CN210461164U

CN210461164U - Mixed flow pump

Info

Publication number: CN210461164U
Application number: CN201921161540.2U
Authority: CN
Inventors: 戴韬; 杨孙圣
Original assignee: Fluid Engineering Equipment Technology Of Jiangsu University Zhenjiang; Jiangsu University
Current assignee: Fluid Engineering Equipment Technology Of Jiangsu University Zhenjiang; Jiangsu University
Priority date: 2019-07-23
Filing date: 2019-07-23
Publication date: 2020-05-05
Anticipated expiration: 2029-07-23

Abstract

The utility model discloses a mixed flow pump, which comprises a volute and an impeller; an outlet of the volute is communicated with an inlet of the impeller; the volute is obliquely arranged relative to the center line of the rotating shaft of the impeller, so that the center line of the outlet of the volute has a flow cone angle theta relative to the center line of the rotating shaft of the impeller. The inclined arrangement of the volute outlet can play a role in improving the inflow of the mixed flow pump as a turbine impeller inlet, is beneficial to reducing the hydraulic loss and improving the performance of the mixed flow pump as a turbine unit. The utility model discloses but wide application in large-traffic, the miniature hydroelectric station of low head.

Description

Mixed flow pump

Technical Field

The utility model relates to a liquid pressure complementary energy is retrieved and small-size hydroelectric power generation field, in particular to is applied to and makes the mixed flow pump of turbine among large-traffic, low-head hydroelectric power station.

Background

The liquid pressure energy is a renewable clean energy source. With the continuous rising of the energy demand and the continuous enhancement of the energy-saving consciousness of the social development, the development and the utilization of the dispersed low-power liquid pressure energy have important significance for building a resource-saving environment-friendly society. The mode of adopting pump reversal to retrieve liquid excess pressure as the turbine has advantages such as small, simple structure, operation maintenance convenience, all has wide application in energy-conserving fields such as industrial process, little water and electricity.

Different from the conventional francis turbine, the francis turbine is not provided with a guide vane structure due to the radial size limitation, namely, high-pressure incoming flow directly enters an impeller flow channel after flowing out of a volute, so that the structure and the form of the outlet of the volute play a key role in the internal flow of the impeller. The ideal volute outlet design can lead the outflow to the impeller inlet reasonably, and reduce the hydraulic loss of the impeller flow channel and the secondary flow vortex phenomenon. At present, in a volute matched with a mixed flow pump as a turbine impeller, the outlet design of the volute mostly refers to a volute outlet mode of taking a centrifugal pump as a turbine, namely, the volute outlet is radial, and the included angle between the center line of the volute outlet and the axis of a rotating shaft is 90 degrees.

Because the mixed flow pump has a certain inclination angle as the inlet of the turbine impeller, after the fluid flows out from the outlet of the volute in the radial direction, the fluid enters the impeller flow channel through the change of the direction, certain loss is generated in the gap area, and the whole efficiency of the unit is influenced. Meanwhile, the gap between the outlet of the volute adopting the radial outflow form and the edge of the rear cover plate of the mixed-flow impeller is larger, so that the flow passing area of the gap flow field of the rear pump cavity and the main flow field is larger, and the impact loss of the gap flow field of the rear pump cavity to the main flow field is further increased. Therefore, the prior mixed-flow pump is used as a turbine volute structure, and the service efficiency of the unit is influenced to a certain extent.

SUMMERY OF THE UTILITY MODEL

To above problem, the utility model provides a spiral case export liquid stream has mixed flow pump of flow cone angle theta to the adaptation has inclination's impeller, improves impeller inflow condition, reduces impeller import impact loss, with promotion unit operating performance.

The utility model provides a mixed flow pump, which comprises a volute and an impeller; an outlet of the volute is communicated with an inlet of the impeller; the volute is obliquely arranged relative to the center line of the rotating shaft of the impeller, so that the center line of the outlet of the volute has a flow cone angle theta relative to the center line of the rotating shaft of the impeller.

Furthermore, the plane where the outlet end of the volute is located is parallel to the plane where the inlet end of the impeller is located.

Further, the center line of the volute outlet is coincident with the center line of the impeller inlet.

Further, the distance between the outlet end of the volute and the inlet end of the impeller is 3% -8% of the average outer diameter of the impeller.

Further, the flow cone angle θ is an acute angle.

Furthermore, the roughness Ra of the inner cavity of the volute is less than 6.3 mu m.

Further, the impeller comprises a front cover plate and a rear cover plate, and an inlet formed by the front cover plate and the rear cover plate in a surrounding mode is communicated with an outlet of the volute.

Adopt above-mentioned technical scheme, the utility model discloses following beneficial effect has:

1. the direction of the volute outlet is parallel to the impeller inlet after being inclined, and high-pressure liquid directly enters the impeller flow channel after flowing out along the normal direction of the volute outlet, so that secondary flow vortex and hydraulic loss caused by speed direction change are reduced.

