AN EXPERIMENTAL STUDY OF VORTEX FLOW FOR APPLICATION TO GAS-PHASE FISSION HEATING

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Abstract
An experimental investigation into the gas dynamics of a jet-driven vortex tube for application of a cavity nuclear reactor to rocket propulsion has shown that viscous retardation of the vortex motion is severe, because of a high level of turbulence near the periphery. Based on the experience gained in this study, it is estimated that the achievement of vortex strengths sufficient for practical application will require the use of small diameter tubes with appreciable expenditure of power for recirculation of the gas. The effect of the high degree of turbulence on the separation process near the periphery remains to be determined. The independent variables which were found to influence the vortex strength significantly for a given gas and temperature condition are the tube diameter, the mass flow rate per unit tube length, the injection velocity, and the wall pressure. Estimates of the degree of turbulence in vortex flow have been made from data on the variation in tangential velocity with radius. Virtual (total) viscosities near the periphery ranged from 30 to 700 times the molecular viscosity for tangential Reynolds numbers of from 4 x 10/sup 4/ to 2 x l0/sup 6/. Measurements of the position of the mole- fraction peakmore » for separation of helium and a heavy vapor agreed with the theory for laminar flow. This suggests that near the center of the vortex tube where the peak developed the radial density gradient was sufficiently strong to suppress turbulence. It is concluded that the vortex reactor concept appears promising for application to nuclear rocket propulsion provided a satisfactory method can be devised for recirculation of the large excess mass flow required to maintain the vortex strength, and if turbulence does not appreciably limit the separation process. A separation experiment at elevated temperature appears to be the next logical step in the research program. (auth) « less

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