CN109540227B - A U-shaped channel flow measurement device and measurement method - Google Patents

Abstract

The invention discloses a U-shaped channel flow measuring device and a measuring method. The disclosed device comprises a measuring cylinder, a cylinder is arranged in the measuring cylinder, and the cylinder and the measuring cylinder are connected through a connectorFixedly connecting; a plurality of through holes are formed in the outer wall of the measuring cylinder along the axial direction and are positioned in the same radial direction, and a water accumulation area is formed between the cylinder body and the inner wall of the measuring cylinder; the outer wall of the measuring cylinder is provided with a first plate and a second plate, the first plate and the second plate are positioned on two sides of the same radial direction, and the radial direction where the plurality of through holes are positioned is vertical to the radial direction where the first plate and the second plate are positioned. The disclosed method utilizes

And calculating the flow of the U-shaped channel. Two plates are arranged on two sides of the water gaging column, so that the critical flow can be formed, the volume of the water gaging column is effectively reduced, the water depth in the column is equal to the water depth of a stagnation point, and the water depth of the stagnation point can be obtained by measuring the water depth in the column. The water depth fluctuation is extremely small, the measurement is convenient, and the precision is improved.

Description

A U-shaped channel flow measurement device and measurement method

technical field

The invention relates to a channel water measuring device, in particular to a U-shaped channel movable plate column water measuring tank.

Background technique

The U-shaped channel is a small channel widely used in irrigation areas in China. The cross-section of the channel is composed of a circular arc in the lower part and two straight lines tangent to the circular arc in the upper part.

The most commonly used method of measuring water in small U-shaped channels is to measure water through special water measuring structures, which mainly include fixed and mobile types. The U-shaped final channel has a wide distribution range and a large number. The construction of a large number of fixed water tanks requires a large investment and is easy to be damaged. Therefore, many scholars have developed a variety of installation and disassembly introductions. Portable mobile water metering equipment.

According to the principle of critical flow, Hager (1985) proposed a mobile water measuring method in which a cylinder was placed in the channel to measure the flow in the channel. Prototype tests were carried out in rectangular, trapezoidal and U-shaped channels and the corresponding flow formulas were deduced.

He Wuquan et al. (2006) and Ji Qingfeng et al. (2007) further studied the flow formula of the U-shaped channel mobile cylindrical water tank, and improved the flow measurement accuracy of this type of water tank.

Liu Jiamei et al. (2013) added a V-shaped tail to the tail of the cylindrical measuring tank to reduce the head loss and the difference between the upstream and downstream water levels.

It can be seen from the above research that the more practical U-shaped channel mobile water tank can provide flow measurement that meets the accuracy requirements. However, these mobile water measuring tanks generally have the problems of large size and insufficient portability. In addition, the research on the cross-sectional structure and size of the channel suitable for measurement of these mobile water measuring tanks is not thorough enough, which hinders the mobile water measuring tanks in the irrigation area. Further promotion and application.

SUMMARY OF THE INVENTION

Aiming at the defects or deficiencies of the prior art, the present invention provides a U-shaped channel flow measurement device.

The U-shaped channel flow measuring device of the present invention comprises a measuring cylinder, a cylinder is arranged in the measuring cylinder, and the cylinder and the measuring cylinder are fixedly connected by a connecting body; a plurality of through holes are opened on the outer wall of the measuring cylinder along the axial direction. , and the plurality of through holes are located in the same radial direction, and there is a water accumulation area between the cylinder and the inner wall of the measuring cylinder; the outer wall of the measuring cylinder is installed with a plate 1 and a plate 2 along the axial direction of the measuring cylinder, and the plate 1 The plate 2 and the plate 2 are located on both sides of the same radial direction, and the radial direction in which the plurality of through holes are located is perpendicular to the radial direction in which the plate 1 and the plate 2 are located.

In some embodiments, the cylinder of the measuring device of the present invention includes an inner cylinder and a fixing rod, the inner cylinder and the measuring cylinder are connected by a connecting member, and the connecting member is located at the end of the cylinder and the measuring cylinder.

Further, the measuring device of the present invention also includes a water level measuring sensor.

In some embodiments, the measuring device of the present invention further includes an installation device, the installation device includes two installation rods and two installation seats, one end of the installation rod is provided with an installation groove, and the installation seat is used for installing the other side of the installation rod. At one end, the mounting slot is used for mounting the first board or the second board.

Preferably, a spring is connected between one end of the plate of the measuring device of the present invention and an installation rod, and a spring is installed between the second plate and another installation rod.

Meanwhile, the present invention provides a U-shaped channel flow measurement method, characterized in that the method includes:

Using the measuring device according to claim 1 to measure the water depth h of the water accumulation area in the channel and the throat width B _c corresponding to the water depth h, B _c =Bd, B is the channel width corresponding to the water depth h in the water accumulation area, m; d is the sum of the outer diameter of the measuring cylinder and the width of the first and second plates on both sides, m;

Use formula (1) to calculate the U-shaped channel flow:

In formula (1):

Q——flow;

h——water depth in the stagnant water area, m;

ε——shrinkage ratio;

i——the bottom slope of the channel;

g——gravitational acceleration, m/s ² ;

p, α ₁ , α ₂ , α ₃ are parameters.

In some embodiments, 1/500≤i≤1/5000 of the present invention.

Preferably, in the present invention, p=0.3184, α ₁ =1.44235, α ₂ =-0.00182, and α ₃ =0.0145.

Preferably, the value range of ε in the present invention is: 0.41≤ε≤0.67.

Compared with the prior art, the advantages of the present invention are as follows:

1. The measuring device of the present invention is composed of a cylinder and two plates symmetrically arranged on both sides of the cylinder, which is simple to manufacture and has low cost; the fixing of the water column and the channel can be completed by the steel bar vertically extending from the bottom and the upper slot, and the installation can be completed. Easy to disassemble.

2. Compared with the existing cylindrical water measuring tank and the cylindrical water measuring tank with tail wing, the plate column measuring water tank in the present invention is provided with two plates on both sides of the water measuring column, which can effectively reduce the amount of water column while ensuring that a critical flow can be formed. volume.

3. When the mobile measuring tank of the prior art measures the stagnant water depth in front of the column (the stagnant point is the point where the flow velocity formed at the front end of the obstacle is zero when the water flow encounters an obstacle) to calculate the flow, because the water depth exists Certain fluctuations will bring difficulties to bathymetry and adversely affect the accuracy. According to the invention, through holes are arranged at the front end of the water-facing side of the cylindrical part of the measuring water column, which are distributed at equal intervals along the axial direction of the outer cylinder, so that the water flows into the cylinder through the small holes, and the water depth in the column is measured. The stagnant water depth can be obtained from the inner water depth. The water depth fluctuation is extremely small, which facilitates the measurement and improves the accuracy.

4. The device of the present invention is especially suitable for measuring the water depth of the U-shaped channel from the arc bottom to the design water depth. On the premise of meeting the requirements of measurement accuracy, the range of the bottom slope of the channel suitable for the water measuring tank is 1/500-1/5000, which can be applied to most of the final U-shaped channels in the irrigation area.

Description of drawings

Fig. 1 is the plan view of the measuring device of the present invention;

Fig. 2 is the A-A sectional view of Fig. 1;

Fig. 3 is the B-direction view of Fig. 1;

Figure 4 is a schematic diagram of the throat section.

Detailed ways

Unless otherwise specified, the cross-section or cross-section described in the present invention is a cross-section cut by a cross-section perpendicular to the water flow direction.

The measuring cylinder 2, the wing plate 4 and the U-shaped channel 1 of the present invention jointly form a critical flow. On the one hand, the cylinder 3 together with the measuring cylinder 2 and the through hole 5 constitute a communication device; The through hole 5 realizes the communication between the water depth in the cylinder and the water depth at the stagnation point, so that the cavity between the inner and outer cylinders of the water column of the water inflow is the water accumulation area of the measuring device.

The design selection of the device of the present invention in terms of size only needs to meet the requirements of the measurement object and measurement accuracy. It should be noted that, in specific implementation, the total width range of the measuring device can be calculated according to the cross-sectional size of the channel, the water depth range and the shrinkage ratio range of the present invention, and then the width of each component is selected within this range. In one embodiment, the width of the wings 4 on both sides can be selected to be the same, and the total width thereof is equal to the outer diameter of the outer cylinder 2 . During measurement, the ideal positional relationship of the measuring device of the present invention is that the measuring cylinder is vertically installed in the U-shaped channel, the central axis of the measuring cylinder is located on the central axis of the channel, and the radial directions of the wings on both sides are perpendicular to the central axis. After installation, the measuring cylinder 2, the column body 3 and the wing plate 4 should preferably have the same height and be 5-10cm higher than the top of the channel.

The invention adopts the dimensional analysis method to deduce the flow formula of the plate column measuring tank, and carries out regression analysis according to the prototype observation test results to obtain the relevant parameters in the formula, so as to determine the final form of the flow formula. According to the principle of dimensional harmony and the overcurrent phenomenon of water flow in the U-shaped channel, the flow formula is derived as:

where:

Q——flow, m ³ /s;

h——water depth in the stagnant water area, m;

B _c ——the throat width, as shown in Figure 4, B _c =Bd, B is the channel width corresponding to the water depth h, m; d is the sum of the outer diameter of the measuring cylinder and the width of the wings on both sides, m;

，A₀为喉口断面处，水深h以下的渠道横断面面积；A_c为喉口断面处，水深h以下的过水横断面面积，即A_c等于A₀减去水深h以下的测量筒和两侧翼板的横断面面积；ε—shrinkage ratio,

, A ₀ is the cross-sectional area of the channel below the water depth h at the throat section; A _c is the cross-sectional area of the water passage below the water depth h at the throat section, that is, A _c is equal to A ₀ minus the measuring tube below the water depth h and the cross-sectional area of the wings on both sides;

i——the bottom slope of the channel;

g——gravitational acceleration, m/s ² ;

p, α ₁ , α ₂ , α ₃ ,——parameters. A specific method for determining the parameters p, α ₁ , α ₂ , α ₃ is:

The U-shaped channel with the channel made of plexiglass is adopted, and the slope can be adjusted;

The channel is 12m long, the bottom arc diameter is 40cm, the center angle is 152°, and the height is 45cm;

The material of each component of the device is also plexiglass, and its dimensions are shown in Table 1;

Set five different widths of water column (12.0cm, 14.0cm, 16.0cm, 18.0cm, 20.0cm), 6 groups of flow (20L/s, 25L/s, 30L/s, 35L/s, 40L/s, 45L /s), 4 groups of bottom slopes (1/500, 1/1000, 1/2000, 1/5000), a total of 5×6×4=120 groups of working conditions.

The actual flow in the channel is measured using the right-angled triangular water weir, and the SCM60 water level stylus is used to measure the water depth from the water surface to the bottom of the channel on the center line of the channel cross-section in the accumulated water area. A tailgate is set at the end of the channel to adjust the height of the water surface in the channel to ensure free outflow.

Table 1 Dimensions of water column

According to the above flow formula and the observation results of the prototype test, regression analysis was performed using OriginPro 2017 software, and the parameters in the formula were respectively: p=0.3184, α ₁ =1.44235, α ₂ =-0.00182, α ₃ =0.0145. The coefficient of determination R2 value of the ^formula is 0.9933, which is close to 1, and the fitting accuracy is high. The calculation formula is obtained:

Example 1:

As shown in Figures 1-3, the measuring device of this embodiment includes a measuring cylinder 2, a cylinder 3, and two side wings 4 (ie, the first plate and the second plate), wherein the cylinder 3 is located in the measuring cylinder 2, and the cylinder 3 It is fixedly connected with the measuring cylinder 2 through the connecting piece, and a row of through holes 5 are provided on the water-facing wall of the measuring cylinder.

In order to facilitate positioning and installation and fixation, the column body 3 includes an inner cylinder and a fixing rod 7. When using this structure, during installation, the fixing rod 7 is inserted through the inner cylinder into the bottom of the channel, and the inner cylinder and the measuring cylinder are fixed by connecting pieces. connection to realize the overall fixation of the measuring device. In actual engineering, the fixed rod can be made of various materials, such as steel bars. A more reliable solution is to cast a concrete base 12 at the bottom of the channel, and install the fixing rod in the concrete base to better determine the position of the channel centerline and the fixed amount of water column.

In order to facilitate the fixed installation on both sides of the device, the measuring device can be equipped with a mounting structure, which specifically includes two mounting rods 8 and two mounting seats 9. During measurement, the two mounting seats 9 are correspondingly installed on the channel walls on both sides, and the two are installed. The rods are installed on both sides, one end of the installation rod is fixedly installed in the mounting seat, and the other end can be provided with a mounting groove, which is snapped with the corresponding side of the wing plate 4, which can prevent the rotation of the movable part of the device. On the basis of this structure, the fixing method in the more preferred embodiment is to install the spring 10 between the mounting rod and the wing plate, one end of the spring 10 is fixed on the mounting rod 8, optionally fixed with screws, and the other end is fixed on the top of the wing plate On the reserved hole, it is used to tighten the measuring device.

In a more preferred embodiment, a rubber water stop 11 is provided between the bottom of the measuring device and the channel to prevent water flow from passing through the gap between the bottom of the measuring water column and the bottom of the channel.

When measuring, a water level measuring sensor 6 is placed between the measuring cylinder and the cylinder, also known as a wireless telemetry high-precision water level gauge, which is used for automatic measurement of water depth in the column and transmission of water level data (such as Yituo Sensing Technology, YT-LPC -00/YT-YL-0300 series sensors can meet the measurement needs of the device).

Example 2:

In this example, the diameter of the bottom arc is 40cm, the central angle is 152°, the height is 45cm, the width of the channel top is 54cm, and the flow rate in the channel bottom slope is 1/2000 U-shaped channel. The diameter of the measuring cylinder used is 8cm, the diameter of each through hole is 5mm, the distance between adjacent through holes is 2cm, the diameter of the inner cylinder is 2cm, and the width of the single-sided wing plate is 4cm, that is, the total width of the measuring water column is 16cm. The measuring device is 5cm above the channel.

Data observation: When the water flow exceeds the water column, it enters the water accumulation area between the inner and outer cylinders through the water inlet hole 5 on the outer cylinder of the water column. The water depth in the measuring cylinder measured by the high-precision water level gauge is 0.2469m, and the shrinkage ratio under this water depth is:

Flow calculation: Input the measured water depth data h in the water column, the structural parameters of the channel cross-section, the throat width B _c of the measuring tank and the corresponding channel bottom slope i into the software, and the formula in the software automatically calculates the overcurrent flow in the channel . The flow calculation formula is:

The actual flow through the trough is 0.03007m ³ /s measured by the right-angled triangle water weir in the prior art.

The relative error measured by the device of the present invention is:

The relative error is less than 5%, which meets the requirements of current measurement accuracy.

Claims (6)

1. A U-shaped channel flow measuring device is characterized by comprising a measuring cylinder, wherein a cylinder is arranged in the measuring cylinder, and the cylinder is fixedly connected with the measuring cylinder through a connecting body; a plurality of through holes are formed in the outer wall of the measuring cylinder along the axial direction, the through holes are located in the same radial direction, and a water accumulation area is formed between the cylinder body and the inner wall of the measuring cylinder; a first plate and a second plate are axially arranged on the outer wall of the measuring cylinder along the measuring cylinder, the first plate and the second plate are positioned on two sides of the same radial direction, and the radial direction where the plurality of through holes are positioned is perpendicular to the radial direction where the first plate and the second plate are positioned;

the cylinder comprises an inner cylinder and a fixed rod, the inner cylinder is connected with the measuring cylinder through a connecting piece, and the connecting piece is positioned at the end parts of the cylinder and the measuring cylinder;

the measuring device also comprises a water level measuring sensor;

the measuring device further comprises a mounting device, the mounting device comprises two mounting rods and two mounting seats, one end of each mounting rod is provided with a mounting groove, the mounting seats are used for mounting the other ends of the mounting rods, and the mounting grooves are used for mounting the first mounting plate or the second mounting plate.

2. The U-channel flow measuring device of claim 1 wherein a spring is attached between one end of the plate and one mounting bar and a spring is attached between the plate and the other mounting bar.

3. A U-shaped channel flow measuring method is characterized by comprising the following steps: calculating the flow of the U-shaped channel by using the formula (1):

the measuring device of claim 1, wherein the water depth h of the water accumulation area in the channel and the throat width B corresponding to the water depth h are measured_c，B_cB is the channel width corresponding to the water depth h in the ponding area, and m; d is the sum of the outer diameter of the measuring cylinder and the widths of the two side plates I and the two side plates II, and m;

calculating the flow of the U-shaped channel by using the formula (1):

in formula (1):

q is the flow rate;

h is the water depth m in the ponding area;

ε -shrinkage ratio;

i-channel bottom slope;

g-acceleration of gravity, m/s²；

p，α₁，α₂，α₃Are parameters.

4. The U-channel flow measurement method of claim 3, wherein 1/500 ≦ i ≦ 1/5000.

5. The U-channel flow measurement method of claim 3 wherein p-0.3184, α₁＝1.44235，α₂＝-0.00182，α₃＝0.0145。

6. The U-channel flow measurement method of claim 3, wherein epsilon ranges from 0.41 to 0.67.

Images