FR3098286A1 - RANKINE THERMODYNAMIC CYCLE SYSTEM INTEGRATED WITH A MULTIPLE EJECTOR AIR CONDITIONING LOOP - Google Patents

Abstract

A system (30) for a vehicle comprising an air conditioning circuit (42) comprising a first evaporator (33) and a holder (36), a Rankine cycle system (43) comprising an expansion machine (39). , a pump (34) and a second evaporator (32), said thermodynamic system (30) further comprising a condenser (35) common to said air conditioning circuit (42) and to said Rankine cycle system (43), at least one first ejector (31a) and a second ejector (31b) connected to said second evaporator (32) by means of a distribution device (41), said condenser (35) being connected to said second evaporator (32), said heating machine expansion (39) being connected to said second evaporator (32) via said distribution device (41), said expansion machine (39) and said at least first ejector (31a) and second ejector (31b) being connected to said condenser (35) via a combination device (40). Figure 3

Description

RANKINE THERMODYNAMIC CYCLE SYSTEM INTEGRATED WITH A MULTIPLE EJECTOR AIR CONDITIONING LOOP

The invention relates to a so-called Rankine thermodynamic cycle system integrated into an air conditioning loop using several ejectors.

It is known from the state of the art that only a small part of the energy produced by a heat engine is actually transmitted to the vehicle; more than 20% corresponds to lost mechanical energy (about 20% engine losses, about 5% gearbox losses, and about 2% pumping losses), while more than 50% of the energy produced by the engine is lost in the form of exhaust heat and water.

This heat rejected by the heat engine can be recovered and partially reconverted into mechanical or electrical power through the use of a Rankine thermodynamic cycle system.

Such a system uses phase change fluids (water or organic fluid) to produce energy. The use of organic fluids makes it possible to better adapt to temperatures to valorize the heat rejected at low temperature. The selection of the working fluid is a factor affecting cycle efficiency. The difference between the organic Rankine cycle (or ORC for "Organic Rankine Cycle" in English) and the classic cycle, also called "Steam Rankine" in English, is the use of an organic working fluid instead of the water vapour, in this case the critical point is reached at a lower temperature and pressure compared with water. The heat source on a vehicle may be either the coolant or the exhaust gases.

As can be seen in Figure 1, a Rankine cycle system 1 comprises a liquid pump 2, an evaporator 3 (hot exchanger coupling the working fluid of the loop to hot air A_ch or to the liquid of cooling of the engine, a turbine 4 or another type of expansion machine, as well as a condenser 5 (cold exchanger coupling the working fluid of the loop to cold air).The ORC cycle is composed of a phase compression of the fluid leaving the condenser by the pump 2, of a heating phase of the fluid at constant pressure in the evaporator 3, of an expansion phase in the turbine 4, and of a condensation phase at constant pressure in the condenser 5.

Thus, the working fluid at the outlet of condenser 5 (Point P1) is compressed until it reaches a higher pressure at the outlet of pump 2 (Point P2). The fluid then passes through the evaporator 3 in which it is heated and vaporized thanks to a heat exchange between the heat source and the working fluid. At the outlet of the evaporator 3 (cf. point P3), the fluid has a higher enthalpy and then passes into the turbine 4 in which it undergoes work-producing expansion. The turbine 4 generally drives an electric generator which makes it possible to reinject the power in electrical form. The fluid at the outlet of turbine 4 (Point P4) is then condensed in condenser 5 to return to compress again.

