JP7334405B2 - Rankine cycle system - Google Patents

Description

The present disclosure relates to Rankine cycle systems.

A Rankine cycle system has been proposed in which part of the energy of the engine exhaust is recovered, the recovered energy is used to drive an expander connected to the engine, and this driving force is used to assist the engine (for example, See Patent Document 1).

Japanese Patent Application Laid-Open No. 2018-17203

In the Rankine cycle system described above, the piping for the working fluid between the outlet of the evaporator and the inlet of the expander in the system is exposed to the outside air so that the working fluid is cooled by the outside air while passing through this piping. , the power that can be output by the inflator is reduced.

An object of the present disclosure is to provide a Rankine cycle system capable of suppressing reduction in power that can be output by an expander.

A Rankine cycle system according to an aspect of the present invention for achieving the above object includes an evaporator that exchanges heat between a working fluid and exhaust gas passing through an exhaust pipe of an internal combustion engine, and a working fluid that has undergone heat exchange with the exhaust gas in the evaporator. and an expander that expands to output power, at least between the outlet of the evaporator and the inlet of the expander in a working fluid pipe through which the working fluid passes The temperature adjustment unit, which is a part, branches from a main exhaust pipe through which exhaust gas used for heat exchange in the evaporator passes upstream of the evaporator and is downstream of the evaporator. By joining the pipes, it is covered with a bypass pipe that bypasses the evaporator, and by exchanging heat between the exhaust gas flowing through the bypass pipe and the working fluid, the temperature of the working fluid passing through the inlet of the expander is reduced. A configuration is provided to bring the temperature above the temperature of the working fluid passing through the outlet of the evaporator.

According to the present disclosure, it is possible to suppress reduction in the power that can be output by the expander.

It is a figure which illustrates the Rankine cycle system of 1st Embodiment. It is a figure which illustrates the Rankine cycle system of 2nd Embodiment.

The Rankine cycle system of the present disclosure will be described below with reference to the drawings. As illustrated in FIG. 1, the Rankine cycle system 1 of the first embodiment includes a tank, a pump, an evaporator 3, an expander 4, and a and a condenser.

The working fluid flow path 2 is a closed flow path through which the working fluid W is circulated. The tank is a device that is arranged in the working fluid flow path 2 and stores the working fluid W. As shown in FIG. The pump is a device that is arranged in the working fluid flow path 2 on the downstream side of the tank and applies driving force for circulation in the flow path 2 to the working fluid W that has flowed in from the tank. The evaporator 3 is arranged in the working fluid flow path 2 on the downstream side of the pump, and is a device that exchanges heat between the working fluid W and the exhaust gas G passing through the exhaust pipe 5 of the engine (internal combustion engine). Due to this heat exchange, most of the working fluid W is heated by the exhaust gas G and evaporated. The expander 4 is a device arranged in the working fluid flow path 2 on the downstream side of the evaporator 3 to expand the working fluid W heat-exchanged with the exhaust gas G in the evaporator 3 to output power. A driving device (engine, motor, etc.) is connected to the output shaft 4a of the expander 4 via a connecting/disconnecting device (clutch, etc.). The resulting power is transmitted to the driving device. The condenser is a device that is arranged downstream of the expander 4 and upstream of the tank in the working fluid flow path 2 to condense the working fluid W. As shown in FIG.

In the Rankine cycle system 1 of the present embodiment, the temperature of at least a part of the pipe 2a between the outlet of the evaporator 3 and the inlet of the expander 4 in the working fluid pipe 2 through which the working fluid W passes. Exhaust gas G flowing through the exhaust pipe 5 upstream of the evaporator 3 and the working fluid W are heat-exchanged in the adjustment unit 2 b.

