JPH07659Y2 - Exhaust gas aftertreatment device - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention relates to an aftertreatment device for exhaust gas emitted from a diesel engine, specifically, an exhaust gas for collecting and burning particulate matter contained in the exhaust gas. The present invention relates to a gas aftertreatment device.

(Prior Art) An exhaust gas post-treatment device for burning particulates is already well known. An example thereof is shown in FIG. In the figure, reference numeral 50 shows a part of a trap for collecting particulates having a known filter structure. The trap 50 has an upstream chamber 51 connected to the upstream side thereof in the exhaust gas flow direction. Exhaust gas discharged from an engine (not shown) is introduced into the upstream chamber 51 in the direction of arrow a. The upstream chamber 51 is provided with a combustion gas intake pipe 52 which is a curved pipe for introducing the combustion gas b generated by a burner or the like (not shown) into the central portion of the upstream chamber. In front of the outlet 52a of the combustion gas intake pipe 52, an equalizer 53 having a conical surface with a wide-angle cross section is arranged.

When particulate adhesion or deposition on the trap 50 is detected by measuring the pressure loss between the upstream chamber 51 of the trap 50 and a downstream chamber (not shown), the flow of exhaust gas flowing in the direction of arrow a is bypassed (not shown). The pipeline is switched to and the introduction of exhaust gas to the trap 50 is stopped. At the same time, the combustion gas b from the burner is sent to the combustion gas intake pipe 52. The combustion gas collides with the equalizer 53, its flow velocity is reduced and diffused, and then the combustion gas is supplied toward the upstream end 50a of the trap 50. The combustion gas supplied to the trap 50 regenerates the trap by burning the particulates adhering to and accumulated in the trap 50.

(Problems to be solved by the invention) Since the combustion gas taken in from the combustion gas intake pipe 52 at the time of trap regeneration is weakened in its flow velocity by the equalizer 53, it is supplied toward the upstream end 50a of the trap 50. However, due to the inertia of the combustion gas flowing through the combustion gas intake pipe 52, the combustion gas buffered by the equalizer 53 is supplied in a non-uniform distribution to the end face of the trap, the temperature of the trap becomes non-uniform, and the combustion of particulates There is a problem that the distribution becomes non-uniform. Further, the combustion gas intake pipe 52 disposed in the upstream chamber 51 disturbs the flow of the exhaust gas, the flow of the exhaust gas flowing into the trap 50 is deflected, and the particulates adhere unevenly to the trap. There is also the problem of deposits. These problems lead to non-uniform trap regeneration and thermal stress leading to destruction of the device components containing the trap.

(Means for Solving the Problems) The present invention aims at providing an exhaust gas post-treatment device capable of uniformly depositing exhaust gas on a trap and making the distribution of combustion gas on the trap uniform. In the above, a gas supply chamber provided upstream of the trap, an expansion chamber provided upstream of the gas supply chamber, which is cut off from the supply chamber, and into which combustion gas is introduced from a combustion gas inlet, The upstream end of the combustion chamber is connected to the exhaust gas flow path through the chamber, and the downstream end of the trap is separated from the upstream end of the trap to be located in the gas supply chamber. A plurality of combustion gas intake holes are provided to take in the combustion gas from a direction different from the direction in which the combustion gas is introduced into the expansion chamber from the mouth, and a plurality of exhaust gas and combustion gas are formed in the portion located in the gas supply chamber. A gas diffusion cylinder having a gas discharge hole for discharging the burning gas from the cylindrical portion to the gas supply chamber.

(Function) Exhaust gas discharged from the engine and introduced into the gas diffusion cylinder is discharged into the gas supply chamber through a plurality of gas discharge holes and heads to the trap where particulates contained therein are attached and captured. Gathered. When the necessity of trap regeneration is detected, the exhaust gas flow path is switched, the introduction of exhaust gas into the trap is stopped, and the combustion gas is supplied. The combustion gas introduced into the expansion chamber is introduced into the gas diffusion cylinder from the combustion gas intake hole, and then is supplied from the gas discharge hole to the trap via the gas supply chamber.

(Embodiment) Hereinafter, the present invention will be described in detail based on the illustrated embodiment.