Furthermore, there is also known in the prior art a thermodynamic air conditioning system 20 with an ejector, as can be seen in FIG. 2. Such a thermodynamic system 20 comprises an ejector 21. The ejector 21 has a nozzle convergent at its inlet then divergent, thus allowing the high-pressure working fluid coming from the boiler 22 to be relaxed. The ejector 21 draws in the low-pressure working fluid coming from the evaporator 23, thus allowing the working fluid to circulate. The thermodynamic system 20 further comprises a pump 24 for circulating the working fluid, a condenser 25 whose function is to reject the residual heat to the outside and an expander 26 whose function is to expand the working fluid leaving the condenser 25. The thermodynamic ejector system 20 operates in the manner described below. A first part of the working fluid leaving the condenser 25 is compressed by the pump 24, the high pressure working fluid leaving the pump 24 then enters a boiler 22 in which the working fluid is heated, vaporized and superheated by a hot fluid entering the boiler 22 through the inlet 27 and leaving the boiler 22 through the outlet 28. The working fluid in the form of superheated vapor at high pressure then expands in the ejector 21 to draw in working fluid under vapor coming from the evaporator 23. The second part of working fluid leaving the condenser 25 expands in the expander 26 to thus produce cold in the evaporator.

Nowadays vehicles, in particular automobiles, include an increasing number of electrical equipment requiring therefore an increasingly important production of electrical energy. A Rankine 1 thermodynamic cycle system solves this problem. Indeed, the turbine 4 generates mechanical energy and drives an electric generator. The electric generator thus produces part of the electrical energy necessary for the various electrical equipment of the vehicle. The major drawback of this method of electricity production is that it requires additional components which therefore add mass to the vehicle. In addition, it is necessary to provide a volume, in the vehicle, to accommodate these additional components. For some vehicles, it is very difficult, if not impossible, to integrate these components because the space available is very limited. In an attempt to solve these various drawbacks, the thermodynamic ejector air conditioning system 20 has been proposed as illustrated in FIG. Rankine 1 thermodynamic cycle nevertheless remains of little advantage in the environment of a vehicle, in particular an automobile. Indeed, the energy gains obtained do not make it possible to compensate for the additional energy expenditure, in particular in fuel, resulting from the additional on-board mass of such a Rankine 1 thermodynamic system.

The object of the invention is to overcome the drawbacks of the prior art by proposing a thermodynamic system for a vehicle, in particular an automobile, making it possible to produce electrical energy and to air-condition the passenger compartment of said vehicle, and having the advantage of use, at least in part, the components of said vehicle and thus allow a reduction of said vehicle.

To do this, the invention thus relates, in its broadest sense, to a thermodynamic system for a vehicle, in particular an automobile, equipped with a heat engine comprising:

- an air conditioning circuit comprising:

- a first evaporator capable of absorbing heat from the passenger compartment of said vehicle,

- a holder,

- a Rankine thermodynamic cycle system capable of recovering energy from said heat engine comprising:

- an expansion machine, such as a turbine,

- a pump capable of increasing the pressure of a working fluid, and

- a second evaporator capable of coupling said working fluid to a heat source of said heat engine, said thermodynamic system further comprises a condenser common to said air conditioning circuit and to said Rankine thermodynamic cycle system, at least a first ejector and a second ejector being connected to said second evaporator by means of a distribution device, said condenser being connected directly to said pump itself connected directly to said second evaporator, said expansion machine being connected to said second evaporator by means of said distribution, said expansion machine and said at least first ejector and second ejector being connected to said condenser via a combination device.

Preferably, each ejector has a first inlet connected to said first evaporator and a second inlet connected to said second evaporator.

Preferably, said air conditioning circuit and said Rankine thermodynamic cycle system use the same organic-type working fluid.

According to a preferred embodiment, said working fluid is water, carbon dioxide or a refrigerant fluid, for example of the R-1234yf type.

Advantageously, said second evaporator is installed on a cooling circuit of said heat engine.

Advantageously, said cooling circuit comprises a coolant outlet box, said second evaporator being installed between an outlet of said coolant outlet box and a radiator of said vehicle.

Preferably, each ejector comprises a convergent then divergent nozzle.

Preferably, said expansion machine is an axial or radial turbine, or a piston machine.

Advantageously, said thermodynamic system comprises a first ejector, a second ejector and a third ejector connected to said condenser via said combination device and to said second evaporator via said distribution device.

Preferably, the expansion machine is connected to an electricity generator or to the crankshaft of said heat engine.

