JP3714732B2 - Diesel engine exhaust purification system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diesel engine exhaust gas purification device that purifies exhaust gas with a catalyst in a diesel engine.
[0002]
[Prior art]
Exhaust gas emitted from diesel engines contains SOF (Soluble Organic Fraction) such as unburned fuel and unburned oil, and particulates such as carbon. After oxidizing SOF with a catalyst, it enters the atmosphere. It is generally known that when discharged, the total amount of particulate emissions can be reduced.
[0003]
As a low-temperature active oxidation catalyst that is effective even at a relatively low temperature, there is a platinum-based catalyst, which is supported on a carrier disposed in an exhaust gas flow path, and oxidizes SOF in the particulate.
The platinum-based catalyst is effective in reducing SOF such as unburned fuel and unburned oil in HC and particulates when the engine is under a low load.
[0004]
By the way, although the amount of air increases at the time of low load and the generation of “soot” decreases, the generation amount of SOF tends to increase as the exhaust temperature decreases.
Further, when the temperature is higher high load, until sulfur contained in the fuel of a diesel engine will also be oxidized, increased SOx such as SO _2, for example increased SO ₃ and water and the sulfate by reacting ( There is also a problem that the total amount of particulates increases as a result of the generation of sulfuric acid compounds).
[0005]
A technique for controlling the temperature of the exhaust gas entering the catalyst is provided, an example of which is shown in FIGS. 12 and 13.
That is, FIG. 12 is a schematic diagram showing the main part, in which a catalyst 1 composed of a low-temperature active oxidation catalyst, for example, a catalyst carrier carrying a platinum-based catalyst, is connected to an exhaust gas passage 2 of a diesel engine and a treated exhaust gas. It is provided between the exhaust gas passage 3 for discharging gas to the atmosphere.
[0006]
A bypass flow path 4 is branched from the exhaust gas flow path 2, and a flow path switching valve 5 is provided at the inlet 4a of the bypass flow path 4 so that the flow path to the catalyst 1 and the bypass flow path are provided. The exhaust gas is selectively circulated through any one of the four.
The bypass flow path 4 is composed of flow paths 4b and 4c. The flow paths 4b and 4c surround the catalyst 1 and merge with the exhaust gas flow path 3 at the outlet 4d.
[0007]
The position of the flow path switching valve 5 is adjusted by an actuator 6 controlled by the controller 7, and is set to a required position based on the determination of the high load state and the low load state of the engine. It is configured.
With this configuration, the operating condition of the region A in the graph of FIG. 13, small generation amount of sulfate, and because it is a high temperature region purification efficiency, by switching the flow path switching valve 5 to the solid line position in FIG. 12 The exhaust gas is circulated toward the catalyst 1.
[0008]
Further, since the catalyst 1 is warmed by the exhaust gas flowing through the bypass flow path 4 in a high load state, the SOF in the particulate is efficiently oxidized.
Then, further in the operating conditions such as idling state of low load (the region of Figure 13 C), by switching the flow path switching valve 5 to the dotted line position of FIG. 12, it is passed through the exhaust gas to the bypass passage 4, catalyst 1 Prevents the temperature from falling below the proper temperature.
[0009]
Further, in the high load region B where the exhaust gas is at a high temperature, the exhaust gas is circulated to the bypass flow path 4 by switching the flow path switching valve 5 so as to suppress the generation of sulfate so that the exhaust gas does not flow into the catalyst 1. To.
[0010]
[Problems to be solved by the invention]
Thus, in the conventional configuration shown in FIGS. 12 and 13 , the exhaust gas in the low temperature region is devised to flow into the catalyst 1, but the exhaust gas in the high temperature region suppresses sulfate generation. Bypass the catalyst.
Therefore, the exhaust gas is purified only in the temperature range where the generation of sulfate is low and the purification rate is high, and in the high exhaust temperature and low exhaust temperature regions, the exhaust gas is discharged to the atmosphere as it is because no catalyst is used. There are challenges.
