Often in agriculture, in industry and in private homes use pumping equipment. Their purpose is to move different types liquids. That is why pumping units have many varieties, a special place among which is occupied by centrifugal pumps.

The main working element of this equipment is Working wheel. This article discusses in detail the concept of the impeller, the device of this structural element, as well as its types.

1 The concept of the impeller and its device

The impeller (impeller) of the pump is the main working element of pumping equipment, which transmits the energy received from the motor. The outer and inner diameter of the blades, the shape of the blades, the width of the wheel can be determined using calculations.

The main purpose of the pump impeller is to generate centrifugal force, which creates pressure that sets the fluid flow in motion.

The design of the impeller includes the following main elements:

• front (leading) disk;
• rear (driven) disk;
• impeller, which consists of blades located between the disks.

The impeller blades of pumping equipment often have a curvature to the side opposite to the direction in which they move.

1.1 Pump impeller functions

The principle of operation of the impeller: when the working cycle begins, the liquid accumulates between the blades simultaneously with the start of rotation of the impeller. Under the influence of rotation, a centrifugal force appears, contributing to the appearance of pressure; then the liquid moves away from the middle of the impeller and gradually presses against the walls. The pumped medium, under pressure, is discharged outside through the discharge pipe, while a minimum pressure is created in the middle of the impeller, facilitating the flow of the next portion of fluid to the impeller.

It should also be noted that this process occurs cyclically, thanks to which the operation of pumping equipment is stable and uninterrupted.

1.2 Types and differences

Impellers are of the following types:

• open;
• closed;
• semi-closed.

Today, a centrifugal pump with an open impeller is practically not used, since their efficiency< 40%. Но на немногих землесосных снарядах давней постройки такие колеса еще эксплуатируются. Но данный тип крыльчаток имеет и преимущества.Они гораздо менее подвержены засорению, и их весьма легко можно защитить от износа стальными накладками. Также отремонтировать данный тип колес можно очень просто.

Semi closed type has a disc on the side that is opposite to suction. These types are not used in large soil units, but are used in small pumps for which the issue of clogging is the cornerstone.

Private types issue highest efficiency, they are used on all modern pumping equipment. They possess high strength, but their wear protection and repair is much more difficult than semi-closed and open impellers.

The closed wheel has from two to six working blades. Radial protrusions are usually made on its outer surface of the disks. Or protrusions that repeat the outline of the shoulder blades.

Impellers are most often produced in one piece. But in the United States of America they are sometimes made welded, from cast parts. In the case of hard-to-machine hard alloys, the impellers are sometimes made with a detachable hub made of a softer material.

1.3 The most commonly used types of landings

Tapered (conical) fit - allows easy installation and removal of the impeller from the pump shaft. The disadvantage of this fit is the less accurate position of the impeller relative to the casing of the pump unit in the longitudinal direction than with a cylindrical fit. The impeller is mounted rigidly on the shaft, so it is immobilized. In addition, the conical fit, as a rule, gives large runout of the impeller, and this, in turn, negatively affects the gland packings and.

Cylindrical fit - ensures the exact position of the impeller on the shaft. The wheel is fixed on the shaft by one or more keys. This landing used in peripheral pumps, and submersible peripheral pumps. The disadvantage of such a fit is the need for precise processing of both the pump shaft and the hole itself in its hub.

Landing hexagonal (cross-shaped) - as a rule, it is used in pumping equipment for wells. This landing provides easy installation and removal of the impeller. It firmly fixes it on the shaft in the axis of its rotation. By means of special washers, the gaps in the diffuser wheels are adjusted.

Landing in the form of a six-sided star - is used in vertical and horizontal multistage high-pressure pumping units, in which the impellers are made of stainless steel. This design is the most complex, it requires the highest class of processing of both the shaft and the impeller. It firmly fixes the impeller on the axis of rotation of the shaft. The gaps in the diffusers are regulated by bushings.

2 Causes and symptoms of a broken impeller of centrifugal pumps

The most common cause of impeller failures is cavitation - vaporization and the appearance of vapor bubbles in the liquid, which leads to metal erosion, due to the presence of high chemical aggressiveness of the gas in the liquid bubbles.

The main causes of cavitation:

1. Temperature > 60°C
2. Too long and not enough large diameter suction pressure.
3. Loose connections on the suction head.
4. Suction head contamination.

