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EP3594569A1 - Dispositif de récupération de chaleur - Google Patents

Dispositif de récupération de chaleur Download PDF

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Publication number
EP3594569A1
EP3594569A1 EP18382522.3A EP18382522A EP3594569A1 EP 3594569 A1 EP3594569 A1 EP 3594569A1 EP 18382522 A EP18382522 A EP 18382522A EP 3594569 A1 EP3594569 A1 EP 3594569A1
Authority
EP
European Patent Office
Prior art keywords
fluid
turbine
expander
liquid
pump
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP18382522.3A
Other languages
German (de)
English (en)
Inventor
Javier ARÍZTEGUI CORTIJO
Fermín OLIVA MIÑANA
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Repsol SA
Original Assignee
Repsol SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Repsol SA filed Critical Repsol SA
Priority to EP18382522.3A priority Critical patent/EP3594569A1/fr
Publication of EP3594569A1 publication Critical patent/EP3594569A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B3/00—Other methods of steam generation; Steam boilers not provided for in other groups of this subclass
    • F22B3/04—Other methods of steam generation; Steam boilers not provided for in other groups of this subclass by drop in pressure of high-pressure hot water within pressure-reducing chambers, e.g. in accumulators
    • 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

Definitions

  • the present invention relates to a heat recovery device particularly conceived for an internal combustion engine, and in particular for a vehicle including said internal combustion engine.
  • the heat recovery device is based on a Rankine cycle in which the high-pressure stage has been modified.
  • the fluid on which the thermal cycle is carried out, or working fluid is compressed in the liquid phase by the pump until it reaches the heat source causing the phase change.
  • the phase change usually takes place in a boiler or in an evaporator, in such a manner that the fluid changes phase significantly increasing its specific volume in its transition inside the boiler or evaporator.
  • the fluid in the vapor phase having a high enthalpy provided by the heat source, enters the turbine or expander, where a large part of the enthalpy is transformed into mechanical energy.
  • the invention is characterized by the use of a tank in the high-pressure region of the Rankine cycle for storing the fluid before entering the turbine or expander, maintaining said fluid in the liquid phase so as to drastically reduce its specific volume, and an expansion valve arranged between the tank and the inlet of the turbine or expander for causing the liquid-to-vapor phase change of the fluid right at the inlet, which prevents that the high specific volume in the vapor phase leads to large-sized devices.
  • One alternative used for harnessing the residual heat of the exhaust gases and of the cooling fluid is to include a Rankine cycle wherein said exhaust gases and cooling fluid are the heat source. Even though a Rankine cycle in an industrial plant can have enough space for the devices involved, in a vehicle, and in particular in the engine compartment, space is a scarce resource.
  • Evaporation devices or boilers in charge of providing energy to the Rankine cycle require a large volume since the phase change significantly increases the volume required for circulating the fluid in the liquid plus vapor phase or finally in the form of vapor.
  • the Rankine cycle When a Rankine cycle is used in a vehicle, the primary demand for energy occurs when a driving force of the vehicle is required, and is nil, with respect to this same force, when actuating with the brake of the vehicle. Under these circumstances, the Rankine cycle according to the state of the art does not have the capacity to almost instantaneously regulate the energy given off by the fluid in the turbine or expander and making use of the mechanical energy obtained, so as to provide that driving force at suitable times.
  • the present invention solves these problems by preventing the circulation of the fluid with high enthalpy in the vapor phase during the energy transfer from the hot source to the fluid, this objective being achieved by causing the phase change right before the fluid is introduced into the turbine or expander.
  • the specific volume of the fluid with high enthalpy is thereby drastically reduced, and the components through which the fluid passes in this step are therefore also reduced. This allows reducing the size of the devices, thereby preventing the installation of extremely bulky evaporators.
  • the invention also solves specific problems according to various embodiments that will be described in detail below in relation to the figures.
  • the present invention is a heat recovery device suitable for an internal combustion engine.
  • the device is based on a Rankine cycle and comprises at least:
  • the hot fluid is the cooling fluid.
  • the Rankine cycle is carried out on a fluid in a closed circuit.
  • the turbine or expander is the component which transforms the energy stored in the working fluid, which has high enthalpy, into mechanical energy, for example driving a shaft.
  • the inlet in the turbine or expander receives the fluid in the vapor phase with high enthalpy and at the outlet the same fluid continues in the vapor phase but with lower enthalpy and lower pressure.
  • the fluid at the outlet of the turbine or expander now with lower enthalpy, enters the condenser for causing the vapor-to-liquid phase change.
  • the condenser is a heat exchanger that cools the vapor by removing heat.
  • the fluid coolant which removes the heat from the thermal fluid in the vapor phase is the liquid coolant of the internal combustion engine. If the heat to be removed is high, the engine may include a second cooling circuit for example with an independent radiator.
  • the fluid coolant which removes the heat from the thermal fluid in the vapor phase is the ambient air around the engine.
  • the fluid Once the fluid has exited the condenser, it is in the liquid phase and has a lower specific volume.
  • the fluid is pumped by means of the pressure pump, again raising its pressure and maintaining the fluid in the liquid phase.
  • the fluid at high pressure again receives heat from the heat source, or main heat exchanger, to increase its enthalpy.
  • the preferred way to provide heat is by means of one or several heat exchangers that transfer the heat of the exhaust gases to the thermal fluid following the Rankine cycle.
  • the exhaust gases come from either the exhaust pipe circuit, from the exhaust gas recirculation circuit for recirculating said exhaust gas to the intake manifold, or from both.
  • the heat can be transferred from the hot cooling fluid of the engine to the thermal fluid following the Rankine cycle.
  • the invention modifies the elements normally arranged in the fluid communication existing between the pump and the turbine or expander.
  • the device comprises:
