Axial fan for tunnel ventilation

Abstract

To provide an axial fan for tunnel ventilation which can improve a loss reduction effect.SOLUTION: An axial fan for tunnel ventilation includes: a rotor blade 1 having a spherical tip part 1c; and a casing 3 for covering the spherical tip part 1c of the rotor blade 1. The casing 3 includes: a cylindrical upstream side inner peripheral surface part 3a provided on the upstream side with respect to the rotor blade 1 in the flow direction of the air; and a spherical inner peripheral surface part 3c provided at a portion opposing to the spherical tip part 1c of the rotor blade 1. The spherical inner peripheral surface part 3c of the casing 3 and the spherical tip part 1c of the rotor blade 1 constitute a gap of a constant interval g between a front edge part 1a and a rear edge part 1b of the rotor blade 1. The spherical inner peripheral surface part 3c of the casing 3 forms an annular projection part 3c1 in which a distance Rca from a rotational axis center of the rotor blade 1 is smaller than a distance Rc from the rotational axis center in the upstream side inner peripheral surface part 3a, between itself and the upstream side inner peripheral surface part 3a.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an axial flow fan used for ventilating road tunnels (axial flow fan for tunnel ventilation). [Background technology]

[0002] Axial flow fans for tunnel ventilation are large axial flow fans that are mainly installed in ventilation facilities attached to road tunnels, and there is a demand for reducing power consumption.Patent Document 1 describes a blade tip structure of a rotary machinery device having a blade row attached to a rotor, in which at least a portion of the blade tip surface protrudes in a gentle curve along the axial direction, and the inner surface of the casing facing the blade tip surface is formed with a recess so as to form a convex shape at an approximately constant distance from the blade tip surface (see abstract). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-26904 Summary of the Invention [Problem to be solved by the invention]

[0004] In the shaft end structure of the rotary machinery device of Patent Document 1, sufficient consideration is not given to the relationship between the length of the recess and the length of the blade tip, which may result in a reduced loss reduction effect.

[0005] An object of the present invention is to provide an axial flow fan for tunnel ventilation that can improve the loss reduction effect. [Means for solving the problem]

[0006] In order to achieve the above object, the axial flow fan for tunnel ventilation of the present invention comprises: An axial flow fan for tunnel ventilation comprising: a rotor blade having a spherical tip portion formed into a spherical shape; and a casing covering the spherical tip portion of the rotor blade, wherein the casing has a cylindrical upstream inner circumferential surface portion provided upstream of the rotor blade in an air flow direction, and a spherical inner circumferential surface portion provided spherically at a position facing the spherical tip portion of the rotor blade, the spherical inner peripheral surface of the casing and the spherical tip of the rotor blade define a gap of a fixed interval between a leading edge and a trailing edge of the rotor blade; the spherical inner peripheral surface portion of the casing forms an annular protrusion between the upstream inner peripheral surface portion and the spherical inner peripheral surface portion of the casing, the annular protrusion protruding radially inward from the upstream inner peripheral surface portion along a circumferential direction, The distance of the annular protrusion from the rotation axis of the rotor blade is smaller than the distance of the upstream inner circumferential surface portion from the rotation axis. [Effects of the Invention]

[0007] According to the present invention, it is possible to reduce loss at the tip of the rotor blades and reduce the power consumption of the axial flow fan, thereby improving the loss reduction effect of the axial flow fan for tunnel ventilation. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of an axial flow fan for tunnel ventilation according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view of a rotor blade tip and a casing according to an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram illustrating the length of a rotor blade at a tip portion according to an embodiment of the present invention. [Figure 4] FIG. 4 is a graph showing the relationship between the blade tip clearance ratio and the blade pressure rise according to an embodiment of the present invention. [Figure 5] FIG. 2 is a cross-sectional view of a rotor blade tip and a casing of an axial flow fan for tunnel ventilation, which is a comparative example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described.

[0010] FIG. 1 shows a cross-sectional view of an axial flow fan 100 for tunnel ventilation according to one embodiment of the present invention. In the following explanation, the "axial flow fan for tunnel ventilation" may be referred to as an "axial flow fan." The direction along the center line of the rotation shaft (rotation axis) of the axial flow fan will be referred to as the "axial direction."

