JP2993164B2 - Axial flow type fluid machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial flow type fluid machine used for an incompressible fluid.

[0002]

2. Description of the Related Art An axial flow type fluid machine such as a pump generally comprises a suction bell mouth, a front guide blade, an impeller, a rear guide blade, and a discharge pipe. The impeller is mounted on a pump shaft driven by a prime mover, and fluid is discharged from the front guide blade side to the rear guide blade side by rotation of the impeller.

[0003] As a known example showing the structure of this type of axial flow type fluid machine, a pump diagram collection subcommittee of the Japan Society of Mechanical Engineers:
“Mechanical Drawing Pump” (December 1972, The Japan Society of Mechanical Engineers)
p.57 and p.59).

[0004]

The high-speed miniaturization of the pump can be achieved by a high specific speed ratio (high Ns). To achieve this, it is necessary to reduce the hub ratio and increase the flow passage area.
The developed view of a cylindrical cross-section of a pump diameter D _g shown in FIG. 20 (a). The mounting angle β _i ′ of the impeller blade blade element is expressed by the following equation.

[0005]

(Equation 1)

The following can be understood from the velocity triangle shown in FIG. That is, as the hub ratio decreases, the peripheral speed U decreases in proportion to the hub ratio, but the axial inflow speed C ₁
Does not decrease in proportion to the radius, the inflow angle β ₁ becomes very large. Therefore, the blade mounting angle β _i rapidly increases on the hub side as shown in FIG.

On the other hand, the load on the blade blade is expressed by the following equation.

[0008]

(Equation 2)

[0009] design theory lift issuing from the hub of the impeller over tip (constant), since W _∞ is small becomes beta _∞ increases closer to the hub, the load and lift coefficient of the wing blade element increases. Relationship between the load of the blade and (C _L · l / t) and the radius is shown in FIG. From this figure, it can be seen that the load generally increases extremely as the radius decreases. Therefore, in order to cope with this increase in load, it is necessary to increase the angle of attack α of the blade blade element.
_i ) is even larger.

As described above, in the prior art, when the hub ratio required for increasing the Ns is reduced, the difference between the tip blade angle and the hub blade angle becomes large, resulting in a very twisted blade. There is a problem that it is not preferable.

On the other hand, as shown in FIG. 6, when the angle of attack (α) is increased in order to obtain a large lift coefficient with the blade element, the lift ratio increases sharply, the loss of the impeller increases, and the margin to the stall point is increased. There is also a problem that it will be reduced.

As described above, in the prior art, when the hub ratio is reduced, the torsion of the impeller is increased, which is not preferable in terms of manufacturing and strength, and the performance of the impeller is reduced.

According to the present invention, since the twist of the blade between the hub and the tip is reduced, the manufacture of the blade is facilitated.
It is an object of the present invention to provide an axial flow type fluid machine with improved blade strength.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide a front guide vane fixed to a hub and a cascade satisfying a speed triangle determined from a design theoretical head using a velocity of a flow flowing out of the front guide vane as an inflow velocity vector. In the axial-flow type fluid machine provided with an impeller having a front guide blade and a rear guide vane, the front guide vane has a blade thickness center line facing downstream in a hub-side cylindrical cross section and the rotation of the impeller relative to a rotation axis direction. This is achieved by connecting and forming a blade blade element inclined in a direction opposite to the direction and a blade blade center line parallel to the rotation axis direction in the cylindrical section on the tip side.

[0015] Further, the object is to provide an impeller having a front guide blade fixed to a hub, a blade row satisfying a speed triangle determined from a design theoretical head using a velocity of a flow flowing out of the front guide blade as an inflow velocity vector. In the axial-flow type fluid machine including the rear guide blades, the front blades may be arranged such that the blade thickness center line faces downstream in the cylindrical section on the hub side and is located on the side opposite to the rotation direction of the impeller with respect to the rotation axis direction. This is achieved by the fact that the inclined vane element extends radially to the middle of the flow path.

