Pressure fluctuations analysis on the powder fluidization performance at different pressure

Abstract

Powder propellant feeding system is the key part of powder engine, and the powder fluidization process is quite complex due to the comprehensive effects of intake type, piston and compressible dense gas-solid flow in tank. In order to explore the regimes and fluidization characteristics at high pressure, in this paper, visualization technique with pressure transducer are applied, and the pressure signals have been analyzed by using standard deviation and wavelet transform methods. It is found that in powder tank the fluidization regime will be changed with the increase of pressure: from partial powder fluctuation at low pressure (0.4 MPa) to steady gas-solid interface at high pressure (2.5 MPa), and the regime phenomenon can be explained roughly by standard deviation analysis of pressure signals. Meanwhile, the flow representations of pressure sub-signals were redistricted through wavelet energy method based on ten-level decomposition: the approximation sub-signal a10 (0–4.88 Hz) represents the fluidized gas intake, sub-signals d8–d10 (19.53–39.0625 Hz) represent the powder flow structure changing, gas-solid interaction is represented by d6–d7(39.0625–156.25.Hz), and sub-signals d1–d5 (156.25–5000 Hz) can be used for gas turbulence flow representation. Where gas turbulence and powder fluctuation were determined as the main contributions to pressure fluctuation in the tank. Otherwise, the wavelet energies of sub-signals except for approximation decrease with pressure increase, but there exist large differences for that with the increase of particle mean diameter with different leading force, and the easier entrainment for different size powder, the slighter effects of gas turbulence and gas-solid interaction.