JP2005002976A - Hot air type external-combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hot air type external-combustion engine having a low environmental load using a method having a high practicality. <P>SOLUTION: A heater 3 and a cooler 4 are connected parallel between a compression side cylinder 1 and an expansion side cylinder 2, and in the heating process, the passage including the heater 3 is selected by a shutoff/selector valve 5, and heating is conducted while the fluid is moved from the compression side cylinder 1 to the expansion side cylinder 2. In the cooling process, the passage including the cooler 4 is selected, and cooling is conducted while the fluid is moved from the expansion side cylinder 2 to the compression side cylinder 1. In the adiabatic process, the two cylinders are separated from the passages, and a adiabatic change takes place inside the cylinders. The heating and cooling processes are made in the form of isobaric change by driving pistons in the cylinders according to the cam curve, and the conditional change can be made in Brayton cycles. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[Conventional technology and problems]
In recent years, due to increased awareness of the global environment, external combustion engines with low noise and low pollutants in the exhaust gas are attracting attention, regardless of heat source. Stirling engines are being developed as representatives of these external combustion engines. . A Stirling engine can make full use of the temperature ratio of the working fluid regardless of the cylinder volume change ratio and can always achieve the highest thermal efficiency, but has the following drawbacks.
As shown in FIG. 7, the Stirling engine uses a regenerator (heat accumulator) to bring it closer to the Carnot cycle. However, the efficiency of the regenerator is not perfect, so that heat escapes from the high temperature side to the low temperature side.
・ Regenerator becomes resistance when moving working fluid.
・ It is difficult to construct a structure that keeps the entire cylinder at a constant temperature, and it is difficult to efficiently transfer heat to the working fluid.
-Due to the dead volume, the temperature change of the entire working fluid is averaged, the temperature ratio is degenerated and the thermal efficiency is lowered.
FIG. 8A shows a TS diagram of the Carnot cycle, and FIG. 8B shows a TS diagram of the Stirling cycle. The maximum temperature and the minimum temperature of the working fluid in the Stirling cycle are Th and Tc as in the Carnot cycle. However, when the cycle trajectory is curved, the representative value of the high temperature decreases to Th (s), and the low temperature decreases to Tc ( s), and the thermal efficiency of the Stirling cycle increases only to about 0.8 times the thermal efficiency (Th−Tc) / Th shown in the Carnot cycle.
Thus, since a Stirling engine is difficult to make in practice and it is difficult to increase thermal efficiency, it is necessary to develop a highly feasible external combustion engine.
[0002]
[Configuration and operation of the present invention]
The configuration of the present invention is shown in FIG.
In the present invention, the compression side cylinder 1 and the expansion side cylinder 2 are connected by two flow paths, a flow path including a heater 3 and a flow path including a cooler 4, and both cylinders are connected by a shutoff / switching valve 5. The inside is filled with working fluid so that one of the flow paths is connected or both flow paths are disconnected.
The operation of the present invention is shown in FIG. 2 (a), and its TS diagram is shown in FIG. 2 (b).
First, the compression-side cylinder 1 and both flow paths are disconnected, and the piston is moved to perform adiabatic compression. At this time, the temperature of the working fluid becomes Tha.
Next, the flow path including the compression side cylinder 1, the expansion side cylinder 2 and the heater 3 is connected, and the piston is moved to move the working fluid from the compression side cylinder 1 to the expansion side cylinder 2 and to perform heating. The temperature after heating is Thb, and by moving the volume ratio of the compression side cylinder 1 and the expansion side cylinder 2 to Tha: Thb, the moving heating of the working fluid becomes equal pressure expansion. The entropy change ΔS is proportional to ln (Thb / Tha), but since the temperature ratio in this isobaric expansion is small, it is shown as a straight line in the TS diagram.
Furthermore, the expansion side cylinder 2 and both flow paths are separated, and the piston is moved to perform adiabatic expansion. At this time, the temperature of the working fluid becomes Tcb.
Finally, the flow path including the compression side cylinder 1, the expansion side cylinder 2 and the cooler 4 is connected, and the piston is moved to move the working fluid from the expansion side cylinder 2 to the compression side cylinder 1 and to cool. The state change at this time is equal pressure compression.
[0003]
As a specific example of the present invention, temperature and volume change ratios are set, and a TS diagram is shown in FIG.
Considering the influence on the environment, the maximum temperature of the working fluid is set to 1600 ° K so that the generation of nitrogen oxides (NOx) is reduced, and the combustion temperature is also in accordance with it.
The thermal efficiency is represented by b / (a + b). In this example, 1000 ÷ 1400 = 0.714, and Th = 1600 ° K, Tc = 400 ° K, when the Carnot cycle thermal efficiency is 0.75. The value is very close to 0.95 times.
In this example, the volume change ratio when the isobaric change is the same as the temperature ratio is 1600 ÷ 1400 = 1.14 times. When helium (He) is used as the working fluid, the temperature ratio when the adiabatic change is 1400 ÷ 400 = Since it is 3.5 times, the volume change ratio is 6.5 times, the pressure ratio is 22.8 times, and the PV diagram is as shown in FIG.
