A fan blade flow channel plate rotation strength test device

Abstract

The present invention relates to the field of aero-engine technology, and in particular to a fan blade flow channel plate rotational strength test device, which includes a fan impeller, a fan simulation blade 1, a fan simulation blade 2, a lower clamping plate, an upper clamping plate, and a transfer core shaft. In the device, the upper clamping plate and the lower clamping plate are respectively clearance-matched with the upper end mating surface 2 and the lower end mating surface 1 of the fan blade flow channel plate test piece, and the fan simulation blade 1 and the fan simulation blade 2 are respectively clearance-matched with the concave curved surface and the convex curved surface of the fan blade flow channel plate test piece. Under the premise of ensuring the assembly accuracy requirements of the fan blade flow channel plate test piece, the device greatly reduces the difficulty of the test piece assembly and dynamic balancing test, significantly shortens the test preparation cycle, thereby improving its rotational strength test efficiency, reducing the test device installation cost, and at the same time realizing the strain measurement of the fan blade flow channel plate.

Description

Technical Field

[0001] The present invention relates to the technical field of aviation engines, and in particular to a device for testing the rotational strength of a fan blade flow channel plate. Background Art

[0002] The fan blade flow channel plate is a rotating structural component between the low-pressure fan stage rotor of an axial-flow aircraft engine (such as Figure 1 Its main function is to form the flow path of the engine intake section, and it mainly bears aerodynamic loads and centrifugal loads during operation.

[0003] In the fan blade flow channel plate rotation strength test, the current test device is equipped with test parts to assemble the flow channel plate test piece. The assembly structure is as follows: Figure 2 As shown, the outer diameter of the structure D≥φ1900mm. The accompanying test parts include: fan disk 21, fan blades 22, intake cone rear section 23, boost stage drum seal 24 and boost stage drum 25. The intake cone rear section 23, boost stage drum seal 24 and fan disk 21 need to be hot-assembled; the upper and lower end surfaces of the fan blade 22 fit seamlessly with the intake cone rear section 23 and boost stage drum seal 24, and its side faces fit seamlessly with the left concave surface 111 and the right convex surface 121 of the fan blade upper flow channel surface. The test device with its structural dimensions and assembly method has the disadvantages of high test cost, complex test piece assembly, and the dynamic balancing test before the test is limited to the use of a vertical balancing machine, and it is impossible to arrange a strain measurement line. This results in a long test preparation cycle and low test efficiency. At the same time, it is impossible to achieve strain measurement on the surface of the fan blade flow channel plate reinforcement rib 12. Summary of the Invention

[0004] The purpose of the present invention is to reduce the assembly difficulty of the fan blade flow channel plate test piece, realize dynamic balancing on the existing horizontal balancing machine, reduce the end test preparation cycle, and meet the arrangement of the strain measurement line, thereby improving its test efficiency, reducing the test cost, and realizing the strain measurement of the fan blade flow channel plate at the same time. A fan blade flow channel plate rotation strength test device is specially provided.

[0005] In order to achieve the above-mentioned purpose, the present invention provides the following technical solutions: a fan blade flow channel plate rotation strength test device, the fan blade flow channel plate includes: a flow channel surface, a reinforcing rib, a left concave surface, a right convex surface, a lower end matching surface 1, and an upper end matching surface 2; the fan blade flow channel plate rotation strength test device includes: a fan wheel, a fan simulation blade 1, a fan simulation blade 2, a lower clamping plate, an upper clamping plate and a transfer core shaft; the fan simulation blade 1 and the fan simulation blade 2 are respectively connected to the outer side wall of the fan wheel through one end, and the end of the fan simulation blade 1 away from the fan wheel is clamped in On the left concave surface of the fan blade flow channel plate, the end of the fan simulation blade 2 away from the fan wheel is clamped on the right convex surface of the fan blade flow channel plate; one end of the lower clamping plate is fixedly connected to the lower end surface of the fan wheel, and the other end is provided with an upward vertical assembly boss 1, which is used to constrain the lower end mating surface 1 of the fan blade flow channel plate; one end of the upper clamping plate is fixedly connected to the upper end surface of the fan wheel, and the other end is freely provided with a downward vertical assembly boss 2, which is used to constrain the upper end mating surface 2 of the fan blade flow channel plate; one end of the adapter core shaft is installed at the center position of the upper end surface of the fan wheel, and the other end is connected to the external power source.

