JP2007071141A - V type diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a V type diesel engine capable of remarkably increasing the capacity of an after treatment device in comparison with the conventional case. <P>SOLUTION: In this V type diesel engine 1 with cylinder rows 2, 3 divided on the right and left, turbochargers 7 are mounted respectively on the left and right cylinder rows 2, 3, exhaust pipes 9 are connected respectively to the turbines 8 of the turbochargers 7 to form an exhaust system into two systems, and the after treatment devices 10 for purifying exhaust gas 5 are individually placed midway the exhaust pipes 9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a V-type diesel engine.

  FIG. 3 shows an example of the configuration of an exhaust system in a conventional V-type diesel engine. In FIG. 3, a pair of cylinder rows 2 and 3 are distributed so as to form a V-shape centering on a crankshaft (not shown). A V-type diesel engine (illustrated in the figure is a case of a V-type 8-cylinder engine including eight cylinders 4), and exhaust gas 5 discharged from each cylinder 4 is supplied to each cylinder row 2 and 3 The exhaust energy is sent to the turbine 8 of the turbocharger 7 through the exhaust manifold 6 and then discharged to the outside through the exhaust pipe 9.

  In the middle of the exhaust pipe 9, when the exhaust air-fuel ratio is lean, NOx in the exhaust gas 5 is oxidized and temporarily stored in the form of nitrate, and when the oxygen concentration in the exhaust gas 5 decreases, NOx occlusion reduction catalyst having the property of decomposing and releasing NOx through the intervention of fuel HC, CO, etc., the selective reduction type catalyst having the property of selectively reacting NOx with a reducing agent even in the presence of oxygen, A post-processing device 10 such as a particulate filter that collects particulate matter (particulate matter) in the exhaust gas 5 is provided.

  Further, as shown in FIG. 4, when the turbocharger 7 is mounted for each of the left and right cylinder rows 2 and 3, the exhaust gas 5 from the turbine 8 of each turbocharger 7 is merged into one. In the middle of the exhaust pipe 9, the post-processing device 10 is provided in the middle of the exhaust pipe 9 as in the case of FIG.

In addition, as the prior art document information related to the V-type diesel engine described above, there is the following.
GP Planning Center, “What is the mechanism of cars? 37-39

  However, in the V-type diesel engine 1 of FIGS. 3 and 4, the exhaust gas 5 from the left and right cylinder rows 2 and 3 is combined into a single exhaust pipe 9 and processed by a single post-processing device 10. For this reason, the size of the post-processing device 10 is restricted in layout, and it is difficult to increase the capacity of the post-processing device 10.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a V-type diesel engine capable of significantly increasing the capacity of the aftertreatment device as compared with the prior art.

  In the V-type diesel engine in which the cylinder rows are divided to the left and right, the present invention has two exhaust systems for each of the left and right cylinder rows, and is equipped with an aftertreatment device for purifying exhaust gas individually for each exhaust system. It is characterized by that.

  In the present invention, a turbocharger may be mounted for each of the left and right cylinder rows, and two exhaust systems may be provided for each turbine of each turbocharger.

  Thus, in this way, the exhaust gas is individually processed by the two post-processing devices for each of the left and right cylinder rows, so that the layout regarding the size at the respective arrangement positions of the respective post-processing devices. Even if the above restriction is applied, the total capacity of the two post-processing devices can be significantly increased compared to the conventional case.

  Further, in the present invention, the aftertreatment device is configured by a triple arrangement of a pre-stage oxidation catalyst, a NOx storage reduction catalyst, and a particulate filter, and fuel addition means for adding fuel to the exhaust gas upstream from the pre-stage oxidation catalyst. It may be provided, and an injector may be provided in the middle of each exhaust system as the fuel addition means.

  In this way, exhaust gas whose exhaust air-fuel ratio is in a lean state is caused to flow through the NOx storage reduction catalyst, so that NOx in the exhaust gas is stored in the form of nitrate to reduce NOx, and this NOx storage reduction is achieved. When the exhaust gas that has passed through the catalyst passes through the particulate filter in the subsequent stage, the particulates in the exhaust gas are collected.

