JPH0743303B2 - Exhaust gas measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas measuring device, and in particular, it extracts a part of engine exhaust gas and guides it to a mini-dilution tunnel. The present invention relates to a device for diluting and measuring a part of the diluted gas by sampling means, which is suitable for measuring particulates in exhaust gas.

[Outline of Invention]

When performing intermittent measurement of particulates in a split flow mini-dilution tunnel for particulates measurement, the amount of diluent gas flowing in the tunnel changes, which affects the gas concentration that determines the split ratio and causes errors in particulate measurement. In consideration of the occurrence, the gas flow rate does not change between measurement and non-measurement, and the measurement accuracy is improved by suppressing the change in the dilution rate.

[Conventional technology]

FIG. 4 shows a device for measuring the particulates in the exhaust gas of a conventional diesel engine. A divider 3 is connected to the exhaust pipe 2 through which the exhaust gas of the diesel engine 1 passes, and A part of the exhaust gas is extracted through the extraction pipe 4 by the divider 3. The extracted exhaust gas is diluted by the mini dilution tunnel 5. A heat exchanger 6 and a blower 7 are connected to the downstream side of the tunnel 5 so as to generate a gas flow having a constant flow rate. Then, the sampling pump 8 sucks a part of the diluted gas in the mini-dilution tunnel, and the filter 9 captures and measures the particulates in the gas. A three-way solenoid valve 10 is connected between the filter 9 and the sampling pump 8. When sampling is not performed, the solenoid valve 10 is switched and the air intake 11 takes in air, I am trying to stop sampling.

[Problems to be solved by the invention]

A drawback of the particulate measuring device using such a mini-dilution tunnel 5 is that when intermittent measurement of particulates is performed, the amount of diluent gas flowing in the tunnel 5 changes, which affects the gas concentration that determines the division ratio. Therefore, an error will occur in the measurement of particulates. Generally, when performing continuous measurement of particulates, the gas flow rate in the mini-dilution tunnel 5 is always constant, but when performing intermittent measurement, the gas flow rate in the tunnel 5 is The switching of the three-way solenoid valve 10 changes the amount of diluent gas.

FIG. 5 shows such a change in the amount of gas, and the amount of gas between the mixing point of the exhaust gas at the outlet of the extraction pipe 4 of the tunnel 5 and the sampling point for sampling particulates is It is the sum of the flow rate V generated by the roots blower 7 and the flow rate V generated by the sampling pump 8 for sampling the particulates. In the case of intermittent measurement, it changes by the ON-OFF amount of the sampling flow rate v. Therefore, the exhaust gas concentration that determines the split ratio, that is, the concentration of nitrogen oxides, changes, which affects the measurement of the particulate emission amount.

In particular, one of the particulate test regulation test modes currently under study in Europe is the exhaust test gas for a certain period of time in all test modes as shown in Fig. 6 is evaluated on one filter. The test method is included. If such a test is performed using the mini dilution tunnel 5, the particulate sampling flow rate v
Is not negligible compared to the flow rate by the blower 7, the exhaust gas dilution rate changes between when particulates are collected and when not collected,
Accurate measurement cannot be performed due to the response delay of the analyzer when calculating the division ratio from the gas concentration to the mini tunnel.

The sampling pump 8 shown in FIG. 4 has inertia, and since there is a time delay from the start of rotation until it rises to a constant flow rate, when performing intermittent measurement of particulates, the sampling pump 8 should always be rotated. The three-way solenoid valve 10 sucks exhaust gas into the filter 9 only when measuring, and sucks fresh air from the air intake 11 when not measuring.

Therefore, the amount of exhaust gas supplied by the extraction pipe 4 and the blower 7 both when the particulate matter is measured and when it is not measured.
Since the flow rate V generated by each is constant, when the sampling gas amount v is sucked from the mini tunnel 5 at the time of measurement, the amount of air flowing into the tunnel 5 from the inlet side of the mini dilution tunnel 5 is more than that at the time of non-measurement. Also, at the time of measurement, only v increases and the dilution rate changes. The change with time of the dilution gas concentration is shown in FIG. 7. If the measurement time is short due to the response delay of the analyzer 12, the accurate division ratio cannot be measured.