Furthermore, an object of the present invention is to provide an impeller having a front guide blade fixed to a hub, and a cascade satisfying a speed triangle determined from a design theoretical head using a velocity of a flow flowing out of the front guide blade as an inflow velocity vector. In the axial-flow type fluid machine including the rear guide blade, the front proposed blade is a blade in which a blade thickness center line in a cylindrical cross section is inclined toward a downstream side with respect to a rotation axis direction in a direction opposite to a rotation direction of the impeller. This is achieved by extending the blade elements in the radial direction to the full length of the flow path and making the blade blade elements of the tip parallel to the axis of rotation in the cylindrical cross section.

[0017]

The front guide blade provided at the front end of the impeller and having a hub-side cross section gives the impeller a swirling flow in a direction opposite to the rotation of the impeller.
As a result, the relative inflow angle to the impeller becomes small, and the difference in the blade mounting angle between the hub surface and the tip surface becomes small, that is, the torsion of the blade becomes small. On the other hand, the inflow speed of the blade blade element on the hub side increases. As a result, if the head is designed so as to provide a full head in the radial direction, the load on the hub surface is reduced and the blade performance on the hub surface is improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

A front guide blade 2 is provided below the impeller 1 mounted on the rotary shaft 4 supported by a submerged bearing (not shown) of the axial flow pump, and a rear guide blade is provided above the impeller 1. A blade 3 is provided. The front guide blade 2 is fixed to the bell mouth 5 on the tip side, and the bell mouth 5 is fixed on the hub side. FIG. 2 shows the shape of the pump suction channel (cross section taken along line AA) of FIG. FIG. 3 is a developed view of a cylindrical cross section on the hub side (diameter D _g ′) in FIG. FIG. 4 is a developed view of a cylindrical cross section on the tip side (diameter D _g ″) in FIG.

Between the hub cylindrical section 2a (diameter D _gh ) and the cylindrical section 2c (diameter D _g ) of the front guide blade 2, a warped airfoil is applied as shown in FIGS. A rotation in a direction opposite to that of the rotation of 1 is obtained. Further, between the cylindrical section 2c and the tip-side cylindrical section 2b, a non-warped airfoil is set parallel to the rotation axis (inflow direction) (zero angle of attack) as shown in FIGS. The blade shape of the front guide blade 2 is such that the warp and the turning angle gradually decrease from the hub cylindrical section 2a to the cylindrical section 2c, and the cylindrical section 2c
Are set so that both become zero.

FIGS. 3 (b) and 4 (b) show the speed triangle of the impeller 1 when the flow flows from below the pump in such an axial flow pump. As shown in FIG. 3 (b), the flow axially flowing into the front guide blade 2 in the hub-side cylindrical cross section is rotated by the front guide blade 2 at the guide blade outlet, that is, at the impeller inlet. And a velocity vector C ₁ having a turning component C _u1 in the opposite direction. Therefore, it flows into the impeller 1 at the relative speed W ₁ . The impeller 1 decelerates from W ₁ to W ₂ , and sends the absolute speed C to the rear guide blade 3.
Go out as _two . From the velocity triangles of FIGS. 3B and 20B, the inflow angle β ₁ of the present invention and the inflow angle β of the prior art are shown.
₁ ′ has the following relationship.

[0022]

(Equation 3)

Accordingly, the blade mounting angle β _i of the present invention is smaller than that of the conventional art, and does not become an abnormally large value even in the hub cylindrical section 2a as shown in FIG.

Further, in the present invention with regard loads vane blade element shown in equation (2), the load value of the left side for right of beta _∞ and W _∞ decreases also decreases. Therefore, the angle of attack (α) of the blade blade element can be set small, and the blade mounting angle β ₁ becomes small.

On the other hand, the cavitation performance of the pump is one of the important performances. Since the front guide blades 2 have a speed increasing cascade, the pressure at the inlet of the impeller is reduced as compared with the case where the front guide blades 2 are not provided, and cavitation is likely to occur. The cavitation coefficient K _b of the blade blade is represented by the following equation.

[0026]

(Equation 4)

[0027] The NPSH = 10 m and cavitation K _b of vane blade element obtained by Formula 4 by assuming shown in FIG. If the cavitation coefficient _Kb falls below a certain value, the performance is reduced. Therefore, from the viewpoint of anti-cavitation performance, the higher the _{Kb, the} better. In the prior art, since the cavitation coefficient on the hub side is much larger than that on the tip side, cavitation is originally unlikely to occur on the hub side. Therefore, even if the pressure is slightly reduced by the front guide vanes 2, the state of cavitation does not change as in the related art, and the tip side becomes a restricted cross section regarding the cavitation performance. Since the tip side has the same shape as that of the related art, the same cavitation performance as that of the related art can be obtained.

