RU2735971C1 - Impeller of blade pump stage - Google Patents

Abstract

FIELD: pumps.

SUBSTANCE: invention relates to pump engineering, mainly to production of multi-stage electric submersible centrifugal and semi-axial pumps for oil production. Impeller of vane pump stage comprises main disc (1) with hub (2) and cover disc (3), between which there are curvilinear blades (4) forming inter-blade channels (5). Each channel (5) is made in the form of a cone-shaped diffuser having an oval cross-section, mainly an oval-ellipse-oval. Inlets into channels (5) and outlets therefrom are made in the form of quadrangles with parallel opposite sides, and end areas of channels (5), where transition occurs from quadrangular cross-section to oval shape, at inlet of channels (5), and from oval section to quadrangular, at outlet of channels (5), smoothly mate with inner area of channel (5).

EFFECT: invention is aimed at reduction of hydraulic resistance of impeller and hydraulic losses in it by 2÷5 %.

1 cl, 2 dwg

Description

Technology area

The claimed technical solution relates to pumping equipment, namely to impellers of vane multistage pumps for pumping various liquid media. It will be most effectively used when used as a part of multistage ESPs (electric submersible centrifugal pumps) for oil production.

State of the art

Multistage vane (centrifugal and semi-axial) pumps are widely used for pumping various liquids in oil production, power engineering, other industries and Zh.K.Kh. The working bodies of such pumps are pump stages, each of which consists of an impeller and a guide vane. The rotating impeller serves to transfer mechanical energy to the fluid flow. It is a main disc with a hub and a cover disc, between which the blades (blades) are located, forming inter-blade channels, through which, under the action of the blades, the pumped liquid moves. This design is called a closed impeller. The guide vane fixed in the housing serves to transfer the liquid to the impeller of the next stage of the vane pump [see. V.N. Ivanovsky, A.A. Sabirov, A.V. Degovtsev et al. "Design and research of dynamic pump stages" - M: Russian State University of Oil and Gas named after THEM. Gubkin, 124 p.].

In the main number of known analogs, the inter-blade channels of the impeller from the point of view of hydrodynamics are curved diffusers, in which the blades (blades) are curved, with a variable inclined and bent back (along the direction of rotation of the wheel). The cross-section of the inter-blade channels, perpendicular to the direction of fluid flow (or the cross-section of the channel), has the shape of a quadrangle in which the lines formed by the discs are straight and parallel, and the blades are both parallel straight and parallel curved lines [see, for example, US Patent No. 5224821 , cl. F01D 5/14, publ. 06.07.1993, Patent RU 2080490, cl. F04B 29/24, F04D 29/66 publ. May 27, 1997, Eurasian patent 000686 cl. F 04D 29/22, 7/04. publ. February 28, 2000, as well as V.N. Ivanovsky, A.A. Sabirov, A.V. Degovtsev et al. "Design and research of dynamic pump stages." - M: Russian State University of Oil and Gas named after THEM. Gubkin, 124 p.].

The closest technical solution in essence to the claimed one is the invention under Patent RU 2688873 C1 class. F04D 1/06, F04D 29/22, F04D 29/44, publ. 05/22/2019 This is the Stage of a centrifugal pump, consisting of at least an impeller and a guide vane, characterized in that the interscapular (intershaped) channels are circular or close to a circle in cross section; in this case, a shape is considered close to a circle in which the distance from the channel axis to the least distant point on the channel wall is at least 90% of the distance from the channel axis to the most distant point. A variant of the invention is a centrifugal pump stage according to claim 1, characterized in that each channel or part of it is located along a curve described by equations of the form:

x = a⋅t⋅cos (t ^b );

y = a⋅t⋅sin (t ^b );

where a, b, t is any real number.

