Device and method for recovering waste heat energy and a utility vehicle

Abstract

A device for recovering the waste heat energy having a Clausius-Rankine circuit with a line system conveying a working medium via which at least one vaporizer for vaporizing the working medium, an expansion device for expanding the vaporized working medium to produce mechanical work, a condenser for fluidizing the vaporized and expanded working medium as well as a delivery pump for condensing and conveying the working medium through the line system are fluidically connected to one another. A compensation tank supplies additional working medium volume and is connected to a fluid line and can be fluidically separated from the line system via a valve that is controllable via a control device connected to a sensor for detecting working medium temperature and/or pressure, such that a working medium volume is transferred from the compensation tank into the line system or from the line system into the compensation tank.

Claims

1. A device for recovering waste heat energy of an internal combustion engine in a motor vehicle, the device comprising: a Clausius-Rankine circuit comprising a line system conveying a working medium, having at least one vaporizer for vaporizing the working medium, an expansion device, a condenser for fluidizing the working medium, and a delivery pump for condensing and conveying the working medium through the line system, the line system, the expansion device, the condenser, and the delivery pump being fluidically connected to one another; a compensation tank for supplying additional working medium volume and being connected to the line system by a single fluid line, the single fluid line being bi-directional and the single fluid line connecting the compensation tank to the line system at a single connection point located downstream of the condenser and upstream of the delivery pump; a switchable shut-off valve arranged in the single fluid line, the switchable shut-off valve for fluidically separating the compensation tank from the line system, the switchable shut-off valve being controlled to transfer a working medium volume from the compensation tank into the line system or from the line system into the compensation tank depending on working medium temperature and/or pressure, a feed pump arranged in the single fluid line such that an additional working medium volume is transferred from the compensation tank into the line system via the feed pump, and the feed pump and the switchable shut-off valve being arranged in series in the single fluid line with the switchable shut-off valve positioned between the feed pump and the single connection point and the feed pump positioned between the compensation tank and the switchable shut-off valve.

2. The device as claimed in claim 1, wherein the compensation tank is temporarily connected fluidically to the line system such that within the line system an at least localized supercooling of the working medium is adjusted as a function of a working medium volume transferred from the compensation tank and into the line system or vice versa.

3. The device as claimed in claim 1, wherein an exterior housing of the compensation tank is flexible and expandable, such that the compensation tank has a variable volume.

4. The device as claimed in claim 1, wherein the switchable shut-off valve opens or closes depending on a prescribed supercooling temperature and/or a detected pump performance such that a certain volume of working medium is transferred into or from the line system.

5. A device for recovering waste heat energy of an internal combustion engine in a motor vehicle, the device comprising: a Clausius-Rankine circuit comprising a line system conveying a working medium, having at least one vaporizer for vaporizing the working medium, an expansion device, a condenser for fluidizing the working medium, and a delivery pump for condensing and conveying the working medium through the line system, the line system, the expansion device, the condenser, and the delivery pump being fluidically connected to one another; a compensation tank for supplying additional working medium volume and being connected to the line system by two fluid lines that each connect directly to the line system at respective connection points that are located downstream of the condenser; a switchable shut-off valve for fluidically separating the compensation tank from the line system, the valve being controlled to transfer a working medium volume from the compensation tank into the line system or from the line system into the compensation tank depending on working medium temperature and/or pressure, a feed pump arranged in one of the two fluid lines such that an additional working medium volume stored in the compensation tank is transferred from the compensation tank to the line system, and the switchable shut-off valve being arranged in the other of the two fluid lines such that a working medium present in the line system is transferred from the line system into the compensation tank.

6. The device as claimed in claim 5, further comprising a non-return valve that is arranged at one of an intake or outlet of the feed pump.

7. The device as claimed in claim 5, wherein the one of the two fluid lines is a single direction flow line that flows in a direction from the compensation tank to the line system and the other of the two fluid lines is a single direction flow line that flows in a direction from the line system to the compensation tank.

