Classifications

• • 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
  • F01B27/00—Starting of machines or engines
  • F01B27/02—Starting of machines or engines of reciprocating-piston engines
  • F01B27/04—Starting of machines or engines of reciprocating-piston engines by directing working-fluid supply, e.g. by aid of by-pass steam conduits

Definitions

• the present invention relates to the field of expansion machines converting waste heat from an internal combustion engine in a Rankine cycle into mechanical energy that can be transferred to a shaft driving the internal combustion engine.
• the field of application concerns all types of internal combustion engine, for example those fitted to vehicles and in particular trucks, buses and passenger cars.
• the expansion machines can be of several types: ⁇ turbomachines using a turbine
• volumetric machines using one or more pistons acting on a linkage which may be constituted by a plate inclined (“swashplate” in English) or oscillating ("wobble plate” in English), or a linkage rod-type crank, or still a spiral (“scroll” in English) or a screw (“screw” in English).
• a linkage which may be constituted by a plate inclined (“swashplate” in English) or oscillating ("wobble plate” in English), or a linkage rod-type crank, or still a spiral (“scroll” in English) or a screw (“screw” in English).
• a volumetric expansion machine generally comprises an intake port connected to a channel intake and an exhaust port connected to an exhaust channel. These two intake and exhaust ports are formed in the body of the machine.
• Such a machine is generally composed of three zones: a high pressure inlet zone, an expansion zone and a low pressure exhaust zone.
• the intake zone is connected to the expansion zone, itself connected to the exhaust zone.
• the expansion zone is formed by moving means.
• the exhaust zone comprises a transmission of the force produced by the moving means to a rotating shaft.
• a bypass channel extends from the high pressure inlet zone to the low pressure exhaust zone.
• a bypass valve is connected to or integrated into the intake zone and opens or closes the bypass channel according to its open or closed position.
• the invention relates more particularly to the different modes of operation of such a volumetric machine and its coupling to the internal combustion engine.
• the machine When stopped, the machine is in a first mode of operation, called “idle state", where the machine is filled with working fluid in the liquid state.
• the bypass valve is then in the open position.
• the prior art is known from the international patent application WO2017008094 describing a method of controlling a waste heat recovery system for an internal combustion engine of a vehicle, this waste heat recovery system having at least an expansion machine transmitting a torque to the internal combustion engine and which can be bypassed via a bypass flow path, at least one evaporator and at least one pump for a working fluid, said at least one evaporator being arranged in the region of the exhaust system of the internal combustion engine.
• the expansion machine can operate in different modes. It is connected in drive, in at least one mode of operation, to an auxiliary drive shaft of the internal combustion engine. On the basis of at least one input variable, an operating mode is selected by a controller and the waste heat recovery system then operates in this mode.
• the input variable is selected from the group consisting of the following: speed of rotation of the expansion machine (n), information on the gear ratios (GI), retardation information (CI), pressure (pl, p2) and temperature (T1, T2) of the working fluid upstream and downstream of the expansion machine via the control device.
• a first mode of operation is associated with a temperature-setting phase of the expansion machine, and a second mode of operation with a normal operating phase of the expansion machine.
• the bypass flow path is open and the expansion machine is not connected to an auxiliary drive shaft of the internal combustion engine.
• the bypass flow path is closed and the expansion machine is connected to the internal combustion engine.
• the second mode is selected when the pressure (p2) and / or the temperature (T2) of the working fluid downstream of the expansion machine exceeds a defined value.
• patent AT512921 describing a method of connecting a storage tank to the control valves and a feed pump.
• the control valves distribute the working fluid to the heat exchangers.
• An expansion machine is connected downstream of the heat exchanger to a condenser.
• the condenser is connected to a circulation pump which is connected to the storage tank.
• the working fluid is transmitted to the heat exchangers.
• the mass flow of the working fluid in the heat exchangers is controlled by the control valves to achieve a predetermined superheat of the working fluid.
• the Rankine cycle thus described further comprises a switching valve in a controlled manner between a first direct flow path to the expansion machine, or a second flow path through a rolling valve.
• This patent describes the control method of such a system for carrying out an expansion operation according to the following steps: a) the heating operation
• the working fluid at the outlet of the heat exchanger is two-phase at the temperature of the saturated steam.
• the mass flow of working fluid is reduced through a control valve, a rise in temperature occurs and the overheating process is achieved.
• the second path through the rolling valve is selected.
• the temperature of the working fluid vapor is controlled to be greater than the temperature of the saturated vapor by a predetermined value.
• the second path through the rolling valve is selected. d) operate the relaxation machine
• the first direct flow path to the expander is selected and the machine is started.
