JP3597991B2 - Gas mixing confirmation method in gas flow measurement using gas trace method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention confirms that a trace gas (helium gas) of a constant flow rate injected into a gas (hereinafter, referred to as an exhaust gas) discharged from an internal combustion engine such as an automobile engine is sufficiently mixed with the exhaust gas. The present invention relates to a gas mixing confirmation method in gas flow measurement using a gas trace method.
[0002]
[Prior art]
In exhaust gas flow measurement by the gas trace method using pure helium gas as a trace gas, a constant flow of helium gas is injected into exhaust gas, and a sufficiently mixed sample gas is sampled by various analyzers including a trace gas analyzer. There is a need. Specifically, as shown in FIG. 5, a mass flow controller 31 (for example, see Japanese Patent Application No. 9-227442) having both a function of measuring a gas flow rate and a function of controlling a gas flow rate is provided in a gas cylinder containing pure helium gas. Helium gas whose flow rate is controlled by using a mass flow controller 31 and is provided downstream of 30 is injected into an intake manifold (not shown) on the intake side of the engine 33 of the automobile 32 or a tail pipe (not shown) connected to the engine 33. Then, a sample gas S directly sampled from, for example, the sampling position A or the sampling position B of the exhaust pipe 34 downstream of the tail pipe is converted into a gas analyzer for measuring a component to be measured in the exhaust gas R and a helium gas for measuring the concentration of helium gas. was introduced into the spectrometer, Heriumuga known injection quantity Q _{the He} helium gas By dividing by the helium gas concentration C _He detected by the gas analyzer, the flow rate of the exhaust gas can be obtained in real time.
[0003]
In the case of pre-engine injection in which helium gas is injected from the suction side of the engine 33, the engine 33 functions as a stirrer for stirring the helium gas and the exhaust gas R, so that complete mixing of both gases can be achieved in the wake.
[0004]
[Problems to be solved by the invention]
By the way, exhaust gas flow measurement using the gas tracing method requires a wide dynamic range to observe changes during transient operation and a responsiveness that can respond to sudden acceleration / deceleration.However, helium gas is supplied to the tail pipe connected to the engine. In the case of injection after engine injection, there was no method for confirming the degree of mixing of both gases.
[0005]
Therefore, when the desired exhaust gas flow rate was not obtained by performing post-engine injection of helium gas, poor measurement accuracy of the exhaust gas flow rate was
(1) For example, as shown in FIG. 5, the volume of the pipeline from the helium gas injection position P to the sampling position B in the exhaust pipe 34 downstream of the tail pipe becomes a dead volume, and the helium gas concentration measurement result by the helium gas analyzer is used. Is the time lag with the helium gas concentration measurement error caused by the increase in the response delay increased, or
(2) The helium gas and the exhaust gas R were not always sufficiently mixed, and it was not possible to judge whether the mixing was due to an error generated in the helium gas concentration measurement result by the helium gas analyzer.
[0006]
For example, conventional problems will be described in more detail with reference to FIGS. FIG. 6A shows a virtual model of a change in the flow rate Q _DE (t) (where t is time) of the exhaust gas R by solid lines a ₁ , a ₂ , and a _3. flow rate Q _{DE (t)} starts at a low flow rate a _1, then it changes to a high flow rate a ₂ instantaneously, then shows the flow rate variation of returning to the low flow rate a ₃ instantaneously again. FIG. 6B shows the helium gas in the sample gas S flowing from the sampling position A as indicated by a virtual line, assuming that the helium gas is completely mixed with the exhaust gas R immediately after the post-engine injection. shows the change in the concentration _C He (t) of a solid line b. Therefore, in this ideal system, the sample gas S is sampled immediately after the injection of the helium gas, and the pipe volume from the injection position P to the sampling position A is small and there is no dead time. Changes. However, unlike such an ideal system, mixing of the helium gas and the exhaust gas R is not completely performed immediately after injection, and a finite distance is required until the helium gas is sufficiently mixed. . Therefore, conventionally, the sample gas S flowing as shown by the solid line from the sampling position B at the rear of the exhaust pipe 34, which is separated from the injection position P by a finite distance L, is sampled. Since there was no method, it was doubtful whether sampling position B was a position where helium gas and exhaust gas were sufficiently mixed. Moreover change c concentration _C the He helium gas when sampled at a sampling position B (t) [see FIG. 6 (C)] of the exhaust gas flow rate _Q DE (t) is switched from a low flow rate _{a 1} in a high flow rate _{a 2} The dead time T _d2 when the exhaust gas flow rate Q _DE (t) switches from the high flow rate a ₂ to the low flow rate a ₃ shows a larger value than the dead time T _{d1 at the} time, and as a result, the helium gas has a low concentration. The region becomes longer than the actual flow rate, and the exhaust gas flow rate Q _DE (t) is higher (longer time) than the actual high flow rate a ₂ (higher flow rate is shown by a virtual line a ₄ in FIG. 6A). ] Is observed, and an error occurs.
