DE8808920U1 - Side channel machine - Google Patents

Description

U.Kayeer-Herold

Patent description " Since enkanalinaschine ¹¹

The invention relates to a side channel machine with axial blading for use as a pump or compressor. It is generally known that the operating characteristics and in particular the efficiency of side channel machines depend crucially on the type and design of the impeller (references 1-3). For example, the impeller losses in conventional side channel machines are up to 7596 of the total losses / 1 /. It is also generally known that conventional side channel machines have only been designed with radial impellers, although a side channel machine with axial blading was proposed and discussed in the laid-open specification DE-OS 1921 94S. The main sources of loss in conventional radial impellers are known to be impact, friction and gap losses. If it is therefore possible to use an impeller with lower losses, then the key parameters of efficiency, pressure coefficient and delivery ratio can be increased in a desirable manner.

It is generally known that the way the side channel machines work is based on the fact that the fluid in the side channel machine passes through the impeller several times and, after each such pass, transfers the peripheral impulse gained in the impeller to the liquid column contained in the side channel. The pressure build-up in the side channel is thus proportional to the peripheral impulse of the so-called mass exchange flow transferred to the side channel per unit of time. The mass exchange flow corresponds to the meridian volume flow through the impeller.

Using the generally known design equation for side channel machines / 1 /, the influence of the main determinants on the operating characteristics of a side channel machine can be assessed:

H» I^ ( ^c au - £, ) (Eq.1)

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U.Kayser-Herold - 2. -

In Eq.1:

H-head

A-Mass flow rate-Meridian mass flow g«Acceleration due to gravity f»Cross section of the side channel V-Conveying volume flow

c_ «Mean circumferential component of the flow at the blade outlet

According to equation 1, the most favorable impeller wheel must deliver large meridional mass flows A, i.e., in particular, a large -displacement number e_iifwnifl.eTi- and at the same time have large circumferential components c at the blade outlet. The circumferential component c is determined to a large extent by the reaction rate r of the blades./ 1 /.

However, it is not immediately clear from equation 1 which type of blade, e.g. axial or radial, best meets the above conditions, since in principle any blade with a reaction rate between 0 and 1 can be used in a side channel machine. However, it is generally known that axial impellers, due to their higher absorption rates, enable several times larger meridional mass flows or mass exchange flows than radial impellers of comparable diameter. It is also generally known that with axial impellers, the desired large circumferential components c at the blade outlet can be achieved by selecting the reaction rate appropriately, e.g. r«1/3.

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However, a closer examination of the axial blading disclosed in DE-OS 19 21 945 shows significant design defects, which do not allow any significant advantages to be achieved over conventional radial blading. In particular, the proposed sin and exit angles and the profile contours are not adapted to the requirements. The blade length, which is approximately half the width of the side channel, also results in disproportionately large return flow areas, with a corresponding reduction in the pressure coefficient. The invention is therefore based on the object of significantly increasing the performance, in particular the efficiency and pressure coefficient of side channel machines with axial blading.

U.Kayser-Herold - 3 -

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The object is achieved according to the invention by the features mentioned in the characterizing part of patent claim 1.

The resulting technical advantages of the invention are at least the following:

Because the axial blades are flowed through in two flows and thus act over the entire clear width of the side channel, twice as much energy or peripheral momentum is transferred to the fluid with each circulation through the side channel as with the single-flow, conventional axial blade according to DE-OS 19 21 94.5, which only acts over half the clear width of the side channel. From the ! Theory of side channel machines /Ibis3/ also shows that the pressure coefficient of the inventive double-flow axial blading is at least twice as high as with the single-flow design according to DE-OS 19 21 945. Furthermore, the inventive double-flow axial blading has smaller harmful backflow areas in the side channel than with conventional single-flow axial blades, since the average residence time of a fluid element in the side channel between exit and re-entry into the blade area is only half as long as with the single-flow design with half the blade length.

