EXHAUST PURIFICATION DEVICE BURNER

This burner is disposed at the upstream side of a DPF and raises the temperature of exhaust by combusting an air-fuel mixture of air and fuel in a combustion region within a flame holder. The burner is provided with: an upstream-side cover enclosing the peripheral wall of the flame holder; and a partition wall that partitions the gap between the flame holder and the upstream-side cover into a prior-stage exhaust chamber and a latter-state exhaust chamber. An exhaust tube through which exhaust from an engine flows is connected to the upstream-side cover; a through hole that interconnects the prior-stage exhaust chamber and the latter-stage exhaust chamber is formed at the partition wall; exhaust flows in from the exhaust tube at the prior-stage exhaust chamber; and exhaust flows in from the prior-stage exhaust chamber through the through hole to the latter-stage exhaust chamber.

Skip to: Description  ·  Claims  · Patent History  ·  Patent History
Description
TECHNICAL FIELD

The technique of the present disclosure relates to a burner for an exhaust purification device. The burner is applied to an exhaust purification device, which purifies exhaust gas from the engine, and raises the temperature of the exhaust gas.

BACKGROUND ART

Conventional diesel engines include, in the exhaust passage, a diesel particulate filter (DPF), which captures particulate matter (PM) contained in exhaust gas. In such a DPF, in order to maintain the function of capturing particulate matter, a regeneration process, in which particulate matter captured by the DPF is burnt, is performed.

For example, Patent Document 1 discloses an exhaust purification device, in which a burner is arranged upstream of a DPF. Exhaust gas with the temperature raised by the burner is sent to the DPF to regenerate the DPF. In the burner, fuel for the engine and air for combustion are introduced to a combustion area, which is the inside space of a tubular flame stabilizer, and mixture of the fuel and the air for combustion is produced. The air-fuel mixture is then burnt by ignition, and the temperature of the exhaust gas is raised.

PRIOR ART DOCUMENT Patent Document

  • Patent Document 1: Japanese Laid-Open Patent Publication No. 2011-185493

SUMMARY OF THE INVENTION Problem that the Invention is to Solve

While an engine is cold, the temperature of a flame stabilizer and the temperature of gas in the combustion area are low relative to those after completion of warming-up of the engine. For this reason, when the regeneration process is performed while the engine is cold, unburned gas contained in the combustion gas increases compared to that after the completion of the warming-up of the engine.

It is an objective of the technique of the present disclosure to provide a burner for an exhaust purification device that reduces fuel discharged as unburned gas.

Means for Solving the Problems

To achieve the above objective, according to one aspect of the present disclosure, a burner for an exhaust purification device (an exhaust purification device burner) comprises a tubular flame stabilizer having a space in which air-fuel mixture of fuel and air is combusted and an ejection port for ejecting combustion gas, a tubular cover that surrounds the flame stabilizer, in which a gap is formed between an inner circumference face of the cover and an outer circumference face of the flame stabilizer, an exhaust pipe connected to the cover to deliver exhaust gas into the gap, and a partition portion arranged in the gap to partition the gap into an upstream exhaust chamber and a downstream exhaust chamber. The upstream exhaust chamber is connected to the exhaust pipe and the downstream exhaust chamber, and the downstream exhaust chamber is connected to the ejection port of the flame stabilizer.

According to the above aspect, exhaust gas flowing into the gap between the flame stabilizer and the cover takes a more complex route due to the partition portion. This increases the possibility for the exhaust gas to contact the flame stabilizer and raises the temperature of the flame stabilizer. Thus, the temperature of gas is more easily raised in the combustion area heated by the flame stabilizer. As a result, even in cold, the temperature of the flame stabilizer and the temperature of the gas in the combustion area are promptly raised, and fuel in the combustion area is more easily vaporized, so that the fuel discharged as unburned gas after being supplied to the combustion area is reduced.

Preferably, the flame stabilizer is shaped as a cylindrical tube, and the exhaust pipe extends in the tangential direction of the outer circumferential face of the flame stabilizer.

According to the above aspect, since the exhaust gas flowing into the upstream exhaust chamber more easily swirls around the flame stabilizer, the flows of the exhaust gas are more easily aligned in the upstream exhaust chamber in one direction. As a result, for example, compared to when the exhaust gas flowing into the upstream exhaust chamber is divided into flows in two directions by striking the circumference wall of the flame stabilizer, it is easier for the exhaust gas to contact the portion of the outer circumferential face of the flame stabilizer that defines the upstream exhaust chamber. For this reason, heat is efficiently transferred from the exhaust gas to the flame stabilizer.

Preferably, the exhaust pipe connects to an outer circumferential face of the cover at one location.

According to the above aspect, the exhaust gas is introduced to the upstream exhaust chamber from one location of the upstream exhaust chamber. For this reason, the exhaust gas more easily swirls around the flame stabilizer in the upstream exhaust chamber. As a result, compared to when an exhaust pipe communicates with the upstream exhaust chamber at a plurality of locations, the flows of the exhaust gas are more easily aligned in one direction in the upstream exhaust chamber.

Preferably, the partition portion protrudes from the outer circumferential face of the flame stabilizer toward the inner circumferential face of the cover and is coupled to the outer circumferential face of the flame stabilizer and the inner circumferential face of the cover. The partition portion is a partition wall that partitions the gap into the upstream exhaust chamber and the downstream exhaust chamber. The partition wall includes a communication hole that extends through the partition wall such that the upstream exhaust chamber communicates with the downstream exhaust chamber.

According to the above aspect, the exhaust gas that has flowed into the upstream exhaust chamber flows into the downstream exhaust chamber through the communication hole, which extends through the partition wall. In this case, after flowing along the outer circumferential face of the flame stabilizer, the exhaust gas strikes the partition wall and flows along the partition wall. The exhaust gas then flows in the depthwise direction of the partition wall (the direction in which the communication hole extends). For this reason, compared to when the exhaust gas flows from the upstream exhaust chamber to the downstream exhaust chamber without changing the direction, the exhaust gas flowing into the gap between the flame stabilizer and the cover takes a more complex route.