2. After the outlet of the volute is inclined, the speed projection direction of the volute outflow on the axial plane is parallel to the front cover plate and the rear cover plate of the impeller, so that the rim impact loss of the front cover plate is reduced, and the flow state of the inlet area of the impeller is further improved.

3. After the outlet of the volute is inclined, the gap distance between the rear cover plate of the mixed-flow pump as a turbine impeller and the volute is reduced, the flow area of the gap of the rear pump cavity is reduced, and the impact loss of the gap flow field of the rear pump cavity to the inlet of the impeller is reduced. The utility model discloses but wide application in large-traffic, the miniature hydroelectric station of low head.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a schematic structural view of a mixed flow pump according to an embodiment of the present invention;

FIG. 2 is a prior art radial outlet volute flow section streamline distribution diagram;

FIG. 3 is a flow line distribution diagram of the flow cross section of the volute of the mixed flow pump of the present invention;

FIG. 4 is a schematic diagram comparing various performances of the mixed flow pump as a turbine with the conventional radial outlet volute case;

fig. 5 is a schematic view of a three-dimensional water body and a flowing direction in the mixed flow pump of the present invention.

The following is a supplementary description of the drawings:

1-a volute; 101-volute outlet; 102-a volute inner cavity; 2-an impeller; 201-front cover plate; 202-a back cover plate; 203-impeller inlet; 3-flow cone angle theta.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the embodiments described are only some embodiments of the invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with at least one implementation of the invention is included. In the description of the present invention, it is to be understood that the terms "upper", "lower", "top", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or otherwise described herein.

Example (b):

as shown in fig. 1, the embodiment of the present invention provides a mixed flow pump, which includes a volute 1 and an impeller 2; the outlet 101 of the volute is in communication with the inlet 203 of the impeller;

the volute 1 is placed obliquely relative to the center line of the impeller 2, so that the center line of the volute outlet 101 has a flow cone angle theta 3 relative to the center line of the impeller 2.

It can be understood that in the volute matched with the mixed-flow pump as the turbine impeller in the prior art, the outlet design of the volute mostly refers to the volute outlet mode of the centrifugal pump as the turbine, namely, the volute outlet is radial, and the included angle between the center line of the specific volute outlet and the axis of the rotating shaft is 90 degrees. And the utility model discloses in can change the spiral case 1 through having set up the cone angle theta 3 that flows and flow direction that outflows to according to the 2 circumstances of actual impeller, get corresponding cone angle theta 3 value that flows on the one hand, can adapt to the impeller 2 of different imports, on the other hand also can reduce because speed direction changes the secondary flow vortex and the hydraulic loss that arouses.

In some possible embodiments, the plane of the outlet end of the volute and the plane of the inlet end of the impeller are parallel to each other, so that the fluid does not change its direction before entering the flow channel of the impeller 2, and the flow area of the gap of the rear pump cavity and the main flow area can be effectively reduced. Therefore, the mixed flow pump is used as the internal flow field of the turbine and does not generate direction mutation along the streamline flow, so as to reduce the energy loss generated by water flow impact and vortex. It can be understood that if the volute outlet 101 is not parallel to the impeller inlet 203 after being inclined, and a certain included angle still exists, the flow direction of the outlet flow of the volute 1 still needs to be changed before the outlet flow enters the impeller 2, and the direct inflow effect cannot be realized, so that energy loss is caused.

In some possible embodiments, a centerline of the volute outlet 101 coincides with a centerline of the impeller inlet 203.

Specifically, the relative position of the impeller 2 and the volute 1 can be adjusted by changing the length of the rotating shaft of the mixed-flow pump, so that the outflow of the volute 1 can be ensured to uniformly flow into the flow channel of the impeller 2, and the phenomenon that the center line of the inclined volute outlet 101 is not coincident with the center line of the impeller inlet 203, so that part of the fluid still needs to be subjected to flow direction conversion after flowing out of the volute 1, and the energy loss caused by the fluid is reduced.

In some possible embodiments, the spacing between the volute outlet end and the impeller inlet end is between 3% and 8% of the average outer diameter of the impeller 2.

In some possible embodiments, the flow cone angle θ 3 is acute, i.e., the angle between the centerline of the volute outlet 101 and the centerline of the impeller 2 is acute.

It is understood that the flow cone angle θ 3 or the included angle is an acute angle between the projection of the speed of the liquid outflow from the volute 1 on the axial plane of the impeller 2 and the rotation axis.

Further, the flow cone angle θ 3 may be specifically set according to an actual situation, for example, set according to an inlet direction of the impeller 2.

In some possible embodiments, the roughness Ra of the inner cavity 102 of the volute is < 6.3 μm.

In some possible embodiments, the impeller 2 includes a front cover plate 201 and a rear cover plate 202, and an inlet formed by the front cover plate 201 and the rear cover plate 202 is communicated with the outlet 101 of the volute.