  In addition, when fuel is added to the exhaust gas by the fuel addition means, the added fuel flows into the pre-stage oxidation catalyst to cause an oxidation reaction, and the exhaust gas heated by the reaction heat flows into the NOx occlusion reduction catalyst. While the catalyst bed temperature of the NOx storage reduction catalyst is raised and the catalytic activity is improved, NOx is decomposed and released from the NOx storage reduction catalyst by effectively reducing the excess air ratio of the exhaust gas, and regeneration is achieved. The released NOx reacts with excess added fuel (HC) on the NOx occlusion reduction catalyst and is reduced and purified.

  And, the reaction heat due to regeneration of such NOx occlusion reduction catalyst also contributes to an increase in the catalyst bed temperature of the downstream particulate filter (the temperature of the oxidation catalyst supported on the surface) via the exhaust gas. If further fuel addition is executed after completion of regeneration of the NOx storage reduction catalyst for the particulate filter whose catalyst bed temperature has risen, the particulates collected in the particulate filter can be incinerated satisfactorily. become.

  As the fuel addition means employed in the present invention, an injector is provided in the middle of each exhaust system, or a fuel injection device that injects fuel into each cylinder is employed as the fuel addition means, and compression top dead center. It is possible to add the post-injection at the non-ignition timing following the main injection of the fuel in the vicinity so as to execute the fuel addition.

  According to the above-described V-type diesel engine of the present invention, various excellent effects as described below can be obtained.

  (I) According to the first and second aspects of the present invention, the exhaust gas can be individually processed by the two post-treatment devices for each of the left and right cylinder rows. The capacity can be significantly increased as compared with the prior art.

  (II) According to the third, fourth, and fifth aspects of the present invention, the NOx storage reduction catalyst and the particulate filter having sufficient capacity are provided for each of the left and right cylinder rows, and the NOx and the particulates in the exhaust gas. Can be reduced at the same time, and good regeneration of the NOx occlusion reduction catalyst and the particulate filter can be realized.

  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, and the portions denoted by the same reference numerals as those in FIGS. 3 and 4 represent the same items.

  As shown in FIG. 1, in the present embodiment, a turbocharger 7 is mounted for each of the left and right cylinder rows 2 and 3 with respect to the V-type diesel engine 1 in which the cylinder rows 2 and 3 are assigned to the left and right. Exhaust pipes 9 are respectively connected to the turbine 8 of FIG. 7, and the exhaust system is divided into two systems. In the middle of each exhaust pipe 9, an aftertreatment device 10 for purifying the exhaust gas 5 is individually provided. Has been.

  Thus, if configured in this way, the exhaust gas 5 is individually processed by the two post-processing devices 10 for each of the left and right cylinder rows 2 and 3. Even if there is a layout restriction regarding the size at the arrangement location, the total capacity of the two post-processing devices 10 can be significantly increased as compared with the conventional case.

  Therefore, according to the above embodiment, the exhaust gas 5 can be individually processed by the two post-treatment devices 10 for each of the left and right cylinder rows 2 and 3, so that the total capacity of the two post-treatment devices 10 is conventional. Can be significantly increased.

  Further, FIG. 2 shows a more specific embodiment of the present invention. A post-treatment device 10 is constituted by a triple arrangement of a pre-stage oxidation catalyst 11, a NOx occlusion reduction catalyst 12, and a particulate filter 13, and the pre-stage oxidation is performed. It is assumed that an injector 14 (fuel addition means) for adding fuel directly into the exhaust pipe 9 upstream of the catalyst 11 is provided.

  However, not only the injector 14 is provided as a fuel addition means in this way, but also a fuel injection device (not shown) for injecting fuel into each cylinder 4 is adopted as the fuel addition means, and the fuel near the compression top dead center is adopted. It is also possible to add fuel by adding post-injection at the non-ignition timing following the main injection.