Preferably, a flow path cross-sectional area of the exhaust pipe is larger than a flow path cross-sectional area of the upstream exhaust chamber.

According to the above aspect, compared to when the flow path cross-sectional area of the exhaust pipe is smaller than the flow path cross-sectional area of the upstream exhaust chamber, expansion of the exhaust gas in the upstream exhaust chamber is suppressed. For this reason, the decrease in the temperature of the exhaust gas is reduced, and therefore, the efficiency of heat transfer from the exhaust gas to the flame stabilizer is increased.

Preferably, the burner for an exhaust purification device further comprises an ignition portion, which is arranged in the space in the flame stabilizer to ignite the air-fuel mixture. With respect to distances in the axial direction of the flame stabilizer, the distance between the partition portion and the ejection port is shorter than the distance between the ignition portion and the ejection port. According to the above aspect, with respect to distances in the axial direction of the flame stabilizer, compared to when the distance between the partition portion and the ejection port is long, the flame stabilizer has a larger outer circumferential face that defines the upstream exhaust chamber. This facilitates increasing the temperature of the flame stabilizer with the exhaust gas flowing in the upstream exhaust chamber. With this, the temperature of gas in the combustion area is more easily raised by being heated by the flame stabilizer. As a result, the ambient temperature is more easily raised near the ignition portion in the combustion area.

According to another aspect of the present disclosure, the burner further comprises a premixing portion, which is arranged in the space in the flame stabilizer and produces the air-fuel mixture, and an ignition portion, which is arranged in the space in the flame stabilizer and ignites the air-fuel mixture produced in the premixing portion. The distance between the ignition portion and the upstream exhaust chamber is shorter than the distance between the ignition portion and the downstream exhaust chamber.

According to the above aspect, the air-fuel mixture combusted in the combustion area is air-fuel mixture that is mixed in advance in the premixing portion. For this reason, compared to when air-fuel mixture is produced and combusted in the combustion area, the air-fuel mixture is more easily ignited, and the air-fuel mixture is efficiently combusted. Furthermore, since the temperature of the gas is raised near the ignition portion, the exhaust gas is efficiently utilized as heat for reducing production of unburned gas compared to when the temperature of the gas is raised at a distance from the ignition portion. As a result, it is possible to further suppress the discharge of fuel supplied to the combustion area as unburned gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exhaust purification device including a burner for an exhaust purification device according to a first embodiment;

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a graph that shows a relationship between elapsed time from cold start of an engine and an ambient temperature near an ignition point in a combustion area;

FIG. 4 is a schematic view of a burner for an exhaust purification device according to a second embodiment;

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 4; and

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 4.

 MODES FOR CARRYING OUT THE INVENTION First Embodiment

A burner for an exhaust purification device according to a first embodiment of the present disclosure will now be described with reference to FIGS. 1 to 3. First, the general configuration of an exhaust purification device including the burner for an exhaust purification device will be described with reference to FIG. 1.

As shown in FIG. 1, an exhaust purification device 10 for a diesel engine is arranged downstream of an exhaust pipe 11, through which exhaust gas from the engine flows. The exhaust purification device 10 includes a tubular upstream cover 13 and a tubular downstream cover 14, which are coupled to each other. The downstream cover 14 includes a diesel particulate filter 12 (hereinafter, referred to as a DPF 12), to which particulate matter contained in the exhaust gas adsorbs.

The DPF 12 has a honeycomb structure made of, e.g., a porous silicon carbide and captures particulate matter in the exhaust gas with the surface of the inner wall that defines the honeycomb structure. A burner for an exhaust purification device 15 (hereinafter, referred to as a burner 15) is mounted upstream of the DPF 12, and carries out a regeneration process of the DPF 12 by raising the temperature of the exhaust gas flowing into the DPF 12.

The upstream cover 13 is one of the components included in the burner 15, and its circumference wall has a basal end fixed to a basal wall 17 of the flame stabilizer 16. The upstream cover 13 is connected to an exhaust pipe 11, through which the exhaust gas from the engine flows.

The flame stabilizer 16 of the burner 15 has a tubular shape with the basal wall 17, and its circumference wall is surrounded by the upstream cover 13. The flame stabilizer 16 includes a small diameter portion 18 and a large diameter portion 19. The small diameter portion 18 has a smaller diameter than the diameter of the basal wall 17 and is fixed to the basal wall 17. The large diameter portion 19 extends from the distal end of the small diameter portion 18 to an ejection port 16A of the flame stabilizer 16 while increasing its diameter. The flame stabilizer 16 includes a combustion area 20 formed in a space surrounded by the circumference wall of the small diameter portion 18 and the circumference wall of the large diameter portion 19.

An air supply pipe 26 is fixed to the basal wall 17 of the flame stabilizer 16 and guides a portion of intake air that flows through an intake pipe 25 in a state of being compressed by a compressor of a turbocharger as air for combustion to the combustion area 20. An air valve 27 is attached to a portion of an air supply pipe 26. A portion of the intake air flows into the combustion area 20 through the air supply pipe 26 when the air valve 27 is in the open state.

A fuel injection valve 21 is fixed to the basal wall 17 of the flame stabilizer 16 inside a part where the circumference wall of the small diameter portion 18 is fixed to the basal wall 17. The fuel injection valve 21 is supplied with fuel by a fuel pump for supplying fuel to the engine (not shown). A distal end portion of the fuel injection valve 21, which includes an injection port, is arranged in the combustion area 20. The fuel injection valve 21 injects the fuel into the combustion area 20 to supply atomized fuel to the combustion area 20.

A pair of spark plugs 22 is fixed to the basal wall 17 of the flame stabilizer 16 inside a part where the circumference wall of the small diameter portion 18 is fixed to the basal wall 17. The spark plugs 22 are arranged such that ignition portions 22a, which are distal end portions of the spark plugs 22, surround the distal end portion of the fuel injection valve 21. The spark plugs 22 generate sparks in the combustion area 20 to ignite air-fuel mixture of fuel and air for combustion at an ignition point 23. This produces flame F in the combustion area 20.

