Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
  • F04D29/669—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for liquid pumps
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/40—Casings; Connections of working fluid
  • F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
  • F04D29/426—Casings; Connections of working fluid for radial or helico-centrifugal pumps especially adapted for liquid pumps
  • F04D29/428—Discharge tongues
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
  • F05B2260/00—Function
  • F05B2260/96—Preventing, counteracting or reducing vibration or noise

Definitions

• the present invention relates to a centrifugal pump.
• the invention relates in particular to a centrifugal pump capable of pumping liquids as free of pressure pulses as possible.
• Centrifugal 5 pumps of this type are used for example as feed pumps for paper machine head boxes.
• Centrifugal pumps are generally used in the transfer of substances in liquid form and mixtures containing mainly liquid, and the pumping effect is created by an impeller rotating inside a stationary pump casing. When the impeller moves the substance to be pumped the rotating 0 movement creates a centrifugal effect in the material and when the material arrives at the discharge opening, which in most cases is tangential, the centrifugal force moves it to the discharge duct.
• This kind of pumps are disclosed for example in German patent publication no. 25 25 16 and Finnish patent no. 53747.
• Finnish patent no. 87009 tries to remove the problem by a structure a characteristic feature of which is that the blade wheel of a centrifugal pump has at least one row of blades successive in the direction of the blade wheel periphery, the end of which adjacent the periphery is positioned at an inclined angle in relation to the movement of the blade wheel periphery. Further, it is characteristic of the blade wheel according to the patent
• the article gives the distance mentioned of 7 - 10 % of the radius of the impeller Secondly, Ekman suggests that since the feed pumps of a head box in most cases are double-sided, i.e. sucking from two opposite sides, which means that also the impeller is double-sided, the vanes of the impeller on the different sides of the impeller should not be positioned opposite to each other but staggered. Then, while the pressure pulse caused by a vane on one side is at its minimum the pressure pulse caused by a vane on the opposite side is at its maximum. Further, Ekman suggests that the tips of the vanes are inclined so as to extend the length of the pulses in the peripheral direction.
• the Finnish patent no. 87009 mentioned above relates to a corresponding single-suction impeller and suggests that the outer tip of the vane should be inclined so much that the rear edge of the preceding vane is at the same axial level as the leading edge of the following vane.
• the objective is to arrange the increasing and the decreasing pulses one after the other so as to obtain a pulseless flow.
• impellers of this structure are practically impossible to manufacture or at least to manufacture them such that they would in small sizes operate with an adequate efficiency.
• Finnish patent application no. 953241 in turn discloses a pump employing a single suction impeller which creates smaller pulse disturbances than before and which is more suitable for use for example as a feed pump in connection with a paper machine head box.
• a second objective of the solution disclosed in the publication is to provide an impeller which is easy to manufacture and solves the problems mentioned above.
• a characteristic feature of the pump according to the publication is that the impeller vanes and the volute cut-water at the junction of the spiral and the pressure opening serving with the impeller vanes as the means creating the pulses are set in such a position in relation to each other that, while the impeller rotates, at least one vane tip is always passing the volute cut-water whereby the pressure pulse created by the tip of the vane at the volute cut-water is all the time substantially constant and no remarkable pressure fluctuations occur in the discharge duct.
• the present invention examines the distance between the volute cut-water and the tips of the impeller vanes mentioned above in a new light.
• the reason for this is of course that inclining the tips of the vanes and the volute cut-water, which has been found to be a good method of reducing pulses, results in practice at least when trying to minimize the pulse effect, in a constructively impossible structure or, because of the complex manufacturing method, at least in a disproportionately expensive design.
• the initial distance considered is the distance 7 - 10 % of the impeller radius given by Ekman mentioned above. Studies have indicated among other things that the distance above may be extended manifold without loosing anything essential of other properties of the pump.
