CN109611170B - Waste heat recovery system for free piston expander-linear generator vehicle based on composite power supply - Google Patents
Waste heat recovery system for free piston expander-linear generator vehicle based on composite power supply Download PDFInfo
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- CN109611170B CN109611170B CN201811292611.2A CN201811292611A CN109611170B CN 109611170 B CN109611170 B CN 109611170B CN 201811292611 A CN201811292611 A CN 201811292611A CN 109611170 B CN109611170 B CN 109611170B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K23/00—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids
- F01K23/02—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled
- F01K23/06—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle
- F01K23/065—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle the combustion taking place in an internal combustion piston engine, e.g. a diesel engine
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01B—MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES
- F01B11/00—Reciprocating-piston machines or engines without rotary main shaft, e.g. of free-piston type
- F01B11/009—Reciprocating-piston machines or engines without rotary main shaft, e.g. of free-piston type in which the movement in two directions is obtained by two or more double acting piston motors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01B—MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES
- F01B21/00—Combinations of two or more machines or engines
- F01B21/02—Combinations of two or more machines or engines the machines or engines being all of reciprocating-piston type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01B—MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES
- F01B23/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
- F01B23/10—Adaptations for driving, or combinations with, electric generators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
- F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
- F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
- F01K25/10—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours the vapours being cold, e.g. ammonia, carbon dioxide, ether
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
- H02K7/18—Structural association of electric generators with mechanical driving motors, e.g. with turbines
- H02K7/1869—Linear generators; sectional generators
- H02K7/1876—Linear generators; sectional generators with reciprocating, linearly oscillating or vibrating parts
- H02K7/1884—Linear generators; sectional generators with reciprocating, linearly oscillating or vibrating parts structurally associated with free piston engines
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/64—Electric machine technologies in electromobility
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
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- Power Engineering (AREA)
- Engine Equipment That Uses Special Cycles (AREA)
- Hybrid Electric Vehicles (AREA)
Abstract
A free piston expander-linear generator vehicle waste heat recovery system based on a composite power supply system belongs to the field of energy conservation and emission reduction. The invention provides a novel free piston expander-linear generator integrated unit as a thermoelectric conversion device, and designs a novel vehicle waste heat recovery system based on a compound power supply system, wherein the system converts engine exhaust energy into high-grade electric energy and is used for driving a motor through the compound power supply system. The system can effectively improve the fuel economy of the engine, reduce the fuel consumption and reduce CO2And pollutants are discharged, the service life of the storage battery is prolonged, and the requirements of a vehicle-mounted power supply on high energy and high power are met.
Description
Technical Field
The invention relates to a waste heat recovery system for a free piston expander-linear generator vehicle based on a composite power supply, and belongs to the field of energy conservation and emission reduction.
Background
Energy is the power of social and economic development, and energy safety is the basis for guaranteeing national safety and national economy sustainable development. The increase of the automobile output and the keeping quantity will cause a great deal of energy consumption and severe environmental protection pressure, and CO discharged by the internal combustion engine of the automobile2Approximately accounts for global CO21/4 for total emissions. From the energy balance of a vehicular internal combustion engine, only 30% -45% (diesel engine) or 20% -30% (gasoline engine) of the total heat of fuel combustion is used for power output, and the rest of the energy is mainly discharged to the atmosphere through a cooling medium and exhaust gas. Therefore, the waste heat energy of the internal combustion engine for the vehicle can be efficiently recycled, so that the total energy efficiency of the internal combustion engine for the vehicle can be effectively improved, the fuel consumption can be reduced, and the CO can be reduced2And pollutant emissions. The organic Rankine cycle system has the advantages of high efficiency, simple structure, environmental friendliness and the like, and becomes one of effective ways for reducing the oil consumption of the internal combustion engine for the vehicle and reducing the pollutant emission of the internal combustion engine.
At present, there are patents which propose to recover waste heat energy of an internal combustion engine by using an organic rankine cycle system, and the waste heat energy is converted into electric energy to be stored in a storage battery for supplying power to a whole vehicle and driving a motor, so as to form a hybrid power system for the vehicle. However, the hybrid electric vehicle and the hybrid electric vehicle using the organic rankine cycle system still have some problems, such as: when the engine is operated alone, fuel efficiency is low and fuel consumption is high, and about 1/3 of energy is discharged to the atmosphere through the exhaust. The storage battery has small specific power, short cycle life, poor temperature characteristic and short driving range, the storage battery is singly used as a power source, when the vehicle has instantaneous high-power requirements, the storage battery can be impacted and damaged, particularly for urban working conditions, the vehicle has frequent starting, acceleration and deceleration processes, the power output fluctuation of the storage battery is frequent and large, and the impact damage to the storage battery is more serious.
Disclosure of Invention
The invention aims to solve the problems, and provides a novel integrated unit of a free piston expander and a linear generator as a thermoelectric conversion device in an organic Rankine cycle system, which can effectively improve the fuel economy of an engine, prolong the service life of a storage battery and meet the requirements of a vehicle-mounted power supply on high energy and high power.