A annular partition wall 33 is fixed to the upstream cover 13 and the small diameter portion 18. The partition wall 33 is a partition portion that partitions a gap formed between the inner circumferential face of the upstream cover 13 and the outer circumferential face of the flame stabilizer 16 into an upstream exhaust chamber 31 and a downstream exhaust chamber 32. The upstream exhaust chamber 31 is located close to the basal wall 17 (basal end) of the flame stabilizer 16. The downstream exhaust chamber 32 is located close to the ejection port 16A (distal end) of the flame stabilizer 16. In detail, the partition wall 33 projects from the outer circumferential face of the small diameter portion 18 of the flame stabilizer 16 toward the inner circumferential face of the upstream cover 13, and the partition wall 33 is coupled to the inner circumferential face of the upstream cover 13 and the outer circumferential face of the small diameter portion 18. The partition wall 33 is located closer to the distal end of the flame stabilizer 16 (ejection port 16A) than the ignition portions 22a in the axial direction of the flame stabilizer 16. In other words, with respect to distances in the axial direction of the flame stabilizer 16, the distance between the partition wall 33 and the ejection port 16A is shorter than the distance between the ignition portions 22a and the ejection port 16A. The upstream exhaust chamber 31 communicates with the exhaust pipe 11 through an opening 34 formed in the upstream cover 13. The downstream exhaust chamber 32 has an open end located opposite to the partition wall 33. The partition wall 33 includes communication holes 35 formed at predefined intervals in the circumferential direction of the partition wall 33. The communication holes 35 connect the upstream exhaust chamber 31 to the downstream exhaust chamber 32. In other words, after the exhaust gas flowing through the exhaust pipe 11 passes through the upstream exhaust chamber 31, the communication holes 35, the downstream exhaust chamber 32 in order, the exhaust gas flows into the DPF 12. In this case, when the flame F is formed in the combustion area 20, the temperature of exhaust gas is raised by the flame F, and then the exhaust gas flows into the DPF 12.

As shown in FIG. 2, the exhaust pipe 11 is shaped such that piping extending in the radial direction of the upstream cover 13 is offset toward the left of the upstream cover 13 and extends substantially in the tangential direction of the outer surface of the upstream cover 13. For this reason, the exhaust gas flowing into the upstream exhaust chamber 31 from the exhaust pipe 11 partially flows into the downstream exhaust chamber 32 through the communication holes 35 included in the partition wall 33 while the exhaust gas flowing in the upstream exhaust chamber 31 forms a swirling flow that swirls around the small diameter portion 18 of the flame stabilizer 16 as illustrated by the arrows shown in FIG. 2.

The upstream exhaust chamber 31 is formed such that the swirling flow of the exhaust gas has a flow path area smaller than the flow path area of the exhaust pipe 11. In other words, in FIG. 1, a portion surrounded by the small diameter portion 18, the partition wall 33, the upstream cover 13, and the basal wall 17 is formed so as to have an area smaller than the flow path area of the exhaust pipe 11.

Operation of the burner 15 configured as above will now be described with reference to FIG. 3.

In the burner 15, the gap between the upstream cover 13 and the flame stabilizer 16 is partitioned by the partition wall 33 into the upstream exhaust chamber 31 and the downstream exhaust chamber 32. The partition wall 33 includes the communication holes 35, which connect the upstream exhaust chamber 31 to the downstream exhaust chamber 32. In addition, the exhaust pipe 11 communicates with the upstream exhaust chamber 31.

According to this configuration, the exhaust gas which has flowed through the exhaust pipe 11 passes through the upstream exhaust chamber 31, the communication holes 35, and the downstream exhaust chamber 32. After that, the exhaust gas flows into the DPF 12. For this reason, compared to when the partition wall 33 is not formed, the exhaust gas that has flowed into the gap between the upstream cover 13 and the flame stabilizer 16 takes a more complex route to flow out of the gap, and therefore, the possibility for the exhaust gas to contact the circumference wall of the flame stabilizer 16 is increased. This facilitates heating the flame stabilizer 16 with heat transferred from the exhaust gas and raising the temperature of gas in the combustion area 20 heated with the flame stabilizer 16.

In other words, even when the engine is cold, the temperature of the flame stabilizer 16 and the temperature of the gas in the combustion area 20 are promptly raised. Furthermore, after raising the temperatures of the flame stabilizer 16 and the combustion area 20, it is easier to maintain the raised temperatures. This facilitates vaporization of the fuel in the combustion area 20 when the engine is cold, thereby reducing the fuel discharged as unburned gas after being supplied to the combustion area 20.

In the burner 15, the exhaust pipe 11 is, as shown in FIG. 2, one pipe that is offset toward the left of the upstream cover 13 and extends substantially in the tangential direction of the outer circumferential face of the upstream cover 13. For this reason, the exhaust gas flowing into the upstream exhaust chamber 31 forms a swirling flow that swirls around the small diameter portion 18. According to this configuration, compared to when a plurality of exhaust gas pipes is connected to the upstream cover 13, it is easier to generate a swirling flow in the upstream exhaust chamber 31. In addition, compared to when the exhaust gas flowing into the upstream exhaust chamber 31 forms two flows divided by the flame stabilizer 16 by striking the circumference wall of the flame stabilizer 16, it is easier for the exhaust gas to contact the entire surface of the portion of the circumference wall of the small diameter portion 18 that defines the upstream exhaust chamber 31. As a result, heat is efficiently transferred from the exhaust gas to the flame stabilizer 16.

In the burner 15, the exhaust pipe 11 is attached to the upstream cover 13 at a position such that a swirling flow is generated in the upstream exhaust chamber 31. For this reason, for example, compared to when a guide plate for guiding the exhaust gas flowing into the upstream exhaust chamber 31 is arranged in the upstream exhaust chamber 31 to generate a swirling flow in the upstream exhaust chamber 31, a simpler configuration is employed to allow the exhaust gas to contact the entire surface of the portion of the circumference wall of the small diameter portion 18 that defines the upstream exhaust chamber 31.

