JP5844997B2 - Equipment for evaluating the performance of exhaust gas purification catalysts - Google Patents

Description

  The present invention relates to an apparatus for evaluating the performance of an exhaust gas purification catalyst provided in an exhaust system of an internal combustion engine such as an automobile engine.

As shown in FIG. 10, a conventional apparatus of this type generally has an exhaust gas introduction pipe 20 into which simulated exhaust gas is introduced from one end side, a diameter larger than that of the exhaust gas introduction pipe 20, and exhaust gas purification inside. A catalyst housing pipe 22 in which the catalyst 21 is housed, and a taper pipe 23 that connects the other end of the exhaust gas introduction pipe 20 and one end of the catalyst housing pipe 22 are provided (see, for example, Patent Document 1).

And when performance evaluation of an exhaust gas purification catalyst is performed using this apparatus, simulated exhaust gas containing the same component as exhaust gas from an internal combustion engine is usually used. The simulated exhaust gas is a mixture of various components contained in the exhaust gas of the internal combustion engine, such as NO _X , CO ₂ , HC, H ₂ O, etc., with nitrogen gas so as to have a concentration similar to the concentration in the exhaust gas. In this case, the simulated exhaust gas is brought to a temperature state similar to the actual exhaust gas temperature, and the catalyst to be evaluated is heated to a predetermined temperature, and an adsorption reaction is performed in the catalyst.

The NO _X storage reduction catalyst captures (occludes) NO _X when the air-fuel ratio of the inflowing exhaust gas is lean, while it captures (occludes) NO _X when the air-fuel ratio of the inflowing exhaust gas is stoichiometric or rich. Reduce.
The internal combustion engine equipped with the NO _X storage reduction catalyst operates lean, and when the exhaust gas purification performance of the catalyst is reduced, the operation state is switched so that the air-fuel ratio becomes stoichiometric or rich, so that lean It is performed purification of the NO _X in the exhaust gas.

Thus, in an internal combustion engine provided with _the NO _X storage reduction catalyst, and the lean, by the switching of the stoichiometric or rich is optimally controlled, have been achieved reduction of the NO _X in the exhaust gas, in this case, in particular, When switching from lean to stoichiometric or rich is carried out quickly and efficiently improves the purification efficiency of NO _X, the low fuel consumption is achieved.

Correspondingly, in the conventional performance evaluation device, if the evaluation object of the NO _X occluding and reducing catalyst, and the lean simulated exhaust gas catalyst housing pipe 22 from the exhaust gas inlet pipe 20, the stoichiometric or rich simulated exhaust gas and a constant timing In this way, the performance of the catalyst 21 is evaluated. In this case, in order to increase the accuracy of the performance evaluation of the catalyst 21, how is the gas atmosphere before passing through the catalyst 21 corresponding to switching from lean simulated exhaust gas to stoichiometric or rich simulated exhaust gas or vice versa? It is important to be able to replace quickly and uniformly over the entire cross section of the catalyst.

  However, in the performance evaluation apparatus, since the exhaust gas introduction pipe 20 has a smaller diameter than the catalyst housing pipe 22, the flow rate of the simulated exhaust gas G discharged from the exhaust gas introduction pipe 20 into the catalyst housing pipe 22 as shown in FIG. Gradually decreases as the distance from the center of the catalyst housing tube 22 in the radial direction increases. As a result, when switching from lean simulated exhaust gas to stoichiometric or rich simulated exhaust gas, or vice versa, the gas atmosphere is replaced relatively quickly in the central portion in the catalyst housing tube 22, but the catalyst housing tube The gas atmosphere is not easily replaced near the inner wall of 22. This becomes more prominent as the diameter of the catalyst, and hence the diameter of the catalyst housing tube 22, increases.

  In general, the catalyst to be evaluated is arranged at a position not far from the inlet of the catalyst housing pipe, so that when it is switched from lean to stoichiometric or rich or vice versa, the gas atmosphere before passing through the catalyst is reduced. It is not replaced quickly and uniformly throughout the entire cross section of the catalyst, and in particular, this becomes more prominent as the diameter of the catalyst to be evaluated becomes larger, resulting in a problem that performance evaluation cannot be performed accurately. It was.

  In this case, it is conceivable to lengthen the taper pipe and increase the distance from the outlet of the exhaust gas introduction pipe to the catalyst, but it is necessary to increase the size of the heating unit correspondingly, etc. After switching from lean to stoichiometric or rich, or vice versa, it takes time for the switched gas atmosphere to reach the catalyst, which is an effective solution. Absent.

