JP2014134157A - Fuel addition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the dilution of engine oil by minimizing post injection to be used.SOLUTION: In a fuel addition device, a fuel addition valve 11 (a first fuel addition valve) is provided on the downstream side of a pre-oxidation catalyst 9 provided in the outlet of a turbine 2b of a turbocharger 2 so that fuel addition can be performed by at least one means out of the fuel addition valve 11 and post injection on the side of a diesel engine 1 (an engine). A fuel addition valve 14 (a second fuel addition valve) is provided on the upstream side of the pre-oxidation catalyst 9 so that fuel addition can be also performed by the fuel addition valve 14.

Description

  The present invention relates to a fuel addition apparatus in which fuel is added to exhaust gas flowing in an exhaust system passage by a fuel addition valve.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot made of carbonaceous matter and SOF content (Soluble Organic Fraction) made of high-boiling hydrocarbon components. 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. It has been done since before.

  This type of particulate filter has a porous honeycomb structure made of ceramics such as cordierite, and the inlets of each flow path partitioned in a lattice pattern are alternately sealed, and the inlets are not sealed. About the flow path, the exit is sealed, and only the exhaust gas which permeate | transmitted the porous thin wall which divides each flow path is discharged | emitted 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. Although it is necessary to regenerate, in an ordinary diesel engine operation state, there are few opportunities to obtain an exhaust temperature high enough for the particulates to self-combust.

  For this reason, for example, an oxidation catalyst formed by adding an appropriate amount of a rare earth element such as cerium to a material in which platinum is supported on alumina is integrally supported on a particulate filter and collected in the particulate filter. The oxidation reaction of the particulates is promoted by the oxidation catalyst to lower the ignition temperature, so that the particulates can be burned and removed even at an exhaust temperature lower than that of the prior art.

  However, even in such a case, in the operation region where the exhaust temperature is low, the trapped amount exceeds the processing amount of the particulates, and therefore the operation state at such a low exhaust temperature continues. There is a risk that the particulate filter will fall into an over-collected state without the particulate filter regenerating well, and the particulate filter is forcibly heated and trapped when the amount of accumulated particulate matter has increased. It is necessary to incinerate the collected particulates.

  More specifically, a flow-through type oxidation catalyst is provided in front of the particulate filter, and fuel is added upstream from the oxidation catalyst, and the added fuel is oxidized by the oxidation catalyst in front of the particulate filter. The exhaust gas heated by the reaction heat is introduced into the particulate filter, the catalyst bed temperature is raised to burn out the particulate, and the particulate filter is regenerated.

  When forcibly regenerating such a particulate filter, the exhaust temperature is too low and the activity of the oxidation catalyst is not sufficiently increased at light loads including when idling is stopped. The pre-oxidation catalyst is heated to an active state by high-temperature exhaust gas that has not yet decreased in temperature at the turbine outlet, and is post-injected on the engine side (the main fuel in the vicinity of compression top dead center). (Addition of injection performed at the timing of non-ignition following injection) is added to perform fuel addition, and the exhaust temperature is raised by oxidizing the added fuel with the pre-oxidation catalyst.

  Then, after the exhaust temperature increase by such a pre-oxidation catalyst is carried out, when the downstream oxidation catalyst is heated to an active state, a fuel addition valve arranged on the downstream side of the pre-oxidation catalyst is used in combination, Fuel addition is also performed from the fuel addition valve to perform forced regeneration of the particulate filter. Also, under operating conditions with high exhaust gas temperature and higher load, the fuel addition valve is switched to fuel addition. The curative filter is forcibly regenerated.

  That is, if the oxidation catalyst in the previous stage of the particulate filter is in an active state and the temperature condition is set so that forced regeneration can be carried out, if the fuel addition for forced regeneration of the particulate filter is to be covered only by post injection, Since there is a possibility that an excessive amount of added fuel may be consumed by the oxidation catalyst, fuel is added by a fuel addition valve arranged on the downstream side of the pre-oxidation catalyst.

  A method for forcibly regenerating this type of particulate filter is also described in the following Patent Document 1 and Patent Document 2 by the same applicant as the present invention.

