JP2538909B2 - Stirling engine heater - Google Patents

Description

The present invention relates to a heater for heating a working fluid in a Stirling engine, and more particularly to a heater using a combustion system.

(Prior Art) Recently, the Stirling engine has attracted attention as a part of energy saving. There are various types of Stirling engines, but for example, in the case of a two-piston type, a regenerator is connected between the expansion cylinder and the compression cylinder, and the regenerator and the expansion cylinder operate in the flow path. The fluid is heated and the working fluid is cooled in the flow path between the regenerator and the compression cylinder. This engine has high theoretical thermal efficiency and can use any heat source.

By the way, a heater for a working fluid in a Stirling engine is usually composed mainly of a combustion chamber that forms a combustion flame by a gas or liquid fuel, and a heat exchanger that transfers heat to the working fluid by radiation and convection in the combustion chamber. It

In such a Stirling engine heater, the high temperature gas generated in the combustion chamber maintains a high temperature of about 700 to 800 ° C. even after heating the working fluid. For this reason, in a Stirling engine heater, an air preheater is generally arranged to perform heat exchange between the combustion air and the combustion exhaust gas for the purpose of recovering exhaust heat of the high temperature gas after heating. The efficiency is improved by preheating the air before supplying it to the combustion chamber.

However, there is a problem that preheating of combustion air is accompanied by emission of nitrogen oxide (NOx) which is a causative substance of photochemical smog. Moreover, the amount of NOx produced greatly depends on temperature, and increases exponentially with increasing preheating temperature.

As one method for reducing NOx, an exhaust gas recirculation system is known in which combustion exhaust gas is mixed into combustion air. An ejector is a means for specifically realizing this method. The ejector ejects air as a driving flow from a nozzle to generate a negative pressure in the mixing chamber, and the negative pressure causes the combustion exhaust gas to be drawn in and mixed with the combustion air. However, since the temperature of the combustion exhaust gas introduced into the mixing chamber of the ejector is about 200 to 300 ° C,
When mixed with air, condensation occurs, resulting in the accumulation of condensed water in the mixing chamber within the ejector.

When the condensed water accumulates in the mixing chamber, the air flow is obstructed and the flow velocity decreases, so the pressure difference from the combustion exhaust gas decreases, and the suction of the combustion exhaust gas due to negative pressure cannot be performed properly. That is, the efficiency of the ejector decreases. Further, when the condensed water accumulated in the mixing chamber reaches the combustion chamber, the temperature of the combustion gas becomes low, and the heat exchange efficiency of the heat exchanger provided in the combustion chamber decreases.

(Problems to be solved by the invention) When the conventional ejector is used for exhaust gas recirculation in the heater of the Stirling engine as described above, condensed water is accumulated in the mixing chamber in the ejector, which lowers the efficiency of the ejector. However, there is a problem that condensed water enters the combustion chamber and heat exchange efficiency decreases.

The present invention has been made to solve such a problem, and effectively discharges the condensed water generated in the ejector to improve the efficiency of the ejector and the heat exchange efficiency of the heat exchanger in the combustion chamber. An object of the present invention is to provide a heater for a Stirling engine that can be designed.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention connects a drain pipe for discharging condensed water to the lower part of the mixing chamber of an ejector, and connects the drain pipe in the middle thereof. It is characterized in that a solenoid valve is inserted, and further below that, a check valve that is closed when the solenoid valve is opened is inserted.

(Operation) When the solenoid valve is normally open, the check valve is closed due to the negative pressure, and the condensed water generated in the mixing chamber of the ejector is accumulated in the drain pipe above the check valve. When the solenoid valve is closed, the check valve is opened, so that the condensed water accumulated in the drainage pipe is discharged to the outside.

In this way, the condensed water in the mixing chamber can be discharged while maintaining the negative pressure in the mixing chamber in the ejector. Therefore, the problem of lowering the efficiency of the ejector due to the accumulation of condensed water in the mixing chamber is solved, and the infiltration of condensed water into the combustion chamber is prevented.

(Example) Hereinafter, the Example of this invention is described with reference to drawings. FIG. 1 is a sectional view showing a schematic structure of a Stirling engine incorporating an air preheater according to an embodiment of the present invention.