[0011]
For example, JP-A-5-263628, JP-A-6-264732, JP-A-6-8259, JP-A-5-1616, etc. disclose related techniques. The technology was not intended to solve the above problems.
The present invention was devised in view of the above-mentioned problems, and in order to effectively utilize the catalyst in a wider operating range, the exhaust gas temperature is controlled, and the diesel engine can be used efficiently in the entire region. An object of the present invention is to provide an exhaust emission control device for an engine.
[0012]
[Means for Solving the Problems]
Therefore, an exhaust emission control device for a diesel engine according to claim 1 of the present invention includes a catalyst disposed in an exhaust passage of the diesel engine for purifying harmful components in the exhaust, and an exhaust passage upstream of the catalyst. An exhaust turbine provided and driven by exhaust pressure; a compressor coupled to the exhaust turbine and driven to rotate by the exhaust turbine; an upstream side of the exhaust passage in the exhaust passage and a downstream side of the exhaust turbine in the exhaust passage A bypass passage that bypasses the exhaust turbine, a bypass valve that bypasses the exhaust turbine and controls the flow rate of the exhaust gas that flows through the bypass passage, and upstream of the catalyst by compressed air obtained from the compressor The exhaust passage or the cooling means for cooling the catalyst, and the exhaust temperature or the catalyst temperature flowing into the catalyst is the optimum active range temperature of the catalyst. Control means for controlling the opening degree of the bypass valve as described above, and the control means is configured to control the open / close state of the bypass valve in accordance with the exhaust gas temperature upstream of the catalyst and the engine operating state. is Rutotomoni, the cooling means is configured to cool the catalyst by supplying the compressed air to the catalyst without being mixed with the exhaust gas flowing through the compressed air and exhaust passage obtained by said compressor It is characterized by that.
[0016]
According to a second aspect of the present invention, there is provided an exhaust purification apparatus for a diesel engine according to the present invention, wherein , in addition to the configuration of the first aspect, the cooling means includes an inner pipe formed in an exhaust passage upstream of the catalyst, The heat exchanger is configured as a heat exchanger having a double pipe structure composed of an outer pipe, compressed air from the compressor is supplied to the outer pipe of the double pipe structure, and the exhaust gas is supplied to the inner pipe of the double pipe structure. It is characterized by being configured to be distributed .
[0017]
Moreover, in addition to the structure of the said Claim 1 or 2, the exhaust-gas purification apparatus of the diesel engine of this invention of Claim 3 has a several catalyst layer, This catalyst is a catalyst layer and this catalyst layer. It is characterized by being formed by alternately polymerizing air flow path portions through which compressed air from the compressor flows .
According to a fourth aspect of the present invention, there is provided a diesel engine exhaust gas purification apparatus, wherein the catalyst is configured as an oxidation catalyst in addition to the structure according to any one of the first to third aspects, and the purification by the oxidation catalyst. in operation, the control means, so that the exhaust gas temperature flowing into the catalyst is a temperature range which does not generate sulfate at the oxidation catalyst, as characterized in the flow rate of the compressed air is configured to be controlled Yes.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 9 show a diesel engine exhaust gas purification apparatus as a first embodiment of the present invention. FIG. FIG. 2 is a schematic view showing the flow path switching valve, FIG. 3 is a schematic cross-sectional view showing the main configuration of the air-cooled heat exchanger, and FIGS. 4 to 6 are other examples of the air-cooled heat exchanger. FIG. 7 to FIG. 9 are diagrams showing the operation characteristics, and FIG. 10 and FIG. 11 show a diesel engine exhaust gas purification apparatus as a second embodiment of the present invention . FIG. 10 is a schematic view showing the configuration of the main part, and FIG. 11 is a schematic perspective view showing the catalyst structure.
(A) Description of the First Embodiment First, the first embodiment will be described. As shown in FIG. 1, the exhaust system 100 of the diesel engine E is provided with a catalyst 1 for purifying harmful components in the exhaust. It is installed.
