DE2635725A1 - EXHAUST GAS REACTION DEVICE FOR A COMBUSTION ENGINE - Google Patents

Description

Patent attorneys Dipl.-Ing. H.Weickmann, Dipl.-Phys. Dr. K. Fincke

Dipl.-Ing. R A. ¥ eickmann, Dipl.-Chem. B. Huber

8 MUNICH 86, POST BOX 860 820 SbT

MÖHLSTRASSE 22, CALL NUMBER 98 39 21/22

HONDA GIKEN KOGYO KABUSHIKI KAISHA,

27-8, 6-chome, Jingumae, Shibuya-ku,

Tokyo, 150 Japan

Exhaust gas reaction device for an internal combustion engine

The invention relates to an exhaust gas reaction device for an internal combustion engine which is to be mounted in the exhaust gas duct and with which the release of unburned hydrocarbons (HC) into the atmosphere can be minimized.

The invention is explained below with reference to a two-stroke piston internal combustion engine described, but this is not intended to limit the basic concept of the invention in any way. The problem of exhaust gas cleaning occurs in two-stroke engines particularly in appearance as part of the fresh air-fuel mixture introduced into the combustion chamber exits through the exhaust opening with the burned gases from the previous work cycle. The problem, the unburned

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Keeping the hydrocarbons in the exhaust to a minimum also occurs in four-stroke engines, as this occurs with every working cycle a so-called valve overlap occurs when the inlet valve and the outlet valve open at the same time are.

An exhaust gas reaction device for an internal combustion engine is characterized according to the invention by an elongated, Heat-resistant arrangement to be installed in the exhaust gas duct, made up of several longitudinally extending, through mutually parallel, mutually contacting walls formed channels running the entire length of the reaction device run and the walls of which are thin in relation to the channel width.

When the exhaust gas reaction device is used in an internal combustion engine, it is preferably as close as possible the exhaust port and isolated from the machine body and the exhaust pipe, so that the burned gases Remain sufficiently hot in it and ignite the non-dispersed, unburned fuel-air mixture. The cross section each of the mutually parallel channels is so small that the mixture flowing through it is not dispersed in the reaction device during the burning period. The canal walls are burned by the Gases are heated and warm and in turn ignite the unburned mixture flowing through them. The cross section the reaction device is larger than that of the exhaust port in order to keep back pressure to a minimum. The flow of burned exhaust gases and unburned mixture fractions is not homogeneous and it is necessary to have a To prevent dispersion of the unburned mixture flowing through within the flow of burned exhaust gases,

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with the HC emissions are reduced. By minimal Dispersion of unburned mixture, the HC emissions are reduced because at the same reaction temperature and at the same residence time in the reaction device, higher fuel concentrations burn better than by dispersion decreased. The construction of a reaction device according to the invention is generated in the form of multiple channels the desired result as the undesirable dispersion is prevented.

Embodiments of the invention are described below with reference to the figures. Show it:

1 shows the section of a two-stroke engine with a reaction device according to the invention,

FIG. 2 shows a part of the device according to FIG. 1 on an enlarged scale,

Fig. 3 the section 3-3 according to Fig. 2,

4 shows a part of the device according to FIG. 3 on an enlarged scale,

5 shows the section 5-5 according to FIG. 2, FIG. 6 shows the section 6-6 according to FIG. 2,

7 shows another embodiment of a reaction device ,

8 shows a further embodiment of a reaction device,

9 shows a third embodiment of a reaction device,

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10 is a graph showing the relationship between the distance L of the exhaust port and the reaction device and the percentage reduction of HC in the discharged exhaust gases for reaction channels with three different cross-sections,

11 is a graph showing the relationship between the length χ of the reaction device and the percentage reduction of HC for three channels of the reaction device with different cross-sections,

Fig. 12 is a graph showing the relationship between the cross-section a of each reaction channel and the percentage reduction from HC for a distance L of 20 mm and a length χ between 30 and 100 mm,

Figures 13, 14 and 15 are diagrams of the motion supplied Fuel-air mixture and the movement of the exhaust gases from the combustion chamber when the piston moves to bottom dead center and subsequent upward movement,

Figure 16 is a graph of the flow rate burned exhaust gases and unburned mixture for piston positions near bottom dead center and

17 is a graph showing the concentration of unburned hydrocarbons as a function of of the piston position during the exhaust stroke of a four-stroke internal combustion engine.