8. A device for recovering waste heat energy of an internal combustion engine in a motor vehicle, the device comprising: a Clausius-Rankine circuit comprising a line system conveying a working medium, having at least one vaporizer for vaporizing the working medium, an expansion device, a condenser for fluidizing the working medium, and a delivery pump for condensing and conveying the working medium through the line system, the line system, the expansion device, the condenser, and the delivery pump being fluidically connected to one another; a compensation tank for supplying additional working medium volume and being connected to the line system by a first fluid line and a second fluid line; a first switchable shut-off valve and a second switchable shut-off valve for fluidically separating the compensation tank from the line system, the first switchable shut-off valve arranged in the first fluid line and being controlled to transfer the additional working medium volume from the compensation tank into the line system Rolland the second switchable shut-off valve arranged in the second fluid line and being controlled to transfer the working medium from the line system into the compensation tank depending on working medium temperature and/or pressure, and the delivery pump being arranged in the line system between a first line system connection of the first fluid line and a second line system connection of the second fluid line, such that, in a flow direction of the working medium through the line system, the second line system connection is arranged downstream from the delivery pump and the first line system connection is arranged upstream from the delivery pump.

9. The device as claimed in claim 8, wherein the volume of working medium is removed from the line system at the highest point of a line elevation at the first system connection of the line system, so that any harmful gas present in the circuit is collected at the line elevation and is transferred into the compensation tank together with the transferred working medium.

10. A utility vehicle with an internal combustion engine, comprising: a device for recovering waste heat energy of the internal combustion engine, the device comprising: a Clausius-Rankine circuit comprising a line system conveying a working medium, having at least one vaporizer for vaporizing the working medium, an expansion device, a condenser for fluidizing the working medium, and a delivery pump for condensing and conveying the working medium through the line system, the line system, the expansion device, the condenser, and the delivery pump being fluidically connected to one another; a compensation tank for supplying additional working medium volume and being connected to the line system by a single fluid line, the fluid line being bi-directional and the fluid line connecting the compensation tank to the line system at a single connection point located downstream of the condenser and upstream of the delivery pump; a switchable shut-off valve arranged in the single fluid line, the switchable shut-off valve for fluidically separating the compensation tank from the line system, the switchable shut-off valve being controlled to transfer a working medium volume from the compensation tank into the line system or from the line system into the compensation tank depending on working medium temperature and/or pressure, a feed pump arranged in the single fluid line such that an additional working medium volume is transferred from the compensation tank into the line system via the feed pump, and the feed pump and the switchable shut-off valve being arranged in series in the single fluid line with the switchable shut-off valve positioned between the feed pump and the single connection point and the feed pump positioned between the compensation tank and the switchable shut-off valve.

11. A method for recovering waste heat energy from an internal combustion engine of a motor vehicle, the method comprising: transferring the waste heat energy, at least partly, to a working medium conveyed in a line system of a Clausius-Rankine circuit; vaporizing the working medium via a vaporizer, in which the vaporized working medium is expanded at an expansion device thereby exerting mechanical work in which the expanded working medium is fluidized with a desired supercooling via a condenser, the supercooled working medium being compressed to a higher pressure level at a delivery pump; and setting the desired supercooling of the working medium within the line system by a previously blocked fluid connection line between a compensation tank for supplying an additional working medium volume and the line system, the previously blocked fluid connection line being temporarily opened in such a manner that a working medium volume is transferred from the compensation tank into the line system or vice versa, the fluid connection line being a single fluid connection line that connects the compensation tank to the line system at a single connection point located downstream of the condenser and upstream of the delivery pump, the single fluid connection line being bi-directional, a feed pump being arranged in the single fluid connection line such that the additional working medium volume is transferred from the compensation tank into the line system via the feed pump, a switchable shut-off valve being arranged in the single fluid connection line, and the feed pump and the switchable shut-off valve being arranged in series in the single fluid connection line with the switchable shut-off valve positioned between the feed pump and the single connection point and the feed pump positioned between the compensation tank and the switchable shut-off valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 is a first exemplary embodiment of a waste heat energy recovery device according to the invention having a Clausius-Rankine circuit comprising a line system to which a compensation tank for storing a working medium is isolatably connected,