[0019]
Further, the exhaust system 100 upstream of the catalyst 1 is provided with an exhaust turbine 8T of the first supercharger 8 and an exhaust turbine 9T of the second supercharger 9, and each exhaust turbine 8T, 9T is configured to be rotationally driven by exhaust.
A compressor 8C and a compressor 9C are connected to the exhaust turbine 8T and the exhaust turbine 9T, respectively, and the compressors 8C and 9C are rotationally driven on the same axis as the exhaust turbines 8T and 9T connected thereto. It is like that.
[0020]
Here, the first supercharger 8 is a general turbocharger provided to improve the output of the engine E. When the compressor 8C is driven, the intake air introduced through the air cleaner 15 is sucked. Pressure is supplied to the engine E.
Further, the exhaust turbine 8T of the first supercharger 8 is interposed between the exhaust passage 2 and the exhaust passage 16 of the exhaust system 100 of the engine E, and the exhaust gas after driving the exhaust turbine 8T is The gas is discharged to the exhaust passage 16.
[0021]
Further, the downstream side of the exhaust passage 16 branches into an exhaust passage 11 and a bypass passage 13, and a flow path switching valve (bypass valve) 10 is provided at a branch portion between the exhaust passage 11 and the bypass passage 13. It is intervened. The exhaust passage 11 is connected to the exhaust turbine 9T of the second supercharger 9, and the exhaust turbine 9T is driven by circulating the exhaust gas through the exhaust passage 11.
[0022]
Further, the exhaust passage 11 and the bypass passage 13 join together at the downstream side of the exhaust turbine 9T in the exhaust passage 11 to form an exhaust passage 27.
The compressor 9C of the second supercharger 9 takes air from the air supply passage 12 that is open to the atmosphere and pressurizes (compresses) the air, and supplies the compressed air to the cooling air passage (cooling passage) 17 on the downstream side. It comes to supply. The pressurized air (or compressed air) supplied in this way is configured to be supplied to a cooler (heat exchanger) 14 as a cooling means via a cooling air passage 17. Yes.
[0023]
Here, the cooler 14 has a structure as shown in FIG. 3, for example. That is, in the structure shown in FIG. 3, the cooler 14 is configured to have a double tube structure including an inner tube 20 and an outer tube 21, and the outer tube 21 is supplied with compressed air from the compressor 9C. ing. The inner pipe 20 is connected to an exhaust passage 27, and exhaust gas is supplied to the inner pipe 20. And by providing the cooler 14 in this way, it is configured as a heat exchange structure in which the exhaust gas flowing through the inner tube 20 is cooled by the compressed air in the outer tube 21.
[0024]
Incidentally, a control means S is provided to control the flow rate of the compressed air so that the temperature of the exhaust gas flowing into the catalyst 1 becomes the optimum active range temperature of the catalyst 1.
That is, the control means S is composed of the flow path switching valve 10 and the controller 7, and the flow path switching valve 10 adjusts the outflow opening degree from the exhaust passage 16 to the exhaust passage 11 from fully closed to fully open. The exhaust flow rate from the exhaust passage 16 to the exhaust passage 11 is adjusted. At this time, of the exhaust flow flowing in from the exhaust passage 16, the remainder that does not flow out to the exhaust passage 11 flows out from the exhaust passage 16 to the bypass passage 13.
[0025]
On the other hand, information from a sensor (not shown) that can detect the exhaust temperature and the engine speed is input to the controller 7, and the controller 7 constituted by a computer or the like receives input signals from each sensor. The control signal based on the above is output, and the opening / closing control of the flow path switching valve 10 is performed according to the exhaust gas temperature upstream of the catalyst 1 and the engine operating state.
[0026]
Here, the flow path switching valve 10 is configured as shown in FIG. 2, and the valve body 10A is driven by an actuator (not shown) to adjust the opening degree with respect to the bypass passage 13 and the opening degree with respect to the exhaust passage 11. The shunting is performed in a desired state.