Fig. 4 shows changes in the temperature and output of the working fluid during acceleration.
In the present invention, the speed and output are adjusted by the accelerator as in the conventional reciprocating engine.
In normal operation, combustion is performed at a combustion temperature with an air-fuel ratio suitable for adiabatic and isobaric change ratios, and the maximum temperature of the working fluid is also appropriate.
When the fuel is increased by applying the accelerator and the combustion temperature rises, the volume change ratio is constant and the thermal efficiency does not change, but the output per rotation increases and acceleration is performed.
By returning the accelerator, the output per rotation returns to the steady state, but the work rate increases because the rotation speed increases.
[0004]
FIG. 5 shows the configuration of the embodiment of the present invention.
As shown in FIG. 5 (a), the compression side cylinder 1, the expansion side cylinder 2, the heater 3, the cooler 4 and the shutoff / switching valve 5 which are the basic configuration of the present invention are collectively made into one unit. As shown in FIG. 5B, it is arranged so as to surround the axis of the cylindrical cam, and the cylindrical cam is provided with a groove for driving the piston or the like. By placing the unit opposite to the cam, the vibration is canceled and the stress applied to the cam shaft is minimized.
The heater 3 and the cooler 4 are counter-current heat exchangers, and are provided with a shutter driven by a cam so that the combustion gas is supplied to the heater 3 only during fluid heating of the fluid.
FIG. 6 shows a development view of the cam curve.
The piston moves so that the volumes of the compression side cylinder 1 and the expansion side cylinder 2 change corresponding to each step.
By operating the shut-off / switching valve 5, both cylinders are connected to the flow path including the heater 3 during moving heating, connected to the flow path including the cooler 4 during moving cooling, and the shut-off / switching valve 5 is neutral during adiabatic change. And separated from either flow path.
The shutter is opened only during moving heating, but is opened prior to moving heating in consideration of the time for heating the heater 3 itself.
In addition, the cam curve can be appropriately designed according to the time required for heating and cooling at a constant rotational speed.
[0005]
[Effect of the present invention]
In the present invention, since the temperature ratio at the time of adiabatic change or isobaric change is fixed, when the temperature of the heat source is removed from the optimum temperature, the maximum thermal efficiency at that temperature cannot be realized, and wasteful heat is released into the exhaust. However, the exhaust heat can be regenerated by the intake air as in the conventional turbine engine, and waste can be minimized.
The features of the present invention are as follows.
-By accurately reproducing each state change, thermal efficiency close to the theoretical value of Carnot cycle can be realized. The behavior is easy to grasp and understand.
-No regenerator is required, there is no problem of heat removal, and the resistance of the working fluid is reduced.
・ Since the moving heating is an isobaric change, the pressure in the cylinder and in the flow path are equal, and there is no sound of fluid jetting when the valve is opened, resulting in high silence.
In the adiabatic change process, since the cylinder is completely separated from the flow path, the adiabatic change is surely performed in the cylinder, and the flow path does not become dead volume. Therefore, the allowable range of the length and volume of the flow path is wide, and the flexibility of the layout of the heater and cooler is high.
-Since there is no need to heat and cool the cylinder and the heat exchanger does not become dead volume, the selection range of the heat exchanger structure is expanded, and a highly efficient heat exchanger can be used.
As described above, according to the present invention, it is possible to make an external combustion engine with high thermal efficiency and high feasibility.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of the present invention.
FIG. 2 is an operation diagram of the present invention.
FIG. 3 is a specific example of a state change of the present invention.
FIG. 4 is a comparison diagram of state changes of the present invention.
FIG. 5 is a configuration diagram of an embodiment of the present invention.
FIG. 6 is a configuration diagram of an embodiment of the present invention.
FIG. 7 is a configuration diagram of a conventional method.
FIG. 8 is a state change diagram of a conventional method.
[Explanation of symbols]
1. 1. Compression side cylinder 2. Expansion side cylinder Heater 4. 4. Cooler Shut-off / switching valve

Claims (3)

In an external combustion engine that heats and cools a sealed fluid from the outside and converts it into a force, a heater 3 and a cooler 4 are connected in parallel between the compression side cylinder 1 and the expansion side cylinder 2, and each cylinder and the heater 3. The flow path between the cooler 4 and the cooler 4 is changed by a flow path shut-off / switch valve 5 to change the flow path during heating and cooling, heating or cooling is performed when the fluid is moved, and adiabatic change is performed in each cylinder. An external combustion engine. An external combustion engine in the range 1 in which the piston in the compression side cylinder 1 and the expansion side cylinder 2 is driven by the cam curve to realize the Brayton cycle. The external combustion engine of the range 1 which has a shutter which controls combustion gas so that heat may be supplied to the heater 3 only when fluid heating is performed.

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