  • the device comprises a first tank (5) interposed in the fluid communication between the outlet (4.2) of the first pressure pump (4) and the inlet (1.1) of the turbine or expander (1) for storing the fluid at high pressure in the liquid phase heated by the main exchanger (7), and wherein the expansion valve (6) is located between the first tank (5) and the inlet (1.1) of the turbine or expander (1).
  • the liquid fluid exiting the pump enters a boiler or evaporator such that the phase change takes place inside this element.
  • the phase change takes place inside this element.
  • the element where the phase change takes place there is a first segment with the fluid in the liquid phase where its temperature gradually increases until reaching the boiling temperature, a second segment where a mixture of liquid plus vapor can be found, and finally a third segment where just vapor can be found.
  • the second and third stages require the element used for causing the phase change to be very bulky, since the vapor gradually increases the specific volume in a very significant manner.
  • Elements of this type are furthermore oversized, since the point between the first and the second segment and the point between the second and the third segment constantly change position depending on operating conditions, and the positions thereof cannot be readily established.
  • the element in charge of providing heat causing the phase change must therefore have a volume sufficient for storing all the vapor no matter where it is generated, in order not to become damaged.
  • the device according to the invention comprises an expansion valve causing in the fluid with high pressure and enthalpy the abrupt transitioning from the liquid phase to the vapor phase right before entering the turbine or expander.
  • the highest specific volume of the vapor phase can be found right at the inlet of the turbine or expander, so no intermediate device is required to have a large volume for storing vapor.
  • the tank is interposed in the fluid communication between the outlet of the first pressure pump and the inlet of the turbine or expander for storing the fluid at high pressure in the liquid phase and heated by the heat exchanger.
  • the heat exchanger raises the temperature by means of circulating the thermal fluid between the heat exchanger and the inside of the first tank.
  • the first tank has more than one compartment such that the passage from one compartment to another is carried out through the heat exchanger.
  • the first tank stores liquid at high pressure and high enthalpy, and the fluid also raises its temperature due to the transfer of heat either from the hot cooling fluid of the engine or else from the exhaust gases to the liquid fluid, or even from both.
  • the device combines the first tank with an expansion valve located between said first tank and the turbine or expander.
  • the present invention is a device for heat recovery that can be applied to recovering heat from any heat source with the suitable temperature so as to establish the thermodynamic cycle for the selected fluid.
  • all of the examples described in this section will refer to recovering heat from the residual heat coming from either a hot cooling fluid or else from the exhaust gases of an internal combustion engine, such as a stationary internal combustion engine, for example, used as an electricity generator; and more specifically for a vehicle with an internal combustion engine where space requirements are stricter.
  • Figure 1 shows a diagram where the components of a device according to several embodiments of the invention are identified.
  • a turbine or expander (1) is responsible for transforming part of the enthalpy (h) of the fluid in the vapor phase entering through an inlet (1.1) into mechanical energy, the fluid exiting also in the vapor phase through an outlet (1.2).
  • the component transforming the enthalpy (h) of the fluid into mechanical energy is a turbine (1)
  • the mechanical energy that is obtained is provided in the rotating shaft of the turbine.
  • said component can be a cylinder with axial displacement.
  • One or more axial cylinders can for example drive a crankshaft transforming the axial displacement into rotation of the shaft also.
  • This shaft can provide its energy either directly to the driving of the vehicle with a kinematic coupling which is aggregated to the drive from the engine, or else indirectly for example by coupling the output shaft to a current generator feeding, with or without the intermediation of electric batteries, one or more electric motors, giving rise to a hybrid propulsion system or covering the electrical energy needs of the vehicle.
  • the vapor exiting the outlet (1.2) of the turbine or expander (1) is introduced in a condenser (2) for causing the phase change, from the vapor phase to the liquid phase, reducing its specific volume.
  • the inlet (2.1) of the condenser (2) thereby receives vapor from the outlet of the turbine or expander (1) and through the outlet (2.2) of the condenser (2) itself it exits in the liquid state, ready for raising its pressure again.
  • the outlet (2.2) of the condenser (2) is fluidic communicated with a tank referred to as second tank (3) with a capacity for storing a variable volume of liquid.
  • This second tank (3) is an optional element that will be used for a specific example that will be described below.
  • the outlet of the second tank (3) for storing liquid is fluidic connected with an inlet (4.1) of a first pump (4) at the outlet (4.2) of which the same liquid is obtained at a higher pressure.
  • the liquid fluid exiting the outlet (4.2) of the first pump (4) passes through a heat exchanger which will be identified as third heat exchanger (10).
  • This third heat exchanger (10) is an optional component according to one embodiment in which the liquid fluid is pre-heated for example by means of the liquid coolant of the internal combustion engine or by means of the regenerator (12).
  • this hot source consists of the exhaust gases of the internal combustion engine from which heat is to be recovered. This heat of the exhaust gases may in turn have two sources: the exhaust gases circulating through the exhaust pipe out into the atmosphere, or the exhaust gases that are recirculated to the intake manifold of the engine.
  • a main heat exchanger (7) has its inlet and its outlet in fluid communication with the first tank (5), the liquid fluid being exchanged between the first tank (5) and said main heat exchanger (7), raising its temperature.
  • One way to circulate the liquid fluid is by means of a hot fluid recirculation pump or drive pump, not depicted in Figure 1 .
  • Another way to circulate the liquid fluid is by means of pressure differences between the compartments of the tank.
  • the first tank (5) comprises a movable wall that allows the expansion of its internal volume such that the volume of liquid fluid to be stored is variable.