Thus, the control means S controls the flow path switching valve 10 with the control signal from the controller 7 to perform the desired cooling in the cooler 14 so that the temperature of the catalyst 1 is high and the purification efficiency is high. In addition, the exhaust gas temperature is controlled. Further, when the catalyst 1 is an oxidation catalyst, the control is performed so that the catalyst inlet temperature is in a range in which sulfate is not generated.
[0027]
Since the diesel engine exhaust gas purification apparatus according to the first embodiment of the present invention is configured as described above, the following operation is performed.
First, when the engine E is operated, the compressor 8C is driven by the exhaust from the exhaust passage 2 via the exhaust turbine 8T, and the intake air flowing from the air cleaner 15 is pressurized by the compressor 8C to perform a supercharging operation. .
[0028]
On the other hand, the exhaust gas discharged from the engine E drives the exhaust turbine 8T of the first supercharger 8 and then flows into the catalyst 1 through the exhaust passage 16 and the bypass passage 13.
Here, a part of the exhaust gas in the exhaust passage 16 circulates in the exhaust passage 11 via the flow path switching valve 10, drives the exhaust turbine 9 T of the second supercharger 9, and then joins the bypass passage 13. To do. And by driving the exhaust turbine 9T with exhaust energy in this way, the exhaust gas works and the exhaust temperature decreases.
[0029]
Further, the flow rate of the exhaust passage 11 is controlled by the control means S. That is, the opening degree of the flow path switching valve 10 is adjusted by the control signal from the controller 7, the flow rate of the exhaust passage 11 is adjusted, and the driving state of the exhaust turbine 9T is controlled.
The compressor 9 </ b> C is driven by driving the exhaust turbine 9 </ b> T, whereby the atmosphere flowing in from the air supply passage 12 is compressed and flows into the cooler 14 through the cooling air passage 17.
[0030]
In the cooler 14, the exhaust gas in the inner pipe 20 is cooled by the cooling air in the outer pipe 21, and heat exchange is performed. The exhaust gas temperature is controlled by adjusting the amount of cooling air supplied. That is, the temperature of the exhaust gas is controlled so that the temperature of the catalyst 1 is high and the purification efficiency is high. Further, when the catalyst 1 is an oxidation catalyst, the exhaust gas temperature is controlled so that the catalyst inlet temperature is in a range where no sulfate is generated.
[0031]
The operation characteristics obtained by such an operation will be described with reference to FIGS. 7 to 9. First, as shown in FIG. 7, when the inlet temperature of the exhaust turbine 9T is low (light load), the flow path switching valve 10 Operation is controlled in the closed state (see FIG. 2).
When the inlet temperature of the exhaust turbine 9T rises and the inlet temperature of the catalyst 1 reaches the first predetermined temperature, the flow path switching valve 10 starts to open based on a control signal from the controller 7. As a result, part of the exhaust gas flows through the exhaust passage 11 to drive the exhaust turbine 9T, and the compressor 9C is operated to supply air to the cooler 14.
[0032]
Thereby, the exhaust gas temperature in the inner pipe 20 in the bypass passage 13 is lowered, and the inlet temperature of the catalyst 1 is lowered.
By controlling the flow path switching valve 10 in this way, efficient purification is performed in the catalyst 1.
By the way, regarding the oxidation catalyst, the relationship between the catalyst inlet temperature, the sulfate generation amount, and the catalyst efficiency as described above has characteristics as shown in FIG. For this reason, the operation of the flow path switching valve 10 is controlled based on information from an exhaust gas temperature sensor (not shown) so that the catalyst inlet temperature falls within the appropriate central range (for example, 250 to 450 ° C.).
[0033]
For NOx catalysts, the relationship between the catalyst inlet temperature and the catalyst efficiency has the characteristics shown in FIG. 9. In this case, the catalyst inlet temperature is determined based on information from an exhaust temperature sensor (not shown). The operation of the flow path switching valve 10 is controlled so as to be in the center appropriate range (300 to 500 °).
