JP5648315B2 - Fuel pool prevention mechanism and engine system - Google Patents

Description

  The present invention relates to a fuel pool prevention mechanism and an engine system.

Fine particles (particulate matter) are contained in exhaust gas such as diesel engines. In recent years, a filter (DPF) for removing particulates in exhaust gas has been installed in vehicles equipped with diesel engines, etc., because there is concern about the environmental impact of releasing the particulates into the atmosphere. Has been.
This filter is formed of ceramics or the like, which is a porous body having a plurality of pores smaller than the fine particles, and collects the fine particles by preventing the fine particles from passing therethrough.

However, when such a filter is used for a long time, the collected fine particles are accumulated and the filter becomes clogged.
In order to prevent such clogging of the filter, for example, as disclosed in Patent Document 1, a method of burning and removing particulates collected in the filter by supplying a high-temperature gas to the filter is known. It is used.

  Specifically, in Patent Document 1, a burner is installed between a diesel engine and a filter, and a high-temperature gas (combustion gas) is generated by burning an air-fuel mixture in which exhaust gas and fuel are mixed. The particulates are burned by supplying to the filter.

JP-A-8-260944

  Incidentally, an oxidation catalyst for oxidizing the exhaust gas from the diesel engine is usually disposed between the diesel engine and the filter. Furthermore, the burner is disposed upstream of the oxidation catalyst, and the high-temperature gas generated by the burner is supplied to the filter via the oxidation catalyst.

  And the hot gas produced by the burner typically contains a lot of unburned fuel. This unburned fuel is normally burned by an oxidation catalyst. However, particularly when the pipe from the burner to the oxidation catalyst is lower in temperature than the high-temperature gas, unburned fuel contained in the high-temperature gas may condense and liquid fuel may accumulate in the pipe. . When liquid fuel is accumulated in the pipe in this way, the liquid fuel accumulated when the pipe temperature rises or the like is ignited, and unnecessary combustion gas is supplied to the oxidation catalyst. Inconveniences such as accelerated deterioration will occur.

  The phenomenon that the unburned fuel contained in the high-temperature gas generated by the burner is condensed and accumulated in the cooled pipe is not a phenomenon that occurs only when the burner is installed on the upstream side of the oxidation catalyst. That is, there is a possibility that liquid fuel may accumulate in all of the exhaust gas exhaust pipes generated by the burner.

  The present invention has been made in view of the above-described problems, and an object thereof is to prevent liquid fuel from accumulating in the middle of a discharge pipe for combustion gas generated by a burner.

  The present invention adopts the following configuration as means for solving the above-described problems.

  A first invention is a fuel pool prevention mechanism, which is disposed in the middle of a discharge pipe for combustion gas generated by a burner and forms a shear flow in the discharge pipe, thereby collecting liquid in the middle of the discharge pipe. A configuration in which atomization means for atomizing the fuel is provided is adopted.

  According to a second invention, in the first invention, the atomization means includes a projecting portion projecting in the middle of the discharge pipe.

  According to a third invention, in the first or second invention, the atomization means is provided only in a lower region in the discharge pipe.

  A fourth invention is the invention according to any one of the first to third inventions, wherein the atomizing means disperses the liquid fuel flowing toward the shear flow forming region in a direction perpendicular to the flow direction. Adopting a configuration comprising

  According to a fifth aspect of the invention, there is provided an internal combustion engine, an oxidation catalyst for oxidizing exhaust gas discharged from the internal combustion engine, a filter for collecting particulates contained in the exhaust gas that has passed through the oxidation catalyst, and the internal combustion engine And a burner disposed between the oxidation catalyst and a fuel pool prevention mechanism according to any one of the first to fourth aspects of the present invention in the middle of a pipe connecting the burner and the oxidation catalyst Adopting a configuration comprising

According to the present invention, a shear flow is formed in the combustion gas discharge pipe by the atomization means. As a result, the liquid fuel collected in the discharge pipe is exposed to the shear flow and atomized, and is carried on the flow in the discharge pipe to the downstream side, so that a large amount of liquid fuel is accumulated in the discharge pipe. Can be prevented.
Therefore, according to the present invention, it is possible to prevent liquid fuel from accumulating in the middle of the exhaust gas discharge pipe generated by the burner.

