WO2008080437A1

WO2008080437A1 - Suction pipe

Info

Publication number: WO2008080437A1
Application number: PCT/EP2007/000695
Authority: WO
Inventors: Rudi Dittmar; Markus Kopf
Original assignee: Gardner Denver Deutdchland Gmbh
Priority date: 2007-01-05
Filing date: 2007-01-26
Publication date: 2008-07-10
Also published as: ITMI20072405A1; DE102007001770A1; EP2097647A1

Abstract

A suction pipe for drawing in a fluid mix comprises an intake nozzle (10) which can be subjected to negative pressure for drawing in a second fluid (4), with at least one intake nozzle opening (20) open counter to a direction of intake flow and an adding nozzle (11) adding a first fluid (3) to the second fluid (4) drawn in by the intake nozzle (10), which adding nozzle (11) surrounds at least partially an adding channel (24) with at least one adding channel inlet opening (28) for drawing in the first fluid (3) and at least one adding channel outlet opening following the adding channel inlet opening (28) in a direction of adding flow, wherein the adding channel outlet opening and the intake nozzle opening (20) merge with each other in such a way that at least most of the first fluid (3) flowing through the adding channel (24) passes into the intake nozzle (10).

Description

Suction pipe

The invention relates to a suction pipe for drawing in a fluid mix. The invention also relates to a pumping station for conveying a fluid mix located in a container.

For drawing in a gas, positive-displacement pumps are often used, especially in industrial applications. Liquid ring pumps are particularly conventional in this regard, on account of their robust construction. Although pumps of this type are suitable for conveying a gas, their limitations quickly become apparent, in the case of a gas/liquid mix, if the content of the liquid to be conveyed exceeds a critical value, generally of approximately 5 per cent by volume of the total volume conveyed. Exceeding this critical value, for example if there is an additional amount of liquid to be conveyed, results in the production of unpleasant noise, in cavitation which can damage the pump, in high mechanical loads being placed on the components of the pump and possibly in the pump becoming completely blocked.

The object of the present invention is to provide a suction pipe and a pumping station allowing the above-mentioned drawbacks of the prior art to be overcome.

The core of the invention is to supplement the intake nozzle of a suction pipe with an adding nozzle in such a way that, irrespective of the occurrence of an additional amount of liquid to be conveyed, in any case a liquid/gas mix is conveyed with a minimum gas content. The gas content prevents cavitation and a sudden rise in the power output of the pump, such as would occur were liquid conveyed without gas being added. The pump component loads are reduced and the service life extended. The amount of liquid concomitantly conveyed can be well above 5 per cent by volume based on the total volume conveyed. Further advantageous embodiments emerge from the sub-claims. Additional features and details of the invention will become apparent from the following description of a plurality of embodiments with reference to the drawings. They show:

Fig. 1 a schematic view of an embodiment of a pumping station with a suction pipe,

Fig. 2 a schematic longitudinal section through a first embodiment of a suction pipe,

Fig. 3 a schematic longitudinal section through a second embodiment of a suction pipe,

Fig. 4 a schematic longitudinal section through a third embodiment of a suction pipe,

Fig. 5 a schematic longitudinal section through a fourth embodiment of a suction pipe,

Fig. 6 a schematic longitudinal section through a fifth embodiment of a suction pipe,

Fig. 7 a schematic cross-section through a sixth embodiment of a suction pipe, and

Fig. 8 a schematic cross-section of a pre-storage means for limiting the maximum flow rate of liquid passing into the pump.

