Multiphase Hypergolic Combustion Simulation Tool Based on Algebraic VOF and Compressible Flamelet Methodologies

The innovation proposed is an advanced multiphase hypergolic combustion simulation capability in a computational fluid dynamics (CFD) tool called Loci-STREAM, to improve the understanding of hypergolic ignition and transient flame dynamics which would enhance NASArsquo;s ability to simulate engine-start, main-stage and shutdown characteristics of hypergolic engines. The key objectives of this work are: (1) demonstration of the suitability of compressible flamelet-based models for gas phase combustion of hypergolic propellants, (2) development of a spray combustion capability based on Lagrangian Particle (Droplet) Tracking algorithm, droplet evaporation models, and secondary breakup models, and (3) development of the foundation for modeling impingement of liquid hypergolic propellant jets based on an algebraic volume of fluid (VOF) method. The computational modeling capability resulting from this work will enable us to define the interrelationships between operational parameters (e.g., flows, pressures, timing, etc.) and combustion chamber dynamic responses. The results will help designers and modelers understand relevant environments and inform test engineers of instrumentation best practices to capture relevant behaviors. The user community will also benefit by preventing damage to hardware and designing safer and more efficient start-up sequences. Specifically, the following application areas will benefit immediately from this project: (a) NASArsquo;s ability to simulate engine start, main-stage and shutdown characteristics of hypergolic engines, (b) NESCrsquo;s material compatibility assessment effort involving flammability and ignition susceptibility of titanium in NTO environments, (c) NESC effort to test different materials for O-rings for compatibility with hypergolic propellants, (d) Transient modeling in Draco and SuperDraco engines developed by Space-X, (e) Improved combustion instability predictions for existing and future hypergolic propellant engines, etc.