In the burner 15, the flow path cross-sectional area of the exhaust pipe 11 is larger than the flow path cross-sectional area in the upstream exhaust chamber 31. For this reason, compared to when the flow path cross-sectional area of the exhaust pipe 11 is smaller than the flow path cross-sectional area of the upstream exhaust chamber 31, the volume of the upstream exhaust chamber 31 in the same flow path length is smaller, and therefore, expansion of the exhaust gas in the upstream exhaust chamber 31 is suppressed. This reduces the decrease in the temperature of the exhaust gas flowing in the upstream exhaust chamber 31, thereby increasing the efficiency of heat transfer from the exhaust gas to the flame stabilizer 16.

In the burner 15, the partition wall 33 is arranged closer to the distal end of the flame stabilizer 16 than the ignition portions 22a. For this reason, compared to when the partition wall 33 is arranged closer to the basal wall 17 of the flame stabilizer 16 than the ignition portions 22a, the circumference wall of the flame stabilizer 16 that defines the upstream exhaust chamber 31 is enlarged so that the circumference wall surrounds the ignition point 23. As a result, the temperature of the flame stabilizer 16 is more easily raised with the exhaust gas flowing in the upstream exhaust chamber 31, and the ambient temperature is more easily raised near the ignition point 23 via the flame stabilizer 16.

FIG. 3 shows a graph that shows a relationship between elapsed time t from cold start of the engine and an ambient temperature T in the combustion area. In FIG. 3, an example indicated by a solid line represents the aforementioned burner 15. A comparison example indicated by a long dashed double-short dashed line represents a burner for an exhaust purification device in which the partition wall 33 is not formed and the exhaust pipe 11 is connected to the upstream cover 13 so as to face the large diameter portion 19. The ambient temperature T is a temperature near the ignition point 23, and an ignitable temperature T1 is a temperature at which mixture of fuel and air can be ignited.

As shown in FIG. 3, in the burner 15 of the example, the ambient temperature T near the ignition point 23 reaches the ignitable temperature T1 in elapsed time t1. In the burner for an exhaust purification device of the comparison example, the ambient temperature T near the ignition point 23 reaches the ignitable temperature T1 in elapsed time t2, which is longer than the elapsed time t1. Thus, it is recognized that the burner 15 of the example has the ambient temperature T near the ignition point 23 to reach the ignitable temperature T1 earlier than the burner of the comparison example.

As described above, the burner 15 according to the first embodiment provides the following advantages.

(1) Even in cold, the temperature of the flame stabilizer 16 and the temperature of gas in the combustion area 20 heated by the flame stabilizer 16 are promptly raised. In addition, after the temperature of the flame stabilizer 16 is raised, it is easier to maintain the raised temperatures of the flame stabilizer 16 and the gas in the combustion area 20. This reduces fuel discharged as unburned gas after being supplied to the combustion area 20.

(2) Since the swirling flow that swirls around the flame stabilizer 16 is generated in the upstream exhaust chamber 31, it is easier for the exhaust gas to contact the entire surface of the portion of the circumference wall of the flame stabilizer 16 that defines the upstream exhaust chamber 31, and heat is efficiently transferred from the exhaust gas to the flame stabilizer 16.

(3) The exhaust pipe 11 is attached to the upstream cover 13 at the position such that a swirling flow is generated in the upstream exhaust chamber 31. Thus, compared to when a member such as a guide plate is arranged in the upstream exhaust chamber 31, a simpler configuration can be employed to allow the exhaust gas to contact the entire surface of the portion of the circumference wall of the flame stabilizer 16 that defines the upstream exhaust chamber 31.

(4) The exhaust gas flowing into the upstream exhaust chamber 31 flows along the partition wall 33, and then flows into the downstream exhaust chamber 32 through the communication holes 35 of the partition wall 33. In this case, in order to flow from the upstream exhaust chamber 31 to the downstream exhaust chamber 32, the exhaust gas needs to change the flowing direction so as to flow in the depthwise direction of the partition wall 33 after flowing along the face of the partition wall 33. For this reason, compared to when the exhaust gas flows from the upstream exhaust chamber 31 to the downstream exhaust chamber 32 without changing the flowing direction of the exhaust gas, the exhaust gas takes a more complex route, and therefore, the efficiency of heat transfer from the exhaust gas to the flame stabilizer 16 is increased.

(5) The flow path cross-sectional area of the exhaust pipe 11 is larger than the flow path cross-sectional area of the upstream exhaust chamber 31. Thus, compared to when the flow path cross-sectional area of the exhaust pipe 11 is smaller than the flow path cross-sectional area of the upstream exhaust chamber 31, the volume in the upstream exhaust chamber 31 per the same flow path length is smaller than the volume in the exhaust pipe 11, and therefore, expansion of exhaust gas in the upstream exhaust chamber 31 is suppressed. Accordingly, heat is efficiently transferred from the exhaust gas to the flame stabilizer 16.

(6) The partition wall 33 is arranged closer to the ejection port 16A of the flame stabilizer 16 than the ignition portions 22a. Thus, compared to when the partition wall 33 is arranged closer to the basal wall 17 of the flame stabilizer 16 than the ignition portions 22a, it is easier to raise the temperature of the flame stabilizer 16. As a result, the temperature of gas in the combustion area 20 is more easily raised by being heated by the flame stabilizer 16.

Second Embodiment

A burner for an exhaust purification device according to a second embodiment of the present disclosure will now be described with reference to FIGS. 4 to 6. The burner for an exhaust purification device 50 according to the second embodiment is primarily configured in the same way as the burner for an exhaust purification device according to the first embodiment. For this reason, in the second embodiment, parts different from the first embodiment will be described in detail, and parts with similar functions to those in the first embodiment will not be described in detail by assigning like reference characters.

