WO2021180999A1

WO2021180999A1 - Apparatus for converting heat energy to mechanical shaft output

Info

Publication number: WO2021180999A1
Application number: PCT/FI2020/050155
Authority: WO
Inventors: Petteri Mikko Samuli Penttinen
Original assignee: 21Tdmc Group Oy
Priority date: 2020-03-11
Filing date: 2020-03-11
Publication date: 2021-09-16

Abstract

This invention relates to an apparatus for converting heat energy to mechanical shaft output, which apparatus comprises a main body (1 ) having a rotor chamber (5) for a rotary rotor (6) with a group of vanes (7) and a rotary shaft (9), which rotor (6) is arranged to be rotated by a working fluid in the rotor chamber (5). The input of heat to the working fluid and output of heat from the working fluid are implemented by a phase transition. The main body (1) comprises a heated compartment (2) and a cooled compartment (3) and the rotor chamber (5) is placed between the mentioned compartments (2 and 3).

Description

APPARATUS FOR CONVERTING HEAT ENERGY TO MECHANICAL SHAFT OUTPUT

The present invention relates to an apparatus for converting heat energy to me chanical shaft output as defined in the preamble of claim 1.

The apparatus according to the invention converts heat or thermal energy to me chanical energy, preferably such as a shaft power or shaft output. Thus, the ap paratus according to the invention is a type of heat engine, more specifically an external heat engine because the heat energy for the apparatus is brought from outside the apparatus. In the apparatus itself no combustion reaction exists.

The apparatus according to the invention is suited very well for instance in con nection with a heater of a caravan or trailer from which heater the apparatus gets the needed heat for converting the heat to mechanical shaft output. When, for instance, a generator is connected to the output shaft of the apparatus the appa ratus produces electrical energy when the heater is switched on. The batteries of the caravan can be charged with the so produced electrical energy. Thus, the batteries do not discharge during the heating. Another advantageous example is to use the apparatus according to the invention for converting waste heat of ex haust gases of motor vehicles to electrical energy. The arrangement may be im plemented so that in that case the alternator of the vehicle does not load the mo tor of the vehicle, which leads to decreasing carbon dioxide emissions.

In prior art various solutions for converting heat energy to mechanical energy are known. Traditionally, in thermal power stations heat energy is converted to elec tric power. However, these are huge entities, permanently built at their locations and are not suited to small-scale use.

Also, thermal power stations based on the Organic Rankine Cycle (ORC) tech nology converts heat energy to electric power. The ORC technology uses an or- ganic fluid that has the boiling point at a lower temperature than the water. The heat is converted into useful work, that can further be converted into electricity. ORC power stations can be smaller than traditional thermal power stations, but they are still too large for small-scale use. In addition, their structure is complicat ed, the efficiency is low and mainly the installations work only in large units and when the temperature difference is more than 200 °C. Also, the scalability of the ORC power stations is rather poor.

In the prior art a thermoelectric generators (TEG) are also known. TEG generator is based on a so-called Seebeck effect and converts heat energy directly into electrical energy. Thus, they function like heat engines. Thermoelectric genera tors could be used in power plants to convert waste heat into electrical power and in automobiles as thermoelectric generators (ATGs) to increase fuel efficiency. However, thermoelectric generators are typically rather expensive, and their effi ciency is low, and the power output is poor.

The object of the present invention is to eliminate the drawbacks described above and to achieve a reliable, economical, simple and efficient apparatus for convert ing heat energy to mechanical shaft output or electrical energy. Another object of the invention is to achieve an apparatus for converting heat energy to mechanical shaft output or electrical energy which apparatus is small in its size and is suita ble also for small-scale use. The apparatus for converting heat energy to me chanical shaft output according to the invention is characterized by what is pre sented in the characterization part of claim 1. Other embodiments of the invention are characterized by what is presented in the other claims.

An aspect of the invention is to provide an apparatus for converting heat energy to mechanical energy, preferably to mechanical shaft output, which apparatus comprises a main body having a rotor chamber for a rotary rotor with a group of vanes and a rotary shaft, which rotor is arranged to be rotated by a working fluid in the rotor chamber. Advantageously, the input of heat to the working fluid and output of heat from the working fluid are implemented by a phase transition.