An embodiment of the present invention will be described below, by way of non-limiting examples, with reference to the appended figures in which:

schematically illustrates a Rankine loop thermodynamic system as known from the prior art;

schematically illustrates a thermodynamic ejector air conditioning system as known from the prior art;

schematically illustrates an embodiment of the thermodynamic system according to the invention;

is a graphical representation of the entropy diagram of the working fluid used in the thermodynamic system according to the present invention;

is a schematic representation illustrating the contribution of the Rankine cycle system to the overall efficiency of the heat engine when the heat source consists of the coolant of the heat engine;

is a schematic representation illustrating the contribution of the Rankine cycle system to the overall efficiency of the heat engine when the heat source consists of the exhaust gases from the heat engine.

Figure 3 schematically illustrates an embodiment of the present invention. The thermodynamic system 30, according to the invention, has an air conditioning circuit 42, also called air conditioning loop, and a recovery loop 43, also called Rankine loop. The air conditioning circuit 42 comprises a holder 36, a first evaporator 33 to absorb the heat coming from the passenger compartment of the vehicle, a first ejector 31a, a second ejector 31b, a third ejector 31c and a condenser 35. The recovery loop 43 is intended to recover energy dissipated by the heat engine of the vehicle and comprises a pump 34 suitable for increasing the pressure of the working fluid of the thermodynamic system 30, a second evaporator 32, also called a boiler, for coupling the working fluid to a source heat from the heat engine. The recovery loop 43 also uses the condenser 35. In addition, the recovery loop 43 comprises an expansion machine 39 able to produce a work-producing expansion, in order to supply, for example, an electricity generator. In a preferred embodiment, the expansion machine 39 is a turbine, radial or axial. The expansion machine 39 can also be a scroll expander, a piston expander, a screw expander, a Wankel engine or an impulse turbine.

The first ejector 31a comprises a first inlet 45a connected to the first evaporator 33 via a first distribution device 47, for example a three-way valve, and a second inlet 44a connected to the second evaporator 32 via a second distribution device 41, for example a three-way valve. The first ejector 31a also includes an outlet 46a. The second ejector 31b comprises a first inlet 45b connected to the first evaporator 33 via said first distribution device 47 and a second inlet 44b connected to the second evaporator 32 via said second distribution device 41. The second ejector 31b comprises also a 46b exit. The third ejector 31c comprises a first inlet 45c connected to the first evaporator 33 via said first distribution device 47 and a second inlet 44c connected to the second evaporator 32 via said second distribution device 41. The third ejector 31c comprises also a 46c output. Each ejector 31a, 31b, 31c further comprises a convergent then divergent nozzle. The working fluid penetrating through the second inlet 44a, 44b, 44c of each ejector 31a, 31b, 31c expands so as to suck the working fluid penetrating through the first inlet 45a, 45b, 45c of each ejector 31a, 31b, 31c . The working fluids coming from the first inlet 45a, 45b, 45c and from the second inlet 44a, 44b, 44c mix to then exit through the outlets 46a, 46b, 46c of each ejector 31a, 31b, 31c. Each output 46a, 46b, 46v is connected to the condenser 35 via a combination device 40, for example a three-way valve. In a first embodiment of the invention, the first ejector 31a has a section of 1.50 mm, the second ejector 31b has a section of 1.60 mm, and the third ejector 31c has a section of 1.70 mm. . Thus, the section of each ejector 31a, 31b, 31c is adapted to a given flow rate range, consequently allowing improved efficiency of the air conditioning loop 42. Indeed, the working fluid circulating in the air conditioning loop 42 has a flow rate which varies according, in particular, to the temperature outside the passenger compartment of the vehicle and the number of passengers transported. In this embodiment of the invention, the first ejector 31a, the second ejector 31b and the third ejector 31c operate simultaneously. Alternatively, a valve (not shown) is connected to the first inlet 45a, 45b, 45c of each ejector 31a, 31b, 31c, in order to control them, thus making it possible to activate a single ejector 31a, 31b, 31c at the times or two ejectors 31a, 31b, 31c simultaneously or the three ejectors 31a, 31b, 31c simultaneously in order to select the best combination for a given flow rate range and thus improve the efficiency of the air conditioning loop 42. In another embodiment , the thermodynamic system 30 comprises only a first ejector 31a and a second ejector 31b. In yet another embodiment, the thermodynamic system 30 includes four ejectors. In other embodiments of the invention, the thermodynamic system 30 comprises more than four ejectors.