[0007]
Therefore, in the case of post-engine injection, in order to obtain a desired exhaust gas flow rate, the delay time due to the dead volume from the helium gas injection position P to the sampling position in the exhaust pipe downstream of the tail pipe is shortened to reduce the helium gas in the helium gas analyzer. Since it is necessary to minimize the time lag from the gas concentration measurement result, a method for confirming the degree of mixing of the exhaust gas R and the helium gas has been desired.
[0008]
The present invention has been made in consideration of the above-mentioned matters, and an object of the present invention is to provide a gas mixing confirmation method in gas flow measurement using a gas tracing method capable of confirming a mixing degree of exhaust gas and helium gas. .
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention relates to a method in which a sampling flow path for supplying a sample gas to a gas analyzer is connected to an exhaust flow path connected to an internal combustion engine, and a downstream of a sampling position in the sampling flow path. A trace gas analyzer for measuring the concentration of the trace gas is provided on the side, and the trace gas is supplied from one of the first injection position on the upstream side of the internal combustion engine and the second injection position on the exhaust flow path on the upstream side of the sampling position. Injecting, measuring the flow rate of the exhaust gas of the internal combustion engine based on the trace gas injection amount and the trace gas concentration, setting the sampling position to be movable, and setting the flow rate of the exhaust gas corresponding to each position to the second injection. Trace gas is injected from the position and measured for each constant speed traveling mode, and the flow rate of these exhaust gases is predicted by injecting the trace gas from the first injection position. At the sampling positions when matched in flow rate and the constant speed driving mode of the measured exhaust gas, it is characterized in that so as to verify that substantial mixing of the trace gas and the exhaust gas was obtained.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0011]
1 and 2, reference numeral 1 denotes an automobile, which is subjected to a running simulation test performed using a chassis dynamo 16 based on a predetermined running mode switching sequence. Reference numeral 2 denotes an engine of the automobile 1. Reference numeral 3 denotes an exhaust pipe connected to a tail pipe (not shown) connected to the engine 2. Reference numeral 4 denotes a sampling pipe connected to the exhaust pipe 3. The exhaust pipe 3 directly samples a sample gas S obtained by injecting a helium gas as a trace gas into the exhaust gas R from the exhaust pipe 3. A probe pipe 5 for changing, for example, seven sampling positions A ₀ , A ₁ , A ₂ , A ₃ , A ₄ , A ₅ , A ₆ in the exhaust pipe 3 is flexible at the tip 4 a of the sampling pipe 4. It is provided via a pipe 5c. The probe tube 5 is inserted directly into the exhaust pipe 3, the tube-axis direction (M ₁ direction, M ₂ direction) by the drive means 40 is movable in the.
[0012]
The driving means 40 includes a belt 40c hung over a pair of pulleys 40a and 40b, a moving member 40d mounted and fixed on the upper surface of the belt so as to move in the tube axis direction together with the belt 40c, and a belt drive not shown. It consists of a motor. The probe tube 5 is fixed to the moving member 40d with the rear end portion 5b of the probe tube 5 penetrating the moving member 40d in the tube axis direction, and the rear end portion 5b connects the joint 41. The flexible pipe 5c is connected to one end of the flexible pipe 5c via the joint 42, while the other end of the flexible pipe 5c is connected to the tip 4a of the sampling pipe 4 via the joint 42.
[0013]
6a is a trace gas supply path for pre-engine injection connected to an intake manifold (not shown) on the intake side of the engine 33, and 6b is a trace gas supply path for injecting helium gas into the tail pipe. is there. A gas cylinder 8 containing pure helium gas as a trace gas is provided on the upstream side of the trace gas supply paths 6a and 6b via an electromagnetic three-way valve 7, and a function for measuring the flow rate of the helium gas is provided on the downstream side. And a mass flow controller 9 having a function of controlling the mass flow controller. The reason why helium gas was used as the trace gas is that the atomic weight of helium is far different from the atomic weight of the substances present in the exhaust gas as compared with other inert gases such as argon.
