Multiphase shock tube offers insights into physics early in blasts
by Sue Holmes
Sandia’s one-of-a-kind multiphase shock tube began with a hallway conversation about five years ago that culminated in the creation of what engineer Justin Wagner describes as the only shock tube in the world that can look at shock wave interactions with dense particle fields.
Shock tubes have been around for decades. What makes Sandia’s unique is its ability to study how densely clustered particles disperse during an explosion. That’s important because understanding the physics that occurs at the first tens of microseconds of a blast can help improve computer codes that model what happens in explosions.
“Not having this correct in those codes could have implications for predicting different explosives properties,” says Justin (1515).
In that years-ago conversation, Steve Beresh (1515) and Sean Kearney (1512) asked a since-retired colleague, Melvin Baer, what he’d like to measure that he hadn’t been able to. “He started talking about some of the missing physics that were in the models that are used for predicting explosives, and Sean and I looked at each other and said, ‘We think we could do that,’” Steve recalls.
They came up with the idea of a multiphase shock tube that would enable researchers to study particle dispersal in dense gas-solid flows. The project was initially funded under the Laboratory Directed Research and Development program.
“We needed somebody to actually make it work so we hired Justin as a postdoc” to oversee the design and building phase, says Steve. Justin has since joined Sandia’s regular staff.
“When we hired Justin we had an empty room and a blank sheet of paper. Now we have a shock tube that is different from what anybody else in the world has,” Steve says.
First fired in 2010
The machine, first fired in April 2010, is considered multiphase because it can study shock wave propagation through a mixture of gas and solid particles.
Particulates in an explosion start out tightly packed. As the explosive process continues, they disperse more and more and quickly become widely spaced. But the physics of the densely packed particles at the start of the explosion are crucial to everything that comes later. Currently, they are not thoroughly understood, and therefore existing models are equally limited, Steve and Justin say.
The team says better understanding the particle dynamics in the early part of a blast will help Sandia respond to national security challenges surrounding detonations, including improving explosives, mitigating blasts, or assessing the vulnerability of personnel, weapons, and structures.
A shock tube generates a shock wave without an explosion. “The important thing about the shock tube is it generates a planar shock wave,” Justin says. “We study the interaction of the shock wave with a dense field of particles to understand the physics relevant to explosives processes.”
The multiphase shock tube uses such diagnostics as high-speed pressure measurements, high-speed imaging, and flash X-ray to measure gas and particle properties, and it’s adding laser-based diagnostics, Steve, Sean, and Justin say.
A better view of the physics
“We can get different things from the X-ray diagnostics, different things from the laser-based diagnostics, different things from temperature and pressure measurements, and by piecing all of that together we get a better view of the physics that are occurring in the shot,” Steve adds.
The machine’s unique diagnostic capabilities demonstrate Sandia’s ability to collaborate. The team particularly singles out the X-ray expertise offered by Enrico Quintana and Jerry Stoker’s group in Org. 1522.
“Once you get the thing built, then the diagnostics required to get useful information out of it are also difficult and expensive,” Justin says. “There’s a reason why it hasn’t been done thoroughly in the past.”
A lot of data for modeling come from explosions, but it’s difficult to isolate what happens in each part of a blast, Sean says.
“Whereas if you do an experiment like this you can delve deeper into what is really happening,” he says. “But it’s just one piece of the puzzle and they’re all important.”
The stainless steel and aluminum shock tube, about 22 feet long, is divided into a high-pressure or driver section that creates the shock wave, and a low-pressure or driven section, with a diaphragm or burst disk between the two. Pressure builds up in the cylindrical driver section and when it gets high enough, the diaphragm ruptures. Spherical particles loaded into a hopper above the low-pressure section flow into the shock tube before the diaphragm breaks, creating a dense particle curtain that’s hit by the shock wave.
Justin, Steve, Sean, and Brian Pruett (1515), along with Wayne Trott, Jaime Castaneda, and Melvin Baer, all now retired, made a presentation on the work in April 2011 to the Engineering Sciences External Review Board. The team says Elton Wright (6916) also made a sizeable contribution to the project.
