US3716996A

US3716996A - Afterburner for internal combustion engine

Info

Publication number: US3716996A
Application number: US00188959A
Authority: US
Inventors: H Maruoka
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1970-12-30
Filing date: 1971-10-13
Publication date: 1973-02-20
Anticipated expiration: 1990-02-20
Also published as: CA946172A; FR2120675A5; DE2163983B2; JPS5032890B1; DE2163983C3; DE2163983A1

Abstract

An afterburning system for minimizing hydrocarbon and carbon monoxide, content left unburned in engine exhaust gases of an internal combustion engine. In the afterburning system, an improved afterburning stabilizer is provided including a porous enclosure for uniformly admixing an additional air-fuel mixture, which is burned to form a premixed flame therearound for anchoring the main combustion of the contaminated exhaust gases. A number of projections are mounted upon the porous enclosure for producing small disturbances in the flow of the exhaust gases and for acting as a stable heat source for the main combustion when the premixed flame is formed close to the tips thereof.

Description

United States Patent Maruoka Feb. 20, 1973 54] AFTERBURNER FOR INTERNAL 3,042,499 7/1962 Williams ..60/303 COIMBUSTION ENGINE 3,306,035 2/1967 Morrell ..60/286 Primary Examiner-Douglas Hart [75] Inventor: Hiroyuki Maruoka, Yokohama, Anomey yohn Lezdey Japan [73] Assignee: Nissan Motor Company Limited, [57] ABSTRACT Yokohama-lapan An afterburning system for minimizing hydrocarbon [22] il Oct 13 7 and carbon monoxide, content left unburned in engine exhaust gases of an internal combustion engine. In the PP N 188,959 afterburning system, an improved afterburning stabil- Foreign Application Priority Data izer is provided including a porous enclosure for On. 30, 1970 Japan "/122778 uniformly admixing an additional air-fuel mixture; which is burned to form a premixed flame therearound for anchoring the main combustion of the [58] 23/277 C contaminated exhaust gases. A number of projections are mounted upon the porous enclosure for producing [56] References Cited small disturbances in the flow of the exhaust gases and 1 I for acting as a stable heat source for the main com- UNITED STATES PATENTS bustion when the premixed flame is formed close to 2,203,554 6/1940 Uhri ..23 277 c the ups 10 Claims, 4 Drawing Figures FI I EXHAUST GASES /I5 SECONDARY Mb Io OF PROPER AIR I6 MIXTURE RATIO I40 CONTAMINATED CLEAN EXHAUST GASES EXHAUST GASES I8 I8 b 2K3 22 5 ADDITION/ii AIR E I ADDITIONAL 2 I I AIR- FUEL 23b {ADDITIONAL IXT RE I I FUEI \k I I9 I? I I 2| I I I 25 SERVO- MOTOR CONTROLLER I 2H3 2I CI L Fig. 4

INVENTOR HIROYIM'I Manuela m!n e ATTOR Y SHEET 3 OF 3 RECIRCULA- TION ZONE ZONE 1 l- 9;!jf .I-I L/IIIJAXY/I/I/ OF PROPER MIXTURE RATIO EXHAUST GASES 3 SMALL TURBULENCES ADDITIONAL AIR- FUEL MIXTURE ADDITIONAL AIR-FUEL MIXTURE PAIENTEDFEBZOIQH AFTERBURNER FOR INTERNAL COMBUSTION ENGINE This invention relates to an afterburner for an internal combustion engine and, more particularly, to an afterburning system for minimizing hydrocarbon and carbon monoxide content left unburned in engine exhaust gases of an internal combustion engine.

Afterburners of the flame type have been used as furnaces that burn out the small quantities of fuel left unburned in the engine combustion chamber. In order to effect complete combustion of the unburned contents and therefore to discharge clean exhaust gases, the afterburners of the flame type establish an open flame in the contaminated exhaust gases by adding some amount of extra secondary fuel to the exhaust gases. In this direct open flame method, however, there are several concomitant problems: Since the afterburners are located in an engine exhaust pipe through which the exhaust gases flow at a high speed, it is quite difficult to stably maintain or hold the main combustion of the exhaust gases; furthermore, irregular combustions such as misfire or blow-off are often encountered in using the open flame method, thus inviting deterioration of the main combustion with resultant increased in unburned contaminated emission.