The apparatus according to the invention has significant advantages over the solutions of the prior art. For instance, the coefficient of efficiency is much bigger than with the prior art solutions. One advantage is that the apparatus according to the invention works also in low temperature differences. Electrical energy can be produced from warm air or water the temperature of which is between about 40 - 200 °C. A further advantage is that the structure of the apparatus is economical and simple, and the size of the apparatus can be small. Yet a further advantage is that the scalability of the apparatus is good. The apparatus according to the invention can produce mechanical shaft output in the area of about 50 W - 50 kW with very low temperature differences. In the following, the invention will be described in detail by the aid of examples by referring to the attached simplified and diagrammatic drawings, wherein

Fig. 1 presents in a front view a main body of an apparatus according to the invention partially cross-sectioned and a cover piece removed, Fig. 2 presents in a side view and in a simplified and diagrammatic way a main body of an apparatus according to the invention cross-sectioned and main parts separated from each other,

Fig. 3 presents in a simplified and diagrammatic way a working cycle of an apparatus according to the invention, Fig. 4 presents in a front view and in a simplified and diagrammatic way and cross-sectioned another embodiment of the apparatus according to the invention,

Fig. 5 presents in a front view and in a simplified and diagrammatic way and cross-sectioned and shortened yet another embodiment of the appa ratus according to the invention, and Fig. 6 presents in a front view and in a simplified and diagrammatic way and cross-sectioned an enlarged detail of the embodiment of Fig. 5.

The basic idea of the present invention is to achieve an apparatus to produce mechanical shaft power or shaft output from heat energy. Preferably, the heat energy used may be waste heat from various sources, and advantageously the produced shaft power may be converted into electrical energy. In the apparatus the heat transfer is improved by a phase transition. In that case even from small temperature differences may be recovered a significant energy density as a work for the rotor of the apparatus. The fluid used may be liquid or gaseous and both the states may be alone or together to produce work from heat energy by their thermal expansion.

Figure 1 and 2 present a main body 1 of an apparatus according to the invention with its main components. Figure 1 presents in a front view a main body 1 of an apparatus according to the invention partially cross-sectioned and a cover piece 1a removed, and Figure 2 presents in a side view and in a simplified and dia grammatic way a main body 1 of an apparatus according to the invention cross- sectioned and the main parts separated from each other.

The apparatus comprises the main body 1 or a frame that is preferably a one- piece unit and made of well heat conducting material, for instance aluminum. The main body 1 comprises at least two compartments or halves, a heated compart ment 2 on the heat side of the main body 1 and a cooled compartment 3 on the cool side of the main body 1. Between the mentioned compartments 2 and 3 the body comprises thermal barriers 4 that are arranged to reduce a conducting heat flow between the compartments 2 and 3. Further, the apparatus comprises a ro tor 6 with a group of vanes 7, a rotary shaft 9 and a bearing 11 on each side of the rotor 6. The structure of the rotor 6 with the vanes 7 is substantially similar to the structure of the rotors in commonly known vane pumps. Preferably, the rotor 6 is made of material that does not conduct heat. The rotary shaft 9 act as the output shaft of the apparatus when the mechanical shaft output or power is taken from the apparatus.

The main body 1 further comprises a cavity that acts as a rotor chamber 5 for the rotary rotor 6 with the vanes 7. In this embodiment the rotor chamber 5 is closed by its sides. In addition, the rotor chamber 5 has a group of substantially parallel grooves 8 on both of its sides, which grooves 8 extend sideways outwards from the rotor chamber 5 to increase the heat exchange surface of the main body 1 and thus to improve thermal conductivity. The shape and number of grooves 8 are preferably similar in both the compartments 2 and 3. The shape of the rotor chamber 5 is oval, more or less like a shape of a stadium or obround having a long axis and a short axis perpendicular to the long axis. Preferably, the shape of the rotor chamber 5 has at least one axis of symmetry, and preferably this axis is the longer axis of the two axes of the oval or obround. The heat side of the main body 1 is also the heat side of the rotor chamber 5 and the cool side of the main body 1 is also the cool side of the rotor chamber 5.

