A turbine flowmeter is a speed-type instrument. The change of density will increase or decrease the rotating torque acting on the impeller proportionally, thereby affecting the displayed volume flow.
In the case of measuring liquid, because the density of the liquid changes little, and the bearing friction torque is as small as possible in the design, the influence of density can generally be ignored.
In the case of measuring gas, since the density of the gas is one-thousandth of the density of the liquid under normal pressure, to keep the gas with the same torque effect as the liquid, the flow rate must be increased by more than 30 times. Similarly, the speed of the impeller must also increase sharply, which directly affects the service life of the sensor.
For this reason, the design of the gas flow sensor must reduce the blade inclination angle to reduce the impeller speed.
At the same time, reduce the bearing friction torque as much as possible. Once the temperature, pressure, or density of the fluid to be measured changes significantly, the flow coefficient of the sensor should be corrected.