• German patent DE102015204385 describing another known example of axial piston machine comprising a rotor rotatably mounted in a housing, cylinders arranged around the rotor, in which pistons are arranged in translation.
• patent WO201708094 relates to a Rankine cycle machine using a turbine and not a volumetric type machine. Secondly, the control of the passage between the first mode of operation and the second mode of operation is based on the pressure and / or the temperature measured at the outlet of the exhaust of the machine.
• the object of this patent concerns the transition between the bypass mode and the operating mode. This passage is a critical technical issue.
• the derivation mode is not productive. It must last the least possible to maximize the mechanical production of the expansion machine.
• bypass mode The role of the bypass mode is to move from a rest mode to the operating mode by converging a set of parameters to values accepted by the machine so that its lubrication is ensured and it does not wear out. neither breaks.
• a set of sensors is judiciously placed to determine the state of the expansion machine as quickly as possible without waiting for the slow convergence of sensors external to the machine due to the thermal inertia of the system. .
• the present invention relates in its most general sense to a volumetric expansion machine according to claim 1, taken alone or in combination with one or more of the dependent claims.
• the invention differs in particular from the solutions of the prior art in that the temperature is measured not not in the exhaust, but in the expansion zone.
• This solution unlike those proposed in the prior art, allows to take into account the actual state of the working fluid in the expansion zone. This solution makes it possible to prevent the fluid from being liquid, and to check the state of overheating before starting.
• One of the beneficial consequences is a faster start compared to the solutions of the prior art.
• the invention also relates to a method of controlling such a volumetric expansion machine according to claim 8 taken alone or in combination with one or more of the dependent claims.
• FIG. 1 represents a schematic view of a Rankine cycle according to the invention
• FIG. 2 represents the control method of the expansion machine
• FIG. 3 represents a schematic view of the starter of the expansion machine
• FIG. 4 represents an external isometric view of the expansion machine.
• FIG. 1 represents a schematic view of a Rankine cycle according to the invention.
• a Rankine cycle recovers lost heat from the internal combustion engine (301). This heat can be recovered in several places: on the cooling circuit, on the cooling of the compressed air upstream of the engine, on the cooling of the exhaust gases recirculated in the engine or on the exhaust gases (302) as shown in Figure 1.
• a heat exchanger (307) is inserted bypass on the exhaust line after the pollution control system (303).
• a bypass valve (327) proportionally distributes the flow rates between the heat exchanger (307) and the normal exhaust.
• the exchanger (307) is an evaporator for evaporating the working fluid (308) from the Rankine cycle.
• the working fluid (308) is drawn by the pump (306) from an expansion tank (328) at a pressure controlled by the electric valve (329).
• the proportional electric valve (329) regulates the air pressure in the expansion tank (328) either by connecting the expansion vessel to the compressed air source (321) or by connecting the expansion tank ( 328) to the atmosphere.
• the temperature and pressure of the working fluid upstream of the pump and downstream of the evaporator (307) are measured by sensors.
• the Rankine cycle calculator receives these signals to control the actuators of the system and a temperature of the vapor in the expansion machine (304) measured either in the expansion zone (316) or in the exhaust zone ( 317).
• the vapor produced in the evaporator (307) flows to the expansion machine (304).
• the expansion machine has three zones: the inlet zone (314) of the high pressure steam which is connected to the expansion zone (316), itself connected to the exhaust zone (317) at low pressure.
• the bypass valve (315) opens and closes a bypass channel connecting the intake zone (314) and the exhaust zone (317).
• This bypass valve (315) is advantageously pneumatic and is connected to a source of compressed air (321).
• An electric valve (320) controls the admission of air into the bypass valve (315) either by connecting the bypass valve to the source of compressed air (321) or by connecting the bypass valve (315) to the atmosphere.
• the bypass channel or the bypass valve further comprises a restriction, typically of the order of 20 mm 2 in order to limit the volume flow through the bypass channel and to cause a rise in pressure of the zone upstream of the restriction.
• the low pressure steam escaping from the expansion machine (304) from the exhaust zone (317) flows in a condenser (305) to return to the liquid state.
• the condenser (305) is cooled by either a fluid of the internal combustion engine (301) or by ambient air. For example, one or more of the engine cooling circuits (301) may be used.
• the condensed working fluid then returns to the expansion vessel (328).
• the expansion machine (304) is connected to a rotating shaft (313) of the internal combustion engine (301).
• a first seal (309) is disposed on the shaft closest to the exhaust zone (317) to limit the volume of the area containing the working fluid. This seal serves to seal the Rankine cycle circuit and to prevent leakage of working fluid out of the cycle as well as the ingress of air into the circuit.
