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Advanced Imaging Magazine

Updated: January 12th, 2011 09:49 AM CDT

Searching for Cleaner Fuels

Department of Energy scientists use high-speed imaging as a tool to fight global warming
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By Barry Hochfelder

The microscopic coal particles are reacted with other chemicals to produce a gas commonly referred to as synthesis gas, or syngas. Syngas is very much like natural gas in the fact that it can easily be cleaned and directly burned by turbines to generate electricity for the power grid. By using gasified and liquefied coal from the U.S., we can greatly reduce our dependence on foreign oil. The byproducts of the process can be separated, captured, and stored for reuse or for sale as chemicals.

To make the process more effective and efficient, NETL researchers are studying the high-speed dynamics of microscopic coal particles during gasification. Computer models, called Computational Fluid Dynamics (CFD) models, are being developed to simulate particle motion and mixing in gasification processes. CFD models can be created that accurately simulate particle mixing and chemical reactions in gasifiers, enabling design of the next generation of advanced gasifiers on computers.

But to make the CFD models accurate, scientists must understand exactly how particles behave in gasifier flow fields. The only way to know for sure how these microscopic particles are behaving in such a high-speed, high-concentration environment, is to use very high-speed, high-resolution digital imaging through a borescope.

For this project, the NETL is using the Phantom v12.1 the latest, fastest high-speed digital camera from Vision Research (Wayne, N.J.). The v12 is capable of frame rates exceeding 6,200 frames per second at an image resolution of 1280x800 pixels x 12-bit grey scale resolution. Frame rates can be increased by decreasing the image resolution up to a maximum of 1 million frames per second with exposure times down to 0.3 microseconds.

The particle area is viewed by an endoscope, which carries its own light source. “Because small particles scatter light very inefficiently, we are starved for light,” Shaffer says. “In the 1990s we used pulsed lasers, such as the copper vapor laser, as an extremely bright light source. But the light sensitivity of high-speed cameras has gotten so much better that we now use continuous non-laser light sources. This greatly reduces eye safety hazards and cost. I now use a 100 W halogen lamp from Olympus (ILP-2) with endoscopes from Olympus and Gradient Lens.”



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