JPS6073094A - Variable vane mixed flow pump - Google Patents

Abstract

PURPOSE:To improve suction performance, pump efficiency while to reduce hydraulic loss by employing a rotary face having an arch the center of which is in the downstream of vane turning shaft in a face containing the rotary axis as a bus line on the surface of hab while enlarging the width of vane flow path at the vane inlet. CONSTITUTION:The surface of hab 3 is formed into a rotari face containing a conical face having an arch or similar curve the center of which is in the downstream of vane turning axis (l) in the face containing the rotary axis as the bus line. Consequently the height of vane at the inlet 4 of vane 2 is made higher than that at the outlet 5 to widen the flow path of vane 2 at the inlet. Since the flow-in speed to the impeller 1 decreases, it causes no cavitation thus to improve the suction performance while the increasing rate of flow path area from the inlet toward the outlet is reduced. Consequently, the flow in the impeller 1 will never decrease abruptly to reduce the hydraulic loss in the impeller 1 resulting in improvement of pump efficiency.

Description

[Detailed description of the invention] This invention relates to a planar movable blade mixed flow pump.

Conventionally, in the impeller of a movable blade mixed flow pump, as shown in FIG. 2a and hub 3
The surface of has been made into a spherical surface of radius t and Rh with a common center O on the axis of rotation m.

Therefore, the height of the blade 2 is exactly the same from the blade inlet l to the blade outlet, and accordingly, the blade flow path area is
Rotation +! ]It is small in the blade close to the center, and the blade exit is far from the rotation axis! It is increasing significantly towards.

As mentioned above, since the flow path area of the blade inlet is significantly narrowed compared to the blade outlet, the speed of flow into the impeller increases, cavitation is less likely to occur, and the suction performance is significantly reduced.h. Ru. (7) As the flow path area increases significantly from the impeller inlet to the impeller outlet, the flow inside the impeller rapidly decelerates, causing hydraulic loss inside the impeller and reducing pump efficiency. Furthermore, in movable blade mixed flow impellers, the hub ratio (hub radius/blade outer radius) is increased in order to lower the cut-off III power ratio, so as mentioned above, the blade outer circumferential surface and the hub If the surfaces were concentric spherical surfaces, there was a drawback that the rate of increase in the area of the flow path increased from the inlet to the outlet of the blade, resulting in further deterioration of suction performance.

In order to eliminate the above-mentioned drawbacks, the present inventor first discovered that the center of the spherical surface of the spherical hub was shifted rearward on the axis of rotation from the center of the spherical surface of the outer periphery of the spherical blade when viewed in the flow direction. Special application for a movable vane mixed flow pump featuring the following characteristics:
The application was filed as No. 2GA77.

By the way, in this case, the width of the impeller inlet flow path (the height of the blades at the inlet) can be widened, so it is possible to achieve high pump efficiency, good suction performance, and a low shut-off shaft power ratio. In the flow path from the inlet to the exit of the blade, the center of the hub's spherical surface must lie on the axis of rotation, which limits the shape of the hub surface. There was a risk that there would be restrictions on designing freely the rate of change in area.

It is an object of the present invention to eliminate the drawbacks of the conventional ones as described above, to provide high pump efficiency, good suction performance, low shut-off shaft power ratio, and a flow path from the inlet to the outlet of the impeller. To provide a movable vane mixed flow pump in which the rate of change in area can be designed relatively freely.

In order to achieve this object, the present invention provides a rotating surface whose generating line is a circular arc or similar curve having its center in the area 9 downstream of the blade rotation axis, excluding the area on the rotation a line, within a plane including the rotation axis. (including a conical surface) is characterized by forming a hub surface.

Embodiments of the present invention will be described below with reference to FIG. 2.

