AU1168092A

AU1168092A - Exhaust gas purifying device for an internal combustion engine

Info

Publication number: AU1168092A
Application number: AU11680/92A
Authority: AU
Inventors: Saverio Megna
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-05-13
Filing date: 1992-01-16
Publication date: 1992-12-30
Also published as: ITMI911305A1; EP0587564A1; IT1254054B; JPH06511059A; WO1992020910A1; CA2102917A1; ITMI911305A0

Description

DESCRIPTION

EXHAUST GAS PURIFYING DEVICE FOR AN INTERNAL COMBUSTION ENGINE

The present invention relates to an exhaust gas purifying device for an internal combustion engine.

It is known that the control of each type of gas emission in general is becoming increasingly more important as well as in particular, above all in big towns, the reduction of the noxious components present in the exhaust gases of motor-vehicle engines.

Presently this reduction is preferably accomplished byapplying catalytic scrubbers, commercially referred to as catalytic mufflers, to the exhaust pipes of motor-vehicles. The results hitherto achieved in motor-vehicles using petrol engines have been particularly encouraging, because they have allowed some of the most noxious components of the exhaust gases, such as carbon monoxide and nitrogen and sulfur oxides to be drastically reduced.

However, it should be noted that when the exhaust gases pass through the catalytic muffler, they tend to "poison" it, that is to clog it thereby reducing the catalytic properties thereof. As a result, it is necessary to replace the whole catalytic unit rather frequently, depending on how often the vehicle is used, which involves high costs.

One of the components that greatly tend to clog the catalytic scrubber is represented by the solid particles forming the combustion fumes, referred to as "particulate matter" by those skilled in the field.

These particles are present to a great extent not only in vehicles provided with diesel engines where they are visible to the naked eye due to the very dark coloration they have, but also in vehicles driven by petrol engines where the discharged fumes are less visible.

These solid particles lay down on the catalytic unit generally consisting of a catalyst placed on a porous support and clog it in a short period of time, thereby preventing it from coming into contact with the noxious gases to be purified. As a result, since it is above all the most upstream portion of the catalytic unit, as viewed in the direction of the gas flow, that is "poisoned", that is clogged by the particulate matter, it is necessary to foresee a catalytic mass of important sizes in order to be able to spread the solid particles over a wider volume and therefore prolong the lifetime of the catalytic unit.

This problem is more present in vehicles provided with diesel engines due to the greater amount of particulate matter produced by combustion, so that the application of catalytic scrubbers to this type of vehicles has been hitherto substantially negligible. At all events, every type of catalytic scrubber used in combination with a diesel engine would have a lower lifetime than if used in combination with a petrol engine. Under this situation the technical task underlying the present invention is to provide an exhaust gas purifying device capable of substantially eliminating the above drawbacks. Within the scope of this technical task it is an important object of the invention to provide an exhaust gas purifying device capable of substantially reducing the smokiness of the exhaust gases in internal combustion engines.

Another inportant object of the invention is to provide a purifying device permitting the lifetime of the catalytic scrubber to be greatly increased both when applied to diesel engines and when applied to petrol engines while at the same time reducing the mass of the employed catalyst, thereby achieving an important reduction both in the management and installation costs of the catalytic scrubber.

The technical task mentioned and the aims specified are substantially achieved by an exhaust gas purifying device for an internal combustion engine, characterised in that it comprises: an outer casing exhibiting an inlet and an outlet for the passage of said exhaust gases, and at least a filtering portion disposed within said outer casing between said inlet and outlet and adapted to retain the solid particles produced by combustion and present in said exhaust gases.

Two preferred embodiments of an exhaust gas purifying device in accordance with the invention for an internal combustion engine will be given hereinafter by way of non-limiting example with reference to the accompanying drawings, in which:

- Fig. 1 is a longitudinal sectional view of an exhaust gas purifying device in accordance with one embodiment of the invention;

- Fig. 2 is a longitudinal sectional view of a second embodiment of the purifying device in question.

Referring to the drawings, the exhaust gas purifying device in accordance with the invention has been generally identified by reference numeral 1.

It comprises an outer casing 2 inserted between an inlet 3 and an outlet 4 of an upstream section 5 and a downstream section 6 respectively of an exhaust pipe for the gases coming from an engine. The outer casing 2 is comprised of a body 2a and a closing cover 2b.

Advantageously the downstream section 6 of the exhaust pipe is in turn fitted in a catalytic scrubber or catalytic muffler 7. The latter can be positioned as shown in Fig. 1 on the longitudinal extension of the device 1 or, as shown in Fig. 2, alongside the latter, but still in succession thereto relative to the flow direction of the exhaust gases.

Provided between the inlet 3 and outlef 4, within the outer casing 2, are two filtering portions consisting of one filtering portion 8a and a second filtering portion 8b coaxial with each other and preferably exhibiting a substantially cylindrical hollow shape.