The present invention has been made in view of the above problems, and improves the measurement accuracy by suppressing the change in the dilution rate that occurs when intermittently measuring exhaust gas, especially particulates, and at the same time, an expensive pump It is an object of the present invention to provide an exhaust gas measuring device capable of measuring the background concentration of particulates without adding a flow meter or a flow meter.

[Means for solving problems]

According to a first aspect of the present invention, a part of engine exhaust gas is extracted and guided to a mini-dilution tunnel, diluted by the mini-dilution tunnel, and a part of the diluted gas is sampled by a sampling means. In the device described above, pseudo sampling means for extracting the same amount of diluent gas as the sampling means is provided, and when the sampling means does not perform sampling, the pseudo sampling means extracts diluent gas from the mini-dilution tunnel. is there.

In a second aspect of the invention, a part of the exhaust gas of the engine is extracted, guided to a mini dilution tunnel, diluted by the mini dilution tunnel, and a part of the diluted gas is sampled by a sampling means. In such a device, the dilution gas sampled by the sampling means is returned to the downstream side of the sampling position of the mini-dilution tunnel, and the sampling pump is connected to the pseudo-pipe through a switching valve. During non-measurement, the pseudo pipe sucks gas from the upstream side of the introduction position of the exhaust gas of the mini-dilution tunnel and returns the sucked gas to the upstream side of the introduction position of the exhaust gas. It was done.

[Action]

Therefore, in both the first invention and the second invention, the amount of gas flowing in the mini-dilution tunnel does not change between the time of measurement and the time of non-measurement, and the gas concentration that determines the division ratio is affected. Stop giving. Therefore, it becomes possible to suppress a change in the dilution rate when performing intermittent measurement of particulates.

〔Example〕

FIG. 1 shows an exhaust gas measuring device according to a first embodiment of the present invention, and this measuring device measures exhaust gas emitted from a diesel engine 15. An exhaust pipe 17 is connected to an exhaust manifold 16 mounted on the side surface of the diesel engine 15. An exhaust gas divider 18 is connected to an intermediate position of the exhaust pipe 17. Further, the gas analyzer 19 is directly connected to the exhaust pipe 17 via the narrow pipe 20 on the downstream side of the divider 18.

Furthermore, this measuring device is equipped with a mini-dilution tunnel 23 for diluting the exhaust gas, so that the exhaust gas extracted by the extraction pipe 24 at the divider 18 is guided into this tunnel 23. A heat exchanger 25 and a roots blower 26 are connected to the exit side of the tunnel 23, respectively. A dilution gas analyzer 27 is connected to the downstream side of the tunnel 23 via a thin tube 28.

A sampling tube 29 is further inserted in the mini dilution tunnel 23. A particulate filter 30 is attached to the sampling pipe 29, and is connected to a sampling pump 32 via a three-way solenoid valve 31. A flow meter 33 is connected to the downstream side of the sampling pump 32. A pseudo sampling tube 34 is connected between the three-way solenoid valve 31 and the mini-dilution tunnel 23, and a dummy filter 35 is attached to the sampling tube 34.

In the above structure, the exhaust gas generated by the operation of the diesel engine 15 is exhausted through the exhaust manifold 16 and the exhaust pipe 17, and the exhaust pipe 24 inserted in the divider 18 at this time Part of the exhaust gas is extracted and guided to the mini dilution tunnel 23. The concentration of the exhaust gas discharged from the engine 15 is directly measured by the gas analyzer 19. Since the roots blower 26 on the exit side of the mini-dilution tunnel 23 is operating, air is taken into the mini-tunnel 23 from its upstream side, and this air is introduced through the extraction pipe 24. The exhaust gas will be diluted. The diluted exhaust gas concentration in the mini tunnel 23 is measured by a diluted gas analyzer 27.