Japanese Patent No. 4194581

  Therefore, the object of the present invention is to quickly and evenly replace the gas atmosphere before passing through the catalyst to be evaluated over the entire cross section of the catalyst when switching from lean to stoichiometric or rich or vice versa. It is to provide a compact device.

In order to solve the above-mentioned problems, the present invention is an apparatus for evaluating the performance of an exhaust gas purifying catalyst, wherein a simulated exhaust gas supply unit that switches between lean simulated exhaust gas and stoichiometric or rich simulated exhaust gas, and one end of the simulated exhaust gas. An exhaust gas introduction pipe connected to the supply unit, a catalyst housing pipe having a larger diameter than the exhaust gas introduction pipe, in which the exhaust gas purification catalyst is housed, and the other end of the exhaust gas introduction pipe and the catalyst housing pipe And a heating part disposed outside the exhaust gas introduction pipe, the pipe connection part, and the catalyst housing pipe, the catalyst housing pipe or the pipe connection part. A circular porous rectifying plate having a plurality of vent holes disposed opposite to the exhaust gas purification catalyst at a position spaced from the exhaust gas purification catalyst to the exhaust gas introduction pipe side inside It is obtained by constituting the apparatus characterized by a.

  In the above configuration, preferably, the porous rectifying plate has the plurality of vent holes having the same shape arranged concentrically, or the surface of the porous rectifying plate has a central circular region and an outer side thereof. The vent holes belonging to at least one annular region and all belonging to one region have the same shape, and the opening area of the vent hole belonging to the region increases as the region moves away from the center of the porous rectifying plate. Is getting bigger. Preferably, the air hole has a slit shape, or the porous rectifying plate is made of a mesh plate or a honeycomb plate.

In the above configuration, one end of the pipe connection portion is connected to the other end of the exhaust gas introduction pipe, and after extending from the connection portion with the exhaust gas introduction pipe, the other end is connected to one end of the catalyst housing pipe. The tube connection portion may be filled with an inert material made of granular quartz or ceramic.
Alternatively, the pipe connecting portion has a diameter corresponding to the inner diameter of the catalyst housing pipe, forms a disk shape that seals one end opening of the catalyst housing pipe, and further, in the center thereof, the exhaust gas introduction pipe A circular opening having a diameter corresponding to the inner diameter may be provided, and the other end of the exhaust gas introduction pipe may be connected to the circular opening.

  In the above configuration, it is preferable that the exhaust gas introduction pipe is composed of a venturi pipe, an orifice pipe or a static mixer, or the inside of the exhaust gas introduction pipe has a partially honeycomb structure.

According to the present invention, the space from the outlet of the exhaust gas introduction pipe to the exhaust gas purification catalyst in the device by the porous rectification plate is the first space from the outlet of the exhaust gas introduction pipe to the porous rectification plate and the porous rectification plate. It is divided into two spaces, the second space leading to the exhaust gas purification catalyst. A part of the simulated exhaust gas discharged from the outlet of the exhaust gas introduction pipe directly passes through the vent hole of the porous rectifying plate, but the remaining part is once bounced back to the porous rectifying plate, thereby Turbulence occurs. Due to this turbulent flow, the simulated exhaust gas discharged from the outlet of the exhaust gas introduction pipe uniformly spreads not only in the central part but also in the peripheral part of the first space, and then through the ventilation holes of the porous rectifying plate, It is discharged into the second space at a substantially uniform flow rate throughout the plate.

Thus, when switching from lean simulated exhaust gas to stoichiometric or rich simulated exhaust gas, or vice versa, the gas atmosphere before passing through the catalyst to be evaluated is quickly and uniformly replaced across the entire cross section of the catalyst, Thereby, the accuracy of performance evaluation is improved.
The present invention can be applied not only to an apparatus for evaluating the performance of an exhaust gas purification catalyst, but also to an exhaust gas purification apparatus attached to an exhaust system of an internal combustion engine.