In greater detail the first filtering portion Sa has an entry wall 10a formed with a perforated plate defining a cylindrical cavity 11 in which a given length of the upstream section 5 of the exhaust pipe is fitted. Arranged in the cylindrical cavity 11 is a deflecting means 12 adapted to centrifuge the exhaust gases entering the device 1 and defining a sheet spiral substantially in the form of an Archimedean screw. The sheet spiral 12 is integral with a tie-rod member 13 both ends of which, 13a and 13b, are threaded. The first end 13a engages in a bored support 14, introduced into the end portion of the upstream section 5 of the exhaust pipe.

The second end 13b emerges from the outer casing 2 at the cover 2b and can be engaged by a wing nut 15 adapted to keep the cover associated with the body 2a of the outer casing 2.

The first filtering portion 8a has one exit wall 16a for the exhaust gas made of perforated plate too in which the holes are formed by cutting and subsequent stretching of the plate itself. Disposed between the exit wall 16a and entry wall 10a is a first filler 17a which is permeable to the exhaust gases and adapted to hold by filtering the solid particles produced by combustion and known as "particulate matter", which substantially consist of carbonaceous residual products present in the exhaust gases.

Likewise, the second filtering portion 8b disposed coaxially with, and externally of the first filtering portion 8a, exhibits a second entry wall 19b and a second exit wall 16b formed with perforated plate, in particular of the expanded metal type. The diameter of the cylindrical surface defined by the second entry wall 10b is greater than the diameter of the cylindrical surface defined by the first exit wall 16a so that an empty area 18 is included therebetween which is reached by burnt gases having lost part of their velocity.

The perforated metal plates 10a and 16a, 10b and 16b have respective passage openings the sizes of which decrease in the flow direction of the gas, that is decreasing sizes are provided between subsequent filtering portions and, in each filtering portion, between the entry wall and exit wall.

The second filtering portion 8b too has inside it a second filler 17b adapted to retain the unburned solid particles. More particularly, the fillers 17a and 17b are of the granular type and exhibit grains of decreasing sizes between filtering portions. in succession. In this way the first filtering portion 8a is adapted to stop particles of great size and the second filtering portion 8b can retain finer particles.

Advantageously, for applications to diesel engines, the fillers 17a and 17b preferably consist of quicklime exhibiting the above mentioned granulometric features for each filtering portion.

On the contrary, for applications to petrol engines, the fillers preferably consist of a mixture made of quicklime and granular paper from Russian pine having the above discussed granulometric features in connection with each portion.

Provided between the second outer wall 16 and the outer casing 2 is a chamber 19 for passage of the burnt and filtered gases; said chamber becomes larger close to the outlet 4. Shaped plates 20a and 20b are integral with the cover 2b and they close the cilindrical cavity 11 at the end, and the passage chamber 19 at the tie-rod member 13.

Referring particularly to Fig. 2, the embodiment of the purifying device shown therein differs from that seen in Fig. 1 exclusively in that the catalytic unit is disposed in side by side relation with the filter. This is done for reducing the bulkiness relative to the sizes and structure of the vehicle to which said unit is to be mounted.

Operation of the exhaust gas purifying device described above mainly as regards structure, is as follows. The exhaust gases, after passing the inlet 3 are set in rotatory motion by the sheet spiral 12 so that the solid particles contained therein are sent with violence by centrifugal force against the first filtering portion 8a. In this filtering portion the retention of particles of greater sizes occurs, whereas those of smaller sizes are stopped in the following filtering portion 8b. It is pointed out that the filtering material that is originally used, that is quicklime of differentiated granulometry in the two filtering portions 8a and 8b, is specifically efficient in filtering the particulate matter contained in the exhaust gases from internal combustion engines and above all from diesel engines. Therefore the exhaust gasses discharged from the outlet 4 have a greatly reduced smokiness.

From tests carried out on the exhaust gases from the diesel motor of a van through opacimeters of the approved type in accordance with the Italian law it has been found that the addition of the device of the invention has allowed the average opacity value to be reduced by about 50%. In fact an average value of m% and an average value of 85% have been measured respectively on a vehicle provided with the inventive device and on the same vehicle devoid of said device.

Tests have also been carried out on a petrol motorvehicle devoid of the catalytic muffler in order to evaluate the emission amounts with the use of the device of the invention and without its use. The results supplied by the measuring apparatus keeping the engine to a constant speed of 3000 revolutions per minute have shown an important reduction in the amounts of nitrogen and sulfur oxides contained in the exhaust gases as well as a reduction as high as 50% in the contents of carbon monoxide.

Where necessary, it is possible to withdraw the filtering portions 8a and 8b from the outer casing 2 by acting on the wing nut 15 and separating the removable part 2b and the shaped plates 20a and 20b from the main body 2a. In this way the filtering portions 8a and 8b can be easily cleaned and replaced.

