Open-type vortex impeller with enhanced anti-cavitation properties for a side-channel open-vortex pump

Abstract

This utility model relates to pump engineering, specifically to open vortex pumps, and is intended to improve the anti-cavitation properties of open-type vortex impellers. It is an open-type vortex impeller for a side-channel open-type vortex pump, comprising a hub with straight radial blades. The blades have a variable thickness, increasing from the center to the rear periphery of the impeller, and have rounded end edges along the rear side, corresponding to the height of the side-channel cross-section on the side where it is located. The technical result is improved anti-cavitation properties in the interblade spaces of the open-type vortex impeller when the pump operates at operating conditions exceeding the rated value.

Description

[0001] The utility model relates to the field of pump engineering, in particular to open vortex pumps, and is intended to improve the anti-cavitation properties of open-type vortex wheels.

[0002] Cavitation on the impeller blades of an open-vortex pump, a harmful and undesirable hydrodynamic phenomenon in pump operation, occurs due to a decrease in the pressure of the liquid in the flow to the saturated vapor pressure, during which the liquid undergoes an intense transition from a liquid to a gaseous state. A decrease in pressure during pump operation above the nominal value can be caused by a sharp increase in the relative velocity of the liquid flow as it passes through the impeller blades or by flow separation from the blade surfaces, which is accompanied by an intense local pressure drop. This creates cavities in the flow, which, upon subsequent transition to the pump's high-pressure zone, collapse, causing hydraulic shock, which can damage pump components.

[0003] An open-vortex pump is a vortex pump in which the liquid is supplied to a stationary annular channel of variable, constantly increasing cross-section through an open-type impeller. The open-type impeller (see article "Operating Diagram, General Information on Vortex Pumps," URL: https: / / www.nasos-italy.ru / stat / vihrevye_nasosy) has long, straight, radial blades of constant thickness, open on both ends, and is installed with minimal clearances between the end surfaces of the blades and the pump casing.

[0004] A disadvantage of an open-type vortex pump with a side channel, in terms of the development of suction cavitation on the blades of an open-type vortex wheel, is that the straight radial blade of the wheel is poorly streamlined by the flow, the channel between the blades is short, which for wheels with a small number of blades contributes to a decrease in the flow swirl rate and an increase in its relative velocity; the channel has an expansion angle greater than 15°, which increases the likelihood of flow particles separating from the blade surfaces.

[0005] Flow separation from the vortex wheel blade surfaces occurs, including along the blade length and on the side corresponding to the location and height of the side channel cross-section, localized in this zone under the influence of the Coriolis force. Moreover, separation in this zone from the blade working surface occurs with increasing flow rate, and from the blade back surface, under any conditions.

[0006] An increase in the relative flow velocity between the blades and the separation of the flow from their surfaces causes a significant decrease in the flow pressure in the space between the blades, which can lead to cavitation.

[0007] A closed-type vortex pump impeller is known (application 2000121725: published 20.07.2002), made in the form of a disk containing a front and back side, equipped with radial blade channels on both sides, separated by straight blades, in which the blade channels are made of constant width in the tangential direction, and the separating blades are of variable thickness, increasing from the center to the periphery of the disk.

[0008] This design of the wheel reduces the intensity of flow separation from the surfaces of the blades, but does not reduce the relative flow velocity between the blades, and the presence of a disk does not allow it to be used in open-vortex pumps.

[0009] A free-vortex pump impeller is known (Author's certificate No. 1576733: published 07 / 07 / 1990), containing a hub and a disk with radial flat blades, in which the edges of the blades are rounded on their working side.

[0010] Rounding the blade's end surface is a useful design feature, as it prevents flow separation from the blade's back edge due to a sudden change in direction, disrupting laminar flow. Furthermore, as the fluid flows past the blade's sharp edge, the flow may become unstable and separate from the blade, creating a vortex shedding zone in the interblade space.

[0011] The disadvantage of this impeller is that the presence of a disk does not allow the impeller to be used in open-vortex pumps, and also that rounding the edges of the blades on the working side outside the location and height of the cross-section of the side channel will not lead to flow disruption from the edges of the rear surface of the blades due to the minimal gaps between the end surfaces of the blades and the pump casing.

[0012] The technical problem that the utility model is aimed at solving is the creation of an impeller for an open-vortex pump with a side channel.

[0013] The technical result is an increase in the anti-cavitation properties in the inter-blade spaces of an open-type vortex impeller when the pump is operating at modes exceeding the nominal one.

[0014] The technical result is achieved in that the open-type vortex impeller for an open-vortex pump with a side channel contains a hub with straight radial blades.

[0015] The peculiarity is that the blades are made of variable thickness, increasing from the center to the periphery of the wheel from the rear side, and have rounded end edges from the rear side along the length corresponding to the height of the cross-section of the side channel from the side of its location.

[0016] The essence of the utility model is explained by the drawing, where Fig. 1 shows a general view of an open-type vortex impeller with enhanced anti-cavitation properties, and Fig. 2 shows a cross-section A-A of a straight radial blade.

[0017] An open-type vortex impeller with enhanced anti-cavitation properties contains a hub 1 with straight radial blades 2.

[0018] Blades 2 are made of variable thickness, increasing from the center to the periphery of the wheel from the rear (non-working) side, due to which the inter-blade channels have a smaller expansion angle α, which helps to reduce the likelihood of flow separation from the surfaces of blades 2. Blades 2 provide a certain inclination of the inter-blade channels against the rotation of the wheel, which helps to reduce the relative flow velocity ω in the channels by changing its direction.

[0019] Blades 2 have rounded end edges on the rear side along the length and side corresponding to the location and height of the cross-section of the side channel of the pump.

[0020] The proposed open type vortex impeller works as follows.

[0021] A fluid flow enters the impeller and, under the action of centrifugal force, is thrown to the periphery. As it moves toward the impeller outlet, the flow is deflected in a circumferential direction. A circulating flow is formed in the channel at the impeller outlet. The variable thickness of blades 2, increasing from the center to the periphery of the impeller on the rear (non-working) side, helps reduce the likelihood of flow separation from the blade surfaces and the relative flow velocity ω in the channels by changing its direction. Rounding the end edges of blades 2 on the rear side along the length and on the side corresponding to the location and cross-section height of the pump's side channel leads to flow separation from the end edges of the working side of the blades and reduces the flow of liquid from the working side to the rear side due to the entrainment of the liquid by the circulating flow in the channel. At the same time, there are no low pressure zones or preconditions for cavitation to occur in the interblade space of the wheel.

Claims

An open-type vortex impeller for an open-vortex pump with a side channel, containing a hub with straight radial blades, characterized in that the blades are made of variable thickness, increasing from the center to the periphery of the wheel on the rear side, and have rounded end edges on the rear side along a length corresponding to the height of the cross-section of the side channel on the side where it is located.

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