CHARACTERIZATION OF CRITICAL FLOW IN A NOZZLE FOR THE DEVELOPMENT OF LIQUID HYDROGEN JET PUMPS

Yulia Katrina Gitter

The increased globalization efforts around the world have enabled a surge in air traffic within the growing aviation industry. However, the heavy reliance on carbon-based fuels has caused a surge in carbon emissions at higher altitudes, resulting in increased ozone layer thickness and increased warming on the planet. The reliance on these carbon-based fossil fuels has also become unsustainable due to the sheer quantity of fuel needed from a depletable resource. As alternative fuels are investigated, liquid hydrogen has become a prime candidate due to the high gravimetric energy, low mass, versatility in production methods, and universal abundance. The challenge becomes the engineering of systems for this alternative fuel integration. One of the key technologies required for any fuel integration is a pumping system to maintain a constant fuel flow throughout the system. This dissertation focuses on developing an understanding of liquid hydrogen critical flow for the design of venturi jet pumps that achieve consistent pumping, mass flow rate, and subcooling of liquid and two-phase cryogenic hydrogen. In order to understand how to develop a liquid hydrogen jet pump and predict its performance. Chapter 2 starts with a literature review of existing critical-flow reduced-order models and the key experimental apparatuses used for model validation. This section then explores key venturi jet pump models, highlighting the fundamental differences between most reduced-order models, the assumptions made, and the breakdown of nodes within a venturi jet pump. This results in addressing a fundamental knowledge gap, as there is no liquid hydrogen validation data or technological developments, which necessitate this work. Based on this gap, Chapter 3 discusses the development, results, sensitivity analysis, and case studies of the reduced-order model proposed to predict venturi jet pump performance with liquid or two-phase hydrogen. To validate the model, Chapter 4 describes the experimental apparatuses established and tested with current liquid hydrogen capabilities. This includes the full jet pump test apparatus and a sub-test of critical flow through a nozzle, aimed at evaluating the primary nozzle's critical flow performance. Chapter 5 discusses individual primary nozzle critical flow experimental results compared with the established reduced-order model, followed by a comparison of full jet pump performance as nozzle position in the mixing chamber, fluid quality, and fluid pressure are varied. This section then discusses model corrections and, finally, proposes a scaled-up jet pump and analyzes its performance, including mass flow rate and net positive suction pressure, based on experimental learnings. Chapter 6 presents final conclusive remarks and proposes steps forward for future work.

CHARACTERIZATION OF CRITICAL FLOW IN A NOZZLE FOR THE DEVELOPMENT OF LIQUID HYDROGEN JET PUMPS

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