Abstract:
The housing of a vane-type machine has a largely cylindrical space for accommodating the vane cells. A shaft is eccentrically arranged in the housing. First and second guide plates are provided on the shaft. Slides displaceable largely radially to the shaft in the direction of the inner housing wall are guided by the guide plates. A vane cell is formed with the participation of two adjacent slides of the adjacent region of the inner housing wall and the volume of the vane cells in the region of an inlet opening differs from the volume of the vane cells in the region of an outlet opening. To increase the speed of the shaft and the temperature of the medium, the slides are lubricated by pressure oil and radially and axially guided by a guideway, which is fixed with respect to the housing.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a vane-cell machine for the expansion or compression of gaseous media, such as air, exhaust gases from an internal combustion engine, vaporous media or a mixture thereof, and also to a method for waste-heat utilization, preferably using at least one vane-cell machine. 
     A vane-cell machine is known from DE 201 17 224 U1. So that the expansion profile can be better adapted to thermal requirements and so that a vane-cell machine can be produced at low production costs, a vane-cell machine with vane-cell units is proposed which has cell volumes increasing and decreasing in the direction of rotation. 
     BRIEF SUMMARY OF THE INVENTION 
     The object on which the invention is based is to specify a reliable and efficient vane-cell machine and just such a method for the utilization of waste heat. 
     The vane-cell machine according to the invention serves for the expansion or compression of gaseous media, such as, in particular, air, exhaust gases from an internal combustion engine with a temperature of up to 500° C., vaporous media or a mixture thereof. The vane-cell machine has a housing which has a largely cylindrical space or a space of non-constant radius for receiving the vane cells of the vane-cell machine and also an inlet port and an outlet port in the space. A shaft is arranged eccentrically in the housing. First and second guide plates arranged essentially parallel to one another are provided on the shaft. The guide plates guide slides displaceable essentially radially with respect to the shaft in the direction of the inner wall of the housing. A vane cell is formed in each case by two adjacent slides and the adjacent region of the inner wall of the housing. The volume of the vane cells in the region of the inlet port differs from the volume of the vane cells in the region of the outlet port. According to the invention, the slides displaceable radially in the direction of the inner wall of the housing are preferably lubricated with pressure oil and guided radially and axially by a guide track. The guide track is configured at a fixed location with respect to the housing and is likewise preferably lubricated with pressure oil. 
     In a preferred embodiment of the invention, a first and/or a second continuous guide track are/is provided. This guide track or these guide tracks limits or limit the movement of the slides displaceable radially in the direction of the inner wall of the housing, in each case in such a way that the slide or that side of the slide which faces the inner wall of the housing, that is to say the end face of the slide, moves, essentially free of contact, along its entire path of movement, past the inner wall of the housing. 
     The vane-cell machine according to the invention serves for the expansion or compression of gaseous media, such as, in particular, air, exhaust gases from an internal combustion engine with a temperature of up to 500° C., vaporous media or a mixture thereof. The vane-cell machine has a housing which has a largely cylindrical space or a space of non-constant radius for receiving the vane cells of the vane-cell machine and also an inlet port and an outlet port in the space. A shaft is arranged eccentrically in the housing. A first and a second guide plate arranged essentially parallel to one another are provided on the shaft. The guide plates guide slides displaceable essentially radially with respect to the shaft in the direction of the inner wall of the housing. A vane cell is formed in each case by two adjacent slides and the adjacent region of the inner wall of the housing. The volume of the vane cells in the region of the inlet port differs from the volume of the vane cells in the region of the outlet port. According to the invention, the slides displaceable radially in the direction of the inner wall of the housing are preferably lubricated with pressure oil and are guided radially and axially by a guide track. The guide track is configured at a fixed location with respect to the housing and is likewise preferably lubricated with pressure oil. 
     In a preferred embodiment of the invention, a first and/or a second continuous guide track are/is provided. This guide track or these guide tracks limits or limit the movement of the slides displaceable radially in the direction of the inner wall of the housing, in each case in such a way that the slide or that side of the slide which faces the inner wall of the housing, that is to say the end face of the slide, moves, essentially free of contact, along its entire path of movement, past the inner wall of the housing. 
     This contact-free movement is achieved, in a preferred embodiment of the invention, by a non-cylindrical housing and a circular guide track or by a cylindrical housing and a noncircular guide track or by a special form of the housing and of the guide track. 
     In the case of a noncylindrical housing and a circular guide track, the following equations are to be solved numerically according to R, in order to arrive at a preferred embodiment of the invention: 
     