Preferably, the apparatus has the circular rotor 6 rotating inside the rotor chamber 5 that is larger than the rotor 6. The centers of the rotor 6 and the rotor chamber 5 are offset, causing eccentricity. The center of the rotor 6 is on the axis of sym metry of the rotor chamber 5 but closer the first end of the rotor chamber 5 than the second end of the rotor chamber 5.

The vanes 7 are allowed to slide inwards and outwards in the body of the rotor 6 and seal all edges, creating vane chambers that do the pumping work. Thinking the direction of the revolution of the rotor 6, on the heated compartment 2 side of the main body 1, the rotor chamber 5 is increasing in volume. Correspondingly, on the cooled compartment 3 side of the main body 1 , the rotor chamber 5 is de creasing in volume, forcing the condensed working fluid in the rotor chamber 5 to the heat side of the main body 1 through the small gap between the body of the rotor 6 and the first end of the rotor chamber 5. Because of the eccentricity or offset of the rotor shaft 9 the gap between the body of the rotor 6 and the first end of the rotor chamber 5 is smaller than the gap between the body of the rotor 6 and the second end of the rotor chamber 5.

Further the main body comprises a filling hole 1b connected to the rotor chamber 5. The filling hole 1b is for filling the working fluid and lubricant into the rotor chamber 5. Preferably the working fluid is liquid that vaporizes in the rotor cham ber 5 when heated and condenses back to liquid when cooled.

As mentioned above the main body 1 is preferably a one-piece unit. The bottom of the rotor chamber 5 forms a first end wall 1c for the rotor chamber 5. Prefera bly the end wall 1c comprises a first bearing housing 1d for the first bearing 11 of the rotor 6. Preferably the cover piece 1a comprises a second bearing housing 1e for the second bearing 11 of the rotor 6. The cover piece 1a also comprises a seal 13 to seal the output end of the rotor shaft 9 which extends out from the rotor chamber 5. The rotor chamber 5 is tightly closed with the cover piece 1a using for instance fastening elements 14, such as screws that are fastened into the fas tening holes 10 of the main body 1. The cover piece 1a forms a second end wall for the rotor chamber 5.

On the outer side section of the heated compartment 2 the main body 1 has a first heat exchange surface 2a and on the outer side section of the cooled com partment 3 the main body 1 has a second heat exchange surface 3a. The heat exchange surfaces 2a and 3a are treated so that an external heat source and/or an external cooling source can be fastened onto the surface 2a and 3a with a good thermo-conductive contact. The contact may be improved for instance with a thermal paste. The external heat source may preferably be for instance a water- based heat element or a heat profile made of aluminum. The external heat source may also be a source of waste heat energy, for instance an exhaust pipe of a vehicle. Correspondingly, an external cooling source may be a cooling profile made of aluminum. Figure 3 presents in a simplified and diagrammatic way a working cycle of an ap paratus according to the invention by illustrating a revolution of the rotor 6. When the heated compartment 2 is heated the working fluid in the heated side of the rotor chamber 5 heats up and its volume expanses because of the heat expan sion. The heat expansion of the working fluid, which in this phase is mainly the heat expansion of the liquid, makes work and makes the rotor 6 to rotate counter clockwise about in a area between 180° - 200° because the eccentric shape of the rotor chamber 5 forms an enlarging volume. In the area of about 200° - 310° the rotor chamber 5 comprises a heat exchange area with the grooves 8 which increase the heat exchange surface area. In that angle area the working fluid boils. So, in that area the state of the working fluid changes from liquid to gase ous. The phase transition takes place. The boiling of the working fluid also produces pressure. Between 310° - 40° is a so-called intensive area where the pressure created on the heated side of the rotor chamber 5 is focused to the vanes 7 which pressure pushes the vanes 7 towards the cool side of the main body 1 where the pressure in the rotor chamber 5 is lower. Thus, the rotor 6 gets torque also from the gas pressure and continues its rotary motion counterclockwise. In the area of the cool side about between 40° - 140° the gas cools down and condenses. When the rotor 6 continues its rotation the vanes 7 move the condensed liquid back to the heated side of the main body through the gap under the rotor 6 about in the area between 140° - 180°. Thus, the work cycle closes and begins again from the beginning. The work produced can be obtained from the rotor shaft 9. The rotor 6 acts at the same time as an element to produce work and also as a pump to return the condensed liquid back to the heat side of the rotor chamber 5.