The disadvantages of the technical solutions chosen as analogues and prototype are as follows:

1. The analogs considered above are impellers with inter-blade channels in the form of curved diffusers with a cross-section of channels in the form of a quadrangle with parallel opposite sides. Most often, these channels are flat diffusers, i.e. expanding in one plane (in the width of the flow channel), because they have a hydraulic resistance lower than that of diffusers that expand in two planes. The local hydraulic resistance of the sudden liquid expansion at the outlet from such diffusers is minimal.

The disadvantage of the above-described impellers is a rather high hydraulic resistance of the inter-blade channels, especially of low-capacity pumps (20-100 m ³ / day), as well as low reliability during the operation of these pumps in wells due to clogging of the channels with mechanical impurities and salt deposits from the pumped liquid. The latter is especially important when operating an ESP for oil production.

2. The technical solution chosen as a prototype differs from analogs in that the inter-blade channels have a circular or very close to circular cross-sectional shape. Due to this shape of the channels, when the fluid moves along them, the flow moves along the channel walls with fewer separations and vortices, which cause pressure losses. Those. this form provides a minimum hydraulic resistance of the inter-blade channels. Our hydrodynamic calculations carried out to adapt the prototype to the design of a real impeller (see Table 1) showed that the hydraulic resistance of channels of this shape can be 42% lower than that of analogues. In addition, clogging of the flowing round channels occurs less often than the elongated quadrangular shape (with the same cross-sectional areas of the channels).

In the design of the stage shown in the materials of the Prototype (but not reflected in the claims and description of the invention), the guide vane has a diameter much larger than the diameter of the impeller and the fluid flow from the wheel enters the inter-blade grate of the guide vane without changing direction. It changes already in the guide vane itself. But in real downhole ESPs with relatively small radial dimensions, the use of such a stage design leads to a significant decrease in its head. It seems that the author also did not take into account the high hydraulic resistance arising when the fluid enters from the wheel into the blade cascade of a circular apparatus. Therefore, the reduction in hydraulic losses in the pump stage declared in the prototype as a whole is, to put it mildly, controversial. The design of an impeller with a circular flow channel has the following disadvantages:

2.1. The use of a circular cross-section of the inter-blade channel leads to a very large increase in the local hydraulic resistance of the sudden expansion of the liquid at the outlet of the impeller. Our hydrodynamic calculations, carried out when adapting the prototype to the design of a real impeller, showed that the local hydraulic resistance of the sudden expansion of the liquid at the exit from the impeller before entering the guide vane can be 140-150 times higher than that of analogues (see Table 1 ). Therefore, the total hydraulic resistance of the impeller of the prototype will be 1.65 times greater than that of impellers of vane pumps with a classical design (diffuser design with a quadrangular shape of the channel cross-section).

2.2. Uneven, pulsating nature of fluid movement in a pump with such stages. This leads to jet rupture, flow disruption and increased cavitation in the pumps. The result is a decrease in the reliability and service life of the pumping unit, especially when the pumped liquid contains dissolved gas. The latter is always characteristic of the process of oil production from wells.

Disclosure of the proposed technical solution

The aim of the claimed invention is to improve the efficiency of the multistage vane pump by reducing the hydraulic resistance of the impeller as a whole, and hence reducing hydraulic losses when the fluid moves in it.

This goal is achieved due to the fact that the impeller of a vane pump stage, consisting of a main disk (1) with a hub (2) and a cover disk (3), between which curved blades (4) are located, forming inter-blade channels (5), along which , under the action of the blades, the pumped liquid moves (see Fig. 1) is distinguished by the following main features:

1). Each inter-blade channel is a curved diffuser, which has an oval cross-section, mainly oval-ellipse-oval:

2). The entrances to the inter-blade channels and exits from them are made in the form of quadrangles with parallel opposite sides, and the end areas of these channels, where the transition from a quadrangular section to an oval one occurs (i.e., at the inlet of the fluid flow into the inter-blade channels) and from an oval section to quadrangular (i.e. at the outlet of the fluid flow from the inter-blade channels) smoothly mate with the inner regions of these channels.