It is a longitudinal cross-sectional view which shows schematic structure of the apparatus which evaluates the performance of the exhaust gas purification catalyst by one Example of this invention. FIG. 2 is a longitudinal sectional view similar to FIG. 1 of an apparatus for evaluating the performance of an exhaust gas purifying catalyst according to another embodiment of the present invention. It is a longitudinal cross-sectional view which shows the inflow state of exhaust gas or simulation exhaust gas in the apparatus of FIG. It is a top view which illustrates the structure of a porous baffle plate. It is a top view which illustrates the structure of a porous baffle plate. It is the longitudinal cross-sectional view which illustrates the structure of an exhaust gas introduction pipe, and the top view seen from each arrow direction. It is a longitudinal cross-sectional view which shows schematic structure of the apparatus which evaluates the performance of the exhaust gas purification catalyst by another Example of this invention. It is the graph which plotted the change of the gas concentration just before a catalyst with progress of time after switching from lean simulated exhaust gas to rich simulated exhaust gas. It is the graph which plotted the change of the gas concentration just before a catalyst at the time of switching switching of lean simulated exhaust gas and rich simulated exhaust gas. It is a longitudinal cross-sectional view which shows the schematic structure of the conventional catalyst performance evaluation apparatus, and the inflow state of simulation exhaust gas.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view showing a schematic configuration of an apparatus for evaluating the performance of an exhaust gas purification catalyst according to one embodiment of the present invention.
As shown in FIG. 1, an apparatus for evaluating the performance of an exhaust gas purifying catalyst according to the present invention includes a simulated exhaust gas supply unit (not shown) that switches between lean simulated exhaust gas and stoichiometric or rich simulated exhaust gas, and one end 1a. An exhaust gas introduction pipe 1 connected to the simulated exhaust gas supply unit, a catalyst housing pipe 2 having a larger diameter than the exhaust gas introduction pipe 1 and containing the exhaust gas purification catalyst 3 therein, and the other end 1b of the exhaust gas introduction pipe 1 And a heating section 5 disposed outside the exhaust pipe 1, the pipe connection section 4, and the catalyst housing pipe 2.

  In this embodiment, the pipe connection portion 4 has one end 4 a connected to the other end 1 b of the exhaust gas introduction pipe 1, and extends from the connection portion with the exhaust gas introduction pipe 1 in a divergent shape, and then the other end 4 b of the catalyst housing pipe 2. It has a tapered tubular shape connected to one end 2a.

  The exhaust gas purifying catalyst 3 is previously attached to the holder 6 outside in advance, and is then inserted into the catalyst housing tube 2 while being held by the holder 6, and is disposed at a predetermined position in the catalyst housing tube 2.

The apparatus according to the present invention also has a plurality of vent holes arranged facing the exhaust gas purification catalyst 3 at a position spaced from the exhaust gas purification catalyst 3 inside the catalyst housing pipe 2 to the exhaust gas introduction pipe 1 side. A circular perforated flow rectifying plate 7 is provided.
In this embodiment, the porous rectifying plate 7 is attached in the vicinity of the inlet of the catalyst housing pipe 2 so as to partition the inside of the catalyst housing pipe up and down. Instead, as shown in FIG. It may be attached to.
Further, the porous rectifying plate 7 may be disposed inside the catalyst housing pipe 2 as in this embodiment, or is attached inside the pipe connecting portion 4 so as to partition the inside of the pipe connecting portion up and down. Also good.

According to the present invention, the space from the outlet 1 c of the exhaust gas introduction pipe 1 to the exhaust gas purification catalyst 3 in the apparatus by the porous rectification plate 7 is the first from the outlet 1 c of the exhaust gas introduction pipe 1 to the porous rectification plate 7. The space 8 and the second space 9 extending from the porous rectifying plate 7 to the exhaust gas purification catalyst 3 are divided into two spaces.
As shown in FIG. 3, a part of the simulated exhaust gas G discharged from the outlet 1 c of the exhaust gas introduction pipe 1 directly passes through the vent hole of the porous rectifying plate 7, while the remaining part is the porous rectifying plate 7. , So that turbulence is generated in the first space 8. Due to this turbulent flow, the simulated exhaust gas G discharged from the outlet 1c of the exhaust gas introduction pipe 1 uniformly spreads not only in the central portion of the first space 8 but also in the peripheral portion, Then, it is discharged into the second space 9 at a substantially uniform flow rate over the entire porous rectifying plate 7.