• the expansion machine (304) is fixed to the motor (301) by a flange (319) and optionally other fastening means.
• the fixing by a single flange is interesting because it limits the number of interfaces with the motor (301) and the machine (304) can then be fixed as an accessory (hydraulic pump, ...) on a power take-off of the motor (301).
• the flange can be set back from the transmission of the expansion machine (304) so that a part of this transmission enters the motor (301) to connect to the rotating shaft (313) at the inside of it.
• gears (312) make it possible to adapt the speed of rotation of the motor shaft (313) to that of the expansion machine (304), which generally rotates more rapidly.
• the speed ratio is fixed and is typically between 1 and 4.
• a freewheel (311) is disposed at the output of the gears on the side of the expansion machine (304). This allows rotation of the motor (301) without the expansion machine (304) being rotated. When the expansion machine (304) rotates at the same speed as the motor (301), the freewheel (311) is blocked and the expansion machine (304) can transmit torque to the motor shaft (313).
• a second seal (330) on the shaft seals the engine (301) and prevents engine oil from escaping.
• the gears (312) and the freewheel (311) are lubricated by the engine oil (301).
• the resilient element (310) is used to shift the resonant frequencies of the shaft line due to the excitations of the angular accelerations due to both the expansion machine (304) and the motor (301) to avoid breakage. of the transmission from the expansion machine (304) to the engine (301).
• the elastic element (310) is composed of elements of low torsional stiffness to exclude the resonance peaks from the operating range.
• the elasticity is generally obtained using an elastomeric disc (for example polyurethane).
• the hardness of the elastomer and the inertia of the disk make it possible to adjust the natural frequencies of the transmission according to the mechanical characteristics of the engine (301). Elasticity can also be achieved with devices having two parts connected by springs or permanent magnets.
• the relative positioning of the shaft line elements between the gears (312) and the first seal (309), i.e. the freewheel assembly (311) joined (330) elastic member (310) and starter (318), can be arranged differently depending on the external conditions (bulk).
• the freewheel (311) may be disposed directly after the first seal (309) and after the starter (318) without this calling into question the operation of the line.
• the starter (318) makes it possible, during the transition from the bypass mode (102) to the operating mode (104), to start the rotation of the expansion machine (304) if the latter does not start by itself. Indeed, some piston expansion machines need to overcome a start torque before being driving.
• This starter is advantageously pneumatic and connected on the same compressed air line as the bypass valve (315) and is therefore controlled by the same electric valve (320) as the bypass valve (315). This reduces the number of actuators and connections to the computer.
• the starter (318) may further comprise a torque limiter to avoid forcing the start and therefore the rotation of the machine (304) if it is blocked, for example, by liquid working fluid.
• FIG. 1 shows the control method of the expansion machine.
• the machine When stopped, the machine is in a first mode of operation, called “idle state" (100), where the machine (304) is filled with working fluid (308) in the liquid state.
• the bypass valve (315) is then in the open position.
• bypass valve (315) is advantageously of the pneumatic type.
• An electric valve (320) for controlling compressed air opens or closes the compressed air duct (321) to the bypass valve (315).
• the bypass valve (315) is open in the absence of compressed air and closed when a certain pressure of compressed air is applied to it (typically 6 to 8 bar relative).
• the operating conditions of the machine are a set of control laws selected from, but not limited to, the following examples:
• the temperature of the measured vapor is higher than a few degrees (typically 5 ° C) at the saturation temperature of the working fluid at the pressure measured in the exhaust zone (317)
• the temperature of the vapor admitted into the intake zone (314) is a few degrees higher (typically 5 ° C) than the saturation temperature of the working fluid at the pressure of the vapor admitted into the intake zone ( 314)
• the temperature of the vapor escaped from the exhaust zone (317) is a few degrees (typically 5 ° C) higher than the saturation temperature of the working fluid at the pressure of the vapor escaped from the exhaust zone ( 317)
• the temperature of the vapor admitted into the intake zone (314) is below a maximum threshold (typically 225 ° C or 250 ° C).
• a maximum threshold typically 35 or 40 absolute bars
• timers can be implemented on all or part of these conditions in order to filter out temporary changes and to avoid inadvertent mode changes.
• the expansion machine can accept saturated steam at intake or exhaust for 30 seconds.
• the "bypass" (102) or "in operation” operating modes (104) are exited, when a stop command is given for the Rankine cycle or when failures are detected. For example, stopping the vehicle engine leads to a stop order of the Rankine cycle.