As shown in FIG. 1, this Stirling engine has a power cylinder (expansion cylinder) 1 for expanding a working fluid, a power piston (expansion piston) 2 slidably mounted in the expansion cylinder 1, and a working fluid. A heating device 5, a regenerator 6, and a cooling device 7 are arranged between a cylinder (compression cylinder) 3 for compressing and a piston (compression piston) 4 slidably mounted in the compression cylinder 3. Further, the expansion piston 2 and the compression piston 4 are connected to the connecting rods 8 and 9 and the crankshaft 10, respectively.
It is a two-piston Stirling engine with a structure in which an output shaft 12 is connected via 11.

The heater 5 includes a combustion chamber 15 arranged via an inner heat insulating material 14 so as to surround the head 13 of the expansion cylinder 1, a plurality of heat exchangers 16 arranged in the combustion chamber 15, and a combustion chamber 15. Composed mainly of a combustion air generating means including an air preheater 18 which is arranged so as to face the gas nozzle 17 and surrounds the combustion chamber 15 and preheats combustion air by heat exchange with combustion exhaust gas, and an ejector described later. Has been done. The heat exchangers 16 are arranged in a funnel shape as a whole, and one end side of the fluid passage formed inside each is at the top of the expansion cylinder 1 and the other end side is provided with a manifold 19 and a connecting pipe 20 formed inside the head 13. And communicates with the regenerator 6, respectively.
Then, a blank surrounded by the expansion cylinder 1 and the expansion piston 2, a heat exchanger 16, a manifold 19, a connecting pipe 20, a regenerator 6, a cooler 7, and a compression cylinder 3 and a compression piston 4. A working fluid such as He is enclosed in the space.

In FIG. 1, 21 is a crank chamber in which lubricating oil is stored to a predetermined level, 22 and 23 are linear bearings, and 24 and 25 are linear bearings.
Is a pipe for guiding the refrigerant of the cooler 7, 26 to 28 are heat insulating materials, 29
Are swirlers for swirling and supplying combustion air mixed with combustion exhaust gas into the combustion chamber 15 by an ejector 30 described later.

The ejector 30 is a nozzle 31 that ejects air from the tip,
The mixing chamber 32 for mixing the air and the combustion exhaust gas is mainly configured, and the mixing chamber 32 includes the exhaust duct from the combustion chamber 15.
A part of the combustion exhaust gas discharged to 33 is guided through the exhaust gas passage 34. The mixed gas of air and combustion exhaust gas generated in the mixing chamber 32 is supplied to the air preheater 18 via the air passage 35 and the air supply port 36.

On the other hand, a drain pipe 37 for discharging condensed water is connected to the lower part of the mixing chamber 32. An electromagnetic valve 38 whose opening and closing is controlled by a controller (not shown) is inserted in the middle of the drain pipe 37, and a check valve 39 is inserted below the electromagnetic valve 38. The check valve 39 is provided so as to be closed when the solenoid valve 38 is open and open when the solenoid valve 38 is closed.

Next, the operation of the Stirling engine of this embodiment will be described. Combustion flame is formed by injecting gas fuel from the gas nozzle 17 into the combustion chamber 15 and supplying the combustion air generated by the ejector 30 from the swirler 29 through the air preheater 18, and further the refrigerant by the pipes 24, 25. When the output shaft 12 is temporarily rotated by an external power source while circulating, the expansion piston 2 and the compression piston 4 reciprocate with a certain phase difference via the crankshafts 10 and 11 and the connecting rods 8 and 9. Move. When the expansion piston 2 moves to the compression stroke by this reciprocating motion, the working fluid (He) in the expansion cylinder 1 passes through the heat exchanger 16, the manifold 19, the connecting pipe 20, the regenerator 6 and the cooler 7, and the compression cylinder 3 Most of the working fluid flows into the compression cylinder 3 when the expansion piston 2 reaches the top dead center. At this time, the heat of the working fluid is taken by the regenerator 6 while passing through the regenerator 6, and then cooled by the cooler 7. When the compression piston 4 starts moving from the bottom dead center to the top dead center with the rotation of the output shaft 12,
The low-temperature working fluid in the compression cylinder 3 is compressed and flows into the expansion cylinder 1 by a route opposite to that before. At this time, the working fluid absorbs heat while passing through the regenerator 6 and is heated to a high temperature, and is further heated when passing through the heat exchanger 16 next time. The high-temperature working fluid flowing into the expansion cylinder 1 expands and pushes down the expansion piston 2. After that, the above-described operation is repeated, the output shaft 12 continues to rotate even when the external power source is turned off, and the operation as the Stirling engine is performed.

