VANE-TYPE PUMP AND HEAT RECOVERY DEVICE

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage of International Application No. PCT/DE2013/100373 filed Oct. 29, 2013 and which claims priority to German Application No. 10 2012 111 394.7 filed Nov. 26, 2012. The entire disclosure of each of the above applications is incorporated herein by reference.

FIELD

The invention relates to a vane-type pump with a housing, a rotationally drivable rotor, which has a number of slots, which in each case receive a displaceable vane, conveying cells of variable volume being formed between successive vanes, with a pump space receiving the rotor having the vanes, with side faces bearing laterally against the rotor and against the vanes and with a stroke contour which is arranged between the side faces and against which the outer ends of the vanes bear when the vane-type pump is in operation, and with ports which are provided in the side faces and at least one of which serves for filling the conveying cells and at least one of which serves for discharging a pressurized medium conveyed by the conveying cells, the medium containing water, alcohols, such as ethanol, ammonia or other organic liquids or a mixture of said substances, also a lubricant, the specific weight and/or the viscosity of which are/is higher than those stroke/that of the remaining constituents of the medium, wherein an outer margin of the ports which faces the stroke contour being arranged at a distance from the stroke contour and to a heat recovery device having an evaporation circuit which comprises a vane-type pump, which contains a medium to be evaporated, the medium containing a lubricant, the specific weight of which is higher than that of the remaining constituents of the medium and/or the viscosity of which is higher than that of the remaining constituents of the medium.

BACKGROUND

This section provides background information related to the present disclosure that is not necessarily prior art.

Vane-type pumps and heat recovery devices of the type referred to here are known. Particularly in engines, for example motor truck engines, the aim is to utilize the fuel optimally. Heat recovery devices are therefore used, in conjunction with motor vehicle engine exhaust gas heat recovery devices which serve for utilizing as far as possible the energy occurring during the combustion of the fuel in the engine, including the heat present in the exhaust gases. In conventional heat recovery devices of this type, in which a Rankine process, as it is known, takes place, vane-type pumps are employed. These convey a medium which is fed to an evaporation circuit of the heat recovery device. The medium used in carrying out the Rankine process comprises water, various alcohols, such as ethanol, ammonia or other organic liquids and also mixtures of such constituents. These constituents are distinguished in that relatively high wear of the vane-type pump occurs. In order to avoid this, a lubricant is added to said constituents, wherein the lubricant fraction preferably amounts into a maximum of 10% by weight, in order to avoid having to accept excessive losses of effectiveness in the evaporation of the medium inside the evaporation circuit. When conventional vane-type pumps are used in heat recovery devices of the type referred to here in order to implement the Rankine process, therefore, a medium is used which comprises a lubricant for reducing the wear of the vane-type pump. It became apparent that, because of the limited fraction of lubricant, there is still considerable wear.

SUMMARY

This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its objects and features.

The object of the invention, therefore, is to provide a vane-type pump which avoids the above-mentioned disadvantages associated with conventional vane-type pumps.

To achieve this object, a vane-type pump constructed in accordance with the present invention is proposed, which has a housing and a rotationally drivable rotor with a number of slots and with vanes arranged displaceably therein. The rotor is accommodated together with the vanes in a pump space, the side faces of which bear sealingly against the rotor and against the vanes accommodated in the slots. The space lying between the side faces is delimited on the outside by a face which is formed as a stroke contour and against which the outer vane ends bear with the vane-type pump in operation. As a result, between the vanes, conveying cells are formed, the volume of which is variable when the pump is operating. In the side faces of the pump space, ports are provided, at least one of which serves for filling the conveying cells and is designated as a suction port. At least one further port serves for discharging a medium which is conveyed by the conveying cells and which is pressed under pressure in these ports and is fed to a delivery region of the vane-type pump. The vane-type pump conveys a medium which contains water, alcohols, such as ethanol, ammonia or other organic liquids or a mixture of said substances. Moreover, the medium comprises a lubricant, the specific weight of which is higher than that of the remaining constituents of the medium. The lubricant serves for lubricating the contact regions between the rotor and side faces and between the vanes and side faces, and also the contact region between the outer ends of the vanes and the stroke contour. In order to avoid disadvantages when the medium is used in a heat recovery method also designated as a Rankine process, the lubricant fraction should be too high, because this has an adverse effect in an evaporation circuit of a heat recovery device. In order to ensure sufficient lubrication, in particular, in the especially loaded region where the vanes are in contact with the stroke contour, in spite of the reduced lubricant fraction, there is provision, according to the invention, whereby a margin of the ports which faces the stroke contour is arranged at a distance from the stroke contour. If, therefore, a look is taken at the side faces of the pump space which have the ports, it is clear that the ports have a margin, there being an outer margin which faces the stroke contour and a lower margin which lies opposite and which faces approximately the center of the pump space. The vane-type pump referred to here is distinguished in that the outer margin is arranged at a distance from the stroke contour, so that, when the vane-type pump is in operation, liquid comes to bear against the stroke contour on account of the centrifugal forces generated by the rotation of the rotor and of the vane cells. A liquid ring is formed, the thickness of which corresponds to the distance of the margin of the ports which faces the stroke contour. Since the lubricant has a higher specific weight than the remaining constituents of the medium conveyed by the vane cell, a lubricant ring at the stroke contour is formed, which, because of the distance of the margin of the ports, does not escape from the ports through which the pressurized medium is discharged. When the vane-type pump is in operation, the margin forms a lubricant ring, within which the lubricant is separated out from the remaining constituents of the medium. This lubricant is not discharged out of the pump space, so that it does not enter the delivery region of the vane-type pump. It is therefore not fed to an evaporation circuit of a heat recovery device.

By a lubricant ring along the stroke contour being formed with a thickness which corresponds to the distance of the outer margin of the ports from the stroke contour, a closed lubricant film is ensured in that region of the pump which is subjected to especially high wearing load, to be precise the contact region of the vane ends with the stroke contour. A highly concentrated lubricant is consequently available precisely for this region of wear, so that the wear within the vane-type pump is reduced to a minimum. Due to the distance of the port from the stroke contour, a liquid ring is formed after all, a high percentage of which is composed of lubricant. The medium discharged from a port consequently has a greatly reduced lubricant fraction.

In a preferred exemplary embodiment of the vane-type pump, there is provision whereby the outer contour of the rotor is also arranged at a distance from the stroke contour. As a result, a liquid ring built up during the operation of the vane-type pump is not disturbed, in particular is not interrupted, by the rotor, so that, on the one hand, an undisturbed lubricant film is available for the ends of the vane cells in the contact region with the stroke contour and, on the other hand, it is ensured that an intact lubricant ring can be formed on the stroke contour, so that the fraction of lubricant in the out of the ports lying in the delivery region is reduced.

In an especially preferred exemplary embodiment, there is provision whereby the distance of the margin of the ports from the stroke contour and the distance of the outer face of the rotor from the stroke contour are adapted to one another, preferably are of equal size.

In an especially preferred exemplary embodiment, there is provision whereby the distance, referred to here, of the margin of the ports from the stroke contour, on the one hand, and of the outer face of the rotor from the stroke contour, on the other hand, lies in the range of 0.1 mm to 2 mm, preferably in the range of 0.7 mm to 1.3 mm. A distance of 1 mm is especially preferred.

The object of the invention is, moreover, to provide a heat recovery device which does not have the above-mentioned disadvantages associated with conventional heat recovery devices.

To achieve this object, a heat recovery device constructed in accordance with the present invention is proposed, which has an evaporation circuit and a vane-type pump which conveys a medium to be evaporated, the medium containing lubricant, the specific weight of which is higher than that of the remaining constituents of the medium, and/or the viscosity of which is higher than that of the remaining constituents of the medium.

Further areas of applicability will become more apparent from the description provided herein. The description and specific exemplary embodiments noted in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 illustrates a partial sectional view of a vane-type pump constructed in accordance with the teachings of the present disclosure.

DETAILED DESCRIPTION

A non-limiting example of the present invention is explained in more detail below by means of the drawing. The single figure shows a basic diagram of part of a vane-type pump in longitudinal section with a rotor in a pump space.

