is minimized. An amount of intake of the thrust fluid TF by the intake grate 102 can reduce the amount of thrust provided by the propulsion system 100. The amount of thrust provided by the propulsion system 100 can be characterized as thrust output.

[0032] Now referring to FIGS. 8 and 9, a comparison of thrust output between a propulsion system having an intake grate with blades that pitch in the same direction as blades of a propeller (FIG. 8) and thrust output between a propulsion system having an intake grate with blades that pitch in a direction that is opposite to blades of a propeller (FIG. 9) is shown.

[0033] FIG. 8 illustrates examples where intake grate blades and propeller blades have a pitch that is in the same direction. In FIG. 8, the vector-flow nozzle 116 can have a rotatable span 800 that corresponds to a rotation of 360 relative to the propulsion system housing 108. In FIG. 8, 60 can correspond to a configuration where the vector-flow nozzle 116 ejects the thrust fluid TF in a direction that is opposite from an intake grate of a propulsion system. Moreover, 240 can correspond to a configuration where the vector-flow nozzle 116 ejects the thrust fluid TF in a direction such that the thrust fluid TF flows over an intake grate of a propulsion system. As can be seen with reference to FIG. 8, in examples where the intake grate blades and propeller blades have a pitch that is in the same direction, thrust generated by a vector-flow nozzle drops of considerably at 240 in comparison to 60. Moreover, thrust generated by the vector-flow nozzle drops off significantly in a range between 150 and 330.

[0034] FIG. 9 illustrates examples where the intake grate blades 200/202 have the intake grate blade pitch 402 and the propeller blade 300 has the propeller blade pitch 400. Due to the opposing pitches of the intake grate blades 200/202 and the propeller blade 300, thrust generated by the vector-flow nozzle 116 can vary in a range between about one percent and about ten percent.

[0035] In some examples, the intake grate 102 can have a clocked configuration relative to the propulsion system housing 108, as shown with reference to FIG. 10. In the examples discussed above, the intake grate 102 can have a configuration where ones of the intake grate blades, such as the intake grate blades 200, are in line with a center Z of the propulsion system housing 108. In further examples, the intake grate 102 along with the fluid intake 104 can have a clocked configuration relative to the propulsion system housing 108. In particular, ones of the intake grate blades of the intake grate 102, such as the intake grate blades 200, can be rotated an angle 1000 relative to the propulsion system housing 108. By clocking the blades with an blade advance or blade retard clocking angle, the in-line blade can be shifted from one side to another side. This can cause an asymmetrical thrust output response when plotting FIG. 9. Additionally, while a singular blade pitch profile are discussed herein, multiple blades profiles for the intake grate blades and/or the propeller blade could be user. Moreover, clocking can optimize drag and thruster efficiency.

ADDITIONAL EXAMPLES

[0036] Example 1 is a marine propulsion system comprising: a housing; a rotatable vector-flow nozzle extending from the housing and configured to eject a fluid in a plurality of directions; a propeller disposed within the housing and in fluid communication with the rotatable vector-flow nozzle, the propeller having a blade that pitches in a first direction; a fluid intake disposed at an end of the housing and opposite the rotatable vector-flow nozzle; and an intake grate disposed at the fluid intake, the intake grate having an asymmetrical configuration defining a hub and a rim spaced apart and about the hub, the intake grate comprising: a first plurality of intake grate blades wherein: blades of the first plurality of intake grate blades pitch in a second direction that is opposite the first direction; and the blades of the first plurality of intake grate blades have a hub intake grate angle and a first intake grate rim angle; a second plurality of intake grate blades wherein: blades of the second plurality of intake grate blades pitch in the second direction; and the blades of the second plurality of intake grate blades have the hub intake grate angle and a second intake grate rim angle that is different from the first intake grate rim angle.

[0037] In Example 2, the subject matter of Example 1 includes, wherein the blades of the first plurality of intake grate blades have a first length and the blades of the second plurality of intake grate blades have a second length that is different from the first length.

[0038] In Example 3, the subject matter of Examples 1-2 includes, degrees relative to the housing and the marine propulsion system is configurable to produce thrust via the rotatable vector-flow nozzle that varies in a range between one percent and ten percent throughout the rotatable span.

[0039] In Example 4, the subject matter of Examples 1-3 includes, wherein the fluid intake includes a first taper disposed about a periphery of the fluid intake.

[0040] In Example 5, the subject matter of Example 4 includes, wherein the blades of the first plurality of intake grate blades have a second taper at a distal end, the second taper mirroring the first taper.

