A Stirling engine that uses four cylinders to complete one cycle.

Abstract

Conventional Stirling engines have the following drawbacks: • The two working gases that exchange heat with each other do not reach the heat exchanger at the same time. The pressure, volume, temperature, and entropy of the working gas change continuously. [Solution] A combination of a cylinder and a piston creates a first heating chamber, a second heating chamber, a first cooling chamber, and a second cooling chamber. The first heating chamber and the second cooling chamber are small for the same volume. The second heating chamber and the first cooling chamber are large for the same volume. Each cylinder is connected by a vent pipe with a check valve. The vent pipes connecting the second heating chamber and the first cooling chamber, and the vent pipes connecting the third cooling chamber and the first heating chamber, are passed through the heat exchanger. The pistons and crankshafts are connected such that when the volumes of the first heating chamber and the first cooling chamber are at their minimum, the volumes of the second heating chamber and the second cooling chamber are maximized. The first and second heating chambers are heated with a high-temperature heat source, and the first and second cooling chambers are cooled with a low-temperature heat source.

Description

Technical Field

[0001] The present invention relates to a Stirling engine of an external combustion engine.

Background Art

[0002] As forms of Stirling engines, an α-type, a β-type, a γ-type, a double-acting type, etc. have been proposed (Non-Patent Documents 1, 2, 3). Also, a form using a check valve has been proposed (Non-Patent Document 4).

Prior Art Documents

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0003] The drawbacks of the conventionally proposed Stirling engines are as follows. • The two working gases exchanging heat with each other do not reach the heat exchanger at the same time. As a result, the shape of the heat gradient formed by one working fluid in the heat exchanger collapses within the time it takes for the other working fluid to pass through the heat exchanger. Consequently, the heat exchange efficiency of the heat exchanger is poor. The pressure, volume, temperature, and entropy of the working gas change continuously. Therefore, the time spent in each process—isocholic heating, isothermal heating, isochoric cooling, and isothermal cooling—is very short. As a result, the thermal cycle deviates from the Stirling cycle, leading to poor thermal efficiency. [Means for solving the problem]

[0004] The structure of the present invention is as follows. Four combinations of cylinders and pistons are prepared. The enclosed spaces formed by each combination are designated as the first heating chamber, the second heating chamber, the first cooling chamber, and the second cooling chamber. The first heating chamber and the second cooling chamber are small for the same volume. The second heating chamber and the first cooling chamber are large for the same volume. Each cylinder is connected by a vent pipe with a check valve. The ventilation direction is first heating chamber → second heating chamber → first cooling chamber → second cooling chamber → first heating chamber. The vent pipes connecting the second heating chamber and the first cooling chamber, and the vent pipes connecting the third cooling chamber and the first heating chamber, are passed through a heat exchanger to allow heat exchange between them. Each piston is connected to the crankshaft by a connecting rod. The connection between each piston and the crankshaft is such that when the volume of the first heating chamber and the first cooling chamber is at its minimum, the volume of the second heating chamber and the second cooling chamber is at its maximum. If there are multiple crankshafts, each crankshaft should rotate at the same speed. The first heating chamber and the second heating chamber are heated with a high-temperature heat source. The first and second cooling chambers are cooled using a low-temperature heat source. [Effects of the Invention]

[0005] It can achieve higher thermal efficiency than existing Stirling engines. The reasons are as follows: Two masses of working gas pass through the heat exchanger simultaneously. • It is closer to the Stirling cycle than the thermal cycles of conventionally proposed Stirling engines. [Brief explanation of the drawing]

[0006] [Figure 1] The proposed structure (single-acting) An example of the proposed structure implemented as a single-acting system is shown. The working fluid consists of two masses. The diagram shown is a cross-sectional view. The crankshaft rotates perpendicular to the plane of the paper. [Figure 2] Proposed Structure (Double-Acting) An example of the proposed structure implemented in a double-acting configuration is shown. In this example, the isochoric heating and cooling are closer to the Stirling cycle than in the single-acting configuration shown in Figure 1. There are four working fluid masses. The diagrams shown are cross-sectional views. The crankshaft rotates perpendicular to the plane of the paper.

