Temperature&Pressure integrated Turbine flow meter

A Turbine Flow Meter with Temperature and Presure Compensation is a volumetric measuring turbine type.

The flowing fluid engages the rotor causing it to rotate at an angular velocity proportional to the fluid flow rate.

The angular velocity of the rotor results in the generation of an electrical signal (AC sine wave type) in the pickup. The sum of the pulsing electrical signal is directly related to the total flow.

Temperature and pressure compensation gas Turbine Flowmeter is a kind of velocity flow measurement instrument, in which the turbine speed is the measurement of flow, through mechanical transmission, magnetoelectric conversion, form an electrical pulse signal proportional to the flow, making a significant contribution to industrial production and measurement. 

Under certain working conditions, when using a gas turbine flowmeter to measure flow, if the user does not consider temperature and pressure compensation, the results will often be very different from the correct results, and it is impossible to conduct trade settlement or process assessment. 

Liquid volume is almost unaffected by pressure, only by temperature, and when the temperature range is very small, liquid volume change is very small. However, the fluid characteristics of the gas are greatly changed by the influence of pressure and temperature. In fluid measurement, gas flow temperature and pressure compensation are of great significance.

Most gases can be approximated as ideal gases, and their density can be expressed by a modified ideal gas equation of state. Some gases, such as water vapor, are different from ideal gases, and their density cannot be expressed simply by the ideal gas equation of state. There are dry and wet gases.As for wet gases, their density is related to humidity in addition to temperature and pressure. In recent years, the continuous emergence of microcomputer instruments makes it easy to measure the temperature and pressure compensation of gas flow, improving the measurement accuracy.

I. Flow measurement principle of gas turbine flowmeter
1. The temperature and pressure compensation gas turbine flowmeter is made according to the Karman vortex street principle, that is, a nonlinear object (i.e. a vortex generator) is inserted into a fluid-filled pipeline perpendicular to the flow direction of the fluid.When the flow velocity of the fluid reaches a certain value, two columns of regular vortices will be alternately released on both sides of the vortex generator of the temperature and pressure compensation gas turbine flowmeter. The relationship between the frequency f of a single row of vortices and the average velocity v of the measured fluid is as follows: f= St (V1/d) ,  in the fomula , f -- frequency of a single row of vortices, Hz;d --maximum width of the incident fluid side of the vortex generator, m; V1 -- average velocity of both sides of the vortex generator, m/s; St -- Strauhal number, dimensionless.
2. When Reynolds number Re is in the range of 2×104 to 7×106, St value is constant after the vortex generator and pipe diameter are confirmed. It can be seen that the frequency of a single column vortex is directly proportional to the volume flow of the fluid. As long as the value of the vortex frequency f is detected by the sensor, the flow can be accurately confirmed.

Ⅱ. Compensation function of gas turbine flowmeter
For the measurement of gas mass flow, since it is easily affected by temperature and pressure, it deviates from the ideal working state, resulting in a large error in measurement results. Therefore, in order to improve accuracy, temperature and pressure sensors are added to this design,compensate for t measuring gas mass flow.

Ⅲ. Compensating method for gas turbine flowmeter measurement of different media
1. When measuring saturated steam,a single temperature compensation or pressure compensation is required. The density of saturated vapor has a fixed relationship with temperature or pressure (saturated vapor density table), knowing either of which can determine the density of saturated vapor.
2.When measuring superheated steam, the temperature and pressure must be compensated at the same time ; Steam is generally billed as mass flow rate. Because of a change in temperature or pressure, the density of  vapor changes, and the mass flow rate changes with it.
3. When measuring gas, the temperature and pressure must be compensated at the same time; gas is generally settled in standard condition volume flow. Because the volume flow, temperature or pressure of a gas changes, the flow will change with it.
4.When measuring liquids, pressure compensation is generally not required.When the pressure is below 5MPa, generally only consider the impact of temperature.Temperature compensation is required for accurate measurement. Measurement of certain hydrocarbons(such as crude oil) generally requires compensation for both temperature and pressure .