[0011] Reference numeral 1 denotes a rotor blade attached to a hub 6, which is a rotor body; 2 denotes a stator blade installed downstream of the rotor blade; 3 denotes a casing that covers the tip of the rotor blade 1 (rotor blade tip) 1c (see Figure 2); 4a and 4b are inner cylinders; and 5a, 5b, and 5c are stays. The casing 3 surrounds the rotor blade 1 on its outer periphery and, together with the inner cylinders 4a and 4b, forms a flow path inside the axial fan. The stays 5a, 5b, and 5c are members that connect the casing 3 to the inner cylinders 4a and 4b. The arrows in the figure indicate the direction of airflow. Also, the dashed-dotted line 100a in the figure represents the axis of rotation (axial center) of the rotor blade 1 in the axial fan 100.

[0012] The problems with axial fans will now be described with reference to Fig. 5. Fig. 5 shows a cross-sectional view of a rotor blade tip 1c and a casing 3' of an axial fan 100' for tunnel ventilation, which is a comparative example to the present invention.

[0013] In the axial flow fan 100' of the comparative example, the rotor blade tip 1c is machined to a spherical shape with a constant radius Rr. Therefore, the outermost diameter (distance from the shaft center to the rotor blade tip 1c) Rra at the rotor blade leading edge 1a and the outermost diameter (distance from the shaft center to the rotor blade tip 1c) Rrb at the rotor blade trailing edge 1b are smaller than the distance Rrc from the shaft center to the rotor blade tip 1c at the rotor blade center (Rra, Rrb <Rrc)。

[0014] The casing 3' has a spherically machined portion 3a' including its inner circumferential surface facing the rotor blade tip 1c. Hereinafter, this portion 3a' will be referred to as the "spherically machined portion." The spherically machined portion 3a' is machined to have a radius Rcs, which is the sum of the distance Rrc from the shaft center to the rotor blade center and the minimum gap g between the rotor blade tip 1c and the inner circumferential surface of the casing 3'.

[0015] In a typical casing, the non-sphericalized portion is cylindrical, and the non-sphericalized portion of the casing 3' of the comparative example is also cylindrical. Therefore, the casing 3' has a cylindrical portion with a radius Rc (Rc = Rrc), which is the same as the distance Rrc from the axial center to the blade tip 1c at the center of the blade, connected to the spherically processed portion 3a' at the front and rear of the blade 1 (upstream and downstream in the air flow). In this case, as shown in Figure 5, the gap between the blade tip 1c and the casing 3 at the leading edge 1a and trailing edge 1b of the blade becomes larger than the set gap g, increasing loss at the blade tip 1c and causing a decrease in the efficiency of the axial flow fan.

[0016] FIG. 2 shows a cross-sectional view of a rotor blade tip portion and a casing according to an embodiment of the present invention. In the axial flow fan 100 of this embodiment, as in the comparative example, the rotor blade tip 1c is machined to a spherical shape with a constant radius Rr. Furthermore, in this embodiment, the gap g between the rotor blade tip 1c and the casing 3 is constant between the rotor blade leading edge 1a and the rotor blade trailing edge 1b. In other words, the rotor blade 1 has a constant gap g between the tip 1c and the casing 3. In the following description, "g" represents the gap or the size (distance) of the gap.

[0017] For this reason, the casing 3 is provided with a spherical inner peripheral surface portion 3c at a position facing the rotor blade tip portion 1c in the air flow direction. The casing 3 has cylindrical inner peripheral surfaces on the upstream and downstream sides with respect to the rotor blade 1, and has cylindrical upstream inner peripheral surface portion 3a and downstream inner peripheral surface portion 3b.

[0018] The spherical inner peripheral surface portion 3c of the casing 3 and the spherical tip portion 1c of the rotor blade 1 define a gap of a constant distance g between the leading edge portion 1a and the trailing edge portion 1b of the rotor blade 1. The spherical inner peripheral surface portion 3c of the casing 3 forms an annular protrusion 3c1 between itself and the upstream inner peripheral surface portion 3a, protruding radially inward from the upstream inner peripheral surface portion 1a along the circumferential direction. The annular protrusion 3c1 has a distance Rca from the rotation axis 100a of the rotor blade 1 that is smaller than a distance Rc from the rotation axis 100a of the upstream inner peripheral surface portion 1a, Furthermore, an annular protrusion 3c2 that protrudes radially inward from the downstream inner circumferential surface portion 3b along the circumferential direction is formed between the spherical inner circumferential surface portion 3c of the casing 3 and the downstream inner circumferential surface portion 3b. The distance Rcb of the annular protrusion 3c2 from the rotation axis 100a of the rotor blade 1 is smaller than the distance Rc from the rotation axis 100a of the downstream inner circumferential surface portion 3b.

[0019] In this embodiment, the spherical tip 1c of the rotor blade 1 is formed to a constant radius Rr. Therefore, the spherical inner peripheral surface 3c of the casing 3 is formed to a radius (Rr+g) obtained by adding the radius Rr of the spherical tip 1c of the rotor blade 1 to the gap g formed between the spherical inner peripheral surface 3c and the spherical tip 1c of the rotor blade 1.

