variablenozzle

Variablenozzle, also known as a variable nozzle, is a device in which the effective outlet area can be changed during operation to control the flow and characteristics of a fluid. By adjusting the throat or exit area, operators can influence pressure, velocity, spray angle, and mass flow.

Most variablenozzle use some movable element—such as a sliding sleeve, a pintle, or petals—that alters the flow passage. Actuation can be mechanical, hydraulic, pneumatic, or electrical, often controlled by a feedback system to maintain a target performance under changing conditions.

Applications include propulsion systems, where a variable nozzle improves efficiency across speed regimes; spray technology and coatings, where spray pattern and flow rate can be tuned; and process industries where precise metering and atomization are required.

In propulsion, variable nozzles may adjust area ratio in turbojets or turbofans and in rocket engines for optimized thrust and specific impulse. In sprays, they enable adjustments to spray cone angle, droplet size, and coverage without replacing nozzles.

Design considerations encompass mechanical reliability, sealing, wear, response time, control strategy, and operating range. There is a trade-off between performance benefits and added complexity and maintenance costs. Advantages include improved efficiency, flexibility, throttleability, and reduced emissions; limitations include increased weight, cost, and potential failure modes, as well as added maintenance requirements.

See also: variable geometry nozzle, pintle nozzle, convergent-divergent nozzle.