JP2020133508A - Flow passage structure - Google Patents

Abstract

To effectively improve a fluid flow speed while suppressing a rise of back pressure.SOLUTION: A flow passage structure comprises: a flow passage main body part 41 for making fluid circulate therein; a partitioning wall 50 for partitioning the inside of the flow passage main body part 41 into an upstream-side space part 41A and a downstream-side space part 41B; a fluid introduction port part 51 opened at the partitioning wall 50; and a communication pipe 60 having a cylinder part 61 extending to the downstream-side space part 41B side from the fluid introduction port part 51, and a fluid discharge port part 62 opened at an end part at a side opposite to the fluid introduction port part 51 of the cylinder part 61, and making the upstream-side space part 41A and the downstream-side space part 41B communicate with each other. An opening area of the fluid introduction port part 51 is formed larger than a flow passage cross section area of the cylinder part 61 and an opening area of the fluid discharge port part 62.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a flow path structure, and more particularly to a flow path structure of an exhaust pipe through which exhaust gas discharged from an engine flows.

Generally, the exhaust pipe of an engine has a PM sensor that detects particulate matter (PM) in the exhaust gas, a NOx sensor that detects nitrogen oxides (NOx) in the exhaust gas, and exhaust gas. Various sensors such as a lambda sensor for detecting the air-fuel ratio of the air-fuel ratio are provided.

As an example of this type of sensor, a PM sensor that detects the amount of PM in the exhaust gas based on the resistance value between the electrodes that changes depending on the PM collected between the pair of electrodes is known (for example, , Patent Document 1 etc.).

JP-A-2009-144557

By the way, in various sensors for detecting the state amount of the exhaust gas as described above, a certain flow velocity may be required for the exhaust gas flowing into the sensor unit in order to ensure the detection accuracy. However, depending on the shape of the exhaust pipe provided with the sensor, the exhaust flow velocity of the sensor unit may not be sufficiently secured. In order to secure the exhaust flow velocity, it is conceivable to narrow the flow path area of the exhaust pipe, but in this case, the flow resistance of the exhaust gas increases, which may lead to an increase in back pressure.

An object of the present disclosure technique is to provide a flow path structure capable of effectively improving a fluid flow velocity while suppressing an increase in back pressure.

The technique of the present disclosure includes a flow path main body for flowing a fluid, a partition wall for partitioning the inside of the flow path main body into an upstream space portion and a downstream space portion, and a fluid introduction port portion opening in the partition wall. It has a tubular body portion extending from the fluid introduction port portion to the downstream side space portion side, and a fluid discharge port portion opening at an end portion of the tubular body portion opposite to the fluid introduction port portion. A communication pipe for communicating the upstream side space portion and the downstream side space portion is provided, and the opening area of the fluid introduction port portion is the flow path cross-sectional area of the tubular body portion and the opening area of the fluid discharge port portion. It is characterized in that it is formed larger than.

Further, it is preferable that the tubular body portion is formed in a hollow conical trapezoidal shape in which the cross-sectional area of the flow path is reduced from the fluid introduction port portion toward the fluid discharge port portion.

Further, the flow path main body portion has a cylindrical peripheral wall portion, and the partition wall is formed in a disk shape in which the peripheral edge thereof is fixed to the inner peripheral surface of the peripheral wall portion. The portion is formed to be curved along the inner peripheral surface of the peripheral wall portion, and the fluid discharged from the fluid discharge port portion swirls in the downstream space portion along the inner peripheral surface of the peripheral wall portion. It is preferable to be washed away.

Further, the fluid body is an exhaust pipe through which the exhaust gas discharged from the engine flows, and a carrier carrying a catalyst for purifying the exhaust gas or a particulate substance in the exhaust gas is contained in the upstream space. It is preferable that a filter for collecting the exhaust gas is housed, and a sensor for detecting the state amount of the exhaust gas is provided at a portion of the exhaust pipe adjacent to the fluid discharge port portion.