The device horizontally places two free piston expanders and couples the two free piston expanders with a rotor of a linear generator through a connecting rod, drives the free piston expanders through high-temperature and high-pressure organic working media, converts exhaust waste heat energy of an internal combustion engine into mechanical energy, and further converts the mechanical energy into electric energy through the linear generator to be output. And based on the device, a composite power supply system based on the storage battery and the super capacitor is designed, and through the cooperative work of the super capacitor and the storage battery, the super capacitor can perform the functions of peak clipping and valley filling on the output power of the storage battery, so that the storage battery is prevented from being impacted and damaged by high-current charging and discharging, the service life of the storage battery is prolonged, and the use cost of the electric automobile is reduced. When the waste heat recovery system is in a better operation state, the electric energy generated by the free piston expander-linear generator can be stored in the storage battery and the super capacitor. The use of the composite power supply system meets the technical requirements of a vehicle-mounted power supply on high energy, high power and small volume to a great extent.
In order to achieve the above object, the present invention adopts the following technical solutions:
a waste heat recovery system for a free piston expander-linear generator vehicle based on a composite power supply mainly comprises an organic Rankine cycle system, a composite power supply system and a control system. The method specifically comprises the following steps: the automobile-used air conditioner comprises an internal combustion engine (1), an air compressor (2), a turbine (3), an evaporator (4), a free piston expander-linear generator (5), a condenser (6), a liquid storage tank (7), a working medium pump (8), an alternating current/direct current converter (9), a bidirectional DC/DC converter (10), a super capacitor (11), a storage battery (12), a first indicator (13), a second indicator (14), a power distributor (15), a DC/DC converter (16), a driving motor (17), a control unit (18), a first inlet valve (19), a second inlet valve (20), a first exhaust valve (21), a second exhaust valve (22), a first pressure sensor (23), a first temperature sensor (24), a first electric valve (25), a second electric valve (26), a second temperature sensor (27), a second pressure sensor (28), a third pressure sensor (29), The device comprises a temperature sensor III (30), a temperature sensor IV (31), a pressure sensor IV (32), a pressure sensor V (33), a free piston expander I (34), a free piston expander II (35), a free piston I (36), a free piston II (37), a piston ring I (38), a piston ring II (39), a linear generator (40), a linear generator rotor (41), an anti-collision spring I (42), an anti-collision spring II (43), an anti-collision spring III (44), an anti-collision spring IV (45), a displacement sensor (46) and various connecting pipelines and circuits.
The organic Rankine cycle system mainly comprises: the automobile-used air compressor comprises an internal combustion engine (1) for an automobile, an air compressor (2), a turbine (3), an evaporator (4), a free piston expander-linear generator (5), a condenser (6), a liquid storage tank (7) and a working medium pump (8). The main structure of the free piston expander-linear generator (5) integrated unit is that an inlet valve I (19), an exhaust valve I (21), a temperature sensor III (30) and a pressure sensor IV (32) are arranged on a cylinder of a free piston expander I (34), wherein a pressure sensor II (28) is arranged on the exhaust valve I (21); a first piston ring (38) is arranged on a first free piston (36) in the cylinder. Similarly, a second inlet valve (20), a second exhaust valve (22), a fourth temperature sensor (31) and a fifth pressure sensor (33) are arranged on a cylinder of the second free piston expander (35), wherein a third pressure sensor (29) is arranged on the second exhaust valve (22); and a second piston ring (39) is arranged on the second free piston (37) in the cylinder. The free piston expander I (34) and the free piston expander II (35) are horizontally arranged oppositely, and the free piston I (36), the free piston II (37) and the linear generator rotor (41) are coupled together through a connecting rod to form a piston rotor assembly; the displacement sensor (46) is arranged in the linear generator rotor (41); and a first anti-collision spring (42), a second anti-collision spring (43), a third anti-collision spring (44) and a fourth anti-collision spring (45) are arranged on two sides of the connecting rod of the piston rotor assembly.
The connection relation of each component of the organic Rankine cycle system is as follows: the air inlet passage is connected with the air compressor (2), the internal combustion engine (1) for the vehicle is connected with the air compressor (2) and the turbine (3), the turbine (3) is connected with the air exhaust passage, and the air compressor (2) and the turbine (3) are coaxial. An exhaust main pipe of the vehicle internal combustion engine (1) is divided into two branches, one branch is directly communicated with the atmosphere after passing through an electric valve I (25), the other branch is connected with an evaporator (4) through a pipeline after passing through an electric valve II (26), exhaust enters the evaporator (4) through the pipeline to exchange heat with an organic working medium, and energy is transmitted to the organic working medium and then is exhausted into the atmosphere; one end of the evaporator (4) is connected with the working medium pump (8) through a pipeline, and the other end of the evaporator is respectively connected with the first inlet valve (19) and the second inlet valve (20) through pipelines; the first exhaust valve (21) and the second exhaust valve (22) are connected with the condenser (6) through pipelines; one end of the liquid storage tank (7) is connected with the working medium pump (8), the other end of the liquid storage tank is connected with the condenser (6) through a pipeline, and all the connections are connected through pipelines to form a complete organic Rankine cycle loop.
