JP2009091910A - Exhaust diffuser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly safe exhaust diffuser for more reliably preventing thermal damage to persons/objects than conventional one. <P>SOLUTION: The exhaust diffuser 8 reduces the temperature of exhaust gas 1 to be exhausted from a vehicle to the outside to improve safety around an exhaust outlet. At the terminal of an exhaust pipe 2, an exhaust cone 9 is provided whose diameter is gradually larger as tending toward the exhausting direction of the exhaust gas 1. At the outlet center of the exhaust cone 9, a domed plate 11 is arranged which is swollen to be spherical in the direction of facing the flow of the exhaust gas 1 and which has a number of vent holes 10 opened. The domed plate 11 is supported on the outlet outer periphery of the exhaust cone 9 at a plurality of peripheral positions by a supporting material 12 to secure an annular exhaust flow path 13 around the domed plate 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust diffuser for increasing the safety around an exhaust outlet by lowering the temperature of exhaust gas discharged from a vehicle to the outside of the vehicle.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of a soot fraction composed of carbon and a SOF fraction (Soluble Organic Fraction) composed of a high-boiling hydrocarbon component. Furthermore, the composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. Has been performed conventionally.

  The particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of the respective channels partitioned in a lattice shape are alternately sealed, and the channels are not sealed. The outlet is sealed, and only the exhaust gas that has permeated through the porous thin wall that defines each flow path is discharged downstream.

  Then, the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, so that the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. It is necessary to regenerate, but in normal diesel engine operation conditions, there are few opportunities to obtain exhaust temperatures that are high enough for particulates to self-combust, so a catalyst regeneration type that integrally supports an oxidation catalyst. A particulate filter is used.

  That is, if such a catalyst regeneration type particulate filter is employed, the oxidation reaction of the collected particulates is promoted to lower the ignition temperature, and the particulates can be burned and removed even at an exhaust temperature lower than the conventional one. It becomes possible.

  However, even when such a catalyst regeneration type particulate filter is used, the trapped amount exceeds the particulate processing amount in the operation region where the exhaust temperature is low, so such a low exhaust gas. If the operation state at the temperature continues, there is a possibility that the particulate filter will fall into an over trapped state without the regeneration of the particulate filter proceeding well.

  Therefore, a flow-through type oxidation catalyst is separately arranged in front of the particulate filter, and fuel is added to the exhaust gas upstream of the oxidation catalyst at the stage where the amount of particulate accumulation has increased. It is considered to perform forced regeneration.

  That is, the fuel (HC) added on the upstream side of the particulate filter undergoes an oxidation reaction while passing through the preceding oxidation catalyst, and the catalyst bed of the particulate filter immediately after the inflow of exhaust gas heated by the reaction heat. The temperature is raised, the particulates are burned out, and the particulate filter is regenerated.

  As a specific means for executing this kind of fuel addition, post-injection is added at the timing of non-ignition later than the compression top dead center following the main injection of fuel performed near the compression top dead center. What is necessary is just to add a fuel in gas.

  However, in a garbage collection vehicle that stops at each collection place while traveling in a residential area and collects household garbage, or a transport truck that collects and delivers parcels for delivery, it will travel in a place with many people. It is necessary to take measures to prevent a situation in which the hot exhaust gas generated during forced regeneration of the particulate filter causes heat damage to pedestrians and the like.

  FIG. 3 shows an example of a conventional countermeasure against heat damage. In the example shown here, the end portion of the exhaust pipe 2 for discharging the exhaust gas 1 to the outside of the vehicle has a cylindrical shape larger in diameter than the exhaust pipe 2. The exhaust diffuser 5 is configured by concentrically supporting the cover 3 from a plurality of locations in the circumferential direction via support members 4.

  In this way, due to the difference in dynamic pressure between the exhaust pipe 2 side and the cover 3 side, the atmosphere 7 is sucked from the gap 6 between the end portion of the exhaust pipe 2 and the cover 3 and mixed with the exhaust gas 1. As a result, the high temperature exhaust gas 1 becomes a mixed gas with the normal temperature atmosphere 7 and the temperature is lowered, so that a pedestrian or the like passing near the vehicle is not exposed to the high temperature exhaust gas 1.

