An inducer is the axial inlet portion of a

centrifugal pump Centrifugal pumps are used to transport fluids by the Energy transformation, conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. They are ...

rotor, the function of which is to raise the inlet

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple ani ...

by an amount sufficient to prevent significant

cavitation Cavitation in fluid mechanics and engineering normally is the phenomenon in which the static pressure of a liquid reduces to below the liquid's vapor pressure, leading to the formation of small vapor-filled cavities in the liquid. When sub ...

in the following pump stage. It is used in applications in which the inlet

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

of a pump is close to the

vapor pressure Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indicat ...

of the pumped liquid. Inducers are frequently included in design of

turbopump A turbopump is a fluid pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The most co ...

s for liquid propellant

rocket engines A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed Jet (fluid), jet of high-temperature gas produced by the combustion of rocket propellants stor ...

, although they are used in other applications which require high suction performance. It does not increase NPSHa but decreases NPSHr for Pump. Inducer_tip_vortex_cavitation

Use in rocketry

In order to achieve high

delta-v Delta-''v'' (also known as "change in velocity"), symbolized as and pronounced , as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or l ...

, the structural mass of a

launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...

should be as low as possible. Liquid fuel tanks can be constructed lighter if the pressure within those tanks is kept low. Typically, for pump-fed rocket engines, the propellant tank pressures (and masses) are 1/10 to 1/40 of those in a pressure-fed rocket. The structural weight constraint also makes the rotating speed of the

rotor as high as possible. For example, the rotating speed of the oxygen turbopump of the Japanese

LE-7 The LE-7 and its succeeding upgrade model the LE-7A are staged combustion cycle LH/LOX liquid rocket engines produced in Japan for the H-II series of launch vehicles. Design and production work was all done domestically in Japan, the first ma ...

rocket engine is 18300rpm. These two factors above combine to make the pump impeller very susceptible to cavitation. If cavitation occurs in the impeller, the performance of the pump will be severely degraded and the pump itself may be damaged.

References

Pumps Rocket engines {{fluiddynamics-stub