The hybrid power supply mainly includes: the direct current power supply system comprises a linear generator (40), an alternating current/direct current converter (9), a bidirectional DC/DC converter (10), a super capacitor (11), a storage battery (12), a power distributor (15), a DC/DC converter (16) and a driving motor (17), wherein electric energy generated by the linear generator (40) is converted into direct current through the alternating current/direct current converter (9) and then enters the bidirectional DC/DC converter (10), the bidirectional DC/DC converter (10) is respectively connected with the storage battery (12) and the super capacitor (11), and current flowing out of the super capacitor (11) and the storage battery (12) firstly passes through the power distributor (15) and then is supplied to the driving motor (17) after being regulated through the DC/DC converter (16).
The control system mainly comprises: the device comprises a first indicator (13), a second indicator (14), a control unit (18), a first intake valve (19), a second intake valve (20), a first exhaust valve (21), a second exhaust valve (22), a first pressure sensor (23), a first temperature sensor (24), a first electric valve (25), a second electric valve (26), a second temperature sensor (27), a second pressure sensor (28), a third pressure sensor (29), a third temperature sensor (30), a fourth temperature sensor (31), a fourth pressure sensor (32), a fifth pressure sensor (33) and a displacement sensor (46). The first pressure sensor (23) and the first temperature sensor (24) are arranged on an exhaust manifold between the turbine (3) and the first electric valve (25); and a second temperature sensor (27) is arranged on the exhaust pipeline behind the evaporator (4).
The waste heat recovery system for the free piston expander-linear generator vehicle based on the composite power supply is symmetrically designed in such a way that two springs with different elastic stiffness are installed at one end of a rotor assembly of a linear generator (40), and two springs with different elastic stiffness are also installed at the other end of the rotor assembly; the ratio of the elastic stiffness of two springs with different elastic stiffness at the two ends is 1: 2; the elastic stiffness coefficients of the first anti-collision spring (42) and the second anti-collision spring (43) are the same, the elastic stiffness of the third anti-collision spring (44) and the fourth anti-collision spring (45) is the same, the free piston I (36) and the free piston II (37) are prevented from colliding with the cylinder, and energy is stored in the first anti-collision spring (42), the second anti-collision spring (43), the third anti-collision spring (44) and the fourth anti-collision spring (45) and used in the next piston stroke.
The charge states of the super capacitor (11) and the storage battery (12) are fed back according to the indicator I (13) and the indicator II (14), and the control unit (18) controls the charging and discharging of the super capacitor (11) and the storage battery (12) to prevent the super capacitor (11) and the storage battery (12) from generating an over-charging/discharging phenomenon; according to the real-time feedback of the indicator I (13) and the indicator II (14), by utilizing the characteristic that the super capacitor (11) is charged/discharged quickly, when the charge amount of the super capacitor (11) reaches 75%, the super capacitor (11) charges the storage battery (12) through the bidirectional DC/DC converter; the power of the composite power supply is distributed through a power distributor (15) according to the power requirements of a driving motor (17) under different running working conditions of the vehicle; when the required power of the vehicle is not more than the output power of the storage battery (12), the storage battery (12) drives the vehicle alone; when the charge quantity of the super capacitor (11) is lower than 25%, the charge quantity of the storage battery (12) is sufficient, and the required power of the vehicle is not larger than the output power of the storage battery (12), in order to meet the requirement of high power of the vehicle, the storage battery (12) not only drives the vehicle, but also charges the super capacitor (11), and when the charge quantity of the super capacitor (11) reaches 50%, the charging is stopped; when the vehicle goes up a slope or on a muddy road and the power demand is larger than the output power of the storage battery (12), the super capacitor (11) and the storage battery (12) drive the vehicle together.
Compared with the prior art, the invention has the following advantages:
1. in order to ensure the stable and efficient operation of the free piston expander, the operation mode of the linear generator is switched, which mainly comprises (a generator mode and a motor mode). In order to improve the efficiency and output power of the free piston expander, the linear generator is enabled to operate in a motor mode by actively controlling the linear generator, and the phenomena of an over-expansion state and an under-expansion state of the free piston expander are prevented. When the linear generator is in a power generation mode, the linear generator is ensured to operate in a high-efficiency operation area through active control over the linear generator.
2. When the internal combustion engine for the vehicle runs in the full working condition range, the running state of the piston of the free piston linear generator also needs to be changed along with the change of the running state of the piston, so that the best effect of waste heat energy recycling can be achieved. The method has the advantages that an expected piston motion position and the output performance of the linear generator are tracked as optimization targets, a double-closed-loop control strategy taking piston displacement and in-cylinder pressure as feedback is applied, so that the piston can stably run at the expected position, motion fluctuation constraint during transient variation of control variables in the full working condition range of the vehicle engine is met, and the working state of the free piston expander can be adjusted in real time according to the feedback of the in-cylinder pressure (an over-expansion state and an under-expansion state are prevented).