In the Rankine cycle system 1 of the first embodiment, as illustrated in FIG. 1 , the temperature control section 2b is configured to be covered with the exhaust pipe 5 upstream of the evaporator 3 . The working fluid W passing through the temperature adjusting portion 2b exchanges heat with the exhaust gas G flowing through the exhaust pipe 5 covering the temperature adjusting portion 2b. The range of the temperature adjustment part 2b in the pipe 2a between the outlet of the evaporator 3 and the inlet of the expander 4 is the temperature of the working fluid W passing through the outlet of the evaporator 3. is set above the temperature of

Regarding the pipe 2a for the working fluid between the outlet of the evaporator 3 and the inlet of the expander 4, the temperature control unit 2b is a continuous pipe, and this pipe 2b is divided into a pipe 2ba and a pipe 2bb depending on its shape. divided into The pipe 2ba is formed by extending the central portion of the cross section of the exhaust pipe 5 from the first outer wall surface 5a of the exhaust pipe 5 in the direction in which the exhaust gas G passes. The pipe 2bb is a pipe that communicates with one end 2c of the pipe 2aa opposite to the first outer wall surface 5a and extends in the radial direction of the exhaust pipe 5 to the second outer wall surface 5b of the exhaust pipe 5. .

By forming the pipe 2ba so that the central part of the cross section of the exhaust pipe 5 extends in the passage direction of the exhaust gas G, the exhaust gas G having a higher temperature than the exhaust gas G passing through the outer peripheral part of the cross section of the exhaust pipe 5 is formed. and the working fluid W can be heat-exchanged. Therefore, the temperature rise performance of the working fluid W is improved. Further, by forming the pipe 2bb communicating with the pipe 2ba so as to extend in the radial direction of the exhaust pipe 5, the pipe 2b can be easily connected to the expander 4. As shown in FIG.

In the Rankine cycle system 1 of the second embodiment, as illustrated in FIG. 2, a bypass pipe 6 that bypasses the evaporator 3 is provided in the exhaust pipe 5, and the temperature adjustment unit 2b is covered with the bypass pipe 6. . This embodiment differs from the first embodiment in that the temperature control section 2b is covered with a bypass pipe 6 instead of the exhaust pipe 5, and the other points are the same. The working fluid W passing through the temperature adjusting portion 2b exchanges heat with the exhaust gas G flowing through the bypass pipe 6 covering the temperature adjusting portion 2b. The exhaust gas G flowing through the bypass pipe 6 corresponds to part of the exhaust gas G flowing through the exhaust pipe 5 upstream of the evaporator 3 . The range of the temperature adjustment part 2b in the pipe 2a between the outlet of the evaporator 3 and the inlet of the expander 4 is the temperature of the working fluid W passing through the outlet of the evaporator 3. is set above the temperature of

In the Rankine cycle system 1 of the first and second embodiments, the working fluid W exchanges heat with the exhaust gas G in the evaporator 3, so that most of it is heated and evaporated. The working fluid W that exchanges heat with the exhaust gas G and flows out from the outlet of the evaporator 3 exchanges heat with the exhaust gas G passing through the exhaust pipe 5 (or the bypass pipe 6) on the upstream side of the evaporator 3, and is heated. It flows into the inlet of the expander 4 . The working fluid W flowing into the expander 4 expands and outputs power to its output shaft 4a.

According to the Rankine cycle system 1 of the present embodiment (first and second embodiments), the temperature adjustment portion 2b that is at least part of the working fluid pipe 2a between the outlet of the evaporator 3 and the inlet of the expander 4 , the exhaust gas G flowing through the exhaust pipe 5 upstream of the evaporator 3 (or the exhaust gas G flowing through the bypass pipe 6 which is a part of the exhaust gas G) and the working fluid W are heat-exchanged. As a result, the working fluid W after passing through the evaporator 3 can be heat-exchanged with the exhaust gas G flowing through the exhaust pipe 5 upstream of the evaporator 3, and the temperature can be further increased, so that the power that can be output by the expander 4 can be suppressed. Moreover, by further raising the temperature of the working fluid W in the temperature adjustment part 2b, the evaporation of the working fluid W that has not been evaporated in the evaporator 3 can be promoted.

This configuration does not keep the temperature of the working fluid W unlike the configuration in which the piping 2a for the working fluid between the outlet of the evaporator 3 and the inlet of the expander 4 is covered with a heat insulating material to shut off the outside air. The temperature of the working fluid W is further increased. Therefore, the power that can be output from the expander 4 is relatively large.