The general between the prototype and the claimed technical solution is that on the main length of the inter-blade channel its section is not quadrangular, but a closed convex curve without corners. The formation of vortices and the separation of the liquid stream from the pipes occur most intensively precisely in the corners. The presence of corners increases the hydraulic resistance of fluid flows in the channels. Smoothed, without angles, the shape of the cross-sections of the inter-blade channels allows, in principle, to lower the hydraulic resistance in comparison with channels in which the cross-sectional shape is quadrangular. Moreover, it is the circular shape of the cross-section of the inter-blade channel, inherent in the Prototype, that provides the minimum hydraulic resistance during fluid flow. But the use of such a channel shape leads to a large increase in local hydraulic resistance at the inlet, and especially at the outlet of the impeller (see Table 1).

In contrast to the Prototype, in the claimed technical solution, although along the entire length of the channel, a sectional shape smoothed without corners is formed, but it is not close to a circle, but rather an average between an ellipse strongly elongated along the semi-major axis and the parallelogram (or rectangle) that describes it. Moreover, the closer to the inlet and outlet of the channel, the closer the shape is to the parallelogram, and the ratio of the length of the semi-minor axis of the oval (ellipse) to its semi-major axis can be 0.16-0.87 (for impellers of the ETsNA5 series pumps with a nominal capacity of 20-160 m ³ / day). If we sequentially (in the direction of fluid movement) consider the sectional shapes of the diffuser channel, then the following picture is observed: parallelogram - oval gradually tapering in the diagonal plane - oval close to an ellipse - oval gradually expanding in the diagonal plane - parallelogram (see Fig. 2). The presence of transition areas is an essential feature of the proposed technical solution.

In contrast to the Prototype, in the inventive impeller, the end regions of each blade channel are close in shape to a parallelogram, namely, such a cross-sectional shape of the blade channel, inherent in analogues, provides a minimum value of local hydraulic resistances of a sudden expansion of the flow at the exit from the wheel (see Table No. 1) ...

That is, the complex design of the inter-blade channel proposed in the present invention makes it possible to combine the advantages of analogues and the Prototype in a single object and at the same time to level their disadvantages.

The most optimal variant of the technical solution is realized when the main part of the inner region of the inter-blade channels has an elliptical cross-section. This is due to the fact that with the same linear overall dimensions (equality of the major and minor axes), the oval and the ellipse have a smaller perimeter, and therefore lower hydraulic resistance. Then the impeller of the vane pump stage differs in that the inner regions of the inter-blade channels have an oval-ellipse-oval cross-sectional shape, and the lengths of the transition regions, between which the channel regions with an elliptical cross-sectional shape are located, obey the following relations:

с поперечным сечением в форме сужающегося в диагональной плоскости овала, на котором происходит плавный переход от четырехугольного входа в канал к внутреннему участку с сечением в форме эллипса, составляетlength of the transitional region of the interspace canal

with a cross-section in the form of an oval tapering in the diagonal plane, on which a smooth transition from the quadrangular entrance to the channel to the inner section with an elliptical cross-section occurs, is

(where b ₁ is the width (thickness) of the inter-blade channel at the entrance to it of the fluid flow)

с поперечным сечением в форме расширяющегося в диагональной плоскости овала, на котором происходит плавный переход от внутреннего участка с формой сечения в виде эллипса к четырехугольному выходу из канала, составляетlength to the transitional region of the interscotch canal

with a cross-section in the form of an oval expanding in the diagonal plane, on which there is a smooth transition from the inner section with an elliptical cross-section to a quadrangular outlet from the channel, is

(where b ₂ is the width (thickness) of the inter-blade channel at the outlet of the flow from the impeller)

In the general case, the width of the inter-blade channel at the inlet and outlet may differ from each other, which means that b ₁ and b _{2 are} not always equal.

