WO2021233521A1

WO2021233521A1 - A waste heat energy recovery system for an engine

Info

Publication number: WO2021233521A1
Application number: PCT/EP2020/063838
Authority: WO
Inventors: Bengt LASSESSON
Original assignee: Volvo Truck Corporation
Priority date: 2020-05-18
Filing date: 2020-05-18
Publication date: 2021-11-25

Abstract

The disclosure relates to a waste heat energy recovery system (1) for an engine (10), comprising: an operating medium to be circulated in the waste heat energy recovery system; an evaporator (2), the evaporator being configured to use waste heat energy from a cooling medium for the engine to evaporate the operating medium from liquid phase to gas phase; a steam powered engine (3) arranged in downstream fluid communication with the evaporator for receiving the operating medium in its gas phase; a condenser (4) arranged in downstream fluid communication with the steam powered engine for receiving the operating medium in its gas phase, the condenser being configured to condense the operating medium into its liquid phase; wherein the waste heat energy recovery system further comprises a fluid pump (5) which is arranged in downstream fluid communication with the condenser and arranged in upstream fluid communication with the evaporator, wherein the fluid pump is configured to pump the operating medium in its liquid phase to the evaporator. The disclosure further relates to a vehicle and to a method for recovering waste heat energy from an engine.

Description

A waste heat energy recovery system for an engine

TECHNICAL FIELD

The invention relates to a waste heat energy recovery system for an engine, to a vehicle and/or to a method for recovering waste heat energy from an engine.

The invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment. Although the invention will be described with respect to a heavy- duty truck, the invention is not restricted to this particular vehicle, but may also be used in other vehicles and vessels, such as other types of trucks, buses, construction equipment, and marine vessels.

BACKGROUND

An internal combustion engine (ICE) produces power for driving e.g. drive wheels of a truck. However, as is well known, the ICE also produces heat. It is therefore also known to for example use waste heat from the exhaust gases of the ICE to e.g. produce electricity which in turn may be used to drive other components in the truck, such as a radiator fan.

One example of a heat recovery system for an internal combustion engine may be found in US 2017/0122254 A1. It discloses an internal combustion engine heat energy recovery system where heat energy may be transferred from the exhaust gases, from the engine coolant and also from the engine oil.

However, there is still as strive towards further improving efficiency so that more waste heat energy can be re-used, and/or so that waste heat energy can be re-used in a more efficient manner.

SUMMARY

In view of the above, an object of the invention is to provide an improved waste heat energy recovery system for an engine, or at least to provide a useful alternative to known waste heat energy recovery systems. In particular, an object of the invention is to provide a waste heat energy recovery system in which waste heat energy from a cooling medium for the engine can be more efficiently re-used. Another object of the invention is to provide an improved vehicle and/or an improved method for recovering waste heat energy from an engine.

According to a first aspect of the invention, the object is achieved by a waste heat energy recovery system according to claim 1. According to a second aspect of the invention, the object is achieved by a vehicle according to claim 12. According to a third aspect of the invention, the object is achieved by a method according to claim 13.

According to the first aspect, the object is achieved by a waste heat energy recovery system for an engine, comprising: an operating medium to be circulated in the waste heat energy recovery system; an evaporator, the evaporator being configured to use waste heat energy from a cooling medium for the engine to evaporate the operating medium from liquid phase to gas phase; a steam powered engine arranged in downstream fluid communication with the evaporator for receiving the operating medium in its gas phase; a condenser arranged in downstream fluid communication with the steam powered engine for receiving the operating medium in its gas phase, the condenser being configured to condense the operating medium into its liquid phase. The waste heat energy recovery system further comprises a fluid pump which is arranged in downstream fluid communication with the condenser and arranged in upstream fluid communication with the evaporator, wherein the fluid pump is configured to pump the operating medium in its liquid phase to the evaporator.

By the provision of the waste heat energy recovery system as disclosed herein, waste heat energy in the engine’s cooling medium may be more efficiently re-used. In fact, it has been realized that by the configuration of the proposed waste heat energy recovery system, low quality heat from the engine may be better utilized for power generation, such as powering a radiator fan of a vehicle. By using a fluid pump which is configured to pump the operating medium in its liquid phase to the evaporator, less energy may be used for powering the fluid pump, implying improved efficiency. Less energy may for example be required in relation to if a pump was pumping the operating medium in its gas phase. More specifically, no, or almost no, volume difference will be present before and after the fluid pump since the operating medium in its liquid state is incompressible. Thereby a fluid pump requiring less power may be used. Furthermore, by the provision of the waste heat energy recovery system as disclosed herein, the operating medium may work at a lower temperature, such as below 250 degrees Celsius (°C). Hence, heat energy at a lower temperature may be efficiently used for power generation.