As shown in FIG. 4, in the burner for an exhaust purification device 50 (hereinafter, simply referred to as a burner 50), the flame stabilizer 16 has a cylindrical tube shape that has a bottom and is opened toward the DPF 12. The basal wall 17 in the flame stabilizer 16 closes the opening at the basal end of the small diameter portion 18 in the flame stabilizer 16 and extends radially outward from the portion fixed to the small diameter portion 18.

A tubular outer tube 51 is fixed to the edge of the basal wall 17 of the flame stabilizer 16. The outer tube 51 extends from the edge of the basal wall 17 toward the DPF 12, and surrounds the entire small diameter portion 18 of the flame stabilizer 16. The distal end portion of the outer tube 51, which is the one of two ends that is located close to the DPF 12, is fixed to an annular closing wall 53. The distal end portion of the outer tube 51 is arranged closer to the basal wall 17 than the ejection port 16A of the flame stabilizer 16. An area between the outer circumferential face of the small diameter portion 18 and the inner circumferential face of the outer tube 51 is sandwiched and closed by the basal wall 17 and the closing wall 53.

The closing wall 53 has an outer circumferential edge fixed to the tubular upstream cover 13. The upstream cover 13 extends from the outer circumferential edge of the closing wall 53 toward the DPF 12 and surrounds the entire large diameter portion 19 of the flame stabilizer 16. The gap between the outer circumferential face of the large diameter portion 19 and the inner circumferential face of the upstream cover 13 is opened toward the DPF 12. The upstream cover 13 serves as a tubular cover that surrounds the flame stabilizer 16.

The partition wall 33 is arranged in the gap between the outer circumferential face of the large diameter portion 19 and the inner circumferential face of the upstream cover 13. The annular partition wall 33 resides along a periphery of the large diameter portion 19. The partition wall 33 partitions the gap between the outer circumferential face of the large diameter portion 19 and the inner circumferential face of the upstream cover 13 in the axial direction of the flame stabilizer 16 into the upstream exhaust chamber 31 and the downstream exhaust chamber 32. The upstream exhaust chamber 31 is a space connected to the exhaust pipe 11, and the downstream exhaust chamber 32 is a space connected to the ejection port 16A. The partition wall 33 has the communication holes 35, which extend through the partition wall 33 to connect the upstream exhaust chamber 31 to the downstream exhaust chamber 32.

As shown in FIG. 5, the outer circumferential face of the outer tube 51 is connected to the air supply pipe 26, and a guide plate 54 is arranged on the inner circumferential face of the outer tube 51 near the outlet of the air supply pipe 26. The guide plate 54 is positioned to be separated from the outlet of the air supply pipe 26 and to face the outlet. The area between the outer circumferential face of the small diameter portion 18 and the outer tube 51 is an introduction flow path 52. The air for combustion that enters the introduction flow path 52 from the air supply pipe 26 is guided by the guide plate 54, and turns along the outer circumferential face of the small diameter portion 18.

The small diameter portion 18 has an end (basal end) fixed to the basal wall 17 and has a plurality of first introduction ports 55 extending through the small diameter portion 18 in a portion located near the basal end. The first introduction ports 55 line up at equal intervals in the circumferential direction of the small diameter portion 18. The space surrounded by the flame stabilizer 16 is the combustion area 20, and the first introduction ports 55 lead a portion of the air for combustion that has entered the introduction flow path 52 to the inside of the flame stabilizer 16.

The portion of the small diameter portion 18 that is located closer to the ejection port 16A than the first introduction ports 55 includes a plurality of second introduction ports 56, which extends through the small diameter portion 18. The second introduction ports 56 line up at equal intervals in the circumferential direction of the flame stabilizer 16. The second introduction ports 56 lead the air for combustion that has entered the introduction flow path 52 to the inside of the flame stabilizer 16.

As shown in FIG. 6, a raised piece 57 is formed at the opening edge of each first introduction port 55 by cutting a portion of the circumference wall of the small diameter portion 18 and raising the portion inward. The raised piece 57 guides air for combustion from the first introduction port 55 to the inside of the flame stabilizer 16, and swirls the air for combustion inside the flame stabilizer 16. The raised piece 57 swirls the air for combustion in the swirling direction of the air for combustion in the introduction flow path 52 inside the flame stabilizer 16.

A fuel supply unit 58, which supplies fuel to the inside of the flame stabilizer 16, is fixed to the basal wall 17. The distal end portion of the fuel supply unit 58, which includes a supply port, is arranged inside the flame stabilizer 16. The fuel supply unit 58 is connected to a fuel pump for supplying fuel to the engine through a fuel valve. Fuel is sent to the fuel supply unit 58 by the fuel pump when the fuel valve is opened. The fuel sent to the fuel supply unit 58 is vaporized in the fuel supply unit 58 and injected to the inside of the flame stabilizer 16.

A coupling portion 60 is coupled to the portion of the inner circumferential face 16b of the small diameter portion 18 that resides between the first introduction ports 55 and the second introduction ports 56 in the flame stabilizer 16. The coupling portion 60 includes a flange 61, an insertion portion 62, and a radially-narrowed portion 63. The flange 61, the insertion portion 62, and the radially-narrowed portion 63 are integrated.

The flange 61 is annular and resides along the inner circumferential face 16b of the small diameter portion 18 and fixed to the entire inner circumferential face 16b of the small diameter portion 18 in the circumferential direction of the inner circumferential face 16b. In the space surrounded by the flame stabilizer 16, the flange 61 and the basal wall 17 define a first mixing chamber 71.

Air for combustion enters the first mixing chamber 71 through the first introduction ports 55, and fuel enters the first mixing chamber 71 from the fuel supply unit 58. The air for combustion swirls around the axis of the flame stabilizer 16 and the fuel is injected toward the center of the swirling air for combustion so that the air for combustion and the fuel are mixed in the first mixing chamber 71.

The insertion portion 62 has a tubular shape extending from the radially-narrowed portion 63 toward the ejection port 16A and has a smaller diameter than the inner diameter of the flange 61. The radially-narrowed portion 63 has a tubular truncated cone shape extending from the inner circumferential edge of the flange 61 toward the ejection port 16A and couples the flange 61 with the insertion portion 62.

