Patent ID: 12255521

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of a trilateral cycle system according to the present disclosure will be described. In the drawings, white arrows indicate a flow of exhaust heat, and filled arrows indicate a flow of a working fluid. In the drawings, dimensions of members are changed for easy understanding of the configuration, and are not always matched with those actually manufactured. Hereinafter, in the present disclosure, a passage indicates a portion through which the working fluid flows, and a pipe indicates a member constituting the passage.

As illustrated inFIG.1, a trilateral cycle system10of the embodiment is a system for converting exhaust heat from an engine (not illustrated) into electric power and recovering the electric power. The exhaust heat of the engine is, for example, exhaust gas generated by combustion of fuel and cooling water for cooling heat generated by combustion. In the trilateral cycle system10, a state of a working fluid flowing into the expander14is not dry steam, but is a gas-liquid two-phase state, and the exhaust heat can be recovered even when the exhaust heat of the engine is at a low temperature of 100° C. or less. Therefore, as a heat source of the trilateral cycle system10, cooling water of the engine is suitable, and the trilateral cycle system10of the present embodiment adopts the cooling water as the exhaust heat. The working fluid of the trilateral cycle system10is, for example, ethanol.

In the trilateral cycle system10, a pump12, a heat exchanger13, an expander14, and a condenser15are arranged in this order with respect to a flow of the working fluid in a circulation passage11through which the working fluid circulates. The trilateral cycle system10includes a power generator16connected to the expander14.

The working fluid circulated by the pump12through the circulation passage11is heated by heat exchange with the cooling water of the engine in the heat exchanger13, and becomes a working fluid in a gas-liquid two-phase flow. The working fluid in the gas-liquid two-phase flow passes through the heat exchanger13and then drives the expander14. The working fluid drives the expander14, then is cooled by the condenser15, and returns to the pump12again. Electric power generated by the power generator16when the expander14is driven is stored in a battery (not shown).

The trilateral cycle system10includes a housing20and a cooling passage21. The trilateral cycle system10has a structure in which the expander14and the power generator16are accommodated inside one housing20, and inside the housing20, an output shaft17of the expander14and a drive shaft18of the power generator16are coaxially arranged and directly connected. In the trilateral cycle system10, the power generator16is disposed at an intermediate position of a passage19which exists between the heat exchanger13and the expander14in the circulation passage11and through which the working fluid in the gas-liquid two-phase flow after passing through the heat exchanger13flows, and the cooling passage21for cooling the power generator16forms a part of the passage19. In the drawing, a hatched portion indicates the passage19.

InFIG.2, an X direction indicates an axial direction of the output shaft17and the drive shaft18, and a Y direction indicates a direction orthogonal to the X direction. In the present disclosure, a leading end and a trailing end are based on the flow of the working fluid, the leading end indicates one end existing on an upstream side, and the trailing end indicates the other end existing on a downstream side.

As illustrated inFIG.2, the expander14includes a fluid device14athat converts energy of the working fluid in the gas-liquid two-phase flow into rotational motion of the output shaft17, and an expander housing14bthat accommodates the fluid device14a. Examples of the fluid device14ainclude a turbo type (centrifugal turbine or axial flow turbine) and a displacement type (vane expander, scroll expander, screw expander), and are not particularly limited. The expander14of the present embodiment employs a rotary expander in which the fluid device14ahas a structure in which a vane slides on an outer peripheral surface or an inner peripheral surface of a piston.

The power generator16includes a rotor16afixed to the drive shaft18, and a stator16bdisposed around the rotor16aand fixed to the housing20. The power generator16is electrically connected to a battery via an inverter (not shown). The cooling passage21for cooling the power generator16is formed inside the power generator16.

The housing20has a sealed structure, the power generator16is accommodated on the upstream side and the expander14is accommodated on the downstream side with respect to the flow of the working fluid in the gas-liquid two-phase flow. An inlet pipe22and an outlet pipe23are connected to the housing20.

The inlet pipe22is one of pipes constituting the passage19, and is a pipe through which the working fluid in the gas-liquid two-phase flow after passing through the heat exchanger13flows inside the housing20. A trailing end of the inlet pipe22is disposed inside the housing20. The outlet pipe23is a pipe through which the working fluid after passing through the expander14flows out to an outside of the housing20.

The cooling passage21is a part of the passage19, and is a passage having a leading end communicating with the inlet pipe22, an intermediate position passing through the power generator16, and a trailing end communicating with an inlet14cof the fluid device14aof the expander14. The cooling passage21is a passage through which the working fluid in the gas-liquid two-phase flow flows, and a drive-shaft-applied passage24, an output-shaft-applied passage25, and a communication passage26are disposed in this order from the upstream side with respect to the flow of the working fluid.

The drive-shaft-applied passage24is a passage formed inside the drive shaft18, and the working fluid in the gas-liquid two-phase flow flows therethrough. The drive-shaft-applied passage24has a leading end communicating with the inlet pipe22and a trailing end communicating with the output-shaft-applied passage25. The drive shaft18inside which the drive-shaft-applied passage24is formed is implemented by a pipe, and the rotor16ais fixed to an outer peripheral surface of the pipe.

