JPH0776543B2 - Stirling engine - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to Stirling engines.

Structure of Conventional Example and Its Problems FIG. 1 shows one of the conventional examples of the Stirling engine. Here, the reciprocating motion of the displacer 1 causes the working fluid in the cylinder 2 to pass through the working fluid flow path 3, the cooler 4, the regenerator 5, and the heater 6 to expand the expansion space 7 and the compression space 8. Make a round trip. At this time, in the process of raising the displacer 1, the working fluid moves from the expansion space 7 through the regenerator 5 and the cooler 4 to the compression space 8 and is cooled by the regenerator 5 and the cooler 4. The pressure above the power piston 9 decreases. Further, in the process of lowering the displacer 1, the working fluid is heated while moving from the compression space 8 through the regenerator 5 and the heater 6 to the expansion space 7, so that the pressure above the power piston 9 increases. Therefore, due to the pressure fluctuation of the working fluid caused by the reciprocating movement of the displacer 1, the power piston 9
Will reciprocate. In this embodiment, the power piston 9 is reciprocated by the crank mechanism 10 with a phase delay of about 90 degrees from the displacer 1.

Here, as described above, since the Stirling engine is basically an external combustion engine, it goes without saying that the temperature difference between the working fluid in the heater 6 and the cooler 4 and the external heat source has an important influence on its performance. . Generally, as a method of reducing the temperature difference between them, there is an increase in the heat exchange area, an increase in the working fluid filling pressure, an increase in the rotation speed, and the like. However, an increase in the heat exchange area leads to an increase in dead space in the engine, which eventually reduces its performance. Furthermore, the increase of the working fluid filling pressure and the increase of the rotation speed cause the pressure resistance of the material,
Due to problems such as increase in pressure loss and mechanical loss in the flow path, these naturally have limitations, and it was difficult to reduce the temperature difference further. Also, as is clear from the pv characteristic diagram of the Stirling engine of FIG. 2, the internal pressure change is slower than that of other internal combustion engines, which is the reason why the output per unit volume is small. Was becoming. The reason why this large pressure change is difficult to take is that the heat transfer in the heater 6 and the cooler 4 is small and the high temperature expansion space 7
Since the low temperature compression space 8 is always communicated with the working fluid flow path 3 via the regenerator 5, the pressure in the cylinder above the power piston is always averaged.

OBJECT OF THE INVENTION The present invention is directed to improving the output and efficiency of a Stirling engine.

To achieve the above object, in the present invention, a working fluid flow path switch that opens and closes a working fluid flow path that moves between an expansion space and a compression space in an engine by reciprocating in a cylinder is provided. The heat is exchanged between the working fluid and the heat source.

Description of Embodiments FIG. 3 shows an embodiment of the Stirling engine of the present invention. In FIG. 3, the same components as those in FIG. 1 are designated by the same reference numerals. A cylindrical working fluid flow path switch 11 having an outer diameter equal to that of the displacer 1 is attached to the bottom surface of the displacer 1 on the compression space 8 side integrally with the displacer 1, and the power piston 9 is attached to the inner surface thereof. It has a reciprocating structure. Further, the working fluid passage switch 11 is provided with a plurality of working fluid passage holes 12, and the compression space 8 surrounded by the inner wall of the working fluid passage switch 11 and the power piston 9, the cooler 4, and the regenerator. 5. The compression space 8 side outlet of the working fluid flow path 3 connecting the heater 6 and the expansion space 7 is opened when the displacer 1 is located near its top dead center and bottom dead center, and is closed near the center of the amplitude. It is composed. Next, the position changes of the displacer 1 and the power piston 9 with respect to time and the opening / closing timing of the working fluid passage hole 12 of the working fluid passage switch 11 at this time are shown in FIG. 4 with the horizontal axis as the time axis. . Here, the phase difference between the displacer 1 and the power piston 9 is about 90 degrees, and the sections A and C are the states in which the working fluid passage 3 is open near the top dead center and the bottom dead center of the displacer 1, On the contrary, in sections B and D, it closes, and the expansion space 7 and the compression space 8
Is a state in which the working fluid does not move between and.