JP 2003-83139 A JP 2003-155913 A

  However, as described above, post-injection is indispensable for forced regeneration of the particulate filter at light loads. However, if such post-injection is used excessively, one of the fuel injected at the non-ignition timing is used. There is a possibility that the engine part flows down to the oil pan at the bottom of the engine and dilutes the engine oil.

  The present invention has been made in view of the above circumstances, and an object thereof is to reduce the use of post-injection as much as possible and suppress dilution of engine oil.

  The present invention provides a first fuel addition valve on the downstream side of the pre-oxidation catalyst provided at the turbine outlet of the turbocharger, and at least one of the first fuel addition valve and post injection on the engine side The fuel addition device is configured to be able to perform fuel addition by using a second fuel addition valve provided upstream of the pre-oxidation catalyst, and the fuel addition can also be performed by the second fuel addition valve. It is characterized by that.

  Thus, in this way, even when the exhaust temperature is too low and forced regeneration of the particulate filter cannot be performed at light loads including when idling is stopped, the high temperature at which the temperature at the turbine outlet has not yet decreased. Since the pre-oxidation catalyst exposed to the exhaust gas is in an active state, add fuel to the pre-oxidation catalyst here using the second fuel addition valve (subject to post-injection on the engine side as needed). For example, the added fuel undergoes an oxidation reaction with the pre-oxidation catalyst, so that the exhaust gas temperature is raised and the temperature condition for forcibly regenerating the particulate filter is established. As a result, the use of post injection is greatly reduced. Will be.

  Then, after the exhaust gas temperature is raised by such a pre-oxidation catalyst, when the particulate filter can be forcibly regenerated, the first fuel addition valve disposed downstream of the pre-oxidation catalyst is also used. It is only necessary to add fuel and regenerate the particulate filter.

  Further, in the present invention, the second fuel addition valve is arranged so that the fuel can be injected obliquely downstream with respect to the flow direction of the exhaust gas, and the injected fuel from the second fuel addition valve is allowed to collide. It is preferable that a reflector that bounces upstream is provided between the second fuel addition valve and the pre-oxidation catalyst.

  In this way, the injected fuel from the second fuel addition valve collides with the reflector and bounces upstream, and mixes as an opposite flow to the flow of exhaust gas discharged from the turbine outlet of the turbocharger. As a result of striking the flow of the gas from the front, evaporation and dispersion are significantly accelerated, and even at light loads with low exhaust temperatures, it is possible to guide the added fuel to the pre-oxidation catalyst in a well-distributed state as HC gas Thus, a situation in which most of the added fuel is led to the pre-oxidation catalyst in a mist state is avoided.

  That is, the fuel injected in the same direction as the flow of the exhaust gas smoothly rides the flow of the exhaust gas just by injecting the fuel obliquely downstream from the flow direction of the exhaust gas from the second fuel addition valve. Although there is a concern that efficient oxidation treatment cannot be expected due to the pre-oxidation catalyst being led to the pre-oxidation catalyst in a mist state without the evaporation and dispersion of the added fuel proceeding well, there is a risk of collision with the reflector. If you let it bounce back to the upstream side, that concern will be dispelled.

  In addition, when the fuel injected from the second fuel addition valve collides with the reflector and is bounced upstream, it is possible to promote evaporation and dispersion of part of the injected fuel by the impact when the fuel collides with the reflector. It is also possible to promote evaporation of fuel remaining on the reflector surface without being bounced upstream.

  According to the fuel addition apparatus of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, the fuel is added to the upstream side of the pre-oxidation catalyst by the second fuel addition valve at a light load including when idling is stopped, and the added fuel is Since the temperature of the exhaust gas can be raised by an oxidation reaction with an oxidation catalyst, it is only necessary to use post-injection supplementary as necessary when raising the temperature of the exhaust gas. Thus, dilution of engine oil due to post injection can be remarkably suppressed.

