Arc heater is an important ground test facility to study the aerothermodynamics and thermal protection system for hypersonic vehicles. The arc-heated facility generates copper into the high-temperature plasma flow and contaminate the test flow owing to electrode discharge. This paper developed an in-situ quantitative emission spectroscopy diagnostic system for flow parameter measurement, and the system was utilized to measure mole fraction of copper concentration for a 10 MW high enthalpy segmented constrictor-type arc heater. Based on the selected copper line, measurements were conducted in the early ignition stage and steady-operation stage, and electrode erosions were analyzed for ring electrode and tabular electrode. The results show that there exists high degree electrode-erosion in the early ignition stage, and the peak values of copper concentration for tabular electrode were higher than the values for ring electrode. In the steady operation stage, the copper concentration decreased quickly and maintained a value of below 10-6 by mole for ring electrode, while electrode erosions for tabular electrode were obvious with high and unsteady variation of copper concentration. Meanwhile, the copper concentrations were proportional to the operational current and criteria for electrode degradation were established by the copper concentration measurements to ensure the safety operation for the arc heater. This study provides a mature non-intrusive diagnostic technique to study the electrode erosion and copper contamination for arc-heated facilities, and the developed spectra diagnostic system show advantages for high temperature flow diagnostics as a regular test method.
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