According to the technique of the present disclosure, the fluid flow velocity can be effectively improved while suppressing the increase in back pressure.

It is a schematic overall block diagram which shows the exhaust system of the engine which concerns on this embodiment. It is a schematic perspective view which shows by cutting out a part of the post-stage casing of the post-stage post-treatment apparatus which concerns on this embodiment. It is a schematic diagram which viewed the partition wall and the communication pipe which make up the flow path structure which concerns on this Embodiment from the axial direction.

Hereinafter, the flow path structure according to the present embodiment will be described with reference to the accompanying drawings. The same parts are designated by the same reference numerals, and their names and functions are also the same. Therefore, detailed explanations about them will not be repeated.

FIG. 1 is a schematic overall configuration diagram showing an exhaust system of the engine 10 according to the present embodiment.

As shown in FIG. 1, the engine 10 includes an engine main body 11 including a cylinder head, a cylinder block in which a plurality of cylinders are formed, and the like. The cylinder head of the engine body 11 is provided with an exhaust manifold 12 that collects exhaust gas discharged from each cylinder.

In the exhaust manifold 12, in order from the exhaust upstream side, the upstream pipe 13, the front casing 21 of the front post-treatment device 20, the connection pipe 14, and the rear casing 41 of the post-treatment device 40 (an example of the flow path main body of the present disclosure). And the downstream pipe 15 and the like are connected.

The upstream pipe 13 is formed in a substantially cylindrical shape, and its upstream end is connected to the exhaust collecting portion 12A of the exhaust manifold 12. The downstream end of the upstream pipe 13 is connected to the upstream opening of the front casing 21.

The front casing 21 is formed in a substantially cylindrical shape, and the oxidation catalyst 22 and the filter 23 are housed therein in this order from the exhaust upstream side.

The oxidation catalyst 22 is formed by supporting a catalyst component or the like on the surface of a ceramic carrier such as a cordierite honeycomb structure. When unburned fuel (hydrocarbon: HC) is supplied by the post-injection of the engine 10 or the exhaust pipe injection of an exhaust pipe injector (not shown), the oxidation catalyst 22 oxidizes the unburned fuel (hydrocarbon: HC) to raise the exhaust temperature.

The filter 23 is formed, for example, by arranging a large number of cells partitioned by a porous partition wall along the flow direction of the exhaust gas, and alternately sealing the upstream side and the downstream side of these cells. .. The filter 23 collects PM in the exhaust gas in the pores and the surface of the partition wall, and when the PM accumulation amount reaches a predetermined amount, the filter forced regeneration for burning and removing the PM is carried out.

The connection pipe 14 is formed in a substantially S-shaped cylindrical shape as a whole, and connects the downstream opening of the front casing 21 and the upstream opening of the rear casing 41. A urea water injector 35 forming a part of the urea water injection device 30 is provided at a predetermined portion of the connection pipe 14.

The urea water injection device 30 supplies the urea water tank 31 that stores the urea water, the strainer 32 that is immersed in the urea water in the urea water tank 31 to remove foreign matter, and the supply pipe 33 that is connected to the strainer 32. A urea water pump 34 provided in the pipe 33 to pump urea water from the urea water tank 31 and a urea water injector 35 for injecting the urea water supplied from the supply pipe 33 into the connecting pipe 14 are provided.

The urea water injected from the urea water injector 35 into the connecting pipe 14 is hydrolyzed by exhaust heat to generate ammonia (NH3), and the downstream selective reduction catalyst 48 (Selective Catalytic Reduction: hereinafter, SCR catalyst). Is supplied as a reducing agent.

The rear casing 41 is formed in a substantially cylindrical shape. Inside the rear casing 41, a partition wall 50 is provided that divides the internal space of the rear casing 41 into an upstream space 41A and a downstream space 41B. The SCR catalyst 48 is housed in the upstream space 41A.

