JPH03229913A - Contact cleaning apparatus for exhaust gas of internal-combustion engine - Google Patents

Abstract

PURPOSE: To obtain high exhaust purifying performance, preventing thermal damage, by storing a porous inner tube molded corresponding to an outer covering tube and is cover with catalyst within the outer covering tube partially having an expansion chamber and demarcating an annular chamber of roughly constant cross section between both of the outer covering tube and the porous inner tubes. CONSTITUTION: An outer covering tube 1 which partially has an expansion chamber and is formed into an arbitrary shape and porous inner tube 3 stored in the outer covering tube 1 and molded corresponding to the outer covering tube 1 are provided. Between both of the outer covering tube 1 and the porous inner tube 3, an annular chamber 5 having roughly constant cross section is demarcated. In this inner tube 3, one surface or both the surfaces are covered with exhaust gas purifying catalyst. The rate of an inner diameter of the outer covering tube 1: an outer diameter of the inner tube 3 is set to the range of 1.01 to 1.20. A porous hole provided on the inner tube 3 is formed as expansion of upward and/or downward deep drawing and the inner tube 3 is constituted of two half shells which are joined each other as occasion.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a catalytic cleaning device for exhaust gas from internal combustion engines, particularly two-cycle engines.

BACKGROUND OF THE INVENTION BACKGROUND OF THE INVENTION BACKGROUND OF THE INVENTION BACKGROUND OF THE INVENTION Internal combustion engines, in particular those based on the two-cycle principle, require a specific configuration of the exhaust gas guide for an advantageous development of gas conversion processes (fresh gas filling, scavenging and exhaust gas discharge processes). For this purpose, a suitable adjustment of the muffler as well as specific structural measures in the area between the exhaust gas outlet of the engine and the muffler play an important role. For example, reflective surfaces and/or expansion chambers (so-called exhaust converters) are therefore provided in or immediately after the exhaust bend in order to advantageously influence the gas movement.

Conventional catalytic exhaust gas cleaning devices, such as packed-bed catalysts or integrated catalysts (which usually have to be placed in the exhaust system in the area close to the internal combustion engine), in the case of vehicles with a two-cycle engine, are capable of cleaning the exhaust gases caused by the engine. It has been found that performance is reduced due to disturbances such as exhaust gas backpressure and vibrations due to gas movement.

Blockage due to oil return may also occur. This sometimes occurs under certain operating conditions of internal combustion engines, for example in the case of integral catalysts. Conventional monolithic catalysts have generally proved to be disadvantageous, since such catalysts have extremely high conversion potentials in large-displacement internal combustion engines; exposed to fever;
The risk of thermal damage therefore ensues and eventually the catalyst melts.

OBJECTS TO BE SOLVED BY THE INVENTION An object of the present invention is to provide a catalytic exhaust gas cleaning device that is better suited for internal combustion engines as described above.

Means for Solving the Problems The above object is achieved by providing a contact cleaning device for exhaust gas of an internal combustion engine according to the present invention, which includes: a jacket pipe forming an expansion chamber, which is optionally arranged as a part of an exhaust pipe or in the exhaust pipe; and a porous inner tube located inside the jacket tube, separated from the intermediate tube, and optionally corresponding to the shape of the jacket tube, and coated on one or both sides with an exhaust gas purification catalyst. at least one bridge spaced between the outer tube and the inner tube and connected to both tubes forms an annular chamber which may be interrupted by a projection or bead in the inner tube; and the ratio of the inner diameter of the jacket tube to the outer diameter of the inner tube is 1.01~
solved by said device, characterized in that it lies in the range given by 1°20.

The device according to the invention is also suitable in the case of four-stroke engines, since fine adjustment of the exhaust system is also necessary in the case of these engines. The jacket tube 1 may be shaped arbitrarily. The inner tube 3 is shaped to correspond to the tube 1, resulting in an annular tube 5 with a vague cross section. A tapered annular chamber is also a component of the invention.

The annular tube 5 utilizes only a portion of the volume of the jacket tube I due to predetermined dimensions. The annular tube 5 and the pores enhance the turbulence and thus the gas exchange in the catalytic region. This effect is enhanced in the basic design of the 7 device according to the invention by an annular gap that is open on both sides and ensures a backward flow of the catalyst-coated inner tube. For many engine designs, it is advantageous to close the annular chamber at any position on at least one side.

In the case of circular holes as porous holes, the pore diameter of the inner tube is 0-75
-10+++ m, the hole spacing being 1.0-15 mm. Preferably the pore diameter is 1.5-6 mm and the pore spacing is 2.0-7.5 mm. The inner tube has pores of various pore sizes arranged regularly with respect to each other over its entire outer shell.

Further, in addition to circular holes, rectangular holes, slit holes, holes of arbitrary shapes, and these holes can also be used. Similarly, the size or number of holes can vary over the length of the inner tube. Optionally, the tube body may also consist of rolled metal or coarse wire mesh.