Due to the profile twisting running over the entire length of the blade, the shock losses over the entire inlet length of the axial blade are avoided at the design point according to the invention, whereas this is not possible with the axial blades with a constant angle of attack proposed in DE-OS 19 21 945 or only in a limited area of the inlet edge. In addition, the profile twisting according to the invention over the entire length of the blade allows the speed profile of the toroidal vortex core in the side channel to be adjusted with regard to the desired performance characteristics. J

The features of claim 2 determine the profile of the

double-flow axial blades are optimized with regard to a maximum pressure coefficient. From the theory of side channel machines, it can be deduced, among other things, that the maximum pressure coefficient ]

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then it is achieved when the ratio of meridional and peripheral exit velocity from the blade area assumes its greatest value. From the theory of turbomachines / 1 / it is generally known that this product is determined significantly by the degree of reaction of the blading. According to the invention, the axial blading can be used to achieve an optimal degree of reaction _f at which the

: pressure coefficient is maximum, determine and constructively implement. From the similarity laws of fluid mechanics it can be deduced that the optimal reaction rate is 1/3, from which according to the invention a slight hook shape of the blade

L profile over the entire length of the blade. According to the invention, the blade trailing edge is therefore also slightly forward

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&igr; Further details and features of the invention will become apparent

from the following description of a specific embodiment of the invention based on the drawings Fig. 1a,

2t 1 b and 1c.

^ Jp Fig. 1a shows a meridian section through a side channel machine according to the invention with a double-flow

&Ggr; axial blade ring on impeller 1 within a double-flow side channel 2a,2b,flem side channel housing 3 and the drive shaft 4.Each of the double-flow axial blades consists of an inner blade area 1a and an outer blade area 1b,wherein the inner blade area 1a and the outer blade area 1b have opposing angles of attack - [>a.The inner blade area 1a and the outer blade area 1b

y. are composed in the area 00. The opposing angles of attack -ßi between the inner blade area 1a and the outer blade area 1b are determined according to the invention by

_ Profile twist achieved over the entire blade length 1.

The angle of attack disappears locally at the transition from the inner blade area 1a to the outer blade area 1b at the point 00. The area 00 with the disappearing angle of attack lies according to the invention in the center circle of the toroidal exchange vortex 5. The course of the expansion vortex 5 during operation of the side channel machine corresponds to the meridional mass exchange flow, which flows alternately through the two side channel halves 2a and 2b. The meridian speed c in the inner blade area 1a is accordingly opposite to the meridian speed c -. in the outer blade area. !·*..*'.: :.".■..: .' : : _

U.Kayeer-Herold - 5 - -j

From Fig. 1a it can also be seen that the fluid crosses the impeller plane twice during each circulation in the side channel 2a, 2b according to the exchange vortex 5 and is thereby supplied with twice as much radial and peripheral momentum as with an eleven-flow axial impeller according to DE OS 1521 945.

Fig. 1b shows the plan view of the two-flow axial impeller according to the invention .

Fig. 1c shows a projection of the blade areas la, 1b in the direction of the blade axis 6, from which the profile twist and the slight hook shape of the blade profile a with the slightly forward-facing trailing edge bv can be seen. In particular, the entry angles -ß ., -9O ⁰ and the exit angles -ß ₂ ⁹⁰ ° are shown. Further advantages of this embodiment are that

-the entire blading can be formed from a sheet metal part, and that

-the axial thrust acting on the impeller bearing is completely balanced, since the axial force on the inner blade area 1a is opposite to the axial force on the outer blade area _1b and that

- the noise emission is significantly lower than with conventional side channel machines due to the small volume of gas enclosed in the blade space and the low impact and friction effects.