1 is a system block diagram showing a schematic configuration of an engine system in a first embodiment of the present invention. It is the sectional view on the AA line of FIG. It is a schematic diagram for demonstrating the function of the fuel pool prevention mechanism with which the engine system in 1st Embodiment of this invention is provided. It is an enlarged view in the same cut surface as FIG. 1 of 2nd piping in 2nd Embodiment of this invention. It is the BB sectional view taken on the line of FIG. It is an enlarged view in the same cut surface as FIG. 1 of 2nd piping in 3rd Embodiment of this invention.

  Hereinafter, an embodiment of a fuel pool prevention mechanism and an engine system according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

(First embodiment)
FIG. 1 is a system block diagram showing a schematic configuration of an engine system S1 in the present embodiment. As shown in this figure, the engine system S1 in this embodiment includes a diesel engine 1 (internal combustion engine), a burner 2, a DOC (Diesel Oxidation Catalyst) 3 (oxidation catalyst), and a DPF (Diesel Particulate Filter) 4 ( Filter), discharge pipe 5, and fuel pool prevention mechanism 6 (atomization means).

  The diesel engine 1 is mounted on a vehicle or the like as a power source, and ignites the air-fuel mixture and takes out its explosive force as rotational power. The diesel engine 1 discharges the exhaust gas X generated by burning the air-fuel mixture to the outside.

  The burner 2 generates a high-temperature gas (combustion gas) by burning an air-fuel mixture of fuel and oxidant (air or exhaust gas X), and supplies this high-temperature gas into the exhaust gas X flow to generate DPF 3. To supply. The burner 2 is disposed between the diesel engine 1 and the DOC 3 and supplies high-temperature gas into the exhaust gas X flowing from the diesel engine 1 to the DOC 3.

DOC3 is an oxidation catalyst containing platinum, and is arranged downstream of the diesel engine 1 and upstream of the DPF 4 in the flow direction of the exhaust gas X.
The DOC 3 oxidizes the exhaust gas X, and when unburned fuel from the burner 2 remains in the exhaust gas X, the unburned fuel is burned.

The DPF 4 collects fine particles (Particulate Matter) contained in the exhaust gas X and removes them from the exhaust gas X, and is disposed downstream of the DOC 3 in the flow direction of the exhaust gas X.
As the DPF 4, for example, a monolithic filter made of cordierite or silicon nitride is used. In the engine system S1 of this embodiment, the DPF 4 is regenerated by an active regeneration method in which fine particles collected by the high-temperature gas supplied from the burner 2 are burned and regenerated.

The exhaust pipe 5 is a pipe through which the exhaust gas X discharged from the diesel engine 1 flows. When the high-temperature gas is generated by the burner 2, the exhaust pipe 5 is a pipe through which the high-temperature gas flows.
The discharge pipe 5 includes a first pipe 5a that connects the diesel engine 1 and the burner 2, a second pipe 5b that connects the burner 2 and the DOC 3, a third pipe 5c that connects the DOC 3 and the DPF 4, and a DPF 4. And 4th piping 5d which connects an external area | region.

  The fuel pool prevention mechanism 6 is arranged in the middle of the second pipe 5b connecting the burner 2 and the DOC 3 (that is, the discharge pipe through which the high-temperature gas generated by the burner 2 flows), and forms a shear flow in the second pipe 5b. By doing so, the liquid fuel collected in the middle of the 2nd piping 5b is atomized.

  2 is a cross-sectional view taken along line AA in FIG. As shown in FIGS. 2 and 1, in this embodiment, the fuel pool preventing mechanism 6 is a plate-like projecting portion that projects in the middle of the second pipe 5 b. As shown in FIG. 2, the fuel pool preventing mechanism 6 has a lower end curved along the inner wall surface of the second pipe 5b and an upper end linearly set. In this embodiment, the fuel pool prevention mechanism 6 is provided only in the lower region of the second pipe 5b.

  FIG. 3 is a schematic diagram for explaining the function of the fuel pool prevention mechanism 6 in more detail. As shown in this figure, the fuel pool preventing mechanism 6 reduces the flow rate of the exhaust gas X in the lower region by blocking the lower region of the second pipe 5b. As a result, a shear flow Y formed by the exhaust gas Xa having a relatively high flow rate and the exhaust gas Xb having a relatively low flow rate is created on the downstream side of the fuel pool prevention mechanism 6.