A pumping station 1 for conveying a two-phase mix 31, which consists of a first fluid 3 having a density pi and a second fluid 4 having a density p₂ > pi and is located in a container 2 closed so as to be gas and liquid-tight, will be described hereinafter with reference to Fig. 1. The first fluid 3 is, in particular, a gas. The second fluid 4 may, in particular, be a liquid. The container 2 comprises a feed line 12 for introducing the first fluid 3 and the second fluid 4 into the container 2. The feed line 12 can be regulated via a feed line valve. The pumping station 1 comprises at least one pump which is configured as a liquid ring pump 5 and has a pump inlet 6 and a pump outlet 7. To the pump inlet 6 there is coupled, by way of a coupling part configured as a gas and liquid-tight hose 8, a suction pipe 9 comprising said coupling part. As shown in Fig. 8, provision is made to connect the hose 8 to the pump inlet 6 by way of a liquid separation device configured as a pre-storage means 46 (not shown in Fig. 1). The pump inlet 6 is configured as a pump inlet nozzle 48 with a pump inlet nozzle opening 49. The pump inlet nozzle 48 is, in this case, arranged substantially along a vertical direction 47. The pre- storage means 46 is, for example, in the form of a hollow cylinder and has an upper end wall 50, a lower end wall 51 and a side wall 52. Apart from a lower aperture 54 in the lower end wall 51 and an upper aperture 55 in the upper end wall 50, the upper end wall 50, the lower end wall 51 and the side wall 52 outwardly close a pre-storage means interior 56 so as to be gas and liquid-tight. Other geometric embodiments of the pre-storage means 46 are also conceivable. The pump inlet nozzle 48 is guided through the lower aperture 54 in the lower end wall 51 in a sealed manner, so the pump inlet nozzle 48 protrudes into the pre- storage means interior 56. The pump inlet nozzle opening 49 is, in particular, arranged above the lower end wall 51 of the pre-storage means 46 and below the upper end wall 50 of the pre-storage means 46. The hose 8 is connected to the upper aperture 55 so as to be gas and liquid-tight. The upper aperture 55 is arranged in the region of the upper end wall 50 so as not to overlap the pump inlet nozzle opening 49 in the vertical direction 47. The pump inlet nozzle 48 comprises, in the region of the pre-storage means interior 56, at least one bore 53 which is advantageously arranged in proximity to the lower end wall 51 of the pre-storage means 46. The bore 53 is, in particular, arranged at the lowest point of the pre-storage means 46.

In the region of the lower end wall 51 of the pre-storage means 46, a further pump, for example a side channel pump, can be arranged so as to be connected to the pre-storage means interior 56 in a sealed manner for drawing in the second fluid 4, in particular for drawing in liquid. In this case, the liquid ring pump 5 can be replaced by any other vacuum pump.

The specially configured suction pipe 9 comprises, in addition to the hose 8 and the pre-storage means 46, a riser pipe 45 with an intake nozzle 10 and an adding nozzle 11 and will be described hereinafter in greater detail.

The pumping station 1 further comprises a pressure regulation means 13 with a pressure sensor 15 and an adjustable pressure valve 16. The pressure sensor 15 and the pressure valve 16 are directly connected to the region of the container 2 that contains the first fluid 3. The pressure valve 16 is subjected to atmospheric pressure on the side remote from the container 2. Optionally, there may also be provided an adjustable pressure generator 14 (not shown in Fig. 1) for subjecting the pressure valve 16 to a pressure differing from atmospheric pressure.

Finally, the pumping station 1 comprises an inert air feed line 17 which can be regulated using a valve. The inert air used in this case may, in particular, be ambient air. The inert air feed line 17 opens directly into the liquid ring pump 5 via the pump inlet 6. Alternatively thereto, it may also be arranged in the region of the hose 8 or the riser pipe 45.

A first embodiment of the suction pipe 9 will be described hereinafter with reference to Fig. 2.

The riser pipe 9 is configured to be gas and liquid-tight. It can be subjected to negative pressure and has an intake nozzle 10 with an intake nozzle opening 20 which is open counter to a direction of intake flow 19. The intake nozzle 10 is in the form of a hollow cylinder, at least in a region adjoining the intake nozzle opening 20 in the direction of intake flow 19, although any sectional geometry of the intake nozzle 10 is possible. The intake nozzle opening 20 is surrounded by an intake nozzle edge 21 perpendicularly to the direction of intake flow 19. The hollow cylindrical intake nozzle 10 has a central longitudinal axis 22 and a diameter dA-