[0014]
The following devices and devices are connected to the sampling tube 4, for example. That is, a helium gas analyzer (trace gas analyzer) 10 for measuring the concentration of helium gas and a plurality of gas analyzers 11 for measuring components to be measured in the exhaust gas are provided in parallel with each other. The gas analyzer 11 is provided via a branch channel 12 branched from example _CO, CO 2, HC, sampling tube 4 so as to be able to appropriately measure the components contained in such flue gas NO _x. Reference numeral 13 denotes a suction pump, 14 denotes a filter, and 15 denotes a dehumidifier such as an electronic cooler.
[0015]
Then, when performing pre-engine injection of injecting helium gas whose flow rate is controlled by the mass flow controller 9 from the intake side of the engine 2 (injection position is indicated by V and is assumed to be a first injection position), after the combustion chamber, When helium gas is injected into the tail pipe while sampling can be performed from any position, the sampling positions A ₀ , A ₁ , A ₂ , A at an appropriate distance from the injection position (second injection position) P. ₃ , A ₄ , A ₅ , and A ₆ can be sampled.
[0016]
Then, the chassis dynamo 16, the trace gas analyzer 10, the plurality of gas analyzers 11, the mass flow controller 9 and the electromagnetic three-way valve 7 are connected to a system controller (CPU) 18 including arithmetic means via an input / output interface 17, By dividing the known injection amount _QHe of helium gas by the concentration _CHe of helium gas detected by the helium gas analyzer 10 according to a previously set and stored calculation program, the flow rate Q of exhaust gas according to the traveling pattern is obtained. _DE can be obtained in real time. Further, by moving the probe tube 5 provided at the distal end portion 4a of the sampling tube 4 in the tube axis direction, the sampling port 5a of the probe tube 5 is moved to the sampling positions A ₀ , A ₁ , A ₂ , A ₃ , It can be brought to any of A ₄ , A ₅ , and A ₆ . Further, the discharged weight of the component gas to be measured can be obtained in real time.
[0017]
In order to confirm that the trace gas (helium gas) at a constant flow rate injected from the tail pipe is sufficiently mixed with the exhaust gas R in the exhaust pipe 3, the respective sampling positions A ₀ , A ₁ , A _{At 2} , A ₃ , A ₄ , A ₅ , and A ₆ , first, data in the case of injection before the engine is collected.
[0018]
In this case, the chassis dynamo 16 employs a constant speed traveling mode such as 80 (km / h) or 40 (km / h) as the predetermined traveling mode. Figure 3 shows a 80 (km / h) data X and 40 of the flow rate _{Q DE} of the exhaust gas due to constant speed running (km / h) data Y of the flow rate _{Q DE} of the exhaust gas due to constant speed running. In the data X and Y, the reason why the exhaust gas flow rate _QDE does not fluctuate is that the helium gas can be injected from the arbitrary position after the combustion chamber as the first injection position V in the pre-engine injection, and the engine 2 mixes the helium gas and the exhaust gas R. This is because both gases can be completely mixed in the downstream stream because they function as a stirrer for stirring.
[0019]
Next, data in the case of tailpipe injection is collected using the constant speed traveling mode. Figure 3 shows a 80 (km / h) data W of the flow rate _{Q DE} of the exhaust gas due to constant speed running and 40 (km / h) data Z of the flow rate _{Q DE} of the exhaust gas due to the constant-speed running when the tail pipe injection.
[0020]
For example, from the data W, it can be easily confirmed that the helium gas and the exhaust gas R are sufficiently mixed at a position 100 cm away from the second injection position P by comparing with the data X in the case of the injection before the engine. That, 80 (km / h) when the constant speed running, the flow rate _{Q DE} of the exhaust gas at a distance 100cm from tail pipe injection position P in the M direction, by injecting helium gas from the first injection position V measurement since it matches the flow rate Q _DE of by exhaust gas, it becomes clear to complete at a position where the mixing of both gases leaves 100 cm. Therefore, the helium gas and the exhaust gas R are sufficiently moved by moving the probe tube 5 so that the sampling port 5a of the probe tube 5 is located at a position 100 cm away from the second injection position P based on the data X and W. The analysis can be performed using the mixed sample gas S. Therefore, the delay time due to the dead volume from the second injection position P of the helium gas to the sampling position can be shortened, the time lag with the helium gas concentration measurement result in the helium gas analyzer 10 can be minimized, and a desired exhaust gas flow rate can be obtained. Can be.