[0006] Preferably, a plurality of tenons are provided on the outer surface of the fan impeller along the axial direction, and each of the tenons is provided with a pin hole 1; the fan simulation blade 1 and the fan simulation blade 2 are mortise-jointed with the corresponding tenon through tenon 1 and tenon 2 respectively, and the tenon 1 and the tenon 2 are provided with pin hole 2 and pin hole 3 corresponding to the pin hole 1 respectively.

[0007] Preferably, one end of the fan blade flow channel plate corresponding to the fan blade 1 is provided with a curved boss that closely matches the left concave surface; and one end of the fan blade flow channel plate corresponding to the fan blade 2 is provided with a curved concave platform that closely matches the right convex surface.

[0008] Preferably, the upper and lower end surfaces of the fan impeller are circumferentially provided with a plurality of threaded holes; the lower clamping plate is provided with a light hole 1 at one end corresponding to the fan impeller, and is connected to the corresponding threaded hole 1 by a bolt passing through the light hole 1; the upper clamping plate is provided with a light hole 2 at one end corresponding to the fan impeller, and is connected to the corresponding threaded hole 1 by a bolt passing through the light hole 2.

[0009] Preferably, the centers of the two end surfaces of the fan impeller respectively have symmetrical weight-reducing holes, and an assembly platform is provided in the center of the weight-reducing hole corresponding to the upper end surface of the fan impeller, and the upper end surface of the assembly platform is provided with a positioning groove and two threaded holes; a flange is provided at one end of the adapter core shaft, and a light hole three is provided on the flange, and a positioning platform two is provided on the bottom surface of the flange, and the positioning platform two cooperates with the positioning groove, and the adapter core shaft and the assembly platform are fixedly connected by bolts.

[0010] Preferably, the assembly boss 1 is provided with a mating surface 1 on the side facing the fan wheel, and the mating surface 1 is matched with the lower end mating surface 1; the assembly boss 2 is provided with a mating surface 3 on the side facing the fan wheel, and the mating surface 3 is matched with the upper end mating surface 2.

[0011] Preferably, a raised lock buckle 1 is vertically provided at one end of the lower clamping plate away from the assembly boss 1, and the lock buckle 1 cooperates with the inner side wall of the weight-reducing hole through a mating surface 2; a balancing boss 2 is vertically provided at one end of the upper clamping plate away from the assembly boss 2, and the balancing boss 2 cooperates with the inner side surface of the weight-reducing hole through a mating surface 4.

[0012] Preferably, through hole one and through hole two are provided in the center of the assembly table and the transfer core shaft; and also include strain measurement lines respectively passing through the through hole one and the through hole two, the strain measurement lines extending toward the outer surface of the fan impeller and being fixed to the outer surface of the fan impeller through a fixing plate.

[0013] Preferably, the fan wheel is made of high-strength heat-resistant martensitic stainless steel 1Cr11 Ni2W2MoV; the fan simulation blade 1, fan simulation blade 2, lower clamping plate and upper clamping plate are made of high-yield ratio titanium alloy TC4; the transfer core shaft is made of high-strength alloy structural steel 40CrNiMo.

[0014] Preferably, the method of use comprises the following steps:

[0015] a. First install the fan simulation blade 1 in the mortise and tenon groove on the left side of the fan wheel;

[0016] b. Install the second fan simulation blade at the mortise and tenon groove on the right side of the fan wheel;

[0017] c. Assemble the fan blade flow channel plate test piece 1 between the fan simulation blade 1 and the fan simulation blade 2;

[0018] d. Then install and fix the lower clamping plate to the lower end surface of the fan wheel, and install and fix the upper clamping plate to the upper end surface of the fan wheel;

[0019] e. Then follow steps a to d to install and secure another fan blade flow channel plate on the other side in rotational symmetry.