In the region of the intake nozzle opening 20, the intake nozzle 10 is surrounded by the hollow cylindrical adding nozzle 11. The adding nozzle 11 is arranged, in this case, concentrically to the intake nozzle 10. In the direction of the longitudinal axis 22, the adding nozzle 11 has a length 1. The adding nozzle 11 protrudes, in an adding nozzle overhang portion 23 in the direction of the longitudinal axis 22, beyond the intake nozzle edge 21 by an overhang of length u. The adding nozzle 11 is secured against displacement along the longitudinal axis 22 and perpendicularly to said axis in relation to the intake nozzle 10. It is accordingly fastened to the intake nozzle 10 via radially protruding struts (not shown in the figures). Spacers can also be arranged between the adding nozzle 11 and the intake nozzle 10. The adding nozzle 11 is advantageously fastened to the intake nozzle 10 in such a way that the length u of the overhang of the adding nozzle 11 over the intake nozzle edge 21 can easily be adjusted. The adding nozzle 11 is configured so as to be gas and liquid-tight and has a diameter dβ, wherein dβ > dA-

An annular cylindrical adding channel 24 is thus formed between the intake nozzle 10 and the adding nozzle 1 1 in such a way that the circumference of the adding channel 24 is surrounded by the adding nozzle 11 and the intake nozzle 10 forms, in an overlap portion 25, the inner wall of the adding channel 24.

The adding nozzle 11 has a lower adding nozzle edge 26 and an upper adding nozzle edge 27. The terms "lower" and "upper" shall refer, throughout the present description, to the typical arrangement of the pumping station 1 and the suction pipe 9 shown in the figures. Between the upper adding nozzle edge 27 and the intake nozzle 10, the adding channel 24 has an adding channel inlet opening 28. Also formed between the intake nozzle edge 21 and the adding nozzle 11 is an adding channel outlet opening 29. A valve, configured in particular as a nonreturn flap, can be arranged in the region of the adding channel outlet opening 29. The adding channel outlet opening 29 follows the adding channel inlet opening 28 in a direction of adding flow 30. The direction of adding flow 30 is opposed, at least in certain sections, to the direction of intake flow 19.

The operation of the pumping station 1, in particular of the suction pipe 9, will be described hereinafter. The liquid ring pump 5 generates an intake vacuum. The riser pipe 45 and the intake nozzle 10 are subjected to this negative pressure via the pump inlet 6 and the hose 8. The negative pressure applied to the intake nozzle 10 causes the second fluid 4 to be drawn into the riser pipe 45 through the intake nozzle opening 20 having the diameter d_A in the direction of intake flow 19. As the lower adding nozzle edge 26 protrudes beyond the intake nozzle edge 21 counter to the direction of intake flow 19, the second fluid 4 flowing through the intake nozzle opening 20 necessarily also flows through the adding nozzle overhang portion 23 of diameter dβ and passes through the adding channel outlet opening 29. In the region of the intake nozzle edge 21, the diameter of the intake flow cross-section narrows from dβ to d_A. This results in an increase in the intake flow speed, leading in turn to reduced static pressure in the region of the adding channel outlet opening 29. The reduced pressure in the region of the adding channel outlet opening 29 causes the fluid 3 located in the adding channel 24 and fluid 4, which as the case may be might also be located in the adding channel 24, to be drawn in through the adding channel 24 in the direction of adding flow 30. At the same time, the first fluid 3 is drawn into the adding channel 24 through the adding channel inlet opening 28. If the negative pressure generated in the region of the adding channel outlet opening 29 by the second fluid 4 flowing through the intake nozzle opening 20 is sufficiently great, the first fluid 3, which flows through the adding channel inlet opening 28 and is drawn through the adding channel 24 in the direction of adding flow 30, issues from the adding channel 24 through the adding channel outlet opening 29 and is entrained into the riser pipe 45 by the second fluid 4, flowing through the intake nozzle opening 20, in the direction of intake flow 19. In the intake nozzle 10, the first fluid 3 thus drawn in mixes with the second fluid 4 to form the fluid mix 31. As the first fluid 3 has a lower density than the second fluid 4, pi < p₂, the fluid mix 31 conveyed by the liquid ring pump 5 therefore also has a density lower than that of the second fluid 4 alone. Depending on how much second fluid 4 is present in the container 2, the first fluid 3 is also drawn into the riser pipe 45 directly through the intake nozzle opening 20 in the direction of intake flow 19. If, in particular, there is no second liquid 4, the liquid ring pump 5 conveys merely the first fluid 3. The liquid ring pump 5 operates in this case in nominal mode. The adding of the first fluid 3 to the second fluid 4 prevents cavitation and reduces the sudden rise in power output of the liquid pump 5 such as would occur were merely the second fluid 4 conveyed. The component load is reduced and the service life of the pump 5 extended. A further advantage of the conveying of the mix is that the liquid ring pump 5 can be operated by a drive motor less powerful than that which would be required if conveying of merely the second fluid 4 were anticipated, at least from time to time.

