Laser-based diagnostics of electronically excited oxygen atoms at extreme temperatures
Abstract/Contents
- Abstract
- Tunable diode laser absorption spectroscopy (TDLAS) sensors were developed for in situ detection of electronically excited oxygen atoms (O*) in high-temperature environments. Near-infrared absorption sensing techniques, utilizing electronic transitions near 777.2 nm and 844.6 nm, were implemented to enable sensitive measurements of important thermodynamic flow properties, such as kinetic temperature and excited-state populations. In particular, this work discusses the development and deployment of O* TDLAS sensors for (1) a large-scale arc-heated-plasma wind tunnel and (2) shock tube kinetic studies of O-atom electronic excitation. Collaborative research with NASA's Ames Research Center Thermophysics Facilities Branch was performed to investigate tunable diode laser sensing of gas temperature in the arc-heater plenum of the 60 MW Interaction Heating arcjet Facility (IHF). An external cavity diode laser was used to generate light near 777.2 nm and laser absorption used to monitor the population of electronically excited oxygen atoms in an air plasma flow. Under the assumption of thermochemical equilibrium, time-resolved and spatially-resolved measurements of temperature were obtained at multiple lines-of-sight. Differences between inferred temperatures for distinct lines-of-sight revealed important details regarding the degree of flowfield uniformity in the arcjet plenum. These results led to the design, fabrication, and testing of an extension to the arc-heater column of the IHF to improve gas mixing and overall arcjet performance. In addition to the work performed at NASA Ames, the present work discusses shock tube studies of nonequilibrium electronic excitation processes conducted at Stanford University. Cavity-enhanced absorption spectroscopy (CEAS) was utilized to improve the detection sensitivity of O* laser-based sensors by nearly two orders of magnitude over conventional single-pass schemes. Mixtures of 1% O2/Ar were shock-heated to temperatures up to 8000 K and two distributed-feedback diode lasers near 777.2 nm and 844.6 nm were employed to measure time-resolved populations of two O-atom electronic states. Measurements were compared with simulated population time-histories obtained using two distinct kinetic models that accounted for thermal nonequilibrium effects: (1) a multi-temperature model and (2) a reduced collisional-radiative model. The former assumed a Boltzmann distribution of electronic energy whereas the latter allowed for non-Boltzmann populations by treating the probed electronic states as pseudo-species and accounting for dominant electronic excitation/de-excitation processes. The effects of heavy-particle collisions were investigated and found to play a major role in the kinetics of O-atom electronic excitation at the conditions studied.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Nations, Marcel |
|---|---|
| Associated with | Stanford University, Department of Mechanical Engineering. |
| Primary advisor | Hanson, Ronald |
| Thesis advisor | Hanson, Ronald |
| Thesis advisor | Cappelli, Mark A. (Mark Antony) |
| Thesis advisor | Davidson, David |
| Advisor | Cappelli, Mark A. (Mark Antony) |
| Advisor | Davidson, David |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Marcel Nations. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Marcel Nations
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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