The liquid fuel N collected on the upstream side of the fuel pool prevention mechanism 6 reaches the fuel pool prevention mechanism 6 by being pushed away by the flow of the exhaust gas X, and further passes through the fuel pool prevention mechanism 6 to be sheared. It flows to the formation area of the stream Y.
The liquid fuel N that has flowed to the shear flow Y is atomized by being sheared by the shear flow Y. Since the atomized liquid fuel N has a small weight and a low surface tension, it is carried on the flow of the exhaust gas X and is transported to the DOC 3 together with the exhaust gas X.

When the DPF 4 is regenerated in the engine system S1 of this embodiment having such a configuration, as shown in FIG. 1, the state in which the exhaust gas X1 generated in the diesel engine 1 flows through the first pipe 5a is maintained. However, hot gas is generated by the burner 2.
Then, the exhaust gas X2 mixed with the high-temperature gas is supplied to the DOC 3 through the second pipe 5b, and is oxidized. Further, the exhaust gas X3 that has been oxidized and discharged from the DOC 3 is supplied to the DPF 4 via the third pipe 5c, and particulates are collected and removed. Finally, the exhaust gas X discharged from the DPF 4 is exhausted to the external region via the fourth pipe 5d.

Here, the engine system S1 of the present embodiment is arranged in the middle of the second pipe 5b serving as a discharge pipe for the high-temperature gas generated by the burner 2 and forms a shear flow Y in the second pipe 5b. A fuel pool prevention mechanism 6 for atomizing the liquid fuel N collected in the middle of the two pipes 5b is provided.
According to the engine system S1 of this embodiment, the shear flow Y is formed in the second pipe 5b by the fuel pool prevention mechanism 6. As a result, the liquid fuel N accumulated in the second pipe 5b is exposed to the shear flow Y and atomized, and then flows along the flow in the second pipe 5b and flows downstream. A large amount of liquid fuel N can be prevented from accumulating.
Therefore, according to the engine system S1 of the present embodiment, it is possible to prevent the liquid fuel N from being collected in the middle of the second pipe 5b.

  In the second pipe 5b, the liquid fuel N condensed on the upstream side of the fuel pool preventing mechanism 6 eventually reaches the fuel pool preventing mechanism 6 and is atomized. For this reason, it is preferable to arrange | position the fuel pool prevention mechanism 6 as much as possible in the downstream of the 2nd piping 5b (namely, DOC3 nearest).

Further, in the engine system S1 of the present embodiment, the fuel pool prevention mechanism 6 includes a projecting portion that projects in the middle of the second pipe 5b.
For this reason, the fuel pool prevention mechanism 6 can be easily installed only by fixing the protruding portion to the inner wall surface of a generally used cylindrical pipe by spot welding or the like.

Further, in the engine system S1 of the present embodiment, the fuel pool prevention mechanism 6 is provided only in the lower region of the second pipe 5b.
The fuel pool prevention mechanism 6 including the projecting portion becomes an obstacle to the exhaust gas X flowing through the second pipe 5b, and causes a slight increase in pressure loss in the second pipe 5b. For this reason, by installing the fuel pool prevention mechanism 6 only in the lower region of the second pipe 5b where liquid fuel is most likely to accumulate, the liquid fuel N is prevented from accumulating in the middle of the second pipe 5b while suppressing an increase in pressure loss. It becomes possible to do.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the description of the present embodiment, the description of the same parts as those of the first embodiment is omitted or simplified.

  4 and 5 are enlarged views showing the fuel pool prevention mechanism 7 in the present embodiment, FIG. 4 is an enlarged view of the same cut surface as FIG. 1, and FIG. 5 is a sectional view taken along line BB in FIG. It is.

  As shown in FIG. 4, the fuel pool prevention mechanism 7 in the present embodiment has a shape in which the tip 7a protrudes toward the center and the downstream side of the second pipe 5b in the cross-sectional shape, thereby the tip 7a. Suppresses dripping of the fuel pool prevention mechanism 7 toward the downstream side and efficiently atomizes the liquid fuel N.

Further, in the cross-sectional shape of the fuel pool preventing mechanism 7, the inclined surface 7b from the upstream side to the downstream side of the second pipe 5b is connected to the inner wall surface of the second pipe 5b at an obtuse angle, and the inclined surface 7b is It has a shape that gently rises toward the tip 7a.
For this reason, it becomes possible to easily guide the liquid fuel accumulated on the upstream side of the fuel pool prevention mechanism 7 to the tip 7a where the shear flow is formed.