The size, number and arrangement pattern of the vent holes of the porous rectifying plate 6 are not particularly limited as long as the function and effect of the porous rectifying plate 7 are achieved.
For example, as shown in FIG. 4A, a plurality of vent holes 10 having the same shape may be provided concentrically in the porous rectifying plate 7, or as shown in FIG. 4B, the surface of the porous rectifying plate 7 is The central circular region 11a is divided into at least one annular region 11b on the outer side, and the air holes 12a; 12b belonging to the one region 11a; 11b all have the same shape, and the region 11a; The configuration may be such that the opening area of the vent holes 12a; 12b belonging to the regions 11a;

  Further, for example, as shown in FIG. 5A, the porous rectifying plate 7 may have a slit-shaped air hole 13, or the porous rectifying plate 7 is made of a honeycomb plate as shown in FIG. 5B. It may be made of a mesh plate as shown in FIG. 5C.

  Although not shown in the drawings, when the pipe connecting portion 4 is tapered as in this embodiment, the pipe connecting portion 4 may be filled with an inert material made of granular quartz or ceramic. Good. This inert material makes the simulated exhaust gas introduced into the catalyst housing pipe more uniform.

According to another preferred embodiment of the present invention, as shown in FIG. 6, the exhaust gas introduction pipe 1 comprises an orifice pipe (see FIG. 6A) or a venturi pipe (see FIG. 6B) or a static mixer (see FIG. 6E). ing. Alternatively, the inside of the exhaust gas introduction pipe 1 partially has a honeycomb structure 14 (see FIG. 6C). Alternatively, the exhaust gas introduction pipe 1 includes a plurality of sub pipes 15 arranged in parallel in the axial direction (see FIG. 6D).
As a result, the exhaust gas introduction pipe 1 can be shortened, thereby reducing the size of the heating unit 5 and further reducing the size and cost of the apparatus.

  Thus, according to the present invention, the catalyst performance evaluation apparatus can be made more compact and less expensive than the conventional example, and at the time of switching from lean simulated exhaust gas to stoichiometric or rich simulated exhaust gas, or vice versa, The gas atmosphere before passing through the catalyst is quickly and uniformly replaced throughout the entire cross section of the catalyst, thereby improving the accuracy of the performance evaluation.

FIG. 7 is a longitudinal sectional view showing a schematic configuration of an apparatus for evaluating the performance of an exhaust gas purifying catalyst according to another embodiment of the present invention. This embodiment differs from the embodiment shown in FIG. 1 only in the configuration of the pipe connecting portion. Therefore, in FIG. 7, the same components as those shown in FIG.
Referring to FIG. 7, in this embodiment, the pipe connecting portion 4 ′ has a diameter corresponding to the inner diameter of the catalyst housing pipe 2 and has a disk shape that seals one end opening of the catalyst housing pipe 2. In the center, a circular opening 16 having a diameter corresponding to the inner diameter of the exhaust gas introduction pipe is provided, and the other end 1b of the exhaust gas introduction pipe 1 is connected to the circular opening 16.
Needless to say, this embodiment can provide the same effects as those of the embodiment shown in FIG.

Next, several experiments were conducted to confirm the operational effects of the catalyst performance evaluation apparatus according to the present invention.
(Example)
An apparatus having the perforated flow straightening plate 7 shown in FIG. 4A and having the same configuration as that of FIG. 1 was manufactured as an example. All experiments were performed with the catalyst 3 removed from the catalyst housing tube 2.
In addition, the dimension of the principal part of this apparatus is as follows.
Inside diameter of exhaust gas introduction pipe 1 = 10 mm
Inner diameter of catalyst housing tube 2 = 58 mm
Distance from outlet 1c of exhaust gas introduction pipe 1 to porous rectifying plate 7 d1 = 31 mm
Distance from porous rectifying plate 7 to catalyst front surface d2 = 20 mm
Length d4 = 170 mm from the porous rectifying plate 7 to the lower end of the catalyst housing pipe 2
Further, the gas concentration is measured at a position in the center of the pipe (point P1 in FIG. 1) and a position in the vicinity of the wall of the pipe (point P2 in FIG. 1) separated by a distance d3 = 10 mm in front of the porous rectifying plate 7. Therefore, a high-speed FID analyzer was arranged.
(Comparative example)
A device obtained by removing the porous rectifying plate 7 from the apparatus of the example was used as a comparative example.

[Experiment 1]
In the apparatus of the example, rich simulated exhaust gas (C ₃ H ₆₎ was introduced from the state in which N ₂ gas was introduced at a rate of 6 liters / minute as simulated simulated exhaust gas into simulated exhaust gas (N ₂ gas of 30 liters / minute). 1.2% containing N ₂ gas, switching 6 liters / minute), the as time elapses after the switching, to measure changes in gas concentration of the point P1 and the point P2.
Moreover, the measurement was performed under the same conditions for the apparatus of the comparative example.