Optionally, the waste heat energy recovery system may further comprise a cooling medium treatment equipment configured to receive waste heat energy from the engine carried by the cooling medium for the engine. The waste heat energy recovery system may further be configured to transfer an amount of waste heat energy from the cooling medium to the evaporator which is equal to or below a predetermined threshold value. Thereby the amount of transferred waste heat energy may be efficiently controlled. Still optionally, the cooling medium treatment equipment may comprise a power limiter, such as a bypass valve, wherein the amount of waste heat energy transferred from the cooling medium to the evaporator is controlled by means of the power limiter so that the provided amount of waste heat energy is equal to or below the predetermined threshold value. For example, there may be a need to control the amount of energy generated by the steam powered engine. If for example the steam powered engine is powering an electric generator, the electric generator may have a maximum power limit. Additionally, or alternatively, the power limiter of the cooling medium treatment equipment may be used to ensure that the power generated from the steam powered engine is at an appropriate level for a given electric generator.

Optionally, the amount of available waste heat energy in the cooling medium may be limited by an allowed minimum temperature of the cooling medium during operation of the engine. As such, the waste heat energy recovery system may be configured so that the cooling medium’s temperature, after having passed the evaporator and/or the cooling medium treatment equipment, and before entering the engine, is equal to or above the allowed minimum temperature. In order for the engine to work properly, the cooling medium should not be too cold when entering the engine. For example, the evaporator and/or the above mentioned power limiter may be controlled and/or configured so that the cooling medium’s temperature before entering the engine, is equal to or above the allowed minimum temperature.

Typically, the cooling medium may be a fluid cooling medium such as a cooling liquid medium. Preferably, the cooling medium is at least one of engine coolant water and engine lubricant, such as engine oil. In fact, it has been realized that waste heat energy from the engine coolant water and/or from the engine lubricant can be efficiently utilized by the waste heat energy recovery system as disclosed herein for e.g. providing electrical and/or mechanical power.

Optionally, the cooling medium treatment equipment may further comprise a radiator for removing auxiliary waste heat energy from the cooling medium after waste heat energy from the cooling medium has been transferred to the evaporator. Thereby, in the event that there is waste heat energy left after the cooling medium has passed the evaporator, the radiator may be used to lower the temperature of the cooling medium, such as to the above mentioned allowed minimum temperature.

Optionally, the waste heat energy recovery system may be configured to operate at a temperature level of the operating medium which is 250 °C or less, such as 200 °C or less, for example at a temperature level within the temperature range of 60-200 °C. Hence, the system as disclosed herein may preferably be configured for utilizing low quality heat for power generation in an efficient manner.

Optionally, the operating medium may be any kind of operating medium which is suitable for heat transfer by use of phase transitions. For example, the operating medium may be any one of ethanol, pentane, propane, butane, liquefied petroleum gas (LPG), DiMethylEther (DME) etc.

Optionally, the waste heat energy recovery system may further comprise an accumulator tank for storing the operating medium in its liquid phase, wherein the accumulator tank is provided in-between and fluidly connects the condenser and the fluid pump.

Optionally, the steam powered engine may be any one of a turbine and a piston engine. Still optionally, the steam powered engine may be arranged to drive at least one of a generator for producing electrical power, a mechanical axle and a fan for a vehicle, such as a radiator fan.

Optionally, the waste heat energy recovery system may further be configured so that the operating medium in its liquid phase passes directly from the fluid pump to the evaporator. Thereby a simplified less complex, yet still efficient, system may be provided, implying improved cost-efficiency. According to the second aspect, the object is achieved by a vehicle comprising the waste heat energy recovery system according to any one of the embodiments of the first aspect of the invention.

Advantages and effects of the second aspect of the invention are largely analogous to the advantages and effects of the first aspect of the invention. It shall also be noted that all embodiments of the first aspect of the invention are applicable to and combinable with all embodiments of the second aspect of the invention and vice versa.