[0020] f. Finally, the adapter core shaft 36 is installed and fixed on the upper end surface assembly platform of the fan impeller.

[0021] The beneficial effects of the present invention are as follows: the fan blade flow channel plate rotation strength test device, under the premise of ensuring the assembly accuracy requirements of the fan blade flow channel plate test piece, greatly reduces the assembly difficulty of the test piece, realizes the dynamic balancing test on the existing horizontal balancing machine, and significantly shortens the test preparation cycle. The assembly and dynamic balancing time test is shortened from more than 48 hours to less than 6 hours, thereby improving the efficiency of the rotation strength test, reducing the cost of the test device, and at the same time realizing the strain measurement of the fan blade flow channel plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a structural stereogram of the fan blade flow channel plate test piece;

[0024] Figure 2 This is a schematic diagram of the structure of the test device for the fan blade flow plate;

[0025] Figure 3 It is a structural stereogram of the present invention;

[0026] Figure 4 This is a schematic diagram of the strain measurement circuit arrangement implemented in the present invention;

[0027] Figure 5 yes Figure 3 A structural perspective view of the middle piece 31;

[0028] Figure 6 yes Figure 3 A structural perspective view of the middle piece 32;

[0029] Figure 7 yes Figure 3 A structural perspective view of the middle piece 33;

[0030] Figure 8 yes Figure 3 A structural perspective view of the middle piece 34;

[0031] Figure 9 yes Figure 3 A structural perspective view of the middle piece 35;

[0032] Figure 10 yes Figure 3 A structural perspective view of the middle piece 36. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] according to Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 As shown, a fan blade flow channel plate rotation strength test device, the fan blade flow channel plate 1 includes: a flow channel surface 11, a reinforcing rib 12, a left concave surface 111, a right convex surface 112, a lower end mating surface 113, and an upper end mating surface 2 114; the fan blade flow channel plate rotation strength test device includes: a fan wheel 31, a fan simulation blade 1 32, a fan simulation blade 2 33, a lower clamping plate 34, an upper clamping plate 35 and an adapter core shaft 36; the fan simulation blade 1 32 and the fan simulation blade 2 33 are respectively connected to the outer side wall of the fan wheel 31 through one end, and the end of the fan simulation blade 1 32 away from the fan wheel 31 is clamped on the fan blade flow channel plate 1 On the left concave surface 111, the end of the fan simulation blade 2 33 away from the fan impeller 31 is clamped on the right convex surface 112 of the fan blade flow channel plate 1; one end of the lower clamping plate 34 is fixedly connected to the lower end surface of the fan impeller 31, and the other end is provided with an upward vertical assembly boss 1 341, which is used to constrain the lower end mating surface 113 of the fan blade flow channel plate 1; one end of the upper clamping plate 35 is fixedly connected to the upper end surface of the fan impeller 31, and the other end is freely provided with a downward vertical assembly boss 2 351, which is used to constrain the upper end mating surface 2 114 of the fan blade flow channel plate 1; one end of the adapter core shaft 36 is installed at the center position of the upper end surface of the fan impeller 31, and the other end is connected to the external power source.

[0035] A plurality of tenons 311 are provided on the outer surface of the fan impeller 31 along the axial direction, and each tenon 311 is provided with a pin hole 1 312; the fan simulation blade 1 32 and the fan simulation blade 2 33 are mortised with the corresponding tenon 311 through a tenon 1 321 and a tenon 2 331 respectively, and the tenon 1 321 and the tenon 2 331 are provided with a pin hole 2 322 and a pin hole 332 corresponding to the pin hole 1 312 respectively.

[0036] The fan simulation blade 1 32 corresponds to one end of the fan blade flow channel plate 1 and is provided with a curved surface boss 323 that closely matches the left concave surface 111; the fan simulation blade 2 33 corresponds to one end of the fan blade flow channel plate 1 and is provided with a curved surface concave platform 333 that closely matches the right convex surface 112.