The relative proportions of the first fluid 3 and the second fluid 4 in the fluid mix 31 conveyed are dependent, inter alia, on the ratio of the diameters of the adding nozzle 11, dβ, and the intake nozzle 10, d_A, and on the length u of the adding nozzle overhang portion 23. The mixing ratio of the fluid mix 31 conveyed can thus easily be adjusted, for example by displacing the adding nozzle 11 on the intake nozzle 10 in the direction of the longitudinal axis 22.

The defined addition, controlled by the pressure regulation means 13, of gas, in particular of air, into the container 2 ensures the minimum gas mass flow rate required for conveying the mix, thus allowing, in particular, the conveyed volume flow rate of the fluid 4 to be adapted to the respective requirements. Inert air can also be added to the fluid mix 31 via the inert air feed line 17. This ensures the presence of a minimum content of gas in the fluid mix 31 conveyed by the liquid ring pump 5, thus preventing cavitation of the pump and eliminating peak loading of the components of the liquid ring pump 5.

Should the volume flow rate of the second fluid 4 conveyed intermittently be greater than that which the liquid ring pump 5 is able to convey without cavitation and overloading, then the pre- storage means interior 56 exerts its protective purpose. Through the hose 8, the fluid mix 31, comprising the first fluid 3 and the second fluid 4, passes into the pre-storage means 46, where the second fluid 4, issuing from the lower end wall 51, collects. The pump inlet nozzle opening 49 accordingly remains unobstructed, i.e. above the collected second fluid 4. The second fluid 4 passes into the pump inlet nozzle 48 through the at least one bore 53. The at least one bore 53 is dimensioned in such a way that at most the maximum admissible volume flow of the fluid 4 passes into the liquid ring pump 5, thus preventing cavitation and mechanical overloading of the parts of the pump.

A second embodiment of the suction pipe 9a will be described hereinafter with reference to Fig. 3. Indentical parts will be denoted by the same reference numerals as in the first embodiment, to the description of which reference is hereby made. Parts that differ in terms of construction but are functionally identical will be denoted by the same reference numerals followed by a. The main difference from the first embodiment is that the adding nozzle 1 Ia is closed, in the region of the lower adding nozzle edge 26a, by an annular cover 35 which leaves exposed merely a central flow channel 36 having a diameter do < d_A. The flow channel 36 is formed as a hollow cylinder and arranged concentrically to the longitudinal axis 22. It comprises a flow channel wall 37 in the form of a cylinder jacket and has, at the level of the cover, a flow channel intake opening 38 and, at the end opposing said intake opening, a flow channel outlet opening 39. The flow channel outlet opening 39 is located inside the intake nozzle 10a in such a way that the intake nozzle edge 21 is positioned, in the direction of the longitudinal axis 22, between the flow channel intake opening 38 and the flow channel outlet opening 39. In this embodiment, the outlet opening 29a of the adding channel 24a is formed by the annular region between the flow channel outlet opening 39 and the intake nozzle 10a.