The above formulas for calculating the lengths of the transition regions (1, 2) are related to the conditions for optimal ratios of the angles of narrowing and expansion for complex converging-diffuser transitions. It is known that diffusers become ineffective at expansion angles of more than 40 ° ÷ 50 °. In addition, the optimal angles of contraction in these cases are in the range of 30 ° ÷ 40 °, and expansion 7 ° ÷ 10 °. [cm. Idelchik I.E. "Handbook on hydraulic resistance / ed. M.O. Steinberg. " - 3rd edition revised. and add. - M: Mechanical Engineering, 1992 - 672 s]. It is necessary to increase the length of the region of the inter-blade channels with an elliptical section shape, if possible. It is this form that is characterized by the lowest possible hydraulic resistance. Therefore, we accept the following conditions for the proposed technical solution:

and). The angle of narrowing of the transitional region at the entrance to the inter-blade channel is within 30 ° ÷ 40 °, which is equivalent to the inequality according to formula (1);

b). The angle of expansion of the transition region at the exit from the inter-blade channel is 10 ° ÷ 40 °, which is equivalent to the inequality according to formula (2).

Description of drawings

FIG. 1 shows a longitudinal section of the impeller of a vane pump stage in its axial projection of the meridian section.

FIG. 2 shows the impeller of a vane pump stage in a radial projection with sections of the inter-blade channels - sections A-A, B-B, V-C, G-G, D-D and E-E.

А-А - radial section of the impeller at the entrance to the inter-blade channel of the pumped liquid,

B-B - radial section of the interscotch canal in the transitional region closest to the entrance, B-B - radial section of the inner region of the interspace canal,

Г-Г - radial section of the inter-blade canal in the transitional region closest to the exit,

D-D - radial section of the inter-blade channel at the outlet of the pumped liquid from it,

E-E - axial section of the impeller interspace channel in a plane not passing through the center of the channel.

The following designations are adopted in the drawings:

1 - main disk;

2 - hub;

3 - cover disc;

4 - curved blades;

5 - inter-blade canal formed by curved blades and main and cover discs;

b ₁ - width (thickness) of the inter-blade channel at the inlet of the pumped liquid flow;

b ₂ - width (thickness) of the inter-blade channel at the outlet of the flow of the pumped liquid;

- длина переходной области межлопастного канала на входе в него потока перекачиваемой жидкости;

- the length of the transition region of the inter-blade channel at the inlet of the pumped liquid flow;

- длина внутренней области межлопастного канала с поперечным сечением в форме эллипс, или овала приближающегося к эллипсу;

- the length of the inner region of the inter-blade channel with a cross-section in the form of an ellipse, or an oval approaching an ellipse;

- длина переходной области межлопастного канала на входе в него потока перекачиваемой жидкости.

is the length of the transition region of the inter-blade channel at the inlet of the pumped liquid flow.

The arrows show the direction of movement of the pumped liquid in the impeller.

The device works as follows.

During the operation of the vane multistage pump, the pumped liquid enters the annular channel of the hub (2) of the impeller rotating on the shaft. Further, after passing through the annular channel, the liquid makes a turn (as a rule, smooth by 90 °) and enters the inter-blade channels (5), which are formed by the curved blades (4) by the main disk (1) and the cover disk (3). In the inter-blade channels, under the influence of the centrifugal force transmitted by the blades, the fluid flow rate increases. The flow moves in the channel with smooth expansion and leaves the inter-blade channels of the impeller, and then through the guide vane of the vane pump stage, the flow enters the impeller of the next vane pump stage. When the fluid moves in the impeller, the centrifugal force acts on it, increasing the kinetic energy of the flow, and the hydraulic braking forces that inhibit the flow.

The hydraulic braking forces are directly proportional to the hydraulic resistance of the impeller elements through which the flow flows. Sequentially along the direction of the fluid flow, the following hydraulic resistances can be distinguished: friction resistance of the annular channel of the hub, local resistance of smooth rotation before entering the interspace channels, resistance of a sudden and gradual narrowing when the flow enters the interspace channels, resistance of a smooth diffuser expansion of the fluid when moving in the interlobate channels (it has 2 components: expansion resistance and frictional resistance), local resistances of sudden expansion at the exit of flows from the inter-blade channels.