The circulation of the working fluid in the air conditioning loop 42 is described below. After having passed through the expansion valve 36, the working fluid passes inside the evaporator 33 within which the fluid absorbs the heat from the cabin air by changing its physical state, that is to say by passing in the gas phase. At the outlet of the evaporator 33, the working fluid circulates to the first ejector 31a, second ejector 31b and third ejector 31c which compress it. The working fluid in the form of high pressure gas at the outlet of the expansion machine 39 is introduced into the condenser 35 within which the gas gives up its heat to the outside air passing through the condenser 35 thanks to the advancement of the vehicle and/or or the operation of the fan motor assembly.

The circulation of the working fluid in the recovery loop 43 is described below. The working fluid at the outlet of condenser 35 is compressed by pump 34 in order to increase its pressure. The fluid then passes through the evaporator 32 in which it is heated and vaporized thanks to a heat exchange between the heat source and the working fluid. At the outlet of the evaporator 32, the working fluid has a higher enthalpy and then passes, in part, into the expansion machine 39, for example a turbine, in which it undergoes work-producing expansion. The expansion machine 39 generally drives an electric generator which makes it possible to reinject the power in electrical form. The working fluid at the outlet of the expansion machine 39 is then condensed in the condenser 35 to then be compressed again.

The configuration of the thermodynamic system 30 thus makes it possible to have simultaneous operation of the recovery loop 43 and the air conditioning loop 42. The condenser 35 is common to the recovery loop 43 and the air conditioning loop 42 thus making it possible to reduce the number of components and thus reduce the mass transported by the vehicle. In addition, the ejectors 31a, 31b, 31c advantageously replace the compressor which is conventionally found in an air conditioning loop, thus allowing a saving in mass and a simplification of the maintenance of said air conditioning loop 42. The working fluid, at high pressure at the outlet of the second evaporator 32, is distributed between the expansion machine 39 and the ejectors 31a, 31b, 31c thanks to the distribution device 41, for example a three-way valve. The distribution device 41 is connected, on the one hand, directly to the expansion machine 39, and on the other hand, directly to the second inlet 44a, 44b, 44c of each ejector 31a, 31b, 31c. Furthermore, the output 46a, 46b, 46c of each ejector 31a, 31b, 31c is directly connected to the combination device 40. The output of the expansion machine 39 is also directly connected to the combination device 40.

According to a particular embodiment, the second evaporator 32 is installed on a cooling circuit of the thermal engine, in particular between an outlet of the coolant outlet box and the radiator of the vehicle. Alternatively, the second evaporator 32 is installed on an exhaust line of the thermal engine, in particular downstream of a catalyst, for example of the SCR type for a "Selective Catalytic Reduction" system, or other, so as not to disturb its operation. Alternatively, the second evaporator 32 combines an evaporator mounted on the heat engine cooling circuit and an evaporator installed on the exhaust line.

Given that the expansion machine 39 can be mounted on the accessories front of the thermal engine, the work produced during the expansion of the working fluid can be directly reinjected mechanically via the transmission device, in particular a belt or chain transmission device, between the compressor and the heat engine crankshaft.

The Rankine cycle system 43 and the air conditioning circuit 42 use the same organic-type working fluid. In another embodiment, the working fluid is water or carbon dioxide. The working fluid is advantageously a refrigerant, for example of the 1234yf type. Figure 4 shows the entropic diagram or T (Temperature)-S (Entropy) diagram of such a fluid of isentropic nature. It is observed that the slope of the diagram in the part which delimits the two-phase zone Z_D (liquid-vapor) from the vapor zone Z_V is vertical (infinite slope). The zone of the Z_L diagram corresponds to the zone in the liquid state.

