JPS61170619A - Correlation flowmeter - Google Patents

Abstract

PURPOSE:To make possible the measurement of a flow rate in a low flow rate region and to expand a flow rate measuring range by determining the flow rate in a low flow rate region by using one sensor of a correlation flowmeter and determining the flow rate of fluid to be measured from such flow rate. CONSTITUTION:The sensor 12 detects the flow rate and temp. of the fluid to be measured and a detector 20 can determine the flow rate of the fluid to be measured if the difference between the output signal of the detector 20 which detects the temp. of the fluid to be measured and the output signals of either of the sensors 11 and 12 is determined in the flow rate region where the outputs of the sensors 11 and 12 can be correlated. The flowmeter 14 can calculate subsequently the flow rate by using the output signal of a current meter 21 if the current meter 21 is operated by a correlation calculator 13 when the cross correlation is no more obtd. by the calculator 13.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a correlation flowmeter, more specifically, one sensor of the correlation flowmeter can also be used as a flow rate sensor,
Therefore, in a small flow rate region where no correlation can be obtained, the flow rate sensor is used to determine the flow rate.

Sensors that detect fluid signals are arranged at certain distances along the flow of the fluid to be measured, and the cross-correlation function of the fluid turbulence component signals in the fluid signals transmitted from each of the sensors is determined. A so-called correlation flowmeter is well known, which calculates the flow velocity by dividing the above-mentioned fixed distance by the delay time at the maximum value of the correlation function.

That is, a correlation flowmeter is an absolute flowmeter. However, when the flow velocity of the fluid to be measured is slow, the power spectrum that indicates the strength of the turbulence component in the fluid decreases, so the detection signal level also decreases, making it difficult to accurately determine the cross-correlation when the flow velocity of the fluid to be measured is slow. Therefore, the measurement error in the low flow rate region was large, making it impossible to measure low flow rates, and the flow rate measurement range was limited.

On the other hand, a thermal flowmeter is an inferential flowmeter that utilizes the fact that the amount of heat released from a heating element in a fluid flow is proportional to the flow rate. Since the thermal conductivity of a fluid differs depending on the gas component, it is necessary to correct it if the type of fluid to be measured differs.

The present invention was made in view of the above-mentioned circumstances.
In particular, this was done with the aim of compensating for measurement errors in the low flow velocity region of a correlation flowmeter.

1-11 Fig. 1 is a configuration diagram for explaining one embodiment of a correlation flowmeter according to the present invention. a sensor 13 disposed within the pipe 1 at a predetermined distance Ω along the flow direction of the fluid to be measured;
is a correlation calculator, 14 is a flow rate calculator, 15 is a display, 16
is a pressure detector.

Reference numeral 17 denotes a temperature detector, and sensors 11 and 12 are composed of heat-sensitive sensors such as a thermistor, a hot wire, and a platinum resistance wire. The flow rate is calculated by dividing the constant distance Q by the delay time t at the maximum value of this cross-correlation (CQ/l), and the flow rate is calculated by the flow rate calculator 14 using the detectors 16 and 17. The flow rate is calculated taking into consideration the pressure and temperature of the detected fluid to be measured, the diameter of the flow path pipe 1, etc., and the result is displayed on the display 15. The above is a well-known correlation flowmeter. However, in the correlation flowmeter as described above, when the flow velocity of the fluid to be measured is slow, it is not possible to obtain a cross-correlation between the sensors 11 and 12, which causes the measurement This was a cause of error.

The present invention was made in order to eliminate the drawbacks of the prior art as described above, and the detector 20 and current meter 21 in the figure are added according to the present invention. In the present invention, the detector 20 is a thermistor or a hot wire similar to the sensors 11 and 12.

The detector 2 is composed of a thermal sensor such as a platinum resistance wire.
0 is configured so as not to be affected by the flow velocity of the fluid to be measured, and in the illustrated example, the heat sensitive part 20a is connected to the orifice 20b.
Therefore, the detector 20 detects the temperature of the fluid to be measured when the flow velocity of the fluid to be measured is zero. Therefore, in the flow velocity region where the outputs of the sensors 11 and 12 can be correlated, the detector 2
In the illustrated example, the sensor 12 detects the flow velocity and temperature of the fluid to be measured, and the detector 20 detects the flow rate and temperature of the fluid to be measured. Since only the temperature of the fluid is detected, the flow velocity of the fluid to be measured can be determined. The current meter 21 determines the flow velocity of the fluid to be measured as described above, and by doing so, when the correlation calculator 13 no longer determines the cross-correlation.

If the current meter 21 is activated by the correlation calculator 13, the flow meter 14 can thereafter calculate the flow rate using the output signal of the current meter 21.

As is clear from the above explanation, according to the present invention, one sensor of the correlation flowmeter is used to determine the flow velocity in the low flow velocity region, and from this, the flow rate of the fluid to be measured is determined. It becomes possible to measure the flow rate in a low flow velocity region, which was impossible to measure with a conventional correlation flowmeter, and it is possible to expand the flow rate measurement range and improve measurement accuracy. Furthermore, since the sensor used to determine the cross-correlation is also used to determine the flow velocity in the low flow velocity region, the structure is simple and the cost is low.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram for explaining one embodiment of a correlation flowmeter according to the present invention. 1...Flow pipe, 11, 12...Sensor, ↓3...
Correlation calculator, 14...Flow rate calculator, 15...Display device, 16...Pressure gauge, 17...Thermometer, 20...Detector, 21... Current velocity meter.

Claims (1)

[Claims] A correlation flowmeter is configured by a heat-sensitive fluid turbulence sensor installed between two points upstream and downstream of the flow path to be measured, and a detector for detecting zero flow velocity is provided in the flow path to be measured, and the correlation flowmeter is Within the usable flow rate range, one of the sensors is calibrated using the output of the detector so that it can also be used as a flow rate sensor, and in the small flow rate range where correlation cannot be determined, the flow rate sensor is used to calculate the correlation. A correlation flowmeter characterized in that the flow rate is determined from the flow velocity.