Rankine system with bypass valve

Abstract

The present invention relates to a Rankine system comprising a valve including a valve member. The valve member is provided with a valve controlling element in the form of an elongated tapered end portion with a tip end facing the duct, wherein the tapered end portion is arranged to be inserted through the opening and into the duct as the valve member is moved towards the valve seat. The actuator is configured to hold the valve member in at least one intermediate position between the first and second end positions, where the tapered end portion occupies a portion of a cross-sectional fluid through-flow area defined by the duct so as to partly restrict a flow of fluid through the duct.

Claims

1. A system of Rankine type for recovering waste heat of an internal combustion engine, wherein the system comprises: a closed loop for recirculating a fluid; a first heat exchanger configured to evaporate the fluid by transferring heat from a heated medium originating from the engine; an expander configured to expand the fluid that has been evaporated in the first heat exchanger and produce a power output; a second heat exchanger configured to condense the fluid by transferring heat to a flow of cooling medium; a pump for feeding the condensed fluid to the first heat exchanger; a bypass passage configured to allow the fluid to bypass the expander while recirculating in the system; and a bypass valve device arranged to control the flow through the bypass passage, wherein the bypass valve device comprises: a duct and a duct opening; a valve seat arranged circumferentially around the duct opening and facing away from the duct; a movable valve member for restricting a flow of fluid through the duct; and a valve actuator for moving the valve member, wherein the valve member and the valve actuator are arranged on an opposite side of the duct opening in relation to the duct, wherein the valve member is provided with a valve sealing element in the form of a sealing surface for sealing against the seat around the duct opening, wherein the valve member is movable towards and away from the duct opening in an axial direction thereof, wherein the valve seat and the sealing surface face each other in the axial direction so as to, when brought in contact with each other, define a first end position of the valve member in which the valve device is closed, wherein the valve member is movable between the closed first end position and a second end position in which the valve member sealing surface is located at an axial distance from the valve seat and the valve device is open; wherein the valve actuator is configured to move the valve member between the first and second end positions, wherein the valve member in addition to the valve sealing element is provided with a valve controlling element in the form of an elongated tapered end portion with a tip end facing the duct, wherein the tapered end portion is arranged to be inserted through the opening and into the duct as the valve member is moved towards the valve seat, and wherein the actuator is configured to be capable of holding the valve member in at least one intermediate position between the first and second end positions, in which intermediate position the tapered end portion occupies a portion of a cross-sectional fluid through-flow area defined by the duct so as to partly restrict a flow of fluid through the duct.

2. The system according to claim 1, wherein the actuator of said valve device is configured to be capable of holding the valve member in a plurality of intermediate positions between the first and second end positions, in which plurality of positions the tapered end portion occupies a varying portion of the cross-sectional through-flow area of the duct and thus to a different degree restricts a flow of fluid through the duct.

3. The system according to claim 1, wherein the actuator of said valve device is arranged to exert a linear force onto the valve member.

4. The system according to claim 1, wherein the actuator of said valve device comprises an electric motor.

5. The system according to claim 1, wherein the actuator of said valve device comprises a spring.

6. The system according to claim 1, wherein the actuator of said valve device is arranged at an end portion of the valve member opposite to the elongated tapered end portion.

7. The system according to claim 1, wherein the shape of the tapered end portion of said valve member in relation to the cross-sectional through-flow area of the duct is such that a certain linear movement of the valve member results in a smaller change of the duct's cross-sectional through-flow area when the valve member is close to its first end position than when the valve member is close to its second end position.

8. The system according to claim 1, wherein the shape of the tapered end portion of said valve member in relation to the cross-sectional through-flow area of the duct is such that, at least along half of the length of the tapered end portion in the axial direction thereof, the cross-sectional through-flow area varies substantially linearly with the axial position of the valve member.