To identify the advantages of this technical solution over analogues and the Prototype, the hydraulic resistance of the elements of the impeller of the stage of the electric submersible centrifugal pump ETsNA5-80 was calculated both in the existing version (analogue) and when the technical solutions of the Prototype and the proposed technical solution were applied in its design. The calculation used the recommended techniques, formulas, values of coefficients and parameters from tables, graphs and diagrams of a literature source [see. Idelchik I.E. "Handbook on hydraulic resistance / ed. M.O. Steinberg. " - 3rd edition revised. and additional - M .: Mechanical Engineering, 1992 - 672 s], as well as the formulas derived by the authors of this technical solution on the basis of theoretical provisions presented in the above Reference. The results of these calculations are presented in Table 1.

The data obtained showed the following:

1) The hydraulic resistance of the inter-blade channels of the impeller manufactured according to the claimed technical solution is 33-49% higher than in the impeller manufactured in accordance with the Prototype. But it is 5-13% lower than in the impeller - an analogue with the classical quadrangular cross-section of the inter-blade channels.

2) The hydraulic resistance at the outlet from the inter-blade channels of the impeller, manufactured according to the claimed technical solution, is practically the same as in the impeller - an analogue with the classical design of the inter-blade channels. But it is 145-146 times lower than that of the Prototype impeller.

3) The total hydraulic resistance and hydraulic losses of the impeller, manufactured according to the claimed technical solution, is 1.9-5.3% lower than that of analog impellers, and 41-43% lower than that of the Prototype.

Examples of technical solution implementation

Theoretical calculations carried out for the ETsNA5-80 pump (see Table 1) showed that the design of the impellers of the stages of serial multistage pumps can be easily adapted to the implementation of the proposed technical solution. For example, this is a series of mass-produced electric submersible centrifugal pumps ETsNA5-20… ETsN5-125 and ETsNA5A-25… ETsNA5A-160 with nominal capacities ranging from 20 m ³ / day to 160 m ³ / day. The most optimal technology for manufacturing such impellers is investment casting, followed by machining (grinding) on high-performance machines. The materials of the impellers produced by casting are modified gray cast iron or corrosion-resistant cast iron of the Nirezist grade. The impeller can also be made from plastic or composite materials.

Claims (8)

1. The impeller of a vane pump stage, consisting of a main disk with a hub and a cover disk, between which curvilinear blades are located, forming inter-blade channels, along which, under the action of the blades, the pumped liquid moves, characterized in that each inter-blade channel is made in the form of a curved axis diffuser, which has an oval cross-section, mainly oval-ellipse-oval; the entrances to the inter-blade channels and exits from them are made in the form of quadrangles with parallel opposite sides; and the end areas of these channels, where there is a transition from a quadrangular section to an oval one, and from an oval section to a quadrangular one, at the inlets and outlets of the inter-blade channels, smoothly mate with the inner regions of the inter-blade channels. 2. The impeller of the vane pump stage according to claim 1, characterized in that the inner regions of the inter-blade channels have an oval-ellipse-oval cross-sectional shape, and the lengths of the transition regions, between which the channel regions with an elliptical cross-sectional shape are located, obey the following relations:

Where

- the length of the transitional region of the inter-blade channel with a cross-section in the form of an oval tapering in the diagonal plane, on which there is a smooth transition from the quadrangular entrance to the channel to the inner section with an elliptical section; b ₁ - the width of the inter-blade channel at the entrance to it of the fluid flow;

- the length of the transition region of the inter-blade channel with a cross-section in the form of an oval expanding in the diagonal plane, on which there is a smooth transition from the inner section with the cross-section in the form of an ellipse to a quadrangular exit from the channel; b ₂ - the width of the inter-blade channel at the outlet of the fluid flow from the impeller.

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