       
         
           
             
               x 
               2 
             
             = 
             
               
                 
                   t 
                   2 
                 
                 4 
               
               + 
               
                 
                   [ 
                   
                     b 
                     - 
                     
                       a 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         cos 
                         ⁡ 
                         
                           ( 
                           
                             φ 
                             + 
                             
                               arcsin 
                               ⁢ 
                               
                                 t 
                                 
                                   2 
                                   ⁢ 
                                   x 
                                 
                               
                             
                           
                           ) 
                         
                       
                     
                     + 
                     
                       
                         
                           r 
                           2 
                         
                         - 
                         
                           
                             a 
                             2 
                           
                           ⁢ 
                           
                             
                               sin 
                               2 
                             
                             ⁡ 
                             
                               ( 
                               
                                 φ 
                                 + 
                                 
                                   arcsin 
                                   ⁢ 
                                   
                                     t 
                                     
                                       2 
                                       ⁢ 
                                       x 
                                     
                                   
                                 
                               
                               ) 
                             
                           
                         
                       
                     
                   
                   ] 
                 
                 2 
               
             
           
         
       
       
         
           
             
               x 
               2 
             
             = 
             
               
                 
                   t 
                   2 
                 
                 4 
               
               + 
               
                 
                   [ 
                   
                     b 
                     - 
                     
                       a 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         cos 
                         ⁡ 
                         
                           ( 
                           
                             φ 
                             + 
                             
                               arcsin 
                               ⁢ 
                               
                                 t 
                                 
                                   2 
                                   ⁢ 
                                   x 
                                 
                               
                             
                           
                           ) 
                         
                       
                     
                     + 
                     
                       
                         
                           r 
                           2 
                         
                         - 
                         
                           
                             a 
                             2 
                           
                           ⁢ 
                           
                             
                               sin 
                               2 
                             
                             ⁡ 
                             
                               ( 
                               
                                 φ 
                                 - 
                                 
                                   arcsin 
                                   ⁢ 
                                   
                                     t 
                                     
                                       2 
                                       ⁢ 
                                       x 
                                     
                                   
                                 
                               
                               ) 
                             
                           
                         
                       
                     
                   
                   ] 
                 
                 2 
               
             
           
         
       
     
     The higher value of the two equations is used for the preferred design. 
     In this case, the following abbreviations apply: 
     x: the distance from the axis of rotation of the shaft to the wall of the housing 
     t: the width of the slides on the end face 
     b: the distance from the center point of the guide pins of the slides ( 140 - 151 ) to the end face of the slides 
     a: the distance between the axis of rotation of the shaft and the center point of the circular guide track 
     φ: the angle between the line x and the straight line through the center point of the rotor and the point of minimum distance between the shaft and the housing 
     r: the radius of the guide track 
     In the case of a cylindrical housing and a noncircular guide track, in a further preferred embodiment of the invention the following relations apply: 
     
       
         
           
             y 
             = 
             
               
                 
                   
                     R 
                     2 
                   
                   - 
                   
                     
                       ( 
                       
                         
                           
                             e 
                             · 
                             sin 
                           
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           φ 
                         
                         + 
                         
                           t 
                           2 
                         
                       
                       ) 
                     
                     2 
                   
                 
               
               - 
               
                 
                   e 
                   · 
                   cos 
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 φ 
               
               - 
               b 
             
           
         
       
       
         
           for 
         
       
       
         
           
             0 
             ≤ 
             φ 
             ≤ 
             π 
           
         
       
       
         
           for 
         
       
       
         
           
             y 
             = 
             
               
                 
                   
                     R 
                     2 
                   
                   - 
                   
                     
                       ( 
                       
                         
                           
                             e 
                             · 
                             sin 
                           
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           φ 
                         
                         - 
                         
                           t 
                           2 
                         
                       
                       ) 
                     
