JPS6388250A - Stirling engine - Google Patents

Abstract

PURPOSE:To enable a blower to reduce its power and noise or the like when anno NOx is generated, by controlling a passage of air to be switched to the first or second passage in accordance with the operative condition of a Stirling engine main unit. CONSTITUTION:A controller 13, when an engine is ignited, opens a proportional control valve 32 supplying air from a blower 11 to a Stirling engine main unit 40 through a bypass passage 22, and the engine, to which a large amount of air is supplied with a less pressure drop, enables the blower 11 to decrease its power and noise. While the engine, when it is in steady operation, supplies the air through the bypass passage 22 similarly to when the engine is ignited, but if a generated amount of NOx increases, the controller, which controls the proportional control valves 32, 31 to gradually switch the passage from a side 22 to a side 21, opens a solenoid valve 33 performing the exhaust gas recirculation (EGR) by an air ejector 12, and an emitting amount of NOx is suppressed. In this way, the engine enables the power of the blower and its noise to be reduced, when no NOx is generated, while the generated amount of NOx to be reduced by the EGR when NOx is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a Stirling engine, and particularly to a Stirling engine with an improved combustion system.

(Prior Art) In recent years, as part of efforts to save energy, the Stirling engine has been reconsidered and intensive research is being conducted. In this Stirling engine, a heater is generally connected to an expansion cylinder, a cooler is connected to a compression cylinder, and the heater and cooler are connected by a regenerator, which is movably housed in the expansion cylinder. An expansion piston and a compression piston movably housed within a compression cylinder are coupled to a crankshaft. A fluid such as helium is sealed in the path extending from the Di cylinder to the compression cylinder. and,! ] When the working fluid is heated and expanded by the 0-heater, the piston descends and rotates the crankshaft, and when the expansion piston rises, the working fluid is pushed out and transferred to the compression cylinder side.

By the way, in the above-mentioned Stirling engine, the heater is heated by high-temperature gas generated in the combustor, but even after heating the heater, the high-temperature gas remains at 70%.
It maintains a high temperature of 0 to 800 ["C]. For this reason,
In order to recover waste heat from the high-temperature gas after heating, thermal efficiency is improved by exchanging heat with combustion air.

However, this type of organization had the following problems. In other words, preheating of the combustion air increases the combustion temperature, which increases nitrogen oxides (which are the cause of photochemical smog).
There is a problem in that it leads to the emission of NOx). It is known that this NOx has a strong dependence on temperature and increases exponentially as the air preheating temperature rises.

In addition, if the combustion air is not preheated using waste heat,
This not only leads to a decrease in efficiency, but also leads to incomplete combustion and an increase in the time from ignition to steady operation.

(Problem to be solved by the invention) In this way, in the conventional Stirling engine, increasing the preheating of the combustion air reduces the amount of NOx contained in the combustion exhaust gas.
There were problems such as an increase in the amount of combustion air and no improvement in efficiency could be expected if the preheating of the combustion air was reduced.

The present invention has been made in consideration of the above circumstances, and its purpose is to improve efficiency by sufficiently increasing the preheating of combustion air, and to reduce the generation of NOx, thereby reducing pollution. Our goal is to provide an efficient Stirling engine.

[Structure J of the Invention (Means for Solving the Problems) The gist of the present invention is to adopt a recirculation combustion method in which a part of the combustion exhaust gas is mixed with combustion air, and furthermore, the combustion exhaust gas is mixed with combustion air. The method consists in using an air ejector for mixing with air and a passage bypassing the ejector.

That is, the present invention includes a Stirling engine main body, an air ejector provided on the air inlet side of the Stirling engine main body, and a first passage that supplies combustion air to the air inlet of the Stirling engine via the air ejector. , a second passage that branches from the inlet side of the air ejector and merges at the outlet side of the ejector; a third passage that guides combustion exhaust gas exhausted from the exhaust pipe of the Stirling engine main body to the air ejector; A Stirling engine comprising a proportional control valve provided in each of the first and second passages and regulating the flow rate of fluid flowing in the passage, and a controller that drives and controls these proportional control valves. Yes, NOxffi in combustion exhaust gas
The combustion air is supplied by selecting the first and second passages according to the conditions.

(Function) With the above configuration, 1. A portion of the combustion exhaust gas can be mixed with combustion air through the third passage, and by supplying this mixed air to the Stirling engine body through the first passage, NOx can be reduced.

Combustion air is supplied through the first air passage through the air ejector when NOx is high, and through the second air passage that bypasses the air ejector when NOx is low, so excessive power is applied to the blower that supplies the air. This makes it possible to realize a Stirling engine with low optical pollution without causing any damage.

