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1. Parshall flume 1: Introduction
Parshall flume, also known as Bab flume, is an auxiliary device for measuring open channel flow. The prototype is a Venturi water tank, and the latter experiment was conducted by VM. Cone in Colorado, USA in 1915. In 1922, F.L. Marshall made a fundamental change to this and created the now widely used Bachel groove. Subsequent hydraulic experiments were repeated multiple times, resulting in various measuring tanks ranging in size from 1 inch to 50 inches. The name Bacher Trough was given by the American Civil Society in 1929. Afterwards, many countries such as the United Kingdom, Switzerland, Italy, India, Argentina, etc. also proposed various types of design schemes for Venturi water tanks and conducted experiments, but the Bachel tank is still the most popular tank in Venturi water tanks.
2. The principle of open channel flowmeter and selection of weir channel - Tangshan Dafanghui Instrument
The open channel flowmeter adopts the principle of "liquid level method", which measures the liquid level in the standard water weir channel and calculates the flow value by combining the formula.
. The following explains the principles, types of weirs, and selection points:1. Working principle of open channel flowmeter. An open channel flowmeter consists of three parts: a converter, a liquid level sensor, and a standard water weirs. Liquid level measurement: The liquid level sensor monitors the liquid level height in the weirs in real time and converts the liquid level signal into an electrical signal. Flow calculation: The converter automatically calculates instantaneous flow and cumulative flow based on the flow formula corresponding to the liquid level height and weir type. Output function: Supports multiple signal outputs (such as 4-20mA, RS485, etc.) for remote monitoring and data integration.
II. Types and Characteristics of Standard Weir Troughs. The open channel flowmeter is equipped with 11 types of standard weir grooves, suitable for different flow ranges and scenarios: thin-walled weirs, 90 ° triangular thin-walled weirs: suitable for small flow rates (0.1-10 L/s), simple structure, and easy installation.
. Rectangular thin-walled weir: with a wide flow range (1-1000 L/s), it requires high water flow conditions. Trapezoidal thin-walled weir: Combining the advantages of rectangular and triangular weirs, suitable for medium flow rates (10-5000 L/s). Equal width thin-walled weir: stable flow measurement, but high installation accuracy is required. Wide top weir type rectangular wide top weir: suitable for high flow rates (0.1-10 m3/s), with a sturdy structure and strong impact resistance. Circular edge wide top weir: reduces water flow resistance, improves measurement accuracy, and is suitable for water flows containing impurities. Parshall Flume, a special weir channel, has a wide flow range (0.01-100 m3/s) and strong adaptability to water flow conditions, making it one of the most widely used weir channels. No throat groove: With a simple structure, it is suitable for low flow velocity and large cross-section channels. P-B slot: Combining the characteristics of Pasher slot and throat free slot, suitable for medium flow rates. Triangular section weir: suitable for irregular cross-section channels, flow calculation needs to be combined with liquid level and cross-section shape. Pingtan V-shaped weir: suitable for water flow containing sediment, with strong ant