9. The system according to claim 1, wherein the tapered end portion of said valve member has a conical shape.

10. The system according to claim 1, wherein the duct opening of said valve device faces an enclosed space, wherein the enclosed space is provided with a further opening allowing a fluid to, provided that the valve device is at least partly open, flow between the duct and the further opening via the duct opening and the enclosed space.

11. The system according to claim 1, wherein the heated medium originating from the engine is exhaust gas.

12. The system according to claim 1, wherein the fluid is ethanol.

13. The system according to claim 1, wherein the expander is connected to an electric generator for production of electricity or mechanically connected to the internal combustion engine.

14. A vehicle comprising an internal combustion engine and a system according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) In the description of the invention given below reference is made to the following figure, in which:

(2) FIG. 1 shows, in a schematic view, a Rankine system provided with a bypass valve.

(3) FIG. 2 shows a first embodiment of a valve device according to the invention.

(4) FIG. 3 shows a detail of a second embodiment of a valve device according to the invention.

(5) FIG. 4 shows an example of the dimensions of a tapered end portion of a valve member forming part of a valve device according to the invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

(6) FIG. 1 shows a system 1 of Rankine type for recovering waste heat of an internal combustion engine 2. The system 1 comprises a closed loop 3 for recirculating a fluid, which in this case is ethanol. The closed loop 3 is arranged so that the fluid can recirculate between the following components (in flow order): a first heat exchanger 4, an expander 5, a second heat exchanger 6, a pump 7 and back again to the first heat exchanger 4.

(7) The first heat exchanger 4 is arranged to evaporate the fluid by transferring heat from a flow of exhaust gas 8 originating from the engine 2. The expander 5 is arranged to expand the evaporated fluid delivered by the first heat exchanger 4 and produce a power output by driving a generator 9 that generates electricity, which can be supplied to the engine 4. The second heat exchanger 6 is arranged to condense the fluid by transferring heat from the fluid to a flow of cooling medium 10. The pump 7 is arranged to feed the condensed fluid to the first heat exchanger 4.

(8) A bypass passage 11 is arranged to allow the fluid to bypass the expander 5 while recirculating in the system 1. A bypass valve 12 is arranged to control the flow through the bypass passage 11.

(9) The bypass passage 11 is mainly used during a start-up phase of the system 1 to avoid that fluid in liquid form is fed to the expander 5, which might damage the expander 5, until a sufficient temperature and pressure has been established in the system.

(10) FIG. 2 shows a first embodiment of a valve device 120 suitable for forming the bypass valve 12 in the system 1 shown in FIG. 1. When the valve device 120 is open the fluid can pass the device 120 via the openings 21 and 22 that are in fluid communication via a duct 23, a duct opening 24 and an enclosed space 25.

(11) The valve device 120 further comprises: a valve seat 32 (see also FIG. 3) arranged circumferentially around the duct opening 24 and facing away from the duct 23, i.e. at least a portion the seat surface is located radially outside of the duct opening 24 and facing in general in an axial direction away from the duct 22; a movable valve member 26 for restricting a flow of fluid through the duct 23 and thus through the valve device 120; and a valve actuator 27 for moving the valve member 26, wherein the actuator 27 in this case comprises a spring 27a and an electric motor (not shown).

(12) The valve member 26 comprises in this case two parts: a main part located in the closed space 25 and an outer end part 26b mainly located in association with the actuator 27. The main part of the valve member 26 is axially movable in relation to the outer end part 26b. The spring 27a holds the two parts apart at a certain minimum nominal axial distance from each other. The main part of the valve member 26 can be pressed closer to the end part 26b by overcoming the force of the spring 27a. The end part 26b extends into the main part as indicated in FIG. 2 by a dashed line, an axially elongated opening 30a in the main part of the valve member 26, and a pin 30b that is fixed to the end part 26b and that is moveable along the opening 30a. In general the entire valve member 26, including the end part 26b and the spring 27a, moves as one unit. The valve device 120 is designed so that the spring 27a is somewhat compressed when the valve device 120 is closed (to protect the seat 32 from damage of a strong actuator/electric motor). The spring 27a may also be compressed by a high fluid pressure in the duct 23, in which case the valve can work as release valve.

