JPH0355779B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to the production of spray particles from an injection valve that supplies liquid fuel to the combustion chamber of a gas turbine, diesel engine, boiler, etc., or in the process of producing powder by a spray drying method. The present invention relates to a device for measuring the representative particle size of solid particles.

[Prior art] Conventionally, in this type of device, there is a device that photographs the sprayed particles with a television camera, performs image processing, and measures the representative particle size, and a device that measures the representative particle size based on the characteristics of the scattered light from each particle. There are devices that determine the particle size and measure the representative particle size, but all of these require statistical sampling using image processing, and it takes time to obtain statistically sufficient samples, and it is difficult to use, for example, in a diesel engine. It is impossible to measure sprays that end in an extremely short period of time, such as sprays from commercial fuel injection valves, or sprays that involve transient changes. Furthermore, there is a device that uses optical diffraction development of a group of particles rather than individual particles to measure the representative particle size. In addition, it is necessary to find the one closest to the measurement pattern from among these diffraction pattern files and match the pattern, which requires a lot of time and requires a lot of time to perform the work and analysis. However, there are problems in that it is complicated, large-sized, and expensive.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problem in the conventional example that it takes a lot of time to measure the particle size, and also solves the problem that it is impossible to measure spray particles that involve transient changes. This is an attempt to solve the problems of complicated and large-sized devices.

[Means for Solving the Problems] As a specific means for solving the above problems, the present invention provides a laser oscillator, an optical lens for condensing light scattered forward from a group of spray particles irradiated with a laser beam, and the like. , two concentric photoelectric elements disposed at the focal point of the optical lens, and a logarithmic amplifier that amplifies the current signals from the photoelectric elements, respectively;
A subtracter that outputs the output difference from each of the amplifiers, and an A/D converter that converts the output from A/D.
The present invention provides a particle size measuring device for atomized particles, which includes a calculation unit that calculates a particle size from an A/D converted output, and a display device that digitally displays the calculation result, and the device is configured to measure a particle size of atomized particles by directing a laser beam to a group of atomized particles. The light scattered by the spray particles is collected, the photoelectric element receives the light, extracts a current signal, and instantaneously calculates and digitally displays the current signal based on the current signal. This will significantly shorten the time required, and the device itself will also be made smaller and lighter.

[Embodiments] Next, the present invention will be explained in more detail based on the illustrated embodiments. 1 is a laser oscillator, and a laser beam emitted from the laser oscillator is collimated by a collimator lens 2 to form a parallel laser beam 3. The spray particle group 3 to be measured is irradiated. An optical lens 5 for condensing the light that has passed through or been scattered by the spray particle group 3 is disposed at an appropriate distance from the colmeter lens 2, and a silicon photodetector, for example, is installed approximately at the focal point of the optical lens 5. Two annular photoelectric conversion elements 6, 7 consisting of
are arranged in concentric circles. In this case, the two photoelectric conversion elements 6 and 7 are arranged concentrically so as to face the optical lens 5 with the focus position of the optical lens 5 as the center.

The photoelectric conversion elements 6 and 7 arranged in this manner generate current by receiving light, and the current increases or decreases depending on the amount of light, which can be extracted as a current signal. This current signal is amplified by logarithmic amplifiers 8 and 9, each having the same characteristics, and is input to a subtraction circuit 10. This subtraction circuit 10 subtracts the current signals input from the logarithmic amplifiers 8 and 9 and outputs the result, which is converted by the A/D converter 11 and input to the arithmetic unit 12, where it is calculated. The results are digitally displayed on the display 13.

To explain the calculation of the representative particle size by the arithmetic unit 12, first, the intensity distribution of the light scattered forward from the particle group 4 after receiving the parallel laser beam 3 is the superposition of the scattered light intensities from the individual particles. The distribution of scattered light intensity from individual particles is calculated theoretically. When we investigated the intensity distribution of scattered light by particle groups for various particle size distributions, we found that the light intensity at the focal point
The ratio of Io to the light intensity I(θ) at the focal plane due to the scattering angle θ is the ratio of the representative particle diameter D to the light wavelength λ (πD/
As shown in the graph of FIG. 3, it was found that the relationship between λ) and θ is almost constant in the range of O<(πD/λ)θ<2.5. Therefore, I
The relationship between (θ)/Io and (πD/λ)θ can be expressed as lnI(θ)/Io=−β(πD/λθ) ² with sufficient accuracy for practical purposes, so if the predetermined angles θ ₁ and θ It is calculated from the ratio of the intensities at ₂ using the following formula.

Therefore, the laser beam 3 is irradiated onto the atomized particle group 4 to be measured, and among the light that is focused through the optical lens 5, the light that is focused at the focal position is received by the photoelectric conversion element 7 and is converted into a predetermined current. is output,
The light scattered at a predetermined angle is received at a ring-shaped position on the focal plane, that is, by the photoelectric conversion element 6,
A predetermined current is output depending on the amount of light. The difference between these two currents is outputted by a subtraction circuit 10 via logarithmic amplifiers 8 and 9, respectively, and the output is A/D converted and immediately calculated by the arithmetic unit 12 based on the above formula, and the result is Immediately display 1
It is displayed in 3. Therefore, the displayed value indicates the diameter of the atomized particles.

[Effects of the Invention] As explained above, the spray particle diameter measuring device according to the present invention irradiates the spray particle group to be measured with a laser beam, and collects the light that has passed through the spray particle group, that is, the scattered light, with an optical lens. The particle size can be measured immediately by emitting light, placing two annular photoelectric conversion elements on the plane of its focal position, and performing a predetermined calculation using a calculator based on the output difference between the two photoelectric conversion elements. Unlike conventional methods, this method does not require a huge amount of sampling data at all, and also has the excellent effect of being able to measure particle diameters instantly without any data comparison work.

Also, in its configuration, the laser oscillator, optical lens, a pair of annular photoelectric conversion elements, a logarithmic amplifier, a subtraction circuit, an arithmetic unit, and a display can be integrated and formed, so the entire structure can be made smaller and more compact. It also has this excellent effect.

[Brief explanation of drawings]

Fig. 1 is a schematic side view of the device according to the present invention, Fig. 2 is a block diagram schematically showing the main parts of the device, and Fig. 3 is the relationship between the representative particle size and the intensity of scattered light. This is a graph showing. 1... Laser oscillator, 2... Collimator lens, 3... Parallel beam, 4... Spray particle group, 5...
...Optical lens, 6, 7... Photoelectric conversion element, 8, 9
... Logarithmic amplifier, 10 ... Subtraction circuit, 11 ...
A/D converter, 12... arithmetic unit, 13... display device.

Claims (1)

[Claims] 1. A laser oscillator, an optical lens that condenses light scattered forward from a group of spray particles irradiated with a laser beam, and two concentric photoelectrons arranged at the focal point of the optical lens. a logarithmic amplifier that amplifies the current signals from the photoelectric elements and the photoelectric elements, respectively;
a subtracter that outputs the output difference from each of those amplifiers, and an A/D converter that converts the output from A/D,
A particle size measuring device for atomized particles, which includes a calculator that calculates the particle size from A/D converted output, and a display that digitally displays the calculation result. 2. The atomized particle size measuring device according to item 1 above, further comprising a collimator lens for collimating the laser beam of the laser oscillator.