In FIGS. 1 and 2, reference numeral 1 denotes a gas supply chamber arranged upstream of the trap 50 (see FIG. 5), which is connected and fixed to the outer cylinder of the trap by a flange 1a. A cone-shaped expansion chamber 2 is formed on the upstream side of the gas supply chamber 1, and both chambers are isolated from each other by a partition wall 3. The expansion chamber 2 is connected to a combustion gas inlet 4 into which combustion gas generated by a burner (not shown) is selectively introduced. The expansion chamber 2 has a flange 5a at the upstream end thereof.
A gas diffusion cylinder 5 connected to an exhaust gas flow path (not shown) is densely penetrated and fixed. The downstream end 5b of the gas diffusion cylinder 5 is located in the gas supply chamber 1. In the case of the illustrated example, the end surface 5c of the downstream end portion 5b is closed, and this end surface 5c is located at a predetermined distance from the upstream end portion 50a (see FIG. 5) of the trap. . In the end cylindrical portion of the gas diffusion cylinder 5 located in the gas supply chamber 1, there is provided a gas discharge hole 5d having a size that is not easily blocked by adhesion of particulates of normal size. A plurality is formed. This gas exhaust hole
5d is for discharging combustion gas b and exhaust gas a, which will be described later, to the inner surface of the end surface 5c, and then discharging these into the gas supply chamber 1. The total opening area of the holes 5d is introduced into the cylindrical body 5. The size is set so as not to give a pressure loss to the generated exhaust gas and combustion gas. The gas diffusion cylinder 5 located in the expansion chamber 2 has a pair of combustion gases in a direction different from the introduction direction c of the combustion gas introduced into the chamber, in the illustrated example, a direction orthogonal to the introduction direction c. An intake hole 5e is formed.

The operation of the embodiment configured as described above will be described.

Exhaust gas discharged from an engine (not shown) is introduced into the gas diffusion cylinder 5 in the direction of arrow a, but the gas discharge hole formed in the end cylindrical portion by closing the downstream end thereof. It is diffused and discharged into the gas supply chamber 1 from 5d, 5d. The exhaust gas in the gas supply chamber 1 is supplied to the trap 50 (see FIG. 5) by the exhaust gas pressure on the upstream side of the trap, flows inside the trap 50, and is exhausted to the atmosphere. When passing through the trap, the particulates contained in the exhaust gas adhere to the trap and are collected. In this case, the exhaust gas supplied to the trap is introduced into the trap in the gas supply chamber 1 without its flow direction being specified, in other words, without being deflected, so that the particulates are uniformly attached to the trap. accumulate.

Now, for example, based on the calculation of the pressure loss on the upstream side and the downstream side of the trap in the flow path of the exhaust gas, when it is detected that the accumulated amount of particulates in the trap is close to the allowable limit value, The flow paths are switched, the introduction of exhaust gas into the gas diffusion cylinder 5 is stopped, and the supply of combustion gas is started. The exhaust gas is exhausted into the atmosphere via a bypass exhaust passage (not shown). As shown in FIG. 2, the combustion gas is introduced from the combustion gas introduction port 4 into the expansion chamber 2 in the direction of arrow c, collides with the outer peripheral surface of the cylinder of the gas diffusion cylinder 5, and its flow velocity is reduced to expand the expansion chamber. And is expanded in the annular space formed by the cylinder. The expanded combustion gas is taken into the gas diffusion cylinder 5 through the combustion gas intake holes 5e, 5e as shown by the arrow e. The combustion gas introduced into the cylindrical body 5 is discharged to the gas supply chamber 1 through the gas discharge holes 5d, 5d ... As indicated by an arrow d, because the downstream end surface of the combustion gas is closed. The combustion gas discharged to the gas supply chamber 1 is trapped by the pressure of the supplied combustion gas.
(See FIG. 5) It is pushed into the inside and uniformly supplied to the end face on the upstream side. Therefore, the particulates trapped in the trap are uniformly burned in the longitudinal direction of the trap and the cross-sectional direction orthogonal thereto. When the supply of combustion gas exceeds the time required for particulate combustion,
When the supply of the gas is stopped and the flow path of the exhaust gas is switched from the bypass side to the post-treatment device side, the collection of particulates is started again.

In the embodiment shown in FIG. 1, if the diffusion cylinder 2 is fixed to the partition wall 3 that blocks the gas supply chamber 1 and the expansion chamber 2 in order to maintain airtightness, the temperature difference between the exhaust gas and the combustion gas and the post-treatment process There is a fear that a thermal stress may damage the space between the cylindrical body 5 and the partition wall 3 or the space between the partition wall 3 and the gas supply chamber 1 due to the temperature change before and after. Although it is considered that the problem of thermal stress will be eliminated if the cylindrical body is penetrated with high accuracy without being fixed to the partition wall, the cost becomes high in consideration of the accuracy of parts and the assembling property.