(13) FIG. 2 also shows means 28 for adjusting the load of the spring and a bushing 29 for the valve member 26.

(14) The valve member 26 and the valve actuator 27 are arranged on an opposite side of the duct opening 24 in relation to the duct 23. The valve member 26 is provided with a valve sealing element in the form of a sealing surface 31 for sealing against the seat 32 around the duct opening 24. The sealing surface 31 has an annular shape. The valve member 26 is movable towards (to the left in FIG. 2) and away from (to the right in FIG. 2) the duct opening 24 in an axial direction thereof.

(15) The valve seat 32 and the sealing surface 31 are schematically depicted in FIG. 2; a part of the valve seat 32 is rounded while the sealing surface 31 is not. Typically, the shape of the seat 32 and the sealing surface 31 should be more adapted to each other; for instance, the seat 32 may be less rounded and the surface 31 may be somewhat rounded to match each other better. In an alternative both the seat 32 and the sealing surface 31 are flat. Such flat surfaces may be inclined in relation to a radial direction of the valve member 26.

(16) The valve seat 32 and the matching sealing surface 31 of the valve member 26 face each other in the axial direction so as to, when brought in contact with each other, define a first axial end position of the valve member 26 in which the valve device 120 is closed. This closed end position is indicated with dashed lines in FIG. 2. The valve member 26 is movable between the closed first end position and a second end position in which the valve member sealing surface 31 is located at an axial distance from the valve seat 32 and the valve device 120 is open. This open second end position is shown with solid lines in FIG. 2. The valve actuator 27, i.e. the electric motor in this case, is configured to move the valve member 26 in the axial direction between the first and second end positions.

(17) The valve member 26 is, in addition to the valve sealing element 31, provided with a valve controlling element in the form of an elongated tapered end portion 33 with a tip end 34 facing the duct 23, i.e. away from the other parts of the valve member 26, away from the actuator 27, and in the opposite end in relation to the outer end part 26b. The tapered end portion 33 is arranged to be inserted through the opening 24 and into the duct 23 as the valve member 26 is moved towards the valve seat 32. The size and shape of the tapered end portion 33 is thus such that it fits into the duct 23 and it is located onto the valve member 26 in such a way as to be inserted through the opening 24 and into the duct 23 as the valve member 26 is moved towards the valve seat 32.

(18) The actuator 27, i.e. the electric motor, is also configured to be capable of holding the valve member 26 in at least one intermediate position between the first and second end positions, i.e. in a position somewhere in between the two axial positions indicated in FIG. 2. In this intermediate position the tapered end portion 33 occupies a portion of a cross-sectional fluid through-flow area defined by the duct 23 so as to partly restrict a flow of fluid through the duct 23.

(19) In this example the electric motor of the actuator 27 is further configured to be capable of holding the valve member 26 in a plurality of intermediate positions between the first and second end positions, in which plurality of positions the tapered end portion 33 occupies a varying portion of the cross-sectional through-flow area of the duct 23 and thus to a different degree restricts a flow of fluid through the duct 23.

(20) The actuator 27 is arranged to exert a linear force onto the valve member 26 and the actuator 27 is arranged at an end portion of the valve member 26 opposite to the elongated tapered end portion 33. Electric motors, pistons etc. for the purpose of holding the valve member 26 in a plurality of axial positions are known as such. The spring 27a exerts a force onto the main part of the valve member 26 that is directed towards the valve seat 32. Such a spring arrangement for valves is also known as such.

(21) In the examples shown here the duct 23 has a circular cross section and the elongated tapered end portion 33 has a circular conical shape. In FIG. 2 the schematically depicted end portion 33 has a frusto-conical shape. In FIG. 3 the slant angle of the conical end portion 33 is not the same over the entire axial length of the end portion 33.