3. The invention aims at the requirement of a hybrid electric vehicle on a high-energy-density electric energy storage system, and establishes a composite power supply system for composite use of a super capacitor and a storage battery. The application of the composite power supply system meets the technical requirements of a vehicle-mounted power supply on high energy, high power and small volume to a great extent. And distributing the power of the hybrid power supply through the power distributor in combination with different running conditions of the vehicle. When the required power of the vehicle is not more than the output power of the storage battery, the storage battery drives the vehicle independently; when the energy storage of the super capacitor is insufficient, the charge quantity of the storage battery is sufficient, and the required power of the vehicle is not more than the output power of the storage battery, the storage battery not only drives the vehicle, but also charges the super capacitor, and when the charge quantity of the super capacitor reaches a certain value, the charging is stopped; when the vehicle goes up a slope or on a muddy road, the driving force needs to be increased, and the power demand is greater than the output power of the storage battery, the super capacitor and the storage battery jointly drive the vehicle.
4. The expansion ratio of the free piston can be adjusted due to the lack of a crank connecting rod mechanism, so that the free piston is suitable for different operation conditions; the number of moving accessories is small, the friction loss is small, and the like; but at the same time poses an inevitable problem of control of the movement of the piston (or mover assembly). In order to avoid the collision of the free piston with the cylinder, two springs with different elastic rigidities are arranged at two ends of a rotor assembly of the linear generator, so that the collision and oscillation phenomena of the free piston and the cylinder can be prevented, energy can be stored in the springs and used in the next piston stroke, the waste of energy is avoided, the energy conversion efficiency of a system is improved, and the stable, efficient and high-energy motion of the free piston expander is ensured.
Drawings
FIG. 1 is a schematic diagram of the principle of a waste heat recovery system for a free piston expander-linear generator vehicle based on a hybrid power supply
FIG. 2 is a schematic view of a free piston expander-linear generator integrated unit
In the figure: 1. an internal combustion engine for a vehicle; 2. a compressor; 3. a turbine; 4. an evaporator; 5. free piston expander-linear generator; 6. a condenser; 7. a liquid storage tank; 8. a working medium pump; 9. an AC/DC converter; 10. a bidirectional DC/DC converter; 11. a super capacitor; 12. a storage battery; 13. a first indicator; 14. a second indicator; 15. a power divider; 16. a DC/DC converter; 17. a drive motor; 18. a control unit; 19. a first inlet valve; 20. an intake valve II; 21. a first exhaust valve; 22. a second exhaust valve; 23. a first pressure sensor; 24. a first temperature sensor; 25. a first electric valve; 26. a second electric valve; 27. a second temperature sensor; 28. a second pressure sensor; 29. a third pressure sensor; 30. a third temperature sensor; 31. a fourth temperature sensor; 32. a fourth pressure sensor; 33. a fifth pressure sensor; 34. a free piston expander I; 35. a free piston expander II; 36. a free piston I; 37. a free piston II; 38. a first piston ring; 39. a second piston ring; 40. a linear generator; 41. a linear generator mover; 42. a first anti-collision spring; 43. a second anti-collision spring; 44. a third anti-collision spring; 45. a fourth anti-collision spring; 46. and a displacement sensor.
Detailed Description
The present invention will be further illustrated with reference to the following examples, but the present invention is not limited to the following examples.
Example 1: the present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1 and 2, the waste heat recovery system for the free piston expander-linear generator vehicle based on the hybrid power supply mainly comprises an organic rankine cycle system, a hybrid power supply system and a control system. The method specifically comprises the following steps: 1. an internal combustion engine for a vehicle; 2. a compressor; 3. a turbine; 4. an evaporator; 5. free piston expander-linear generator; 6. a condenser; 7. a liquid storage tank; 8. a working medium pump; 9. an AC/DC converter; 10. a bidirectional DC/DC converter; 11. a super capacitor; 12. a storage battery; 13. a first indicator; 14. a second indicator; 15. a power divider; 16. a DC/DC converter; 17. a drive motor; 18. a control unit; 19. a first inlet valve; 20. an intake valve II; 21. a first exhaust valve; 22. a second exhaust valve; 23. a first pressure sensor; 24. a first temperature sensor; 25. a first electric valve; 26. a second electric valve; 27. a second temperature sensor; 28. a second pressure sensor; 29. a third pressure sensor; 30. a third temperature sensor; 31. a fourth temperature sensor; 32. a fourth pressure sensor; 33. a fifth pressure sensor; 34. a free piston expander I; 35. a free piston expander II; 36. a free piston I; 37. a free piston II; 38. a first piston ring; 39. a second piston ring; 40. a linear generator; 41. a linear generator mover; 42. a first anti-collision spring; 43. a second anti-collision spring; 44. a third anti-collision spring; 45. a fourth anti-collision spring; 46. and a displacement sensor.