[0007] [Figure 3] Operation of this proposal (single-acting): An example of the proposed operation implemented using a single-acting mechanism is shown. [Figure 4]Operation of the Proposed Method (Double-Acting) An example of the operation of the proposed method implemented in a double-acting manner is shown below. The state numbers in Figures 3 and 4 represent the state of the working gas inside the adjacent cylinder and heat exchanger. The state changes of the working gas are as follows (common to Figures 3 and 4): State 1 → State 2: Moves from the second cooling chamber to the first heating chamber. Receives heat from the heat exchanger. Volume does not change much. Nearly isovolumetric heating. State 2 → State 3: Moves from the first heating chamber to the second heating chamber. Receives heat from the high-temperature heat source. Temperature does not change much. Nearly isovolumetric heating. State 3 → State 4: Moves from the second heating chamber to the first cooling chamber. Disposes heat to the heat exchanger. Volume does not change much. Nearly isovolumetric cooling. State 4 → State 1: Moves from the first cooling chamber to the second cooling chamber. Disposes heat to the low-temperature heat source. Temperature does not change much. Nearly isovolumetric cooling. The relationship between the crankshaft rotation angle and the cycles in this proposal is as follows (common to Figures 3 and 4): One mass of working fluid experiences one Stirling cycle (1 / 4 cycle) in the time it takes for the crankshaft to rotate 180°. In other words, one mass of working fluid experiences four Stirling cycles (1 cycle) in the time it takes for the crankshaft to rotate 2 times.

[0008] [Figure 5] Relationship between the proposed state numbers and the Carnot cycle The Carnot cycle is represented by a pv diagram and an sT diagram, and the state numbers shown in

[0007] above are superimposed on them. [Modes for carrying out the invention]

[0009] By exposing the crankshaft to an environment with temperature differences and connecting a generator to it, electricity can be generated. [Examples]

[0010] none [Industrial applicability]

[0011] · It can be used for energy harvesting from a small temperature difference. Small temperature differences exist in large numbers in the surrounding environment (geothermal heat, sewer pipes, bath drainage in each household, greenhouses, etc.). · It can be used for power generation in places where the use of the grid power is not available, power generation during disasters, etc.

Description of symbols

[0012] · Description of components · 1-1, 1-2, 1-3, 1-4: Cylinders · 2-1, 2-2, 2-3, 2-4: Pistons · 3-1, 3-2, 3-3, 3-4: Connecting rods · 4-1, 4-2, 4-3, 4-4: Crankshafts The rotating shafts are rotating at a common speed. If possible, connect them to one shaft. · 5: Vent pipe with a check valve function · 6: Heat exchanger · 1-1 and 2-1: Constituting the first heating chamber · 1-2 and 2-2: Constituting the second heating chamber · 1-3 and 2-3: Constituting the first cooling chamber · 1-4 and 2-4: Constituting the second cooling chamber · Description of state numbers · State 1: The state after the end of isothermal cooling and before the start of isochoric heating · State 2: The state after the end of isochoric heating and before the start of isothermal heating · State 3: The state after the end of isothermal heating and before the start of isochoric cooling · State 4: The state after the end of isochoric cooling and before the start of isothermal cooling

Claims

[Claim 1] A structure that satisfies all of the following conditions. Four combinations of cylinders and pistons are prepared. The enclosed spaces formed by each combination are designated as the first heating chamber, the second heating chamber, the first cooling chamber, and the second cooling chamber. The first heating chamber and the second cooling chamber are small for the same volume. The second heating chamber and the first cooling chamber are large for the same volume. Each cylinder is connected by a vent pipe with a check valve. The ventilation direction is first heating chamber → second heating chamber → first cooling chamber → second cooling chamber → first heating chamber. - The vent pipes connecting the second heating chamber and the first cooling chamber, and the vent pipes connecting the third cooling chamber and the first heating chamber, are passed through a heat exchanger to allow heat exchange between them. Each piston is connected to the crankshaft by a connecting rod. The connection between each piston and the crankshaft is such that when the volume of the first heating chamber and the first cooling chamber is at its minimum, the volume of the second heating chamber and the second cooling chamber is at its maximum. If there are multiple crankshafts, rotate each crankshaft at the same speed. The first and second heating chambers are heated with a high-temperature heat source. - The first and second cooling chambers are cooled using a low-temperature heat source.

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