Damage signs:

1. Vibration.
2. Crackling during suction.
3. Noises.

Tip: if the above symptoms are present in the pump, it is better to stop using it. Since cavitation reduces the efficiency of the device, its pressure and performance, the parts of the pumping unit become rough, and subsequently it will be necessary to repair or purchase a new device.

2.1 Repair

If the device still refused to work, you can fix it yourself. For you need to disassemble it:

1. The first step is to remove the coupling half using a special puller.
2. The next step is to direct the rotor to the stop of the unloading disk in the direction that produces suction.
3. Mark the location of the axis shift arrow.
4. Disassemble the bearings, remove the liners.
5. By means of the stripper, the unloading disk is pulled out.
6. Using forcing screws, remove the impeller from the shaft.

If the material is steel, if the wheel is worn out, then it is first directed, and then turned into lathe. With severe wear of the wheel, it is removed, after which a new one is welded.

If the material is cast iron, if the wheel is worn out, then the necessary places are poured with copper, and then they are machined, but cast iron wheels, as a rule, are simply changed.

The last step is to assemble the pump back in the following sequence:

1. Wipe the parts of the centrifugal pump.
2. If there are burrs or nicks, they are eliminated.
3. The impeller is assembled on the shaft.
4. Put the boot disk in place.
5. Install the soft stuffing box.
6. Tighten the nuts.
7. Roll the seal.
8. Until the stop of the unloading disk, the rotor is fed into the heel.

3 Main characteristics of modern centrifugal pumps

The best representatives modern pumps are: submersible pump with a Calpeda B-VT series peripheral impeller, as well as a self-priming pumping unit 1SVN-80A and an electric pump 1ASVN-80A.

3.1 Purpose of pumps CALPEDA B-VT

CALPEDA B-VT pumps are used for pumping clean (for contaminated liquids, you can use semi-submersible pumps Calpeda VAL or Calpeda SC) non-explosive liquids that do not contain particles that are abrasive, suspended or highly aggressive for the materials from which the pump is made.

Thanks to small size these electric pumps are very well suited for installation in different devices and devices of cooling, circulation and air conditioning systems.

Operating limitations of CALPEDA B-VT pump units

1. Liquid temperature: for water<90 °C, для масла < 150°C.
2. Ambient temperature< 40°C.
3. Continuous mode of use.

Self-priming pumping equipment 1SVN-80A and 1ASVN-80A. used for pumping uncontaminated liquid: water, alcohol, diesel fuel, gasoline, kerosene and similar neutral liquid with viscosity<2⋅10-5 м 2 /с температурой -40 – 50 °Cи плотностью <1000 кг/м 3 .

Pump units 1SVN-80A are produced with right and left rotation, when viewed from the end of the shaft. In the left rotation device, the drive end of the shaft is located on the side of the suction pipe, the direction of movement of the shaft is counterclockwise.

In the apparatus of right rotation, the drive end of the shaft is located on the side of the discharge pipe, the rotation of the shaft is clockwise. It is necessary that the direction of movement of the shaft coincides with the direction of the arrow on the pressure section of the pumping equipment (checked by a short test run of the drive of the device).

3.2 Modeling the impeller in FlowVision (video)

The invention relates to the field of centrifugal pumps. The impeller of the centrifugal pump contains at least two blades with different entry angle β l1 . All blades of the impeller are located with a constant outer pitch α and have the same exit angle β l2. In a particular case, each blade corresponds to a blade with the same entry angle β l1 located symmetrically with respect to the center of the impeller. The impeller may include three pairs of blades with different entry angles β l1. An increase in pump efficiency is achieved in the range of flow values ​​that are different from the calculated value. 4 w.p. f-ly, 3 ill.

The invention relates to the field of centrifugal pumps, in particular, to the design of their impellers, and can be used to improve the efficiency of pumps in heat and water supply systems.

The vane system of pump impellers is profiled for the calculated value of the pump flow based on the condition for reducing hydraulic losses. Minimization of hydraulic losses allows to ensure the maximum efficiency of the pump in the optimal mode of its operation, corresponding to the calculated value of the flow.

The main regularities for profiling the vane system of the impeller of a centrifugal pump are set out in the publication: M.D. EISENSTEIN Centrifugal pumps for the oil industry. - M.: State Scientific and Technical Publishing House of Oil and Mining and Fuel Literature, 1957. However, the impeller designed in accordance with the specified source will provide minimal hydraulic losses, i.e. high value of pump efficiency, only in a narrow area near the calculated pump flow rates.

