JPH05179942A - Exhaust device for engine - Google Patents

Abstract

PURPOSE:To promote oxidizing and deoxidizing action of catalyst so as to improve purifying efficiency for exhaust gas, and efficiently recover exhaust heat and reaction heat generated on the catalyst. CONSTITUTION:Exhaust gas discharged from respective exhaust ports 3 of a cylinder head 1 is introduced to an exhaust emission control device 14 before being cooled with an exhaust gas cooling device 2, and hence the temperature of exhaust gas passed through the exhaust emission control device 14 is fully high, so as to improve reaction efficiency by catalyst and effectively remove harmful matter in the exhaust gas. The exhaust gas discharged from the exhaust emission control device 14 is introduced to the exhaust gas cooling device 2 in the obtain by adding reaction heat due to catalyst to the original exhaust heat, condition of the highest temperature, and hence heat recovery efficiency in the exhaust gas cooling device 2 is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust system provided with an exhaust cooling system, and more particularly to a liquid-cooled exhaust manifold for an engine for a cogeneration system.

[0002]

2. Description of the Related Art A cogeneration system generates electric power from a gas engine, a gasoline engine (diesel engine), etc., while utilizing the exhaust heat of these,
It supplies heat energy such as hot water supply and air conditioning, and has extremely high thermal efficiency. Some gasoline engines for automobiles used in such a cogeneration system include a liquid-cooled exhaust manifold that recovers exhaust heat from an exhaust manifold and converts it into effective heat energy. is there.

That is, an inner cylinder, through which exhaust gas flows, composed of each branch portion communicating with the exhaust port of the cylinder head in the exhaust manifold, and a collection portion thereof,
A double structure is formed by the outer cylinder that covers this, and a passage through which the cooling liquid circulates is formed between the inner cylinder and the outer cylinder, and heat exchange is performed between the exhaust gas flowing in the inner cylinder and the cooling liquid. Is being done. Recently, there has been an active movement to further purify harmful exhaust gas emitted from engines of automobiles and the like, and it has become general to equip a cogeneration system engine with a catalytic exhaust purification device. .. Conventionally, this exhaust purification device is provided in an exhaust pipe connected to the outlet side of a liquid-cooled exhaust manifold that is an exhaust cooling device to reduce HC, CO, NOx and the like which are harmful substances.

[0004]

In order to effectively purify the harmful substances in the exhaust gas by the catalyst of the exhaust gas purification device, the temperature of the exhaust gas flowing into the exhaust gas purification device is raised and the oxidation by the catalyst is carried out. It is preferable that the reducing action is performed efficiently.

However, as described above, in the conventional exhaust device, since the exhaust gas purification device is provided on the outlet side of the liquid cooling type exhaust manifold which is the exhaust gas cooling device, the temperature is cooled by the exhaust gas cooling device. Since the lowered exhaust gas is introduced into the exhaust gas purification device, there is a problem that the reaction of the catalyst is slow and efficient purification cannot be performed. In particular,
If this exhaust gas purification device is located on the downstream side of the exhaust pipe away from the engine, the temperature of the exhaust gas will be further lowered, and the efficiency of purification of harmful substances by the catalyst will be further reduced.

Further, if the exhaust gas purifying device is provided on the downstream side of the exhaust pipe, the temperature of the exhaust gas after passing through the catalyst becomes high. In order to further recover the heat generated by the reaction of such a catalyst, there is a system in which an exhaust cooling device similar to the exhaust cooling device on the upstream side is provided also on the downstream side of the exhaust purification device. There is a problem that the structure becomes complicated and the thermal efficiency is poor.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to accelerate the oxidation and reduction actions of the catalyst to enhance the exhaust gas purification efficiency and to reduce the exhaust heat. And to efficiently recover the heat of reaction generated in the catalyst.

[0008]

In order to achieve the above-mentioned object, according to the present invention, an outer cylinder covers a part of an outer peripheral portion of an exhaust pipe connected to an exhaust port of a cylinder head. In an exhaust system of an engine equipped with an exhaust cooling device for recovering exhaust heat of exhaust gas by circulating a heat exchange medium in a passage formed between the cylinder head and the exhaust cooling device in the exhaust pipe. An exhaust purification device equipped with a catalyst for purifying exhaust gas harmful substances is provided in the portion near the exhaust port. The above object can also be achieved by providing an exhaust gas purification device equipped with a catalyst for purifying exhaust gas harmful substances in the exhaust pipe at the inlet portion of the exhaust gas cooling device.

[0009]

Since the exhaust gas emitted from each exhaust port is introduced into the exhaust purification device before being cooled by the exhaust cooling device, the temperature of the exhaust gas passing through the exhaust purification device is sufficiently high, and therefore the reaction by the catalyst is caused. Efficiency is improved and harmful substances in exhaust gas are effectively purified.

