The Application & Working Principle of the Open Channel Ultrasonic Flow Meter
In practical application, even though there is a name called open channel ultrasonic flow meter, its essence is actually an ultrasonic level gauge. Only the head of the ultrasonic level gauge is designed with a matching algorithm formula of the Parshall tank. By setting the matching tank body and adding the height of the ultrasonic level gauge measured in real-time, the corresponding sectional area is calculated, and the corresponding flow rate is added to calculate the real-time flow value. In fact, the open channel ultrasonic flow meter has been used more and more widely and has been paid attention to.
Classifications of Open Channel Measurements
There are several major classifications of open channel measurements according to different principles. The following is an analysis of several methods of measuring flow according to the building flow measurement method.
1. Weir trough method
The Weir groove method is a relatively traditional water measuring equipment, mainly including thin-walled weir, broad crested weir, trapezoidal profile weir, triangular profile weir, flat weir, long throat groove, short throat groove, including Parshall groove, Suneli groove, and non-throat groove.
The basic principle of the weir slot method is to let the water flow pass through the constricted discharge section and control the water flow. The flow is calculated by using the stable water level discharge relationship when the water flows through the narrowest part of the discharge section because in this case, the flow will form a transition from slow flow to rapid flow, namely critical flow, so as to form a stable water level discharge relationship in front of the slot.
2. Stage discharge relation method
On some natural river sections, the measured results show that there is a stable stage-discharge relationship. The relationship between the upstream water level and the flow of some gates and culverts is also stable, so the flow can be measured directly by measuring the water level. The water level discharge relation method can be divided into the liquid level velocity equation method and the nozzle flow meter method.
Calculation method of liquid level and velocity: a method to measure the water level of the flowing pipe and channel to obtain the flow rate by using the function between the liquid level and the average velocity of the liquid under the natural flow of the non-full pipe or open channel free surface.
Nozzle flow meter method: an open nozzle is installed at the discharge outlet of the non-full pipe, and the water level upstream of the nozzle is measured to obtain the flow. One type of open nozzle is installed at the discharge outlet of a circular blind channel, and the downstream liquid level must be lower than the nozzle elevation to form free discharge.
The obvious advantages of the stage-discharge relation method are low cost, small resistance loss, and difficulty forming sediment, while the obvious disadvantages are low measurement accuracy, and its accuracy is greatly affected by roughness. In areas with large changes in roughness, its measurement accuracy will be further reduced.It can be seen from the above that there are also many branches of the open-channel ultrasonic flow meter, and the corresponding open channel ultrasonic flow meter is selected according to different site conditions. However, many customers generally select a range of 5 meters for the ultrasonic level meter that is matched on the site and select the corresponding tank model at the meter head. Through reasonable installation, the corresponding sewage flow can be measured.