The output-shaft-applied passage25is a passage formed inside the output shaft17, and the working fluid in the gas-liquid two-phase flow after passing through the drive-shaft-applied passage24flows therethrough. The output-shaft-applied passage25has a leading end communicating with the drive-shaft-applied passage24and a trailing end communicating with the communication passage26. The output shaft17inside which the output-shaft-applied passage25is formed is implemented by a pipe, and the pipe is rotationally driven by the fluid device14a.

The communication passage26is a passage formed in the expander housing14b, and the working fluid in the gas-liquid two-phase flow after passing through the output-shaft-applied passage25flows therethrough. The communication passage26has a leading end communicating with the output-shaft-applied passage25, and a trailing end communicating with the inlet14cof the fluid device14a.

A pipe outer diameter of the drive shaft18is equal to or smaller than a pipe inner diameter of the inlet pipe22. A leading end of the drive shaft18is disposed inside the inlet pipe22. The drive shaft18rotatably communicates with the inlet pipe22through the drive-shaft-applied passage24. It is desirable that the pipe outer diameter of the drive shaft18is smaller than the pipe inner diameter of the inlet pipe22. When the pipe outer diameter of the drive shaft18is smaller than the pipe inner diameter of the inlet pipe22, the outer peripheral surface of the drive shaft18is not in contact with an inner peripheral surface of the inlet pipe22, which is advantageous in reducing a resistance load caused by the contact. When the pipe outer diameter of the drive shaft18is smaller than the pipe inner diameter of the inlet pipe22, a gap is formed between the outer peripheral surface of the drive shaft18and the inner peripheral surface of the inlet pipe22. Since an outlet of the expander14is at a pressure lower than a pressure inside the housing20, the working fluid in the gas-liquid two-phase flow flows from the inlet pipe22to the drive shaft18, and does not leak out from the gap. Even if the working fluid in the gas-liquid two-phase flow leaks out from the gap, the working fluid remains inside the housing20and does not leak out to the outside of the housing20.

A pipe outer diameter of the output shaft17is the same as a pipe inner diameter of the drive shaft18. A leading end of the output shaft17is disposed inside the drive shaft18. An outer peripheral surface of the output shaft17is fixed to an inner peripheral surface of the drive shaft18. It is desirable that the output shaft17extends such that the leading end thereof is positioned at a center portion of the power generator16. When the leading end of the output shaft17is positioned at the center portion of the power generator16, a fixing area between the output shaft17and the drive shaft18increases, which is advantageous for fixing the rotating pipes to each other. In order to increase the fixing area between the output shaft17and the drive shaft18, the leading end of the output shaft17may be disposed upstream of the central portion of the power generator16with respect to the flow of the working fluid. The trailing end of the drive shaft18may protrude from the power generator16toward an expander14side.

A through hole26apenetrating in the X direction is formed in a passage wall surface on an upper side in the X direction at a trailing end portion of the communication passage26. A hole diameter of the through hole26ais equal to or larger than the pipe outer diameter of the output shaft17. The trailing end of the output shaft17protrudes downward in the X direction from the fluid device14aand is disposed inside the trailing end portion of the communication passage26through the through hole26a. The output shaft17rotatably communicates with the communication passage26through the output-shaft-applied passage25. It is desirable that the hole diameter of the through hole26ais larger than the pipe outer diameter of the output shaft17. When the hole diameter of the through hole26ais larger than the pipe outer diameter of the output shaft17, the outer peripheral surface of the output shaft17is not in contact with the expander housing14b, which is advantageous in reducing a resistance load caused by the contact. Similarly, a hole diameter of a through hole14d, which is formed at an upper end of the expander housing14bin the X direction and through which the output shaft17is inserted, is equal to or larger than the pipe outer diameter of the output shaft17, and it is desirable that the hole diameter is larger than the pipe outer diameter of the output shaft17.

The working fluid in the gas-liquid two-phase flow passing through the heat exchanger13flows through the inlet pipe22, the drive-shaft-applied passage24, the output-shaft-applied passage25, the communication passage26, the fluid device14a, and the outlet pipe23in this order. When passing through the drive-shaft-applied passage24, if a temperature of the power generator16is higher than a temperature of the working fluid in the gas-liquid two-phase flow, the working fluid of a liquid phase evaporates and takes evaporation heat from the power generator16in the process of evaporation. As a result, the power generator16is cooled, and the working fluid in the gas-liquid two-phase flow recovers the exhaust heat from the power generator16.

As described above, in the trilateral cycle system10of the present embodiment, the cooling passage21for cooling the power generator16is implemented by a part of the passage19through which the working fluid in the gas-liquid two-phase flow after passing through the heat exchanger13flows. Therefore, according to the trilateral cycle system10, when the working fluid in the gas-liquid two-phase flow in the cooling passage21flows through the cooling passage21, the working fluid of the liquid phase evaporates by the heat of the power generator16, and thus the exhaust heat from the power generator16can be recovered while cooling the power generator16.