Figures 5 and 6 highlight the energy gain provided by the Rankine cycle system 43. In a conventional heat engine, energy is rejected in the form of heat mainly via the engine coolant and the exhaust gases. System 43 makes it possible to recover part of this thermal energy to transform it into mechanical energy and reinject it into the traction chain in order to improve the overall efficiency of the powertrain.

Thus, as shown in Figure 5, when the fuel generates a power of 100 kW, part of this power (33 kW) is lost at the exhaust Ech and part of this power (37 kW) is useful for rotation Motor rot. In the case where the second evaporator 32 is arranged on the cooling circuit Ref of the engine, the Rankine loop system 43, which has an efficiency of 5%, makes it possible to recover 1.5 kW of mechanical power for the Rot rotation of the heat engine, the rest being rejected in the form of heat Chal.

Alternatively, as shown in Figure 6, in the case where the second evaporator 32 is arranged on the exhaust duct Ech, the Rankine loop system 43, which then has an increased yield of 18%, makes it possible to recover 1.5 kW of mechanical power for Rot rotation of the heat engine.

Claims (10)

Thermodynamic system (30) for a vehicle, in particular a car, equipped with a heat engine comprising:
- an air conditioning circuit (42) comprising:
- a first evaporator (33) capable of absorbing heat coming from the passenger compartment of said vehicle, and
- a holder (36),
- a Rankine thermodynamic cycle system (43) capable of recovering energy from said heat engine comprising:
- an expansion machine (39), such as a turbine,
- a pump (34) capable of increasing the pressure of a working fluid, and
- a second evaporator (32) capable of coupling said working fluid to a heat source of said heat engine,
characterized in that said thermodynamic system (30) further comprises a condenser (35) common to said air conditioning circuit (42) and to said Rankine thermodynamic cycle system (43), at least a first ejector (31a) and a second ejector (31b) being connected to said second evaporator (32) via a distribution device (41), said condenser (35) being connected directly to said pump (34) itself connected directly to said second evaporator (32) , said expansion machine (39) being connected to said second evaporator (32) via said distribution device (41), said expansion machine (39) and said at least first ejector (31a) and second ejector (31b) being connected to said condenser (35) via a combiner (40). Thermodynamic system (30) according to Claim 1, characterized in that each ejector (31a, 31b, 31c) comprises a first inlet (45a, 45b, 45c) connected to the said first evaporator (33) and a second inlet (44a, 44b, 44c ) connected to said second evaporator (32). Thermodynamic system (30) according to any one of the preceding claims, characterized in that the said air conditioning circuit (42) and the said Rankine thermodynamic cycle system (43) use the same working fluid of the organic type. Thermodynamic system (30) according to Claim 3, characterized in that the said working fluid is water, carbon dioxide or a refrigerant fluid, for example of the R-1234yf type. Thermodynamic system (30) according to any one of the preceding claims, characterized in that the said second evaporator (32) is installed on a cooling circuit of the said heat engine. Thermodynamic system (30) according to Claim 5, characterized in that the said cooling circuit comprises a coolant outlet box, the said second evaporator (32) being installed between an outlet of the said coolant outlet box and a radiator of the said vehicle. Thermodynamic system (30) according to any one of the preceding claims, characterized in that each ejector (31a, 31b, 31c) comprises a convergent then divergent nozzle. Thermodynamic system (30) according to any one of the preceding claims, characterized in that the said expansion machine (39) is an axial or radial turbine or a piston machine. Thermodynamic system (30) according to any one of the preceding claims, characterized in that the said thermodynamic system (30) comprises a first ejector (31a), a second ejector (31b) and a third ejector (31c) connected to the said condenser (35) through said combiner (40) and said second evaporator (32) through said distribution device (41). Thermodynamic system (30) according to any one of the preceding claims, characterized in that the expansion machine (39) is connected to an electricity generator or to the crankshaft of the said heat engine.