(3) FIG. 2 is another exemplary embodiment of a waste heat energy recovery device according to the invention having a compensation tank of different construction,

(4) FIG. 3 is another exemplary embodiment of a waste heat energy recovery device according to the invention having a compensation tank of alternative construction,

(5) FIG. 4 is another exemplary embodiment of a waste heat energy recovery device according to the invention having an alternative connection arrangement of a compensation tank to a line system of a Clausius-Rankine circuit,

(6) FIG. 4A corresponds to the exemplary embodiment of FIG. 4 with the inclusion of a non-return valve at the intake of the feed pump,

(7) FIG. 4B corresponds to the exemplary embodiment of FIG. 4 with the inclusion of a non-return valve at the outlet of the feed pump, and

(8) FIG. 5 is another exemplary embodiment of a waste heat energy recovery device according to the invention having another connection arrangement of a compensation tank to a line system of a Clausius-Rankine circuit.

DETAILED DESCRIPTION

(9) FIG. 1 shows a first device 1 for recovering waste heat energy of an internal combustion engine not illustrated here of a utility vehicle, likewise not illustrated here. The device 1 comprises a Clausius-Rankine Circuit 2 having a line system 3 in which a working medium 4 is conveyed by a delivery pump 5 in the direction of flow 6. The device 1 furthermore comprises a first heat exchanger 8 designed as vaporizer 7, a second heat exchanger 10 designed as vaporizer 9, an expansion device 11 as well as a condenser 12. The basic process of waste heat recovery is as follows: The delivery pump 5 first compresses the working medium 4 once within a line system 3 to a higher pressure level and then conveys it in toward the vaporizers 7 and 9 in the direction of flow 6. The first heat exchanger 10 realized as vaporizer 9 then transfers waste heat energy from internal combustion engine exhaust gases 13 at least partly to the working medium 4, thereby causing it to vaporize in the vaporizer 7. For this purpose the still liquid working medium 4 flows through an input segment 14 into the vaporizer 7 and then exits the vaporizer 7 through an output segment 15 as vaporized working medium. By means of the second heat exchanger 10 realized as additional vaporizer 9, at least part of the waste heat energy from recirculated exhaust gasses 16 is likewise conducted to the working medium 4, causing it to vaporize in the additional vaporizer 9. In this process, the fluid working medium 4 flows into the vaporizer 7 through an input segment 17 and exits the vaporizer 7 through an output segment 18 as vaporized working medium. Provided between the input segment 14 and the additional input segment 17 is a control valve 19 by means of which the working medium 4 coming from the delivery pump 5 can be distributed, in each instance according to whether only one of the two vaporizers 7 and 9 or both of the vaporizers 7 and 9 are operating. The vaporized working medium 4 is further conveyed to the expansion device 11, where it is then expanded, thereby exerting mechanical output. The mechanical output in this case can be converted into electrical energy in a known manner by means of a generator (not illustrated here). Next, the expanded working medium 4 is further conveyed to the condenser 12, which is cooled by a cooling circuit 20 not further described. The condenser 12 condenses the already expanded working medium, which exists at the condenser outlet 21 with a required supercooling as a reliquified working medium 4. The working medium 4 then makes its way to a delivery pump intake 22 of the delivery pump 5 reliably liquefied and the Clausius-Rankine circuit 2 begins again.

(10) The device 1 is furthermore equipped with a compensation tank 25 which, in this first exemplary embodiment, is connected to the line system 3 via a single fluid line 26, specifically in a manner that the compensation tank 25 is integrated in the line system 3 such that it does not allow passage of working medium 4 therethrough in the direction of flow 6.