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In the figures, a two-stroke internal combustion engine 10 with an engine block 11, a cylinder head 12 and a Crankcase 13 is shown. The machine is denoted by 14 as a whole. A piston 15 is within a cylinder wall 16 and a cylinder head 12 and forms with this a combustion chamber 17. A spark plug 18 is fastened in the cylinder head 12.

When the machine is in operation, a fuel-air mixture generated by a carburetor (not shown) is passed through an inlet opening 21 into a space 22 within the Crankcase 13 sucked in and when the downward movement of the Piston 15 compressed. An overflow channel, not shown runs from the space 22 to an overflow opening in the cylinder wall 16. When the piston is in the cylinder moved upwards, the fuel-air mixture delivered through the overflow opening 23 from the space 22 is compressed and ignited by the spark plug 18. The piston 15 is driven by the force of the burning and expanding gases driven downwards. These gases are discharged through an exhaust port 24 in the cylinder wall 16 and pass through an exhaust duct 25 in the engine block 11.

A multi-channel reaction device 26 is shown in FIG the exhaust duct 25 is arranged near the exhaust port 24, so that the exhaust gases discharged from the combustion chamber 17 pass through the reaction device 26 before entering an exhaust pipe 29. As can be seen from Fig. 2 to 6, The reaction device 26 comprises a unitary structure with a plurality of elongated channels 27 running parallel extend to each other and are formed by thin walls 28 which are in mutual lateral contact and over the entire length of the reaction device 26 get lost. In the embodiment shown in FIG

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form a smooth spiral curved wall 28a and a corrugated spiral wall 28b parallel channels. The two walls 28a and 28b are arranged in a cylindrical cartridge 30. This has a bore 31 which the exhaust duct 25 continues. Radially extending pins 32 protrude from the cartridge 30 into the bore 31 and anchor the outer part of the spiral structure against rotational movement. The inside 33 of the spiral structure from the walls 28a and 28b can move freely by thermal expansion forces. The thin walls 28a and 28b are made preferably made of a heat-resistant metal, preferably their thickness is approx. 0.2 to 0.4 mm, but walls were also used used with a thickness of 0.1 to 1 mm. The walls are thin compared to the width of the channels 27.

The spiral structure is axial within the cartridge 30 Direction held, including a front holder 34 and a rear holder 40 are provided. The front bracket 34 (Fig. 5) is an annular member with a plurality of radially outwardly projecting tabs 35 which engage in corresponding recesses 36 in the front end of the cartridge 30. The front holder 34 also has two arms 38 which are diametrically opposed to each other and form a slot 39 between them, which allows thermal expansion. The rear holder 40 (Fig. 6) is integrally formed on the cartridge 30 and provided with arms 41 which are diametrically opposed to each other and between a slot 42 is formed.

The reaction device 26 is arranged within a bore 45 of the machine block 11, so that a distance 44 is provided between the bore 45 on the outer periphery of the cartridge 30 to the heat transfer from the cartridge 30 to the Machine block 11 to prevent. The cartridge 30 is equipped with a

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nem integral flange 46 provided. Threaded fasteners 47 protrude through this flange 46 and through an insulating seal 48 into threaded openings in the machine block The cartridge 30 is held in this way on the machine block 11, but is thermally insulated from it.