In other words, in the exhaust gas recirculation combustion method in which a part of the combustion exhaust gas is mixed into the combustion air, the N0xl in the combustion exhaust gas is
Depending on t, the combustion air supply passage can be used on either the air ejector side or the bypass side, or both can be used while maintaining a balance. Therefore, the blower has low noise without giving excessive power to the blower or the like, and furthermore, it is possible to reduce NOx.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing a Stirling engine according to an actual flow example of the present invention. 11 in the figure is a blower,
The air supplied from the blower 11 is supplied into the air ejector 12, and the air blown out from the air ejector 12 is supplied to the air inlet 53 of the Stirling engine main body 40 through the first passage 21. A bypass passage (second passage) 22 that bypasses the ejector 12 is provided from the inlet side of the air ejector 12, and this bypass passage yI22 is connected to the air inlet 53 of the Stirling engine main body 40. . Further, the exhaust pipe 51 of the Stirling engine main body 40 is provided with an exhaust gas passage (a third
passage) 23 is connected.

The air ejector 12 includes a nozzle 12a and a mixing chamber 12.
When air is supplied to this air ejector 12, two air jets are ejected from the nozzle 12a, thereby generating negative pressure in the mixing chamber 12b. A part of the exhaust gas is mixed with air due to this negative pressure, and is supplied to the Stirling engine main body 40 through the first passage 21.

Also, the outlet of the air ejector 12 and the bypass passage 2
Proportional control valves 31 and 32 are respectively arranged in the exhaust gas passage 23, and a solenoid valve 33 is arranged in the exhaust gas passage 23. The proportional control valves 31 and 32 adjust the flow rate of the fluid by varying the valve opening degree based on the control command, and the 'RfjJ valve 3
3 opens and closes the valve by the third order of the valve leg. and,
The proportional control valves 31 and 32 and the solenoid valve 33 are controlled by the controller 13.

On the other hand, the Stirling engine main body 40 has a well-known configuration, for example, as shown in FIG. 2. That is, it consists of an expansion cylinder 41, a compression cylinder 42, a high temperature side heat exchanger 43 as a heat exchanger, a low temperature side heat exchanger 44, and a regenerator 45, which are connected to each other to close the working fluid. A flow path 46 is formed. As the working fluid flowing in this closed flow path 46, non-condensable He or the like is used.

The high temperature side heat exchanger 43 has a combustion chamber 48 partitioned by a heat insulating material 47, and a gas nozzle 49 faces the top of the combustion chamber 48. The preheated air introduced from the air inlet 53 and the fuel gas supplied from the gas nozzle 49 are mixed and combusted within the combustion chamber 48. Further, a heater 52 is provided within the combustion chamber 48 . This heater 52 causes a working fluid to flow through an internal passage to exchange heat with an external heat source within the combustion chamber 48 .

The bottom side of the combustion chamber 48 is communicated with an exhaust stack 51 via an air preheater 50. The exhaust gas passage 23 is connected to this exhaust pipe 51. Furthermore, the air inlet 53 is connected to the passage 21.22.

Next, the operation of the Stirling engine configured as described above will be explained.

First, when ignition is started, high-temperature gas generated by combustion of fuel heats the heater 52 while convecting inside the combustion v48, raising the temperature of the working fluid.

In order to make the Stirling engine more self-sustaining, it is necessary to quickly raise the temperature of the working fluid, and at the time of ignition, it is necessary to increase the fuel flow rate and air flow rate to increase the heat input.

In order to increase the air flow rate, the power supplied by the blower 11 is increased. The noise from the blower 11 becomes louder, but at this time, the hot gas humidity or air preheating temperature is relatively low, so naturally the N
Ox emissions are also lower.

Therefore, only the proportional control valve 32 on the bypass passage 22 is kept open, and the combustion air is transferred to the bypass passage with low pressure loss.
2. Thereby, the power and noise of the blower 11 can be reduced.

When the Stirling engine begins to stand on its own and the temperature of each part approaches a steady state, the fuel flow, air flow rate, etc. return to a steady state depending on the operating conditions. At this time, the power supplied to the blower 11 and the noise are also in a steady state.

When the high-temperature gas or air preheating temperature rises further and reaches a temperature at which the amount of NOx emissions increases, a signal from the aft controller 13 causes the proportional control valve 32 on the bypass passage 22 and the proportional control valve 31 on the outlet side of the air ejector 12 to be activated. The solenoid valve 33 is opened gradually. At this time, the switching of the proportional control valves 31 and 32 is adjusted so that the color of the air (including exhaust gas) supplied to the Stirling engine main body 40 is maintained constant.

