The metal tube rotor flowmeter is a typical instrument for flow measurement based on rotor dynamic balance and cone geometry. Its core principle can be summarized as follows: when the fluid flows through a vertically installed cone tube from bottom to top, it generates an upward impact force on the internal rotor (float). The rotor reaches dynamic balance under the combined action of gravity, buoyancy, and fluid impact force, and its suspension height corresponds linearly to the flow rate. This process converts the flow signal into a mechanical or electrical signal that can be visually read through the synergistic effect of rotor displacement and cone shaped lines.

Rotor dynamic balance mechanism

The motion state of the rotor is determined by three forces:

Fluid impact force: It increases with the increase of flow velocity and is the main driving force for the rotor to rise;

Buoyancy: Related to fluid density, it assists in adjusting the equilibrium position when the medium density changes;

Gravity: The weight of the rotor itself provides a downward stabilizing force.

When the flow rate increases, the increase in flow velocity leads to an increase in impact force. The rotor rises along the axis of the cone tube, and the annular flow area expands accordingly. The flow velocity gradually decreases until the three forces are re balanced; When the traffic decreases, it moves in the opposite direction. This dynamic adjustment process transmits rotor displacement to external indicators through magnetic coupling technology, achieving non-contact signal conversion, avoiding mechanical wear and improving reliability.

Design Logic of Cone shaped Lines

The shape of the cone tube (usually an exponential curve or linear taper) is the key to flow linearization:

Small caliber instruments often use linear taper, with a simple structure and moderate range ratio;

Index taper is often used for large caliber instruments, and by optimizing the cone angle distribution, the rotor displacement and flow rate are strictly linearly related, simplifying the calibration process.

The smaller diameter at the lower end of the cone tube can increase the flow velocity at low flow rates and enhance the sensitivity of the rotor response; Expanding the upper diameter reduces pressure loss at high flow rates. In addition, the inner wall of the cone tube is designed with guide rods or guide ribs to ensure stable movement of the rotor, avoid tilting and jamming, and reduce the impact of fluid friction on measurement accuracy. For corrosive media, the cone tube and rotor are made of Hastelloy or lined with PTFE material; The addition of insulation layer under high temperature conditions reflects the adaptability of geometric design to complex working conditions.