The measurement of the particulates by this device is performed by operating the sampling pump 32 and sucking the diluent gas from the mini-dilution tunnel 23 through the sampling pipe 29. At this time, the three-way solenoid valve 31 is switched to the sampling tube 29 side. Therefore, the particulates in the exhaust gas diluted at this time are captured by the particulate filter 30. The sampling flow rate by the sampling pump 32 is detected by the flow meter 33.

In the exhaust gas measuring device that performs the measurement as described above, the pseudo sampling pipe 34 is connected in parallel to the sampling pipe 29, and the sampling pipe 34
Is provided with a dummy filter 35. The three-way solenoid valve 31 can be switched to the pseudo sampling pipe 34 side except when the particulates are measured. That is, the sampling pump 32 is always operated, and measurement and non-measurement of particulates are performed by switching the three-way solenoid valve 31. Therefore, as shown in FIG. 2, the flow rate of gas in the mini-tunnel 23 is the sum of the flow rate V of the roots blower 26 and the sampling flow rate v of the sampling pump 32. The accuracy of curate measurement is improved. That is, by providing the dummy filter 35 in addition to the particulate filter 30 and allowing the diluent gas to pass through the dummy filter 35 except during measurement, it is possible to always flow a constant amount of the diluent gas.

Next, a second embodiment will be described with reference to FIG. In this embodiment, in addition to the first three-way solenoid valve 31, another three-way solenoid valve
38, and the three-way solenoid valve 38 is connected to the downstream side of the flow meter 33. Then, one outlet side of the three-way solenoid valve 38 is connected to the return pipe 39, and the outlet side of the return pipe 39 is opened to the upstream portion of the heat exchanger 25 of the mini dilution tunnel 23. Also the first 3-way solenoid valve
A pseudo sampling tube 34 having a dummy filter 35 is connected to another inlet side port of 31 and the tip end of this sampling tube 34 is provided at the upstream side of the open end of the extraction tube 24 of the mini-dilution tunnel 23. It is open to the upstream. A pseudo return pipe 40 is connected to the other outlet side of the further three-way solenoid valve 38.
Is opened inside the mini-tunnel 23 slightly upstream of the outlet side of the extraction pipe 24.

In the above configuration, the first three-way solenoid valve 31 is switched to the sampling pipe 29 side, and the second three-way solenoid valve 38 is switched to the return pipe 39 side when measuring the particulate filter. . Therefore, like the solid arrow 41,
The dilution gas taken out from the mini-dilution tunnel 23 is used as a sampling tube 29, a particulate filter 30, and 3.
It is returned to the inside of the mini-dilution tunnel 23 through the one-way solenoid valve 31, the sampling pump 32, the flow meter 33, the three-way solenoid valve 38, and the return pipe 39. At this time, the particulates in the diluent gas are captured by the filter 30, and the captured particulates are taken out and measured later.

On the other hand, when the particulates are not measured, the pair of three-way solenoid valves 31, 38 are both switched to the opposite side, that is, the pseudo pipeline side, and the inside of the tunnel 23 is indicated by an arrow 42 shown by a dotted line. Part of the gas will flow. That is, the gas taken out by the pseudo sampling pipe 34 from the portion close to the inlet side of the mini-dilution tunnel 23 is the dummy filter 35, the three-way solenoid valve 31, the sampling pump 3
2, the flow meter 33, the three-way solenoid valve 38, and the pseudo return pipe 40 are returned to the upstream side of the outlet of the extraction pipe 24 of the mini dilution tunnel 23.