Further, the exhaust gas discharged from the exhaust gas purification device is introduced into the exhaust gas cooling device in a state where the reaction heat from the catalyst is added to the exhaust gas in addition to the original heat of the exhaust gas, and is introduced into the exhaust gas cooling device. The efficiency of heat recovery is improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a gasoline engine for an automobile for a cogeneration system including a first embodiment of the present invention. On one side of the cylinder head (1),
Liquid-cooled exhaust manifold (exhaust cooler) detailed below
(2) is attached.

As shown in FIGS. 2 and 3, the cylinder head
On the side surface of (1), there are a branch part (4a) communicating with each exhaust port (3) and a collecting part (collector) (4b) having a substantially oblong cylindrical shape for collecting them, and the exhaust pipe While covering the inner cylinder (4) forming a part of the inner cylinder (4) and the periphery of the inner cylinder (4),
An outer cylinder that is integrally connected to the outer wall with a required distance.
(5) is a bolt (7) fixed to the side wall of the cylinder head (1) with a plurality of flanges (6) projecting from the upper and lower ends of the outer cylinder (5) with a slight downward inclination. There is.

The exhaust gas passages (4c) extending from the branch portions (4a) to the exhaust pipes (8) connected to one side of the inner pipe (4) are gently sloping so as to communicate in substantially the same plane. The core (4), which is bent into the shape of a core (not shown) and main mold during casting.
By simplifying the structure of the outer cylinder (5) for covering them, the molding thereof can be facilitated while the die cutting can be easily performed.

At the front and rear ends of the outer cylinder (5) (hereinafter, the left side in FIG. 1 is the front), the cooling liquid (heat exchange medium) (10)
The supply part (11) and the outflow part (12) are connected in the front-rear direction, and the passage (1) between the inner cylinder (4) and the outer cylinder (5) is extended from the supply part (11).
The cooling liquid (10) flowing into the inside 3) is warmed by exhaust heat and then flows out from the outflow part (12), for example, after supplying heat to a heating device (not shown), to the supply part (11). It is designed to recirculate and recirculate.

As shown in FIG. 3, the exhaust gas and the cooling liquid (10) flow in opposite directions so that the cooling liquid (10) flows in the opposite direction.
The temperature difference between (10) and the inner cylinder (4) is always kept large so that the heat exchange rate can be increased.

(14) is an inner cylinder which is an inlet of the exhaust cooling device.
An exhaust gas purification device fitted in the branch portion (4a) of (4), which is, for example, platinum or a catalyst such as platinum in this embodiment.
A known monolith catalytic converter having an alumina coat layer carrying (not shown) is used.

When the exhaust gas passes through the exhaust purification device (14), harmful substances in the exhaust gas are removed by the oxidation and reduction actions of the catalyst.

Next, the operation of the above-mentioned first embodiment will be described. When the high-temperature exhaust gas exiting the exhaust port (3) passes through the exhaust purification device (14), HC and C contained in the exhaust gas
Hazardous substances such as O and NOx react with the catalyst and react with the exhaust gas purification device (1
4) Adsorbed inside and removed from the exhaust gas, the reaction heat at that time causes the exhaust gas to become even hotter,
The temperature of the entire exhaust purification device (14) rises.

However, the exhaust gas purification device (14) has a cooling liquid (10).
Since it is fitted in the branch portion (4a) of the inner cylinder (4) in which the air is circulated, the heat of the exhaust gas purification device (14) is transferred to the branch portion (4a).
The liquid is effectively collected in the cooling liquid (10) in the passage (13) via the. Therefore, even if the purification with the catalyst is continuously performed, the temperature of the exhaust purification device (14) as a whole does not rise excessively and is maintained at a substantially constant temperature. , Effectively recovered in the cooling liquid (10). While passing through the inner cylinder (4), the exhaust gas discharged from the exhaust gas purification device (14) is heat-exchanged with the cooling liquid (10) in the passage (13) to have a low temperature, and the exhaust pipe (9). And it is discharged to the outside through the muffler.

As described above, in the first embodiment, the exhaust purification device (14) is arranged at the inlet of the liquid cooling type exhaust manifold (2) which is the exhaust cooling device.
There is no concern that low-temperature exhaust gas is introduced into the exhaust gas purification device (14) as in the past, and the reaction efficiency by the catalyst is improved and the purification efficiency of the exhaust gas is increased, and the cooling liquid (10) that is a heat exchange medium. The heat recovery efficiency is also improved.