A tubular first inner tube 64 is inserted into the insertion portion 62. The basal end of the first inner tube 64, which is the one of two ends that is located close to the basal wall 17, is joined to the insertion portion 62. The flange 61 of the coupling portion 60 is coupled to the inner circumferential face 16b of the flame stabilizer 16, and the insertion portion 62 of the coupling portion 60 is coupled to the outer circumferential face 64a of the first inner tube 64. The coupling portion 60 closes an area between the inner circumferential face 16b of the flame stabilizer 16 and the outer circumferential face 64a of the first inner tube 64. The distal end of the first inner tube 64, which is the one of two ends that is located close to the ejection port 16A, is opened.

A tubular second inner tube 65 is arranged around the first inner tube 64 to surround the first inner tube 64. The distal end portion of the first inner tube 64 is surrounded by the second inner tube 65. The end (distal end) of the second inner tube 65 that is located close to the ejection port 16A is positioned closer to the ejection port 16A than the distal end of the first inner tube 64. The end (basal end) of the second inner tube 65 that is located close to the basal wall 17 is positioned closer to the ejection port 16A than the basal end of the first inner tube 64.

The opening at the distal end of the second inner tube 65 is closed by a closing wall 66. The basal end of the second inner tube 65 is fixed to the inner circumferential face of the small diameter portion 18 with an annular support plate 67.

The inner circumferential edge of the support plate 67 is fixed to the entire outer circumferential face 65a of the second inner tube 65. The outer circumferential edge of the support plate 67 is fixed to the entire inner circumferential face 16b of the flame stabilizer 16. A plurality of communication passages 68 extends through the support plate 67 so that the space located closer to the ejection port 16A than the support plate 67 communicates with the space located closer to the basal wall 17 than the support plate 67. A wire mesh 69, which covers the communication passages 68, is attached to the support plate 67.

The space surrounded by the inner circumferential face of the first inner tube 64 in the space surrounded by the flame stabilizer 16 forms a second mixing chamber 72. The air-fuel mixture coming out of the first mixing chamber 71 enters the second mixing chamber 72.

In the space surrounded by the flame stabilizer 16, the space that is located closer to the ejection port 16A than the second mixing chamber 72 and surrounded by the inner circumferential face of the second inner tube 65 and the closing wall 66 forms a third mixing chamber 73. The air-fuel mixture coming out of the second mixing chamber 72 enters the third mixing chamber 73.

In the space surrounded by the flame stabilizer 16, the area between the outer circumferential face of the first inner tube 64 and the inner circumferential face of the second inner tube 65 forms a fourth mixing chamber 74. The air-fuel mixture coming out of the third mixing chamber 73 enters the fourth mixing chamber 74.

In the space surrounded by the flame stabilizer 16, the area surrounded by the inner circumferential face 16b of the flame stabilizer 16, the support plate 67, and the coupling portion 60 forms a fifth mixing chamber 75. The air-fuel mixture coming out of the fourth mixing chamber 74 enters the fifth mixing chamber 75.

The spark plug 22 is fixed to the outer circumferential face of the outer tube 51. The ignition portion 22a of the spark plug 22 projects inward of the flame stabilizer 16 from the inner circumferential face 16b of the flame stabilizer 16. The ignition portion 22a is arranged in the space between the inner circumferential face of the small diameter portion 18 and the outer circumferential face 65a of the second inner tube 65 and positioned closer to the ejection port 16A than the support plate 67 in the axial direction of the flame stabilizer 16. The distance between the ignition portion 22a and the upstream exhaust chamber 31 in the axial direction of the flame stabilizer 16 is shorter than the distance between the ignition portions 22a and the downstream exhaust chamber 32.

The first mixing chamber 71, the second mixing chamber 72, the third mixing chamber 73, the fourth mixing chamber 74, and the fifth mixing chamber 75 form one premixing chamber 70, which serves as a premixing portion for producing air-fuel mixture. The space between the inner circumferential face 16b of the flame stabilizer 16 and the outer circumferential face 65a of the second inner tube 65 and the space located closer to the ejection port 16A than the closing wall 66 in the flame stabilizer 16 form the combustion area 20. The premixing chamber 70 and the combustion area 20 are comparted with a compartment portion including the second inner tube 65, the closing wall 66, and the support plate 67. The air-fuel mixture produced in the premixing chamber 70 enters the combustion area 20 through the communication passages 68 and is then ignited by the ignition portion 22a.

As described above, the burner 50 according to the second embodiment provides the following advantages in addition to the above advantages (1) to (5).

(7) Before entering the combustion area 20 to be combusted, fuel is mixed with air for combustion in advance in the premixing chamber 70. For this reason, compared to the configuration in which air-fuel mixture is not produced in the premixing chamber 70, it is easier to ignite the air-fuel mixture, and the air-fuel mixture is efficiently combusted. As a result, it is possible to further suppress the discharge of fuel supplied to the combustion area as unburned gas.

(8) The distance (shortest distance) between the ignition portions 22a and the upstream exhaust chamber 31 is shorter than the distance (shortest distance) between the ignition portion 22a and the downstream exhaust chamber 32. Further, the temperature of the exhaust gas flowing in the upstream exhaust chamber 31 is transferred via the flame stabilizer 16. This raises the temperature of gas near the ignition portion 22a. Thus, compared to the configuration in which the temperature of gas is raised at a distance from the ignition portions 22a, the exhaust gas is efficiently utilized as heat for reducing production of unburned gas.

(9) Before entering the first mixing chamber 71, the air for combustion flowing in the introduction flow path 52 contacts the outer circumferential face of the flame stabilizer 16 and is heated with the outer circumferential face. As a result, it is easier to ignite the air-fuel mixture, and the air-fuel mixture is efficiently combusted.

(10) The outer circumferential face of the large diameter portion 19 defines the upstream exhaust chamber 31. Thus, compared to the configuration in which the outer circumferential face of the small diameter portion 18 defines the upstream exhaust chamber 31, the contact area of the outer circumferential face of the flame stabilizer 16 with the exhaust gas is enlarged.

