How to calculate the coefficient of turbine flowmeter

How to calculate the coefficient of turbine flowmeter

Under normal circumstances, the flow equation of a turbine flowmeter can be divided into two types: practical flow equation and theoretical flow equation. The editor will give you a simple analysis.

Practical flow equation:Qv=f/K formula 1; In the equation qm=qv ρ, qv and qm respectively represent volumetric flow rates, m3/s， Quality flow, kg/s； F is the frequency of the output signal of the flowmeter, Hz; K is the instrument coefficient of the flowmeter, P/m3。

The coefficient of a turbine flowmeter can be divided into two segments, namely the linear segment and the nonlinear segment. The linear segment is about two-thirds of its working segment, and its characteristics are related to the sensor structure size and fluid viscosity. In the nonlinear segment, the characteristics are greatly affected by bearing friction and fluid viscous resistance. When the flow rate is below the lower limit of the sensor flow rate, the instrument coefficient changes rapidly with the flow rate. The pressure loss is approximately proportional to the square of the flow rate. When the traffic exceeds the upper limit, attention should be paid to preventing cavitation. Structurally similarThe shape of the TUF characteristic curve is similar, with only differences in the level of systematic error.

The characteristic curve of the turbine flowmeter is calibrated by a flow verification device, which completely disregards the internal fluid mechanism of the sensor. The sensor is treated as a black box, and its conversion coefficient is determined based on the input (flow rate) and output (frequency pulse signal), making it convenient for practical applications. However, it should be noted that this conversion coefficient (instrument coefficient) is conditional, and its verification condition is a reference condition. If it deviates from this condition coefficient during use, it will change depending on the sensor type, pipeline installation conditions, and fluid properties parameters.

Installation and use of turbine flowmeter

To fully utilize the characteristics of turbine flow meters, it is necessary to pay full attention to the installation and use of flow meters. Below is a brief discussion on this issue

(1) Tested medium

The liquid measured by the turbine flowmeter is generally of low viscosity (generally less than 15 × 10)^－6m²／s)、 Low corrosive liquids. Although turbine flow meters are currently used for measuring various media, careful consideration and corresponding measures still need to be taken for measuring high-temperature, high viscosity, and strongly corrosive media. When the viscosity v of the medium is greater than 15 × 10^－6m²／At s, the instrument coefficient of the flowmeter must be calibrated with real liquid, otherwise significant errors may occur

Gas liquid two-phase flow, gas-solid two-phase flow, and rich solid two-phase flow cannot be measured using a turbine flowmeter

(2) Installation piping requirements

The installation of flow meters has a significant impact on their measurement accuracy