Venturiinjektor

A venturiinjektor, or venturi injector, is a passive device that uses the Venturi effect to entrain and inject a secondary fluid into a main fluid stream without moving parts or external power. It is installed in a piping system and relies on the energy of the main flow to draw in the secondary fluid through a dedicated inlet.

Principle: The main fluid is forced through a converging-diverging nozzle (the Venturi throat). As the flow speeds up in the constricted section, its static pressure drops. This pressure drop creates suction that draws the secondary fluid into the injector through an inlet connected to a reservoir. The entrained fluid mixes with the main flow downstream, and the final concentration depends on the flow rate, pressures, viscosities, and the geometry of the injector.

Construction and operation: Venturi injectors are typically made of materials compatible with the fluids (such as stainless steel, plastic, or reinforced composites). They require a sufficient upstream pressure to produce the necessary suction; the ratio of entrained to main flow is determined by design and operating conditions. Proper installation often includes anti-siphon features or check valves to prevent backflow.

Applications: Commonly used in agriculture for fertigation (injection of fertilizers into irrigation water) and chemical dosing, in water treatment for adding coagulants or disinfectants, and in some industrial processes for low-cost, electricity-free dosing. They have also been used in older fuel systems (carburetors) to mix fuel and air, though modern engines use different methods.

Advantages and limitations: Advantages include no moving parts, low maintenance, and simple installation. Limitations include variable dosing with changes in flow or pressure, sensitivity to viscosity, potential for clogging, and the need for proper sizing and backflow prevention to ensure safe operation.