As described above, according to the present invention, the blade mounting angle β _i of the hub can be set small, the hub ratio required for a high specific speed ratio can be reduced, and the productivity, strength and performance of the impeller 1 can be reduced. It can be realized without bringing.

FIGS. 9 and 10 show a second embodiment. FIG.
0 is a cross-sectional view taken along the line BB of FIG. The number of the front guide blades 2 from the hub 6 to the tip is the minimum number (four in the embodiment) sufficient in strength to fix the bell mouth 5, and the other is the radial position where the warped guide blades are provided. (D _g /
The blades are provided only up to 2), and the area between the blades in the suction channel is widened to increase the permeability of impurities.

A third embodiment is shown in FIGS.
FIG. 12 is a cross-sectional view taken along line CC of FIG. In order to improve the manufacturability of the front first guide blade 2, the guide blade 2 is
And the hub 6 is joined to the front second guide blade also serving as a support of the bell mouth 5 by a bolt. The angle γ between the leading edge ridge line 2d of the first guide blade 2 and the center axis of the rotating shaft is set to 90 ° or less to prevent entanglement of impurities.

FIG. 13 and FIG. 14 show a fourth embodiment.
FIG. 14 is a cross-sectional view taken along line DD of FIG. Since the front guide blade 2 is an open type blade, the flow guided on the hub side is affected by the main flow on the side with a large diameter, and if the number of blades is small, a sufficient guide effect may not be obtained. is there.
Therefore, in such a case, in order to sufficiently obtain the guiding effect of the front guide blade 2, the cylinder 10 is provided around the entire tip of the guide blade 2.

FIG. 15 shows a fifth embodiment. In the pump provided with the movable blade impeller 1, the front guide blade 2 is a movable blade. The front guide blade 2 is transmitted to a guide blade angle driving device 11 via a link mechanism from the outside of the pump or a movable transmission mechanism 12 of hydraulic pressure, electric signal, or the like, and is set to a blade angle suitable for the blade angle of the impeller 1. It is supposed to be. With this device, the blade angle is set to the optimal one for the required operating point, and high-efficiency operation becomes possible.

FIG. 16A shows a sixth embodiment. The guide blades are such that the way of stacking the front guide blade blades in the radial direction from the hub 6 is inclined by an angle θ in the direction in which the turning is performed from the radial direction. As shown in FIG. 16 (b), a centrifugal force acts on the fluid due to the circumferential velocity component C _u1 guided and induced by the guide blade 2, and a radial flow C _r1 is generated as a secondary flow, and loss occurs. It becomes a factor to lower the pump efficiency. The present embodiment has the function of suppressing this secondary flow, and can prevent an increase in loss.

FIGS. 17 and 18 show the seventh and eighth embodiments. This is a case where the pump suction flow path 8 is an umbrella-shaped flow path and flows directly into the pump from the suction flow path without the pump pit and the bell mouth. FIG. 17 shows a case where the present invention is applied to the front guide blade 2, and FIG. 18 shows a case where the front guide blade 2 having a low height is provided on the suction cone.

[0035]

According to the present invention, the relative flow velocity on the hub side of the axial impeller can be increased, the angle of inflow of the relative velocity to the impeller blade element is reduced, and the lift coefficient of the blade element is set small. The angle of attack can be reduced because it can be done, and the mounting angle of the impeller blade (the angle between the circumferential direction and the chord) can be reduced, so the difference between the mounting angle of the blade on the hub side section and the blade mounting angle on the tip section is set small. The twist of the blade between the hub and the tip is reduced, so that the manufacture of the blade is facilitated and the strength of the blade is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

3 (a) and 3 (b) are a development view of a hub-side cylindrical cross section (diameter D _g ′) of FIG. 1 and a view showing a speed triangle of an impeller.