The relative pore area (total pore area) is in various embodiments from 5 to 80%, preferably from 20 to 60%.

The pores in the inner tube, which act as turbulent fluid, are directed upward and/or
Or they can be enhanced in their effectiveness by being present as downward deep-drawn bulges.

The inner tube may optionally consist of two half-shells, which are optionally connected to each other, especially for reasons of manufacturing technology. It is therefore also possible to divide the annular chamber into two halves.

The geometric surface of the inner tube may be increased by surrounding it with wire mesh, rolled metal or other perforated tubes to increase the conversion rate of hazardous substances.

The device according to the invention is suitable as a pre-catalyst and starter catalyst for a subsequent main catalyst 6 of any design. By using it as a starter catalyst, a temperature increase occurs due to partial conversion of pollutants, which facilitates or even for the first time makes possible the starting of the main catalyst, which is optionally followed by a relatively cold part of the exhaust gas system. When high pollutant concentrations occur and at the same time the exhaust gas temperature increases, partial conversion reduces the temperature load because of the exhaust gas cooling that takes place between the starting catalyst and the main catalyst and allows the main catalyst to open earlier. This has an advantageous effect insofar as it protects it from destruction or thermal deactivation. The conversion according to the invention is surprisingly high when used as a precatalyst, as the Pope example shows. In addition, when used as a precatalyst, when installed in a two-wheeled vehicle, it is possible to meet the limits already in use today and the limits that will come in the future.

As catalysts it is possible to use all the customary formulations known from the exhaust gas cleaning of Otto engines, which contain noble and/or base metals.

In particular, refractory oxide support materials (Al2203, S +0
2, Pt, Pd and/or R on aluminum silicate)
H-containing noble metal catalysts are preferred. The support material may be provided with oxide additives, ie CeO2, ZrO2, alkaline earth metal oxides and/or rare earth oxides, for activation and improved thermal stability.

Optionally, before using the oxide support material, a pretreatment is carried out by sandblasting, thermal spraying, aluminization to improve the heat resistance of the porous tube and the adhesion of the coating.

Example l Diameter 30+n+++ and 55 mm 1 elongated tube length 34
A tapered, perforated curved tube made of high-temperature steel 1.4841 with a diameter of 5 mm, a hole diameter of 2 m+++ and a hole spacing of 3.15 mm is first heat treated with air at 900° C. for 3 hours.

Next, γ-AQ203 (150m2/g),
An approximately 40% dispersion of cerium acetate and zirconyl acetate is applied, dried at 120°C and calcined at 600°C for 2 hours. Coating amount is Al2O37.5g per part
, 22 g of CeO and 20.5 g of ZrO. Next, Pt(Nl-I3)4(OH)2 and R
h(NO3)3 solution (Pt:Rh weight ratio = 5:l
), dry it and form gas (N2:H2
= 95:5) at 400°C. The noble metal loading is 0.24 g/part.

Example 2 The catalyst described in Example 1 was tested in the experimental setup of FIG. The annular gap between the outer diameter of the inner tube and the inner diameter of the outer tube is 1 mm.
Met. As a mounting body for the experimental equipment, the stroke volume is 148
A two-wheeled vehicle equipped with a cm3 air-cooled two-stroke cylinder engine was used. The output of the two-wheeled vehicle is the rated rotational speed of 810
The power was 14kW at 0 min-”.Oil/benzine (1:
50) was used.

For the vehicle, test regulations ECE with a roller type dynamometer
Measurement was performed using R40. The exhaust gas temperature at the inlet of the catalyst varied during the test cycle from 250 to 650°C.

Exhaust gas analysis was performed using the CVS principle.

The following emissions were measured: 0 Co T (C+NOxg/km
g/km Without catalyst 3.25 5.86 With catalyst
1,13 2.56 Therefore, the conversion rate is CO
In the case of (HC+N0x), it is 68%, and in the case of (HC+N0x), it is 56%.

By using such a specifically formed catalyst, the limit value CC0 = 8.0 g accepted in Switzerland can be achieved.
/km x HC + N0x = 3.1 g/km) without causing significant damage to the gas movement process, which would lead to a reduction in the power output of the two-cycle engine.

Example 3 Made of heat-resistant steel 1.4828 with a thickness of 1 mm and a diameter of 3
Adhesive coarse oxide layer based on A4203 on tapered tubes of 9 mm and 61 mm, length 150 m+++, with slit holes (hole width 1-1-51R hole length 5 mm, bridge width 1.3 mm) Cover. The metal tube thus pretreated was immersed in a 42% suspension of La2O3 stabilized γ1 AQ203 (130 m2/g) and cerium oxide, the excess coating material was removed by Suita, and dried for 500 m2/g. Heat treatment for 2 hours at °C. After coating, Aff2033.9g and La2O were placed on the tube.
30.2g and Ce021,Og were present.