The organic Rankine cycle system mainly comprises: the automobile-used air compressor comprises an internal combustion engine (1) for an automobile, an air compressor (2), a turbine (3), an evaporator (4), a free piston expander-linear generator (5), a condenser (6), a liquid storage tank (7) and a working medium pump (8). The main structure of the free piston expander-linear generator (5) integrated unit is as follows, an inlet valve I (19), an exhaust valve I (21), a pressure sensor II (28), a temperature sensor III (30) and a pressure sensor IV (32) are arranged on a cylinder of a free piston expander I (34); a first piston ring (38) is arranged on a first free piston (36) in the cylinder. Similarly, an air inlet valve II (20), an air outlet valve II (22), a pressure sensor III (29), a temperature sensor IV (31) and a pressure sensor V (33) are arranged on an air cylinder of the free piston expander II (35); and a second piston ring (39) is arranged on the second free piston (37) in the cylinder. The free piston expander I (34) and the free piston expander II (35) are horizontally arranged oppositely, and the free piston I (36), the free piston II (37) and the linear generator rotor (41) are coupled together through a connecting rod to form a piston rotor assembly; the displacement sensor (46) is arranged in the linear generator rotor (41); an anti-collision spring I (42), an anti-collision spring II (43), an anti-collision spring III (44) and an anti-collision spring IV (45) are arranged on two sides of a connecting rod of the piston rotor assembly, so that a free piston can be prevented from colliding with a cylinder, and energy waste caused by collision can be avoided; in order to prevent the free piston from oscillating when approaching the cylinder, two springs with different elastic stiffness are arranged on two sides of a connecting rod of the piston rotor assembly, so that the stable, efficient and high-energy operation of the free piston expander is ensured.
The hybrid power supply system mainly includes: the device comprises a linear generator (40), an alternating current/direct current converter (9), a bidirectional DC/DC converter (10), a super capacitor (11), a storage battery (12), a power divider (15) and a DC/DC converter (16).
The control system mainly comprises: the device comprises a first indicator (13), a second indicator (14), a control unit (18), a first pressure sensor (23), a first temperature sensor (24), a first electric valve (25), a second electric valve (26), a second temperature sensor (27), a second pressure sensor (28), a third pressure sensor (29), a third temperature sensor (30), a fourth temperature sensor (31), a fourth pressure sensor (32), a fifth pressure sensor (33) and a displacement sensor (46). The first pressure sensor (23) and the first temperature sensor (24) are arranged on an exhaust manifold between the first electric valve (25) and the turbine (3); and a second temperature sensor (27) is arranged on the exhaust pipeline behind the evaporator (4). The first indicator (13), the second indicator (14), the temperature sensors (24, 27, 30, 31), the pressure sensors (23, 28, 29, 32, 33) and the displacement sensor (46) transmit collected signals to the control unit (18); the opening and closing of the first intake valve (19), the second intake valve (20), the first exhaust valve (21), the second exhaust valve (22), the first electric valve (25) and the second electric valve (26) are controlled by a control unit (18).
The connection relation of each component of the organic Rankine cycle system is as follows: the air inlet passage is connected with the air compressor (2), the internal combustion engine (1) for the vehicle is connected with the turbine (3) of the air compressor (2), the turbine (3) is connected with the air exhaust passage, and the air compressor (2) and the turbine (3) are coaxial. An exhaust main pipe of the vehicle internal combustion engine (1) is divided into two branches, one branch is directly communicated with the atmosphere after passing through an electric valve I (25), the other branch is connected with an evaporator (4) through a pipeline after passing through an electric valve II (26), exhaust enters the evaporator (4) through the pipeline to exchange heat with an organic working medium, and energy is transmitted to the organic working medium and then is exhausted into the atmosphere; one end of the evaporator (4) is connected with the working medium pump (8) through a pipeline, and the other end of the evaporator is respectively connected with the first inlet valve (19) and the second inlet valve (20) through pipelines; the first exhaust valve (21) and the second exhaust valve (22) are connected with the condenser (6) through pipelines; one end of the liquid storage tank (7) is connected with the working medium pump (8), the other end of the liquid storage tank is connected with the condenser (6) through a pipeline, and all the connections are connected through pipelines to form a complete organic Rankine cycle loop.
The connection relation of each part of the composite power supply system is as follows: electric energy generated by the linear generator (40) is converted into direct current through the alternating current/direct current converter (9) and then enters the bidirectional DC/DC converter (10), the bidirectional DC/DC converter (10) is respectively connected with the storage battery (12) and the super capacitor (11), and current flowing out of the storage battery (12) and the super capacitor (11) firstly passes through the power distributor (15), then is regulated through the DC/DC converter (16), then is supplied to the driving motor (17), and then is connected with the control unit (18) through a circuit.
The charge and discharge frequency of the super capacitor can reach 50000 times. The elastic stiffness coefficients of the first anti-collision spring (42) and the second anti-collision spring (43) are 80N/mm, the length of the spring is 8mm, the elastic stiffness of the third anti-collision spring (44) and the fourth anti-collision spring (45) is 160N/mm, and the natural length of the spring is 5 mm.
The working principle of the waste heat recovery system for the free piston expander-linear generator vehicle based on the DC/DC converter is described in detail in the following with the accompanying drawings:
different preset temperatures T are set as control signals, and the opening and closing of the electric valves (25, 26) are controlled by a control unit (18).