                     2 
                   
                 
               
               - 
               
                 
                   e 
                   · 
                   cos 
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 φ 
               
               - 
               b 
             
           
         
       
       
         
           
             π 
             ≤ 
             φ 
             ≤ 
             
               2 
               ⁢ 
               π 
             
           
         
       
     
     The explanation of the abbreviations is as follows: 
     y: the distance from the axis of rotation of the shaft to the center of the guide track 
     R: the radius of the cylindrical housing 
     e: the distance between the axis of rotation of the shaft and the center point of the cylindrical housing 
     t: the width of the slides on the end face 
     φ: the angle between the line y and the straight line through the center point of the rotor and the point of minimum distance between the shaft and the housing 
     b: the distance from the center point of the guide pins of the slides to the end face of the slides 
     The embodiment according to the invention with a cylindrical housing and with a noncircular guide track is particularly preferred. 
     Owing to the lack of mechanical contact by virtue of the measures according to the invention, virtually no friction occurs between the end face of each slide and the inner wall of the housing. The useful life and the efficiency are thereby markedly increased, as compared with frictional vane-cell machines. Owing to the absence of mechanical contact, the vane wheel or the vane cells of the vane-cell machine according to the invention rotates or rotate even in the case of a markedly lower differential pressure between the inlet port and outlet port. As a result, the vane-cell machine according to the invention makes it possible to use energy resources having low pressure differences, as compared with ambient pressure, which it has not been possible previously to utilize with a conventional vane-cell machine. Pressure equalization between the cells of the vane-cell machine via the small gap between the end face of each slide and the inner wall of the housing is virtually irrelevant. 
     In a preferred embodiment of the invention, a first guide track plate which is provided with the first guide track is provided, which is largely parallel to the first guide plate rotating together with the shaft. The first guide track plate is arranged fixedly in terms of rotation with respect to the housing. 
     In a further preferred embodiment of the invention, a second guide track plate which is provided with the second guide track is provided, which is largely parallel to the second guide plate rotating together with the shaft. The second guide track plate is arranged fixedly in terms of rotation with respect to the housing. 
     By virtue of these measures according to the invention, a compact set-up of the vane-cell machine and yet an accurate guidance, contact-free with respect to the inner wall of the housing, of the slides of the vane-cell machine can be achieved. The two guide track plates can be adjusted accurately in relation to one another. The result is a tilt-free radial movement of the slides. The first and, if appropriate, also the second guide track are preferably provided in the respective guide track plate in such a way that the distance of the end faces of the radially movable slides from the inner wall of the housing remains largely constant during the operation of the vane-cell machine. The first and, if appropriate, the second guide track may likewise be adapted to the eccentric arrangement of the shaft in the housing in such a way that the distance of the end face of the slides from the inner wall of the housing decreases during the rotational movement of the vane cells and the accompanying increasing pressure, that is to say, with an increasing pressure, adjacent vane cells are separated or sealed off from one another more effectively. This has an advantageous effect on the efficiency of the vane-cell machine. 
     In an advantageous embodiment of the invention, there is provision for the first and/or the second guide track plate to be screwed to the housing. Furthermore, there may be provision for the first and/or the second guide track plate to form the first and/or the second end face of the housing. 
     In a preferred embodiment of the invention, there is provision for the slides to be provided in each case with a first and/or a second guide pin which is led in each case through a longitudinal groove which in each case runs radially with respect to the shaft and is provided in the first and/or the second guide plate. A largely tilt-free radial displacement of the slides can thereby be carried out. 
     In a preferred embodiment of the invention, there is provision for there to be provided on the guide pin a crescent-shaped guide track sickle which is movable in rotation about its longitudinal axis and which is guided by the guide track. The guide track is preferably lubricated with pressure oil and/or mounted with pressure oil. By means of the guide track sickle, the forces occurring on the guide track during the radial displacement of the slides can be distributed to a larger area of the guide track and/or, if appropriate, of an oil film, as a result of which, in particular, the frictional losses and therefore possible wear can be reduced. By means of pressure-oil lubrication and/or pressure-oil mounting preferred according to the invention, the rotational speed of the shaft of the vane-cell machine can be markedly increased, as compared with a rolling mounting, and even media with markedly higher temperatures can be used, free of faults. Owing to the pressure-oil mounting of the guide track sickle, axial forces which arise can also be absorbed, in contrast to a rolling mounting. This has a positive effect on the efficiency, overall size, useful life and reliability of the vane-cell machine according to the invention. 