According to the third aspect, the object is achieved by a method for recovering waste heat energy from an engine by use of a waste heat energy recovery system according to any one of the embodiments of the first aspect. The method comprises:

- by use of waste heat energy from the cooling medium for the engine, evaporating the operating medium from liquid phase to gas phase by means of the evaporator;

- condensing the operating medium into its liquid phase by the condenser; and

- pumping the operating medium in its liquid phase to the evaporator by the fluid pump.

Advantages and effects of the third aspect of the invention are largely analogous to the advantages and effects of the first aspect of the invention. It shall also be noted that all embodiments of the first and second aspects of the invention are applicable to and combinable with all embodiments of the third aspect of the invention and vice versa.

Optionally, the method may further comprise driving at least one of a generator for producing electrical power, a mechanical axle and a fan for the vehicle, such as a radiator fan, by use of the steam powered engine.

Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples. In the drawings:

Fig. 1 shows a vehicle in the form of a truck according to an example embodiment of the present invention;

Fig. 2 is a schematic view of a waste heat energy recovery system according to an example embodiment of the present invention; and

Fig. 3 is a schematic view of another waste heat energy recovery system according to an example embodiment of the present invention.

The drawings show diagrammatic exemplifying embodiments of the present invention and are thus not necessarily drawn to scale. It shall be noted that some details in the drawings may be exaggerated in order to better describe and illustrate the invention. Like reference characters refer to like elements throughout the description, unless expressed otherwise.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Fig. 1 shows a vehicle in the form of a heavy-duty truck 100. The truck comprises an internal combustion engine 10, which here is a diesel engine, a transmission 11, a propulsion shaft 12 which is drivingly connected to driven wheels 13. Even though a truck is shown, it shall be understood that the invention as disclosed herein is not only limited to this type of vehicle, but may be used in any other type of vehicle, such as a bus, construction equipment etc. The invention may also be used in other applications, such as marine vessels. The engine from which waste heat energy is used may be any kind of engine which produces waste heat energy.

With respect to fig. 2, a schematic view of a waste heat energy recovery system 1 for an engine (not shown) according to an example embodiment of the first aspect of the invention is shown. The engine may for example be the engine 10 as shown in fig. 1. The waste heat energy recovery system 1 comprises an operating medium (not shown) to be circulated in the waste heat energy recovery system 1. The operating medium may be any kind of operating medium, such as ethanol, pentane, propane, butane, liquefied petroleum gas (LPG), DiMethylEther (DME) etc. The waste heat energy recovery system 1 also comprises an evaporator 2, wherein the evaporator 2 is configured to use waste heat energy from a cooling medium for the engine to evaporate the operating medium from liquid phase to gas phase. The used waste heat energy for evaporating the operating medium may for example correspond to a temperature decrease of about 5-15 °C or 5-10 °C of the cooling medium, such as about 8 °C.

The waste heat energy recovery system 1 further comprises a steam powered engine 3, which here is a turbine, arranged in downstream fluid communication with the evaporator 2 for receiving the operating medium in its gas phase. The steam powered engine 3 is driven by a pressure difference created in the system 1 during operation and generates power P for e.g. driving an electrical generator (not shown) of the vehicle 100. Furthermore, a condenser 4 is arranged in downstream fluid communication with the steam powered engine 3 for receiving the operating medium in its gas phase. The condenser 4 is configured to condense the operating medium into its liquid phase. The condenser 4 may be configured to use a cooling fluid, such as air, for condensing the operating medium into its liquid phase. As an alternative, or in addition, the condenser 4 may be cooled by water or by air boosted with water as an aerosol, or in any other suitable way recognized by the person skilled in the art.

The waste heat energy recovery system 1 further comprises a fluid pump 5 which is arranged in downstream fluid communication with the condenser 4 and arranged in upstream fluid communication with the evaporator 2, wherein the fluid pump 5 is configured to pump the operating medium in its liquid phase to the evaporator 2. In the shown embodiment, the waste heat energy recovery system 1 is configured so that the operating medium in its liquid phase passes directly from the fluid pump 5 to the evaporator 2. That is, the fluid pump 5 is in direct fluid communication with the evaporator 2, as illustrated in fig. 2. Passing directly from the fluid pump 5 to the evaporator 2 means herein that the operating medium does not pass any other member or element, except for the piping connecting the fluid pump 5 with the evaporator 2. The evaporator 2 as used herein may also be denoted as a boiler.