The technique for constructing a vane system of a centrifugal pump was developed in the work of: A.N. MACHINE. Profiling of the flow part of impellers of centrifugal pumps. - M.: Moscow Order of Lenin Power Engineering Institute, 1976. This publication describes in detail the method for calculating all parameters of the vane system, while the pump equipped with such an impeller also shows high efficiency only when operating in the optimal mode or close to it.

Thus, impellers known from the prior art do not allow efficient use of the pump at delivery values ​​that differ significantly from the calculated ones.

However, in real conditions, in particular in heat supply and water supply systems, a significant part of the time the pump is operated in a mode other than optimal, for example, when the flow value is less than the calculated one. Under such conditions, the efficiency of the pump is significantly reduced. It should be noted that the manufacturer sets the calculated flow rate closer to its maximum value, since the pump must ensure stable operation over the entire declared flow range. Therefore, the optimal mode of operation of the pump does not always correspond to the mode of operation, and the time-weighted average efficiency of the pump may be significantly lower than the calculated one.

The objective of the invention is to increase the efficiency of the pump in the range of pump flow values ​​that differ from the calculated flow value.

To solve this problem, a centrifugal pump impeller is proposed, which contains at least two blades having different entry angles. All blades can have the same exit angle. All blades can be arranged with a constant outer pitch. Each blade can correspond to a blade with the same entry angle, located symmetrically with respect to the center of the impeller, while these blades form a pair. The impeller may include three pairs of blades with different entry angles.

When using the invention, the following technical results are achieved:

Increasing the efficiency of the pump in the range of pump flow values ​​that differ from the calculated value of the pump flow;

Improving the time-weighted average efficiency of the pump.

The description of the implementation of the invention is explained by reference to the figures:

figure 1 - the original impeller;

figure 2 - upgraded impeller;

figure 3 - dependence of the efficiency of the pump on the feed for the original and upgraded wheels.

The blades of the impeller shown in figure 1 have a working surface, represented in the drawing by the line L, which is referred to in the following as the outer line of the blade. The leading edges of the blades 1 lie on the inlet circle having a diameter D1. The exit edges of the blades 2 lie on the exit circumference with a diameter D2, usually coinciding with the outer diameter of the impeller. The angle between the trailing edges of the blades α, hereinafter referred to as the outer pitch, is the same for all blades.

The tangent to the outer line of the blade at the point of its intersection with the entry circle and the tangent to the entry circle at the specified point form the entry angle β 1l. The tangent to the outer line of the blade at the point of its intersection with the exit circle and the tangent to the exit circle at the specified point form the exit angle β 2l.

The values ​​of the parameters D1, D2, β 1l and β 2l are determined for the calculated pump flow under the condition of maximizing the efficiency of the pump, and also taking into account design limitations, and are the same for all blades. Since, as shown in the above work by A.N. Machine, the conjugation of the entry and exit angles can be carried out by a smooth curve of arbitrary shape, then we can assume that these parameters determine the shape and location of the impeller blades. All the blades of such an impeller, hereinafter referred to as the original blades, are the same.

The vanes of an impeller designed for a different pump flow will have different entry and exit angles, with the entry and exit angles decreasing for lower flow and increasing accordingly for higher flow.

Studies have shown that by replacing part of the original blades with blades having a different entry angle, the efficiency of the pump increases in the delivery area for which the added blades are designed. In this case, it is advisable to keep the exit angle of the replacement blades equal to the exit angle of the original blades. The diameters of the inlet and outlet circles, set taking into account design constraints, for the replacement blades are also kept equal to the corresponding values ​​of these parameters defined for the original blades. The outer pitch remains constant for all blades and its value does not change.

With the implementation of such a modernization of the impeller, the efficiency of the pump at the optimal operating mode, for which the original blades are designed, is expectedly reduced. However, the increase in pump efficiency in the region of low flow rates exceeds its drop in the region of the optimal mode, which makes it possible to obtain a higher time-weighted average pump efficiency.

Figure 2 shows the upgraded impeller having three pairs of blades. Each pair is formed by blades located symmetrically relative to the center of the impeller, while the blades of each pair have the same entry angle, while the entry angles of the blades included in different pairs are different. Such a wheel shows the best results, however, it is a special case of the invention.