  The experimental results are shown in the graph of FIG. From the graph of FIG. 8, in the apparatus of the example, when switching from lean simulated exhaust gas to rich simulated exhaust gas, the gas atmosphere before passing through the catalyst is quickly and uniformly from the center of the catalyst housing pipe 2 to the pipe wall surface. It was found that it was replaced.

[Experiment 2]
In the apparatus of the example, the simulated exhaust gas (N ₂ gas is 30 liters / minute), lean simulated exhaust gas (N ₂ gas, 6 liters / minute) and rich simulated exhaust gas (N ₂ gas containing 1.2% of C ₃ H ₆ ) , 6 liters / minute), the change in the gas concentration at the point P2 was measured while alternately switching at a rate of 0.7 seconds for the former and 0.4 seconds for the latter.
Moreover, the measurement was performed under the same conditions for the apparatus of the comparative example.

  The measurement results are shown in the graph of FIG. From the graph of FIG. 9, it was found that in the apparatus of the example, the gas atmosphere before passing through the catalyst was quickly replaced when switching between the lean simulated exhaust gas and the rich simulated exhaust gas.

DESCRIPTION OF SYMBOLS 1 Exhaust gas introduction pipe 2 Catalyst accommodating pipe 3 Exhaust gas purification catalyst 4 Pipe connection part 5 Heating part 6 Holder 7 Porous baffle plate 8 1st space 9 2nd space 10 Vent hole 11a, 11b Area | region 12a, 12b Vent hole 13 Vent hole 14 Honeycomb structure 15 Sub pipe 16 Circular opening 20 Exhaust gas introduction pipe 21 Exhaust gas purification catalyst 22 Catalyst housing pipe 23 Taper pipe G Simulated exhaust gas or exhaust gas

Claims (9)

An apparatus for evaluating the performance of an exhaust gas purification catalyst,
A simulated exhaust gas supply unit that switches between lean simulated exhaust gas and stoichiometric or rich simulated exhaust gas; and
An exhaust gas introduction pipe having one end connected to the simulated exhaust gas supply unit ;
A catalyst housing pipe having a larger diameter than the exhaust gas introduction pipe, and containing the exhaust gas purification catalyst therein;
A pipe connection part for connecting the other end of the exhaust gas introduction pipe and one end of the catalyst housing pipe;
In what comprises the exhaust gas introducing pipe, the pipe connecting portion and a heating portion arranged outside the catalyst housing pipe,
A circular shape having a plurality of vent holes disposed facing the exhaust gas purification catalyst at a position spaced from the exhaust gas purification catalyst to the exhaust gas introduction tube side inside the catalyst housing pipe or the pipe connection portion. An apparatus comprising a porous baffle plate.   2. The apparatus according to claim 1, wherein the perforated baffle plate has the plurality of vent holes having the same shape arranged concentrically.   The surface of the porous rectifying plate is divided into a central circular region and at least one annular region outside thereof, and the air holes belonging to one of the regions all have the same shape, and the region is formed of the porous rectifying plate. The apparatus according to claim 1, wherein an opening area of the air hole belonging to the region increases as the distance from the center increases.   The apparatus according to claim 1, wherein the vent hole has a slit shape.   2. The apparatus according to claim 1, wherein the porous rectifying plate is made of a mesh plate or a honeycomb plate.   The pipe connecting portion has a tapered tubular shape in which one end is connected to the other end of the exhaust gas introduction pipe, extends from the connection portion with the exhaust gas introduction pipe in a divergent shape, and the other end is connected to one end of the catalyst housing pipe. 6. The device according to claim 1, wherein the device is provided.   The pipe connecting portion has a diameter corresponding to the inner diameter of the catalyst housing pipe, has a disk shape that seals one end opening of the catalyst housing pipe, and further, in the center, has an inner diameter of the exhaust gas introduction pipe. 6. The device according to claim 1, wherein a circular opening having a corresponding diameter is provided, and the other end of the exhaust gas introduction pipe is connected to the circular opening.   The apparatus according to any one of claims 1 to 7, wherein the exhaust gas introduction pipe comprises a venturi pipe, an orifice pipe or a static mixer.   The device according to any one of claims 1 to 7, wherein the inside of the exhaust gas introduction pipe has a partially honeycomb structure.