The waste heat energy recovery system 1 may further be configured to operate so that the operating medium is not provided below its dew point after it has passed the steam powered engine 3. In fact, according to an example embodiment, it has been found advantageous to configure the waste heat energy recovery system 1 to operate so that the operating medium is operating above the boiling point when exiting the steam powered engine 3 in order to avoid getting drops therein during operation.

The steam powered engine 3 is preferably arranged to drive at least one of a generator for producing electrical power, a mechanical axle and a fan for a vehicle, such as a radiator fan of the truck 100 as shown in fig. 1.

Furthermore, the waste heat energy recovery system 1 is preferably configured to operate at a temperature level of the operating medium which is 250 °C or less, such as 200 °C or less, for example at a temperature level within the temperature range of 60-200 °C. Thereby, low quality heat from the engine may be efficiently used for power generation. The expression “low quality heat” as used herein means thermal energy at low temperature, e.g. at a temperature of 110 °C and below, or 100 °C and below, or 95 °C and below, or 90 °C and below.

Fig. 3 shows a schematic view of another example embodiment of a waste heat energy recovery system 1, further comprising a cooling medium treatment equipment 6 configured to receive waste heat energy from an engine 10 carried by the cooling medium for the engine 10. The cooling medium treatment equipment 6 is also configured to transfer an amount of waste heat energy from the cooling medium to the evaporator 2 which is equal to or below a predetermined threshold value. This is accomplished in that the cooling medium treatment equipment 6 comprises a power limiter, in the form of a bypass valve 61. The amount of waste heat energy transferred from the cooling medium to the evaporator 2 is controlled by means of the power limiter 61 so that the provided amount of waste heat energy is equal to or below the predetermined threshold value. Hence, in the event the cooling medium is having a too high temperature, the bypass valve 61 can be opened so that cooling medium is also bypassing the evaporator 2. According to example embodiments, the predetermined threshold value may be fixed or it may be variable, depending on the maximum amount of energy required for the steam powered engine 3. Hence, the steam powered engine 3 may require different amounts of energy at different times during use.

Furthermore, the amount of available waste heat energy in the cooling medium is limited by an allowed minimum temperature of the cooling medium during operation of the engine 10. For example, the evaporator 2 and/or the power limiter 61 may be controlled and/or configured so that the cooling medium’s temperature before entering the engine 10 is equal to or above the allowed minimum temperature. As mentioned in the above, the cooling medium is preferably engine coolant water and/or engine lubricant for the engine 10. Engine lubricant may e.g. be engine oil.

As shown in fig. 3, the cooling medium treatment equipment 6 may further comprise a radiator 62 for removing auxiliary waste heat energy from the cooling medium after waste heat energy from the cooling medium has been transferred to the evaporator 2. Hence, if required, the cooling medium’s temperature may be further decreased after it has transferred heat energy to the evaporator 2. As shown in fig. 3 the radiator 62 is here arranged in-between the engine 10 and the evaporator 2. The radiator 62 may further be configured and/or controlled so that the cooling medium’s temperature before entering the engine 10, is equal to or above the allowed minimum temperature.

The cooling medium is preferably provided from the engine 10 and circulated by use of a cooling medium pump (not shown). The cooling medium, e.g. cooling water, may for example have a temperature of about 85-95 °C, such as 88 °C, when leaving the engine 10, where for example heat energy corresponding to a temperature decrease of about 8 °C, such as 5-10 °C, is transferred to the operating medium in the evaporator 2. The radiator 62 may further lower the temperature of the cooling medium, such as to about 80 °C, e.g. 75-85 °C. The radiator 62 may for example use ambient air for lowering the temperature of the cooling medium before it enters the engine 10. This temperature level of the cooling medium before it enters the engine 10 may in one example embodiment be the allowed minimum temperature as mentioned herein.

