fixednozzle

A fixed nozzle is a nozzle whose geometry is fixed and does not change during operation. In fixed-nozzle configurations, the throat and exit dimensions are set during manufacture and are not adjustable in service. This contrasts with variable-geometry nozzles, which can change cross-sectional area or expansion ratio to adapt to different operating conditions.

Fixed nozzles are used in a variety of applications where stable, repeatable performance is required. Common roles include industrial spraying and atomization, cooling and cleaning jets, and certain propulsion or combustion systems where a constant jet characteristics are desirable. In rocket and jet propulsion contexts, fixed nozzles provide a specific expansion ratio and exit velocity for designated operating conditions and are often paired with gimbaled mounts for steering rather than geometric adjustment.

Design and performance of a fixed nozzle are governed by the upstream pressure, the nozzle’s area ratio (the ratio of exit area to throat area), and the fluid properties. For compressible flows, an ideal nozzle accelerates the fluid according to isentropic relations up to its throat, with the actual performance influenced by friction, heat transfer, and back-pressure effects. Because the geometry cannot adapt, the nozzle delivers peak efficiency near its design point but may become suboptimal under off-design pressures or temperatures, leading to reduced thrust or increased energy losses.

Advantages of fixed nozzles include simplicity, ruggedness, low cost, and reliable repeatability. Limitations involve limited adaptability to changing conditions and potential efficiency loss outside the intended operating range. Suitable materials and precision machining are important to maintain consistent output and prevent wear-related performance drift.