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Full-Text Articles in Mechanical Engineering
A New Technique To Determine Accommodation Coefficients Of Cryogenic Propellants, Kishan Bellur
A New Technique To Determine Accommodation Coefficients Of Cryogenic Propellants, Kishan Bellur
Dissertations, Master's Theses and Master's Reports
The control of propellant boil-off is essential in long-term space missions. However, a clear understanding of cryogenic propellant phase change and the values of accommodation coefficients are lacking. To that effect, a new method to determine accommodation coefficients using a combination of neutron imaging, thin film evaporation modeling and CFD modeling has been established. Phase change experiments were conducted in the BT-2 Neutron Imaging Facility at the National Institute of Standards and Technology (NIST) by introducing cryogenic vapor (H2 and CH4) at a set pressure into Al6061 and SS316L test cells placed inside a 70mm cryostat. Condensation is achieved by …
Development Of An Evaporation Sub-Model And Simulation Of Multiple Droplet Impingement In Volume Of Fluid Method, Sathya Prasad Potham
Development Of An Evaporation Sub-Model And Simulation Of Multiple Droplet Impingement In Volume Of Fluid Method, Sathya Prasad Potham
Dissertations, Master's Theses and Master's Reports
Droplet collision and impingement on a substrate are widely observed phenomenon in many applications like spray injection of Internal Combustion Engines. Existing Lagrangian models do not provide a comprehensive picture of the outcome of these events and may involve model constants requiring experimental data for validation. Physics based models like Volume of Fluid (VOF) method involve no parametric tuning and are more accurate. The aim of this thesis is to extend the basic VOF method with an evaporation sub-model including an additional vapor phase and implement this model in an open source Computational Fluid Dynamics (CFD) software, OpenFOAM. The new …
An Assessment Of The Validity Of The Kinetic Model For Liquid-Vapor Phase Change By Examining Cryogenic Propellants, Kishan Bellur
An Assessment Of The Validity Of The Kinetic Model For Liquid-Vapor Phase Change By Examining Cryogenic Propellants, Kishan Bellur
Dissertations, Master's Theses and Master's Reports
Evaporation is ubiquitous in nature and occurs even in a microgravity space envi- ronment. Long term space missions require storage of cryogenic propellents and an accurate prediction of phase change rates. Kinetic theory has been used to model and predict evaporation rates for over a century but the reported values of accommodation coefficients are highly inconsistent and no accurate data is available for cryogens. The proposed study involves a combined experimental and computational approach to ex- tract the accommodation coefficients. Neutron imaging is used as the visualization technique due to the difference in attenuation between the cryogen and the metallic …