It is therefore an object of this invention to provide an afterburning system for an internal combustion engine including an improved afterburning stabilizer for forming a stable premixed flame to anchor the afterburning of the contaminated exhaust gases.

Another object of the invention is to provide an improved afterburning stabilizer including a porous enclosure for uniformly admixing an additional air-fuel mixture supplied thereto and a number of projections mounted upon the porous enclosure for producing small turbulences in the flow of the exhaust gases and for acting as a heat source when the premixed flame is formed closeto the tips thereof.

A further object is to provide a compact afterburning system with reliable ignition performance and without any misfire or blow-off.

In the accompanying drawings:

FIG. 1 is a diagrammatical flow chart of an afterburning system of the invention;

FIG. 2 is an explanatory view of the overall afterburning system;

FIG.3 is an enlarged sectional view of an embodiment of an afterburning stabilizer and afterburning reactor shown in FIG. 2; and

FIG. 4 is similar to FIG. 3 but shows another embodiment.

Referring now to FIG. 1, an afterburning system of this invention may be provided with a secondary air supplier 11 for supplying a secondary air to the contaminated engine exhaust gases 12 to produce exhaust gases 13, if desired. The exhaust gases 13 thus obtained are then introduced into an afterburning or reburning reactor 14 for complete consumption of the unburned content. After reburning the contaminated exhaust gases 12, the afterburning reactor 14 discharges clean exhaust gases 15.

According to a main feature of the invention, the reburning in the afterburning reactor 14 is stabilized by an afterburning stabilizer 16 which will be described in detail with reference to FIGS. 2 to 4. The afterburning stabilizer 16 of the flame type produces a premixed flame acting as a heat source for the reburning of the exhaust gases 13. Additional air-fuel mixture is supplied from an additional air-fuel mixture supplier 17 to form and maintain the premixed flame. As shown in FIG. 1, additional air 18 and additional fuel 19 are metered to have a proper mixture ratio and delivered to the additional air-fuel mixture supplier 17.

In order to effect complete combustion of the exhaust gases 13, the temperature in the afterburning reactor 14 is maintained at an appropriate level. This temperature control may be accomplished by providing a mixture flow rate controller 21 which controls the intensity of and therefore thermal energy generated by the premixed flame. For this purpose, the mixture flow rate controller 21 regulates flow rate of the additional air-fuel mixture 17 which has obtained a proper mixture ratio, in dependence upon the temperature in the afterburning reactor 14. The temperature detection is carried out by a temperature sensor 22 which may be mounted in the afterburning reactor 14. For initiation of the premixed flame, an igniter 23 may be used in the afterburning system 10.

More detailed description about the overall afterburning system 10 will be made with reference to FIG. 2, in which like numerals designate like elements and parts shown in FIG. 1. In this illustration of an embodiment, the afterburning stabilizer 16 is installed in a reburning chamber 14a defined by a housing 14b of the afterburning reactor 14. The afterburning stabilizer 16 has a generally spherical shape and is located upstream of the reburning chamber 14a.

The contaminated exhaust gases 12 are discharged from an internal combustion engine (not shown) into the reburning chamber 14a. As shown, a metered amount of secondary air 11 may be introduced into the contaminated exhaust gases 12 by an air injection device (not shown). The introduction of the secondary air 11 may preferably provide a partially admixed exhaust gases of proper mixture ratio falling to the lean side. On the other hand, the additional air 18 is sucked by a blower 18a through a passage 18b, which is vented to the surrounding atmosphere and is in communication with a reservoir 16a of the afterburning stabilizer 16. At the same time, an optimum amount of the additional fuel 19 is supplied in an atomized condition to the passage 18b by a carburetor 19a, which communicates with a fuel pump (not shown).