Therefore, according to such an apparatus, when measuring the particulates, the gas is sucked from the sample probe 29, the gas that has passed through the particulate filter 30 is returned to the downstream side of the sample probe 29, and the dilution air is supplied when the particulates are not measured. The tunnel 23 is sucked in before the discharge part of the extraction pipe 24, and is returned before the discharge part of the extraction pipe 24. Therefore, the dilution air amount V becomes constant both when the particulate matter is measured and when it is not measured, and it becomes possible to perform measurement with an accurate division ratio. In addition, the dummy filter 35
By putting in, it becomes possible to measure the background value of particulates without adding a pump or a flow meter. Therefore, it is possible to provide an exhaust gas measuring device that improves the measurement accuracy by suppressing the change in the dilution rate that occurs when the particulates are intermittently measured, and that can also measure the background concentration of the particulates.

〔The invention's effect〕

As described above, in the first aspect of the invention, the pseudo sampling means for extracting the same amount of diluent gas as the sampling means is provided, and when the sampling means does not perform sampling, the pseudo sampling means extracts the diluent gas from the mini-dilution tunnel. It is a thing. Therefore, the solution that the amount of dilution gas flowing in the mini dilution tunnel is always constant between measurement and non-measurement, affects the gas concentration that determines the split ratio, and causes an error in particulate measurement. It becomes possible to do.

According to the second invention, the dilution gas sampled by the sampling means is returned to the downstream side of the sampling position of the mini dilution tunnel,
Furthermore, a pseudo pipeline is connected to the sampling pump via a switching valve.When not measuring, the pseudo pipeline draws in gas from the upstream side of the exhaust gas introduction position of the mini-dilution tunnel and introduces it from the exhaust gas introduction position. Is designed to return this gas to the upstream side. Therefore, the gas extracted from this mini-dilution tunnel is returned to the mini-dilution tunnel both during measurement and during non-measurement, and the amount of diluent gas flowing in the mini-dilution tunnel is different from that during measurement. The measurement accuracy can be improved by suppressing the change in the dilution rate without changing between when the measurement is not performed.

[Brief description of drawings]

FIG. 1 is a block diagram of an exhaust gas measuring apparatus according to a first embodiment of the present invention, FIG. 2 is a graph showing a flow rate of a dilution gas of the apparatus, and FIG. 3 is a block of a measuring apparatus according to the second embodiment. Fig. 4 is a block diagram of a conventional exhaust gas measuring device, Fig. 5 is a graph showing changes in the gas flow rate during intermittent measurement by this device, Fig. 6 is a graph in the test mode, and Fig. 7 is It is a graph which shows transition of a dilution gas mode. The names of the main parts in the drawings are as follows. 15 …… Diesel engine 17 …… Exhaust pipe 18 …… Exhaust gas divider 23 …… Mini dilution tunnel 24 …… Extraction pipe 26 …… Roots blower 29 …… Sampling pipe 30 …… Particulate filter 31 …… 3 ways Solenoid valve 32 …… Sampling pump 34 …… Pseudo sampling tube 35 …… Dummy filter 38 …… Three-way solenoid valve 39 …… Return tube 40 …… Pseudo return tube

Claims (2)

[Claims] 1. A part of engine exhaust gas is extracted and guided to a mini-dilution tunnel, diluted by the mini-dilution tunnel, and a part of the diluted gas is sampled by a sampling means. In the above device, pseudo sampling means for extracting the same amount of diluent gas as the sampling means is provided, and when the sampling means does not sample, the pseudo sampling means extracts the diluent gas from the mini-dilution tunnel. Exhaust gas measuring device. 2. A part of the exhaust gas of the engine is extracted and guided to a mini dilution tunnel, diluted by the mini dilution tunnel, and a part of the diluted gas is sampled by a sampling means. In the device described above, the dilution gas sampled by the sampling means is returned to the downstream side of the sampling position of the mini dilution tunnel, and a pseudo pump is connected to the sampling pump via a switching valve. At the time of measurement, the pseudo pipe sucks gas from the upstream side of the introduction position of the exhaust gas of the mini-dilution tunnel and returns the sucked gas to the upstream side of the introduction position of the exhaust gas. Exhaust gas measuring device characterized by.