JPH0329563Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] The present invention relates to an air preheater for a hot gas engine that performs heat exchange between high temperature exhaust gas and low temperature combustion air.

[Application field of this invention]

Improving engine thermal efficiency by exchanging heat between high-temperature exhaust gas and low-temperature combustion air, effectively utilizing the thermal energy of exhaust gas without wasting it outside, and increasing the temperature of low-temperature combustion ventilation. It is effective for improving combustion and is used, for example, in Stirling engines.

[Prior art]

An air preheater for a hot gas engine is related to an earlier application filed by the present applicant (Japanese Patent Application No. 54-28898).

For example, FIG. 1 shows an air preheater for a Stirling engine. Air is supplied from an air supply duct 1 and led to an air passage 3 through an air inlet 2. Furthermore, the air is led to the heat exchange element 5 from the heat exchange element air inlet 4. The air guided to the heat exchange element 5 exchanges heat with high-temperature exhaust gas, as will be described later. After heat exchange, the high-temperature air passes through the passage 6 and is turned into a swirling flow by the ventilation swirler 7 and supplied to the combustion space 8 . on the other hand,
Fuel is injected from the nozzle 9 into the combustion space 8,
It mixes with the swirling flow and burns. The combustion gas burns while imparting heat to the heater head 10, becomes exhaust gas, and is led to the heat exchange element 5 via the exhaust gas inlet 11. Heat exchange element 5
is corrugated and divides the flow path into approximately two parts.
Cold air flows on one side and hot exhaust gas flows on the other. The exhaust gas led to 5, which underwent heat exchange, is
After exchanging heat with low-temperature air as described above, the exhaust gas passes through the exhaust gas passage 12 and is discharged to the outside from the exhaust gas outlet 13.

[Disadvantages of conventional technology and its technical analysis]

For example, in a Stirling engine, in order to increase the thermal efficiency of the engine, it is necessary to increase the temperature of the heater head. Then, the temperature of the exhaust gas after heat exchange also rises accordingly. For example, if the heater head is set at 800°C, the exhaust gas temperature may reach 900-1000°C. This high-temperature exhaust gas flows into the heat exchange element 5 through the exhaust gas inlet 11. Therefore, after long-term operation, the heat exchange element 5 undergoes thermal stress due to the heat of the exhaust gas and corrosive substances. As a result of corrosion and oxidation, crevices, pitting corrosion, and blockage of flow paths occur, resulting in failures such as poor sealing between air and exhaust gas and reduced temperature efficiency.

By the way, when we observed the heat exchange element 5 where the failure actually occurred, we found that most of the defects occurred at the bent portion 14 near the exhaust gas inlet 11, and the damage to other portions was extremely small. small. In other words, the bent portion 14 is the key to the service life.

The reason for this can be easily understood when considering the flow of exhaust gas. That is, the exhaust gas hits the curved portion 14 vertically, as shown by the arrow in FIG. This is because it gets heated and reaches a high temperature.

[Technical issues]

Therefore, the technical problem of the present invention is to prevent local heating in the bent portion 14 and extend the life of the bent portion 14.

[Technical means]

The technical means taken to solve the above technical problem was to install a protective plate with a plurality of slits that communicate the combustion space with the exhaust gas flow path in the heat exchange element. The curved portion of the corrugated heat exchange element is placed at the inlet and engaged between adjacent slits of the protection plate.

[Effect of technical means]

The above technical means works as follows. That is, the protection plate 15 is made of a heat-resistant material such as ceramic, and is provided with slits 15a having the same shape and the same number of slits 15a at equal pitches as the exhaust gas flow paths 16 of the heat exchange element. It communicates with each of the heat exchange elements 5 on a one-to-one basis, and is installed on the inner periphery of the heat exchange element 5.

For this purpose, the exhaust gas is transferred from the combustion space 8 through the heater head 10, after which it is heated as shown in FIG.
As shown by the arrow in FIG. 3, the exhaust gas passes through the slit 15a provided in the protection plate 15, flows into the exhaust gas passage 16, and exchanges heat with the air.
In this structure, the bent portion 14 is protected by the protection plate 15 and is not exposed to exhaust gas directly, so that it is not locally heated.