  • this movable wall has a spring or elastic element that tends to recover its initial position such that it maintains the pressure in the variable inner volume.
  • this embodiment it is possible to almost instantaneously manage the injection of fluid into the turbine or expander (1) since the mass flow at the outlet of the first tank (5) which changes phase in the expansion valve (6) does not have to be equal to the mass flow imposed by the first pump (4).
  • the mechanical energy delivered by the turbine or expander (1) can be controlled in the event of drive demands of the vehicle or the energy needs of auxiliary devices.
  • this tank (5) comprises two compartments (5.1, 5.2), a low-temperature compartment (5.1) and another high-temperature compartment (5.2).
  • the liquid fluid either exiting the first pump (4) or else exiting the third heat exchanger (10) first enters the first low-temperature compartment (5.1) and from there it passes on to the second high-temperature compartment (5.2), passing through the main heat exchanger (7) which transfers heat from the exhaust gases to the thermal fluid. It is this second high-temperature compartment (5.2) that feeds the turbine or expander (1) with the intermediation of the expansion valve (6).
  • the first pump (4) is actuated through a regenerative brake of the vehicle.
  • the brake torque of the wheels of the vehicle is used as the drive torque of the first pump (4).
  • a regenerative brake is the one including the second tank (3) described above, since the first pump (4) has liquid to be pumped at any time, since the braking moments are not predictable. At the time of braking, the regenerative brake acts on the first pump (4) by raising the pressure of an amount of liquid fluid that is transferred from the second tank (3) to the first tank (5) regardless of the mass flow going through either the turbine or expander (1).
  • the device comprises a central processing unit (CPU) with an output for providing an actuation signal either in the expansion valve (6) or else in a flow control valve located before or after the expansion valve (6) for the opening or closing thereof, the processing unit (CPU) being configured for managing the expansion valve (6) or the flow control valve by injecting vapor into the turbine or expander (1) only when the vehicle requires driving power.
  • CPU central processing unit
  • the central processing unit is additionally configured for sending an actuation signal to close the expansion valve (6) when the first pump (4) is driven by the regenerative brake.
  • the cycle of the thermal fluid therefore adapts to the braking and drive demands of the vehicle, primarily when the mechanical energy obtained in the turbine or expander (1) is used in driving the vehicle.
  • the present embodiment allows controlling the expansion valve (6), located before the turbine or expander (1), by means of two options such that both the flow rate and the expansion are managed by the central processing unit (CPU):
  • control of the expansion valve (6) requires reading the pressure difference with pressure sensors between the inlet and the outlet of said expansion valve (6) so that the central processing unit (CPU) can establish an opening of the expansion valve (6) that determines sufficient flashing for assuring the phase change of the entire flow.
  • CPU central processing unit
  • One embodiment based on any of the examples described up until now includes a superheater (11) that raises the temperature of the vapor obtained in the expansion valve (6). It is thereby assured that the vapor does not transition to the liquid phase until after it exits the turbine or expander (1).
  • the thermal fluid is such that the liquid plus vapor/vapor equilibrium curve (L2) in the entropy (S)/enthalpy (h) graph comprises at least one segment for values of enthalpy (h) that are lower than the critical point enthalpy in which the slope is such that an increase in entropy (S) corresponds to an increase in enthalpy (h) has been found to be of particular interest.
  • FIG. 2 An example of an entropy (S)/enthalpy (h) graph showing this example is shown in Figure 2 .
  • the solid lines depict both the liquid/liquid plus vapor equilibrium curve (L1) and the liquid plus vapor/vapor equilibrium curve (L2).
  • the discontinuous lines identify the path of the thermal cycle of the fluid according to a preferred example.
  • the intersection of both continuous curves identifies the critical point (CR).
  • the first pump (4) raises the pressure and therefore the enthalpy (h) according to a process that would ideally be isentropic (D).
  • the liquid raises the enthalpy and the entropy (E) thereof by raising the temperature by means of the heat given off from the hot cooling fluid of the engine and from the exhaust gases, for example through the main heat exchanger (7).
  • the fluid is kept to the left of the liquid/liquid plus vapor equilibrium curve (L1), so it is stored in the first tank (5) taking up a reduced volume.
  • the liquid is expanded by means of the expansion valve (6) according to an isenthalpic process (A) causing all of the liquid to change phase to vapor phase.
  • the vapor is introduced in the turbine or expander (1) continuing with a process which would ideally be isentropic (B), until reaching the lower point of the straight vertical segment.
  • the isenthalpic process (A) takes place below the critical point (CR), although it may be possible for it to take place above it.
  • the fluid in the vapor phase is introduced in the condenser (2) going through two solid lines, given that it goes from vapor to liquid plus vapor and then all of the fluid is in the liquid phase, returning to the point from where the description of the path of the thermal cycle based on Figure 2 started.
  • the same drawing identifies, using a thicker segment located between two thick points, the at least one segment verifying the condition of having an inclination such that, for values of enthalpy (h) that are lower than the critical point enthalpy (CR), the slope is such that an increase in entropy (S) corresponds to an increase in enthalpy (h).
  • the segment which is subject to the imposition of having an inclination such that the slope is such that an increase in entropy (S) corresponds to an increase in enthalpy (h) is a segment having its upper end at the critical point (CR).
  • regenerator (12) which allows reducing the temperature of the gas after it passes through the turbine or expander (1) and reutilizing this heat to heat up the working fluid after it passes through the pump (4).
  • Figure 1 the two stages of the heat exchanger (12) are shown to be connected by means of a dashed line, indicating that both stages can be configured in one and the same physical device.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)
EP18382522.3A 2018-07-12 2018-07-12 Dispositif de récupération de chaleur Withdrawn EP3594569A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP18382522.3A EP3594569A1 (fr) 2018-07-12 2018-07-12 Dispositif de récupération de chaleur