Figure 3 shows the dependence of the pump efficiency on the mode of its operation for the original and upgraded wheels. An increase in pump efficiency in the low flow area up to 4.5% when using the upgraded impeller is accompanied by a slight decrease in the optimal mode, which confirms the achievement of the claimed technical result.

1. The impeller of a centrifugal pump, characterized in that it contains at least two blades having a different entry angle.

2. The impeller according to claim 1, characterized in that all the blades have the same exit angle.

3. The impeller according to claim 1, characterized in that all the blades are arranged with a constant outer pitch.

4. The impeller according to claim 1, characterized in that each blade corresponds to a blade with the same entry angle, located symmetrically relative to the center of the impeller, while these blades form a pair.

5. The impeller according to claim 4, characterized in that it includes three pairs of blades with different entry angles.

Similar patents:

The invention relates to a centrifugal pump containing a plurality of channels, at least one element of which has one or more non-axisymmetric channel contours formed at least partially by blades or blades of unequal height, and methods for manufacturing and using such pumps for pumping fluids, for example, in and from boreholes (wellbores), although the invention is applicable to pumps designed for any intended use, including, but not limited to, so-called work to transport fluids to the surface.

The invention relates to hydraulic engineering, mainly to the oil industry, and can be used in the production of formation fluid, water and other liquid media from wells with a wide range of mechanical impurities

The invention relates to pump engineering, in particular to centrifugal-type pumps with a working axial-radial tunnel mud wheel with a one-sided axial inlet. The centrifugal pump contains a housing with an inlet pipe passing into the central part of the housing. The central part of the body passes into the pressure pipe. A tunnel-type impeller is installed in the central part of the casing. Annular channels are made on the front annular disk of the wheel. A step is made on the inner wall of the central part of the housing in front of the pressure pipe inlet. On the inner side of the housing cover, installed from the side of the inlet pipe, annular collars are made. The invention is aimed at increasing the efficiency and the maximum allowable rotation speed and reducing the frontal resistance to rotation and the noise level. 3 ill.

The invention relates to pump engineering, namely to chemical horizontal centrifugal electric pump units. The production method of the unit consists in the manufacture of a prefabricated pump housing, a rotor with a shaft and an impeller, as well as a power unit. The body of the running gear of the pump is equipped with bearings. The body of the pump flow part is made with a flow cavity sufficient to accommodate the impeller and the spiral collector. The impeller is made in the form of a closed-type multi-pass impeller with a main and cover disk. Behind the main disk there is a water seal in the form of an autonomous disk with an impeller and an annular removable element framing it along the contour. The radius of the hydraulic seal impeller is less than the radius of the wheel. The main disk of the wheel is provided with an annular ridge. The ridge forms an annular channel with the wall of the wheel hub, which communicates with the hydraulic seal and through a through hole in the main disk through the wheel volume. The pump is assembled and mounted on the support platform of the pump and drive using power half-couplings. After assembling the electric pump unit, tests are performed. The group of inventions is aimed at increasing the resource, durability, reliability of operation, protection against leakage of pumped media and toxic fumes into the atmosphere with reduced labor, material and energy intensity of production. 4 n. and 21 z.p. f-ly, 7 ill.

The invention relates to pump engineering, namely to electric pump units designed for pumping chemically aggressive liquids. The unit contains an electric motor, a centrifugal pump and a power clutch. The pump is made single-stage, cantilever type, contains a housing with housings for running and flow parts. The body of the flowing part includes a collector body with an annular ledge-shaped ridge, combined with a pressure branch pipe, a back wall made of conjugated annular ridge of the collector body and a ledge-shaped annular element of the back wall, as well as a removable lead-in cover with an inlet axial branch pipe. The running gear housing is equipped with a crankcase and bearings. The open-type impeller is made in the form of a multi-thread impeller, including a main disk equipped with a system of blades with a hub and an annular ridge along the contour. The ridge is made with an outer radius congruent to the reciprocal inner radius of the annular ledge-shaped ridge. The disk is endowed with a system of radial blades that form an impeller. The pump has a water seal in the form of an additional autonomous disk mounted on the shaft, equipped with an impeller with a system of radial blades. The impeller radius is made smaller than the impeller radius. The invention is aimed at improving the protection against leaks, durability and reliability of the unit, reducing air pollution with toxic fumes. 12 w.p. f-ly, 5 ill.