  (II) According to the invention described in claim 2 of the present invention, the fuel from the second fuel addition valve collides with the reflector and rebounds upstream, thereby remarkably promoting the evaporation and dispersion of the fuel. Therefore, even when the exhaust temperature is low and the load is light, the added fuel can be guided to the pre-oxidation catalyst in a well-dispersed state as HC gas, and most of the added fuel is guided to the pre-oxidation catalyst in the mist state. Such a situation can be avoided in advance, and fuel addition that is not much different from post-injection can be realized.

It is the schematic which shows an example of the form which implements this invention. It is the schematic which shows another form example of this invention.

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

  FIG. 1 shows an example of an embodiment for carrying out the present invention. In FIG. 1, reference numeral 1 denotes a diesel engine equipped with a turbocharger 2, and intake air 3 led from an air cleaner (not shown) passes through an intake pipe 4. The intake air 3 ′ sent to the compressor 2 a of the turbocharger 2 and pressurized by the compressor 2 a is sent to an intercooler (not shown) to be cooled, and the diesel engine 1 is cooled via an intake manifold (not shown). It is distributed to each cylinder.

  On the other hand, the exhaust gas 5 discharged from each cylinder of the diesel engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 6, and after driving the turbine 2b, the exhaust pipe 8 through the exhaust connector 7. To be sent out.

  Here, a pre-oxidation catalyst 9 is provided at a position connecting the exhaust connector 7 and the exhaust pipe 8, and the exhaust pipe 8 on the downstream side of the pre-oxidation catalyst 9 is directed from the inside to the outside of the exhaust pipe 8. A fuel addition valve 11 (first fuel addition valve) is equipped so as to be able to inject fuel F obliquely downstream with respect to the flow direction of the exhaust gas 5 through the spray pocket 10 which is recessed.

  Further, the exhaust pipe 8 further downstream from the fuel addition valve 11 is provided with a particulate filter 12 that collects particulates in the exhaust gas 5. An oxidation catalyst 13 used for regeneration is provided.

  In this embodiment, in addition to the existing configuration described above, a spray pocket 13 that is recessed from the inside to the outside of the exhaust connector 7 is formed in the exhaust connector 7 on the upstream side of the pre-oxidation catalyst 9. The fuel addition valve 14 (second fuel addition valve) is provided so as to be able to inject the fuel F obliquely downstream with respect to the flow direction of the exhaust gas 5, but the fuel addition valve 14 is provided in the exhaust connector 7. A reflector 15 that collides the injected fuel F from the valve 14 and rebounds to the upstream side is disposed, and as a result, the injected fuel F from the fuel addition valve 14 is injected facing the flow of the exhaust gas 5. It is like that.

  Thus, in this case, the forced regeneration of the particulate filter 12 cannot be performed because the exhaust gas temperature is too low and the activity of the oxidation catalyst 13 does not sufficiently increase at light loads including when idling is stopped. However, since the pre-oxidation catalyst 9 exposed to the high-temperature exhaust gas 5 at the outlet of the turbine 2b that has not yet decreased in temperature is in an active state, fuel is added thereto by the fuel addition valve 14 (if necessary) If the post-injection on the engine side is used as an auxiliary), the added fuel F undergoes an oxidation reaction in the pre-oxidation catalyst 9 to raise the exhaust gas temperature and forcibly regenerate the particulate filter 12. The temperature conditions are in place, and as a result, the use of post injection is greatly reduced.

  At this time, the fuel F injected from the fuel addition valve 14 collides with the reflector, rebounds upstream, and mixes as a counter flow with the flow of the exhaust gas 5 discharged from the turbine 2b outlet of the turbocharger. As a result of striking the flow of 5 from the front, evaporation and dispersion are remarkably promoted. As a result, even when the exhaust temperature is low and the load is light, the added fuel F is led to the pre-oxidation catalyst 9 in a state of being well dispersed as HC gas. This makes it possible to avoid a situation in which most of the added fuel F is led to the pre-oxidation catalyst 9 in a mist state.