The invention puts into practice a new process being part of the present patent application too. In accordance with said process the combination of two seeps is provided which consist in previously subjecting the exhaust gases to a mechanical filtering in order to retain the solid particles resulting from combustion and present therein and subsequently submitting the previously filtered exhaust gases to catalytic purification.

The invention achieves important advantages.

In fact, not only the purifying device of the invention, if used individually, permits an important reduction in the smokiness and noxious emissions of the exhaust gases to be achieved with a reduced additional bulkiness, but also, if used in combination with a catalytic muffler, enables an important improvement in the operation of said catalytic muffler. In fact, the catalytic mufflers are clogged or "poisoned" by the exhaust gases in a much longer time and consequently can be planned so as to have a reduced catalyst mass and a smaller bulkiness, reduced by 50% for example. Consequently also important advantages as regards both servicing and installation are achieved by the use of a catalytic purifier associated with the device of the invention.

But, above all, a still more drastic reduction of the noxious gases coming out of a catalytic muffler is achieved because the catalyst can operate at its best capacities while maintaining good cleanness conditions over all its lifetime.

It will be finally recognized that the particular embodiment shown is advantageous also as regards its most specific aspects.

Modifications and variations may be made to the invention as conceived, all of them falling within the scope of the inventive idea. In addition, all of the details may be replaced by technically equivalent elements.

Claims

C L A I M S

1. An exhaust gas purifying device for an internal combustion engine characterized in that it comprises an outer casing (2) exhibiting an inlet (3) and an' outlet (4) for the passage of said exhaust gases and at least a filtering portion (8a, 8b) disposed internally of said outer casing (2) between said inlet (3) and outlet (4) and adapted to retain the solid particles produced by combustion and present in said exhaust gases.

2. A device according to claim 1, characterized in that said outer casing (2) is fitted between two lengths (5, 6) of an exhaust pipe comprising a catalytic scrubber (7) downstream of said outer casing.

3. A device according to claim 1, characterized in that provision is made for a plurality of said filtering portions (8a, 8b) disposed in succession between said inlet (3) and outlet (4) and adapted to retain said particles of decreasing sizes in the flow direction of said exhaust gases.

4. A device according to claim 1, characterized in that a deflecting means (12) adapted to centrifuge said exhaust gases is provided upstream of said at least one filtering portion (8a, 8b) and after said inlet (3).

5. A device accord ing to claim 4, character ized in that an empty area (18) for the passage of said exhaust gases is provided between a filtering portion (8a) and the following one (8b).

6. A device according to claim 1, characterized in that said filtering portion (8a, 8b) externally consists of walls made of perforated metal plate (10a, 16a, 10b, 16b) and internally consists of a filler (17a, 17b) permeable to the exhaust gases.

7. A device according to claim 6, characterized in that said filler (17a, 17b) is of the granular type and exhibits grains having decreasing average sizes in successive filtering portions (8a, 8b).

8. A device according to claim 6, characterized in that said filler (17a, 17b) substantially consists of quicklime.

9. A device according to claim 6, characterized in that said filler (17a, 17b) substantially consists of a mixture made of quicklime and granular paper from Russian pine.

10. A device according to claim 6, characterized in that said perforated metal plates (10a, 16a, 10b, 16b) exhibit passage holes having decreasing sizes in successive filtering portions (8a, 8b) and, in each filtering portion (8a, 8b), between the entry wall (10a, 10b) and the exit wall (16a, 16b) of said exhaust gases.

11. A device according to claim 9, characterized in that said perforated metal plates (10a, 10b, 16a, 16b) are at least partly obtained from previously cut and subsequently stretched plates.

12. A device according to claim 5, characterized in that said filtering portions (8a, 8b) substantially have the shape of a hollow cylinder and are coaxial with each other, and in that said empty area (18) is included between the outer surface of one of said filtering portions (8a) and the inner surface of the following filtering portion (8b) and said deflecting means (12) is inserted in a cylindrical cavity (11) defined by the inner surface of the filtering portion (8a) disposed immediately downstream of said inlet (3).

A device according to claim 11, characterized in that said deflecting means (12) is defined by a sheet spiral substantially in the form of an Archimedean screw.

14. A device according to claim 1, characterized in that said outer casing (2) consists of a body (2a) housing said filtering portion (8a, 8b) and a removable closing cover (8b) enabling said filtering portion (8a, 8b) to be withdrawn.

15. A device according to claim 13, characterized in that said closing cover (2b) is maintained in association with said main body (2a) by a partly threaded tie-rod member (13) and a wing nut (15) designed to be screwed on said tie-rod member (13).

16. A process, for purifying the exhaust gases from an internal combustion engine, characterized in that it comprises the steps of:

- previously subjecting the exhaust gases to mechanical filtering in order to retain the solid particles resulting from combustion and present therein; and

- subsequently submitting the previously filtered exhaust gases to catalytic purification.