Air Amplifier

Overview

An air amplifier is a passive, movingparts-free device that multiplies pressure using the Coanda effect, the same principle that powers air knives and vacuum ejectors. A supply line at 2–3 bar feeds a Nozzle Ring containing 6–12 precision Coanda nozzles. These nozzles accelerate the supply air and aim the jets into a central Amplifier Chamber. When the jets collide and merge, they create backpressure and resistance, which is channeled to the Outlet Port Assembly. With proper Gap Adjustment Valve tuning, the outlet pressure can reach 8–10 bar from a 1–2 bar supply, a 5–10× amplification.

Amplifiers are prized for low-pressure systems and specialty applications: proportional control loops, pilot-pressure generation in remote plants, emergency inflate of elastic seals, and regenerative braking in rail systems.

How it works

Regulated supply air (say 2 bar) enters the Amplifier Body and is distributed to the Nozzle Ring. Each Coanda nozzle has a throat (0.3–0.8 mm) that accelerates the air. As the air exits the nozzle, it follows the Coanda surface, a concave curved wall, due to a low-pressure region forming on the curved side. The jets from all nozzles radiate inward toward the Amplifier Chamber.

Inside the Amplifier Chamber, the high-velocity jets collide. At the collision point, kinetic energy converts to static pressure. This high-pressure region is connected to the Outlet Port Assembly, which supplies the load. The back-pressure created by the load restricts the outlet flow, raising the stagnation pressure further.

The Suction Port taps into the low-pressure region surrounding the jet core, the wake of the jets. This suction can be used as a low-flow vacuum source or as a pilot signal. The Gap Adjustment Valve needle valve controls the spacing between the nozzle ring and the central outlet. A smaller gap (narrower) increases pressure by creating tighter convergence; a larger gap reduces it. Technicians adjust this needle to find the sweet spot for their load.

Efficiency and behavior

Amplifier efficiency (output power / input power) is typically 35–50%, much lower than a well-sized pump but acceptable for applications where complexity and cost are prohibitive. The amplifier exhibits flow-pressure coupling: if the outlet load increases (valve closes), the outlet pressure rises sharply. If the load is removed, pressure drops and the amplifier operates in "free-flow" mode, supplying high flow at lower pressure.

Response is fast (< 100 ms) because there are no moving parts; it is purely a fluid-mechanics device. Stability is inherent: the back-pressure automatically adjusts to match the demand.

Typical applications

• Proportional pilot supply: A plant with only 1 bar available can generate 4–6 bar for proportional valve pilots.
• Remote emergency inflate: A low-pressure main line feeds a remote device; an amplifier nearby generates high pressure for sudden seal inflation without adding a compressor branch.
• Braking circuits: Regenerative systems for pneumatic brakes use amplifiers to convert low-pressure exhaust back into usable work.

The main limitation is that amplifiers are best suited to low-flow (< 50 L/min) applications. For high-flow needs, a conventional high-pressure compressor is more efficient.