The SCR catalyst 48 is formed by supporting zeolite or the like on, for example, a porous ceramic carrier. The SCR catalyst 48 adsorbs ammonia supplied as a reducing agent from the urea water injector 35, and selectively reduces and purifies NOx from the exhaust gas passing by the adsorbed ammonia.

A substantially cylindrical downstream pipe 15 that communicates with the downstream space 41B and guides the exhaust gas to the atmosphere is connected to the peripheral wall on the downstream side of the rear casing 41. Further, a PM sensor 90, a NOx sensor 91, and the like are provided on the peripheral wall on the downstream side of the rear casing 41. The sensor provided in the rear casing 41 is not limited to the PM sensor 90 and the NOx sensor 91, and may be a sensor that detects another exhaust state amount such as an exhaust temperature sensor.

In the present embodiment, the partition wall 50 communicates the upstream space portion 41A and the downstream space portion 41B, and increases the flow velocity of the exhaust gas flowing from the upstream space portion 41A into the downstream space portion 41B. 60 is provided. Hereinafter, details of the flow path structure of the present embodiment including the partition wall 50 and the communication pipe 60 will be described with reference to FIGS. 2 and 3.

FIG. 2 is a schematic perspective view showing the post-stage post-processing device 40 according to the present embodiment by cutting out a part of the post-stage casing 41.

As shown in FIG. 2, the rear casing 41 is formed in a substantially bottomed tubular shape as a whole, and has a substantially cylindrical peripheral wall portion 42 and a disk-shaped side wall portion 43 that closes the downstream end of the peripheral wall portion 42. It has.

A disk-shaped partition wall 50 having an outer diameter substantially the same as the inner diameter of the peripheral wall portion 42 is provided at a predetermined portion of the inside of the peripheral wall portion 42 on the downstream side of the intermediate position in the tubular axis direction. .. The peripheral edge of the partition wall 50 is joined and fixed to the inner peripheral surface of the peripheral wall portion 42 by welding or the like. By this partition wall 50, the internal space of the rear casing 41 is partitioned into the upstream space 41A and the downstream space 41B. The partition wall 50 may be fastened and fixed to the peripheral wall portion 42 with bolts and nuts or the like.

Of the peripheral wall portion 42 of the rear casing 41, the SCR catalyst 48 is housed and held in a portion corresponding to the upstream space portion 41A (hereinafter referred to as the upstream peripheral wall portion 42A) via a mat member (not shown) or the like. .. The connection pipe 14 (shown in FIG. 1) described above is connected to the upstream end of the upstream peripheral wall portion 42A.

The PM sensor 90 and the NOx sensor 91 are provided in a portion of the peripheral wall portion 42 of the rear casing 41 corresponding to the downstream space portion 41B (hereinafter referred to as the downstream peripheral wall portion 42B) in a substantially vertical direction (or in the sensor axial direction). The sensor portions 90A and 91A are attached so as to be exposed in the downstream space portion 41B in a state of being oriented in a slightly tilted direction. The PM sensor 90 and the NOx sensor 91 are preferably provided at a portion vertically above the cylinder axis of the downstream peripheral wall portion 42B in order to prevent water from entering from the downstream pipe 15 and the like. ..

Of the downstream peripheral wall portion 42B, the portion vertically below the cylinder axis, in other words, the portion facing the sensors 90 and 91 across the cylinder axis, is a cylindrical downstream portion that guides the exhaust gas to the atmosphere. The pipe 15 is connected. That is, the exhaust gas is configured to be discharged downward from the downstream side space 41B through the downstream pipe 15.

The partition wall 50 is formed in a substantially disk shape, and its plane surface is provided so as to be orthogonal to the cylinder axis (exhaust gas flow direction) of the peripheral wall portion 42. The partition wall 50 is formed with an opening of an exhaust introduction port 51 (fluid introduction port) that is curved in a semicircular shape.