Furthermore, the waste heat energy recovery system 1 as shown in fig. 3 further comprises an accumulator tank 7 for storing the operating medium in its liquid phase. The accumulator tank 7 is provided in-between and fluidly connects the condenser 4 and the fluid pump 5. By use of the accumulator tank 7, the amount of the operating medium which is in gas phase may be varied. As such, the pressure level before the steam powered engine 3 may be varied, implying improved control of the power output P from the steam powered engine 3. The present invention also concerns a method for recovering waste heat energy from an engine 10 by use of a waste heat energy recovery system 1 as shown in e.g. figs. 2 and 3. The method comprises:

- by use of waste heat energy from the cooling medium for the engine 10, evaporating the operating medium from liquid phase to gas phase by means of the evaporator 2;

- condensing the operating medium into its liquid phase by the condenser 4; and

- pumping the operating medium in its liquid phase to the evaporator by the fluid pump 5.

The method may further comprise driving at least one of a generator (not shown) for producing electrical power, a mechanical axle (not shown) and a fan (not shown) for the vehicle 100, such as a radiator fan, by use of the steam powered engine 3.

It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

Claims

1. A waste heat energy recovery system (1) for an engine (10), comprising: an operating medium to be circulated in the waste heat energy recovery system; an evaporator (2), the evaporator being configured to use waste heat energy from a cooling medium for the engine to evaporate the operating medium from liquid phase to gas phase; a steam powered engine (3) arranged in downstream fluid communication with the evaporator for receiving the operating medium in its gas phase; a condenser (4) arranged in downstream fluid communication with the steam powered engine for receiving the operating medium in its gas phase, the condenser being configured to condense the operating medium into its liquid phase; characterized in that the waste heat energy recovery system further comprises a fluid pump (5) which is arranged in downstream fluid communication with the condenser and arranged in upstream fluid communication with the evaporator, wherein the fluid pump is configured to pump the operating medium in its liquid phase to the evaporator.

2. The waste heat energy recovery system according to claim 1, further comprising a cooling medium treatment equipment (6) configured to receive waste heat energy from the engine carried by the cooling medium for the engine, and further configured to transfer an amount of waste heat energy from the cooling medium to the evaporator which is equal to or below a predetermined threshold value.

3. The waste heat energy recovery system according to claim 2, wherein the cooling medium treatment equipment comprises a power limiter, such as a bypass valve (61), wherein the amount of waste heat energy transferred from the cooling medium to the evaporator is controlled by means of the power limiter so that the provided amount of waste heat energy is equal to or below the predetermined threshold value.

4. The waste heat energy recovery system according to any one of the preceding claims, wherein the amount of available waste heat energy in the cooling medium is limited by an allowed minimum temperature of the cooling medium during operation of the engine.

5. The waste heat energy recovery system according to any one of the preceding claims, wherein the cooling medium is at least one of engine coolant water and engine lubricant, such as engine oil.

6. The waste heat energy recovery system according to any one of claims 2-5, wherein the cooling medium treatment equipment further comprises a radiator (62) for removing auxiliary waste heat energy from the cooling medium after waste heat energy from the cooling medium has been transferred to the evaporator.

7. The waste heat energy recovery system according to any one of the preceding claims, configured to operate at a temperature level of the operating medium which is 250 °C or less, such as 200 °C or less, for example at a temperature level within the temperature range of 60-200 °C.

8. The waste heat energy recovery system according to any one of the preceding claims, further comprising an accumulator tank (7) for storing the operating medium in its liquid phase, wherein the accumulator tank is provided in-between and fluidly connects the condenser and the fluid pump.

9. The waste heat energy recovery system according to any one of the preceding claims, wherein the steam powered engine is any one of a turbine and a piston engine.

10. The waste heat energy recovery system according to any one of the preceding claims, wherein the steam powered engine is arranged to drive at least one of a generator for producing electrical power, a mechanical axle and a fan for a vehicle, such as a radiator fan.

11. The waste heat energy recovery system according to any one of the preceding claims, further configured so that the operating medium in its liquid phase passes directly from the fluid pump to the evaporator.

12. A vehicle (100) comprising the waste heat energy recovery system according to any one of claims 1-11.

13. A method for recovering waste heat energy from an engine by use of a waste heat energy recovery system according to any one of claims 1-11, the method comprising:

- by use of waste heat energy from the cooling medium for the engine, evaporating the operating medium from liquid phase to gas phase by means of the evaporator; - condensing the operating medium into its liquid phase by the condenser; and

14. The method according to claim 13, further comprising driving at least one of a generator for producing electrical power, a mechanical axle and a fan for the vehicle, such as a radiator fan, by use of the steam powered engine.