FIG. 4 is a development view of a tip-side cylindrical cross section (diameter D _g ″) of FIG. 1 and a diagram showing a speed triangle of an impeller.

FIG. 5 is a diagram showing a relationship between a radius of an impeller and a load of a blade blade element.

FIG. 6 is a diagram showing the relationship between the angle of attack of the blade blade and the lift ratio.

FIG. 7 is a diagram showing the relationship between the radius of an impeller and the mounting angle of a blade element.

FIG. 8 is a diagram showing a relationship between a radius of an impeller and a cavitation coefficient of a blade blade element.

FIG. 9 is a longitudinal sectional view showing a second embodiment.

FIG. 10 is a transverse sectional view taken along the line BB of FIG. 9;

FIG. 11 is a longitudinal sectional view showing a third embodiment.

FIG. 12 is a transverse sectional view taken along line CC of FIG. 11;

FIG. 13 is a longitudinal sectional view showing a fourth embodiment.

FIG. 14 is a transverse sectional view taken along line DD of FIG. 13;

FIG. 15 is a longitudinal sectional view showing a fifth embodiment.

16A and 16B are an explanatory view and a detailed view showing a sixth embodiment.

FIG. 17 is a longitudinal sectional view showing a seventh embodiment.

FIG. 18 is a longitudinal sectional view showing an eighth embodiment.

19A and 19B are a configuration diagram of a conventional blade and a speed triangular diagram.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Impeller, 2 ... Front guide blade, 3 ... Rear guide blade, 4
... Shaft, 5 ... Bell mouth, 6 ... Hub, 7 ... Discharge pipe, 8 ... Umbrella-shaped suction flow path.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Kunio Takada 603, Kandamachi, Tsuchiura-shi, Ibaraki Prefecture Inside the Tsuchiura Plant, Hitachi, Ltd. (72) Kenji Otani 603, Kandamachi-cho, Tsuchiura-shi, Ibaraki Hitachi, Ltd. (56) References JP-A-3-67097 (JP, A) JP-A-57-69999 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F04D 29 / 40-29 / 56

Claims (5)

(57) [Claims] 1. An impeller having a front guide blade to which a hub is fixed, a blade row satisfying a speed triangle determined from a design theoretical head using a velocity of a flow flowing out of the front guide blade as an inflow velocity vector, and a rear guide. In the axial-flow type fluid machine provided with the blades, the front guide blades may be configured such that a blade thickness center line is directed downstream in a cylindrical section on a hub side, and is inclined in a direction opposite to a rotation direction of the impeller with respect to a rotation axis direction. In the element and the cylindrical section on the tip side, the blade thickness center line connects and forms the blade blade element parallel to the rotation axis direction, and the front guide blade is such that the blade blade element extends the entire length of the flow path in the radial direction. An axial flow type fluid machine comprising: a member extending to a middle of a flow path. 2. An axial flow type fluid according to claim 1, wherein said front guide vane is provided with a cylindrical ring on the outer periphery of the tip, although the vane blade element extends to the middle of the flow path in the radial direction. machine. 3. An axial flow type fluid machine according to claim 1, wherein said impeller and said front guide blade are movable blades. 4. An impeller having a front guide blade to which a hub is fixed, a cascade satisfying a speed triangle determined from a design theoretical head using a velocity of a flow flowing out of the front guide blade as an inflow velocity vector and a rear wheel. In the axial-flow type fluid machine provided with guide vanes, the front guide vanes are blades in which a blade thickness center line in a cylindrical cross section on the hub side is inclined toward a downstream side with respect to a rotation axis direction in a direction opposite to a rotation direction of the impeller. The blade element is formed by connecting the blade thickness center line of the tip-side cylindrical cross section with the blade blade element parallel to the rotation axis direction, and the guide blade is such that the blade blade element extends the entire length of the flow path in the radial direction. An axial flow type fluid machine which is configured so as to extend to the middle of the flow path, and the one extending over the entire length of the flow path is arranged more upstream of the flow path than the one extending to the middle of the flow path. 5. An apparatus according to claim 4, wherein an angle between a leading edge of the meridian plane of the front guide vane up to the middle of the flow path and a ridge line and an impeller rotation axis is 90 degrees or less. An axial flow type fluid machine characterized by the following.