     In a further embodiment of the invention, there is provision for the first and/or the second guide track to be formed by a continuous guide track groove which is preferably milled in the inner surface of the first and/or of the second guide track plate. A cost-effective, accurate and reliable guidance of the slides in the radial and the axial direction can thereby be achieved. 
     In one embodiment, the vane-cell machine according to the invention has ducts which carry lubricating oil and which supply lubricating oil to the guide pin and/or the guide track sickle and/or in each case to a radially extending running groove of the slide in the first and/or the second guide plate. The supply of lubricating oil preferably takes place via at least one duct carrying lubricating oil in the shaft and/or the discharge of lubricating oil preferably takes place via at least one duct, discharging lubricating oil, in the first and/or the second guide plate. As a result, the reliability and the efficiency can be markedly improved by virtue of a possible increase in the rotational speed and the temperature of the medium used in the vane-cell machine according to the invention. 
     The method according to the invention for waste-heat utilization is preferably implemented using at least one vane-cell machine according to the invention. The exhaust gas from a stationary or mobile combustion apparatus is supplied to a first heat transfer device and/or an exhaust gas turbocharger. A first vane-cell machine compresses the air which is under ambient pressure, and the compressed air is supplied to the heat transfer device. The heat energy contained in the exhaust gas is then supplied to the compressed air. A second vane-cell machine expands or decompresses the compressed and heated air to a pressure which is lower than the pressure of the exhaust gas from the combustion apparatus or, if appropriate, lower than the pressure of the exhaust gas at the outlet of the turbocharger. The decompressed air and the exhaust gas leaving the heat transfer device or, if appropriate, the exhaust gas turbocharger are supplied to a third vane-cell machine. The third vane-cell machine expands the mixture of exhaust gas and air to ambient pressure and at the same time performs useful work. 
     The method according to the invention is distinguished by high efficiency and, particularly when vane-cell machines according to the invention are used, allows the expedient utilization of energy resources which are otherwise simply discharged, unused, into the environment in an undesirable way. 
     According to one embodiment of the invention, there is provision for the first vane-cell machine according to the invention to compress the air under ambient pressure or atmospheric pressure to approximately double the pressure of the outlet pressure of the exhaust gas at the exhaust manifold of the combustion apparatus or, if appropriate, to approximately double the pressure of the outlet pressure of the exhaust gas downstream of the turbocharger. The efficiency of the invention can thereby be further improved. 
     In one embodiment of the method according to the invention, there is provision for the combustion apparatus to be supplied with compressed ambient air which has been compressed by the first vane-cell machine. As a result, in the case of a suitable combustion apparatus, its efficiency can likewise be increased. 
     In one embodiment of the invention, a second heat transfer device is provided, which is supplied with heat energy from a cooling circuit of the combustion apparatus and with the residual heat of the exhaust gas/air mixture of the third vane-cell machine. The gaseous medium discharged by the second heat transfer device is expanded by a fourth vane-cell machine and at the same time performs useful work. By virtue of this measure according to the invention, the waste heat of the cooling circuit of an internal combustion engine can also advantageously be utilized. 
     In one embodiment of the method according to the invention, there is provision for the second heat transfer device to be an evaporation device which is supplied with liquid extracted from a liquid reservoir and acted upon with pressure by a pump, in particular water, nitrogen dioxide or cyclosiloxanes. The efficiency, already achievable by means of the method according to the invention, in the utilization of waste heat can thereby be further improved. 
     In one embodiment of the invention, there is provision for a gaseous medium expanded by the fourth vane-cell machine to be supplied to a condensation device, in which the gaseous medium condenses and at the same time discharges heat, and the liquid is supplied to the liquid reservoir. By virtue of this measure, an advantageous closed circuit for utilizing the residual heat of the exhaust gas/air mixture and the waste heat from the cooling circuit of the combustion apparatus is achieved. 
     The vane-cell machine according to the invention and the method according to the invention for waste-heat utilization are described in more detail below by means of exemplary embodiments, using drawings which are not necessarily true to scale. The same reference symbols designate identical or identically acting elements. In the drawings: 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  shows a vane-cell machine according to the invention in a sectional drawing which illustrates the operating principle according to the invention, 
         FIG. 2  shows a first system according to the invention for waste-heat utilization, with reference to which the method according to the invention is described, and 