The first and second embodiments may be modified in the following forms.

In the first embodiment, the partition wall 33 may be arranged closer to the basal wall 17 of the flame stabilizer 16 than the ignition portions 22a. In other words, with respect to distances in the axial direction of the flame stabilizer 16, the distance between the partition wall 33 and the ejection port 16A may be longer than the distance between the ignition portions 22a and the ejection port.

In the second embodiment, the second introduction ports 56 may be omitted. In other words, air for combustion may be supplied to the combustion area 20 only through the premixing chamber 70.

In the second embodiment, the air supply pipe 26 may be connected to the basal wall 17. In other words, air for combustion may enter the premixing chamber 70 without traveling around the flame stabilizer 16.

In the second embodiment, the compartment portion, which comparts the premixing chamber 70 and the combustion area 20, may be, e.g., a flat plate arranged inside the flame stabilizer 16 to be orthogonal to the axial direction of the stabilizer 16. In other words, the compartment portion, which comparts the premixing chamber 70 and the combustion area 20, may be modified as long as it is configured as a member that partitions a space defined by the flame stabilizer 16 into a space producing air-fuel mixture and a space for igniting the air-fuel mixture (combustion area).

In the configuration in which the compartment portion includes the coupling portion 60, the first inner tube 64, the second inner tube 65, the closing wall 66, and the support plate 67, a passage that connects the space for producing air-fuel mixture and the space for igniting the air-fuel mixture (combustion area) is complicated. For this reason, in view of mixing fuel and air for combustion to a great extent, it is preferable for the compartment portion to include the coupling portion 60, the first inner tube 64, the second inner tube 65, the closing wall 66, and the support plate 67.

The distance between the ignition portion 22a and the upstream exhaust chamber 31 may be equal to the distance between the ignition portion 22a and the downstream exhaust chamber 32, or may be longer than the distance between the ignition portion 22a and the downstream exhaust chamber 32.

For example, in the axial direction of the flame stabilizer 16, the ignition portion 22a may be arranged midway between the upstream exhaust chamber 31 and the downstream exhaust chamber 32. In this case, the upstream exhaust chamber 31 and the downstream exhaust chamber 32 may be partitioned by two or more partition walls. In the configuration that partitions with one partition wall, the ignition portion 22a may be arranged inside the flame stabilizer 16 through the partition wall. With this configuration, the distance between the ignition portion 22a and the upstream exhaust chamber 31 is set to be equal to the distance between the ignition portion 22a and the downstream exhaust chamber 32 or to be longer than the distance between the ignition portion 22a and the downstream exhaust chamber 32.

For example, the upstream exhaust chamber 31 may be defined by a partition wall and another wall different from the partition wall and arranged closer to the ejection port 16A than the downstream exhaust chamber 32. In this case, piping that connects the downstream exhaust chamber 32 and the ejection port 16A may be modified as long as it is configured to be separately provided outside of the cover so that the exhaust gas of the downstream exhaust chamber 32 travels outside the cover and flows to the ejection port 16A.

For example, the partition wall may extend in the direction that crosses the circumferential direction of the flame stabilizer 16, and partition the upstream exhaust chamber 31 off from the downstream exhaust chamber 32 in the direction that crosses the circumferential direction of the flame stabilizer 16. With this configuration, in the radial direction of the flame stabilizer 16, the upstream exhaust chamber 31 and the downstream exhaust chamber 32 are arranged outside of the ignition portion 22a. For this reason, the distance between the ignition portion 22a and the upstream exhaust chamber 31 is equal to the distance between the ignition portion 22a and the downstream exhaust chamber 32, or longer than the distance between the ignition portion 22a and the downstream exhaust chamber 32.

In other words, the partition portion may be modified as long as it is configured to partition the gap between the outer circumferential face of the flame stabilizer and the inner circumferential face of the cover into the upstream exhaust chamber 31 connected to the exhaust pipe and the downstream exhaust chamber 32 connected to the ejection port.

The flow path cross-sectional area of the exhaust pipe 11 may be less than or equal to the flow path cross-sectional area of the upstream exhaust chamber 31.

The configuration for generating a swirling flow in the upstream exhaust chamber 31 is not limited to the exhaust pipe 11 that is offset from the upstream cover 13, but may be formed, e.g., by arranging a guide plate for guiding the exhaust gas flowing into the upstream exhaust chamber 31 in the upstream exhaust chamber 31. According to the first and second embodiments, the upstream exhaust chamber 31 is a continuous annular space. However, another configuration for generating a swirling flow in the upstream exhaust chamber 31 may be employed, e.g., by forming the upstream exhaust chamber 31 with a discontinuous space by a stopper arranged near the portion that connects the upstream cover 13 and the exhaust pipe 11.

In the upstream exhaust chamber 31, for example, the exhaust pipe 11 may extend in the radial direction of the outer surface of the upstream cover 13 so that the exhaust gas flowing from the exhaust pipe 11 is divided by the flame stabilizer 16 to form two flows. In addition, a plurality of exhaust pipes 11 may be connected to the upstream exhaust chamber 31 so that the exhaust gas flowing from the exhaust pipes 11 flows in different directions. In other words, this may be modified as long as it is configured that the exhaust gas of the exhaust pipes 11 passes through the upstream exhaust chamber 31, the communication holes 35, and the downstream exhaust chamber 32 in order.

The communication holes 35 may be omitted, and the partition portion may be configured such that the partition wall 33 is separated from the inner surface of the upstream cover 13. The communication holes 35 may be omitted, and the partition portion may be configured such that the partition wall 33 is separated from the circumference wall of the flame stabilizer 16. The partition portion may be configured to include two or more partition walls 33 configured as above. The plurality of communication holes 35 may be omitted from the partition wall 33, and the upstream exhaust chamber 31 and the downstream exhaust chamber 32, which are partitioned by the partition wall 33, may be connected by, e.g., other piping arranged outside of the upstream cover 13.

