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External Ignition
Stennis Space Center (SSC) tests liquid rocket engines and components for NASA, the Department of Defense and the commercial space industry. Rockets, and the facilities used to test them, are precision systems that experience extreme temperatures, high vibrations and high pressures during operation. During ground testing, accidental propellant detonation, such as the one in Figure 1, can generate strong pressure waves. The ability to predict these blast occurrences enables SSC to reduce risks to test facilities and adjacent test articles.
Loci/CHEM Simulation
Rockets generate thrust through rapid chemical reactions. Modeling and simulating these reactions requires specialized software, such as Loci/CHEM, developed by Mississippi State University. Loci is a rule-based framework that efficiently maps numerical algorithms to parallel processing systems. CHEM is a Navier-Stokes solver for non-equilibrium flows involving chemical reactions. Loci/CHEM can simulate the complex 3D flows of turbulent, chemically reacting mixtures found in rocket engines.
Predicted Blast Wave
SSC engineers utilized Loci/CHEM to develop a practical, high fidelity, computational fluid dynamics (CFD) methodology to predict the occurrence of detonation events during liquid rocket engine tests, and to understand the propagation of blast waves through test facilities. Verification and validation studies were completed for hydrogen-fueled detonation phenomena, such as shock-induced combustion, confined detonation waves, vapor cloud explosions, and deflagration-to-detonation transition (DDT) processes. The DDT validation cases included predicting flame acceleration mechanisms associated with turbulent flame-jets and flow-obstacles. Excellent comparisons between test data and model predictions were observed. This new capability has been successfully applied to model a detonation that occurred during liquid oxygen/gaseous hydrogen rocket diffuser testing at Stennis Space Center.
A detailed report describing the development and effectiveness of this new technology can be found in the NASA Technical Publication titled "Development of Detonation Modeling Capabilities for Rocket Test Facilities: Hydrogen-Oxygen-Nitrogen Mixtures," (NASA/TP-2016-219220)
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