  That is, the fuel F injected in the same direction as the flow of the exhaust gas 5 smoothly flows into the flow of the exhaust gas 5 only by injecting the fuel F obliquely downstream from the flow direction of the exhaust gas 5 from the fuel addition valve 14. There is a concern that the process proceeds without miniaturization or diffusion, and the evaporation and dispersion of the added fuel F does not proceed well and is guided to the pre-oxidation catalyst 9 in a mist state, so that efficient oxidation treatment cannot be expected. However, if it is made to collide with a reflector and be bounced back to the upstream side, such a concern will be eliminated.

  As described above, if the injected fuel F from the fuel addition valve 14 collides with the reflector and rebounds to the upstream side, a part of the injected fuel F is evaporated and dispersed by the impact at the time of the collision with the reflector. It is also possible to promote the evaporation of the fuel F remaining on the surface of the reflector without being bounced upstream.

  Then, after the temperature of the exhaust gas is increased by the pre-oxidation catalyst 9, when the downstream oxidation catalyst 13 is heated and becomes active, the fuel addition valve 11 disposed on the downstream side of the pre-oxidation catalyst 9. In addition, the fuel is added, and the exhaust gas 5 is heated by the reaction heat generated by oxidizing the added fuel F with the oxidation catalyst 13 and introduced into the particulate filter 12. The particulate filter 12 may be regenerated by burning off the catalyst.

  As described above, according to the above embodiment, fuel is added to the upstream side of the pre-oxidation catalyst 9 by the fuel addition valve 14 at a light load including when idling is stopped, and the added fuel F is supplied by the pre-oxidation catalyst 9. Since the temperature of the exhaust gas 5 can be raised by an oxidation reaction, it is only necessary to supplementarily use post-injection as necessary when raising the temperature of the exhaust gas, and the use of the post-injection is greatly reduced. Thus, dilution of engine oil due to post-injection can be remarkably suppressed.

  Particularly in this embodiment, the fuel F from the fuel addition valve 14 collides with the reflector and bounces back to the upstream side, so that the evaporation and dispersion of the fuel F can be remarkably promoted. Even during loading, the added fuel F can be led to the pre-oxidation catalyst 9 in a well-distributed state as HC gas, so that most of the added fuel F is led to the pre-oxidation catalyst 9 in a mist state. This makes it possible to avoid such a situation and to realize fuel addition that is not much different from post-injection.

  FIG. 2 shows another embodiment of the present invention. Instead of causing the fuel F from the fuel addition valve 14 to collide with the reflector and bounce it upstream, the fuel addition valve 14 moves upstream of the flow of the exhaust gas 5. In this example, the fuel F is injected toward the reflector, and in this case, the effect of promoting the evaporation and dispersion of a part of the injected fuel F due to the impact when colliding with the reflector is shown. Although not obtained, the embodiment shown in FIG. 1 is capable of remarkably promoting evaporation and dispersion of the injected fuel F by mixing the injected fuel F as a counter flow with the flow of the exhaust gas 5 discharged from the turbine 2b outlet of the turbocharger. Similar to the example.

  In addition, the fuel addition apparatus of this invention is not limited only to the above-mentioned example, Of course, various changes can be added within the range which does not deviate from the summary of this invention.

1 Diesel engine (engine)
2 Turbocharger 2b Turbine 5 Exhaust gas 8 Exhaust pipe 9 Pre-oxidation catalyst 11 Fuel addition valve (first fuel addition valve)
14 Fuel addition valve (second fuel addition valve)
15 Reflector F Fuel

Claims (2)

  A first fuel addition valve is provided downstream of the pre-oxidation catalyst provided at the turbine outlet of the turbocharger, and fuel is added by at least one of the first fuel addition valve and post injection on the engine side. A fuel addition device configured to be able to be performed, wherein a second fuel addition valve is provided on the upstream side of the pre-oxidation catalyst, and the fuel addition can be performed also by the second fuel addition valve. A fuel addition device.   A second fuel addition valve is arranged so that fuel can be injected obliquely downstream with respect to the flow direction of the exhaust gas, and a reflector that collides the injected fuel from the second fuel addition valve and bounces upstream is provided. A fuel addition apparatus provided between the second fuel addition valve and the pre-oxidation catalyst.

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