[0041] In Example 6, the subject matter of Examples 1-5 includes, wherein the hub intake grate angle is in a range between one degree and thirty degrees.

[0042] In Example 7, the subject matter of Example 6 includes, wherein the first intake grate rim angle is in a range between thirty degrees and sixty degrees.

[0043] In Example 8, the subject matter of Examples 6-7 includes, wherein the second intake grate rim angle is in a range between thirty degrees and sixty degrees.

[0044] In Example 9, the subject matter of Examples 1-8 includes, wherein the intake grate is in a shape of an oval or a polygon.

[0045] Example 10 is a marine propulsion system comprising: a housing; a rotatable vector-flow nozzle extending from the housing and configured to eject a fluid in a plurality of directions; a propeller disposed within the housing and in fluid communication with the rotatable vector-flow nozzle, the propeller having a blade that pitches in a first direction; a fluid intake disposed at an end of the housing and opposite the rotatable vector-flow nozzle; and an intake grate disposed at the fluid intake, the intake grate defining a hub and a rim spaced apart and about the hub, the intake grate comprising a plurality of intake grate blades wherein the plurality of intake grate blades: pitch in a second direction that is opposite the first direction; and have a hub intake grate angle at the intake grate hub and a rim intake grate angle at the intake grate rim, the hub intake grate angle being different from the rim intake grate angle.

[0046] In Example 11, the subject matter of Example 10 includes, wherein the intake grate has an asymmetrical configuration and the plurality of intake grate blades includes a first plurality of intake grate blades having a first length and a second plurality of intake grate blades having a second length less than the first length.

[0047] In Example 12, the subject matter of Example 11 includes, wherein the first plurality of intake grate blades has a first rim intake grate angle and the second plurality of intake grate blades have a second rim intake grate angle that is less than the first rim intake grate angle.

[0048] In Example 13, the subject matter of Examples 10-12 includes, degrees relative to the housing and the marine propulsion system is configurable to produce thrust via the rotatable vector-flow nozzle that varies in a range between one percent and ten percent throughout the rotatable span.

[0049] In Example 14, the subject matter of Examples 10-13 includes, wherein the hub intake grate angle is in a range between one degree and thirty degrees.

[0050] In Example 15, the subject matter of Example 14 includes, wherein the rim intake grate angle is in a range between thirty degrees and sixty degrees.

[0051] Example 16 is a marine propulsion system comprising: a housing; a rotatable vector-flow nozzle extending from the housing and configured to eject a fluid in a plurality of directions; a propeller disposed within the housing and in fluid communication with the rotatable vector-flow nozzle, the propeller having a blade that pitches in a first direction; a fluid intake disposed at an end of the housing and opposite the rotatable vector-flow nozzle; and an intake grate disposed at the fluid intake, the intake grate defining a hub and a rim spaced apart and about the hub, the intake grate comprising a plurality of intake grate blades, wherein the plurality of intake grate blades pitch in a second direction that is opposite the first direction.

[0052] In Example 17, the subject matter of Example 16 includes, wherein the plurality of intake grate blades have a hub intake grate angle at the intake grate hub and a rim intake grate angle at the intake grate rim, the hub intake grate angle being less than the rim intake grate angle.

[0053] In Example 18, the subject matter of Examples 16-17 includes, degrees relative to the housing and the marine propulsion system is configurable to produce thrust via the rotatable vector-flow nozzle that varies in a range between one percent and ten percent throughout the rotatable span.

[0054] In Example 19, the subject matter of Examples 16-18 includes, wherein the intake grate has an asymmetrical configuration and the plurality of intake grate blades includes a first plurality of intake grate blades having a first length and a second plurality of intake grate blades having a second length less than the first length.

[0055] In Example 20, the subject matter of Example 19 includes, wherein the first plurality of intake grate blades has a first rim intake grate angle and the second plurality of intake grate blades have a second rim intake grate angle that is less than the first rim intake grate angle.

[0056] Example 21 is an apparatus comprising means to implement of any of Examples 1-20.

[0057] Example 23 is a system to implement of any of Examples 1-20.

[0058] Example 24 is a method to implement of any of Examples 1-20.

[0059] Although teachings have been described with reference to specific example teachings, it will be evident that various modifications and changes may be made to these teachings without departing from the broader spirit and scope of the teachings. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. The accompanying drawings that form a part hereof, show by way of illustration, and not of limitation, specific teachings in which the subject matter may be practiced. The teachings illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other teachings may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various teachings is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.