In operation, the additional air-fuel mixture 17 thus produced is uniformly admixed while passing through a porous enclosure 16b of the afterburning stabilizer 16. Then, the additional air-fuel mixture 17 produces the premixed flame when ignited by a spark plug 13a of the igniter 23. This premixed flame is encountered by the flow of the exhaust gases 13. In this instance, the exhaust gases 13 usually contain unburned fuel and may also contain the secondary air 1 1, so that they will easily reburn to consume the unburned fuel content if the reburning chamber 14a is maintained at a high temperature level. The combustion phenomena experienced in the reburning chamber 14a will be discussed in detail with reference to FIG. 3.

In order to control the temperature in the reburning chamber 140, the temperature sensor 22 senses the temperature level and provides a signal indicative of the temperature level. This signal is introduced into a controller 21a of the mixture flow rate controller 21. Upon reception of the temperature signal, the controller 21a energizes a servo-motor 21b to actuate the same. The servo-motor 21b, which is mechanically coupled with a throttle valve 210 mounted in the passage 18b, rotates the throttle valve 21c when actuated. This rotation changes the effective area around the throttle valve 210, thus controlling the flow rate of the additional air-fuel mixture 17. In this way, the temperature in the reburning chamber 14a is automatically controlled at a predetermined level appropriate for effecting therein complete combustion.

The controller 21a is energized by an energy source 24 through an ignition switch 25 and may control the operation of the blower 18a. The spark plug 23a may also be controlled by the controller 21a through switching of a high voltage source 23b.

Turning now to FIG. 3, the afterburning stabilizer 16 further includes a number of projections 16c mounted upon the porous enclosure 16b. These projections 16c may preferably be made of a heat resistive material and acts as a heat source for the main combustion when the premixed flame is formed therearound. This is because the projections 16c are heated by the premixed flame and then turns red-hot. In any event, the premixed flame is formed close to the tips of the projections 16c.

As is well known, the exhaust gases 13 is delivered at a relatively high speed into the reburning chamber 14a. At this instance, the porous enclosure 16b acts as a bluff body establising a wake and a recirculation zone, as shown, downstream thereof. Thus, the porous enclosure 16b as a whole is a flame holder as used in a jet engine. The projections 160, on the other hand, produce small turbulences in the stream of the exhaust gases 13. With the premixed flame thus formed, the combined effects of the small turbulences, wake, recirculation zone stably anchor the main afterburning combustion which is shown as a hatched reaction zone.

In this way, unstable irregular combustions such as a misflre or blow-off, which are otherwise inherent in the conventional afterburning system of the flame type, are absolutely eliminated with a resultant complete combustion. As an unexpected desirable result, the material used in the porous enclosure 16b may not have an extremely high heat-resistive property, because the additional air-fuel mixture 17 is cold enough to cool down the enclosure 16b while passing therethrough. Therefore, materials suitable for the porous enclosure 16b are, by way of example, sintered porcelain and multilayered stainless steel mesh. On the other hand, the projections 160 may be made of solid porcelain.

Reference is now to be made to FIG. 4 showing another example of an afterburning stabilizer 16', in which primed numerals indicate counterparts shown in FIG. 3. In this embodiment, a reburning chamber 14a and therefore an afterburning reactor 14 are provided within a porous enclosure 16'b of the afterburning stabilizer 16. A number of projections l6'c are mounted upon an inner surface of the porous enclosure l6'b. In this instance, a reservoir l6a is provided surrounding the porous enclosure 16b.

The additional air-fuel mixture 17 is, in operation, introduced into the reservoir l6a and passes inwardly throughthe porous enclosure 16'b. Then, the mixture 17 is ignited by the spark plug 230 and forms a premixed flame close to the tips of the projections 16"c.

At the same time, the exhaust gases 13 are ignited by lences, wake and recirculation zone are not expected to a great extentin this embodiment, a uniform high temperature distribution together with stagnant combustible gases are obtained in the reburning chamber l4'a, respectively because the reburning chamber 14'a is surrounded by the premixed flame and because the exhaust gases 13 are introduced into the reburning chamber 14a having a relatively large volume. This will lead to reduction of the amount of extra fuel to be added. The reburning chamber 14a is defined by the porous enclosure l6b being cooled, so that there will not be a cooling problem of the reburning chamber l4'a.

