JPH0422459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the absolute values of the volume concentration and weight concentration of carbon fine particles in a smoke stream discharged from a heat engine.

[Prior Art] Conventionally, there are roughly two types of methods for measuring the concentration of smoke emitted from a heat engine or the like. For example, one of the two methods mentioned above for diesel engines is the Bosch type smoke meter method. In this method, fine carbon particles in exhaled smoke are attracted onto a filter paper, and the concentration of exhaled smoke is measured by measuring the reflectance of light on the filter paper. Another method is the method specified in the American test method, in which smoke is left in a free jet state, and white light is applied to the smoke from the side to measure the opacity of the light. This method measures the concentration of smoke by measuring it.

However, the above-mentioned methods for measuring each type are based on so-called individual arbitrary scales, and can only be achieved by measuring according to predetermined rules for measurement. Therefore,
The meanings of the measurement values obtained by the various measurement methods described above are different, and it is currently difficult to determine the absolute relationship between the measurement methods. That is, with the various methods described above, it is not possible to obtain the absolute concentration of carbon particles in the smoke stream of a heat engine.

[Problems to be Solved by the Invention] An object of the present invention is to provide a simple method for measuring the absolute values of the volume concentration and weight concentration of carbon fine particles in a smoke stream from a heat engine. .

[Means for Solving the Problems] In order to achieve the above object, the measuring method of the present invention allows the smoke stream discharged from the heat engine to flow out in a free jet state, and the carbon particles in the smoke stream are On the other hand, a relatively long single wavelength light that causes Rayleigh scattering is irradiated in multiple directions across the smoke stream, and the intensity of the light transmitted through the smoke stream is detected by a receiver,
This method is characterized in that the absolute values of the volume concentration and weight concentration of carbon particles in the smoke stream are measured by calculating a tomographic image from the detection signal of the light receiver.

In the measurement method of the present invention, the single wavelength light irradiated to the smoke stream has a relatively long wavelength that causes Rayleigh scattering to the carbon particles in the smoke stream. It is theoretically clear that the absorption and scattering of single wavelength light by fine particles can be obtained with the light transmittance depending on the volume concentration of carbon fine particles, and the single wavelength light can be passed across the smoke stream. Since the irradiation was made from multiple directions, changes in the intensity of the light that passed through the smoke stream were detected, and from those detected values, a computer was used to obtain a tomographic image of the jet that overlapped across the entire plane. The absolute values of the volume concentration and weight concentration of the carbon fine particles inside are determined.

Below, the method of the present invention will be explained in more detail.

Figure 1 shows an example of the apparatus used to carry out the method of the present invention, in which 1 is a smoke stream discharged from a heat engine, which is discharged into the atmosphere in a free jet state of about 5 cm in diameter, and downstream. is the duct 2 that receives the smoke flow 1
is provided.

The smoke stream 1 is irradiated with single-wavelength light in multiple directions across the smoke stream, and a tomographic image is calculated from the intensity of the transmitted light. On the same axis as the axis L of smoke flow 1,
For example, a He-Ne gas laser is arranged as the light source 3. The laser light emitted from the light source 3 is treated as Rayleigh scattering in which the absorption and scattering of the laser light by the carbon particles is obtained by assuming that the light transmittance depends on the volume concentration or weight concentration of the carbon particles. This is what I did.

In front of the laser light source 3 is a half mirror 4.
An inclined rotating mirror 5 that reflects the laser beam through the
will be provided. The rotating mirror 5 has the axis L
It is obliquely fixed to the rotation shaft 7 of the motor 6 located coaxially with the motor 6, and rotates together with the rotation shaft 7.
It is configured such that the direction of reflection of the laser beam reflected by the rotating mirror 5 is rotated around the axis L mentioned above.

Furthermore, as shown in FIGS. 1 and 2, in order to direct the reflected light from the rotating mirror 5 in a direction across the smoke stream 1, a flat mirror 8 is arranged around the rotating mirror 5, and a fixed A plane mirror 9 is arranged around a measurement area in the discharge stream 1, and a fixed concave mirror 10 is provided on the opposite side of the fixed plane mirror 9 across the smoke stream 1. As can be seen from FIG. 2, the fixed plane mirrors 8 and 9 and the fixed concave mirror 10 allow the light reflected by them to scan across the entire cross section of the smoke stream 1, and to pass through the same optical path. The beam is arranged so that it passes through the beam and enters the rotating mirror 5 again. Therefore,
The center of curvature O ₂ of the concave mirror 10 is the point where the distance from the rotating mirror 5 to the plane mirror 9 is extended in the opposite direction from the mirror 8 to the concave mirror 10 in FIG.