In this configuration, the working fluid pipe 2a between the outlet of the evaporator 3 and the inlet of the expander 4 is covered with a heating device such as a heater, and the pipe 2a is heated while controlling the heating amount of the heating device. Unlike , it does not require control and has a simple configuration.

When the temperature control unit 2b is covered with the exhaust pipe 5 upstream of the evaporator 3 as in the first embodiment, the installation space for the bypass pipe 6 is not required as compared with the second embodiment, which saves space. be. When the temperature adjustment unit 2b is covered with the bypass pipe 6 as in the second embodiment, the bypass pipe 6 is newly provided compared to the first embodiment, so the range of the temperature adjustment unit 2b covered with the bypass pipe 6 can be increased relatively easily.

It is preferable to improve the heat exchange performance between the working fluid W and the exhaust gas G by providing fins on the inner wall surface or the outer wall surface of the temperature control part 2b.

When a plurality of fins are arranged on the inner wall surface (outer wall surface) of the temperature control unit 2b, these fins may be arranged in the direction of flow of the working fluid W (exhaust gas G), or these fins may be arranged in the direction of the flow of the working fluid W (exhaust gas G). You may arrange|position with respect to the same cross section of the adjustment part 2b. Alternatively, these fin arrangements may be combined.

The arrangement of the fins described above may be combined with the inner wall surface or the outer wall surface of the temperature control section 2b. Further, when a plurality of fins are arranged in the direction of flow of the exhaust gas G, the surface area of the fins on the downstream side may be larger than the surface area of the fins on the upstream side.

Moreover, the cross-sectional shape of the temperature control part 2b is set to a shape (for example, petal shape) having a larger surface area than the cross-sectional shape (for example, circular shape) of a normal pipe. According to this configuration, a relatively large amount of heat of the exhaust gas G is transferred to the working fluid W through the wall surface of the temperature adjustment part 2b, so the heat exchange performance between the working fluid W and the exhaust gas G can be improved.

As in the first embodiment, when the temperature control unit 2b is composed of the pipe 2ba extending in the passage direction of the exhaust gas G and the pipe 2bb extending in the radial direction of the exhaust gas G, the surface area of the wall surface of the pipe 2ba is It is preferable to make the structure larger than the surface area of the wall surface of the pipe 2bb. For example, it is preferable that the length of the pipe 2ba is longer than the length of the pipe 2bb, or that the pipe 2ba is bent at least once (folded shape, spiral shape, etc.).

By configuring in this way, heat exchange between the exhaust gas G passing through the central portion of the pipe and the working fluid W, which has a higher temperature than the exhaust gas G passing through the outer peripheral portion of the pipe, is promoted, so that the working fluid W rises. Can promote warmth.

1 Rankine cycle system 2 Flow path (piping) for working fluid
2a Piping for working fluid between outlet of evaporator and inlet of expander 2b Temperature control section 3 Evaporator 4 Expander 4a Output shaft of expander 5 Exhaust pipe 6 Bypass pipe

Claims (1)

Rankine comprising: an evaporator for exchanging heat between a working fluid and exhaust gas passing through an exhaust pipe of an internal combustion engine; and an expander for expanding the working fluid heat-exchanged with the exhaust gas by the evaporator to output power. In the cycle system,
A temperature adjustment part, which is at least a part between an outlet of the evaporator and an inlet of the expander in the working fluid pipe through which the working fluid passes , is arranged upstream of the evaporator to control heat in the evaporator. It is covered with a bypass pipe that bypasses the evaporator by branching from the main exhaust pipe through which the exhaust gas used for replacement passes and joining the main exhaust pipe downstream of the evaporator, A Rankine cycle having a configuration in which the temperature of the working fluid passing through the inlet of the expander exceeds the temperature of the working fluid passing through the outlet of the evaporator by exchanging heat between the exhaust gas flowing through the bypass pipe and the working fluid. system.

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