The exhaust pipe 29 has an end fitting 50 which surrounds a sleeve 51 which is provided on the cartridge 30. A spring ring 52 and an insulating ring 53 prevent gas leakage and keep the transfer of heat at the connection point between the cartridge 30 and the exhaust pipe is minimal. Coil springs 54 hold parts 50 and 51 together. They have one open end 55 which is fastened to the machine body by means of a bracket 56, the other End 57 of each spring 54 is fastened relative to the exhaust pipe by means of a bracket 58. The connection between the exhaust pipe 29 and the cartridge 30 allow movement of the parts relative to each other by vibration forces can be caused.

As is apparent from the graph of Fig. 10, the percentage of decrease in HC in the Exhaust gases are greatest when the distance L between the exhaust gas opening 24 and the reaction device 26 is as small as possible is. The illustration shows that the distance L should not be greater than approx. 110 mm, regardless of the cross section a, the

2 respective channels 27.Thus, cross sections of 7 mm show

2 2

20mm and 50mm each a relatively minor improvement, when the distance L increases, since the burned gases are fairly cooled and the unburned air-fuel flow is dispersed.

From the graphic representation according to FIG. 11 it can be seen

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nen that the percentage reduction of HC in the exhaust gases is dependent on the length χ of the reaction device 26.

2 There are three curves for duct cross-sections of 7 mm, 20 mm

ρ
and 50 mm. The distance L from the exhaust gas opening 24 to the reaction device 26 is 20 mm in all cases. The illustration shows that the greatest reduction in HC occurs in all cases when the length χ of the reaction device is between 30 mm and 100 mm. It can be seen from this that the shortest length required for effective heat transfer from the burned gases to the unburned fuel-air mixture flowing through for the purpose of ignition has a certain value. The advantage of a longer length is offset by the detrimental effect on the machine's power factor caused by greater back pressure.

The graph of Fig. 12 shows that a considerable percentage reduction of HC can be observed,

ρ if the cross-section of the channel 27 is smaller than approx. 30 mm, since the unburned flow of the fuel-air mixture is then not dispersed.

Actual test results for a single-cylinder, two-stroke engine of 250 cm displacement are shown in FIGS. 10, 11 and 12. However, it can be assumed that the curves also apply to larger or smaller machines of the same type, since the length χ of the reaction device and the cross section a of the channels 27 remain the same, regardless of the engine displacement. Furthermore, the distance L also remains the same. This is true because the temperature of the gases at the exhaust port and the percentage of unburned hydrocarbons at this point, regardless of the size of the machine have the same values. A larger machine requires a reaction device that is larger in diameter,

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_ t-1 _

however, it is not longer. The cross section of the individual channels remains the same.

The schematic diagrams of Figs. 13, 14 and 15 show drawn through the supplied fuel-air mixture and dashed the burned exhaust gases. Fig. 13 shows the downward moving piston close to bottom dead center, the exhaust port 24 and the overflow port 23 both partially are open. Fig. 14 shows the piston at bottom dead center with fully opened overflow -ind exhaust gas opening. 15 shows the piston at the beginning of the upward movement, with the overflow opening and the exhaust gas opening partially are open, a small part of the supplied fuel-air mixture however, exits through the exhaust gas opening 24 into the exhaust gas duct 25. This part creates an unburned flow Fuel-air mixture. The task of the reaction device 26 is to make this mixture as complete as possible before it is released into the atmosphere along with the burned exhaust gases.

The graph in Fig. 16 shows that the flow rate of the combusted exhaust gases is very rapid at the time the opening of the exhaust port 24 increases and decreases for the position A according to FIG. The flow rate burned exhaust gases continue to drop by the time the piston reaches position B, which corresponds to FIG. the However, the flow rate of the unburned mixture slowly increases from the point of time when the spill port 23 opens until the bottom dead center is reached. Then it rises rapidly, after which the rise continues, after the overflow opening 23 has been closed by the upward movement of the piston. The peak value of the flow velocity occurs shortly before the piston closes the exhaust port 24. It's an important feature of the invention that the unburned mixture within the

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Reaction device 26 is burned. The graph of FIG. 17 relates to a four-stroke engine and is taken from S.A.E. Document No. 700676 of Aug. 1970. It can be seen that the concentration of unburned hydrocarbons increases rapidly at the outlet valve just before top dead center is reached. This state continues continues until the outlet valve closes. This shows that four-stroke machines are also suitable for the use of a Reaction device according to the invention are suitable.