• the system then returns to the idle state (100).
• the expansion machine (304) will then gradually be flooded by the working fluid in the liquid state as the temperature of the system falls.
• the liquid working fluid (308) contained in an expansion vessel (328) placed between a condenser (305) and a pump (306) of the Rankine cycle is vented to atmospheric pressure or pressurized by the valve proportional electric (329). The descent into temperature of the system tends to create a depression in the system.
• the system draws the liquid working fluid (308) contained in the expansion vessel (328) to have only a single liquid phase at substantially atmospheric pressure or at a substantially higher pressure throughout the system. system.
• the entry of air into the circuit, and therefore oxygen deleterious to the life of fluids and materials, is limited.
• it may be rotating or not. Its output shaft is mounted on a freewheel (311).
• the motor (301) can rotate freely without the trigger machine (304) rotating. Whatever the mode, when the conditions are right, the machine starts spinning freely. When its speed reaches that of the motor, the freewheel (311) is blocked and the machine (304) is connected to the motor (301): it then provides torque and thus contributes to the reduction of the motor consumption (301).
• the machine disconnects freely when it does not turn fast enough. For example, when the pressure difference between the inlet (314) and the exhaust (317) is not high enough (typically less than 5 bars), then the efficiency of the machine does not allow its rotation whatever the mode of operation.
• the starter (318) is advantageously actuated at the same time as the bypass valve (315) during the transition from the bypass mode (102) to the operating mode (104).
• the starter (318) is inactive in the absence of compressed and active air when a certain pressure of compressed air is applied to it (typically 6 to 8 bar relative).
• a certain pressure of compressed air typically 6 to 8 bar relative.
• the expansion machine (304) would not start under the action of the starter (318)
• the inlet vapor pressure would increase rapidly to get out of the operating condition limits and again to switch the control to bypass (102), bypass valve (315) open.
• the conditions would be checked again and the computer would launch a second start test by going again from mode (102) to mode (104).
• FIG. 3 shows a starter scheme (318).
• FIG. 4 represents an isometric view of a piston volumetric expansion device (304) having a pneumatic starter (318).
• the starter (318) is composed of a pneumatic actuator having a body (205), attached to the body of the machine (304) by a first pivot connection (204), and a rod (203).
• the rod (203) is connected by a pivot connection (202) on a lever arm (201) mounted on a free wheel (207).
• the freewheel (207) in turn actuates the shaft (200) of the expansion machine (304).
• the starter is configured to force the rotation of the expansion machine (304) in a given direction and a few degrees (typically between 20 and 60 °). In doing so, the machine becomes driving and starts to turn faster and faster. It disconnects from the starter with the freewheel (207), then when it reaches the speed of the motor (301) it connects to the motor shaft (313) through the freewheel (311).
• the starter (318) is not positioned as shown in Figure 1, i.e. after the seal (309) on the shaft of the expansion machine ( 304) in the direction of the motor (301). It is placed axially on the other side of the machine.
• the starter is also more complex than illustrated in Figure 3 because it has a bevel gear made by intermediate pieces (208, 209).
• the machine (304) has a high pressure inlet port (212) and a bypass valve (315).
• a pneumatic cylinder (205) has a compressed air inlet (206) and a rod (203).
• the rod (203) under the action of compressed air can exit the body (205) or enter it in the absence of compressed air pressure by means of a return spring integrated into the body ( 205).
• An intermediate lever arm (208) allows transmission of the movement of the rod.
• this lever arm makes it possible to increase the transmitted force by reducing the movement so that a small jack (205) makes it possible to obtain sufficient torque when starting the machine (304).
• This intermediate lever arm (208) pivots on its link (210) and actuates an intermediate rod (209).
• This intermediate rod (209) in turn actuates a lever arm (201) mounted on the wheel free (207) fixed on the shaft (200) of the machine (304).
• the pivot connection (210) and the cylinder body (205) are fixed to the machine (304) by means of a fastener (211).
• a fixing port (213) of a temperature sensor is located on the machine. This allows the measurement via a temperature sensor of the temperature in the expansion zone (316) of the machine. This sensor is placed on one of the cylinders. It is preferentially the cylinder which reaches last the criterion of starting.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Engine Equipment That Uses Special Cycles (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=60202152

Family Applications (1)

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• 2017
  • 2017-08-07 FR FR1757571A patent/FR3069882A1/fr not_active Ceased
• 2018
  • 2018-04-27 WO PCT/FR2018/051073 patent/WO2019030435A1/fr not_active Ceased
  • 2018-04-27 EP EP18726522.8A patent/EP3665366A1/de not_active Withdrawn

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