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FALL/WINTER 2002-03

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Studying in a gravity-free classroom

Students in Weightless Wonder

Students Jeffrey Johnson (left) and James Diebel were part of a team that investigated fuel droplet vaporization in microgravity. (37K JPG)

This spring, four UW-Madison students flew aboard NASA's "Weightless Wonder" KC-135a Reduced Gravity Laboratory, a modified Boeing 707, to perform experiments in zero gravity aimed at examining and improving the efficiency of the fuel injection processes that occur in car engines and rocket motors.

"The first time we went up, we weren't ready, so our feet just flew up behind us and we started floating around," says James Diebel, a May engineering physics graduate and principal investigator for the project, of the initial moments aboard the plane.

To create a sense of weightlessness, the pilot aims the plane at an upward angle of 45 degrees, shooting into the sky like a cannonball. Then, at 34,000 feet, the plane pitches over and falls back toward Earth, simulating weightlessness in the rapid descent. The pilot repeats the flight pattern 29 more times, allowing students to collect data under gravity-free conditions.

The project began in fall 2000, with an idea to investigate the vaporization of fuel droplets when sprayed into gasoline engines and rocket motors.

Because engines are driven by energy released when fuel droplets evaporate and burn, engine efficiency is determined by how much fuel evaporates in a given amount of time. In a gravity-free environment, convection, the process that makes hot air rise and complicates the process of vaporization, would be prevented from occurring.

By comparing the results from fuel vaporization in a reduced-gravity environment with those under normal conditions, the students aim to gain a better understanding of how fuel droplets behave under different conditions to optimize the fuel injection process. The findings may be used in helping promote changes in engine design while improving efficiency and reducing emissions.

The reduced-gravity experiment compressed a single droplet of fuel in a small gas chamber by using two steel pistons that each moved 10 inches in less than 30 thousandths of a second. The compression heated and pressurized the droplet to create enginelike conditions.

Students in Weightless Wonder

The students' experiment tested compressed fuel droplets to optimize fuel-injection processes. (40K JPG)

Aboard the plane, the experimental device had enough fuel to run for 20 experiments, and the students spent the remaining time exploring the reduced-gravity environment. "It's a lot like driving over a hill in a car quickly, and you feel your stomach rise, except with this, that feeling just keeps going and lasts for 25 seconds," Diebel says.

In addition to time aboard the Weightless Wonder, the program offered students the chance to take a behind-the-scenes tour of NASA, attend lectures and social events, and explore industry-related internship and job opportunities. Diebel says the educational aspects were the best parts of the program.

"I've learned more about the practical side of engineering than I could in the classroom, and it's given me valuable experience," he says.

 

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Date last modified: Thursday, 07-Nov-2002 16:09:45 CST
Date created: 07-Nov-2002