[0020] At the leading edge 1a and trailing edge 1b of the rotor blade 1, the distances Rca and Rcb from the axial center 100a to the casing 3 on the inner surface of the casing 3 are smaller than the casing radius Rc of the cylindrical portion, and the radius is expanded to Rc before and after the rotor blade 1 (upstream and downstream sides).

[0021] That is, by keeping the gap g between the rotor blade tip 1c and the casing 3 constant, annular protrusions (convex portions) 3b, 3c that protrude radially inward along the circumferential direction are formed on the inner peripheral surface 3a of the casing 3, and the distances Rca and Rcb may become smaller than the cylindrical casing radius Rc. Convex portion 3b is located upstream of the air flow relative to the center of the rotor blade in the axial direction, and convex portion 3c is located downstream of the air flow relative to the center of the rotor blade in the axial direction.

[0022] More precisely, Rca and Rcb are the distances from the shaft center 100a to the inner peripheral surface 3a of the casing 3, and Rc is the radius of the inner peripheral surface 3a of the casing 3.

[0023] According to this embodiment, the entire rotor blade tip 1c can be made into the gap g, and the casing radius Rc can be increased on the upstream and downstream sides of the rotor blade tip 1c in the air flow, thereby reducing loss at the rotor blade tip 1c and improving the efficiency of the axial flow fan.

[0024] Here, the rotor blade 1 will be briefly described with reference to Fig. 3. Fig. 3 shows the rotor blade length C at the rotor blade tip 1c according to an embodiment of the present invention. Fig. 3 shows the rotor blade tip 1c as viewed from the radial direction. The distance between the upstream end of the rotor blade 1 in the air flow (the leading edge 1a of the rotor blade) and the downstream end of the air flow (the trailing edge 1b of the rotor blade) is defined as the "blade length," and the rotor blade tip 1c has a length C as the rotor blade length.

[0025] Fig. 4 shows the relationship between the rotor blade tip clearance ratio and rotor blade pressure rise according to an embodiment of the present invention, which shows the change in rotor blade pressure rise relative to the rotor blade tip clearance g. In Figure 4, the horizontal axis represents the gap ratio g / C based on the blade length C at the blade tip 1c shown in Figure 3, and the vertical axis represents the dimensionless pressure rise P / P0 based on the blade pressure rise when there is no gap.

[0026] The pressure rise and drop at the rotor blade 1 decreases gradually up to a clearance ratio g / C of 1.5%, but decreases significantly in the range of 1.5% to 3%. Furthermore, when the clearance ratio g / C is 3% or more, the drop in total pressure becomes gentle, but when the clearance ratio g / C is 3% or more, the loss at the rotor blade tip 1c becomes large, reaching approximately 9%.

[0027] The gap ratio g / C of the rotor blade tip 1c cannot be set to zero. For this reason, in this embodiment, the gap g between the rotor blade tip 1c and the casing 3 is kept constant between the rotor blade leading edge 1a and the rotor blade trailing edge 1b, and the gap ratio g / C of the rotor blade tip 1c is set to a range of 0.5% to 1.5%. In other words, the ratio of the gap width g to the length C of the spherical tip of the rotor blade 1 is in the range of 0.5% to 1.5%.

[0028] According to this embodiment, the gap g at the rotor blade tip 1c can be maintained within an appropriate range, so that the loss at the rotor blade tip 1c can be reduced and the efficiency of the axial flow fan can be improved.

[0029] As described above, the tunnel ventilation axial fan 100 of this embodiment has the following features, for example.

[0030] (1) An axial flow fan for tunnel ventilation (100) comprising: a rotor blade (1) having a spherical tip portion (1c) formed into a spherical shape; and a casing (3) covering the spherical tip portion (1c) of the rotor blade (1), wherein the casing (3) has a cylindrical upstream inner circumferential surface portion (3a) provided upstream of the rotor blade (1) in the air flow direction; and a spherical inner circumferential surface portion (3c) provided spherically at a position facing the spherical tip portion (1c) of the rotor blade (1), The spherical inner peripheral surface portion 3c of the casing 3 and the spherical tip portion 1c of the rotor blade 1 form a gap of a constant distance g between the leading edge portion 1a and the trailing edge portion 1b of the rotor blade 1, The spherical inner peripheral surface portion 3c of the casing 3 forms, between itself and the upstream inner peripheral surface portion 3a, an annular protruding portion 3c1 that protrudes radially inward from the upstream inner peripheral surface portion 3a along the circumferential direction, The distance Rca of the annular protrusion 3c1 from the rotation axis 100a of the rotor blade 1 is smaller than the distance of the upstream inner circumferential surface portion 3a from the rotation axis 100a.