• an essential feature of the pump according to the present invention is that the distance of the outer edges of the impeller vanes from the volute cut-water between the casing and the pressure opening is at least 1/7 of the diameter of the pump impeller. If expressed with the measures Ekman uses (i.e. proportioning to the impeller radius) the distance is at least approx. 14 %.
• Fig. I is a schematic illustration of a centrifugal pump according to the invention partially in section at the impeller in a level perpendicular to the axis; and Fig. 2 is a curve illustrating the change of the pulse level as a function of the distance between the volute cut-water and the outer edge of the impeller vanes.
• Figure I illustrates a partial section of a centrifugal pump having a spiral pump casing 12 and an impeller 14 with working vanes 22 and 24 disposed inside the casing on a shaft and rotating with the shaft
• the casing naturally has a suction duct (not illustrated) and a discharge duct 16, in the casing side end of which there is a volute cut-water 18 at a distance s from the impeller 14, more precisely expressed from the outer edge of the vanes, to distribute a part of the flow circulating in the spiral to the discharge duct 16.
• Figure 2 illustrates test results studying the dying of pulses as a function of the distance between the volute cut-water and the impeller.
• the initial position has been a distance of the outer edges of the vanes of 3.3 % of the impeller diameter which is almost seven percent of the impeller radius.
• the tests started from the lower limit of the prior art design value and proceeded increasing the distance up to over 30 % of the radius.
• the curve in Fig. 2 indicates that in the prior art range the pulse level (the linear scale) is 2.5 - 4.2.
• the objective of the study was to halve --he pulse level of the existing pumps which (i.e. a relative value of 1.25) is obtained by arranging the distance s to be about 10 % of the impeller diameter, more precisely expressed from the outer edge of the impeller vanes. Naturally, the figure also indicates that already a distance of
• the pump is constructed from the beginning in a different way than before.
• the initial position of the prior art is that the impeller of an existing pump is turned in a lathe to reduce its diameter in order to obtain the desired distance. As a consequence of this, however, the capacity of the pump decreases dramatically.
• the initial position of the invention is that the form of the impeller is kept optimal in view of the efficiency and the pump casing is designed to meet the distance requirement mentioned earlier.
• a pump according to the invention is especially well suitable to be used as well as a main feed pump of a paper machine head box by means of which the fiber suspension to be distributed from the head box onto the wire section of the paper machine is introduced into the head box, as also as a dilution liquid pump used in modern head boxes by means of which white water or, for example, clean water is introduced into the head box as dilution liquid.
• the task of the liquid introduced with this kind of a pump is to replace the change of the slice opening by means of which the web thickness is regulated. By introducing more dilution liquid at some point along the length of the head box than at other points the same effect is obtained as by narrowing the slice opening.
• This kind of pumps are fairly small for example due to the fact that the liquid volumes they pump are very small compared with the ones pumped by the feed pump itself.
• the pulse level requirements of these pumps are the same as those of the main pump Dilution liquid pumps of this kind, as well as main feed pumps, are speed settable which in practice means that their capacity is regulated by controlling their speed of rotation and thus it is not necessary to change the size of the impeller by turning in a lathe which has been a precondition with the conventional liquid pumps referred to above.
• dilution liquid pumps most often mainly suck at the end, i. e. they are single-suction pumps, and thus their structure is simple and price relatively low.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=8547061

Family Applications (1)

Country Status (5)

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Family Cites Families (1)

• 1996
  • 1996-11-13 FI FI964551A patent/FI964551A/fi unknown
• 1997
  • 1997-11-06 WO PCT/FI1997/000672 patent/WO1998021480A1/en not_active Application Discontinuation
  • 1997-11-06 EP EP97911264A patent/EP0948717A1/de not_active Withdrawn
  • 1997-11-06 CA CA002268293A patent/CA2268293A1/en not_active Abandoned
  • 1997-11-06 JP JP52220998A patent/JP2001508849A/ja active Pending

Non-Patent Citations (1)

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