When the internal combustion engine (1) for the vehicle works, when the temperature sensor I (24) detects that the exhaust temperature is lower than T, the control unit (18) sends a command, the electric valve II (26) is closed, the electric valve I (25) is connected, and the exhaust gas of the internal combustion engine is directly exhausted into the atmosphere through the exhaust pipeline where the electric valve I (25) is located. When the temperature sensor I (24) detects that the exhaust temperature is higher than T, a control unit (18) sends an instruction, the electric valve I (25) is closed, the electric valve II (26) is connected, the tail gas of the internal combustion engine enters the evaporator (4) through a pipeline where the electric valve II (26) is located to exchange heat with the organic working medium pressurized by the working medium pump (5), the energy carried by the high-temperature tail gas is transferred to the liquid organic working medium to be changed into the high-temperature high-pressure gaseous organic working medium, then the high-temperature high-pressure gaseous organic working medium enters the free piston expanders (34,35), the free piston expanders (34,35) alternately expand to do work to push the piston rotor assembly to do reciprocating motion, and the rotor (41) of the linear generator is driven to do motion of cutting magnetic induction lines in the reciprocating motion process of the piston rotor assembly, so that electric energy. The low-pressure dead steam after acting enters a condenser (6) through a pipeline, the low-pressure dead steam is cooled into a liquid organic working medium in the condenser (6) under the action of cooling water, the liquid organic working medium flows into a liquid storage tank (7) through the pipeline, and the liquid organic working medium is temporarily stored. Then the working medium pump (8) pressurizes the organic working medium and then sends the organic working medium to the evaporator (4) again to exchange heat with the high-temperature tail gas, and thus, a working cycle is completed.
Electric energy generated by the linear generator (40) is converted into direct current after passing through the alternating current/direct current converter (9), then enters the bidirectional DC/DC converter (10) to be converted into charging voltage required by the super capacitor (11) and the storage battery (12), and then the super capacitor (11) and the storage battery (12) are charged. When the linear generator is in a power generation mode, the linear generator is ensured to operate in a high-efficiency operation area through active control of the motor. The working state of the free piston expander (34,35) is judged according to the second pressure sensor (28) and the third pressure sensor (29), and the over-expansion state and the under-expansion state are prevented from occurring. If the expanders (34,35) are in an underexpansion state, the energy efficiency utilization rate of the expanders (34,35) is low; if the expander (34,35) is in an over-expanded state, it will result in a lower output of the expander (34, 35). If the exhaust pressure is greater than P (P is greater than the atmospheric pressure), the free piston expanders (34,35) are in an under-expansion state, and the free piston expanders (34,35) are allowed to continue to expand by actively controlling the linear generator (40); if the exhaust pressure is less than the atmospheric pressure, the free piston expander (34,35) is in an over-expansion state, and the free piston expander (34,35) enters the next cycle by actively controlling the linear generator (40) to prevent the movement of the free piston (36, 37).
The charge states of the super capacitor (11) and the storage battery (12) are fed back according to the indicator I (13) and the indicator II (14), and the control unit (18) controls the charging and discharging of the super capacitor (11) and the storage battery (12), so that the super capacitor (11) and the storage battery (12) are prevented from being overcharged/overdischarged. In order to better improve the efficiency of the hybrid power system and meet the requirement of vehicle power, the super capacitor (11) can charge the storage battery (12) through the bidirectional DC/DC converter when the charge amount of the super capacitor (11) reaches 75% by utilizing the characteristic of quick charge/discharge of the super capacitor (11) according to real-time feedback of the indicator I (13) and the indicator II (14). And the power of the composite power supply is distributed through a power distributor (15) according to the power requirements of a driving motor (17) under different running conditions of the vehicle. When the required power of the vehicle is not more than the output power of the storage battery (12), the storage battery (12) drives the vehicle alone; when the charge quantity of the super capacitor (11) is lower than 25%, the charge quantity of the storage battery (12) is sufficient, and the required power of the vehicle is not larger than the output power of the storage battery (12), in order to meet the requirement of high power of the vehicle, the storage battery (12) not only drives the vehicle, but also charges the super capacitor (11), and when the charge quantity of the super capacitor (11) reaches 50%, the charging is stopped; when the vehicle goes up a slope or on a muddy road and the power demand is larger than the output power of the storage battery (12), the super capacitor (11) and the storage battery (12) drive the vehicle together.