The exhaust introduction port 51 extends in a semicircular shape along the peripheral edge of the partition wall 50 at a portion on the left side of the axial center of the partition wall 50 in a state where the partition wall 50 is viewed in the axial direction from the downstream side. It is provided in. The exhaust introduction port 51 may be provided at a position different from the illustrated example (for example, on the right side in the drawing with respect to the axis of the partition wall 50) depending on the arrangement position of the sensors 90 and 91.

The communication pipe 60 has a tubular body main body 61 formed in a tubular shape that is curved in a substantially C shape as a whole, and is provided on a side surface of the partition wall 50 facing the downstream space 41B. Specifically, the tubular body main body 61 has an opening peripheral edge on the upstream side joined to the peripheral edge of the exhaust introduction port 51 by welding or the like, and faces upward along the inner peripheral surface of the downstream peripheral wall portion 42B. It is extended while curving. Further, the tubular body portion 61 is provided so that the exhaust discharge port portion 62 (fluid discharge port portion) formed at the downstream end thereof opens so as to face the sensor portion 90A of the PM sensor 90.

In the present embodiment, the opening area V1 of the exhaust introduction port 51 is larger than the opening area V2 of the exhaust discharge port 62 (V1> V2), in other words, the flow path of the tubular body 61 of the communication pipe 60 is interrupted. The area (cross-sectional area of the flow path orthogonal to the flow direction of the exhaust gas) is formed so as to decrease from the exhaust introduction port 51 on the upstream side toward the exhaust discharge port 62 on the downstream side.

In this way, the tubular body 61 of the communication pipe 60 is formed into a substantially hollow conical trapezoidal cylinder that gradually shrinks in diameter while curving along the inner peripheral surface of the downstream peripheral wall portion 42B, thereby forming the upstream space portion 41A. The exhaust gas that flows into the tubular body body 61 through the exhaust introduction port 51 is discharged from the exhaust discharge port 62 toward the downstream space 41B while increasing the flow velocity. Further, by forming the opening area V1 of the exhaust introduction port 51 larger than the flow path cross-sectional area of the cylinder body 61 and the opening area V2 of the exhaust discharge port 62, the air flows through the cylinder body 61. The increase in the flow resistance of the exhaust gas will be suppressed, and the increase in back pressure will also be effectively suppressed.

The opening area of the exhaust introduction port 51 and the exhaust discharge port 62 depends on the dimensions of the rear casing 41, the capacity of the SCR catalyst 48 arranged on the upstream side, the displacement of the engine 10, and the like. Depending on the specifications, it may be appropriately set within a range in which the increase in back pressure can be effectively suppressed.

The action and effect of the flow path structure according to the present embodiment configured as described above will be described with reference to FIG.

FIG. 3 is a schematic view of the downstream peripheral wall portion 42B notched in the radial direction, and the partition wall 50 and the communication pipe 60 viewed axially from the downstream side in the exhaust flow direction.

As shown in FIG. 3, the exhaust gas E1 that has flowed from the upstream space portion 41A through the exhaust introduction port portion 51 into the tubular body portion 61 of the communication pipe 60 passes through the tubular body portion 61 and is exhausted. It is discharged from the discharge port portion 62 into the downstream space portion 41B. The exhaust gas E2 discharged from the exhaust discharge port 62 flows along the inner peripheral surface of the downstream peripheral wall portion 42B, and flows along the inner peripheral surface of the downstream peripheral wall portion 42B, and is adjacent to the exhaust discharge port 62. It is guided to the sensor unit 91A of 91. The exhaust gas E3 that has passed through the sensor portions 90A and 91A reaches the downstream pipe 15 while swirling in the downstream space portion 41B along the inner peripheral surface of the downstream peripheral wall portion 42B, and efficiently reaches the downstream pipe 15 from the downstream pipe 15. It is designed to be discharged.