[0031] (2) The spherical tip 1c of the rotor blade 1 is formed with a constant radius Rr. The spherical inner peripheral surface portion 3c of the casing 3 is formed to have a radius (Rr+g) which is the radius Rr of the spherical tip portion 1c of the rotor blade 1 plus the gap width g formed between the spherical inner peripheral surface portion 3c and the spherical tip portion 1c of the rotor blade 1.

[0032] (3) The casing 3 has a cylindrical downstream inner circumferential surface portion 3b provided downstream of the rotor blade 1 in the air flow direction, The spherical inner peripheral surface portion 3c of the casing 3 forms, between itself and the downstream inner peripheral surface portion 3b, an annular protrusion 3c2 that protrudes radially inward from the downstream inner peripheral surface portion 3b along the circumferential direction, and whose distance Rcb from the rotation axis 100a of the rotor blade 1 is smaller than the distance Rc from the rotation axis 100a at the downstream inner peripheral surface portion 3b.

[0033] (4) The ratio of the gap distance g to the length C of the spherical tip of the rotor blade 1 is in the range of 0.5% to 1.5%.

[0034] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the configurations. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0035] 1... rotor blade, 1a... leading edge portion of rotor blade 1, 1b... trailing edge portion of rotor blade 1, 1c... spherical tip portion of rotor blade 1, 3... casing, 3a... upstream inner peripheral surface portion of casing 3, 3b... downstream inner peripheral surface portion of casing 3, 3c... spherical inner peripheral surface portion of casing 3, 3c1... annular protrusion portion, 3c2... annular protrusion portion, 100... tunnel ventilation axial flow fan, 100a... rotation axis of rotor blade 1, C... length of spherical tip portion of rotor blade 1, g... spherical Gap or gap interval between the tip portion 1c and the spherical inner surface portion 3c of the casing 3, Rc...distance from the rotation axis 100a at the upstream inner surface portion 3a and distance from the rotation axis 100a at the downstream inner surface portion 3a, Rca...distance from the rotation axis 100a of the rotor blade 1 at the annular protrusion portion 3c1, Rcb...distance from the rotation axis 100a of the rotor blade 1 at the annular protrusion portion 3c2, Rr...radius of the spherical tip portion 1c of the rotor blade 1.

Claims

1. An axial flow fan for tunnel ventilation comprising: a rotor blade having a spherical tip portion formed into a spherical shape; and a casing covering the spherical tip portion of the rotor blade, wherein the casing has a cylindrical upstream inner circumferential surface portion provided upstream of the rotor blade in an air flow direction, and a spherical inner circumferential surface portion provided spherically at a position facing the spherical tip portion of the rotor blade, the spherical inner peripheral surface of the casing and the spherical tip of the rotor blade define a gap of a fixed interval between a leading edge and a trailing edge of the rotor blade; the spherical inner peripheral surface portion of the casing forms an annular protrusion between the upstream inner peripheral surface portion and the spherical inner peripheral surface portion of the casing, the annular protrusion protruding radially inward from the upstream inner peripheral surface portion along a circumferential direction, 10. An axial flow fan for tunnel ventilation, wherein the distance of the annular protrusion from the rotation axis of the rotor blade is smaller than the distance of the upstream inner circumferential surface portion from the rotation axis.

2. The axial flow fan for tunnel ventilation according to claim 1, The spherical tip of the blade is formed to a constant radius, 1. An axial flow fan for tunnel ventilation, wherein the spherical inner circumferential surface of the casing is formed to have a radius that is the sum of the radius of the spherical tip of the rotor blade and the gap formed between the spherical inner circumferential surface and the spherical tip of the rotor blade.

3. The axial flow fan for tunnel ventilation according to claim 2, the casing has a cylindrical downstream inner circumferential surface portion provided downstream of the rotor blade in the air flow direction, a downstream inner circumferential surface portion of the casing and a downstream inner circumferential surface portion of the casing, the downstream inner circumferential surface portion being spaced apart from the downstream inner circumferential surface portion by a distance from the axis of rotation of the rotor blades to the downstream inner circumferential surface portion;

4. The axial flow fan for tunnel ventilation according to any one of claims 1 to 3, 1. An axial flow fan for tunnel ventilation, wherein a ratio of the gap width to the length of the spherical tip of each rotor blade is in the range of 0.5% to 1.5%.

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