JPH0726666Y2 - Flow measurement device detector - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention relates to a flow rate measuring device for measuring a flow rate in an open channel, an underdrain or the like in which a weir or a flume cannot be installed, and particularly to a detector thereof.

(Prior art and its problems) When measuring the flow rate in sewers, the water depth is measured over time, and the cross-sectional water flow area is geometrically determined from the water depth. The flow velocity is, for example, Manning's average flow velocity formula V = 1 / nR ^{2 / 3} I ^1/2 V: Average flow velocity (cm / sec) R: Diameter depth (cm) = A / PP: Wet edge (cm) I: Pipe bottom gradient n: Roughness coefficient.

Therefore, the flow rate is obtained as the product of the above-mentioned running water cross-sectional area and the average flow velocity. When using the average flow velocity formula, the roughness coefficient n of the inner surface of the pipe and the pipe bottom gradient I are uniform values in the actual pipeline. However, the roughness coefficient n varies depending on the contents flowing in the pipe or the degree of deterioration, and the pipe bottom slope I is generally different from the design slope due to poor construction or local subsidence.

However, it is impossible to set these appropriate values by field measurement, and a large error occurs in the average flow velocity to be obtained. Actually, it has been a problem than before that there is a large gap between the actual flow rate and the measured flow rate.

In addition, another method, such as measuring water depth and flow velocity separately,
In the method of obtaining the flow rate as the product, for example, in the case of a velocity meter such as an ultrasonic velocity meter, it takes time and effort to install the sensor, the installation place is limited, and an error in the flow rate occurs depending on the atmospheric conditions. There was a problem.

Further, when an electromagnetic velocity meter is used for this flow velocity measurement, it is desirable that separation does not occur in the flow, but generally the flow through the sewer pipe or the like is turbulent. Therefore, it is necessary to consider so that the turbulence does not become large near the electrodes of the electromagnetic velocity meter.
For this reason, since the front surface of the detector 1 does not disturb the water flow, the flowing water upstream end face 3 of the detector housing 2 has a straight line in the vertical direction and a parabolic quadric surface in the horizontal direction as shown in FIG. I was using it.

Since the above-mentioned detector 1 is an electromagnetic velocity meter, the flowing water downstream side end of the detector casing 2 on the downstream side of the flow velocity detecting electrode 5 is arranged as shown in FIG. 5 so as not to disturb the water flow of the flow velocity detecting electrode 5. Then, it is held at a fixed position from outside by the support rod 4.

However, in the head shape of the detector 1 shown in FIG. 4, as shown in the flow velocity-output characteristic diagram shown in FIG. 3, each flow velocity (in this experiment, since the detector 1 is moved by a trolley in a stationary water tank, the flow velocity is The output voltage of the detector 1 with respect to the trolley speed is not necessarily good in linearity, which causes an error.

An object of the present invention is to solve the above problems and provide a detector 1 in which no error occurs.

(Means for Solving the Problem) In order to achieve the above-mentioned object, the flowing water upstream end face 3 of the detector housing 2 has a modified truncated pyramid shape, and the bottom surface of the modified truncated pyramid has a detector housing. Same as the cross section of the body 2, the upper surface is substantially flat, and the ridge line portion between the upper surface and each side surface is largely rounded to form one cubic curved surface.

(Operation) The detector 1 having the head having the above-mentioned shape almost completely prevents the disturbance of the water flow from the head to the side surface, and the above-mentioned linearity is almost completely except when the flow velocity is extremely slow. Is held.

(Example) In Fig. 2, as in the case of Fig. 3, the detector 1 was fixed to a trolley for an experiment, and this trolley was moved along a stationary water tank to run the detector 1 in water to obtain data. It was taken. On the contrary, this is equivalent to the case where the detector 1 is stationary in running water and the flow velocity is measured.

In the detector 1 used for this measurement, the flowing water upstream end face 3 of the detector housing 2 has a truncated pyramid shape as shown in the first illustration, and the bottom surface of the modified pyramid is the detector housing 2 The upper surface is substantially flat, and the ridge line portion between the upper surface and each side surface is largely rounded to form one cubic curved surface.

In addition, since the usage method and the fixing method are the same as the conventional example,
The description is omitted.

(Effect of the Invention) As described above, since the water flow is not disturbed at each flow velocity and there is almost no measurement error, accurate measurement is possible.

[Brief description of drawings]

FIG. 1 is an external view of the detector of the present invention, FIG. 2 is a flow velocity-output characteristic diagram of the detector of the present invention, FIG. 3 is a flow velocity-output characteristic diagram of a conventional detector, and FIG. FIG. 5 is an external view of the detector, and FIG. 5 is a holding state diagram of the detector. 1: Detector, 2: Detector housing, 3: Upstream end face.

Claims (1)

[Scope of utility model registration request] 1. In a detector of a flow rate measuring apparatus which is immersed in running water, an end face of the detector casing on the flowing water upstream side has a shape of a truncated pyramid, and the bottom surface of the deformed pyramid has a detector casing. A detector of a flow measuring device, which has the same upper surface as a cross section and a substantially flat upper surface, and the ridge line portion between the upper surface and each side surface has a large roundness to form one cubic curved surface.