JPH05232007A - Voif fraction measuring device - Google Patents

Abstract

PURPOSE:To accurately obtain the time average of the void fraction by subjecting the output of a radiation detector to logarithmic conversion, and then by subjecting it to integration or averaging process. CONSTITUTION:A radiation source 1 emits X-rays in a pulse state, and they are radiated on a subject 2 in which a two-phase flow gaseous matter mixed with a liquid such as water or oil is passed through a pipe. The transmitted rays are detected by a detector 3 in which a semiconductor detector and a photoelectric converting element are combined. The output current thereof is converted into a voltage by an amplifier 4 for being amplified, and is subjected to logarithmic conversion by a logarithmic converter 5. The signal subjected to logarithmic conversion is subjected to time integration or averaging process by means of an integration or averaging process circuit 6. After the instantaneous values of transmission data have been subjected to logarithmic conversion, by subjecting them to time integration, the void fraction can be obtained with a good accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a void fraction measuring device using radiation, and more particularly to a void fraction measuring device having a function of accurately measuring a time average value of void fractions.

[0002]

2. Description of the Related Art As a conventional void fraction measuring apparatus utilizing radiation, there is one utilizing a CT (Computed Tomography) apparatus. The structure is such that X-ray CT from the viewpoint of patents, X-rays are continuously irradiated using an X-ray tube as an X-ray source, as described on pages 81 to 83 of the Japan Patent Office (1986). As described on pages 160 to 161, the X-ray detector is designed so that a signal passing through an amplifier, an integrator, and an A / D converter after a detection element is logarithmically converted when passing through a LOG converter. It was At this time, the logarithmic conversion may be performed by using a dedicated converter or may be processed by computer software.

[0003]

The above-mentioned prior art utilizes a device which is widely used for medical purposes for measuring the void rate. However, the void moves quickly, and the imaged portion is taken within the tomographic imaging time per cross section. However, there was a problem that the measurement accuracy was extremely poor because the state of was changed. As an example, consider a case where a void ratio of a two-layer flow flowing in a pipe is measured and a specific cross section is photographed. It is assumed that a void exists at the imaging position at the first measurement time, the void ratio is 100%, and the radiation count value is 1000 counts. Then, at the moment of the next measurement, it is assumed that the void shifts from the imaging position, the void rate becomes 0%, and the radiation count value becomes 10 counts. If the above cycles occur continuously and the measurement intervals are equal, the average void ratio is 50% and the radiation count value should be 100 counts, but the actual count value average is 505 counts. Therefore, there is a problem that the void ratio calculated back based on this count value is 85%, which is largely different from the actual value.

An object of the present invention is to accurately obtain the time average of the void fraction.

[0005]

In order to achieve the above object, an apparatus including an X-ray source for generating X-rays in a pulse shape, a current type radiation detector, an amplifier, a logarithmic converter, and an integrating or averaging circuit is provided. It is composed.

Further, a radiation source for continuously generating X-rays or γ-rays, a current type radiation detector, an amplifier, a logarithmic converter,
And an integrating or averaging circuit.

Further, the apparatus is composed of a radiation source for continuously generating X-rays or γ-rays, a pulse type radiation detector, an amplifier, a discriminator, a counter, a logarithmic converter, and an integrating or averaging circuit. ..

When using a current type radiation detector,
It is also possible to provide a sample hold and an A / D converter after the amplifier and logarithmically transform and integrate or average the digital signal by computer processing.

[0009]

In the circuit after the radiation detector, the time average value of the void ratio can be accurately obtained by logarithmically converting the measured value and then performing time integration or averaging.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the radiation source 1 is an apparatus such as an accelerator that generates pulsed X-rays. The subject 2 is a pipe having a two-layer flow. The two-layer flow is a mixture of gas such as water and oil with gas, and this device measures the ratio (volume) of gas. The detector 3 is a combination of a semiconductor detector or a scintillator and a photoelectric conversion element. The output current from the detector 3 is converted into a voltage by the amplifier 4 and amplified, and the signal thereof is converted by the logarithmic converter 5. Logarithmically converted. The logarithmically converted signal is subjected to time integration or averaging processing by the integration or averaging processing circuit 6. According to the present embodiment, the void ratio can be accurately obtained by logarithmically converting the instantaneous value of the transmission data and then performing time integration.