A third embodiment of the suction pipe 9b will be described hereinafter with reference to Fig. 4. Identical parts will be denoted by the same reference numerals as in the second embodiment, to the description of which reference is hereby made. Parts that differ in terms of construction but are functionally identical will be denoted by the same reference numerals followed by b. The main difference from the second embodiment is that the intake nozzle 10b comprises an insert 40 narrowing the adding channel outlet opening 29b. The insert 40 extends, in the direction of the longitudinal axis 22, from the intake nozzle edge 21 into the interior of the intake nozzle 10b in such a way that the diameter of the free internal cross-section of the intake nozzle 10b constantly expands, in the direction of intake flow 19, from a minimum value d_R in the region of the intake nozzle edge 21, up to the internal diameter d_A of the intake nozzle 10b. A constriction 41 is thus formed between the insert 40 and the flow channel wall 37. The insert 40, in particular the constriction 41, is such that the fluid 3 drawn in through the adding channel 24b passes through the constriction 41, in normal operation of the pump, at at least the speed of sound.

The insert 40 reduces the proportion of the fluid mix 31 formed by the first fluid 3 drawn in through the adding channel 24b. If, in the region of the constriction, the drawn-in fluid reaches or exceeds the speed of sound, this has advantages in terms of regulation.

A fourth embodiment of the suction pipe 9c will be described hereinafter with reference to Fig. 5. Identical parts will be denoted by the same reference numerals as in the first embodiment, to the description of which reference is hereby made. Parts that differ in terms of construction but are functionally identical will be denoted by the same reference numerals followed by c. The main difference from the first embodiment is that the adding nozzle l ie does not concentrically surround the intake nozzle 10c, but rather surrounds a separate adding channel 24c which is arranged laterally of the intake nozzle 10c and has an adding channel inlet opening 28c and an adding channel outlet opening 29c. The adding channel 24c opens laterally into the intake nozzle 10c in such a way that the adding channel outlet opening 29c, which is oriented parallel to the longitudinal axis 22, is arranged entirely inside the intake nozzle 10c. The adding channel 24c also opens, offset relative to the intake nozzle edge 21 in the direction of intake flow 19, into the intake nozzle 10c. However, it is also possible for the adding channel 24c to be arranged flush with the intake nozzle edge 21. This embodiment allows a valve, for example a non-return flap, to be arranged in a particularly simple manner in the region of the adding channel outlet opening 29c.

A fifth embodiment of the suction pipe 9d will be described hereinafter with reference to Fig. 6. Identical parts will be denoted by the same reference numerals as in the fourth embodiment, to the description of which reference is hereby made. Parts that differ in terms of construction but are functionally identical will be denoted by the same reference numerals followed by d. The main difference from the fourth embodiment is that the adding channel 24d surrounded by the adding nozzle 1 Id opens into the intake nozzle 1Od through the intake nozzle opening 20 in the direction of the longitudinal axis 22. The adding nozzle Hd has an inlet region 42d adjoining the adding channel inlet opening 28d in the direction of adding flow 30, an adding nozzle outlet region 43d adjoining the adding channel outlet opening 29d counter to the direction of adding flow 30, and an adding nozzle connection region 44d connecting the adding nozzle inlet region 42d and adding nozzle outlet region 43 d.

A sixth embodiment of the suction pipe 9e will be described hereinafter with reference to Fig. 7. Identical parts will be denoted by the same reference numerals as in the fifth embodiment, to the description of which reference is hereby made. Parts that differ in terms of construction but are functionally identical will be denoted by the same reference numerals followed by e. The main difference from the fifth embodiment is that the intake nozzle 1Oe has an insert 4Oe which extends, in the direction of intake flow 19, from the intake nozzle edge 21 into the interior of the intake nozzle 1Oe and narrows the free flow cross-section. The adding nozzle outlet region 43e also expands in the region of the adding channel outlet opening 29e. The constriction 41 e is formed between the insert 4Oe and the adding nozzle outlet region 43e. The insert 4Oe and the extension of the adding nozzle outlet region 43e are such that the fluid 4 passes through the constriction 4 Ie, during normal operation of the pump 5, at at least the speed of sound. The insert 4Oe also allows the relative proportion of the fluid mix 31 formed by the first fluid 3 and the second fluid 4 to be adapted to the respective requirements.

