Closed low-specific-speed impeller

Abstract

The invention relates to a closed low-specific-speed impeller. The principle of the closed low-specific-speed impeller is that a second blade group is additionally arranged on an outer ring of a blade group of a common closed impeller; when the number of the blades of the blade set is infinite, and the blades have enough length and can completely limit relative vortexes in a flow channel, the total amount of the relative vortexes of fluid in the moving process tends to be infinitely small, and the vortex correction coefficient of the impeller tends to be closer to a limit value; a series of specific technical means are combined, and the closed low-specific-speed impeller with the vortex correction coefficient far exceeding the conventional numerical value and the remarkable synergistic, energy-saving and low-noise characteristics can be achieved.

Description

Technical Field

[0001] The invention belongs to the field of centrifugal pumps and fans, and relates to a closed low specific speed impeller. Technical Background

[0002] The impellers of widely used centrifugal pumps and fans usually adopt a closed low-speed specific structure with a specific speed between 30 and 80. When the equipment is working, due to the loss of relative vortex between the blades with the characteristics of gradual opening, its efficiency decreases with the decrease of specific speed. Generally, the vortex correction coefficient of low-speed specific impellers, that is, the ratio of their actual head to theoretical head, is usually at the lower limit of 78-85%, which leads to problems of insufficient efficiency, noise and excessive heat generation. Summary of the invention

[0003] In response to the existing technical problems, the present invention relates to a closed low specific speed impeller, the principle of which is: a second blade group is added to the outer ring of the blade group of an ordinary closed low specific speed impeller; when the number of blades of the second blade group is infinite and the blades have a sufficient length to completely confine the relative vortex in the flow channel, the total amount of relative vortex of the fluid during movement approaches to infinitesimal, and the vortex correction coefficient of the impeller also approaches the limit value; the above core structure is combined with a series of technical means to achieve a closed low specific speed impeller with a vortex correction coefficient that breaks through conventional values ​​and has significant efficiency improvement, energy saving and low noise characteristics.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A closed low specific speed impeller, whose structure is mainly composed of an impeller rear disk, a first blade group, a second blade group and an impeller front disk, and is characterized in that: the first blade group and the second blade group are concentrically arranged double annular array structures; the first blade group is located in the inner circle, and is composed of a small number of long blades, and the ratio of the outlet diameter to the inlet diameter of its flow channel is greater than 2; the second blade group is located in the outer circle, and is composed of a large number of short blades, and the ratio of the radius of the outlet to the inlet of its flow channel is greater than 1.15, and the length of its flow channel is greater than the average width; the first blade group and the second blade group together constitute a low specific speed blade group, and the ratio of the diameter of the outlet to the inlet of its flow channel is greater than 2.3; the impeller rear disk and the impeller front disk are both dish-shaped structures, and together with the first blade group and the second blade group, they constitute a dish-shaped closed low specific speed impeller; the effective passage area of ​​the flow channel inlet of the first blade group of the closed low specific speed impeller is equal to the effective passage area of ​​the flow channel outlet of the second blade group.

[0006] Preferably, the effective passage areas of the flow channel inlet of the first blade group and the flow channel inlet and flow channel outlet of the second blade group of the closed low specific speed impeller are equal.

[0007] Preferably: the first blade group and the second blade group are jointly arranged on the impeller rear disk; mounting columns and mounting holes are respectively arranged in a circular array at corresponding positions on the impeller rear disk and the impeller front disk, and are fixed by fixing parts to form a complete closed low specific speed impeller.

[0008] Preferably, the ratio of the number of long blades of the first blade group to the number of mounting posts is an integer; and the mounting posts are respectively arranged on the center lines of the long blades of the first blade group.

[0009] Preferably, the ratio of the number of blades of the second blade group to that of the first blade group is exactly an integer, and the outlet ends of all the long blades of the first blade group are connected to the inlet ends of the short blades of the second blade group.