During one revolution of the rotor 6 the working fluid as being liquid is arranged to be heated in the heat side of the rotor chamber 5 and cooled in the cool side of the rotor chamber 5 so that the phase transition takes place twice. Figure 4 presents in a front view and in a simplified and diagrammatic way and cross-sectioned another embodiment of the apparatus according to the invention. In this structure the rotor chamber 5 is not closed but the main body 1 comprises one or more first apertures 16 on its side of the heated compartment 2 and one or more second apertures 17 on its side of the cooled compartment 3. Each first aperture 16 connects the rotor chamber 5 to a heat chamber 18 that is fastened to the heat exchange surface 2a of the heated compartment 2. Correspondingly, each second aperture 17 connects the rotor chamber 5 to a cooling chamber 19 that is fastened to the heat exchange surface 3a of the cooled compartment 3.

The outer surfaces of the heat chamber 18 and the cooling chamber 19 are heat exchange surfaces 20 that are treated so that an external heat source and/or an external cooling source can be fastened onto the outer surfaces 20 with a good thermo-conductive contact. The contact may be improved for instance with a thermal paste. The heat exchange may be further improved with grooves 21 on the inner surfaces of the chambers 18 and 19 which grooves 21 enlarge the heat exchange surface area. The structure of the solution according to Figure 4 makes it possible to have considerably large heat exchange surface areas.

The heat chamber 18 comprises working fluid 18a that is arranged to boil in the heat chamber 18 caused by the heat directed to the outer surfaces 20 of the heat chamber 18. The gas released from the boiling working fluid 18a flows through each first aperture 16 to the rotor 6 making the rotor 6 rotate substantially in a similar way as described in the connection with the solution according to Figures

1 and 2. The rotor 6 moves the gas through each second aperture 17 into the cooling chamber 19 where the gas condenses back to liquid which returns down through each second aperture 17 into the rotor chamber 5 from where the rotor 6 pumps the liquid back into the heat chamber 18 through each first aperture 16. The working principle of the rotor 6 of this embodiment is substantially similar as described in the connection with the solution according to Figures 1 and 2. The apparatus according to this embodiment is intended to work in a vertical position, as presented in Figure 4.

Figures 5 and 6 present yet another embodiment of the apparatus according to the invention. Figure 5 presents this embodiment in a shortened front view and in a simplified and diagrammatic way and cross-sectioned. Figure 6 presents an enlarged detail of the embodiment of Figure 5. In this embodiment the structure and use of the heat chamber 18 and cooling chamber 19 are substantially the same as in the embodiment according to Figure 4. Only the main body 1 and its components are different and the way to return the working fluid as liquid into the heat chamber 18 differs from the embodiments described above.

The main body 1 in Figure 5 is substantially one entity and cross-sectioned in two different levels which partially overlap each other. For that reason, the cross- section lines are not shown. The first level of the cross-section is substantially in the middle of the rotor chamber 5 and the second level of the cross-section is in front of the first level, closer to the viewer, substantially in the middle of the pump arrangement 23 of the main body 1. Also, all the bores, channels and apertures are shown their ends open into the heat chamber 18 and cooling chamber 19.

The main body 1 comprises the rotor chamber 5 that may now be smaller than in the embodiments mentioned above. Also, the rotor 6 is smaller and rotates faster. The rotor chamber 5 is connected to the heat chamber 18 with at least one aper ture 16a that is preferably a round bore. Further, rotor chamber 5 is connected to the cooling chamber 19 with at least one aperture 17a that is preferably also a round bore. In addition, rotor chamber 5 may be connected to the cooling cham ber 19 with a second aperture 17b that acts as a breather channel.