A technique of cooling a power generator or a motor generator, that is mounted on a vehicle, with cooling water of an engine is a well-known and common technique. In the trilateral cycle system10of the present embodiment, the cooling water of the engine is used as exhaust heat of the engine. Therefore, the temperature of the working fluid in the gas-liquid two-phase flow flowing into the expander14is lower than the temperature of the cooling water of the engine, and the power generator16can be sufficiently cooled as long as the power generator is a power generator or a motor generator within a category of well-known and commonly used technique. Specifications of the power generator16of the present embodiment can be appropriately changed.

In the trilateral cycle system10, it is desirable that the expander14and the power generator16are accommodated inside the one housing20. As in the present embodiment, since the expander14and the power generator16are accommodated inside the one housing20, even if the working fluid leaks out from the output shaft17of the expander14, the leaked working fluid remains inside the housing20and can be prevented from flowing out to the outside. This makes it possible to reduce a frequency of periodic maintenance caused by the outflow of the working fluid.

In the trilateral cycle system10, it is desirable that the output shaft17of the expander14and the drive shaft18of the power generator16are coaxially arranged, and a passage for the working fluid in the gas-liquid two-phase flow is formed inside each of the shafts. When both the output shaft17and the drive shaft18are constituted by pipes in each of which the shaft-applied passage is formed as in the present embodiment, it is not necessary to separately provide the pipe for forming the cooling passage21. Therefore, an integrated structure in which the expander14and the power generator16are accommodated inside the one housing20can be made compact.

Although the embodiment of the present disclosure has been described above, the trilateral cycle system10of the present disclosure is not limited to a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present disclosure.

As illustrated inFIG.3, the trilateral cycle system10may be configured such that, when the output shaft17of the expander14and the drive shaft18of the power generator16are coaxially arranged and connected to each other, the output shaft17communicates, at an intermediate position thereof, with the communication passage26. In the output shaft17, a solid shaft17aand a hollow shaft17bimplemented by a pipe are coaxially connected, and a trailing end of the hollow shaft17bis disposed inside the communication passage26. The trailing end of the drive shaft18is also disposed inside the communication passage26. A plurality of through holes27are formed in a pipe wall in which two pipes including a trailing end portion of the hollow shaft17band a trailing end portion of the drive shaft18overlap each other. It is desirable to improve the durability, which is lowered by forming the plurality of through holes27in the trailing end portion, by overlapping the trailing end portion of the hollow shaft17band the trailing end portion of the drive shaft18inside the communication passage26.

As illustrated inFIG.4, in the trilateral cycle system10, when the expander14and the power generator16are connected by one output and drive shaft28, a shaft-applied passage29may be formed inside the output and drive shaft28, and the output and drive shaft28may be implemented by a pipe. The rotor16ais fixed to an upper portion of the output and drive shaft28in the X direction, and the fluid device14ais fixed to a lower portion in the X direction.

As illustrated inFIG.5, the output and drive shaft28may include a solid output shaft portion28aand a hollow drive shaft portion28bin which the output shaft portion28ais disposed at an axial center, and the output shaft portion28aand the drive shaft portion28bmay be connected to each other by a connection portion28c. In the output and drive shaft28, the fluid device14aof the expander14is fixed to the output shaft portion28a, and the rotor16aof the power generator16is fixed to the drive shaft portion28b. When the output and drive shaft28is provided, the trailing end of the output and drive shaft28is directly connected to the inlet14cof the fluid device14aof the expander14in the cooling passage21.

As described above, the connection between the expander14and the power generator16and the configuration of the cooling passage21can be appropriately changed depending on specifications of the fluid device14aof the expander14and the durability of each pipe.

The trilateral cycle system10of the present disclosure is not limited to the integrated structure in which the expander14and the power generator16are accommodated inside the one housing20, and the expander14and the power generator16may be provided separately from the circulation passage11of the trilateral cycle system10.

Further, the trilateral cycle system10of the present disclosure is not limited to the configuration in which the cooling passage21is formed inside the output shaft17of the expander14and the drive shaft18of the power generator16, and may be configured such that the shafts and the cooling passage21are separately provided.

The present application is based on the Japanese patent application filed on Mar. 22, 2021 (Patent Application No. 2021-046805), and the contents thereof are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The present disclosure has an effect that, when a working fluid in a gas-liquid two-phase flow flows through a cooling passage, the working fluid of a liquid phase evaporates due to heat of a power generator, thus cooling the power generator and recovering exhaust heat from the power generator, and is useful for a trilateral cycle system or the like.

REFERENCE SIGNS LIST

10trilateral cycle system11circulation passage12pump13heat exchanger14expander15condenser16power generator17output shaft18drive shaft19passage20housing21cooling passage