As prior art document information related to this type of exhaust diffuser, there are the following Patent Document 1, Patent Document 2, and the like.
Japanese Patent Laid-Open No. 3-1224917 JP-A-63-295814

  However, in such a conventional structure, the gap 6 between the terminal end of the exhaust pipe 2 and the cover 3 is opened upstream from the final outlet of the exhaust diffuser 5, so that the exhaust gas 1 is discharged from the gap 6. There is a possibility of leakage due to reverse flow, and in the unlikely event that the high-temperature exhaust gas 1 leaks from there, there is a risk of unexpected heat damage to surrounding structures.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a highly safe exhaust diffuser that can prevent heat damage to people and objectives more reliably than in the past.

  The present invention is provided with an exhaust cone that gradually increases in diameter toward the exhaust gas exhaust direction at the end of the exhaust pipe, and swells in a spherical shape in the direction opposite to the flow of the exhaust gas at the center of the outlet of the exhaust cone. A dome-shaped plate having a vent hole is disposed, and the dome-shaped plate is supported by a support material from a plurality of locations in the circumferential direction of the outlet outer peripheral portion of the exhaust cone, thereby securing an annular exhaust passage around the dome-shaped plate. It is characterized by this.

  Thus, in this way, the main flow of the exhaust gas flowing out from the end portion of the exhaust pipe hits the dome-shaped plate at the center of the outlet of the exhaust cone and spreads to the outer peripheral side while passing a part through the vent hole. As a result of being dissipated from the exhaust cone while greatly expanding through the surrounding annular exhaust flow path, the cross-sectional area of the exhaust gas flow increases, the thermal energy density decreases, the exhaust gas temperature decreases, and the interpersonal -Thermal damage to the objective will be prevented.

  In addition, the flow of exhaust gas that strikes the dome-shaped plate at the center of the outlet of the exhaust cone and expands in a skirt shape from the annular exhaust flow path, and vigorously discharges the turbulent flow at the interface between the atmosphere and the exhaust gas. Thus, even if the exhaust gas and the atmosphere are mixed well, an effective temperature reduction of the exhaust gas can be achieved.

  Note that a dome-shaped plate is used as a guide means for guiding the main flow of exhaust gas to the outer peripheral side of the exhaust cone. However, such a dome-shaped plate can be easily obtained by only pressing the punching plate once. In addition, it is possible to provide guide means with low exhaust resistance by expanding in a spherical shape in a direction opposite to the flow of exhaust gas and opening a large number of vent holes.

  According to the exhaust diffuser of the present invention described above, various excellent effects as described below can be obtained.

  (I) The action of increasing the cross-sectional area of the exhaust gas flow to decrease the thermal energy density and promoting turbulent flow at the interface between the atmosphere and the exhaust gas to achieve good mixing of the exhaust gas and the atmosphere Due to the synergistic effect with the action, the temperature of the exhaust gas diffused from the outlet of the exhaust diffuser can be effectively reduced, and there is no need to form a gap for taking in the air upstream from the outlet of the exhaust diffuser. Since it is possible to eliminate the concern that exhaust gas leaks from the gap, it is possible to prevent heat damage to humans and objectives more reliably than before, and around the exhaust outlet during forced regeneration of the particulate filter, etc. Safety can be greatly improved.

  (II) Since the dome-shaped plate can be easily manufactured only by pressing the punching plate once, the manufacturing cost of the dome-shaped plate can be kept low, and the flow of exhaust gas. Due to the spherical shape that swells in the opposite direction and the numerous vent holes opened here, the exhaust resistance due to the main flow of exhaust gas hitting the dome-shaped plate can be minimized and the pressure loss increases Can be remarkably suppressed.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 and 2 show an example of an embodiment for carrying out the present invention, and portions denoted by the same reference numerals as those in FIG. 3 represent the same items.

  As shown in FIGS. 1 and 2, in the exhaust diffuser 8 of this embodiment, the exhaust gas 1 gradually flows toward the end of the exhaust pipe 2 through which the exhaust gas 1 flows (to the right in FIG. 1). A dome-shaped plate 11 swells in a spherical shape in the direction opposite to the flow of the exhaust gas 1 and has a large number of air holes 10 opened at the center of the outlet of the exhaust cone 9. The dome-shaped plate 11 is supported by a support member 12 from a plurality of locations in the circumferential direction of the outlet outer peripheral portion of the exhaust cone 9 so as to secure an annular exhaust flow path 13 around the dome-shaped plate 11. Yes.