Furthermore, when the exhaust gas temperature in the exhaust passage 27 is too low, the flow path switching valve 10 is closed and the operation of the compressor 9C is prohibited, so that the cooler 14 having a double-pipe structure functions as a heat retaining device, The exhaust gas temperature can be maintained within a desired temperature range.
[0034]
Thus, according to this apparatus, since the exhaust gas temperature can be controlled to the maximum efficiency temperature of the catalyst, the exhaust gas reduction effect, the amount of sulfate produced, and the like can be greatly improved. Furthermore, since the catalyst 1 does not become too high in temperature, thermal deterioration of the catalyst 1 can be prevented.
Further, since the compressed air produced by the compressor 9c is not returned to the engine intake air, the residual oxygen in the exhaust gas does not increase. For example, in the case of a NOx catalyst, there is an advantage that the catalyst efficiency does not decrease.
[0035]
By the way, as a structure of the cooler 14, it is not limited to what is shown in FIG. 3, For example, you may comprise by the structure as shown in FIGS. Even with such a configuration, the same operation as described above can be realized.
Here, what is shown in FIG. 4 is one in which an inner tube 20 composed of a plurality of small tubes is provided in one outer tube 21. And according to such a structure, since the surface area of the inner pipe | tube 20 increases, there exists an advantage that the temperature of the exhaust gas which passes the inner pipe | tube 20 can be reduced efficiently.
[0036]
5 is provided with a nozzle 17A at the tip of the cooling air passage 17, and by blowing compressed air (cooling air) from the nozzle 17A to the exhaust passage 27, the exhaust gas in the exhaust passage 27 is reduced. It is configured to cool. According to such a structure, there exists an advantage that the cooler 14 can be comprised easily.
[0037]
6 is provided with a turbine 22 driven by a nozzle 17 </ b> A, and cooling air is supplied to an exhaust passage 27 by a propeller 23 of the turbine 22. According to such a structure, even when the air supplied from the nozzle 17A is small, more air can be supplied to the exhaust passage 27, and the cooling efficiency of the cooler 14 can be improved. The advantage there Ru.
[0045]
(B) Description of second embodiment Next, a second embodiment of the present invention will be described. As shown in Fig. 10 , a supercharger 9 is disposed downstream of the exhaust passage 2 of the engine E. An exhaust turbine 9T is provided, and the catalyst 1 is connected to the downstream side of the exhaust turbine 9T through an exhaust passage 16.
[0046]
A bypass passage 13 for bypassing exhaust gas from the exhaust turbine 9T is provided between the exhaust passage 2 and the exhaust passage 16, and a flow path switching valve (bypass valve) 10 is provided in the bypass passage 13. Is intervening.
The flow path switching valve 10 is controlled on the basis of a control signal from the controller 7, whereby the amount of exhaust gas flowing through the bypass path 13 can be adjusted.
[0047]
Further, a compressor 9C is connected to the exhaust turbine 9T, and the compressor 9C is driven to rotate as the exhaust turbine 9T rotates.
When the controller 9 </ b> C is driven, the air taken in through the air cleaner 15 is pressurized, and this air is supplied to the cooler 14 through the cooling air passage 17.
[0048]
Incidentally, the flow rate of the air supplied to the cooler 14 is controlled by the control means S so that the temperature of the exhaust gas flowing into the catalyst 1 becomes the optimum active range temperature of the catalyst 1.
Here, the control means S is composed of the flow path switching valve 10 and the controller 7, and controls the driving state of the exhaust turbine 9T by adjusting the opening degree of the flow path switching valve 10, and the compressor 9C. The operation is controlled to adjust the flow rate of the air supplied to the cooler 14.
