Part I. Experimental investigation of an arc-heated supersonic free jet. Part II. Analysis of one-dimensional isentropic flow for partially ionized argon

摘要

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.I. Experimental Investigation of an Arc-Heated Supersonic Free Jet.An experimental investigation of the flow field of a highly ionized supersonic free jet has been carried out in a continuous-flow test facility. Measurements of impact pressure, mass flux, total enthalpy and stagnation point heat transfer profile were made in this flow field with two water cooled probes.Argon gas, at a flowrate of 0.5 gm/sec, was heated in a magneto-plasma-dynamic arc heater without an external magnetic field operating from between 200 amp and 40 volts to 1000 amp and 25 volts. The total pressure ranged from between 20 and 35 mm Hg, at constant flowrate, and the atom-ion number density was approximately [...] cm[...] at the exit plane. The average total enthalpy calculated from a heat balance ranged from between about 5,000 to 10,000 BTU/[...], while the probe measurements showed that the peak total enthalpy on the jet centerline near the exit plane was about three times the average total enthalpy.The impact and mass flux measurements showed that the flow was hypersonic, source-like, chemically frozen, and in other details very much like the under-expanded free jet flow of a perfect gas. By combining these measurements with the total enthalpy measurements it was shown that the fraction of the total energy contained in ionization was about 0.6 which is quite close to the equilibrium stagnation value. For equilibrium stagnation conditions, the total temperature ranges from between 12,000° to 20,000°K. The species mass fraction ranges from 0.2 for the atoms and 0.8 for the singly-ionized ions, to 0.8 for the singly-ionized ions and 0.2 for doubly-ionized ions.Examination of the electron energy equation showed that within a few diameters from the exit plane the electrons become energetically isolated from the ions and the electron heat conduction term dominates.A preliminary attempt to correlate the stagnation point heat transfer measurements along the axis shows that the electron temperature (TE [...] TI in general) plays an important role.II. Analysis of One-Dimensional Isentropic Flow for Partially Ionized Argon.One-dimensional isentropic-flow variables of partially ionized argon have been calculated by coupling the isentropic flow equations with the partition-function method of deriving equilibrium thermodynamic properties. Tabulated gas properties and flow variables are presented for stagnation conditions of 0.1, 0.5, 1.0, 2.0, and 3.0 atm pressure and temperatures from 6,000 to 14,000°K in 1,000°K increments. The gas properties computed for this flow process include the sound speed, entropy, enthalpy, electron concentration, ionization fraction, electrical conductivity and static-to-stagnation ratios of temperature, pressure, and density. Flow variables include velocity, mass flux, area ratio, and Reynolds number per centimeter. Compared to results obtainable from perfect gas relationships (neglecting excitation and ionization), the results indicate that electronic excitation, and especially ionization effects, significantly alter the flow variables, particularly at the lower stagnation pressures and higher temperatures considered. However, with the exception of the effect of one excited state (the first excited state of the ion) on the equilibrium-composition equation, the thermodynamic properties calculated by neglecting excitation yielded results which were within 1% of those predicted by including excitation.