(11) The compensation tank 25 features a collection chamber 27 in which an additional working medium volume 28 is stored. Because the collection chamber 27 of the compensation tank 25 interfaces with the environment 30 via a filling and venting port 29, the air present in an upper portion 31 of the collection chamber 27 and thus above the working medium volume 28 is under atmospheric pressure. An activated charcoal filter 32 is placed in the filling and venting port 29 to prevent the working medium 4 from adversely dispersing into the environment.

(12) The compensation tank 25 has a rigid housing 33 and is therefore of rugged construction.

(13) To allow the additional working volume 28 stored in the compensation tank 25 to be transferred into the line system 3 or vice versa, the compensation tank 25 is connected to the line system 3 via fluid line 26 by means of a single connection point 34 downstream directly behind the condenser outlet 20.

(14) An overflowable feed pump 35 and a switchable shut-off valve 36 are arranged in the fluid line 26 such that on one hand the compensation tank 25 and the additional working medium 28 stored therein can be physically separated from the line system 3 and, on the other hand, an additional quantity of working medium 28 can be pumped from the compensation tank 25 into the line system 3 by means of the overflowable feed pump 35. In this respect, the overflowable feed pump 35 can also be used to increase line system pressure. If the overflowable feed pump 35 is not operating, a portion of the working medium 4 can conversely flow out of the line system 3 and back into the compensation tank 25 without any problem if the shut-off valve 36 is open and line system pressure is sufficiently high, since on one hand the collection chamber 27 and the compensation tank 25 are collectively only under atmospheric pressure and, on the other hand, the working medium 4 can flow through the idle and thus overflowable feed pump 35. In this instance, the shut-off valve 36 can thus be used to reduce line system pressure.

(15) The further device 101 illustrated in FIG. 2 is essentially the same as the device 1 shown in FIG. 1. Therefore the same components or components performing the same function are provided with the same reference numbers, and only the distinguishing features of the further device 101 are described.

(16) The further device 101 for recovering waste heat energy is characterized by a differently designed compensation tank 125 which is constructed such that the additional working medium volume 28 stored therein cannot permanently interact with the ambient air 140. For this purpose, the compensation tank 125 features in addition to a working medium filling port 141 arranged laterally on the lower third 142 of the compensation tank 125 a filling gas filling port 143 situated on the lid area 144 of the compensation tank. Both the working medium filling port 141 and the filling gas filling port 143 can each be hermetically sealed by means of a cap not illustrated. This specific design ensures that a filling gas 145 inert to the additional working medium volume 28 always collects in the upper half 144 of the compensation tank 125 and the additional working medium volume 28 accordingly collects in the lower half 146 of the compensation tank 125. The compensation tank 25 likewise features a rigid housing 33 and is accordingly designed to be pressure-resistant.

(17) The alternative device 201 illustrated in FIG. 3 is likewise essentially the same as the devices 1 and 101 illustrated in FIGS. 1 and 2, respectively. Therefore the same components or components performing the same function are provided with the same reference numbers, and only distinguishing features of the further device 201 are accordingly described.

(18) The alternative device 201 for recovering waste heat energy is characterized by another alternatively constructed compensation tank 225. This alternative compensation tank 225 is designed as a bellows unit 250 hermetically sealed against the environment 30, thereby allowing different amounts of working medium volume 28 to be taken up by changing the volume of the alternative compensation tank 225 itself. In other words, the size of the compensation tank 225 adapts to the additional working medium volume 28 being stored. For this purpose, the alternative compensation tank differs from the two previously described compensation tanks 25 and 125 by not having a rigid housing 33, but rather an at least partly flexible housing 251 in the form of a bellows 252. In this embodiment, the compensation tank 225 does not necessarily have to be filled with air (see FIG. 1) or with an inert filling gas (see FIG. 2). Instead of the bellows 252, a membrane container or an elastic bladder element could be provided.

