JPH0455221Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is an exhaust mechanism for an alcohol diesel engine, and more specifically, an exhaust system equipped with a catalyst for oxidizing aldehydes produced in incomplete combustion when alcohol fuel is burned. Regarding the exhaust mechanism.

[Technical background of the invention] An alcohol diesel engine is a diesel engine that uses alcohol as fuel, but when the alcohol is completely combusted, carbon dioxide and water are produced. However, it is known that when incomplete combustion occurs, aldehydes, which are intermediate products in oxidation, are produced. This aldehyde is an irritating and toxic gas, and it is undesirable for it to be released into the atmosphere from the exhaust system of a diesel engine. For this reason, a catalyst for oxidizing the aldehyde is provided in the exhaust system of the diesel engine,
Exhaust mechanisms are known in which the aldehyde is oxidized, converted into carbon dioxide and water, and released into the atmosphere.

However, as is well known, the aldehyde oxidation catalyst is active within a predetermined temperature range, so if the exhaust gas is at a low temperature, it may not be possible to oxidize aldehyde, or the aldehyde oxidation efficiency may be low. This will result in a significant decrease in the amount of aldehydes that will be released into the atmosphere. Alcohol is incompletely combusted and a large amount of aldehyde is produced when alcohol is combusted at a low temperature, i.e. when a diesel engine is started or idling. The oxidation catalyst had low activity and was unable to oxidize a large amount of aldehyde.

Therefore, in an exhaust system in which a main catalytic converter 3 filled with an aldehyde oxidation catalyst is provided in the exhaust pipe 2 of a diesel engine 1 as shown in FIG. 21, an auxiliary catalytic converter 4 having a smaller heat capacity than the main catalytic converter 3 is provided, and an exhaust gas cutoff means 5 is formed in the main exhaust pipe 22. According to this exhaust mechanism, when the exhaust gas is at a low temperature, the exhaust gas cutoff means 5 of the main exhaust pipe 22 is closed, the exhaust gas flows into the branch pipe 21, and the secondary catalytic converter 4 provided in the branch pipe 21 is closed. This allows exhaust gas to pass through. Since the secondary catalytic converter 4 has a small heat capacity, the catalyst within the secondary catalytic converter 4 reaches a high temperature in a short time, and the aldehyde is efficiently oxidized.

However, even in this case, it takes some time to raise the temperature of the sub-catalytic converter, and it is desired to raise the temperature of the catalyst more efficiently.

[Purpose of invention]

This invention was made in view of the above points,
In the exhaust system of an alcohol diesel engine equipped with a sub-catalytic converter as described above, the exhaust system is capable of raising the temperature of the catalyst in the sub-catalytic converter more quickly than in the past and oxidizing aldehydes more efficiently. The purpose is to provide a mechanism.

[Structure of the idea]

In order to achieve the above object, the exhaust mechanism for an alcohol diesel engine of the present invention includes a main catalytic converter filled with an aldehyde oxidation catalyst provided in the exhaust pipe of the alcohol diesel engine, and a main catalytic converter provided upstream of the main catalytic converter. Exhaust gas blocking means, a branch pipe that branches upstream of the exhaust gas blocking means and joins upstream of the main catalytic converter, and the main catalytic converter provided in the branch pipe and filled with an aldehyde oxidation catalyst. An exhaust system for an alcohol diesel engine having a secondary catalytic converter with a small heat capacity, characterized in that a throttle is formed in a branch pipe upstream and/or downstream of the secondary catalytic converter.

〔Example〕

FIG. 2 is a schematic diagram of an embodiment of the present invention. As is clear from this diagram, the exhaust pipe 2 of the diesel engine 1 is provided with a main catalytic converter 3 filled with an aldehyde oxidation catalyst. Ori,
The main exhaust pipe 22 upstream of the main catalytic converter 3 is provided with exhaust gas shielding means, such as a butterfly valve 5, for blocking the main exhaust pipe 22.

On the other hand, the branch pipe 21 is formed so as to branch from upstream of the butterfly valve 5 and merge with the main exhaust pipe 22 upstream of the main catalytic converter 3. It is equipped. The auxiliary catalytic converter 4 is filled with an aldehyde oxidation catalyst similarly to the main catalytic converter 3. Furthermore, the heat capacity of the sub-catalytic converter 4 is smaller than that of the main catalytic converter 3, so that the temperature of the catalyst increases more quickly than that of the main catalytic converter 3.

In the present invention, a restriction 23 is provided in the branch pipe 21 upstream and/or downstream of the sub-catalytic converter 3.
is formed.

With this configuration, when the temperature of the exhaust gas is low, such as when the engine 1 is started or warmed up, the butterfly valve 5 is closed manually or automatically. When the butterfly valve 5 is closed, the exhaust gas will flow through the branch pipe 21 without passing through the main exhaust pipe 22, and all of the exhaust gas will pass through the sub-catalytic converter 4. At this time, since the throttles 23 are formed in the branch pipes 21 upstream and downstream of the auxiliary catalytic converter 4, the back pressure of the exhaust gas becomes high, and therefore the exhaust gas temperature rises quickly. Therefore, together with the fact that the heat capacity of the sub-catalytic converter 4 is small,
The temperature of the catalyst rises more rapidly than in the past, making it possible to oxidize aldehydes more efficiently.

Further, when the exhaust gas temperature is sufficiently high, the butterfly valve 5 is opened. In this case, most of the exhaust gas enters the main catalytic converter 3 via the main exhaust pipe 22 . At this time, the temperature is sufficiently higher than that of the main catalytic converter 3, so that aldehyde oxidation can be performed satisfactorily.

In the above embodiments, the throttles were provided upstream and downstream of the auxiliary catalytic converter, but it is clear that similar effects can be obtained even if the throttles are provided either upstream or downstream.

[Effect of idea]

As explained above, according to the alcohol diesel engine exhaust mechanism according to the present invention, since the throttle is provided upstream and/or downstream of the sub-catalytic converter, the engine is operated with high back pressure, and the exhaust temperature decreases. Rise quickly. Therefore, the temperature of the sub-catalytic converter rises rapidly, so that aldehyde can be oxidized efficiently. The advantage is therefore that the amount of aldehyde released into the atmosphere is significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an exhaust mechanism of a conventional alcohol diesel engine, FIG. 2 is a schematic diagram of an exhaust mechanism of an alcohol diesel engine according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of an exhaust mechanism of an alcohol diesel engine according to an embodiment of the present invention. FIG. 2 is a schematic diagram of an engine exhaust mechanism. 2... Exhaust pipe, 21... Branch pipe, 23... Throttle, 3... Main catalytic converter, 4... Sub-catalytic converter, 5... Exhaust gas blocking means.

Claims (1)

[Scope of utility model registration request] A main catalytic converter filled with an aldehyde oxidation catalyst provided in the exhaust pipe of an alcohol diesel engine; an exhaust gas cutoff means provided upstream of the main catalytic converter; In an exhaust system for an alcohol diesel engine, the exhaust system for an alcohol diesel engine includes a branch pipe that joins upstream of a catalytic converter, and a sub-catalytic converter that is provided in the branch pipe and that is filled with an aldehyde oxidation catalyst and that has a smaller heat capacity than the main catalytic converter. upstream of the catalytic converter and/or
Or an alcohol diesel engine exhaust mechanism characterized by forming a restriction in the downstream branch pipe.