As a result, the laser beam reflected by the rotating mirror 5 is reflected by the plane mirrors 8 and 9, passes through the smoke stream 1, and enters the concave mirror 10, and then,
The laser beam passes through the previous optical path in the reverse direction and enters the rotating mirror 5 again, and therefore passes through the smoke flow 1 twice in a round trip, and is reflected and scattered in a Rayleigh scattering state during each pass.

In addition, the plane mirrors 8 and 9 and the concave mirror 10
As can be seen from FIG. 2, a plurality of sets are arranged around the measurement area in the smoke flow 1.

The laser beam that has returned to the rotating mirror 5 after reciprocating through the plane mirrors 8, 9 and the concave mirror 10 is reflected again by the rotating mirror 5 and enters the half mirror 4, and the laser beam reflected there is determined by its intensity. The light is projected onto a light receiver 11 for detecting changes. Thereby, the reflected light from the plane mirror 9 and the concave mirror 10 at the rotational position of the rotating mirror 5 is sequentially projected onto the light receiver 11.

Connected to the light receiver 11 are an electronic computer 12 for processing the detection signal obtained there, and a recording display 13 for recording and displaying the processing results. The electronic computer 12 calculates a tomographic image from the detection signal of the light receiver 11.

In order to measure the volume concentration of carbon fine particles in the smoke stream 1 with the device configured as described above, as can be seen from the above, the laser beam is applied to the smoke stream 1 in a free jet state while rotating the rotary mirror 5. Each time it is projected onto each plane mirror 9 via the plane mirror 8, the plane mirror 9 and the opposing fixed concave mirror 10 work together to spread the entire cross section of the smoke stream 1. The transmitted light is received by the light receiver 11 and changes in intensity are detected. This is repeated each time the plane mirrors 8 and 9 on which the laser beam enters change as the rotary mirror 5 rotates, and by repeating this, the smoke stream 1 is irradiated with the laser beam from the radial direction, and for each irradiation method. The change in intensity of the laser beam will be detected.
Therefore, a tomographic image is calculated by an electronic computer from these detected values, and the absolute values of the volume concentration and weight concentration of the carbon particulates in the smoke stream are obtained, and these are recorded and displayed on the recording display.

Furthermore, apparatuses such as those shown in FIGS. 3 and 4 can also be used to carry out the present invention.

This device has a concave mirror 10 placed in the device shown in FIGS.
0, a large number of glass fibers 15 are arranged in an array, and the other end of each of these glass fibers 15 is connected to a single, not shown, light receiver. Furthermore, the light receiver is connected to an electronic computer and a recording display, and
The tomographic image is calculated in almost the same way as the device shown in the figure.
The volume concentration and weight concentration of carbon particles in the smoke stream are measured.

That is, in the above device, the laser light does not reciprocate within the smoke stream 1 and passes through it only once, but the transmitted light passes through the glass fiber 15.
The received light intensity of each glass fiber changes sequentially in the light receiver, thereby making it possible to know which glass fiber's light-receiving end is detecting the transmitted light. By comparing the measured value by the photodetector with the calibration value when there is no smoke flow in the measurement area, the degree of light attenuation due to the smoke flow can be detected, and the tomographic image can be determined based on the measurement results. At the same time, the volume concentration and weight concentration of carbon particles in the smoke stream can be measured.

Other configurations and functions are shown in Figures 1 and 2.
Since it is the same as in the figure, the same or corresponding parts are given the same reference numerals and the explanation thereof will be omitted.

Furthermore, the method of the present invention is not limited to the above-mentioned two examples of devices, but can also include a plurality of sets of laser light sources and light receivers arranged around the smoke flow 1, and a plurality of laser lights from these laser light sources. It is also possible to construct a structure in which the smoke stream is irradiated at the same time, and each laser beam that has passed through the smoke stream is received by a light receiver, thereby enabling the measurement of the volume concentration and weight concentration of the carbon particles with a high-speed response. It can be done sexually.

[Brief explanation of drawings]

FIG. 1 is a schematic front view showing the overall configuration of the device used to carry out the present invention, FIG. 2 is a schematic explanatory view of the A-A cross section, and FIG. 3 is a schematic diagram showing another example of the configuration of the above device. The front view of FIG. 4 is a schematic explanatory view at the same position as FIG. 2. 1...Smoke flow, 11...Light receiver.

Claims (1)

[Claims] 1 The smoke stream discharged from the heat engine is made to flow out in a free jet state, and a relatively long single wavelength light that causes Rayleigh scattering is transmitted to the carbon particles in the smoke stream.
irradiating in multiple directions across the smoke stream and detecting the intensity of the light transmitted through the smoke stream with a receiver;
A method for measuring smoke concentration in a heat engine, characterized in that the absolute values of the volume concentration and weight concentration of carbon particles in the smoke flow are measured by calculating a tomographic image from the detection signal of the light receiver.