The invention relates to pump engineering, and in particular to the construction of centrifugal slurry pumps of vertical type. The pump contains a housing, a rotor with a shaft and an open-type impeller. The impeller contains a main disk with a system of curved blades separated by interblade channels. The inner surface of the flow cavity of the pump housing and the impeller surfaces are covered with a protective layer of wear-resistant polymer material. The disk and blades of the impeller are made of a combined design, consisting of a shaping, mainly lamellar power frame and the specified protective layer. The protective layer is applied on both sides to the mentioned frame elements with the possibility of mutual pairwise self-anchoring of the opposing sections of the frame and blades. The frame of the disk and the blades are provided with perforations with a certain ratio of the total cross-sectional areas of the perforation and the polymer bridges filling it, mutually anchoring the protective layers, to the non-perforated area of ​​the frame. The diameter of the power frame of the disk is taken to be less than the design diameter of the impeller by at least two initial contour thicknesses of the protective layer. The height of the blade frame is assumed to be less than the design height of the blade for the initial contour thickness of the protective layer. The invention is aimed at increasing the resource, reliability of the slurry pump, the efficiency of pumping abrasive liquid media. 11 w.p. f-ly, 2 ill.

SUBSTANCE: invention relates to oil engineering and can be used in multistage centrifugal submersible pumps for pumping formation fluid with high gas content. The dispersing stage of the submersible multistage centrifugal pump contains a guide vane. The latter includes a lower and upper disk with blades, a semi-open impeller, which contains a drive disk with blades. A through annular groove is made in the driving disk of the impeller. The groove width is from two to ten percent of the maximum outer diameter of the blades. An annular groove is made in each blade of the drive disk. The diameter of the lower disk of the guide vane is not more than eighty-five percent of the outer diameter of the blades. At the inlet to the guide vane, at least one annular cut is made in each blade. The invention is aimed at improving the dispersing properties of the stage and increasing the reliability of its operation. 6 z.p. f-ly, 7 ill.

The invention relates to the field of centrifugal pumps

At the request of the client, the Electrogidromash company will supply spare parts for pumps own production: X, AH, AHP, ANS 60, ANS 130, S569M, S245. And also to pumps of various types: D, 1D, SDV, SM, SD, CNS, VK, K, KM, NKU, KS, NK, SM, TsVK, SE, Sh, NMSh, VVN, and many other pumps. In particular, such assemblies as a rotor assembly, an impeller, a sealing ring, a shaft, a protective sleeve, a guide vane, and a pump housing are supplied.

What gives the installation of new parts:

Spare parts for pumps are not only extending the service life of the unit, but also significant money savings. An example can be given: for a pump D 320/50 with an electric motor with a power of 75 kW, over 5 years of operation on a water supply system, the efficiency decreased by 10%. This led to a slight drop in flow (from 320 to 304 m3/h) and head (from 50 to 47.5 m). However, the corresponding losses of electricity turned out to be very significant: for the year they amounted to 65,700 kW / h, i.e. RUB 45,990, which greatly exceeds the cost of a new wheel ( 4600 rub.)

DESIGN OF CENTRIFUGAL PUMPS

General provisions

The design is based on the accumulated experience in creating various types of pumps. Moreover, for various areas of application of pumps, a different approach is used. This chapter deals with the design of stationary pumps for general industrial purposes. A distinctive feature is their work before cavitation, which is associated with their long-term operation and the need to exclude cavitation damage.

Despite the differences in the justification of the kinematic parameters and geometric dimensions of the flow path, there is a common approach to the design of pumps of various types. The design includes the preparation and analysis of the technical specifications, the selection of the main parameters and hydraulic calculations, the implementation of the draft layout of the machine, the verification and refinement calculations, the execution of drawings of the general view of the machine and its individual parts.

The graphic part of the project and the explanatory note are carried out in accordance with GOST 2.109-73, GOST 2.305-68 (ST SEV 367-76), GOST 2.108-68, GOST 2.307-68, GOST 2.308-68, GOST 10356-63, GOST 2789- 73, GOST 2.309-79, GOST 2.104-68 (ST SEV 140-74, 365-76), GOST 2.105-68 and GOST 106-68.