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP18382522.3A EP3594569A1 (fr) 2018-07-12 2018-07-12 Dispositif de récupération de chaleur

Publications (1)

Publication Number Publication Date
EP3594569A1 true EP3594569A1 (fr) 2020-01-15

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EP18382522.3A Withdrawn EP3594569A1 (fr) 2018-07-12 2018-07-12 Dispositif de récupération de chaleur

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5241817A (en) * 1991-04-09 1993-09-07 George Jr Leslie C Screw engine with regenerative braking
US20110259010A1 (en) * 2010-04-22 2011-10-27 Ormat Technologies Inc. Organic motive fluid based waste heat recovery system
US20140060519A1 (en) * 2011-03-24 2014-03-06 David Bent Generation Of Steam For Use In An Industrial Process
WO2014065397A1 (fr) * 2012-10-26 2014-05-01 三菱重工業株式会社 Système de moteur à combustion interne, navire le comprenant, et procédé de fonctionnement de système de moteur à combustion interne
US20170081982A1 (en) * 2014-05-19 2017-03-23 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Method for recovering heat from internal combustion engines and for converting the recovered heat into mechanical energy

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5241817A (en) * 1991-04-09 1993-09-07 George Jr Leslie C Screw engine with regenerative braking
US20110259010A1 (en) * 2010-04-22 2011-10-27 Ormat Technologies Inc. Organic motive fluid based waste heat recovery system
US20140060519A1 (en) * 2011-03-24 2014-03-06 David Bent Generation Of Steam For Use In An Industrial Process
WO2014065397A1 (fr) * 2012-10-26 2014-05-01 三菱重工業株式会社 Système de moteur à combustion interne, navire le comprenant, et procédé de fonctionnement de système de moteur à combustion interne
US20170081982A1 (en) * 2014-05-19 2017-03-23 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Method for recovering heat from internal combustion engines and for converting the recovered heat into mechanical energy

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