Next, this operation will be described. In this figure, first, the working fluid channel 3 is opened in the section A, and the displacer 1 is near the top dead center, and most of the working fluid is moving to the compression space 8. Therefore, expansion space 7 and compression space 8
The speed of the working fluid flowing between the two is almost 0, and therefore there is almost no pressure difference between the expansion space 7 and the compression space 8. In addition, most of the working fluid is in the space on the low temperature side, so the compression space pressure is low. Shows the lowest pressure in one cycle in the figure.
When the displacer 1 starts descending after passing through the top dead center from the section A and enters the section B, the working fluid flow path 3 is closed, so that a pressure difference starts to occur between the expansion space 7 and the compression space 8. That is, the expansion space 7 is adiabatically expanded by the displacer 1 being lowered, and as a result, the pressure in the section A is gradually decreased, and the compression space 8 is adiabatically compressed by the relative movement of the displacer 1 and the power piston. Then, the pressure rises, and the pressure difference continues to rise to a position where the volume of the compression space 8 becomes the minimum just before the working fluid passage 3 is opened after the section B ends. Next, when the working fluid passage 3 is opened in the section C, the working fluid rapidly flows from the compression space 8 into the expansion space 7 due to this pressure difference and the lowering of the displacer 1. At this time, since the working fluid flows at a high flow rate, the heat transfer coefficient in the regenerator and the heater can be increased, and most of the working fluid moves to the expansion space, so that the pressures in the expansion space 7 and the compression space 8 rapidly. To rise. As a result, the pressure in the compression space 8 reaches the highest pressure in one cycle in the figure. Next, when the working fluid flow path 3 is closed in the section D, a pressure difference starts again in the expansion space 7 and the compression space 8. That is, the pressure of the expansion space 7 rises as the displacer 1 rises, and the compression space 8 is decompressed by the relative movement of the displacer 1 and the power piston 9. Then, when entering the section A and opening the working fluid channel 3, the working fluid rapidly flows from the expansion space 7 into the compression space 8 due to this pressure difference and the rise of the displacer 1. Also in this case, the heat exchange efficiency is promoted by the flow velocity, and most of the working fluid moves to the compression space 8. Therefore, the regenerator 5 and the cooler 4 cool and decompress the pressure, and the pressure in the compression space 8 drops sharply. The lowest pressure.

The present embodiment is merely an example of the present invention, and (i) the working fluid flow path switch is cylindrical, (ii) the working fluid flow path switch is arranged separately from the displacer, (iii) ) A configuration such as applying to a free piston type Stirling engine is also conceivable.

Effects of the Invention As is apparent from the above description, the present invention has the following effects.

(1) The working fluid is caused to flow intermittently and at a high flow rate to the heater, regenerator, and cooler, thereby increasing the heat transfer coefficient there and improving engine efficiency.

(2) Since the working fluid is heated and cooled only in a specific section in one cycle, a rapid increase or decrease in pressure can be obtained, and as a result, the output per unit volume can be increased.

(3) Due to the effect of the rise (1), the heat exchange area can be reduced, the engine can be downsized, and the dead space in the engine can be reduced to improve the performance.

(4) The effect of the above (2) can realize downsizing of the engine.

[Brief description of drawings]

FIG. 1 is a sectional view of a conventional Stirling engine, and FIG.
FIG. 3 is a pv characteristic diagram of the same Stirling engine, FIG. 3 is a sectional view of a Stirling engine showing an embodiment of the present invention, and FIG. 4 is a position of a power piston and a displacer, and a compression space and an expansion space. It is the figure which showed the change with respect to a time axis. 1 ... Displacer, 3 ... Working fluid flow path, 4 ...
Cooler, 5 ... Regenerator, 6 ... Heater, 7 ... Expansion space, 8 ... Compression space, 9 ... Power piston, 11 ... Working fluid passage switch, 12 ... Working fluid passage hole .

Claims (1)

[Claims] 1. A closed vessel in which a working fluid is sealed, a means for heating the working fluid, a means for cooling the working fluid, a member to be worked from the working fluid, and a high temperature in the closed vessel. The displacer includes a flow path switch that opens and closes a flow path of the working fluid that moves between the side space and the low temperature side space, a working fluid passage hole provided in the flow path switch, and a member that moves the working fluid. A Stirling engine in which the working fluid flow passage is opened when is located before and after its top dead center and bottom dead center, and is closed when the displacer is located around the middle position of its amplitude.