(19) In any case the compensation tanks 25, 125 and 225 shown in FIGS. 1 through 3 are separably or connectably arranged fluidically in relation to the line system 3 in such a manner that an at least local supercooling of the working medium 4 within the line system 3 downstream from the condenser outlet 20 and upstream from the delivery pump intake 37 can be adjusted as a function of the working medium volume 28 transferred from the compensation tank 25 into the line system 3 or vice versa.

(20) The further device 301 for recovering waste heat illustrated in FIG. 4 is characterized by a different connection arrangement 355, by means of which the compensation tank 25 is connected to the existing line system 3. Otherwise, the device 301 is of identical construction in terms of its Clausius-Rankine circuit 2. Insofar attention in this regard is directed to the explanations regarding the devices 1, 101 and 201, and only the features associated with the connection arrangement 355 deviating from this material are explained below. As FIG. 4 clearly illustrates, the compensation tank 25 in this instance is fluidically connected to the line system 3 via two fluid lines 356 and 357. In this case a pressure-resistant feed pump 358 is arranged in the upstream front fluid line 356 such that the additional working medium volume 28 can be conveyed or transferred from the compensation tank 25 into the line system 3. The pressure-resistant feed pump 358 is characterized in that no working medium 4 can flow through it from the line system 3 and into the storage tank 25 unless the pressure-resistant feed pump 358 is running. Furthermore, a switchable shut-off valve 36 is arranged in the rear fluid line 357 such that the working medium 4 can be transferred from the line system 3 and into the compensation tank 25 if the shut-off valve 36 is accordingly in the open position. Alternatively, the rear fluid line 357 is also tightly closed, thereby physically separating the compensation tank 25 from the line system 3. Also, as shown in FIG. 4A, a non-return valve 359 can be arranged at the intake of the feed pump 358 or, as shown in FIG. 4B, the non-return valve 359 can be arranged at the outlet of the feed pump 358.

(21) The other device 401 for recovering waste heat energy illustrated in FIG. 5 differs from device 301 (see FIG. 4) only in that an additional shut-off valve 460 is installed in the front fluid line 356 instead of the pressure-resistant feed pump 358 (see FIG. 4) and that the delivery pump 5 is arranged between a front fluid connection 461 of the front fluid line 356 and a rear fluid connection 462 of the rear fluid line 357. In this way, the delivery pump 5 can readily be used for filling the compensation tank 25 via the rear fluid line 357, thereby advantageously allowing component costs to be lowered. In this device 401 the compensation tank 25 is filled once under atmospheric pressure with the Clausius-Rankine circuit 2 still cold until the minimum volume of working medium 4 is present in the compensation tank 25. The compensation tank 25 is then flushed with an inert filling gas 145 and sealed at the filling and venting port 29 with an appropriate closure (not illustrated here). When the Clausius-Rankine circuit 2 is started up, the liquid working medium 4 is first vaporized by means of the transferred waste heat in the vaporizers 7 and/or 9, thereby causing line system pressure to rise, particularly at the condenser outlet 21. If this is not desired, opening the shut-off valve 36 will allow liquid working medium 4 to flow into the compensation tank 25, thereby compressing the filling gas 145 present in the compensation tank 25. This results in a rise in compensation tank pressure. If the Clausius-Rankine circuit 2 is running, the additional shut-off valve 460 can be briefly opened to raise system pressure, and the shut-off valve 36 can be briefly opened to lower line system pressure, thereby allowing the supercooling level to be regulated, particularly in front of delivery pump 5. When the Clausius-Rankine circuit 2 is shut down, the shut-off valves 36 and 460 are preferably open, and the line system 3 can be flooded by working medium 4 from the compensation tank 25. In this case, the pressure level within the line system 3 and the compensation tank 25 decrease back to ambient pressure, thereby allowing a leakage caused by ambient air to be effectively prevented. In addition, the rear fluid connection 462 is situated downstream from the delivery pump 5 in a line elevation 463, thereby allowing any gas entering the line system 3 to be expelled into the compensation tank 25 when the shut-off valve 36 is open by means of a siphoning effect caused by said arrangement and then removed at the next filling procedure.

(22) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.