Therefore, the combustion flame (high temperature gas) generated in the combustion chamber 15
Heats the working fluid through the heat exchanger 16 while convection in the combustion chamber 15, but the hot gas after heating becomes combustion exhaust gas and after preheating the combustion air in the air preheater 18, it is discharged from the exhaust duct 33. It

A part of this combustion exhaust gas is supplied to the mixing chamber 32 in the ejector 30 via the exhaust gas passage 34. That is, in the ejector 30, since air is jetted from the tip of the nozzle 31 to eject air, a negative pressure is generated in the mixing chamber 32. This negative pressure causes combustion exhaust gas to flow through the exhaust gas passage 34 into the mixing chamber 32.
It is sucked in and mixed with air.

At this time, the exhaust gas is cooled in the mixing chamber 32, so that condensed water is generated in the mixing chamber 32. This condensed water flows down into the drain pipe 37. Here, since the solenoid valve 38 is normally open, the check valve 39 is closed by the negative pressure in the mixing chamber 32. Therefore, the condensed water 40 accumulates in the drain pipe 37 above the check valve 39. Next, when condensed water has accumulated in the drain pipe 37 to some extent, the solenoid valve 38 is closed and the check valve 39
Is opened because negative pressure is not applied, and the condensed water 40 accumulated thereabove is discharged.

In this way, the inside of the mixing chamber 32 is always maintained in a negative pressure state, and the condensed water can be discharged while performing the exhaust gas recirculation.

FIG. 2 shows another embodiment of the means for discharging the condensed water in the mixing chamber 32, which is a string-shaped absorbing member made of a material that easily absorbs liquid.
One end of 41 is inserted into mixing chamber 32. The condensed water generated in the mixing chamber 32 permeates the absorbing member 41 and is guided downward,
When it penetrates to some extent, it is discharged as a water droplet from the tip of the member 41. Even with this structure, the same effect as that of the previous embodiment can be obtained.

EFFECTS OF THE INVENTION According to the present invention, a drainage pipe of condensed water is communicated with a lower portion of a mixing chamber of an ejector, a solenoid valve is inserted in the middle of the drainage pipe, and a solenoid valve is closed below the drainage valve when the solenoid valve is opened. By inserting such a check valve, the condensed water in the mixing chamber can be discharged while maintaining the negative pressure state of the mixing chamber.

Therefore, the efficiency of the ejector does not decrease due to the accumulation of condensed water in the mixing chamber, and the combustion exhaust gas is sucked in favorably, so that the NOx reduction action by exhaust gas recirculation can be stably obtained for a long time. Further, the condensed water generated in the mixing chamber does not reach the combustion chamber and lowers the temperature of the combustion gas, the heat exchange efficiency of the heat exchanger in the combustion chamber is maintained well, and the heating of the working fluid is effective. You can

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a Stirling engine according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of another embodiment. 1 ... expansion cylinder, 2 ... expansion piston, 3 ... compression cylinder, 4 ... compression piston, 5 ... heater, 6 ...
Regenerator, 7-cooler, 8,9-connecting rod, 10,11-crank shaft, 12-output shaft, 13-cylinder head, 14,26 to 28-heat insulating material, 15 --- Combustion chamber, 16
...... Heat exchanger, 17 …… Gas nozzle, 18 …… Air preheater,
19 …… manifold, 20 …… connection pipe, 21 …… crank chamber,
22,23 …… Linear bearings, 24,25 …… Refrigerant piping, 29…
… Swirlers, 30 …… Ejectors, 31 …… Nozzles, 32 ……
Mixing chamber, 33 ... Exhaust duct, 34 ... Exhaust gas passage, 35 ...
Air passage, 36 ... Air supply port, 37 ... Drain pipe, 38 ... Solenoid valve, 39 ... Check valve, 40 ... Condensed water.

Claims (1)

(57) [Claims] 1. A Stirling engine heater having a combustion chamber and a heat exchanger for heating a working fluid provided in the combustion chamber, an ejector having a nozzle for ejecting air and a mixing chamber, and the ejector. And an air passage for supplying combustion air to the combustion chamber, an exhaust gas passage for guiding a part of the combustion exhaust gas discharged from the combustion chamber to the mixing chamber of the ejector, and a communicating portion under the mixing chamber of the ejector for condensation. A drain pipe for discharging water, a solenoid valve inserted in the middle of the drain pipe, and a check valve inserted in the drain pipe below the solenoid valve and closed when the solenoid valve is opened. A heater for a Stirling engine, characterized by being equipped with.