         FIG. 3  shows a second system according to the invention for waste-heat utilization which has been further improved, as compared with the first system. 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  shows, by means of a diagrammatic cross-sectional drawing, the operating principle of a vane-cell machine  100  according to the invention for the expansion or compression of gaseous media, such as air, exhaust gases from an internal combustion engine, vaporous media or a mixture thereof. The housing  101  of the vane-cell machine  100  has a largely part-circular cross section and has vane cells  102  to  113  in its largely cylindrical inner space and outwardly an inlet port  114  and an outlet port  115 . A drive or driven shaft  116  is arranged eccentrically in the housing  101 . A first guide plate  117  and a second guide plate (not illustrated) are provided on the shaft  116 . The guide plates guide slides  119  to  129  in such a way that the slides can move essentially radially with respect to the shaft  116  in the direction of the inner wall  118  of the housing  101 . 
     When the shaft  116  is driven mechanically, it rotates, together with the guide plates, in the housing. By virtue of the centrifugal force, the slides  119  to  129  are moved radially outward during rotation. In this case, they are guided (not illustrated) in each case between two guide walls which are fastened to the guide plates and which close (not illustrated) the vane cells  102  to  113 , together with the shaft  116 , with respect to the latter. Each of the vane cells is therefore open outwardly only in the radial direction, insofar as the vane cell is not located in the region of the inner wall  118  of the housing  101 . The end face  131  of each slide  119  to  126  moves, at a slight distance from the inner wall  118  of the housing  101 , past the inner wall, that is to say the slides  119  to  126  and thereafter also the slides  127  to  129  move, preferably largely or completely free of contact, past the inner wall  118  of the housing  101 . In this exemplary embodiment, air under atmospheric pressure is located in the region of the inlet port  114 . When the shaft  116  is rotated clockwise  180  mechanically, for example by an electric motor or internal combustion engine, the air passes via the inlet port  114  into the subsequently largely closed vane cell  106 . On its way from the inlet port  114  to the outlet port  115 , the air is compressed on account of the decreasing volume of the vane cell. The compressed air leaves the vane-cell machine via the outlet port  115 . Part of the compressed air remains in the vane cell, and, according to the invention, this air is expanded to atmospheric pressure on its way from the outlet port  115  to the inlet port  114 . 
     By contrast, if an increased pressure prevails in the region of the outlet port  115 , as compared with the inlet port  114 , and the shaft  116  can rotate largely freely, the outlet port  115  becomes an inlet port and the inlet port  114  becomes an outlet port of the vane-cell machine  100 . In this case, the reverse process takes place, and the vane-cell machine decompresses the gaseous medium entering. In this case, the shaft  116  is rotated counterclockwise  181  and, for example, drives an electric motor, not illustrated, that is to say the vane-cell machine or its shaft  116  performs work. 
     According to the invention, there is provision for the housing  101  with a largely circular cross section per se to have in a part region  182  a radius increasing from the outlet port  115  to the inlet port  114 . As a result, the air which enters the vane cell  113  (in the event of a movement of the shaft  116  counterclockwise  181 ) and is under atmospheric pressure is expanded to a lower pressure, for example 0.95 bar. This pressure difference assists the rotation of the shaft and consequently increases the efficiency of the vane-cell machine  100 . 
     In order to achieve a largely contact-free sliding of the end face  131  of each slide past the inner wall  118  of the housing  101 , according to the invention at least one guide track  130  is provided. The guide track  130 , illustrated diagrammatically, determines the radial position of each slide  119  to  129 . The continuous guide track is preferably a guide groove or guide duct (not illustrated) which is located in the rear side of a guide track plate (not illustrated) and which is largely parallel to the guide plate  117  rotating together with the shaft  116 . In contrast to the guide plate  117 , the guide track plate (not illustrated) is arranged fixedly in terms of rotation with respect to the housing  101 . Preferably, the guide track plate is screwed to the housing and closes the housing upwardly. A guide pin  140  to  151  of each slide  119  to  129  runs preferably with a form fit in the guide track  130 . During the rotation of the shaft, each slide provided with a guide pin is guided into a predetermined position via the form fit of the guide track and pin, with the result that the respective vane cell is largely sealed off with respect to the inner wall of the housing and yet a contact of the end face of each slide with the housing or with the housing wall is largely avoided. An essentially friction-free rotation of the vane cells is thereby achieved, without this leading to any appreciable pressure loss via the gap remaining between adjacent vane cells. Overall, the efficiency of the vane-cell machine  100  according to the invention is markedly higher than in known frictional vane-cell machines. 
     This applies particularly in the case of low differential pressures between the inlet port and outlet port, because, even in this case, the vane cells can rotate and perform work on account of their essential freedom from friction, in contrast to known highly frictional vane-cell machines. So that low differential pressures can also be utilized, the vane-cell machine according to the invention or its vane cells may be designed with larger dimensions. By contrast, an increase in the dimensions of known frictional vane-cell machines also increases their frictional forces to be overcome, and therefore, in known vane-cell machines, this measure does not lead to any improvement. 
     In a preferred embodiment of the invention (not illustrated), the underside of the housing also has provided on it a guide track plate screwed to the housing and having a guide track for guiding lower pins (not illustrated) which are likewise attached to the slides. 
