Development of coupling approach for integrated analysis of thermo-fluid dynamics inside cryogenic tanks
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Authors
Lan, Eymon
Issue Date
2024-08
Type
Electronic thesis
Thesis
Thesis
Language
en_US
Keywords
Mechanical engineering
Alternative Title
Abstract
Numerical analysis of thermo-fluid dynamics for cryogenic propellant storage is vital to future space mission planning. This analysis primarily consists of nodal and computational fluid dynamics (CFD) modeling approaches. While nodal approaches prioritize faster computation over fidelity, CFD approaches promise accuracy and fidelity at the expense of significant computational resources. This dissertation explores the state-of-the-art modeling approaches to simulate cryogenic propellant behaviors under storage conditions including self-pressurization periods and during active pressure control. To have a deeper understanding of the limitations of each numerical analysis code, the accuracy and speed of each code were assessed by simulating cryogenic propellant storage scenarios suitable for each approach.First, the nodal modeling approach was utilized to simulate the tank self-pressurization period of a Multipurpose Hydrogen Test Bed experiment, which represents a prototypical sized cryogenic propellant storage tank of approximately 3 meters in diameter. This was achieved by first identifying the major heat transfer mechanisms in both fluid domains. Then, closure models and constitutive relations were implemented to model the internal flow, and interfacial heat and mass transfer. Results show the predicted pressure evolution of the tank agrees well with experimental data for both 50% fill level and 90% fill level cases. A discrepancy was observed in the vapor temperatures comparison with experimental data. The difference was attributed to the assumption of conduction within the vapor region due to a lack of correlations to model the heat transfer within the vapor region in the presence of thermal stratification.
Next, the CFD approach was used to simulate fast transients such as jet induced mixing during active pressure control. Due to the immense computational requirements and available experimental data, the tank pressure control experiments (TPCE) were identified as a suitable study. Simulation results show the higher fidelity CFD simulation can track the liquid vapor interface and resolve the internal flow using turbulence modeling. In addition, due to thermal considerations, the model was used to perform a parametric study to determine the jet Weber number for penetration of the ullage bubble.
The final part of the dissertation presents a coupling methodology developed to facilitate the simulation of a long-term self-pressurization process of a cryogenic propellant tank. The key highlight of this methodology is the development of a coupling scheme that employs a domain decomposition approach, effectively dividing the computational domains at the liquid-vapor interface. SINDA/FLUINT, the nodal code, is utilized to simulate the liquid region, while ANSYS Fluent, the CFD code, handles the vapor region. An algorithm was proposed to compute the required boundary conditions for the split domains from the local thermodynamic properties of the assumed infinitesimally thin interface. However, due to restricted access to either of the commercial source codes, the data exchange was facilitated through an external routine that computes the interfacial evaporation losses based on temperature and pressure values at the interface. The coupling between the nodal and CFD codes was demonstrated by simulating a self-pressurization process in a small size tank using hydrogen as the working fluid. The effectiveness of the coupling methodology was assessed by comparing the temperature and pressure evolution results from the coupled simulation with those obtained solely from CFD simulation. Additionally, a sensitivity study on the grid sizing and coupling time step was conducted to determine an appropriate spatial resolution to ensure a divergence-free explicit data exchange time step size. Results showed that the interface coupling scheme was successfully implemented, and the coupled simulation agreed well with the CFD simulations. Using the coupling approach, two numerical case studies were considered based on different initial fill levels of the tank to study the pressurization rate. To compare the required computational time, the computational costs associated with both approaches were compared. Lastly, the recommendations for future work was provided in order to improve the accuracy of nodal model and improve upon the current coupled modeling framework in terms of computational speed up and scalability.
Description
August 2024
School of Engineering
School of Engineering
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY