JPS5926251Y2 - flow measurement duct - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a duct for measuring the flow rate of an air conditioning duct, an exhaust duct, an air supply duct, etc.

Conventionally, the following two methods have been used to measure the air volume in differential pressure ducts.
There are different methods.

One method is to arrange multiple pitot tubes in a cross section perpendicular to the flow path of the duct, find the average flow velocity of the duct, and multiply this by the cross-sectional area of the duct.The other method is to In this method, a throttle mechanism is provided in the duct to locally increase the flow velocity in the duct, and the pressure as a flow signal is amplified and detected.

However, when considering a normal duct flow velocity of 2 to 20 m/sec, the pressure signal for air volume detection generated by the former method is approximately 0°24 to 24 mmH at normal temperature and pressure.
The pressure remains within the range of 100 g, which is too small to be measured with a normal pressure measuring manometer, causing an error in air volume measurement.

In addition, in the latter method, the pressure as a flow signal is magnified and detected, but a pressure loss occurs because the throttling mechanism is applied to the entire flow path, which may reduce the duct flow velocity or reduce the power system that generates the duct flow. There were drawbacks such as an increase in operating horsepower.

The present invention eliminates these conventional drawbacks by using an elliptical pipe as a flow velocity measurement sensor instead of a pitot tube, and amplifies the pressure signal as an average flow velocity signal without increasing pressure loss. It is something.

An embodiment of the present invention will be described in detail below with reference to the drawings.

Figure 1 shows an embodiment of the flow rate measuring duct of the present invention, a partially cutaway front view, and Figure 2 shows II-I of Figure 1.
I sectional view and FIG. 3 are longitudinal sectional front views of the total pressure measuring elliptical sensor.

In the figure, 1 is the duct body, 2 is a total pressure measuring elliptical sensor made of an elliptical pipe, 3 is a static pressure measuring elliptical sensor also made of an elliptical pipe, and 4 and 5 are installed on the elliptical sensors 2 and 3. This is a pressure conduit.

The total pressure measuring elliptical sensor 2 and the static pressure measuring elliptical sensor 3 are arranged symmetrically along the flow of the wind, with a slight gap (hereinafter referred to as the throat) on the upstream side, and a flow separation on the downstream side. It is expanded to an angle that does not occur.

That is, the gap formed by the pair of elliptical sensors 2 and 3 forms a second-order Venturi shape.

Note that there is a total pressure hole 2a at the tip of the flow path of the total pressure measurement elliptical sensor 2.
are bored in several places, and the total pressure of the flow is guided into the total pressure measurement elliptical sensor 2 through these total pressure holes 2a.

In addition, a pressure detection hole 4 is also provided in the pressure conduit 4 provided therein.
A is provided at several locations to average out variations in the total pressure caused by spatial non-uniformity of the flow, and is guided to the outside through the pressure conduit 4.

On the other hand, several static pressure holes 3a are provided on the side of the static pressure measurement elliptical sensor 3 on the throat side, and the static pressure of the accelerated flow is guided into the inside thereof, and further externally through a pressure conduit 5. be guided.

Note that the number of static pressure holes 3a and the pressure detection 7L5 of the pressure conduit 5
The number a is the same as in the case of the total pressure measuring elliptical sensor 2 and the pressure conduit 4.

The operation of such a configuration will be explained next.

First, the flow from the direction of the arrow is guided by the duct and enters the duct body 1, and is separated into a flow path sandwiched between the total pressure measuring elliptical sensor 2 and the static pressure measuring elliptical sensor 3, and other parts.

The former is accelerated by the Venturi effect and passes through the throat.

The flow from the direction of the arrow is averaged by several total pressure holes 2a provided at the tip of the flow path of the total pressure measuring elliptical sensor 2, and the total pressure of the flow is measured within the total pressure measuring elliptical sensor 2. lead to.

This total pressure is then conducted to the outside via a pressure conduit 4.

On the other hand, at the throat position, the static pressure of the accelerated flow is guided into the interior by the static pressure hole 3a of the static pressure measurement elliptical sensor 3, and further guided to the outside by the pressure conduit 5.

Therefore, the flow rate can be measured by measuring the pressure difference between the side pressure conduits 4 and 5.

At this time, the flow that has passed through the throat is expanded and, after recovering its pressure, is guided to the rear of the duct body 1, and the other parts are slightly accelerated between the duct surface and the total pressure/static pressure measuring elliptical sensors 2 and 3. pass while being

This reduction in static pressure serves to compensate for the pressure loss that occurs when the former flow is accelerated at the throat and then diffused.

Note that the shape of the duct may be a rectangular shape or a single shape, and in order to improve accuracy, a plurality of these air volume measurement sensors may be used.

It is also possible to use only the airflow measurement sensor and pressure conduit by inserting them into an existing duct.

As explained in detail above, according to the present invention, since an elliptical pipe is used for the measurement sensor, it is possible to provide a large number of total pressure holes and static pressure holes. The sensor itself constitutes a flow acceleration mechanism, and the flow is accelerated only within this sensor, so the pressure loss of the entire device is small.

Furthermore, since the static pressure of the accelerated flow is measured, the pressure as a flow rate signal can be amplified, and low flow rates can be measured with high accuracy with low pressure loss.

[Brief explanation of drawings]

Fig. 1 shows an embodiment of the flow rate measuring duct of the present invention, a partially cutaway front view thereof, and Fig. 2 shows II-II of Fig. 1.
FIG. 3 is a cross-sectional view, and FIG. 3 is a vertical front view of the total pressure measuring elliptical sensor. 1... Duct body, 2... Total pressure measurement elliptical sensor, 2a... Total pressure hole, 3... Static pressure measurement elliptical sensor, 3a...・・・Static pressure hole, 4, 5・
...Pressure conduit, 4a, 5a...Pressure detection hole.

Claims (1)

[Scope of utility model registration request] The total pressure measuring elliptical sensor and the static pressure measuring elliptical sensor, each composed of an elliptical pipe, are symmetrical along the flow, and have a slight throat on the upstream side, and are spread out at an angle that prevents the flow from separating on the downstream side. The elliptical sensor for measuring total pressure has a total pressure hole at the tip of the flow path, and the elliptical sensor for measuring static pressure has several static pressure holes on the side and throat side. , a flow measurement duct with pressure conduits with pressure detection holes at several locations in each sensor to guide the total pressure and static pressure to the outside.