     Owing to the double guidance, the slides can be guided radially, largely tilt-free. Furthermore, according to the invention, the pins may be provided in each case with a guide track sickle which can be rotated about the pins and which is guided by the guide track. As compared with a pin, the guide track sickle has a larger contact surface with the guide track, which is preferably lubricated with pressure oil, with the result that the surface pressure falls, friction is further reduced and reliability or useful life increases. 
     Preferably, the slides and the guide pins or the guide track sickles are lubricated and/or mounted in their guides via suitable ducts (not illustrated) carrying lubricating oil. What is preferred is pressure-oil lubrication or pressure-oil mounting, since higher rotational speeds and higher temperatures of the medium used than, for example, in rolling mountings, can be implemented, with the result that the efficiency rises and the structural dimensions and consequently the costs can be reduced. 
       FIG. 2  shows a first system according to the invention for waste-heat utilization, with reference to which the method according to the invention is described. The system according to the invention has a combustion apparatus  201 , a first heat transfer device  204  with an inlet and with an outlet, an exhaust gas turbocharger  205 , a first vane-cell machine  206 , a connecting line  210 , a second vane-cell machine  211  and a third vane-cell machine  214 . 
     The combustion apparatus  201  sucks in air  202  under ambient pressure or atmospheric pressure and expels hot exhaust gas  203 . The hot exhaust gas is supplied to the first heat transfer device  204  via its inlet. Air under atmospheric pressure  207  is sucked in by the first vane-cell machine  206  and compressed to approximately double the outlet pressure of the exhaust gas at the exhaust manifold of the combustion apparatus. If, by contrast, the combustion apparatus has an exhaust gas turbocharger, as illustrated, the air is compressed by the first vane-cell machine to approximately double the outlet pressure of the exhaust gas downstream of the exhaust gas turbocharger. During compression, tap air for the combustion apparatus may be extracted (not illustrated) from the first vane-cell machine. The compressed air  209  is led into the connecting line  210  which connects the outlet of the first vane-cell machine  206  to the inlet of the second vane-cell machine  211 . The connecting line  210  is arranged (not illustrated) in the form of heat coils in the heat transfer device  204 , in order to transfer a large part of the heat energy  208  contained in the exhaust gas to the compressed air led through the connecting line  210 . In the heat transfer device, the compressed air is heated on the countercurrent principle approximately to the temperature of the exhaust gas, and the exhaust gas is cooled approximately to the temperature of the compressed air. The heated compressed air enters the second vane-cell machine  211  and decompressed air leaves the second vane-cell machine. The air emerging from the second vane-cell machine  211  has a pressure which lies below the pressure of the exhaust gas emerging from the combustion apparatus or, if an exhaust gas turbocharger is present, as illustrated, below the pressure of the exhaust gas emerging from the exhaust gas turbocharger. 
     A further connecting line connects the outlet of the heat transfer device  204  to the inlet of the exhaust gas turbocharger  205  and supplies this with the cooled exhaust gas from the combustion apparatus. The exhaust gas compressed by the exhaust gas turbocharger  205  and leaving the turbocharger at the outlet  212  is combined with the compressed air discharged from the second vane-cell machine  211 . The mixture  213  of compressed air and of compressed exhaust gas is supplied to the inlet of the third vane-cell machine  214  which expands the compressed mixture to a mixture  215  having atmospheric pressure. During decompression in the third vane-cell machine  214 , the latter performs work, for example via an electric generator flanged to the shaft of the third vane-cell machine. 
       FIG. 3  shows a second system according to the invention for waste-heat utilization which has been further improved in relation to the first system  200  illustrated in  FIG. 2 . In addition to the first system, the second system  300  has a second heat transfer device  301 , a cooling circuit  302  of the combustion apparatus  201 , a fourth vane-cell machine  304 , a liquid reservoir  305 , a pump  306  and a condensation device  309 . 
     The expanded mixture of air and exhaust gas  215  emerging from the third vane-cell machine and the cooling circuit  302  heating the second heat transfer device  301  supply heat energy to the second heat transfer device. An evaporable liquid  307  present in the liquid reservoir  305  is pumped into the second heat transfer device by the pump  306 . In the second heat transfer device  301 , the liquid supplied is evaporated on account of the heat energy supplied via the cooling circuit  302  and the mixture  215  of expanded air and of expanded exhaust gas. The vapor has a pressure which is higher than the pressure of the liquid in the liquid reservoir  305 . The vapor is supplied to the inlet of the fourth vane-cell machine  304  and via the outlet of the latter is supplied, after the expansion or decompression of the vapor, to the condensation device  309 . The liquid  308  occurring in the condensation device is recirculated into the liquid reservoir  305 . 
     During the expansion of the vapor, the fourth vane-cell machine  304  performs useful work, for example via an electric generator flanged to the shaft of the vane-cell machine  304 . 
     If the systems illustrated in  FIGS. 2 and 3  are provided with vane-cell machines according to the invention, as is preferred according to the invention, then the systems are distinguished, in particular, by particularly high efficiencies. Moreover, even low differential pressures can be utilized for performing work or for generating electrical current. 
     LIST OF REFERENCE SYMBOLS 
     
         
         
           
               100  Vane-cell machine 
               101  Housing 
               102  to  113  Vane cell 
               114  Inlet port 
               115  Outlet port 
               116  Shaft 
               117  Guide plate 
               118  Inner wall 
               119  to  129  slide 
               130  Guide track 
               131  End face 
               140  to  151  Guide pin 
               160  to  171  Longitudinal groove 
               180  Clockwise rotation 
               181  Counterclockwise rotation 
               182  Part region of the housing 
               200  First system according to the invention for waste-heat utilization 
               201  Combustion apparatus 
               202  Air under atmospheric pressure 
               203  Exhaust gas 
               204  Heat transfer device 
               205  Exhaust gas turbocharger 
               206  First vane-cell machine 
               207  Air under atmospheric pressure 
               208  Heat energy contained in the exhaust gas 
               209  Compressed air 
               210  Connecting line 
               211  Second vane-cell machine 
               212  Outlet of the exhaust gas turbocharger 
               213  Mixture of air and exhaust gas 
               214  Third vane-cell machine 
               215  Expanded mixture of air and exhaust gas 
               300  Second system according to the invention for waste-heat utilization 
               301  Second heat transfer device 
               302  Cooling circuit 
               303  Gaseous medium 
               304  Fourth vane-cell machine 
               305  Liquid reservoir 
               306  Pump 
               307  Liquid 
               308  Liquid 
               309  Condensation device