Terms of reference for design

The assignment for the design of a vane centrifugal pump includes the following basic data:

a) physical properties of the pumped medium:

r is the density of the pumped liquid, kg/m 3 ;

m - coefficient of dynamic viscosity, Pa С;

R np - saturated vapor pressure of the working fluid, PA (the physical properties of the pumped medium are set for the design temperature T 0 K);

b) pump parameters in the design mode:

H- head, m;

Q- volumetric flow rate of liquid through the pump, m 3 / s;

c) additional data. Along with the basic information about the pump, additional data is given that allows you to correctly approach the design of the pump.

Such data includes:

Information about the purpose of the pump and its scope;

Possible boundaries of changes in operating conditions;

Technical requirements (pump efficiency, weight, dimensions);

Ergonomic (noise level, db, vibration, mm or m / s 2, value

external leakage, m 3 / s);

Index of technical aesthetics and physiological indicators,

characterizing the ease of maintenance of the pump;

Economic (the cost of the pump or its installation, maintenance and

repair), resource, availability of individual units for maintenance, etc.

Calculation of basic parameters and geometric

pump impeller dimensions

2.3.1. Determination of wheel speed

The speed of the impeller is determined by the formula of Rudnev S.S. /16/

where C - cavitation coefficient of speed is selected in

depending on the requirements for the pump;

For long-term operation in the 1st critical mode

cavitation С 1 = 800¸1100;

To operate the pump in the second cavitation mode

C 2 \u003d 1000¸1800 (200).

The use of a screw centrifugal stage allows you to take the values ​​C 2 =1800¸3000 (5000)

- calculated value of backwater;

D h- backwater at the pump inlet, D h=1.5¸20 m.

Coefficient 1.15¸1.3 according to GOST 6134-71.

2.3.2. Determination of the speed factor

. (2.2)

2.3.3. Determination of the diameter of the entrance to the wheel D in

It boils down to determining the reduced diameter from the average static values ​​of the coefficient included in the formula:

- the reduced diameter of the impeller.

Finally

. (2.4)

The coefficient K 0 is selected from the following considerations /16/:

1. The impeller has a large cavitation reserve and cavitation is excluded in it. In this case, from the condition of obtaining a minimum relative velocity of fluid entry into the impeller

K 0=3.3¸3.7.

2. In the case of calculating the pump according to the 1st critical cavitation mode K 0=4.2¸4.6. Moreover, large values ​​are selected in case of possible operation of the pump during overload.

3. When calculating according to the 2nd critical cavitation regime K 0=4¸6 depending on the value FROM 2. So, for example, according to V.V. Shemel /16/

To 0 = 4.3¸4.65, FROM 2 = 1230¸1400,

To 0 = 5.2¸5.7, FROM 2 \u003d 1500¸2500.

Sleeve diameter D vm is determined by the approximate formula:

where N- pump power, kW;

a = 0.120¸0.130 - for cantilever pumps;

a= 0.150¸0.160 - for multistage pumps.

2.3.4. Wheel Width Determination in 2 at the exit

Wheel width in 2 is determined on the basis of statistical data by the formula

where for n s £120;

for n s>120.

Received value in 2 is preliminary and will be specified during the subsequent profiling of the meridional section of the impeller.

2.3.5. Approximate definition of outer diameter

impeller D 2

Impeller outlet diameter size D 2 depends on the number of blades in the wheel z and from the angle of installation of the blades at the outlet b l2.

As a first approximation, the size D 2 is determined on the basis of statistical data according to the formula /16/

where ;

.

2.3.6. Choice of number of blades z

The number of blades is chosen according to statistical data depending on the coefficient of speed n s and wheel sizes /16/:

n s = 50¸60; 60¸180; 180¸350; 350¸600;

z= 9¸8; 8¸6; 6; 6¸5.

For small-sized pumps, a smaller number of vanes is chosen to reduce the obstruction of the flow by the vanes, the thickness of which increases relatively with decreasing impeller dimensions. This improves the suction capacity of the wheel and reduces hydraulic losses. Sometimes, for low-speed wheels, some of the blades are shortened on the suction side.

2.3.7. Choice of blade thickness s

The thickness of the blades s is determined by technological considerations and strength, and sometimes wear resistance requirements (for example, for dredgers). Vanes are refined near the inlet to reduce flow restriction (usually 2 times) s 1

T a b l e 2.1

To the choice of the thickness of the impeller blades