[0021]
In this case, it is sufficient to bring the sampling port 5a of the probe tube 5 at any one of the sampling positions A ₀ , A ₁ , A ₂ , A ₃ , A ₄ , A ₅ , A _6. The length of the probe tube 5 may be set as appropriate, and the intervals between the sampling positions A ₀ , A ₁ , A ₂ , A ₃ , A ₄ , A ₅ , and A ₆ may be set as appropriate.
[0022]
Further, 40 (km / h) the same when the constant speed running, the flow rate Q _DE of the exhaust gas at a distance 80cm from the tail pipe injection position P in the M direction, injecting helium gas from the first injection position V Since the measured gas flow rate coincides with the measured exhaust gas flow rate _QDE , it is clear that the mixing of the two gases is completed at a position separated by 80 cm.
[0023]
FIG. 4 shows, as means for setting the sampling position movably, for example, seven branch pipes 44 to 50 branched from the tip end 4a of the sampling pipe 4 at the sampling positions A ₀ , A ₁ , A ₂ , A ₃ , shows another embodiment of _{a 4,} a 5, is provided via a two-way electromagnetic valve 44a~50a to correspond to _{a 6} the present invention.
[0024]
In this case, since sampling can be performed at a plurality of sampling positions A ₀ , A ₁ , A ₂ , A ₃ , A ₄ , A ₅ , and A ₆ , the second injection position P based on, for example, data X and W shown in FIG. For example, the two-way solenoid valve 47a of the branch pipe 47 provided at a position 100 cm away from the valve is opened, and the two-way solenoid valves 44a, 45a, 46a, 48a, 49a, 50a other than the two-way solenoid valve 47a are closed. By setting to, the sample gas S in which the helium gas and the exhaust gas R are sufficiently mixed can be used for analysis.
[0025]
In the present invention, when the sample gas S is sampled at a constant flow rate, a critical flow rate orifice may be used.
[0026]
【The invention's effect】
As described above, in the present invention, the flow rate of the exhaust gas measured in advance by injecting the trace gas from the first injection position on the upstream side of the internal combustion engine and the second injection position of the exhaust flow path on the upstream side from the sampling position are determined. When the flow rate of the exhaust gas measured by injecting the trace gas coincides with the helium gas at the sampling position separated by a predetermined distance from the second injection position in the same constant speed mode, substantial mixing of the trace gas and the exhaust gas is performed. Can be confirmed, the delay time due to the dead volume from the second injection position of the helium gas to the sampling position can be shortened, and the time lag with the helium gas concentration measurement result in the helium gas detector can be reduced as much as possible. Exhaust gas flow rate can be obtained.
[Brief description of the drawings]
FIG. 1 is an overall configuration explanatory diagram showing a state of exhaust gas flow rate measurement using an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a main part configuration in the embodiment.
FIG. 3 is a characteristic diagram showing exhaust gas flow rate data in the case of front engine injection and tail pipe injection at constant speed running in the embodiment.
FIG. 4 is an explanatory diagram of a main part configuration in another embodiment of the present invention.
FIG. 5 is a diagram for explaining a conventional problem.
FIG. 6 is a view for explaining a mechanism of an error when measuring an exhaust gas flow rate in a transient operation state.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Car, 2 ... Engine, 3 ... Exhaust pipe, 4 ... Sampling pipe, 5 ... Probe pipe, 5a ... Sample sampling port, 6a, 6b ... Trace gas supply path, 7 ... Electromagnetic three-way valve, 9 ... Mass flow controller, 10 ... trace gas analyzer, 11 ... gas analyzer, 16 ... chassis dynamometer, 18 ... system controller, R ... exhaust, S ... sample gas, V ... first injection position, P ... second injection _position, A 0, _{A 1} , A ₂ , A ₃ , A ₄ , A ₅ , A ₆ ... Sampling positions.

Claims (1)

Trace gas for connecting a sampling flow path for supplying a sample gas to a gas analyzer to an exhaust flow path connected to the internal combustion engine, and measuring a concentration of the trace gas downstream of a sampling position in the sampling flow path An analyzer is provided, and a trace gas is injected from one of a first injection position on the upstream side of the internal combustion engine and a second injection position on the exhaust flow path on the upstream side of the sampling position. And the sampling position is set to be movable, and the exhaust gas flow according to each position is injected at a constant speed by injecting trace gas from the second injection position. The flow rate of the exhaust gas was measured for each mode, and the flow rate of the exhaust gas was the same as the flow rate of the exhaust gas previously measured by injecting the trace gas from the first injection position. A gas mixing check in the gas flow measurement using the gas tracing method, wherein it is confirmed that a substantial mixing of the trace gas and the exhaust gas has been obtained at the sampling position when the modes match. Method.

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