FIG. 1 shows in cross section part of a vane-type pump 1 with a housing 3 and with a rotor 5 which has in its basic body 7 a number of slots 9. These are arranged radially to a mid-axis 11 of the rotor 5 which runs perpendicularly to the image plane of the figure. The slots 9 are preferably arranged at an equal distance from one another in the circumferential direction with respect to the rotor 5. The number of slots is freely selectable within a broad framework. In the exemplary embodiment, illustrated here, of the vane-type pump 1, the rotor 5 has eight slots 9, three of which are illustrated here. One runs in the direction of an imaginary vertical diametral line 13 and a further one runs on an imaginary horizontal diametral line 15. A further slot 9 is also arranged between them on an imaginary angle bisecting line. In the vane-type pump illustrated here, a further slot is provided in each case opposite the slots illustrated here, and also, symmetrically to the slot on the angle bisecting line, a further slot at top right and an eighth slot opposite this.

Arranged in the slots 9 are vanes 17 which are displaceable within the slots and which preferably completely fill the slots and bear sealingly against the lateral inner faces of the slots 9. Of the eight vanes of the exemplary embodiment, illustrated here, of the vane-type pump 1, again only three are illustrated.

Between two successive vanes lie conveying cells 19 and 21, the volume of which changes during the operation of the vane-type pump 1. The housing 3 of the vane-type pump 1 has a pump space 23 which comprises side walls. One of the side walls 25 is reproduced in a top view in the sectional illustration according to FIG. 1. The pump space 23 is delimited laterally by two side walls which are arranged parallel to one another and which lie at a distance from one another which is selected such that the side walls bear sealingly against the side faces of the rotor 5 and the side faces of the vanes 17.

The pump space 23 is surrounded by an inner face which surrounds the rotor 5 and which is designated as a stroke contour 27. This is formed elliptically in the broadest sense, so as to implement a vane-type pump 1 with two conveying spaces which are arranged symmetrically to the vertical diametral line 13 and are formed per se symmetrically to the horizontal diametral line 15. The conveying spaces are sickle-shaped.

Ports 29 and 31 are introduced into the side wall 25. Preferably, identical ports are provided in the side wall, not illustrated here, which lies opposite the side wall 25. Moreover, further ports are found symmetrically to the horizontal diametral line 15.

When the vane-type pump 1 is in operation, the medium conveyed by the vane-type pump 1 is sucked in through one of the ports illustrated in the FIG. 1, while the conveyed medium is pressed out through the other port.

The rotor 5 is mounted in a rotationally drivable manner in the housing 3, as a rule by means of a shaft which is arranged concentrically to the mid-axis 11 and which is coupled fixedly in terms of rotation to the rotor 5.

It is assumed below, by way of example, that the rotor is driven counter clockwise according to the arrow 33. When the rotor rotates, the outer ends of the vanes 17 bear sealingly against the stroke contour 27. During a rotational movement of the rotor 5, a conveying cell 19 formed between the vertical vane and the vane lying to the left of it enlarges its volume in the direction of the arrow 33. On the left of the middle vane can be seen the conveying cell 21, the volume of which is larger than that of the conveying cell 19, because, during the rotational movement of the rotor 5, the vanes travel outwardly, following the stroke contour 27, thus resulting in the larger volume of the conveying cell 21, as compared with the conveying cell 19.

Since the stroke contour 27 is formed symmetrically to the horizontal diametral line 15, the vanes, after reaching the horizontal position, as is reproduced in FIG. 1, are moved into the interior of the slots 9 by the stroke contour 27, so that a conveying cell volume located between two successive vanes is reduced. A port, not illustrated here, is provided symmetrically to the port 29.

Since the volume of the conveying cell 19 is enlarged during a rotational movement of the rotor 5, a medium is sucked in through the port 29 from the vane-type pump 1, as long as the port 29 is connected fluidically to the conveying cell. During further rotational movement in the direction of the arrow 33, the vane lying on the angle bisecting line reaches the left margin 37 of the port 29, so that there is no fluidic connection between the conveying cell 21 and the port. When the volume of the conveying cell 21 decreases in the course of further rotation of the rotor, the medium is acted upon with pressure and is discharged under pressure out of the port, not illustrated here, which is arranged symmetrically to the horizontal diametral line 15 with respect to the port 29.

The same applies correspondingly to the port 31, out of which a pressurized medium is pressed from a conveying cell.

The basic function, described here, of a vane-type pump is known and is therefore not dealt with in any more detail here.