(22) FIG. 3 shows a detail of a second embodiment of a valve device 120 according to the invention. The same reference numbers are used in FIGS. 2 and 3 for the same or similar details.

(23) FIG. 3 shows the valve device 120 in a closed position, i.e. the valve member 26 is in its closed first axial end position. The valve seat 32 comprises in this case a flat annular surface that extends circumferentially around the opening of the duct 23 and faces in the axial direction. An annular protrusion 37 is arranged in the valve seat 32. The sealing surface 31 on the valve member 26 matches the seat 32. The sealing surface 31 comprises an annular cut-out provided with a sealing 36 positioned to press against the protrusion 37 when the valve device 120 is closed. The annular sealing 36 is made of PTFE (polytetrafluororethylene) or other suitable material that can adapt to the shape of the protrusion 37 and provide for a good seal.

(24) The tapered end portion 33 has a base 35 with a diameter nearly the same as the inner diameter of the duct 23 so as to contribute to the closing of the valve device 120.

(25) FIG. 4 shows an example of suitable dimensions of a tapered end portion 33 and a duct 23 similar to what is shown in FIG. 3. Solid line 40 in FIG. 4 represents an inner wall of the duct 23 and dashed line 41 represents one of the sides of the tapered end portion 33. The x-axis is aligned with a longitudinal centre axis of the end portion 33 (and of the valve member 26) so what is shown in FIG. 4 is a form of representation of a side view of a(n upper) half of the duct 23. The unit on the y-axis is mm and it can be seen that the duct 23 has in this example a radius of 3 mm (and thus a diameter of 6 mm).

(26) The unit on the x-axis is percent of the cross-sectional through-flow area of the duct 23 that is non-obstructed by the end portion 33 and thus available for fluid through-flow at a certain radius (or diameter) of the end portion 33 given by dashed line 41. Another way to say this is that dashed line 41 gives the radius of the end portion 33 to obtain a certain reduced cross-sectional through-flow area of the duct 23, which gives a corresponding reduction of the flow through the duct 23 when the valve is used in for instance the system of FIG. 1.

(27) As an example, if the end portion 33 is inserted only a little into the duct 23 so that the radius of the inserted section is only 1 mm, the free through flow area in the duct is 90% of the nominal value (i.e. the maximum value when the end portion 33 is not located in the duct 23 at all and the valve is fully open). As another example, a reduction of the nominal value of the cross-sectional area to 50% is obtained if the radius of the inserted section is around 2 mm. If the entire end portion 33 is inserted into the duct 23, which corresponds to the closed first end position of the valve member 26, the free through-flow area is close to 0%.

(28) The x-axis in FIG. 4 also implicitly shows the axial length of the tapered end portion 33, which in this example is around 8 mm. As a general rule, the length of the tapered portion 33 should be greater than the diameter of the duct 23, at least when each of the duct 23 and the end portion 23 has a circular cross-section.

(29) FIG. 4 further shows that the slant angle of the tapered end portion 33 is substantially constant between 100% and around 90% as well as between around 85% and 0%, i.e. the dashed line 41 is substantially straight in these two intervals. An effect of this is that, within each of these two intervals, the cross-sectional through-flow area of the duct 23 varies substantially linearly with the axial position of the valve member 26. Further, in the interval 100-90%, i.e. at the tip end of the end portion 33, the slant angle is larger than in the interval 85-0%. An effect of this is that a certain linear movement of the valve member 26 results in a smaller change of the duct's 23 cross-sectional through-flow area when the valve member 26 is close to its first end position than when the valve member 26 is close to its second end position.

(30) The invention is not limited by the embodiments described above but can be modified in various ways within the scope of the claims. For instance, the valve seat and the sealing surface of the valve member can have other shapes than exemplified above. Further, the expander does not necessarily have to produce electricity as power output but may instead be mechanically connected to the internal combustion engine using gears or belt drive.