Arc-Jet Flow Characterization
Abstract
For more than 40 years, arc-jet testing has served as primary basis for characterizing Thermal Protection Systems (TPS) in support of material development and response model validation. Arcjet facilities provide the only ground-based means of simulating hypersonic heating rates (entry, reentry,hypersonic cruise) in a reacting flow environment under flight-relevant durations. Arc-jet testing provides data for detail material response models that can reduce uncertainty and the magnitude of thickness margins. Arc-jets are also essential to investigate mechanical failure modes including erosion, spallation, and losses related to shear effects. The ability to perform accurate experiments using arc-jet facilities is tightly coupled with the necessity of a careful characterization of the resulting plasma flow. The high uncertainties associated with this class of flows strongly impact the development of new TPS as well as the progress in the fundamental understanding of associated gas-surface interaction phenomena. The flow characterization in representativeconditions (including thermo-chemical non-equilibrium), and the use of advanced diagnostic tools to study the chemistry and physics of the boundary layer is of primary importance.Although arc-jet tests are indicative of how well a material will perform in extreme aerothermal heating environments, it has not been possible to directly relate arc-jet test results to flight applications. The main obstacle has been an inability to determine the total enthalpy of the nonequilibrium arc-jet flow, and its distribution among kinetic, thermal, and chemical modes.Additionally, due to the difficulty of modeling the complex thermochemistry inside the arc heater, high-fidelity computational fluid dynamics (CFD) efforts are typically restricted to the convergent-divergent nozzle and the test section. The spatial profile of the nozzle inlet conditions is generally modeled neglecting many thermo-physical and fluid dynamics phenomena. Bypassingthe complex mixing problem in the plenum and neglecting flow nonuniformities, however, hinders the accuracy of CFD simulations. As a result, reliable measurements of arc-heater conditions are needed to properly anchor and improve the accuracy of the CFD analysis.The objective of this proposed work is to develop diagnostic techniques to determine these quantities, thereby improving our understanding of the relationship between arc-jet test and flight environments.As part of this effort, a laser-based spectroscopic system will be developed to characterize the flow environment by measuring the free-stream enthalpy in the proposer~s large-scale arc-jet facility. Flow properties including velocity, translational temperature, and species concentration (atomic nitrogen and atomic oxygen), will be measured over a range of facility operatingconditions. Two measurement capabilities, femtosecond two-photon absorption laser-induced fluorescence (fs-TALIF) and femtosecond laser electronic excitation tagging (FLEET) velocimetry, will be developed and utilized for the proposed, quantitative, measurements. The successful completion of this project will result in an improved understanding of the nonequilibriumflow field, heat transfer and model uncertainties, ultimately improving the testing and design of advanced thermal protection systems.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 25, 2019
- Source ID
- N000141912250
Entities
People
- Luca Maddalena
Organizations
- Office of Naval Research
- United States Navy
- University of Texas at Arlington