In the present embodiment, the tubular body main body 61 of the communicating pipe 60 is formed in a substantially hollow conical trapezoidal tubular shape that gradually shrinks in diameter while curving along the inner peripheral surface of the downstream peripheral wall portion 42B. The exhaust gas E1 passing through the inside is configured to be discharged from the exhaust discharge port portion 62 toward the downstream side space portion 41B while increasing the flow velocity thereof. As a result, it is possible to surely increase the flow velocity of the exhaust gas E2 flowing into the sensor portions 90A and 91A of the sensors 90 and 91 adjacent to the exhaust discharge port portion 62, and the detection accuracy of each sensor 90 and 91 is effective. Can be improved.

Further, the opening area of the exhaust introduction port 51 that takes in the exhaust gas E1 into the tubular body 61 of the communication pipe 60 is determined from the flow path cross-sectional area of the tubular body 61 and the opening area V2 of the exhaust discharge port 62. The large size of the exhaust gas E1 is configured to effectively suppress an increase in the flow resistance of the exhaust gas E1 passing through the main body of the cylinder 61. As a result, the increase in back pressure is surely suppressed, and it is possible to prevent deterioration of the fuel efficiency performance of the engine 10.

It should be noted that the present disclosure is not limited to the above-described embodiment, and can be appropriately modified and implemented without departing from the gist of the present disclosure.

For example, although the above-mentioned flow path structure has been described as being provided in the rear-stage casing 41, it can also be provided in the front-stage casing 21, and the application of this embodiment is not limited to the exhaust system flow path of the engine 10. It can be widely applied to the intake system flow path and the fluid flow path of devices other than the engine.

10 Engine 13 Upstream piping 14 Connection piping 15 Downstream piping 20 Pre-stage aftertreatment device 21 Front-stage casing 22 Oxidation catalyst 23 Filter 40 Post-stage post-treatment device 41 Post-stage casing (flow path main body)
41A Upstream space 41B Downstream space 42 Peripheral wall 50 Partition wall 51 Exhaust inlet (fluid inlet)
60 Communication pipe 61 Cylinder body 62 Exhaust discharge port 90 PM sensor 91 NOx sensor

Claims (4)

The main body of the flow path that allows fluid to flow,
A partition wall that divides the inside of the flow path main body into an upstream space portion and a downstream space portion,
A fluid inlet that opens into the partition wall and
It has a tubular body that extends from the fluid introduction port to the downstream space side, and a fluid discharge port that opens at the end of the tubular body that is opposite to the fluid introduction port, and is on the upstream side. A communication pipe for communicating the space portion and the downstream space portion is provided.
A flow path structure characterized in that the opening area of the fluid introduction port is formed to be larger than the cross-sectional area of the flow path of the tubular body and the opening area of the fluid discharge port. The flow path structure according to claim 1, wherein the tubular body portion is formed in a hollow conical trapezoidal tubular shape in which the cross-sectional area of the flow path is reduced from the fluid introduction port portion toward the fluid discharge port portion. The flow path main body portion has a cylindrical peripheral wall portion, and the partition wall is formed in a disk shape in which the peripheral edge thereof is fixed to the inner peripheral surface of the peripheral wall portion, and the tubular body portion is formed. , It is formed to be curved along the inner peripheral surface of the peripheral wall portion, and the fluid discharged from the fluid discharge port portion swirls and flows in the downstream space portion along the inner peripheral surface of the peripheral wall portion. The flow path structure according to claim 1 or 2. The fluid body is an exhaust pipe through which exhaust gas discharged from the engine flows, and a carrier carrying a catalyst for purifying the exhaust gas or a particulate substance in the exhaust gas is captured in the upstream space. Any one of claims 1 to 3, wherein a collecting filter is housed, and a sensor for detecting the state amount of the exhaust gas is provided at a portion of the exhaust pipe adjacent to the fluid discharge port portion. The flow path structure according to.

Images