A microwave plasma jet based on a coaxial cavity can be generated in atmosphere and vacuum environments. It is shown that with argon gas and a power range of 53–60W, cavity efficiency ranges from 54% to 68%. The electron density distribution and the microwave return loss of the confined plasma jet adjacent to a metal object and their dependency on argon mass flow rate and power have been studied by applying emission/Langmuir probe and spatial reflected wave diagnostic equipments in a low scatter vacuum environment. The results show that the electron density ranges from 8.8×1014to7.53×1016∕m3, and the electron density on the centerline of the jet decreases exponentially from the nozzle exit plane, but its distribution off the centerline is in an upheaved curve. Increasing mass flow rate at constant power and increasing power at constant mass flow rate increase electron density mildly. From typical measurements of microwave return loss, it is noted that the plasma jet attenuates microwaves in a 6to8GHz range.

In order to analyze the characteristic of the self-excited cavitation oscillation occurred in an inducer-centrifugal pump-piping system, a novel cavitation dynamic model is present to simulate the dynamic characteristic to capture the limit cycles, the characteristics of inlet pressure and the flow rate. The results of numerical experiments indicate this cavitation dynamic model is very suitable to simulate the characteristics of the self-excited cavitation oscillation; the calculated limit cycle of flow rate vs. inlet pressure is consistent with experiment; the cavitation pocket decreases as the flow rate and inlet pressure rise.

Electromagnetic waves will be attenuation when through plasma because of absorption and refraction efferts. Active application of plasma attenuation effect has good application prospect, such as aircraft stealth. But at the same time, the attenuation effect oneself will also bring some problems. For exzample, as the power system of the spacecraft, electric thruster plasma jet is possiblly to cause some problem on the communication between spacecraft and ground stations [1] .

No abstract