[0010] Working principle:

[0011] When the impeller described in this case rotates at high speed: the motion trajectory of the first blade group forms a first centrifugal zone in the inner circle, and the motion trajectory of the second blade group forms a second centrifugal zone in the outer circle; in the second centrifugal zone, the relative vortex generated by the interaction between the fluid and the high-pressure fluid outside the impeller during the centrifugal motion is completely confined to each small flow channel; the difference in centrifugal speed between the fluid at the outlet of the second centrifugal zone and the inlet of the first centrifugal zone forms an inner cavity in a negative pressure state; the normal pressure fluid at the inlet is sucked in and accelerated into the flow channel of the first centrifugal zone by the negative pressure, and then the first blade group and the second blade group complete the centrifugal acceleration respectively, and finally ejected into the high-pressure zone outside the impeller at the outlet of the flow channel of the second centrifugal zone with maximum energy. When the impeller described in this case rotates at high speed, the fluid motion has the following two major characteristics:

[0012] 1. In the first centrifugal zone, the movement of the fluid can be understood as: unidirectional centrifugal movement without relative vortex, which is close to the ideal condition of lossless fluid movement preset in the fluid model described by the Euler equation.

[0013] 2. In the second centrifugal zone, the movement of the fluid can be understood as centrifugal movement with relative vortex. The characteristic is that there are a large number of relative vortices, which are completely confined in each small flow channel. The total amount of relative vortex is inversely proportional to the number of flow channels in the second blade group. That is, when the number of blades is infinite, the fluid in the flow channel is a centrifugal movement with approximately no relative vortex. This is close to the ideal condition of infinite blades and lossless fluid movement in the fluid model described by the Euler equation.

[0014] For example: Under the same specific speed condition, if the vortex correction coefficient of an ordinary low specific speed impeller is 80%, and the number of flow channels of the second blade group set in this case is five times that of the former, it can be calculated according to the similarity law that the total amount of relative vortex in this case is only 20% of that of the former, and the theoretical maximum value of its vortex correction coefficient is 96%.

[0015] After empirical verification, the structure of this case objectively decomposes and weakens the relative vortex generated by the fluid in the low specific speed impeller movement, and obtains the following beneficial effects:

[0016] 1. This case breaks through the limitation of eddy current correction coefficient of conventional impellers, which is only 78-85%. Even in the case of large size and extremely low specific speed, the impeller of this case can still achieve an extraordinary eddy current correction coefficient.

[0017] 2. Under the condition of the same specific speed, this case can output higher and more stable head and flow rate compared with ordinary impellers. In the actual measurement of extreme conditions, the head and flow rate of the equipment can be increased by more than 15%.

[0018] 3. Under the same head and flow rate, the noise and heat generation of the fluid during operation are significantly reduced compared with ordinary impellers. In actual measurements under extreme conditions, the noise and heat generation of the fluid can be reduced by more than 15%.

[0019] 4. Under the same head and flow rate, this case has better energy-saving characteristics compared with ordinary impellers. In actual measurements under extreme conditions, it can save more than 15% of energy.

[0020] 5. When the head, flow rate and speed of the equipment remain unchanged, the outer diameter required in this case is smaller, which is of great significance to the miniaturization of the rated equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of the low specific speed blade group of the present invention.

[0022] Figure 2 It is a schematic plan view of the blade assembly of the first embodiment.

[0023] Figure 3 It is a front cross-sectional schematic diagram of a second embodiment of the present invention.

[0024] Figure 4 It is a schematic diagram of the reverse appearance of the second embodiment of the present invention.

[0025] In the figure: 1. Long blade; 2. First centrifugal zone; 3. Short blade; 4. Second centrifugal zone; 5. Shaft hole; 6. Positioning column; 7. Fixing piece; 8. Impeller front disc; 9. Impeller rear disc; 10. Positioning hole DETAILED DESCRIPTION

[0026] The following is a brief description of the specific embodiment of the present invention.

[0027] like Figure 1 The figure is a schematic diagram of the structure of the low specific speed blade group of the present invention. Among them, the six long blades 1 constitute the first blade group arranged in the inner ring, the ratio of the outlet diameter to the inlet diameter of the flow channel is greater than 2, and the trajectory of their rotational motion constitutes the first centrifugal zone 2; the forty-nine short blades 3 constitute the second blade group arranged in the outer ring, the ratio of the outlet radius to the inlet radius of the flow channel is greater than 1.15, the length of the flow channel is greater than the average width, and the trajectory of their rotational motion constitutes the second centrifugal zone 4.