Therefore, referring to FIGS. 3 and 4, another embodiment of the present invention will be described. Since this embodiment is characterized in that two gas diffusion cylinders having different diameters are concentrically arranged, members having the same functions as those in the above-mentioned embodiments are designated by the same reference numerals. In these drawings, the gas diffusion cylinder 15 is composed of a small-diameter cylinder 15A connected to a flow path of exhaust gas which is made to flow through a flange 15Aa at an upstream end thereof in a direction of an arrow a, and is concentric with the cylinder 15A. Large diameter cylindrical body 15
It consists of B and. The cylinder 15A is located inside the expansion chamber 2, and the cylinder 15B has its upstream end 15Ba located inside the expansion chamber 2 and serves as a combustion gas intake hole between the cylinder 15A and the end 15Ab. To form a ring-shaped gap G. This gap G is
It is arranged at a position where the combustion gas in the expansion chamber is taken into the cylindrical body 15B in a direction f different from the introduction direction of the combustion gas introduced into the expansion chamber 2 in the direction shown by the arrow b in FIG. Cylindrical body 15B
Is fixed to the partition wall 3, and its downstream end 15b is located in the gas supply chamber 1. The downstream end of the cylindrical body has its end face 15Bc closed, and a large number of gas discharge holes 15Bd, 15Bd ... Are formed in the cylindrical portion.

The operation of the embodiment configured as described above will be described. Exhaust gas discharged from the engine is discharged from the cylinder 15 in the direction of arrow a.
After flowing into A, it is introduced into the cylindrical body 15B. The exhaust gas introduced into the cylindrical body 15B has its flow velocity weakened due to the closed end surface, and is discharged into the gas supply chamber 1 through the gas discharge holes 15d, 15d ... As shown by the arrow d. The exhaust gas discharged into the gas supply chamber 1 has a uniform distribution in the gas supply chamber and flows toward the trap 50 (see FIG. 5). Therefore, particulates are collected in the trap with a uniform distribution.

When the timing of trap regeneration is detected, the combustion gas inlet 4
Combustion gas is introduced from. This combustion gas is introduced in the direction shown by the arrow b in FIG. 3 and expanded by being blocked by the outer peripheral surface of the cylindrical body 15B located in the expansion chamber 2 and the partition wall 3 and then expanded by the gap G. It is taken from the inside of the cylinder 15A. Combustion gas taken into the cylinder 15A,
After entering the cylindrical body 15B, an arrow d is drawn from the gas discharge holes 15d, 15d.
Is discharged to the gas supply chamber 1. The combustion gas discharged from the cylindrical portion of the cylinder into the gas supply chamber 1 is supplied to the trap 50 (see FIG. 5) with a uniform distribution, and the particulates accumulated on the trap 50 are burned and discharged to discharge the same. Reproduce. When the supply of combustion gas has passed the time required for particulate firing, the supply of the gas is stopped, and
The collection of particulates is started again by switching the exhaust gas flow path from the bypass side to the post-treatment device side. According to this embodiment, since the gas diffusion cylinder is divided into two parts, even if the cylinder 15B expands and contracts due to thermal stress, it is possible to prevent the destruction of itself and other parts.

(Effect of the Invention) As described above, according to the present invention, since the combustion gas inlet does not obstruct the flow path of the exhaust gas and the gas diffusion cylinder makes the distribution distribution uniform, the characteristics of the trap can be improved. The distribution of deposition and deposition of curate becomes uniform. Further, since the distribution of the combustion gas supplied to the trap becomes uniform, the distribution of the particulate combustion becomes uniform, the regeneration of the trap becomes uniform, and a durable exhaust gas post-treatment device is obtained.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential portion of an exhaust gas post-treatment device showing an embodiment of the present invention, FIG. 2 is a front sectional view of the same, and FIG. 3 is a longitudinal sectional view of an essential portion showing another embodiment of the present invention. Fig. 4 is a front sectional view of the same as Fig. 4, and Fig. 5 is a longitudinal sectional view showing an example of a conventional exhaust gas post-treatment device. DESCRIPTION OF SYMBOLS 1 ... Gas supply chamber, 2 ... Expansion chamber, 3 ... Partition wall, 4 ... Combustion gas inlet, 5,15 ... Gas diffusion cylinder, 5d, 15d ... Gas discharge hole, 5
e, G ... Combustion gas intake hole, 50 ... Trap.

Claims (1)

[Scope of utility model registration request] 1. An exhaust gas aftertreatment device for collecting particulates in exhaust gas discharged from an engine in a trap, and then supplying combustion gas to the trap to burn the particulates to regenerate the trap. , A gas supply chamber provided adjacent to the upstream end of the trap in the flow direction of the exhaust gas, and a gas supply chamber upstream of the gas supply chamber that is cut off from the supply chamber and burns from the combustion gas inlet port. An expansion chamber into which gas is introduced, and an upstream end of the expansion chamber that penetrates the expansion chamber and is connected to an exhaust gas flow path, and a downstream end of the expansion chamber that is separated from an upstream end of the trap to supply the gas. A combustion gas intake hole that is located inside the chamber and that takes in the combustion gas from a direction different from the direction of introduction of the combustion gas that is introduced into the expansion chamber from the combustion gas introduction port; A plurality of gas diffusion cylinders formed in a portion located in the supply chamber, the gas diffusion cylinder having a gas discharge hole for discharging exhaust gas and combustion gas from the cylindrical portion to the gas supply chamber. Aftertreatment device.