Further, as shown in FIG. 5, the fuel pool prevention mechanism 7 of the present embodiment is formed in an annular shape along the inner wall of the second pipe 5b.
For this reason, the liquid fuel adhering to the whole area in the circumferential direction of the inner wall of the second pipe 5b can be atomized.

Furthermore, the fuel pool prevention mechanism 7 of the present embodiment includes a plurality of grooves 7c that disperse the liquid fuel flowing toward the tip 7a, which is a shear flow forming region, in a direction perpendicular to the flow direction. As shown in FIG. 5, these grooves 7c are arranged at equal intervals over the entire circumference of the fuel pool prevention mechanism 7, and once connected to the tip 7a.
For this reason, the liquid fuel can be dispersed in the circumferential direction of the second pipe 5b before being supplied to the tip 7a (that is, the shear flow forming region). As a result, the surface tension of the liquid fuel can be weakened to facilitate atomization.

In addition, in this embodiment, although the structure where each groove | channel 7c is extended in parallel with the extension direction of the 2nd piping 5b is employ | adopted, the structure extended so that the groove | channel 7c may turn is employ | adopted. May be.
Thereby, the liquid fuel can be dispersed in the circumferential direction of the second pipe 5b.

(Third embodiment)
Next, a third embodiment of the present invention will be described. In the description of the present embodiment, the description of the same parts as those in the first embodiment will be omitted or simplified.

FIG. 6 is an enlarged view of the same cut surface as FIG. 1 in the present embodiment. As shown in this figure, the second pipe 5b of the present embodiment has a straight pipe region 5b1 and a connection region 5b2 swelled in accordance with the shape of the DOC3.
The fuel pool prevention mechanism 8 has a region continuous from the inner wall surface of the straight pipe region 5b1 and is provided so as to protrude in the connection region 5b2 so that the downstream side falls at a right angle.

  By having such a configuration, it is possible to prevent liquid fuel from dripping to the downstream side of the fuel pool prevention mechanism 8 and to suppress an increase in pressure loss in the second pipe 5b.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

For example, in the above-described embodiment, the configuration in which the internal combustion engine in the present invention is a diesel engine mounted on a vehicle has been described.
However, the present invention is not limited to this, and any type and usage form of the internal combustion engine may be used.

Moreover, in the said embodiment, the example which mounted the fuel pool prevention mechanism in the engine system was demonstrated.
However, the present invention is not limited to this, and can be applied to the exhaust gas exhaust piping generated by the burner.

Moreover, in the said embodiment, the atomization means itself demonstrated the structure which is a fuel pool prevention mechanism of this invention.
However, the present invention is not limited to this, and for example, the fuel pool prevention mechanism may be provided with a bank for damming the fuel in addition to the atomizing means.

Moreover, in the said embodiment, the structure which the atomization means consists of a protrusion part was demonstrated.
However, the present invention is not limited to this, and it is also possible to form a recess protruding from the inner wall surface of the second pipe 5b toward the radially outer side of the second pipe 5b as atomization means.

  S1 ... Engine system, 1 ... Diesel engine (internal combustion engine), 2 ... Burner, 3 ... DOC (oxidation catalyst), 4 ... DPF (filter), 5 ... Discharge piping, 6, 7, 8 ... ... Fuel pool prevention mechanism (atomization means, projecting part), 7c ... groove, N ... liquid fuel, X ... exhaust gas, Y ... shear flow

Claims (2)

Having atomization means arranged in the middle of the discharge pipe of the combustion gas generated by the burner,
The atomization means includes
It consists of an annular shape part provided along the circumferential direction of the discharge pipe and protruding from the inner wall,
Have a groove that is arrayed in the circumferential direction of the extending and discharge pipe in the extending direction of the discharge pipe,
One end of the groove is connected to a tip of the annular shape portion, and the fuel pool preventing mechanism is characterized in that: An internal combustion engine, an oxidation catalyst that oxidizes exhaust gas discharged from the internal combustion engine, a filter that collects particulates contained in the exhaust gas that has passed through the oxidation catalyst, and the internal combustion engine and the oxidation catalyst An engine system comprising a burner disposed between,
An engine system comprising the fuel pool prevention mechanism according to claim 1 in the middle of a pipe connecting the burner and the oxidation catalyst.

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