It should now be appreciated that this invention provides a compact afterburning system for reducing u'nburned content in the engine exhaust gases, with reliable ignition performance and without any misfire or blow-off.

What is claimed is: 1. An afterburning system for minimizing hydrocarbon and carbon monoxide contents left unburned in engine exhaust gases of an internal combustion engine, comprising:

reburning means having a reburning chamber for reburning the engine exhaust gases therein;

reburning stabilizing means including mixing means having a porous enclosure, and heat source and turbulence producing means having a number of projections mounted upon said enclosure, for forming a premixed flame close to the tips of said projections to stabilize the reburning of the engine exhaust gases; and

additional air-fuel mixture supplying means for supplying an additional air-fuel mixture to said reburning stabilizing means,

whereby said porous enclosure uniformly admixes said additional air-fuel mixture while it is passing therethrough, and said projections produce small turbulences in the flow of the engine exhaust gases and act as a heat source, while heated by said premixed flame, for anchoring the reburning of the engine exhaust gases.

2. An afterburning system according to claim 1, further comprising flow rate control means for controlling flow rate of said additional air-fuel mixture in dependence upon the temperature in said reburning chamber to maintain said temperature at a predetermined level appropriate for effecting complete combustion of the engine exhaust gases.

3. An afterburning system according to claim 2, wherein said flowrate control means includes a throttle valve rotatably mounted in said additional air-fuel mixture supplying means for controlling the effective area therearound, a servo-motor for rotating said throttle valve when energized, a controller for controlling energization of said servo-motor, and a temperature sensor mounted in said reburning chamber for sensing the temperature therein to control the operation of said controller.

4. An afterburning system according to claim 1, wherein said additional air-fuel mixture supplying means includes additional air supplying means for supplying fresh air to said reburning stabilizing means, and additional fuel supplying means for supplying an optimum amount of atomized fuel to the flow of the fresh air.

5. An afterburning system according to claim 4, wherein said additional air supplying means includes a passage vented to the atmosphere and communicating with said reburning stabilizing means, and a blower mounted in said passage for sucking the fresh air into said reburning stabilizing means, and wherein said additional fuel supplying means includes a carburetor mounted on said passage.

6. An afterburning system according to claim 1,

wherein said reburning stabilizing means has a generally spherical shape andis located within and upstream of said reburning chamber.

7. An afterburning system according to claim 6, wherein said projections and located externally of said porous enclosure.

8. An afterburning system according to claim 1, wherein the porous enclosure of said reburning stabilizing means defines said reburning chamber.

9. An afterburning system according to claim 8, wherein said projections are located internally of said porous enclosure.

10. An afterburning system according to claim 1, further comprising secondary air supplying means for supplying secondary air to the engine exhaust gases prior to the reburning operation to provide exhaust gases of proper mixture ratio.

Claims

1. An afterburning system for minimizing hydrocarbon and carbon monoxide contents left unburned in engine exhaust gases of an internal combustion engine, comprising: reburning means having a reburning chamber for reburning the engine exhaust gases therein; reburning stabilizing means including mixing means having a porous enclosure, and heat source and turbulence producing means having a number of projections mounted upon said enclosure, for forming a premixed flame close to the tips of said projections to stabilize the reburning of the engine exhaust gases; and additional air-fuel mixture supplying means for supplying an additional air-fuel mixture to said reburning stabilizing means, whereby said porous enclosure uniformly admixes said additional air-fuel mixture while it is passing therethrough, and said projections produce small turbulences in the flow of the engine exhaust gases and act as a heat source, while heated by said premixed flame, for anchoring the reburning of the engine exhaust gases.

3. An afterburning system according to claim 2, wherein said flow rate control means includes a throttle valve rotatably mounted in said additional air-fuel mixture supplying means for controlling the effective area therearound, a servo-motor for rotating said throttle valve when energized, a controller for controlling energization of said servo-motor, and a temperature sensor mounted in said reburning chamber for sensing the temperature therein to control the operation of said controller.

6. An afterburning system according to claim 1, wherein said reburning stabilizing means has a generally spherical shape and is located within and upstream of said reburning chamber.