It has been found that a catalytic coating on the thin walls of the reaction channels 27 the percentage reduction of HC in the exhaust gases improved. A heat-resistant metal such as a base metal should be used as the catalyst be as the thin walls by the hot burned gases and by the burning of the flowing through Heat generated by the fuel-air mixture. Precious metals like platinum show the best results initially, however, coatings with base metals turn out to be cheaper after a long period of operation. It has It has been shown that the initial percentage reduction of HC in the exhaust gases is higher for catalysts made of noble metal than is made of base metals. After a few hours of operation, however, the same results are found for both substances, and If the system continues to operate, the base metal catalysts produce a greater percentage reduction in HC. line Coating made of a nickel-copper base alloy on thin walls made of a stainless steel alloy leads after a long period of time Use to produce results that are at least comparable to those obtained with a platinum coating Ceramic walls received.

7, 8 and 9 are further embodiments of a Reaction device according to the invention shown. In the

- 11 -

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Device according to Fig. 7, the cartridge 30 contains a large number of mutually parallel channels 27a, each between a corrugated wall 28c and a straight flat wall 28d are formed. The pins 32 prevent rotational movement the walls within the bore of the cartridge 30.

In the embodiment according to FIG. 8, tubes 28e parallel to one another are arranged in lateral contact and run the entire length of the reaction device. The tubes 28e can at certain intervals along their length be welded together.

Figure 9 shows a reaction device having parallel walls 28f that intersect parallel walls 28g at right angles. the Pins 32 prevent the reaction device from rotating, which is formed by the walls 28f and 28g.

Above, the various walls for the reaction device have been described as being metal walls. It can, however other substances can also be provided, for example ceramics. If these are used, it is also beneficial to to coat the ceramic walls with a catalyst for the reasons described above. Tests of a single cylinder two-stroke machine with a displacement of 250 cm led to the following results in grams HC / km:

Gr / km % reduction No reaction device 4.90

Multi-level lattice structure
with base metal catalyst
according to Figs. 3 and 4 4.36 11%

Stainless steel alloy walls 3.96 19%

Base metal catalyst (Ni-Cu)

on stainless steel walls 2.78 43%

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A test procedure called "Los Angeles Test No. 4" was used for machine operation, which is carried out by the Environmental Protection Agency is recommended. The test weight was 210 kg.

In addition to the excellent reduction in HC emissions, a reaction device according to the invention was found the following additional benefits:

a) the device is compact and lightweight and has no moving parts,

b) it can be used with minimal modifications in currently common internal combustion engines,

c) it does not affect machine performance,

d) it works very reliably and permanently.

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Claims (1)