Claims (4)
1. A waste heat recovery system for a free piston expander-linear generator vehicle based on a composite power supply comprises an organic Rankine cycle system, a composite power supply system and a control system; the method is characterized by specifically comprising the following steps: the automobile-used air conditioner comprises an internal combustion engine (1), an air compressor (2), a turbine (3), an evaporator (4), a free piston expander-linear generator (5), a condenser (6), a liquid storage tank (7), a working medium pump (8), an alternating current/direct current converter (9), a bidirectional DC/DC converter (10), a super capacitor (11), a storage battery (12), a first indicator (13), a second indicator (14), a power distributor (15), a DC/DC converter (16), a driving motor (17), a control unit (18), a first inlet valve (19), a second inlet valve (20), a first exhaust valve (21), a second exhaust valve (22), a first pressure sensor (23), a first temperature sensor (24), a first electric valve (25), a second electric valve (26), a second temperature sensor (27), a second pressure sensor (28), a third pressure sensor (29), The system comprises a temperature sensor III (30), a temperature sensor IV (31), a pressure sensor IV (32), a pressure sensor V (33), a free piston expander I (34), a free piston expander II (35), a free piston I (36), a free piston II (37), a piston ring I (38), a piston ring II (39), a linear generator (40), a linear generator rotor (41), an anti-collision spring I (42), an anti-collision spring II (43), an anti-collision spring III (44), an anti-collision spring IV (45), a displacement sensor (46) and various connecting pipelines and circuits;
the organic Rankine cycle system includes: the system comprises an internal combustion engine (1) for a vehicle, a gas compressor (2), a turbine (3), an evaporator (4), a free piston expander-linear generator (5), a condenser (6), a liquid storage tank (7) and a working medium pump (8); the free piston expander-linear generator (5) has the following structure: an inlet valve I (19), an exhaust valve I (21), a temperature sensor III (30) and a pressure sensor IV (32) are arranged on a cylinder of the free piston expander I (34), wherein a pressure sensor II (28) is arranged on the exhaust valve I (21); a first piston ring (38) is arranged in the free piston I (36) in the cylinder; similarly, a second inlet valve (20), a second exhaust valve (22), a fourth temperature sensor (31) and a fifth pressure sensor (33) are arranged on a cylinder of the second free piston expander (35), wherein a third pressure sensor (29) is arranged on the second exhaust valve (22); a second piston ring (39) is arranged on a second free piston (37) in the cylinder; the free piston expander I (34) and the free piston expander II (35) are horizontally arranged oppositely, and the free piston I (36), the free piston II (37) and the linear generator rotor (41) are coupled together through a connecting rod to form a piston rotor assembly; the displacement sensor (46) is arranged in the linear generator rotor (41); two sides of a connecting rod of the piston rotor assembly are provided with a first anti-collision spring (42), a second anti-collision spring (43), a third anti-collision spring (44) and a fourth anti-collision spring (45);
the connection relation of each component of the organic Rankine cycle system is as follows: the air inlet passage is connected with the air compressor (2), the vehicle internal combustion engine (1) is connected with the air compressor (2) and the turbine (3), the turbine (3) is connected with the air exhaust passage, and the air compressor (2) and the turbine (3) are coaxial; an exhaust main pipe of the vehicle internal combustion engine (1) is divided into two branches, one branch is directly communicated with the atmosphere after passing through an electric valve I (25), the other branch is connected with an evaporator (4) through a pipeline after passing through an electric valve II (26), exhaust enters the evaporator (4) through the pipeline to exchange heat with an organic working medium, and energy is transmitted to the organic working medium and then is exhausted into the atmosphere; one end of the evaporator (4) is connected with the working medium pump (8) through a pipeline, and the other end of the evaporator is respectively connected with the first inlet valve (19) and the second inlet valve (20) through pipelines; the first exhaust valve (21) and the second exhaust valve (22) are connected with the condenser (6) through pipelines; one end of the liquid storage tank (7) is connected with the working medium pump (8), the other end of the liquid storage tank is connected with the condenser (6) through a pipeline, and all the connections are connected through pipelines to form a complete organic Rankine cycle loop;
the hybrid power supply includes: the system comprises a linear generator (40), an alternating/direct current converter (9), a bidirectional DC/DC converter (10), a super capacitor (11), a storage battery (12), a power distributor (13), a DC/DC converter (16) and a driving motor (17), wherein electric energy generated by the linear generator (40) is converted into direct current through the alternating/direct current converter (9) and then enters the bidirectional DC/DC converter (10), the bidirectional DC/DC converter (10) is respectively connected with the storage battery (12) and the super capacitor (11), and currents flowing out of the storage battery (12) and the super capacitor (11) firstly pass through the power distributor (15) and then are regulated through the DC/DC converter (16) and then are supplied to the driving motor (17);
the control system includes: the device comprises a first indicator (13), a second indicator (14), a control unit (18), a first intake valve (19), a second intake valve (20), a first exhaust valve (21), a second exhaust valve (22), a first pressure sensor (23), a first temperature sensor (24), a first electric valve (25), a second electric valve (26), a second temperature sensor (27), a second pressure sensor (28), a third pressure sensor (29), a third temperature sensor (30), a fourth temperature sensor (31), a fourth pressure sensor (32), a fifth pressure sensor (33) and a displacement sensor (46); the first pressure sensor (23) and the first temperature sensor (24) are arranged on an exhaust manifold between the turbine (3) and the first electric valve (25); and a second temperature sensor (27) is arranged on the exhaust pipeline behind the evaporator (4).