A second embodiment of the present invention is shown in FIG. In FIG. 2, the radiation source 1 is an apparatus such as an X-ray tube or a γ-ray source that generates radiation with a constant intensity. The subject 2 is a pipe in which a two-layer flow is applied, and the detector 3 is a combination of a semiconductor detector or scintillator and a photoelectric conversion element. The output current from the detector 3 is converted into a voltage by the amplifier 4 and amplified, and the signal is logarithmically converted by the logarithmic converter 5. The logarithmically converted signal is subjected to time integration or averaging processing by the integration or averaging processing circuit 6. According to this embodiment, the void ratio can be accurately obtained by logarithmically converting the transmission data and then performing time integration.

A third embodiment of the present invention is shown in FIG. In FIG. 3, a radiation source 1 is an apparatus such as a γ-ray source that generates radiation with a constant intensity. The subject 2 is a pipe in which a two-layer flow is applied, and the detector 3 is a combination of a scintillator and an element such as a photoelectron multiplier which outputs a signal in pulses corresponding to photons of radiation. .. The output current from the detector 3 is converted into a voltage and amplified by the amplifier 4,
Only the signal having a specific intensity is selected by the discretion 7 and counted by the counter-8. The count value is logarithmically converted by the logarithmic converter 5, and the logarithmically converted signal is time-integrated or averaged by the integration or averaging circuit 6. According to the present embodiment, the void ratio can be accurately obtained by logarithmically converting the transmission data and then performing time integration.

A fourth embodiment of the present invention is shown in FIG. FIG. 4 shows a case where the present invention is applied to a tomography apparatus. In FIG. 4, the radiation source 1 is a device that generates radiation, such as an accelerator, an X-ray tube, a γ-ray source. The subject 2 is a pipe in which a two-layer flow is applied, and the detector 3 is a combination of a scintillator and a photoelectric conversion element or a radiation detector such as a semiconductor detector. The radiation source 1 and the detector 3 are installed on the CT scanner-9 and perform translational or rotational scanning. Then, the output from the detector 3 is amplified and A / D converted in the signal processing device 10 and then subjected to logarithmic conversion processing and integration or averaging processing in the arithmetic device 11. Transmission data from all directions passing through the subject 2 is collected, processed by the above-mentioned method, and then CT is calculated by the arithmetic unit 11.
The tomographic image of the two-layer flow can be obtained on the display device 12 by performing the calculation based on the algorithm. According to this embodiment, the void ratio can be accurately obtained by logarithmically converting the transmission data and then performing time integration, and a tomographic image in which an error such as an artifact on the image is suppressed to a minimum. There is a desired effect.

[0014]

According to the present invention, there is an effect that the time average of the void fraction can be accurately obtained by logarithmically converting the radiation detector output and then performing integration or averaging.

Further, the tomography apparatus using the present invention is effective in obtaining a high-quality tomographic image with little error in images such as artifacts.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is a block diagram showing another embodiment of the present invention.

[Explanation of symbols]

1 ... Radiation source, 2 ... Subject, 3 ... Radiation detector, 4 ... Amplifier, 5 ... Logarithmic converter, 6 ... Integration and averaging circuit,
7 ... Discrete, 8 ... Shiina.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Miyai 1168 Moriyama-cho, Hitachi, Hitachi

Claims (4)

[Claims] 1. A void fraction measuring device comprising a radiation source, a radiation detector and a detector circuit, wherein a detector circuit is provided with an integration or averaging circuit after the logarithmic conversion circuit. 2. A void fraction measuring device according to claim 1, wherein a device for generating radiation in a pulse shape is used. 3. The detector circuit according to claim 1, wherein an A / D converter is provided after the sample-hold or peak-hold circuit, and the output of the A / D converter is input to a computer. Then, the void fraction measuring device is characterized by performing logarithmic conversion processing in a computer and then performing integration or averaging processing. 4. A tomography apparatus-type void fraction measuring apparatus, characterized in that the apparatus according to any one of claims 1 to 3 is used for a radiation source and a detector system of a tomography apparatus.