The main body 1 also comprises a pump arrangement 23 that further comprises a rod 12 acting as a piston, a spring element 25 and spring-loaded check valves 27 and 28. In Figure 5 all the components of the pump arrangement 23 are on the second level of the cross-section and the rod 12 with its actuator, an eccentric element 22, overlaps the first level of the cross-section.

In this embodiment the eccentric element 22 is such like a cam and is connected to the rotor shaft 9 outside the rotor chamber 5. The eccentric element 22 is ar ranged to push the rod 12 acting as a piston at its first end in every revolution of the rotor 6. The spring element 25 is arranged to push the rod 12 at its second end back towards the eccentric element 22. The rod 12 is placed in a channel 24 that is connected to the rotor chamber 5. Preferably the channel 24 is a round bore. The spring 25 is in the space 26 between the second end of the rod 12 and the end of the channel 24. The volume of the space 26 varies according to the position of the rod 12. The variable volume space 26 is connected to the heat chamber 18 through the spring-loaded check valve 27 that allows the work fluid to flow only into the heat chamber 18. Further, the space 26 is also connected to the cooling chamber 19 through the spring-loaded check valve 28 that allows the work fluid to flow only out from the cooling chamber 19. The rod 12, spring 25 and the check valves 27, 28 with the rotor 6 act as the pump arrangement 23 to pump condensed work fluid from the cooling chamber 19 into the heat chamber 18 in every revolution of the rotor 6.

The basic idea of the present invention is to achieve an apparatus, such as a heat engine which produces mechanical shaft power from heat energy that can come from various sources. The rotor arrangement with all necessary channels, valves and pumping mechanisms may comprise a structure of any vane type mo tor or pump.

The working fluid is preferably liquid that is converted to gas that is again con densed to liquid. Preferably, the apparatus utilizes during the same working cycle both thermal expansion of gas and thermal expansion of liquid. The efficiency of the apparatus is increased by this way. The apparatus may also be used only by thermal expansion of gas or by thermal expansion of liquid. The rotor 6 is ar- ranged to produce work and to act simultaneously as a pump for the circulation process. The input and output of heat is implemented by a phase transition which makes very small size of the apparatus possible. It is obvious to the person skilled in the art that the invention is not restricted to the examples described above but that it may be varied within the scope of the claims presented below. Thus, for example, instead the rotor arrangements men tioned above all other vane type rotor arrangements may be used. It is also obvious to the person skilled in the art that the rotor may be different from what is described above. The rotor, for instance, may comprise flexible vanes which do not move in and out but bend when the distance to the inner wall of the rotor chamber decreases and straighten again when the distance to the inner wall of the rotor chamber increases. Also, the rotor itself may be made of a rubber-like material.

Claims

1. Apparatus for converting heat energy to mechanical shaft output, which appa ratus comprises a main body (1) having a rotor chamber (5) for a rotary rotor (6) with a group of vanes (7) and a rotary shaft (9), which rotor (6) is arranged to be rotated by a working fluid in the rotor chamber (5), characterized in that the input of heat to the working fluid and output of heat from the working fluid is imple mented by a phase transition.

2. Apparatus for converting heat energy to mechanical shaft output according to claim 1, characterized in that the main body (1) comprises a heated compart ment (2) and a cooled compartment (3) and the rotor chamber (5) is placed be tween the mentioned compartments (2 ) and (3).

3. Apparatus for converting heat energy to mechanical shaft output according to claim 2, characterized in that the rotor chamber (5) is in a longitudinal position between the heated compartment (2) and the cooled compartment (3).

4. Apparatus for converting heat energy to mechanical shaft output according to claim 2 or 3, characterized in that between the heated compartment (2) and the cooled compartment (3) the main body (1) comprises thermal barriers (4) that are arranged to reduce a conducting heat flow between the mentioned compartments (2) and (3).

5. Apparatus for converting heat energy to mechanical shaft output according to any of the claims above, characterized in that the shape of the rotor chamber (5) is substantially oval, advantageously like an obround having a long axis and a short axis perpendicular to the long axis, and that the rotor (6) is placed to rotate on the long axis of the rotor chamber (5) closer to the first end of the rotor cham- ber (5) than the second end of the rotor chamber (5).