2. The hybrid power supply-based free piston expander-linear generator vehicle waste heat recovery system as claimed in claim 1, wherein the electric energy generated by the linear generator (40) is converted into direct current after passing through the ac/DC converter (9), and then enters the bidirectional DC/DC converter (10) to be converted into the charging voltage required by the super capacitor (11) and the storage battery (12), and then the super capacitor (11) and the storage battery (12) are charged; the linear generator (40) is switched to work modes, including a generator mode and a motor mode; the linear generator (40) is enabled to run in a motor mode by actively controlling the linear generator (40), and the phenomena of an over-expansion state and an under-expansion state of the free piston expander I (34) and the free piston expander II (35) are prevented; when the linear generator (40) is in a generating mode, the generating efficiency of the linear generator (40) is ensured to reach more than 97 percent through the active control of the linear generator (40).
3. The waste heat recovery system for a hybrid power supply-based free piston expander-linear generator vehicle as claimed in claim 1, wherein two springs with different elastic stiffness are mounted at one end of a mover assembly of the linear generator (40), and two springs with different elastic stiffness are mounted at the other end, and the system is designed symmetrically; the ratio of the elastic stiffness of two springs with different elastic stiffness at the two ends is 1: 2; the elastic stiffness coefficients of the first anti-collision spring (42) and the second anti-collision spring (43) are the same, the elastic stiffness of the third anti-collision spring (44) and the fourth anti-collision spring (45) is the same, the free piston I (36) and the free piston II (37) are prevented from colliding with the cylinder, and energy is stored in the first anti-collision spring (42), the second anti-collision spring (43), the third anti-collision spring (44) and the fourth anti-collision spring (45) and used in the next piston stroke.
4. The hybrid power supply-based waste heat recovery system for a free piston expander-linear generator vehicle as claimed in claim 1, wherein: the charge states of the super capacitor (11) and the storage battery (12) are fed back according to the indicator I (13) and the indicator II (14), and the control unit (18) controls the charging and discharging of the super capacitor (11) and the storage battery (12) to prevent the super capacitor (11) and the storage battery (12) from generating an over-charging/discharging phenomenon; according to the real-time feedback of the indicator I (13) and the indicator II (14), by utilizing the characteristic that the super capacitor (11) is charged/discharged quickly, when the charge amount of the super capacitor (11) reaches 75%, the super capacitor (11) charges the storage battery (12) through the bidirectional DC/DC converter; the power of the composite power supply is distributed through a power distributor (15) according to the power requirements of a driving motor (17) under different running working conditions of the vehicle; when the required power of the vehicle is not more than the output power of the storage battery (12), the storage battery (12) drives the vehicle alone; when the charge quantity of the super capacitor (11) is lower than 25%, the charge quantity of the storage battery (12) is sufficient, and the required power of the vehicle is not larger than the output power of the storage battery (12), in order to meet the requirement of high power of the vehicle, the storage battery (12) not only drives the vehicle, but also charges the super capacitor (11), and when the charge quantity of the super capacitor (11) reaches 50%, the charging is stopped; when the vehicle goes up a slope or on a muddy road and the power demand is larger than the output power of the storage battery (12), the super capacitor (11) and the storage battery (12) drive the vehicle together.
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| CN110217113A (en) * | 2019-06-12 | 2019-09-10 | 北京工业大学 | Free piston expander-linear electric generator and composite power source stroke-increasing electric automobile |
| CN110509782A (en) * | 2019-09-06 | 2019-11-29 | 北京工业大学 | Stroke-increasing electric automobile based on air motor |
| DE102019133018A1 (en) * | 2019-12-04 | 2021-06-10 | Bayerische Motoren Werke Aktiengesellschaft | Device for temperature control of a component of an internal combustion engine and / or an exhaust system |
| CN111237021B (en) * | 2020-01-13 | 2022-06-28 | 北京工业大学 | Small-pressure-difference steam direct-driven high-supercharging-ratio working medium pump for organic Rankine cycle |
| CN111535892A (en) * | 2020-06-02 | 2020-08-14 | 西安热工研究院有限公司 | Low-temperature waste heat simple power generation system and method adopting linear generator |
| CN111706398B (en) * | 2020-07-31 | 2024-04-09 | 中南大学 | High expansion ratio horizontal opposed piston type expander and control method |
| CN113047949B (en) * | 2021-03-12 | 2021-09-21 | 哈尔滨工程大学 | Split-cylinder free piston generator based on PID closed-loop control |
| CN113266464B (en) * | 2021-06-21 | 2022-04-19 | 北京理工大学 | Free piston internal combustion linear generator operation system and operation control method |
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| CA2975515C (en) * | 2015-01-30 | 2021-09-14 | Claudio Filippone | Waste heat recovery and conversion |
| CN108386271B (en) * | 2018-03-08 | 2021-01-15 | 北京工业大学 | Vehicle gas-electricity hybrid power system for generating electricity by utilizing residual pressure of compressed natural gas |
| CN108374718B (en) * | 2018-03-14 | 2023-04-28 | 北京工业大学 | Integrated measurement and control system of internal combustion type free piston linear generator with controllable piston stroke |
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