JPH0651856U - Gas mixing device for gas sampling device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide an axial flow type gas mixing device in which overheating of a pipe is prevented in a portion where an axial flow type gas mixing device is mounted, and as a result, heating of the pipe can be uniformly performed. [Structure] In an axial flow type gas mixing device 2 installed in a pipe P of a gas sampling device 1, a large number of holes 22 are provided in a casing 21 of the gas mixing device 2. In the preferred embodiment, the multiple holes 22 are distributed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a gas mixing device for a gas sampling device.

[0002]

[Prior art]

 In order to prevent air pollution, emission of pollutants such as nitrogen oxides, hydrocarbons, carbon monoxide, etc. in automobile exhaust gas is regulated. Therefore, as shown in FIG. 2, gas sampling is performed by the gas sampling device 1 and gas analysis is performed by the gas analyzer (not shown) to check whether the exhaust gas of the automobile V satisfies the regulation value. Has been done.

Gas sampling in the gas sampling apparatus 1 is performed as follows.

Exhaust gas from the automobile V is introduced into the mixing pipe C through the sample introduction pipe L.

The exhaust gas introduced into the mixing pipe C is diluted with the dilution air.

The diluted exhaust gas is exhausted through the pipe P by the centrifugal blower B. At this time, sampling is performed by a sambling pipe S provided in the middle of the pipe P.

A critical flow venturi N is interposed in front of the centrifugal blower B in the pipe P in order to keep the gas flow rate in the pipe P constant.

An axial flow type gas mixing device 2 as shown in FIG. 3 is installed in the middle of the pipe P for stirring the diluted exhaust gas.

By the way, as is well known, since gasoline, which is a fuel for automobiles V, contains hydrocarbons as a main component, steam exists in exhaust gas. If the pipe P is not treated at all, the water vapor will be condensed on the inner surface of the pipe when, for example, the gas sampling apparatus 1 is stopped and the inner surface temperature of the pipe is lowered to a dew point or lower.

If the condensed water is left in the tube, contaminants such as nitrogen oxides and carbon monoxide in the exhaust gas will be absorbed when the gas sampling apparatus 1 is restarted. As a result, the amount of pollutants in the sampled exhaust gas will be lower than it should be.

On the contrary, when a sufficient time has passed since the gas sampling device 1 was activated, the water condensed on the inner surface of the pipe was evaporated, and the nitrogen oxide dissolved in the water was also exhausted. Released into the space. As a result, the amount of pollutants in the sampled exhaust gas will be higher than it should be.

[0012] Therefore, the measured values at the start of measurement and at the steady state vary.

This tendency is more remarkable in the present situation where the fuel of the automobile V is diversified and alcohol fuel is used. This is because, for example, when methanol is used as the alcohol fuel, the water vapor partial pressure is almost twice as high as that of gasoline.

Therefore, the outside of the pipe P is kept warm (not shown), the heater H is wound around the pipe P to heat the pipe P, and moisture is prevented from adhering to the inner wall of the pipe P. (See Figure 3).

By the way, this heating needs to be performed uniformly in order to accurately perform gas sampling. However, in the portion where the axial flow type gas mixing device 2 is mounted, a hot spot occurs due to the poor flow of gas in the gap between the casing 21 of the gas mixing device 2 and the inner surface of the pipe P. Therefore, there is a problem that the heating of the pipe P is not uniform.

[0016]

[Problems to be solved by the device]

 The present invention has been made in view of the above problems of the prior art, and prevents overheating of the pipe in the portion where the axial flow gas mixing device is installed, and as a result, the heating of the pipe can be made uniform. An object is to provide an axial flow type gas mixing device.

[0017]

[Means for Solving the Problems]

 The present invention relates to an axial flow type gas mixing device installed in a pipe of a gas sampling device, wherein the casing of the gas mixing device is provided with a large number of holes.

In the present invention, it is preferable that the plurality of holes are provided in a dispersed manner.

