Cooling-water leakage diagnosis using optical emission spectroscopy for a large-scale arc-heated facility

Abstract

A technique for optical emission spectroscopy is developed and deployed in the detection of cooling-water leakage in an arc-heated wind tunnel at China Academy of Aerospace Aerodynamics. The arc heater operates at temperatures of 5000–9000 K and pressures of 2–6 atm. Two mass-average enthalpy conditions, 18.7 MJ∕kg (test 1) and 16.4 MJ∕kg (test 2), are studied. From the spectral characteristics of the normal and leakage spectra, the 656.28-nm emission spectral line of atomic hydrogen (H656.28) and the 777.19-nm emission spectral line of atomic oxygen (O777.19) are selected for coolant-leakage detection in the arc heater. Given the emission intensity ratio of H656.28 and O777.19, detection limits for the mass flow of the leaking water are derived; for tests 1 and 2, they are 18.5–0.94 g∕s and 2.12–0.98 g∕s, corresponding to equilibrium temperatures ranging from 6000 to 8000 K and 5500 to 7500 K, respectively. This work demonstrates the feasibility and potential of the optical emission spectroscopy technology in high-enthalpy arc heater health diagnosis, especially in regard to the coolant leakage diagnosis.