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Lehigh University logo
Lehigh University logo

Wen Shi and Charles Verhoog

Hypersonic Expansion Tube

Department: Mechanical Engineering
Advisor: Dr. Tobias Rossmann

Abstract:
The hypersonic expansion tube is the most essential facility for conducting high-speed flow experiments. It is similar to the widely applied shock tube for simulating the actual physical conditions in supersonic flight. it allows a high pressure gas to drive a lower pressure gas to create high speed flows for a short test time (< 1ms) and attain a high speed up to Mach 8. The tube set is composed of four sections, the driver, the double diaphragm, the driven, and the expansion. The pressure difference in sections generates a shock wave and accelerates the test gas to come out of the tube exit and arrive the viewing section.

Sonic jets in a hypersonic crossflow are the primary method of injection for scramjet engines. To create a reliable source of ignition in the engine, the mixing and combustion process must be completely understood. This research seeks to understand the effect on mixing and combustion due to different momentum jet ratios between a sonic hydrogen jet and a hypersonic crossflow. Through this information more accurate computer simulations can be made which in turn can increase the efficiency of the engine. Two different highspeed imaging systems are used to analyze the jet mixing and combustion. A Schlieren imaging system shows density gradients in the flow and is used to view the jet and corresponding shock wave. An OH* chemiluminescence imaging system visualizes the combustion in the jet by imaging the protons given off by excited OH molecules during the combustion process.

Compressible pipe flows play an essential role in cruise phase of hypersonic flight. Boundary layers are important elements in combustion chamber inlets and motor nozzles of high-speed traveling vehicles. This research explores the viscous effects in supersonic jets by targeting on the most important analogous parameter for categorizing viscous effects, Reynolds number. The two flow qualities related to Reynolds number are core-flow size and test times. Besides computer programming simulations for flow conditions, this research is also involved in conducting supersonic flow tests with infrared (IR) sensors, and high-speed pressure transducers in concert with timer counter systems. All the instruments are used to capture visual and digital data for further characterizing the Reynolds number effects in test gases.

About Wen Shi:
Wen Shi is a senior engineering student honored as a Marquis Scholar at Lafayette College. She is studying mechanical engineering with a minor in Mathematics. Her interest in aerodynamics studies has led her to engage in an undergraduate research on hypersonic jets under Professor Tobias Rossmann. After graduating from Lafayette, Wen will strengthen her knowledge in an M.S in either engineering management or industrial engineering and operations research.

About Charles Verhoog:
Charles Verhoog is a senior mechanical engineering student at Lafayette College. He has participated in a multidisciplinary project to assist older adults, but main interest is aerospace engineering. In addition to his academic pursuits, Charles is a founding member of DTD fraternity, Nu chapter.