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1. Detailed explanation of the technical principle of Doppler ultrasonic flowmeter
The technical principle of Doppler ultrasonic flowmeter is mainly based on the Doppler effect and velocity area method for flow measurement. By measuring the ultrasonic frequency shift and water level parameters reflected by impurities in the fluid, combined with fluid mechanics formulas, flow calculation is achieved. The following is a detailed analysis of the specific technical principles:
1. Core flow measurement method: Velocity area method Doppler ultrasonic flowmeter uses velocity area method to measure flow, and its core formula is: Q=V × SQ: instantaneous flow rate V: fluid velocity (measured by Doppler effect) S: overflow area (calculated from water level) Technical advantages: not limited by channel section shape: suitable for rough sections of any shape such as rectangle, circle, trapezoid, etc., breaking the dependence of conventional flow meters on regular sections. Multi parameter measurement: It can synchronously obtain flow velocity, water level, water temperature, flow area, instantaneous flow rate, and cumulative flow rate. Figure 1: The velocity area method calculates flow rate by multiplying the flow velocity with the flow area. 2. Flow velocity measurement principle: Doppler effect. Ultrasonic emission and reflection: The probe emits a beam of ultrasonic waves obliquely upwards. When the ultrasonic waves propagate in the fluid, they will reflect when encountering impurities such as bubbles and particles (consistent with the water flow velocity). The reflected wave generates a Doppler frequency shift Δ f due to fluid motion, and the magnitude of the frequency shift is proportional to the flow velocity.
III. Flow velocity distribution optimization: Spectral analysis algorithm. Characteristics of water flow velocity distribution: Water flow velocity follows a normal distribution, with the highest and lowest flow velocities accounting for a very small proportion, and the middle flow velocity segment dominating. Habitual flow meters are prone to deviation due to uneven flow velocity distribution. The function of spectrum analysis algorithm is to integrate and process the flow velocity distribution curve, extract the unit that best represents the flow velocity of the water body, and eliminate local flow velocity interference. Accuracy improvement: The flow velocity measurement accuracy reaches 1% ± 1cm/s, significantly better than conventional methods. 4. Calculation of Water Level and Overflow Area: Pressure type Water Level Gauge: Convert the water level height (H) by measuring the pressure of the water body. Automatic calculation of overcurrent area: The controller has built-in channel parameters (such as cross-sectional shape and size), which automatically calculate the overcurrent area S based on the water level H. Formula: S=f (H) (where f is the geometric function of the channel cross-section). High precision: Spectral analysis algorithm optimizes flow velocity measurement with an accuracy of 1% ± 1cm/s. Multifunctionality: Integrated measurement of multiple parameters such as flow rate, water level, temper
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