[0037] The upper and lower end surfaces of the fan impeller 31 are circumferentially provided with a plurality of threaded holes 316; the lower clamping plate 34 is provided with a light hole 345 at one end corresponding to the fan impeller 31, and is connected to the corresponding threaded hole 316 by a bolt passing through the light hole 345; the upper clamping plate 35 is provided with a light hole 2 356 at one end corresponding to the fan impeller 31, and is connected to the corresponding threaded hole 1 316 by a bolt passing through the light hole 2 356.

[0038] There are symmetrical weight-reducing holes 313 in the center of both end surfaces of the fan impeller 31, and an assembly platform 314 is provided in the center of the weight-reducing hole 313 corresponding to the upper end surface of the fan impeller 31. The upper end surface of the assembly platform 314 is provided with a positioning groove 315 and a second threaded hole 317; a flange 362 is provided at one end of the adapter core shaft 36, and a third light hole 364 is provided on the flange 362. A second positioning platform 363 is provided on the bottom surface of the flange, and the second positioning platform 363 cooperates with the positioning groove 315, and the adapter core shaft 36 and the assembly platform 314 are fixedly connected by bolts.

[0039] The assembly boss 1 341 is provided with a mating surface 1 343 on the side facing the fan wheel 31, and the mating surface 1 343 is matched with the lower end mating surface 1 113; the assembly boss 2 351 is provided with a mating surface 354 on the side facing the fan wheel 31, and the mating surface 354 is matched with the upper end mating surface 2 114.

[0040] A raised lock buckle 342 is vertically provided at one end of the lower clamping plate 34 away from the assembly boss 1 341, and the lock buckle 1 342 cooperates with the inner wall of the weight-reducing hole 313 through the mating surface 2 344; a balanced boss 2 352 is vertically provided at one end of the upper clamping plate 35 away from the assembly boss 2 351, and the balanced boss 2 352 cooperates with the inner side surface of the weight-reducing hole 313 through the mating surface 4 355.

[0041] The assembly platform 314 and the adapter mandrel 36 are centrally provided with a first through-hole 318 and a second through-hole 366. Strain measurement wires 5 are also provided, extending through these first and second through-holes 318 and 366, respectively. These wires extend toward the outer surface of the fan disc 31 and are secured to the outer surface of the disc 31 via a fixing plate 6. This arrangement allows for the routing and extraction of the strain measurement wires, which are ultimately connected to strain measurement instruments outside the vacuum chamber of the disc rotation tester.

[0042] The fan wheel 31 is made of high-strength heat-resistant martensitic stainless steel 1Cr11 Ni2W2MoV; the fan simulation blade 1 32, the fan simulation blade 2 33, the lower clamping plate 34 and the upper clamping plate 35 are made of high-yield ratio titanium alloy TC4; the adapter core shaft 36 is made of high-strength alloy structural steel 40CrNiMo.

[0043] The upper and lower end surfaces of the fan simulation blade 1 32 and the fan simulation blade 2 33 are respectively not less than 20 mm away from the upper and lower end surfaces of the fan impeller 31; the assembly clearance between the curved boss 323 on the left side of the test device and the left concave surface 111 does not exceed 0.05 mm; the assembly clearance between the curved concave platform 333 of the side fan simulation blade 2 on the right side of the test device and the right convex surface 112 does not exceed 0.05 mm; on the lower end mating surface 1 13; the unilateral assembly clearance is 0.7~0.8 mm; the unilateral assembly clearance between the mating surface 354 and the upper end mating surface 2 114 is 0.7~0.8 mm.

[0044] The threaded hole 316 is used for assembling a standard balancing bolt in a non-assembly position during a dynamic balancing test, and the through hole 318 is used for passing the strain measurement line 5.

[0045] In addition, the assembly height of the fan simulation blade 1 32 and the fan simulation blade 2 33 is fixed by assembling standard cylindrical pins in the pin hole 1 312 and the pin hole 2 322, ensuring that the upper and lower end surfaces of the fan simulation blade 1 32 are respectively not less than 20 mm away from the upper and lower end surfaces of the fan impeller 31, meeting the arrangement of the strain measurement line 5.

