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Prof. Michael Winter, Mechanical Engineering

Spectrally resolved simulation of plasma and combustion radiation

Plasmas and combustion gases emit radiation which, if measured appropriately, can be interpreted with respect to governing temperatures and species contributions and concentrations. For this interpretation, good knowledge of the spectrally resolved emission is crucial which typically can be simulated using so called line-by-line codes. In these codes, the simulation of molecules and atoms is simulated in form of individual transitions, typically from upper electronic states (for atoms and molecules) or/and from excited vibrational and rotational states (molecules only). In addition, line broadening mechanisms such as collisional and Doppler broadening have to be taken into account. For significantly ionized plasmas, continuum emission from bound-free or free-free transitions becomes important, too. Typical applications of such simulation are the investigation of all types of plasmas, as found in electric propulsion for spacecraft, during atmospheric entries, or in technical plasmas used for surface odification processes, and in all combustion applications.

Students and Staff

Michael Winter (Faculty)
Zhaojin Diao (Postdoc)
Helmut Koch (Grad, visiting scholar)
Raphael Tietz (Grad, visiting scholar)
Ricky Green (Grad)
Avery Hartley (Undergrad)

Software

Neqair (NASA line-by-line simulation code)
CEA (NASA code for the computation of chemical composition of air at high temperatures)
several in-house codes for Abel-Inversion and data processing
((ANSYS))

Radiation Heating from the Arc Column of the NASA Ames Interaction Heating Facility (IHF)

The NASA Ames IHF is the most powerful of the Ames arc-jet facilities, typically used for the qualification of thermal protection systems for the atmospheric entry of spacecraft. In the past, various diagnostic measurements were conducted in this facility to characterize the plasma flow in the arc-jet plenum before the convergent-divergent nozzle and in the freestream at the sample position. In addition, measurements of radiative heating to a sample in the plasma flow generated inside the arc heater were performed through an optical probe looking in the upstream direction. The plenum of the arc heater is the starting position for CFD analysis of the flow and was of particular interest to verify this starting condition. Differences were found between measured emission spectra at this position, if compared to simulated spectra based on the CFD simulation. It is hypothesized that these differences might be at least partly explained by absorbed radiation generated in the 4.5 m long discharge section upstream of the plenum position.

In this work, an existing procedure for radiation transport analysis inside the plenum region shall be extended to cover the upstream discharge region. The NASA Ames code ARCFLO shall be used to define an initial flow field condition for selected heater conditions. Based on this starting condition, a radiation transport analysis shall be set up based on equilibrium plasma conditions generated with the NASA code CEA which will be used as input for simulated emission spectra using the NASA Ames code NEQAIR. Through a successive variation of the plasma conditions inside the discharge column, the resulting spectra shall be modified until they match the experimental results of the optical probe. The resulting condition will serve as a basis to determine the radiation imposed onto the plenum plasma to determine radiation absorbed in this region.

Students

Raphael Tietz, MS, visiting scholar

Computation Methods

The work requires the computing chemical composition of air at high temperatures, which is needed to simulate the spectrally resolved emission of these plasmas, followed by a radiation transport analysis of the emission inside the NASA arc heater.

Software

• ((Neqair)) (NASA)
• ((CEA)) (NASA)
• in-house code for spectrally resolved radiation transport

Support of Plasmadiagnostics in the UK Low Power Plasma Facilities

Several low power plasma facilities have been built up in the ME department to investigate non-equilibrium and equilibrium plasmas with particular respect to their interaction with sample surfaces. The characterization of the operational envelope of these facilities widely relies on optical diagnostics, which must be supported by a spectral simulation of the observed emission spectra. The diagnostic methods under development are also applied to larger NASA facilities.

Collaborators

Zhaojin Diao

Students

Helmut Koch, PhD, visiting scholar

Computation Methods

The work requires the simulation of the spectrally resolved plasma emission to assist the determination of plasma temperatures and composition.

Software

• Neqair (NASA)
• in-house code for Abel-inversion

Active Grants

• AFOSR through Ohio Aerospace institute (OAI), Experimental Investigation of Image Distortion in Hypersonic Flows, Michael Winter, January 7, 2017 to January 31, 2020.

Past or Pending Grants

• KY NSF EPSCoR Track I concept proposal, Plasma-catalysis: A Next Generation Approach for Chemical Processing, Co-PI Michael Winter with Mahendra Sunkara et al., Conn Center Louisville, duration 5 years, total $6,537,648, UK part $750,000, pending.

• Improving Heat Shields for Atmospheric Entry: Numerical and Experimental Investigations of Ablative Thermal Protection System Surface Degradation Effects on Near-Wall Flow, NASA & KY Statewide EPSCoR Match, 3 years from October 2013 to October 2016, PI Suzanne Weaver Smith, Science PI Alexandre Martin, Co-PIs Sean Bailey, Michael Winter, Chi Shen, Janet K. Lumpp.

• NASA Kentucky GF RFP-15-001: Remote Recession Measurements of Ablative Heat Shield Materials, PI Michael Winter, Co-I Haluk Karaca, January 1, 2015 to May 31, 2016.

• NASA Kentucky GF RFP-15-001: Methodology for Reliable Emissivity Measurements at High Temperatures to support NASA Free-Flight Experiments, PI Michael Winter, CoI Dusan Sekulic, January 1, 2015 to August 31, 2015.

• NASA Kentucky RIDG RFP-15-002: Experimental Investigation of Gas-surface Interactions of Ablative Materials in Low Power Plasma Facilities, Michael Winter, June 1, 2015 to May 31, 2016.

• NASA Ames, Investigation of Gas-surface Interactions of Ablative Materials in Low Power Plasma Facilities, Michael Winter, July 31, 2015, end January 31, 2017.

• IR4TD/PTC internal funding mechanism: Quick Curing Of Painted Samples Using Radio Frequency, PI Ahmad Salaimeh, co-PI Michael Winter.