What are three-rotor engines, and how do they work?

　　The three-rotor meter measures fluid flow based on the throttling principle. To maintain a constant differential pressure across the rotor by adjusting the fluid's flow area, it’s also known as a variable-flow-area differential-pressure flowmeter—or simply the three-rotor flowmeter. Now, let’s take a closer look at what exactly a three-rotor is and how it works.

　　The three-rotor is a variable-area flowmeter that operates by utilizing the principle of a circular-section float freely rising and falling within a vertically tapered tube, which widens from bottom to top. The float’s weight is counteracted by fluid dynamics acting upon its circular cross-section, allowing it to move up and down inside the conical tube. As the float oscillates due to changes in flow velocity and buoyant force, it eventually reaches an equilibrium with its own weight. This movement is then transmitted via magnetic coupling to the dial, which displays the corresponding flow rate.

　　The three-rotor flowmeter operates on the principle of variable area. As fluid flows in, the float inside the tapered tube rises, increasing the cross-sectional area of the fluid passage. The greater the flow rate, the higher the float climbs—its height directly correlates with the flow volume. When measuring liquids, the float is influenced by both the buoyant force exerted by the liquid and the difference in fluid velocity. However, when measuring gases, the buoyant force becomes negligible, and the float responds solely to the velocity differential.

　　The three-rotor flowmeter consists of two main components: one is a tapered tube that gradually widens from bottom to top, and the other is a rotor housed inside the tapered tube, free to move up and down along the tube's central axis. When measuring fluid flow, the fluid enters the tapered tube from its lower end. As the fluid flows, it collides with the rotor, exerting a force on it—this force varies depending on the flow rate. If the flow rate is sufficiently high, the resulting force lifts the rotor, causing it to rise upward.

　　Additionally, the fluid being measured flows through the annular cross-section between the rotor and the conical tube wall. At this point, three forces act on the rotor: the dynamic pressure exerted by the fluid, the buoyant force of the rotor in the fluid, and the rotor's own gravitational force. When the rotor is installed vertically, its center of gravity aligns perfectly with the central axis of the conical tube, causing all three forces acting on the rotor to point parallel to this axis. When these three forces reach equilibrium, the rotor smoothly floats at a specific position within the conical tube.

　　Another type of three-rotor design features rotors housed within a tapered tube, allowing them to move freely up and down along the tube's central axis. When measuring fluid flow, the fluid being tested enters from the bottom end of the tapered tube, striking the rotors and exerting a force on them. As the incoming flow velocity increases, the rotors shift either upward or downward, causing the cross-sectional area of the flow path at their current position to change accordingly. For this three-rotor system, the rotor’s position inside the tapered tube directly correlates with the magnitude of the fluid flow passing through the tube.

　　That concludes our introduction to what a three-rotor is and how it works. If you’d like to learn more, feel free to reach out to us anytime! Our company boasts years of experience and warmly welcomes you to join us.