[0046] The second positioning platform 363 is fixed to the hollow rotating spindle 7 in the vacuum chamber of the wheel rotation tester by means of standard bolts on the third threaded hole 364. The second through hole 366 communicates with the first through hole 318 on the fan wheel for leading out the strain measurement line 5.

[0047] The method of using the fan blade flow channel plate rotation strength test device is as follows:

[0048] a. First, install the fan simulation blade 1 32 at the left groove of the fan wheel 31;

[0049] b. Install the second fan simulation blade 33 at the right side of the fan wheel 31;

[0050] c. Assemble the fan blade flow channel plate test piece 1 between the fan simulation blade 1 32 and the fan simulation blade 2 33;

[0051] d. Then, fix the lower card plate to the lower end surface of the fan wheel 31, and fix the upper card plate to the upper end surface of the fan wheel 32;

[0052] e. Then, follow steps a to d to install and fix another fan blade flow channel plate test piece 1 on the other side in rotational symmetry;

[0053] f. Finally, the adapter core shaft 36 is installed and fixed on the upper end surface assembly platform of the fan impeller.

[0054] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A fan blade flow channel plate rotation strength test device, the fan blade flow channel plate (1) comprising: A flow channel surface (11), a reinforcing rib (12), a left concave curved surface (111), a right convex curved surface (112), a lower end matching surface 1 (113), and an upper end matching surface 2 (114); The device is characterized in that the fan blade flow channel plate rotation strength test device comprises: a fan wheel (31), a fan simulation blade 1 (32), a fan simulation blade 2 (33), a lower clamping plate (34), an upper clamping plate (35) and a transfer core shaft (36); The fan simulation blade 1 (32) and the fan simulation blade 2 (33) are respectively connected to the outer wall of the fan wheel disc (31) through one end, the end of the fan simulation blade 1 (32) away from the fan wheel disc (31) is clamped on the left concave surface (111) of the fan blade flow channel plate (1), and the end of the fan simulation blade 2 (33) away from the fan wheel disc (31) is clamped on the right convex surface (112) of the fan blade flow channel plate (1); One end of the lower clamping plate (34) is fixedly connected to the lower end surface of the fan wheel (31), and the other end is provided with an upward vertical assembly boss (341) for constraining the lower end matching surface (113) of the fan blade flow channel plate (1); one end of the upper clamping plate (35) is fixedly connected to the upper end surface of the fan wheel (31), and the other end is provided with a downward vertical assembly boss (351) for constraining the upper end matching surface (114) of the fan blade flow channel plate (1); One end of the transfer core shaft (36) is mounted at the center of the upper end surface of the fan wheel (31), and the other end is connected to an external power source; The upper and lower end surfaces of the fan simulation blade 1 (32) and the fan simulation blade 2 (33) are respectively not less than 20 mm away from the upper and lower end surfaces of the fan wheel (31); the assembly clearance between the curved boss (323) on the left side of the test device and the left concave curved surface (111) does not exceed 0.05 mm; the assembly clearance between the curved concave boss (333) on the right side of the fan simulation blade 2 and the right convex curved surface (112) does not exceed 0.05 mm; the unilateral assembly clearance on the lower end mating surface 1 (113) is 0.7 to 0.8 mm; the unilateral assembly clearance between the mating surface 3 (354) and the upper end mating surface 2 (114) is 0.7 to 0.8 mm.

2. A fan blade flow channel plate rotation strength test device according to claim 1, characterized in that: The outer surface of the fan wheel (31) is provided with a plurality of mortises (311) along the axial direction, and each of the mortises (311) is provided with a pin hole (312); the fan simulation blade (32) and the fan simulation blade (33) are mortised with the corresponding mortise (311) through a tenon (321) and a tenon (331), respectively, and the tenon (321) and the tenon (331) are provided with a pin hole (322) and a pin hole (332) corresponding to the pin hole (312).

3. A fan blade flow channel plate rotation strength test device according to claim 2, characterized in that: The fan simulation blade 1 (32) is provided with a curved surface boss (323) that closely matches the left concave surface (111) at one end of the fan blade flow channel plate (1); One end of the fan blade flow channel plate (1) corresponding to the second fan simulation blade (33) is provided with a curved concave platform (333) that closely matches the right convex curved surface (112).