[0049]
Then, the control unit S, and performs the first embodiment forms on purpose similar control. That is, various information such as the exhaust temperature and the engine speed is input to the controller 7, and the controller 7 outputs a control signal based on the input signal from each sensor and The opening / closing control of the flow path switching valve 10 is performed in accordance with the exhaust gas temperature at the inlet and the engine operating state.
[0050]
On the other hand, as shown in FIG. 11 , in the present embodiment, the catalyst 1 is configured to have a function as a cooler 14.
That is, as shown in FIG. 11 , in the catalyst 1, the catalyst layers 1 </ b> A to 1 </ b> C for purifying exhaust gas and the cooling passage layers (air flow path portions) 17 </ b> A to 17 </ b> C for circulating compressed air are alternately polymerized. It is configured. Further, the catalyst layers 1A to 1C and the cooling passage layers 17A to 17C are arranged so that the flow of the exhaust gas passing through the catalyst 1 and the cooling air passing through the cooling passage layers 17A to 17C are substantially orthogonal to each other. Yes.
[0051]
With such a configuration, the exhaust gas can be cooled via the catalyst 1.
Since the exhaust gas purification apparatus for a diesel engine as the second embodiment of the present invention is configured as described above, the following operation is performed.
First, exhaust gas discharged from the engine E drives the exhaust turbine 9T through the exhaust passage 2 and then flows into the catalyst 1 through the exhaust passage 16.
[0052]
Further, when the exhaust turbine 9T is driven by the exhaust gas, the compressor 9C is driven by this rotational driving force. Then, the air taken in via the air cleaner 15 is pressurized and supplied to the cooler 14 via the cooling air passage 17.
Here, since the cooler 14 is configured as the catalyst 1 having a cooling function, the compressed air passes through the cooling passage layers (air flow path portions) 17A to 17C of the catalyst 1 so that the exhaust gas in the catalyst 1 is exhausted. The temperature of is reduced.
[0053]
Further, the controller 7 controls the open / close state of the flow path switching valve 10 according to the exhaust gas temperature of the catalyst 1 and the engine operating state, thereby adjusting the amount of exhaust gas flowing through the bypass passage 13. Thereby, the flow rate of the exhaust gas for driving the exhaust turbine 9T is adjusted, the flow rate of the compressed air flowing through the cooling passage layers 17A to 17C is adjusted, and the temperature of the exhaust gas in the catalyst 1 is in an appropriate range. It is controlled to become.
[0054]
Therefore, in this embodiment, it is possible to obtain substantially the same effects as in the first implementation described above.
The cooling device 14 of the present embodiment is not limited to those described above, it may be applied cooler 14 as described for example in the first implementation embodiment. Further, the cooler 14 may be configured by using, as described in the second embodiment in the cooler 14 of the first implementation embodiment.
[0055]
【The invention's effect】
As described above in detail, according to the exhaust gas purification apparatus for a diesel engine of the present invention, the exhaust gas temperature can be controlled to the maximum efficiency temperature of the catalyst, so that the exhaust gas reduction effect, thermal degradation characteristics, sulfate generation amount, added HC amount Etc. can be greatly improved.
[0056]
Further, since the compressed air produced by the compressor is not returned to the engine intake air as in the conventional supercharging technology, the residual oxygen in the exhaust gas does not increase, and for example, in the case of a NOx catalyst, the catalyst efficiency does not decrease. There is also.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic diagram showing a main configuration of an exhaust emission control device for a diesel engine as a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing a flow path switching valve of the exhaust purification device for a diesel engine as the first embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view showing a main configuration of an air-cooled heat exchanger of the exhaust purification device for a diesel engine as the first embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view showing the main configuration of another example of the air-cooled heat exchanger of the exhaust purification device for a diesel engine as the first embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view showing the main configuration of another example of the air-cooled heat exchanger of the exhaust purification device for a diesel engine as the first embodiment of the present invention.
FIG. 6 is a schematic cross-sectional view showing the main configuration of another example of the air-cooled heat exchanger of the exhaust purification device for a diesel engine as the first embodiment of the present invention.