A further embodiment of the invention is shown in Fig. 2a, 2b and 2c and is described in more detail below: Fig. 2a shows a meridian section through a side channel machine with a double-flow axial wheel 7 in a double-flow side channel 8a, 8b and the inner axial blades 9a and the outer axial blades 9b, which are separated from each other by a dividing ring 10. Compared to the embodiment according to Fig. 1a, 1b and 1c ^, the opposite angles of attack of the inner axial wheel 9a and the outer axial blade 9b are achieved by profile setting in the area of the dividing ring 10. The axial blades 9a and 9b therefore have little or no profile distortion and flat inlet and outlet surfaces, which in special cases reduces the manufacturing effort.

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U.Kayser-Herold -> 6 -

From the flow curve 4" according to Fig. 2a, the exchange vortex according to streamline 11 can be seen in particular, which runs symmetrically around the dividing ring 10. Fig. 2b shows a partial development of the double-flow axial wheel 7 with the inner axial blade 9a (shown in dashed lines) and the outer axial blade 9b, as well as the relevant velocity triangles for the inlet and outlet flow of the inner and outer axial blades 9a and 9b. In Fig. 2b:

c _B *Meridian speed w-Relative speed csAbsolute speed ^Circumferential speed of the blade Angle of attack at the blade inlet

In Fig. 2b the following indices apply:

"i" for inner blading ⁿ a" for outer blading «1« for the blade inlet "2" for the blade outlet

From the velocity triangles according to Fig. 2b, the opposing flow rates or meridional velocities c of inner axial blades 9a and outer axial blades 9b become particularly clear.

As can be seen from Fig. 2b, the blade angle can be selected at the design point so that locally shock-free entry is possible at the inner and outer blades 9a, 9b. Fig. 2c shows a normal view of the double-flow axial impeller 7 with the inner axial blades 9a and the outer axial blades 9b, the dividing ring 10, the housing 12, the intake nozzle 13, the interrupter 14 and the outlet nozzle 15. The direction of rotation of the axial impeller 7 is indicated by arrow 16. The interrupter 14 is designed in a conventional manner, whereby in particular self-priming operation as a pump is also made possible.

U.Kayser-Herold Reference :

/ 1 / Pfleiderer,C ₁ / 2 / Gabi,M.

N.N.

The centrifugal pumps, 5th edition.

Appendix &Bgr;«

Springer Verlag 1961 Theoretical and experimental Investigation of the flow in Side channel compressors Dr.Ing.Dies.Unirers.Karlsruhe,

1982

Technical manual compressor

3.1ufl. Chapter 5.5

VEB Technology, Berlin, 1983

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Claims (1)

·· ·*': ^eltehkanaJmaischine ' greetings : Address 1 :S»lte^irawaT»awfth<Ti« _l g«v#mn«>»if>hTi«t by a ■double-flow axial impeller within a ■double-flow side channel with angles of attack of the inner, closer-to-the-axis blade areas that are opposite to the angles of attack of the outer, further-from-the-axis blade areas and a total length of the inner and outer blade areas that is equal to the clear diameter of the side channel, whereby the meridian velocities in the inner blade area are opposite to the meridian velocities in the outer blade area. Claim 2 ; Side channel machine according to claim 1, characterized in that the oppositely directed angle of attack -P ₁ of the shovel areas 1a and 1b by profile winding continuously over the entire blade length 1 to a positive angle of attack range + ^ ₁ from the foot of the inner blade area 1a to the blade center OO into a negative angle of attack range - β j of the outer blade area 1b from the blade center 00 to the blade tip, whereby in the blade center 00 the angle of attack becomes locally vanishingly small. Claim 3 tSide channel machine according to claim 1, characterized in that the oppositely directed angle of attack |3 ₁ is achieved by profile restriction between the inner axial blades 9a and the outer axial blades 9b. Claim 4 rSide channel machine according to claim 3, characterized in that a dividing ring 10 is arranged between the inner axial blades 9a and the outer axial blades 9b. Claim 5 ; Raised channel machine according to claims 1 to 4, characterized in that the axial blades have a hook shape corresponding to approximately 1/3 of the degree of reaction ron with a slightly forward-directed exit edge.