4. A fan blade flow channel plate rotation strength test device according to claim 3, characterized in that: The upper and lower end surfaces of the fan wheel (31) are both circumferentially provided with a plurality of threaded holes (316); The lower card plate (34) is provided with a light hole (345) at one end corresponding to the fan wheel (31), and is connected to the corresponding threaded hole (316) via a bolt passing through the light hole (345); The upper clamping plate (35) is provided with a second light hole (356) at one end corresponding to the fan wheel (31), and is connected to the corresponding threaded hole (316) via a bolt passing through the second light hole (356).

5. A fan blade flow channel plate rotation strength test device according to claim 4, characterized in that: The centers of both end surfaces of the fan wheel disc (31) are respectively provided with symmetrical weight-reducing holes (313); an assembly platform (314) is provided in the center of the weight-reducing holes (313) corresponding to the upper end surface of the fan wheel disc (31); and a positioning groove (315) and a second threaded hole (317) are provided on the upper end surface of the assembly platform (314); A flange (362) is provided at one end of the transfer core shaft (36), a light hole (364) is provided on the flange (362), a positioning platform (363) is provided on the bottom surface of the flange, the positioning platform (363) is matched with the positioning groove (315), and the transfer core shaft (36) is fixedly connected with the assembly platform (314) by bolts.

6. A fan blade flow channel plate rotation strength test device according to claim 5, characterized in that: The assembly boss 1 (341) is provided with a matching surface 1 (343) on a side facing the fan wheel (31), and the matching surface 1 (343) is matched with the lower end matching surface 1 (113); A third mating surface (354) is provided on the side of the second assembly boss (351) facing the fan wheel (31), and the third mating surface (354) is matched with the second upper end mating surface (114).

7. A fan blade flow channel plate rotation strength test device according to claim 6, characterized in that: The lower clamping plate (34) is vertically provided with a raised lock buckle (342) at one end away from the assembly boss (341), and the lock buckle (342) is matched with the inner wall of the weight-reducing hole (313) through the matching surface (344); the upper clamping plate (35) is vertically provided with a balancing boss (352) at one end away from the assembly boss (351), and the balancing boss (352) is matched with the inner side surface of the weight-reducing hole (313) through the matching surface (355).

8. The fan blade flow channel plate rotation strength test device according to claim 7, characterized in that: A through hole 1 (318) and a through hole 2 (366) are provided at the center of the assembly platform (314) and the transfer core shaft (36); and a strain measurement line (5) respectively passing through the through hole 1 (318) and the through hole 2 (366), wherein the strain measurement line (5) extends toward the outer surface of the fan wheel (31) and is fixed to the outer surface of the fan wheel (31) via a fixing plate (6).

9. A fan blade flow channel plate rotation strength test device according to claim 8, characterized in that: The fan wheel (31) is made of high-strength heat-resistant martensitic stainless steel 1Cr11 Ni2W2MoV; the fan simulation blade 1 (32), the fan simulation blade 2 (33), the lower clamping plate (34) and the upper clamping plate (35) are made of titanium alloy TC4 with a high yield ratio; and the transfer core shaft (36) is made of high-strength alloy structural steel 40CrNiMo.

10. A fan blade flow channel plate rotation strength test device according to claim 9, characterized in that: The usage includes the following steps: a. First, install the fan simulation blade 1 (32) at the left side groove of the fan wheel (31); b. Install the second fan simulation blade (33) at the right side of the fan wheel (31); c. Assemble the fan blade flow channel plate test piece 1 between the fan simulation blade 1 (32) and the fan simulation blade 2 (33); d. Then, the lower card plate is fixed to the lower end surface of the fan wheel (31), and the upper card plate is fixed to the upper end surface of the fan wheel (32); e. Then, follow steps a to d to install and fix another fan blade flow channel plate (1) on the other side in a rotationally symmetrical manner; f. Finally, the adapter core shaft 36 is installed and fixed on the upper end surface assembly platform of the fan impeller.

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