Grants and Contracts Details
The proposed work is intended to enhance plasma diagnostic capabilities of the HYMETS arc-jet facility at NASA Langley with optical methods. In particular, monitoring of material properties during arc-jet testing and characterization of the facility flow are targeted. One of the most important material properties during high enthalpy testing is the spectral surface emissivity. Accurate knowledge of spectral surface emissivity is of significant importance to increase accuracy in temperature determination. The emissivity depends on the material itself and may change with the surface condition, its temperature, and the direction into which the radiation is emitted. During arc-jet testing, these material properties often change, therefore in-situ monitoring of surface emissivity becomes important. Recently, a method has been developed to determine emissivity from emission spectra of the glowing sample surface during the test through iterative fitting with blackbody radiation. Initial tests showed promising results, however, the theoretical basis needs further investigation to establish the limits of applicability of this method. Within the proposed project, this assessment will be made based on theoretical simulation of example spectra which will undergo the same analysis process as measured ones. The results will be compared with existing data and additional measurements to be performed at UK and Langley facilities. Support to measurement campaigns at Langley will be provided as needed. Beyond material properties, a thorough understanding of the facility flow itself is of significant importance for defining and predicting test conditions in this facility. Optical plasma diagnostics such as emission spectroscopy of free stream and shock/post-shock region in front of probes will be used to characterize temperature distributions in these flows as a means of determining the thermodynamic plasma state with particular respect to the equilibrium situation. Studies to investigate these temperatures through determining molecular temperatures from a comparison with spectral simulation were already initiated and will be applied to existing and future experimental data sets. In addition, measurements of the Doppler temperature from line shapes of atomic lines are possible through Fabry-Perot interferometry. A suitable set-up is in development at UK and will be applied to the HYMETS flows. Support will be given to set up a planar laser induced fluorescence (PLIF) system for the investigation of NO in the facility free stream. Within the project, PhD candidate Bradley Butler will be funded for 9 mo. During this time, several periods at NASA Langley are anticipated for assistance to measurement campaigns. These will be schedules as needed per NASA request.
|Effective start/end date||9/1/16 → 12/23/16|
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