The volute is the first component of the mixed flow pump as a turbine, and the volute 1 provided by the embodiment of the invention can guide the water flow to the impeller inlet 203 with minimum hydraulic loss. In addition, in order to improve the work efficiency of the impeller and ensure the operation stability of the unit, the water flow before entering the impeller is required to have a certain speed circulation. Different from the conventional water turbine, in the mixed flow pump turbine, as the guide vane structure does not exist, the high-pressure fluid directly enters the impeller flow channel after flowing out of the volute, and the outlet form of the volute determines the inflow state of the impeller to a great extent. In addition, different from a centrifugal pump as a turbine impeller, an inclined angle exists at the edge of an impeller inlet 203 of a mixed flow pump as a turbine, and under the condition that a traditional radial outlet volute 1 is adopted, after fluid in the mixed flow pump as a turbine flows out of the volute 1, the flowing speed and the flowing size are changed to enter a runner of an impeller 2, and the running efficiency of the mixed flow pump as the turbine is reduced along with energy loss in the speed change process. The embodiment of the utility model provides an incline spiral case export 101 and set up, make spiral case export 101 locate to be parallel with impeller import 203, spiral case export 101 central line coincides with impeller import 203 central line simultaneously, thus make the medium flow out from spiral case export 101 and directly get into 2 runners of impeller; in addition, the minimum diameter of the base circle of the volute outlet 101 is reduced after the volute outlet 101 is inclined, the flow cross-sectional area of a pump cavity and a main flow area after the mixed flow pump is used as a turbine is reduced, and the impact loss of the main flow area is reduced.

Therefore, the efficiency of the mixed-flow pump as a turbine is obviously superior to that of the traditional radial outlet volute, and the CFD flow simulation calculation is combined for explanation. Figure 2 shows a prior art volute flow cross-section streamline distribution diagram. Figure 3 shows the flow distribution of the flow cross section of the volute 1 of the mixed flow pump. As can be seen from fig. 2 and 3, the mixed flow pump using the radial outlet volute has a secondary flow vortex at the rim of the front cover plate and the rim of the rear cover plate, which is more obvious. As volute outlet 101 is tilted, the swirl at impeller inlet 203 is significantly reduced. The reason is that the mixed flow pump has a certain inclination angle at the side of the inlet 203 of the turbine impeller, the front cover plate of the impeller is firstly contacted with high-pressure incoming flow to start acting on the impeller in advance, and compared with liquid entering the runner of the impeller later, the pressure is reduced, so that transverse pressure difference vertical to the incoming flow is formed near the rim of the front cover plate, and secondary backflow vortex pointing to the front cover plate is formed. In addition, a certain incoming flow impact angle exists between the front cover plate of the impeller of the mixed-flow pump serving as the turbine of the radial outlet volute and the fluid, the fluid starts to have a stripping tendency after bypassing the rim of the front cover plate and generates a static pressure difference delta p to form a local low-pressure area, and the area of the low-pressure area is related to the flow rate. The differential pressure between the low pressure zone and the surrounding fluid acts on the main flow on the side in a normal direction, and centripetal acceleration is formed, namely, the fluid bypasses the rim of the front cover plate to form corner zone separation vortex. Meanwhile, because the distance between the rim of the rear cover plate of the impeller and the outlet of the volute is relatively large, the flow area between the rear pump cavity and the main flow area is large, the influence of outflow of the rear pump cavity is formed at the rim of the rear cover plate, and secondary flow superposed on the main flow is also caused. Therefore, compare with the mixed flow pump of traditional radial spiral case export and do the turbine, the mixed flow pump, its spiral case 1 flows out the fluid distribution that gets into impeller 2 even, does not have obvious swirl and produces, is favorable to reducing hydraulic loss.

Further, figure 4 shows the utility model discloses make the external characteristic contrast condition of turbine with the mixed flow pump of radial spiral case export, it is visible, the flood peak, the axle power and the efficiency of mixed flow pump all have obvious promotion.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A mixed flow pump, characterized in that it comprises a volute (1) and an impeller (2); the outlet (101) of the volute communicates with the inlet (203) of the impeller;

the volute (1) is obliquely arranged relative to the center line of the rotating shaft of the impeller (2) so that the center line of the volute outlet (101) has a flow cone angle theta (3) relative to the center line of the rotating shaft of the impeller (2).

2. A mixed flow pump according to claim 1, wherein the plane of the outlet end of the volute and the plane of the inlet end of the impeller are parallel to each other.

3. A mixed flow pump according to claim 1, wherein the centre line of the volute outlet (101) coincides with the centre line of the impeller inlet (203).

4. A mixed flow pump according to any of claims 1 to 3, wherein the spacing between the outlet end of the volute and the inlet end of the impeller is between 3% and 8% of the average outer diameter of the impeller.

5. A mixed flow pump according to claim 1, wherein the flow cone angle θ (3) is acute.

6. A mixed flow pump according to claim 1, wherein the roughness Ra of the inner chamber (102) of the volute is < 6.3 μm.

7. A mixed flow pump according to claim 1, wherein the impeller (2) comprises a front cover plate (201) and a rear cover plate (202), and an inlet formed by the front cover plate (201) and the rear cover plate (202) is communicated with the outlet (101) of the volute.