[0019]

[Action]

 In the axial flow type gas mixing device of the present invention, since the casing is provided with a large number of holes, the gas for which the radial partial velocity is obtained by the propeller-like stirring plate of the gas mixing device is provided in the casing. It collides with the inner surface of the pipe through the hole and cools that part. Therefore, overheating of the portion where the gas mixing device is installed is prevented, and the piping is heated uniformly. Further, in a preferred embodiment in which a large number of holes are provided in a dispersed manner, uniform heating of the pipe is promoted.

[0020]

【Example】

 Hereinafter, the present invention will be described based on embodiments with reference to the accompanying drawings, but the present invention is not limited to such embodiments.

FIG. 1 is an explanatory diagram showing a state in which an axial flow type gas mixing apparatus according to an embodiment of the present invention is attached to a pipe. In FIG. 1, 22 is a hole provided in the casing 21, and 23 is a propeller-shaped stirring plate. The same reference numerals as those in FIGS. 2 and 3 denote the same or similar elements.

In the axial flow type gas mixing apparatus 2 of the present invention, as is apparent from FIG. 1, a casing 21 is provided with a large number of holes 22. There is no particular limitation on the shape and size of the hole 22, and various shapes and sizes are appropriately selected. Also, the area ratio of the holes 22 provided is appropriately selected in consideration of cooling efficiency and the like. Moreover, the arrangement of the holes 22 in the casing 21 is not particularly limited, but it is preferable that the holes 22 are provided in a dispersed manner.

The basic structure of the axial flow type gas mixing device 2, that is, the structure of the casing 21 and the propeller-shaped stirring plate 23 is the same as the conventional one, and therefore the detailed description of the structure is omitted.

Next, the operation in the pipe P of the axial flow type gas mixing device 2 configured as described above will be described.

The diluted exhaust gas (hereinafter simply referred to as “diluting gas”) introduced into the axial-flow gas mixing device 2 is stirred by a propeller-shaped stirring plate 23. At this time, since the diluent gas is also given a partial speed in the radial direction by the propeller-like stirring plate 23, a part of the diluent gas advances toward the casing 21. However, since the casing 21 is provided with the large number of holes 22 as described above, most of the dilution gas that has proceeded toward the casing 21 reaches the inner wall of the pipe P.

The gas reaching the inner wall of the pipe P is reflected by the inner wall of the pipe P, and most of the gas passes through the hole 22 and reenters the casing 21. Then, on the contrary, it collides with the diluent gas advancing toward the casing 21. Therefore, the stirring of the gas is promoted.

As described above, according to the axial flow type gas mixing apparatus 2 of the present invention, the diluent gas also flows in the gap between the casing 21 and the pipe P, so that the pipe P in this portion is cooled, and in this portion. A local temperature rise is prevented. As a result, the pipe P is heated uniformly.

[0028]

[Effect of device]

 As described above, according to the present invention, it is possible to prevent a local temperature rise in the pipe where the axial flow type gas mixing device is installed, the pipe is heated uniformly, and the gas is agitated. The effect of being promoted is obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a state in which an embodiment of an axial flow type gas mixing device of the present invention is attached to a pipe.

FIG. 2 is a schematic view of a sample gas sampling device.

FIG. 3 is an explanatory view showing a state where a conventional axial flow type gas mixing device is attached to a pipe.

[Explanation of symbols] 1 gas sampling device 2 axial flow type gas mixing device 21 casing 22 holes 23 propeller-like stirring plate P piping C mixing pipe N critical flow venturi B centrifugal blower V automobile S sampling pipe H heater L sample introduction tube

Claims (2)

[Scope of utility model registration request] 1. An axial-flow gas mixing device installed in a pipe of a gas sampling device, wherein a casing of the gas mixing device is provided with a large number of holes. 2. The gas mixing device according to claim 1, wherein the plurality of holes are provided in a dispersed manner.