  Thus, regarding the V-type diesel engine 1 configured as described above, when the exhaust gas 5 whose exhaust air-fuel ratio is lean is passed through the NOx storage reduction catalyst 12, NOx in the exhaust gas 5 is stored in the form of nitrate. NOx is reduced, and particulates in the exhaust gas 5 are collected when the exhaust gas 5 having passed through the NOx occlusion reduction catalyst 12 passes through the particulate filter 13 at the subsequent stage.

  Further, when fuel is added to the exhaust gas 5 by the injector 14 (in addition to this, fuel addition by post injection on the engine side may be used together as appropriate), the added fuel flows into the pre-stage oxidation catalyst 11 and is oxidized. The exhaust gas 5 that has caused a reaction and has been heated by the reaction heat flows into the NOx occlusion reduction catalyst 12, whereby the catalyst bed temperature of the NOx occlusion reduction catalyst 12 is raised and the catalytic activity is improved, while the exhaust gas 5 By effectively reducing the excess air ratio of NOx, NOx is decomposed and released from the NOx storage reduction catalyst 12 to be regenerated, and the released NOx reacts with excess added fuel (HC) on the NOx storage reduction catalyst 12. It will be reduced and purified.

  The reaction heat due to the regeneration of the NOx occlusion reduction catalyst 12 also contributes to an increase in the catalyst bed temperature of the downstream particulate filter 13 (the temperature of the oxidation catalyst supported on the surface) via the exhaust gas 5. Therefore, if further fuel addition is performed on the particulate filter 13 whose catalyst bed temperature has increased after completion of regeneration of the NOx storage reduction catalyst 12 as necessary, the particulates collected by the particulate filter 13 are good. Will be incinerated.

  Therefore, according to the present embodiment, the NOx storage reduction catalyst 12 and the particulate filter 13 having sufficient capacity are provided for each of the left and right cylinder rows 2 and 3 to simultaneously reduce NOx and particulates in the exhaust gas 5. It is possible to achieve good regeneration of the NOx occlusion reduction catalyst 12 and the particulate filter 13.

  Note that the V-type diesel engine of the present invention is not limited to the above-described embodiments, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

It is a top view which shows an example of the form which implements this invention. It is a top view which shows the more specific form example of this invention. It is a top view which shows a prior art example. It is a top view which shows another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 V type diesel engine 2 Cylinder row | line | column 3 Cylinder row | line | column 4 Cylinder 5 Exhaust gas 6 Exhaust manifold 7 Turbocharger 8 Turbine 9 Exhaust pipe 10 Aftertreatment apparatus 11 Pre-stage oxidation catalyst 12 NOx occlusion reduction catalyst 13 Particulate filter 14 Injector (fuel addition means) )

Claims (5)

  In the V-type diesel engine with the cylinder rows distributed to the left and right, the exhaust system is divided into two systems for each of the left and right cylinder rows, and an after-treatment device for purifying exhaust gas is individually provided for each exhaust system. V-type diesel engine.   2. The V-type diesel engine according to claim 1, wherein a turbocharger is mounted for each of the left and right cylinder rows, and two exhaust systems are provided for each turbine of each turbocharger.   The aftertreatment device is constituted by a triple arrangement of a pre-stage oxidation catalyst, a NOx occlusion reduction catalyst, and a particulate filter, and is provided with a fuel addition means for adding fuel to exhaust gas upstream from the pre-stage oxidation catalyst. The V-type diesel engine according to claim 1 or 2.   The V-type diesel engine according to claim 1, 2, or 3, wherein an injector is provided in the middle of each exhaust system as fuel addition means.   The fuel injection device that injects fuel into each cylinder also serves as a fuel addition means, and after the main injection of fuel near the compression top dead center, post injection is added at non-ignition timing to perform fuel addition The V-type diesel engine according to claim 1, 2, 3, or 4, wherein the V-type diesel engine is configured.

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