- 43 - Claims Exhaust gas reaction device for an internal combustion engine, marked by an elongated, heat-resistant arrangement to be mounted in the exhaust gas duct (25) of several, running in the longitudinal direction, by being in mutual contact parallel to one another Walls (28) formed channels (27) which run over the entire length of the reaction device (26) and their Walls (28) are thin in relation to the channel width. 2. Apparatus according to claim 1, characterized in that it has a length between 30 mm and 100 mm. 3. Apparatus according to claim 1 or 2, characterized in that the cross section of each channel (27) is less than 30 mm. 4. Apparatus according to claim 1, 2 or 3, characterized in that the thickness of the walls (28) is between 0.1 and 1.0 mm. 5. Apparatus according to claim 4, characterized in that the thickness of the walls (28) between 0.2 mm and 0.4 mm. 6. Device according to one of the preceding claims, characterized in that the walls (28) are formed from refractory metal. 7. Device according to one of claims 1 to 5, characterized characterized in that the walls' (28) are formed from ceramic material. - 14 - 709809/0753 8. Device according to one of the preceding claims, characterized in that the walls (28) are coated with a catalyst made of a refractory metal. 9. Apparatus according to claim 8, characterized in that a nickel-copper-based alloy is used as the catalyst is provided. 10. Device according to one of the preceding claims, characterized in that the channels (27) between a continuously corrugated, spiral-shaped curved wall (28b) and a continuously smooth, spiral-shaped curved wall (28a) are formed, the outsides of the spiral-shaped walls (28a, 28b) against movement fixed and the inner ends are freely movable. 11. Device according to one of claims 1 to 9, characterized in that the channels by a first group of mutually spaced parallel walls (28f) and a second group mutually spaced parallel to each other, to the first walls running at right angles (28g) are formed. 12. Device according to one of claims 1 to 9, characterized in that the channels (27a) are formed by parallel walls (28d) and corrugated walls (28c) lying therebetween. 13ο Device according to one of claims 1 to 9, characterized characterized in that the channels are formed by a bundle of cylindrical tubes (28e). 709809/0753 - I .j - 14. Internal combustion engine with a combustion chamber having an inlet opening and an exhaust gas opening and an exhaust gas duct emanating from the exhaust gas opening and an exhaust gas reaction device according to one of the preceding Claims, characterized in that the exhaust gas reaction device (26) in the exhaust gas duct (25) is arranged. 15. Internal combustion engine according to claim 14, characterized in that the exhaust gas reaction device (26) is arranged in the exhaust gas duct (25) directly at the exhaust gas opening (24). 16. Internal combustion engine according to claim 15, characterized in that the distance between the exhaust port (24) and the exhaust gas reaction device (26) is less than 110 mm. 17. Internal combustion engine according to one of claims 14, 15 or 16, characterized in that a cartridge (30) is provided, which continues the exhaust gas channel (25), and that the exhaust gas reaction device (26) in the central opening (31) of the cartridge (30) is arranged. 18. Internal combustion engine according to claim 17, characterized in that holding elements (32) for fixing the Exhaust reaction devices (26) are provided against axial movement within the cartridge (30). 19. Internal combustion engine according to claim 17 or 18, wherein the combustion chamber is in a stationary machine body is formed, characterized by a ' - 16 - 709809/0753 releasable attachment of the cartridge (30) to the machine body (11). 20. Internal combustion engine according to one of claims 14 to 19, marked by holding elements (47) for non-rotatable fastening of the cartridge (30) on the machine body (11). 21. Internal combustion engine according to one of claims 14 to 20, characterized in that elements (47) for non-rotatable fastening of the exhaust gas reaction device (26) are provided on the exhaust duct (25). 22. Internal combustion engine according to one of claims 17 to 21, characterized in that the cartridge is marked (30) is connected to an exhaust line (29). 23 · Internal combustion engine according to claim 22, characterized in that for connecting the cartridge (30) with the exhaust line (29) a device (50) is provided which allows a relative movement between the interconnected parts (30, 29) allows. 24. Internal combustion engine according to claim 23, characterized in that the connecting device (50) has at least one helical spring (54) outside the cartridge (30), one end (55) of which on the machine body (11) and the other end (57) of which is attached to the exhaust pipe (29). 25. Internal combustion engine according to one of claims 22 to 24, characterized by on the cartridge (30) 709809/0753 provided holders (34, 40 ) which are provided with arms (38, 41) which prevent movement of the exhaust gas reaction device (26) and its removal from the exhaust gas opening (24). 26. Internal combustion engine according to one of claims 22 to 25,
characterized by one provided between the cartridge (30) and the machine body (11)
insulating element (48). 709 8 0 9/0753