FIG. 1 shows clearly that the port 29 has an outer margin 39 and the port 31 has an outer margin 41. The outer margins 39 and 41 face the stroke contour 27 and are arranged at a distance x from the stroke contour 27. The inner margin of the ports 29 and 31 which lies respectively opposite the outer margin 39 and 41 is concealed here by the side face of the rotor 5, as is indicated by a dotted line.

The medium conveyed by the vane-type pump 1 is water, alcohols, such as ethanol, ammonia or other organic liquids. It may also be here a mixture of said substances. A lubricant, the specific weight of which is higher than that of the remaining constituents of the medium, is additionally admixed to the medium.

Looking at the side face 25, it is clear that the outer margin 39 and 41 of the ports 29 and 31 approximately follows the stroke contour 27 in regions, but does not touch the latter because of the distance x. When the rotor 5 having the vanes 17 is set in rotation during the operation of the vane-type pump 1, centrifugal forces arise, on account of which that constituent of the conveyed medium which has the highest specific weight comes to bear against the stroke contour 27. It transpires, therefore, that a lubricant ring is formed on the inner face of the stroke contour 27, the thickness of said lubricant ring corresponding to the distance x of the outer margin 39, 41 from the stroke contour 27. Precisely in the region of the stroke contour 27, therefore, a lubricant film is formed, which contains only a very small fraction of water, alcohols or ammonia, so that the lubricating action of the lubricant is exerted precisely in the contact region of the outer ends of the vanes 17 with the stroke contour 27. Since the outer margin 41 of the port 31 is arranged at a distance x from the stroke contour 27, the lubricant is not discharged out of the port 31 because it cannot escape laterally over the margin. Only that fraction of the lubricant which settles in a lubricant ring which is higher than the distance x can escape out of the port 31. When the vane-type pump is in operation, therefore, an enrichment of the lubricant directly on the stroke contour 27 takes place. The medium escaping from the port 31 is thus lower in lubricant and is therefore especially suitable for being fed to a heat recovery device.

On account of the distance x of the outer margin 39 of the port 29 from the stroke contour 27, the lubricant also cannot escape from the port 29.

Preferably, moreover, there is provision whereby the outer contour 43 of the rotor 5 maintains a distance y from the inner contour 27. This configuration is therefore preferred because the lubricant ring which forms on the inner contour 27 when the vane-type pump 1 is in operation is consequently not damaged by the rotor 5. If the outer contour 43 were to touch the inner contour 27, the lubricant ring would be displaced completely and would have to be built up anew in subsequent regions which are touched by the outer ends of the vanes.

There is preferably a provision whereby the distance y corresponds to the distance x. In particular, it is preferable that the two distances x and y are formed identically.

This configuration ensures that, when the vane-type pump 1 is in operation, a stable liquid ring, virtually 100% of which is composed of lubricant, is formed on the inner contour 27. The outer ends of the vanes 17 consequently run on the stroke contour 27 within a lubricant ring, so that wear is reduced to a minimum.

The distance x of the ports 29 and 31 from the stroke contour 27 ensures a certain thickness of the lubricant ring, so that an interruption in lubrication is avoided with the highest possible probability. This is even more so if the outer contour 43 of the rotor 5 is arranged at a distance y from the inner contour 27, so that the lubricant ring can be formed continuously on the entire inner contour 27.

It became apparent that the distance x should preferably lie in a range of 0.1 mm to 2 mm, in particular in the range of 0.3 mm to 1.0 mm. A distance x of 1 mm is especially preferred. What otherwise applies here is: y≧x.

The lubricant fraction in the medium conveyed by the vane-type pump 1 affords not only the advantage of improved lubrication, but also the further advantage that volumetric gap losses between the outer end of the vanes, that is to say the vane head, and the inner contour 27 are reduced to a minimum. This is due to the higher viscosity of the lubricant in comparison with the remaining constituents of the medium.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

LIST OF REFERENCE SYMBOLS

1 Vane-type pump

3 Housing

5 Rotor

7 Basic body

9 Slots

11 Mid-axis

13 Vertical diametral line

15 Horizontal diametral line

17 Vane

19 Conveying cell

21 Conveying cell

23 Pump space

25 Side wall

27 Stroke contour

29 Port

31 Port

33 Arrow

35 Outer ends

37 Left margin

39 Outer margin

41 Outer margin

43 Outer contour

x Distance

y Distance