When the proportional control valve 31 opens, a part of the exhaust gas that has passed through the exhaust gas passage 23 within the air ejector 12 mixes with air.
The air is supplied to the air inlet 53 of the Stirling engine body 40 through the passage 21 .

The exhaust gas recirculation method, which mixes part of the exhaust gas with air, lowers the peak temperature of high-temperature gas by increasing heat capacity, etc.
This reduces NOx emissions.

Therefore, by supplying a part of the exhaust gas mixed with air, the exhaust gas W15 of the Stirling engine main body 40 is
It becomes possible to reduce Noxffi in the combustion exhaust gas exhausted from the combustion engine. Also, at this time, the proportional control valve 31
．． 32 is not completely switched, but the opening degrees of the proportional control valves 31 and 32 are controlled according to the amount of NOx discharged. , it becomes possible to avoid a sudden increase in the noise of the blower 11.

Thus, according to this practical example, by driving and controlling the proportional control valves 31, 32 and the solenoid valve 33 according to the NOx discharge n, air supply is controlled in each mode during ignition, steady operation, and NOx generation. The system can be optimized. That is, at the time of ignition, by supplying air through the bypass passage 22, a large amount of air can be supplied with less pressure loss, and the power and noise of the blower 11 can be reduced. During steady operation, the power and noise of the blower 11 can be reduced by supplying air through the bypass passage 22 as in the case of ignition. In addition, when the amount of NOx emissions increases, by gradually switching the air passage from the 22 side to the 21 side, NOx emissions can be reduced.
Emissions can be reduced. In this case, the power and noise of the blower 11 gradually increase. Note that since the air supply to the Stirling engine main body 40 is kept constant, the Stirling engine will not be adversely affected.

In this way, by using the air ejector 12, which has a large pressure loss and causes excessive power to the blower 11 and generates large noise, only when the NOx emission rate increases, the blower power and noise can be reduced. ! minimize,
It becomes possible to reduce NOx. Further, since there is no need to suppress preheating of the combustion air, it is possible to prevent the risk of thermal efficiency decreasing or incomplete combustion occurring.

Note that the present invention is not limited to the above-mentioned practical example. For example, instead of the electromagnetic valve disposed in the third passage, any valve that blocks the flow of fluid from the air ejector side to the exhaust pipe side may be used, and a check valve or the like may be used.

Furthermore, when supplying air through the second passage, if the pressure difference between the air ejector and the exhaust stack is not too large, it is also possible to omit the solenoid valve. Furthermore, the air ejector structure is not limited to the one shown in Fig. 1; in short, a part of the exhaust gas led from the third passage is mixed with air, and this is supplied to the Stirling engine body through the first passage. It is fine as long as it is done. Further, as means for detecting NOxl in the exhaust gas, a detector that directly detects the concentration of NOx, a detector that detects the temperature of combustion gas, or the like may be used. Further, the configuration of the Stirling engine main body is not limited to that shown in FIG. 2 in any way, but can be changed as appropriate according to specifications. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, by switching the air passage to the first or second passage depending on the operating state of the Stirling engine body, when no NOx is generated, the floor It is possible to reduce power, noise, etc., and when NOx is generated, the generation of NOx can be reduced by recirculating the exhaust gas. Therefore, not only can preheating of combustion air be sufficiently increased to improve efficiency, but also NOx generation can be reduced, making it possible to realize a low-pollution and highly efficient Stirling engine.

[Brief explanation of the drawing]

FIG. 1 shows a Stirling engine according to an embodiment of the present invention. FIG. 2 is a sectional view showing the schematic structure of the Stirling engine main body. 11... Blower, 12... Air ejector, 13
...Controller, 21...First passage, 22...Second
passage (bypass passage), 23... third passage (exhaust gas passage), 31.32... proportional $ guilty plea, 33...
Solenoid valve, 40... Stirling engine body, 51.
...Exhaust pipe 53...Air inlet. Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (2)

[Claims] (1) a Stirling engine main body, an air ejector provided on the air inlet side of the Stirling engine main body, a first passage that supplies combustion air to the air inlet of the Stirling engine via the air ejector; a second passage that branches from the inlet side of the air ejector and merges at the outlet side of the ejector; a third passage that guides combustion exhaust gas exhausted from the exhaust pipe of the Stirling engine main body to the air ejector; and a second proportional control valve provided in each of the passages to adjust the flow rate of fluid flowing in the passage, and a controller to drive and control these proportional control valves. . (2) Each proportional control valve provided in the first and second passages is controlled according to the amount of nitrogen oxides in the combustion exhaust gas exhausted from the exhaust stack of the Stirling engine main body. A Stirling engine according to claim 1.