FIG. 7 is a diagram illustrating operating characteristics of the exhaust purification device for a diesel engine according to the first embodiment of the present invention.
FIG. 8 is a diagram illustrating operating characteristics of the exhaust purification device for a diesel engine according to the first embodiment of the present invention.
FIG. 9 is a diagram illustrating operating characteristics of the exhaust purification device for a diesel engine as the first embodiment of the present invention.
FIG. 10 is a schematic diagram showing a main configuration of an exhaust emission control device for a diesel engine as a second embodiment of the present invention.
FIG. 11 is a schematic perspective view showing a configuration of a catalyst of an exhaust emission control device for a diesel engine as a second embodiment of the present invention.
FIG. 12 is a schematic diagram showing a main part configuration of a conventional diesel engine exhaust gas purification device.
FIG. 13 is a schematic diagram showing operating characteristics of an exhaust emission control device for a conventional diesel engine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Catalyst 1A-1C Catalyst layer 2, 11, 16, 27 Exhaust passage 4 Bypass passage 5 Flow path switching valve 7 Controller 8 1st supercharger 8C Compressor 8T Exhaust turbine 9 2nd supercharger 9C Compressor 9T Exhaust turbine 10 Flow path switching valve (bypass valve)
12 Air supply passage 13 Bypass passage 14 Cooler as a cooling means (heat exchanger)
15 Air cleaner 17 Air passage for cooling (cooling passage)
17A-17C Cooling passage layer (air flow path part)
20 Inner pipe 21 Outer pipe 22 Turbine 23 Propeller 24 Intercooler 25, 25A Intake passage 26 Valve 100 Exhaust system S Control means

Claims (4)

A catalyst disposed in the exhaust passage of the diesel engine for purifying harmful components in the exhaust;
An exhaust turbine provided in the exhaust passage upstream of the catalyst and driven by exhaust pressure;
A compressor coupled to the exhaust turbine and driven to rotate by the exhaust turbine;
A bypass passage connecting the upstream side of the exhaust passage of the exhaust passage and the downstream side of the exhaust turbine of the exhaust passage to bypass the exhaust turbine;
A bypass valve that controls the flow rate of exhaust gas that bypasses the exhaust turbine and flows through the bypass passage;
Cooling means for cooling the exhaust passage upstream of the catalyst or the catalyst with compressed air obtained from the compressor;
Control means for controlling the opening of the bypass valve so that the exhaust gas temperature or the catalyst temperature flowing into the catalyst becomes the optimum active range temperature of the catalyst,
Control means is arranged to control the opening and closing state of the bypass valve in accordance with the exhaust temperature and engine operating conditions upstream of the catalyst Rutotomoni,
The cooling means is configured to cool the catalyst by supplying the compressed air to the catalyst without mixing the compressed air obtained by the compressor and the exhaust gas flowing through the exhaust passage. Diesel engine exhaust purification system. The cooling means
It is configured as a heat exchanger having a double-pipe structure consisting of an inner pipe and an outer pipe formed in the exhaust passage upstream of the catalyst,
The compressed air from the compressor is supplied to the outer pipe of the double pipe structure, and the exhaust gas is circulated through the inner pipe of the double pipe structure. The diesel engine exhaust gas purification apparatus as described. The catalyst has a plurality of catalyst layers, and the catalyst is formed by alternately polymerizing the catalyst layers and air flow passage portions through which compressed air from the compressor flows. Item 3. Exhaust gas purification device for diesel engine according to item 1 or 2. The catalyst is configured as an oxidation catalyst;
In the purification action by the oxidation catalyst,
The flow rate of the compressed air is controlled by the control means so that an exhaust gas temperature flowing into the catalyst falls within a temperature range where no sulfate is generated in the oxidation catalyst. Item 4. The exhaust purification device for a diesel engine according to any one of Items 1 to 3.

Images