6. Apparatus for converting heat energy to mechanical shaft output according to any of the claims above, characterized in that the rotor chamber (5) comprises a group of substantially parallel grooves (8) on both of its sides, which grooves (8) extend sideways outwards from the rotor chamber (5) to increase the heat ex change surface of the main body (1) and thus to improve thermal conductivity.

7. Apparatus for converting heat energy to mechanical shaft output according to any of the claims above, characterized in that the rotor chamber (5) is substan tially closed, and that the main body (1) comprises a closable filling hole (1b) connected to the rotor chamber (5), which filling hole (1b) is for filling the working fluid into the rotor chamber (5).

8. Apparatus for converting heat energy to mechanical shaft output according to any of the claims above, characterized in that the working fluid is liquid that is arranged to be heated in the heat side of the rotor chamber (5) and cooled in the cool side of the rotor chamber (5) so that the phase transition takes place twice during one revolution of the rotor (6).

9. Apparatus for converting heat energy to mechanical shaft output according to claim 8, characterized in that the rotor (6) is arranged to be rotated by thermal expansion of both gas and liquid.

10. Apparatus for converting heat energy to mechanical shaft output according to any of claims 1 - 5 above, characterized in that the main body (1) comprises one or more first apertures (16, 16a) on its heat side and one or more second apertures (17, 17a) on its cool side, each first aperture (16, 16a) connecting the rotor chamber (5) to a heat chamber (18) that is fastened to the heat side of the main body (1), and each second aperture (17, 17a) connecting the rotor chamber (5) to a cooling chamber (19) that is fastened to the cool side of the main body (1 )·

11. Apparatus for converting heat energy to mechanical shaft output according to claim 10, characterized in that the inner surfaces of the chambers (18) and (19) are equipped with grooves (21) to enlarge the heat exchange surface area.

12. Apparatus for converting heat energy to mechanical shaft output according to claim 10 or 11, characterized in that the heat chamber (18) comprises working fluid (18a) in a liquid state which working fluid (18a) is arranged to boil in the heat chamber (18) caused by the heat directed to the one or more outer surfaces (20) of the heat chamber (18), and that the vaporized working fluid as gas is arranged to flow through each first aperture (16) to the rotor (6) making the rotor (6) rotate and move the gas through each second aperture (17) into the cooling chamber (19) where the gas is arranged to condense back to liquid which is arranged to return down through each second aperture (17) into the rotor chamber (5) from where the rotor (6) is arranged to pump the liquid back into the heat chamber (18) through each first aperture (16).

13. Apparatus for converting heat energy to mechanical shaft output according to any of claims 1 - 5 or 10 or 11 above, characterized in that the main body (1) comprises a pump arrangement (23) activated by the rotary shaft (9) of the rotor (6) to pump the condensed work fluid from the cooling chamber (19) into the heat chamber (18).

14. Apparatus for converting heat energy to mechanical shaft output according to any of the claims above, characterized in that the on the outer side section of the heated compartment (2) the main body (1) has a first heat exchange surface (2a) and on the outer side section of the cooled compartment (3) the main body (1) has a second heat exchange surface (3a), and that the outer surfaces of heat chamber (18) and cooling chamber (19) have heat exchange surfaces (20), which heat exchange surfaces (2a, 3a, 20) are treated so that an external heat source and/or an external cooling source can be fastened onto each heat exchange sur- face (2a, 3a, 20) with a good thermo-conductive contact, preferably the contact may be improved with a thermal paste.

15. Apparatus for converting heat energy to mechanical shaft output according to any of the claims above, characterized in that the working fluid is liquid that is arranged to vaporize when heated and to condense back to liquid when cooled.

16. Apparatus for converting heat energy to mechanical shaft output according to any of the claims above, characterized in that the main body (1) is preferably a one-piece unit and made of well heat conducting material, for instance aluminum, and that the rotor (6) is made of material that does not conduct heat.