JPS61207949A - Measuring method for discharged smoke density from heat engine - Google Patents

Abstract

PURPOSE:To measure the absolute value of a volume density and a weight density by irradiating a single wavelength light to carbon fine particles in a discharged smoke flow. CONSTITUTION:A gaseous He-Ne laser is placed as a light source 3 on the same axis as the axis L of a smoke discharge machine 1, in front of which an inclined rotary mirror 5 for reflecting a laser beam through a half mirror 4 is provided. The rotary mirror 5 rotates a reflecting direction of the laser beam around the axis L. In order to turn a reflected light from the rotary mirror 5 to the direction for crossing a discharged smoke flow 1, a fixed plane mirror 9 is placed around a measuring area, and a fixed concave mirror 10 is provided on the opposite side. The laser beam reflected by the rotary mirror 5 is made incident on plane mirrors 8, 9, the discharged smoke flow 1, and the concave mirror 10, and thereafter, passes through an optical path in reverse and made incident on the rotary mirror again, and the laser beam passed through the discharged smoke flow 1 two times in its reciprocating motion, reflected and scattered at each passing time, and projected to a photodetector 11. By the arithmetic of an electronic computer 12 from a detected value, the absolute values of the volume density and the weight density of carbon fine particles in the discharged smoke flow are obtained, and displayed on a recording indicator 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] 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 l] Conventionally, there are two types of methods for measuring the concentration of smoke emitted from heat engines, etc.For example, one of the above two methods for diesel engines is the Bosch This method uses a type smoke meter. 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, white light is applied to the smoke from the side, and the opacity of the light is measured. This method measures the concentration of smoke by measuring the amount of smoke.

However, the above-mentioned various measurement methods are based on so-called individual arbitrary scales, and are effective only when measurements are performed in accordance with predetermined rules for measurement. Therefore, the meanings of the measured 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, the absolute concentration of carbon particles in the smoke stream of a heat engine cannot be determined by the various methods described above.

[Problems to be Solved by the Invention J] 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 1] In order to achieve the above object, the measurement method of the present invention allows the smoke stream discharged from a heat engine to flow out in a free jet state, and carbon particles in this smoke stream are On the other hand, 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 light receiver. The 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.

In such a measurement method of the present invention, the medium-wavelength light irradiated to the smoke stream has a relatively long wavelength that causes Rayleigh scattering to the carbon particles in the smoke stream. Absorption of single wavelength light by carbon particles,
It is theoretically clear that scattering can be obtained by changing the light transmittance to the volume concentration of the carbon particles, and the medium-wavelength light is irradiated from multiple directions across the smoke flow. Therefore, changes in the intensity of light transmitted through the smoke stream are detected, and a tomographic image covering the entire cross section of the jet is obtained using a computer from these detected values, and the volume concentration and weight concentration of carbon particles in the smoke stream are calculated. Absolute value is required.

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. 1 is a smoke stream discharged from a heat engine, which is discharged into the atmosphere in a free jet state with a diameter of about 5 cm, and is discharged downstream. A duct 2 is provided for receiving the smoke flow l.

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. For example, a He-Me gas laser is arranged as a light source 3 coaxially with the axis of the smoke flow 1. The laser beam emitted from the light source 3 is configured such that absorption and scattering of the laser beam by the carbon particles can be treated as Rayleigh scattering in which the light transmittance is obtained as a function of the volume concentration or weight concentration of the carbon particles. It is something.

In front of the laser light source 3, an inclined rotary mirror 5 is provided which reflects the laser light via a half mirror 4.

The rotating mirror 5 is obliquely fixed to a rotating shaft 7 of a motor 6 located coaxially with the axis, and rotates together with the rotating shaft 7 to reflect the laser beam reflected by the rotating mirror 5. is configured to rotate around the above-mentioned axis.

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 flow l, a flat mirror 8 is arranged around the rotating mirror 5, and a fixed A plane mirror 8 is arranged around a measurement area in the discharge flow 1, and a fixed concave mirror 10 is provided on the opposite side of the fixed plane mirror 9 across the discharge flow 1. The fixed plane mirror 8.9 and the fixed concave mirror 10, as shown in FIG.
The beam is arranged so as to scan the entire cross section of the beam and enter the rotating mirror 5 again through the same optical path. Therefore, the center of curvature of the concave mirror 10 is 0. is the point where the distance from the rotating mirror 5 to the plane mirror 8 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
After being reflected by the plane mirror 8.9, the laser beam passes through the smoke flow 1 and enters the concave mirror 10, and then passes through the previous optical path in the reverse direction and enters the rotating mirror 5 again. The light passes through the stream 1 twice in a round trip, and upon each pass, reflection and scattering occur in a Rayleigh scattering state.

Further, the plane mirror 8.8 and the concave mirror 10 are connected to a second
As can be seen from the figure, a plurality of sets are arranged around the measurement area in the smoke flow l.

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. Light receiver 11 for detecting changes
is projected on. As a result, the reflected light from the plane mirror 8 and the concave mirror 10 at the rotational position of the rotating mirror 5 is
The light is sequentially projected onto the light receiver 11.

The light receiver 11 includes an electronic calculation R12 for processing the detection signal obtained there, and a recording display for recording and displaying the processing results! 3 is connected.

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 particles in the smoke stream 1 with the device configured as described above, as can be seen from the above, the rotating mirror 5 must be rotated with respect to the smoke stream 1 in a free jet state. Each time a laser beam is projected and enters each plane mirror 8 via a 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 mirror 8.9 on which the laser beam is incident changes as the rotary mirror 5 rotates.

By repeating this process, the smoke flow 1 is irradiated with laser light from the radial direction, and the intensity change of the laser light in each irradiation direction is 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 carbon particles in the smoke stream are obtained.
This is recorded and displayed on the record display.

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

In this device, in place of the concave mirror 10 in the device shown in FIGS. 1 and 2, a large number of light receiving ends 16 of glass fibers 15 are arranged and arranged. The other end of the glass fiber 15 is connected to a single light receiver (not shown). Furthermore, the light receiver is connected to an electronic computer and a recording display, and a tomographic image is calculated in substantially the same manner as the apparatus shown in FIGS. 1 and 2.
The volume concentration and weight concentration of carbon particles in the smoke stream are measured.

That is, in the above device, the laser beam does not go back and forth within the smoke flow 1 and passes through it only once, but the transmitted light is received by the light receiver through the glass fiber 15, and the light is transmitted through the light receiver through the glass fiber 15. The received light intensity of each glass fiber fluctuates sequentially, which makes it possible to know which glass fiber's receiving end is detecting transmitted light. The degree of light attenuation due to the smoke flow can be detected by comparing with the calibration value when there is no smoke flow, and the tomographic image can be calculated based on the measurement results. The volumetric and gravimetric concentrations of can be measured.

Note that the other configurations and operations are the same as those in FIG. 1 and FIG. 2, so the same or corresponding parts will be given the same reference numerals and their explanation 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 with gender.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view showing the overall configuration of the device used for carrying out the present invention, FIG. 2 is a schematic explanatory view of the A-A cross section thereof,
FIG. 3 is a schematic front view showing another configuration example of the above device, and FIG. 4 is a schematic explanatory view at the same position as FIG. 2. 1st diagram 2nd diagram O

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 at multiple points across the smoke stream. The intensity of the light transmitted through the smoke stream is detected by a light receiver, and the volume concentration and weight of the carbon particles in the smoke stream are calculated by calculating a tomographic image from the detection signal of the light receiver. A method for measuring smoke concentration from a heat engine, characterized by measuring the absolute value of concentration.