This catalyst precursor is then added to Pt(NH3)2(NO2).
2 and Pd(NO3)2 (Pt: pd weight ratio -
2=1), the material is dried and calcined in air at 300°C. The amount of precious metal is 125m
g/part.

Example 4 The catalyst described in Example 3 was tested in the experimental setup illustrated in FIG. The annular gap between the outer diameter of the inner tube and the inner diameter of the outer tube was 1.5 mm on average. As a mounting body for experimental equipment,
A two-wheeled vehicle equipped with an air-cooled two-stroke cylinder engine with a stroke volume of 134 cm3 was used. The output of the engine is
The power output was 12 kW at a rated rotational speed of 8100 m1n-1. An oil/benzine (1:30) mixture was used.

2 For the vehicle, test regulations ECE with a roller type dynamometer.
Measurement was performed using R40. The exhaust gas temperature at the inlet of the catalyst was 150-420°C. Exhaust gas analysis was performed using the CVS principle. The following emissions were measured: Co HCN0x y /km g/km g/km without catalyst
6.86 10.15 0.016 with catalyst 3
．． 16 5.96 0.014 Therefore, the conversion rate is
53% for CO, 41% for HC, NOx
The percentage was 13%.

By using such a specifically formed catalyst, the limit values (c) prevailing in Austria can be achieved in the case of two-cycle motorcycles.

= 8g/km, HC= 7.5g/km 5NO
x=0.

1g/km).

Example 5 A monolithic metal support with a diameter BO mm, a length 75 mm and a cell density of 31 cells/cm2 was coated by immersion in an aqueous suspension consisting of γ]3 AQ203, cerium acetate and zirconyl acetate. , excess application material is removed by blowing. After drying at 120°C and baking at 700°C for 1 hour, AQ20
325g, CeO25g and Zr021g are present. This catalyst precursor is then added to pt(NH3)4(○H
)2 and Rh(NO3)3 and dry the material at 300°C. Pt: R on the catalyst after coating
There was present 0.36 g of noble metal in a weight ratio of -5:l.

Example 6 The catalysts according to Examples 3 and 5 are installed in the exhaust port of a two-cycle motorcycle using the apparatus shown in FIG. The test is carried out analogously to Example 4.

The following emissions were measured: Co HCNOx g/km y /km g/km without catalyst
6.86 10.15 0.016 with catalyst
1.10 1,45 0.0144 4 Compared to Example 4, the nitrogen oxide emissions are approximately the same, but a clearly increased conversion of 84% for CO and 86% for HC is obtained. It was done. Therefore, such a concept is suitable when trying to satisfy very strict future limit values.

If only the catalyst according to Example 5 is used in a device according to Example 3, it is not possible to obtain high conversion rates, since without the taper precatalyst the temperature level is too low.

If the catalyst according to Example 5 were to be installed close to the engine in the area of the precatalyst (FIG. 3), such a concept would not be suitable, since this would lead to disturbances in the gas movement process and thus to unacceptable power losses.

[Brief explanation of drawings]

1 to 3 are schematic longitudinal cross-sectional views of embodiments of the device of the present invention: ■...Outer tube, 2...Catalyst, 3...Inner tube, 4...
・Buri 5

Claims (1)

[Claims] 1. In a contact cleaning device for exhaust gas of an internal combustion engine, a jacket pipe (1) forming an expansion chamber, which is optionally arranged in a part of an exhaust pipe or in the exhaust pipe; and a jacket pipe (1) forming an expansion chamber; Inside the tube, it has a porous inner tube (3) arranged at a distance from the tube, optionally corresponding to the shape of the jacket tube, and coated on one or both sides with an exhaust gas purification catalyst. ; at least one tube spaced between the outer tube and the inner tube and connected to both tubes;
The bridges (4) form an annular chamber (5) which may be interrupted by projections or beads in the inner tube, and the ratio of the inner diameter of the jacket tube to the outer diameter of the inner tube is 1.0.
A contact cleaning device for exhaust gas of an internal combustion engine, characterized in that the contact cleaning device exists in the range given by 1 to 1.20. 2. The annular chamber (5) is at any position on at least one side,
2. The device according to claim 1, wherein the device is closed by enlarging the inner tube end or by welding or soldering. 3. The device according to claim 1 or 2, wherein the pores are present as upwardly and/or downwardly directed deep-drawn bulges. 4. Device according to claim 1, wherein the inner tube (3) consists of two half-shells, optionally connected to each other. 5. The device as claimed in claim 1, wherein the inner tube (3) is forcibly surrounded by a wire mesh, rolled metal or other perforated tube which is also coated with a catalyst. 6. Any one of claims 1 to 5, optionally connected as a preliminary catalyst before the integrated main catalyst (6).
Apparatus described in section. 7. The device according to any one of claims 1 to 6, wherein the pores are present as circular pores with a pore diameter of 0.75 to 10. 8. The device according to any one of claims 1 to 7, wherein the total pore area is 5 to 80%.