The conveying behaviour of liquid ring pumps is markedly dependent on the temperature of the operating liquid and the liquid to be conveyed. High temperatures reduce the volumes conveyed, in particular at low intake pressures.

In order to achieve the desired volume flow rate of the second fluid 4 given a predetermined pressure in the container 2, for various temperatures of the fluid 4, the intake volume flow rate of the pump 5 has to be adapted. This can be achieved by switching pumps on/off as a function of temperature and as required. A further possibility is to adapt the configuration of the pump 5 to the maximum anticipated temperatures and to reduce the efficiency of the pump 5, for example by opening valves, as a function of temperature. A third, advantageous possibility is to adapt the rotational speed, and hence the volume conveyed, of the liquid ring pump 5 using temperature-adjusted frequency converters.

Claims

1. Suction pipe for drawing in a fluid mix (31), comprising a. an intake nozzle (10; 10a; 10b; 10c; 1Od; 1Oe) which can be subjected to negative pressure for drawing in a second fluid (4), with i at least one intake nozzle opening (20) open counter to a direction of intake flow (19) and b. an adding nozzle (11; 11a; l ie; l id) for adding a first fluid (3) to the second fluid (4) drawn in by the intake nozzle (10; 10a;

10b; 10c; 1Od; 1Oe), i. which adding nozzle (11 ; l la; l ie; l id) surrounds at least partially an adding channel (24; 24a; 24b; 24c; 24d) with ii. at least one adding channel inlet opening (28; 28c; 28d) for drawing in the first fluid (3) and iii. at least one adding channel outlet opening (29; 29a; 29b; 29c; 29d; 29e) following the adding channel inlet opening (28; 28c; 28d) in a direction of adding flow (30), c. wherein the adding channel outlet opening (29; 29a; 29b; 29c; 29d; 29e) and the intake nozzle opening (20) merge with each other in such a way that at least most of the first fluid (3) flowing through the adding channel (24; 24a; 24b; 24c; 24d) passes into the intake nozzle (10; 10a; 10b; 10c; 1Od; 1Oe).

2. Suction pipe according to claim 1, characterised in that the adding nozzle (11 ; l la; l ie; l id) is arranged relative to the intake nozzle (10; 10a; 10b; 10c; 1Od; 1Oe) in such a way that the direction of adding flow (30) is at least partially opposed to the direction of intake flow (19).

3. Suction pipe according to claim 1 or 2, characterised in that the adding channel inlet opening (28; 28c; 28d) is arranged above the intake nozzle opening (20).

4. Suction pipe according to any one of the preceding claims, characterised in that the suction pipe comprises an adjustable inert air supply means (17).

5. Suction pipe according to any one of the preceding claims, characterised in that the adding nozzle (11 ; 11 a) is displaceable on the intake nozzle (10; 10a; 1 Ob) in the direction of a longitudinal axis (22) in such a way that the displacement allows the mixing ratio of the fluid mix 31 conveyed to be adjusted.

6. Suction pipe according to any one of the preceding claims, characterised in that a liquid separation device is arranged at the pump-side end of the suction pipe (9; 9a; 9b; 9c; 9d; 9e) for limiting the maximum volume flow rate of liquid passing into the pump (5).

7. Pumping station for conveying a two-phase fluid mix (31) which consists of a first fluid (3) and a second fluid (4) and is located in a container (2), with a. a pump (5) for generating an intake vacuum, b. a suction pipe (9; 9a; 9b; 9c; 9d; 9e) according to any one of claims 1 to 6 coupled to the pump (5), and c. a pressure regulating means (13) for controlling the pressure prevailing in a container (2), comprising i. a pressure generator ( 14), ii. a pressure sensor (15), iii. an adjustable pressure valve (16).

8. Pumping station according to claim 7, characterised in that the conveyed amount of the first fluid (3) and the second fluid (4) is controllable using the pressure regulating means (13).

9. Pumping station according to claim 7 or 8, characterised in that the pump (5) is a liquid ring pump.