Not limited to piping for exhaust gas from the engine, the exhaust pipe 11 may be piping through which the exhaust gas that has passed through the DPF 12 flows.

The flame stabilizer 16 may have a tubular shape that has a constant diameter over the entire flame stabilizer in the axial direction. In other words, the flame stabilizer 16 may be modified as long as it is configured to have a tubular shape with the ejection port 16A for ejecting combustion gas.

The fuel injected from the fuel injection valve 21 may be supplied from a common rail, not a fuel pump. A fuel pump that supplies fuel only to the fuel injection valve 21 may be included.

In the first embodiment, for example, the fuel injection valve 21 may be configured to supply fuel that is vaporized in advance to the combustion area 20.

In the second embodiment, the fuel supply unit 58 may inject fuel that is not vaporized to the first mixing chamber 71.

Not limited to a spark plug, a glow plug, a laser spark device, or a plasma spark device may be used to ignite air-fuel mixture. One of those or two or more of those may be used to ignite the air-fuel mixture.

Not limited to the intake air flowing through the intake pipe 25, air for combustion may be air flowing through piping connected to the air tank of a brake or air supplied by a blower for the burner for an exhaust purification device.

The engine with the burner for an exhaust purification device may be a gasoline engine.

The exhaust gas with the temperature raised by the burner for an exhaust purification device is used for raising the temperature of a catalyst, not limited to a regeneration process of the DPF 12.

DESCRIPTION OF THE REFERENCE NUMERALS

    • F: flame, T: ambient temperature, T1: ignitable temperature, t, t1, t2: elapsed time, 10: exhaust purification device, 11: exhaust pipe, 12: diesel particulate filter, 13: upstream cover, 14: downstream cover, 15: burner for an exhaust purification device, 16: flame stabilizer, 16A: ejection port, 17: basal wall, 18: small diameter portion, 19: large diameter portion, 20: combustion area, 21: fuel injection valve, 22: spark plug, 22a: ignition portion, 23: ignition point, 25: intake pipe, 26: air supply pipe, 27: air valve, 31: upstream exhaust chamber, 32: downstream exhaust chamber, 33: partition wall, 34: opening, 35: communication hole, 50: burner for an exhaust purification device, 51: outer tube, 52: introduction flow path, 53: closing wall, 54: guide plate, 55: first introduction port, 56: second introduction port, 57: raised piece, 58: fuel supply unit, 60: coupling portion, 61: flange, 62: insertion portion, 63: radially-narrowed portion, 64: first inner tube, 65: second inner tube, 66: closing wall, 67: support plate, 68: communication passage, 69: wire mesh, 70: premixing chamber, 71: first mixing chamber, 72: second mixing chamber, 73: third mixing chamber, 74: fourth mixing chamber, and 75: fifth mixing chamber.

Claims

1. A burner for an exhaust purification device, comprising:

a tubular flame stabilizer having a space including a combustion area, in which air-fuel mixture of fuel and air is combusted, an ejection port for ejecting combustion gas, a small diameter portion, and a large diameter portion having an inner diameter larger than the small diameter portion;
a tubular cover that surrounds the flame stabilizer, wherein a gap is formed between an inner circumference face of the cover and an outer circumference face of the flame stabilizer;
an exhaust pipe connected to the cover to deliver exhaust gas into the gap; and
a partition portion arranged in the gap to partition the gap into an upstream exhaust chamber and a downstream exhaust chamber, wherein the partition portion is arranged between an outer circumference face of the large diameter portion and the inner circumference face of the cover in the gap, wherein
the upstream exhaust chamber is connected to the exhaust pipe and the downstream exhaust chamber, and
the downstream exhaust chamber is connected to the ejection port of the flame stabilizer.

2. The burner for an exhaust purification device according to claim 1, wherein

the flame stabilizer is shaped as a cylindrical tube, and
the exhaust pipe extends in the tangential direction of the outer circumferential face of the flame stabilizer.

3. The burner for an exhaust purification device according to claim 2, wherein the exhaust pipe connects to an outer circumferential face of the cover at one location.

4. The burner for an exhaust purification device according to claim 1, wherein

the partition portion is configured to:
protrude from the outer circumferential face of the flame stabilizer toward the inner circumferential face of the cover;
be coupled to the outer circumferential face of the flame stabilizer and the inner circumferential face of the cover; and
be a partition wall that partitions the gap into the upstream exhaust chamber and the downstream exhaust chamber, and
the partition wall includes a communication hole that extends through the partition wall such that the upstream exhaust chamber communicates with the downstream exhaust chamber.

5. The burner for an exhaust purification device according to claim 1, wherein a flow path cross-sectional area of the exhaust pipe is larger than a flow path cross-sectional area of the upstream exhaust chamber.

6. The burner for an exhaust purification device according to claim 1, further comprising an ignition portion, which is arranged in the space in the flame stabilizer to ignite the air-fuel mixture,

wherein with respect to distances in the axial direction of the flame stabilizer, a distance between the partition portion and the ejection port is shorter than a distance between the ignition portion and the ejection port.

7. The burner for an exhaust purification device according to claim 1, further comprising:

a premixing portion, which is arranged in the space in the flame stabilizer and produces the air-fuel mixture; and
an ignition portion, which is arranged in the space in the flame stabilizer and ignites the air-fuel mixture produced in the premixing portion,
wherein a distance between the ignition portion and the upstream exhaust chamber is shorter than a distance between the ignition portion and the downstream exhaust chamber.
Patent History
Publication number: 20150082777
Type: Application
Filed: Apr 24, 2013
Publication Date: Mar 26, 2015
Inventors: Ichiro Tsumagari (Hino-shi), Ryo Shibuya (Hino-shi), Atsushi Koide (Miyoshi-shi)
Application Number: 14/396,441
Classifications
Current U.S. Class: Exhaust Gas Or Exhaust System Element Heated, Cooled, Or Used As A Heat Source (60/320); By Sorber Or Mechanical Separator (60/311)
International Classification: F01N 3/025 (20060101);