FIG. 4 shows a second embodiment of the present invention. The same members as those shown in the first embodiment are designated by the same reference numerals, detailed description thereof will be omitted, and only the characteristic points will be described below. In the second embodiment, an exhaust gas purification device (14) is provided for each exhaust port (3) of the cylinder head (1) and for the inner cylinder (4) of the liquid cooling type exhaust manifold (2) which is an exhaust cooling device. It is provided in a connecting pipe (16) that connects each branch portion (4a).

In this way, the exhaust gas purifying device (14) is not directly cooled by the cooling liquid (10), and other than that, the same action and effect as those of the first embodiment can be obtained. it can.

That is, since the high-temperature exhaust gas exiting the exhaust port (3) is introduced into the exhaust gas purification device (14) at a high temperature, the efficiency of purification of harmful substances is good and the exhaust gas purification device (1
Exhaust gas that has become even hotter after passing through 4) is introduced into the liquid-cooled exhaust manifold (2), which is an exhaust cooling device, so that heat recovery efficiency is also improved.

In the first and second embodiments, the exhaust cooling device is provided on the exhaust manifold to form the liquid-cooled exhaust manifold (2). However, the exhaust cooling device is located at an appropriate position on the exhaust pipe downstream of the exhaust manifold. It may be provided in. In this case,
The exhaust purification device (14) is an exhaust port of the cylinder head (1).
Exhaust pipe (including exhaust manifold) closest to (3) inlet of exhaust cooling device or closer to exhaust port (3)
It should be installed in the right place. In short, the exhaust gas purification device (14) may be arranged on the upstream side of the exhaust gas cooling device.

As described above, according to the liquid-cooled exhaust manifold of the present invention, the high temperature exhaust gas is introduced into the exhaust purification device (14) to enhance the reaction efficiency by the catalyst. Therefore, not only the efficiency of purifying harmful substances is improved, but also the heat of reaction of the catalyst generated in the exhaust gas purification device (14) can be efficiently recovered with the cooling liquid (10) to improve the heat exchange efficiency.

[0026]

The present invention has the following effects. (a) Since the hot exhaust gas before being cooled by the exhaust cooling device passes through the exhaust purification device, oxidation and reduction actions by the catalyst in the exhaust purification device are actively performed, and harmful substances in the exhaust gas are Can be removed efficiently. (b) Since the high temperature exhaust gas, which has become higher by the reaction heat of the catalyst by passing through the exhaust purification device, is introduced into the exhaust cooling device, the heat recovery efficiency in the exhaust cooling device is improved. It can be significantly increased over conventional ones. (c) If the exhaust gas purification device is provided in the exhaust pipe at the inlet of the exhaust gas cooling device (the invention of claim 2) and the exhaust gas purification device is directly cooled by the exhaust gas purification device, the exhaust gas purification device malfunctions. The temperature rise can be prevented, and the heat recovery efficiency can be further improved.

[Brief description of drawings]

FIG. 1 is a side view of an engine for a cogeneration system including a first embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional front view of a main part taken along the line AA in FIG.

3 is a cross-sectional plan view of the main part taken along the line BB in FIG.

FIG. 4 is a cross-sectional plan view of an essential part of the second embodiment of the present invention.

[Explanation of symbols]

(1) Cylinder head (2) Liquid-cooled exhaust manifold (exhaust cooling device) (3) Exhaust port (4) Inner cylinder (exhaust pipe) (4a) Branch part (4b) Assembly part (4c) Exhaust gas passage (5 ) Outer tube (6) Flange section (7) Bolt (8) Exhaust tube (9) Exhaust tube (10) Coolant (heat exchange medium) (11) Supply section (12) Outflow section (13) Passage (14) Exhaust Purifier (15) Passage (16) Connection pipe (exhaust pipe)

Claims (2)

[Claims] 1. An outer cylinder covers a part of an outer peripheral portion of an exhaust pipe connected to an exhaust port of a cylinder head, and a heat exchange medium is circulated in a passage formed between the exhaust pipe and the outer cylinder. In an exhaust system of an engine provided with an exhaust cooling device adapted to recover exhaust heat of exhaust gas, a catalyst for purifying exhaust gas harmful substances is provided in a portion of the exhaust pipe closer to the exhaust port of the cylinder head than the exhaust cooling device. An exhaust system for an engine, characterized by being provided with an exhaust purification system equipped with it. 2. A heat exchange medium is circulated in a passage formed between the exhaust pipe and the outer cylinder by covering an outer peripheral portion of a part of the exhaust pipe connected to the exhaust port of the cylinder head with an outer cylinder. In an exhaust system of an engine including an exhaust cooling device configured to recover exhaust heat of exhaust gas, an exhaust purification device including a catalyst for purifying exhaust gas harmful substances is provided in an exhaust pipe at an inlet portion of the exhaust cooling device. An engine exhaust system characterized by being provided.