FIG. 1 is an axial cross-sectional view of a movable blade mixed flow pump showing an embodiment of the present invention, in which a boss 3 of an impeller has blades a2 at an angle of blade angle about the rotation axis l. The blade is attached so that it can be adjusted freely.In order to make sure of this, the outer circumferential surface of the blade is centered at point 0 on the rotation axis m (the intersection of the rotation axis and the rotation axis m). A spherical surface with a radius of On the other hand, the surface of the boss 3 is formed as a rotating surface (including a conical surface) whose -fE: line is a circular arc or similar curved line with the center Qa downstream of the blade rotation axis t in a plane that includes the rotational axis. ing.

Therefore, the height of the blade at the entrance of the blade is equal to the height of the blade at the exit!
Wings of size &! The tube is formed with a large parting. In addition, since the blade angle of the blade is adjusted around the rotation axis t passing through point 0, the inner circumferential surface (root) of the blade and the hub surface 3 are
It does not fit tightly like the conventional one (Fig. 1), and therefore,
The blade inlet hub end 2b is notched in advance so that it does not hit the hub surface when the blade angle is reduced (that is, the blade is rolled closer to the direction of rotation). At this time, a slight gap is formed between the hub end of the blade outlet and the hub surface, but this has almost no effect on the performance of the pump. In the figure, t is a bell mouth forming the inlet of the pump casing, 7 is a guide casing, t is a discharge f, 71 is a drive shaft, and IO is a tension rod that reciprocates to change the blade angle.

Since this embodiment has the above-mentioned configuration, when the impeller rotates due to the rotation of the drive shaft r, the liquid is sucked in through the blade 2 and the guide casing 7 is energized by the blades 2. The first . Ru. The groove blade angle is changed by reciprocating the tension rod 10 up and down.
There isn't.

However, in the present invention, which is different from the conventional one, the rotating surface (conical ), the hub surface 3 is
Since it is formed, I! ? As shown in I, the blade quality of the blade type 1'' is larger than the blade height at the blade outlet j, and the blade flow path width is correspondingly wider at the blade inlet.

In this way, the flow path width (blade height) of the impeller population is increased while the impeller outlet dimensions remain approximately the same, and the inflow speed into the impeller is reduced, so there is no risk of cavitation occurring. The suction performance can be improved, and the rate of increase in the flow path area from the impeller inlet to the impeller outlet is also smaller, so the flow inside the impeller is much better than that of the conventional impeller shown in Figure 1. There is no rapid deceleration, thus reducing hydraulic losses in the impeller and increasing pump efficiency.

Moreover, since the center of rotation of the hub surface exists in any of a wide area within the plane including the rotation axis, excluding the rotary axis on the downstream side of the rotary rotation of the impeller, the shape of the hub surface is Compared to the previous application, it can be selected relatively freely, so the rate of change in the flow path area from the inlet to the outlet of the blade can be set as follows:
It can be selected relatively freely depending on various conditions given to the pump. Therefore, the improvement in suction performance and pump performance as described above is further promoted.

Furthermore, in this type of movable blade mixed flow pump, the hub ratio is increased in order to lower the shut-off shaft power ratio, but in the present invention, the impeller can be adjusted without changing the relatively large hub ratio. Since the width of the inlet flow path (the height of the blades at the inlet) can be increased, the above-mentioned drawbacks of the conventional low cut-off shaft power ratio as shown in FIG. 1 can be eliminated.

Since the present invention has the above-mentioned (14) structure, a movable vane mixed flow pump with high pump efficiency, good suction performance, and low shut-off shaft power ratio can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an axial sectional view of a conventional movable vane mixed flow pump, and FIG. 2 is an axial sectional view of a movable vane mixed flow pump showing an embodiment of the present invention. ／...impeller, ko...blade, m...blade outer circumference, 3
...Hub, l...Blade inlet,! ...Blade outlet, 0
...The center of the spherical surface of the outer circumference of the blade, Oa...), the center of the spherical surface.

Claims (1)

[Claims] / Movable blade diagonal flow 71 with a spherical blade outer peripheral surface?
In a pump, as a rotating surface (including a conical surface) whose generating line is an arc or similar curve having a center in the area including the rotating axis, excluding the area on the downstream side of the rotating axis of the blade rotation axis,
A movable vane mixed flow pump characterized by forming a hub surface.