[0028] Its characteristics are: the first centrifugal area and the second centrifugal area are separated concentric ring structures; the first blade group and the second blade group together form a low specific speed blade group with a diameter ratio of the flow channel outlet to the inlet greater than 2.3.

[0029] like Figure 2 FIG. 1 is a schematic plan view of the blade assembly of the first embodiment, wherein twelve long blades 1 form a first blade assembly arranged in the inner ring, and forty-eight short blades 3 form a second blade assembly arranged in the outer ring.

[0030] Its characteristics are: the first centrifugal zone and the second centrifugal zone are adjacent concentric ring structures; six positioning columns 6 are respectively arranged on the center lines of certain long blades 1; the ratio of the number of short blades 3 to the number of long blades 1 is exactly an integer, and all long blades 1 are not connected to short blades 3.

[0031] like Figure 3 FIG. 2 is a front cross-sectional schematic diagram of a second embodiment of the present invention, wherein twelve long blades 1 and forty-eight short blades 3 together form a low specific speed blade group.

[0032] Its characteristics are: the impeller front disk 8 and the impeller rear disk 9 are both disc-shaped structures, and are respectively provided with six positioning holes 10 and positioning columns 6; the positioning columns 6 are respectively arranged on the central axis of certain long blades 1; the fixing part 7 consolidates the impeller front disk 8 and the impeller rear disk 9 into a complete closed low specific speed impeller through the positioning holes 10 and the positioning columns 6.

[0033] like Figure 4 , which is a schematic diagram of the reverse appearance of the second embodiment of the present invention. Its characteristics are: the impeller front disc 8 and the impeller rear disc 9 are both butterfly-shaped structures; when they are consolidated with the first blade group and the second blade group to form a complete closed low specific speed impeller, the effective passage area of ​​the flow channel inlet of the first blade group and the flow channel inlet and flow channel outlet of the second blade group are equal.

[0034] Supplementary explanation: The above is only an illustration and analysis of the present invention, not a definition or limitation.

Claims

1. A closed low specific speed impeller, which is mainly composed of an impeller rear disc, a first blade group, a second blade group and an impeller front disc, and is characterized by: The first blade group and the second blade group are concentrically arranged double annular array structures; the first blade group is located in the inner circle, composed of a small number of long blades, and the ratio of the outlet diameter to the inlet diameter of its flow channel is greater than 2; the second blade group is located in the outer circle, composed of a large number of short blades, the ratio of the radius of the outlet to the inlet of its flow channel is greater than 1.15, and the length of its flow channel is greater than the average width; the first blade group and the second blade group together form a low specific speed blade group, and the ratio of the diameter of the outlet to the inlet of its flow channel is greater than 2.3; the impeller rear disk and the impeller front disk are both disc-shaped structures, and together with the first blade group and the second blade group, they form a disc-shaped closed low specific speed impeller; the effective passage area of ​​the flow channel inlet of the first blade group of the closed low specific speed impeller is equal to the effective passage area of ​​the flow channel outlet of the second blade group.

2. A closed low specific speed impeller according to claim 1, characterized in that: The effective passage areas of the flow passage inlet of the first blade group and the flow passage inlet and flow passage outlet of the second blade group of the closed low specific speed impeller are equal.

3. A closed low specific speed impeller according to claim 1, characterized in that: The first blade group and the second blade group are jointly arranged on the impeller rear disk; corresponding positions on the impeller rear disk and the impeller front disk are respectively provided with mounting columns and mounting holes in a circular array, and are fixed by fixing parts to form a complete closed low specific speed impeller.

4. A closed low specific speed impeller according to claim 1, characterized in that: The ratio of the number of blades of the second blade group to that of the first blade group is exactly an integer, and the outlet ends of all the long blades of the first blade group are connected to the inlet ends of the short blades of the second blade group.

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