  Here, the exhaust cone 9 is provided with a sleeve portion 14 that can be fitted to the end portion of the exhaust pipe 2 at the base end portion thereof, and a fastening bolt that is screwed to a plurality of locations in the circumferential direction of the sleeve portion 14. By tightening 15, the exhaust pipe 2 is fixed to the end portion.

  Thus, when the exhaust diffuser 8 is configured in this way, the main flow of the exhaust gas 1 flowing out from the end portion of the exhaust pipe 2 hits the dome-shaped plate 11 at the center of the outlet of the exhaust cone 9, and a part of the vent hole 10 is formed. The heat energy density is increased by increasing the cross-sectional area of the flow of the exhaust gas 1 as a result of being diffused from the exhaust cone 9 while passing through the surrounding annular exhaust passage 13 and being greatly expanded while being passed. As a result, the temperature of the exhaust gas 1 is lowered and the heat damage of the person and the object is prevented.

  In particular, as shown by a schematic arrow on the right side of FIG. 1, exhaust gas that strikes the dome-shaped plate 11 at the center of the outlet of the exhaust cone 9 and is expelled from the annular exhaust passage 13 while expanding in a skirt shape. 1 flow promotes turbulent flow at the interface between the atmosphere 7 and the exhaust gas 1, and the exhaust gas 1 and the atmosphere 7 can be mixed well, thereby effectively reducing the temperature of the exhaust gas 1. Figured.

  Note that a dome-shaped plate 11 is employed as a guide means for guiding the main flow of the exhaust gas 1 to the outer peripheral side of the exhaust cone 9, but such a dome-shaped plate 11 is subjected to a single press working on the punching plate. In addition, it can be easily manufactured, and is swelled in a spherical shape in a direction opposite to the flow of the exhaust gas 1 and has a large number of vent holes 10 to provide a guide means with low exhaust resistance. It is possible.

  Therefore, according to the above embodiment, the action of increasing the cross-sectional area of the flow of the exhaust gas 1 to decrease the thermal energy density and the turbulent flow at the boundary surface between the atmosphere 7 and the exhaust gas 1 are promoted and the exhaust gas is promoted. The temperature of the exhaust gas 1 radiated from the outlet of the exhaust diffuser 8 can be effectively reduced by the synergistic effect of the action of achieving good mixing of the air 1 and the atmosphere 7, and moreover from the outlet of the exhaust diffuser 8. Since it is not necessary to form a gap for taking in the atmosphere 7 upstream, it is possible to eliminate the concern that the exhaust gas 1 leaks from the gap, so that it is possible to prevent thermal damage to people and objectives more reliably than before. Therefore, the safety around the exhaust outlet at the time of forced regeneration of the particulate filter can be greatly improved.

  In addition, since the dome-shaped plate 11 can be easily manufactured by simply pressing the punching plate once, the manufacturing cost of the dome-shaped plate 11 can be suppressed at a low cost, and the exhaust gas 1 Due to the spherical shape that swells in a direction opposite to the flow of the gas and the numerous vent holes 10 opened here, the exhaust resistance due to the main flow of the exhaust gas 1 hitting the dome-shaped plate 11 can be suppressed as small as possible. Thus, an increase in pressure loss can be remarkably suppressed.

  The exhaust diffuser of the present invention is not limited to the above-described embodiment, and can be similarly applied to a vehicle that is not equipped with a system that performs forced regeneration of the particulate filter. Of course, various modifications can be made without departing from the scope of the invention.

It is a side view which shows an example of the form which implements this invention. It is an arrow view of the II-II direction of FIG. It is a side view which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas 2 Exhaust pipe 8 Exhaust diffuser 9 Exhaust cone 10 Ventilation hole 11 Dome type plate 12 Support material 13 Annular exhaust flow path

Claims (1)

  An exhaust cone that gradually expands in the exhaust gas exhaust direction is provided at the end of the exhaust pipe. The exhaust cone swells in a spherical shape in the direction opposite the exhaust gas flow at the center of the outlet of the exhaust cone and opens a number of vent holes. The dome-shaped plate is disposed, and the dome-shaped plate is supported by a support material from a plurality of locations in the circumferential direction of the outlet outer peripheral portion of the exhaust cone, thereby securing an annular exhaust passage around the dome-shaped plate. Exhaust diffuser to do.

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