[Special effects produced by the present invention]

The present invention produces the following unique effects. That is, in the conventional system, the technical problem can be solved by supplying low-temperature air from a small hole etc. near the exhaust gas inlet 11 to lower the temperature of the exhaust gas. Another problem arises: increased power requirements and decreased thermal efficiency.

In contrast, the present invention only prevents the local heating of the bent portion 14, which is the key to the service life. The thermal area is
It is small, accounting for less than 1% of the total, and can solve technical problems without causing any major problems.

[Embodiment of the idea]

A protective plate with slits of the same shape and pitch at the same pitch as the curved portion of the heat exchange element is arranged around the inner circumference of the heat exchange element.

The structure is such that the area of the slit in the above-mentioned protection plate is varied in the pitch direction. This provides a flow rate adjustment function when heat exchange with air is poor due to variations in the flow rate of exhaust gas flowing through each of the exhaust gas flow paths 16, and can improve thermal efficiency.

The slits in the above protective plate are burred. In this case, the pressure loss of the exhaust gas when passing through the slit can be reduced.

The above-mentioned protective plate is provided with flanges, stays, etc., and the structure is such that it can be positioned or fixed to other members of the air preheater using fasteners such as pins or bolts.

The above protective plate is divided into multiple parts. In this case, if a malfunction occurs such as damage to a part of the protective plate, only that part can be replaced, and by treating the protective plate as a consumable item,
It is possible to reduce the cost of materials.

The structure is such that the protective plate shown above and the outer wall of the combustion space are integrated.

〔Example〕

An example illustrating a specific example of the above technical means will be described below. For the example shown in Figure 2,
A protective plate 15 and a slit 15a.
is fixed to the outer wall 17 of the combustion space 8 arranged on the inner periphery of the heat exchange element 5.

In the example shown in FIG. 4, the protection plate 15 has a flange 15b and is fixed to the outer wall 17 of the combustion space 8 by bolts 18. The example shown in FIG. 5 has a structure in which the protection plate and the combustion space 8 are integrated.

The example shown in FIG. 6 has a structure in which the area (width in FIG. 6) of the slit 15a is varied in the pitch direction of the slit 15a to provide an exhaust gas flow rate adjustment function.

In the above example, the exhaust gas flows into the exhaust gas flow path 16 through the slit 15a, as shown in FIGS. 2 and 3, but the bent portion 14 is protected by the protection plate 15. No local heating occurs.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional air preheater for a Stirling engine, and FIG. 2 is a sectional view showing a specific example of the air preheater for a Stirling engine of the present invention.
3 is a partially enlarged sectional view taken along the arrow A-A line in FIG. 2, FIG. 4 is an enlarged sectional view showing a modified embodiment of FIG. 3, and FIG. FIG. 6 is a cross-sectional view of still another modified embodiment showing a portion indicated by an arrow B in FIG. 2 in an enlarged manner. FIG. 5... Heat exchange element, 8... Combustion space, 5
a...slit, 14...bend part, 16...
Exhaust gas flow path.

Claims (1)

[Claims for Utility Model Registration] (1) Having a combustion space and a flow path for air and exhaust gas inside, dividing the flow path into approximately two parts, with air flowing through one side and exhaust gas flowing through the other, and mixing with each other. In the air preheater for a hot gas engine, the air preheater has a corrugated heat exchange element that allows heat exchange to be performed without any heat exchange, and the air preheater includes a plurality of air preheaters that communicate the combustion space with the exhaust gas flow path in the heat exchange element. A protection plate provided with slits is disposed at the exhaust gas inlet of the heat exchange element, and a bent portion of the corrugated heat exchange element is engaged between adjacent slits of the protection plate. Features: Air preheater for hot gas engines. (2) The air preheater for a hot gas engine according to claim 1, wherein the cross-sectional area of the slit is varied in the pitch direction.