Experiments and diagnostics are complicated, so team members are still gathering data to eventually incorporate into codes used at Sandia and elsewhere.
“It’s clear that we’ve learned some things that weren’t known before,” Steve says. “Those physics [inputs] are important to a code.”-- Sue Holmes
Federal Laboratory Consortium tips hat to wide range of Sandia work
by Nancy Salem
Sandia was honored four times by the Federal Laboratory Consortium (FLC) for its work to develop and commercialize innovative technologies.
The FLC’s Far West/Mid-Continent regional awards recognized Sandia’s technology transfer work with crystalline silico-titanates (CSTs), biomimetic membranes, DAKOTA software, and the i-Gate Innovation Hub.
“It is always gratifying when the Federal Laboratory Consortium shines a light on the amazing work that is taking place at Sandia National Laboratories,” says Jackie Kerby Moore, manager of Technology and Economic Development Dept. 1933 and Sandia’s representative to the FLC. “They recognized the entire spectrum of our work, from technology development to technology transfer, as well as the economic impact that technology transfer creates."
CST ion exchangers
The Excellence in Technology Transfer award went to people involved in development and commercialization of CSTs — business development specialist Bianca Thayer (1931), Geochemistry Dept. 6915 Manager Mark Rigali, and researcher Tina Nenoff (1114).
CSTs are inorganic, molecularly engineered ion exchangers that can remove high-level radioactive contaminants such as cesium from wastewater. UOP, a Honeywell company, licensed the Sandia technology in the mid-1990s and revised the license last year to become the exclusive US manufacturer of CSTs.
CSTs played a role when the Fukushima Daiichi nuclear power plant outside Tokyo was damaged in an earthquake and tsunami on March 11, 2011. Seawater was pumped in to cool the reactors. The water was contaminated with cesium and could not be released back into the ocean.
Tina, who had experience developing and working with CSTs in the 1990s, was called upon to test the material for removal of cesium in seawater. She worked around the clock for 10 days, concluding that CSTs outperformed other materials in removing cesium from seawater.
Honeywell UOP products with CST technology have successfully treated more than 40 million gallons of contaminated water at Fukushima.
The Notable Technology Development award recognized researcher Susan Rempe (8635) and her team’s work with biomimetic membranes, a revolutionary advance in the field of membrane technology for water filtration.
Nearly half the world’s population has inadequate access to clean, fresh water. Desalination plants pass salt water through membranes that remove salts and create drinkable water. But membrane technology has advanced slowly the past 30 years.
The biomimetic membrane, inspired by how the human body filters water, uses self-assembly and atomic layer deposition. It is designed for water purification using reverse osmosis technology, which removes impurities with applied pressure powered by electrical energy.
The Sandia technology received an R&D 100 Award in 2011. “We made a synthetic membrane that mimics the nanoscale design features of natural water purification channels,” Susan says. “By doing so, our initial membranes achieved a 10-fold improvement in water purification efficiency compared with state-of-the-art RO membranes.”
Biomimetic membranes can increase access to clean water by dramatically reducing energy use and costs.
The Outstanding Partnership Award recognized the i-GATE regional public-private partnership in California designed to support small businesses and maximize the economic potential of green transportation and clean-energy technologies. i-GATE (Innovation for Green Advanced Transportation Excellence) creates a link between national laboratories and entrepreneurs, industry, venture capital, universities, and economic development resources to accelerate the commercialization of energy technologies and grow a cohesive innovation ecosystem.
The i-Gate National Energy Systems Technology (NEST) incubator opened in June 2011 to help small companies work with advanced transportation or renewable energy technologies that can leverage technical assistance from Sandia/California or Lawrence Livermore National Laboratory. The i-GATE NEST has helped create 62 direct and 118 indirect jobs.
The award recognized Bruce Balfour (8539), a Sandia technical business development specialist and i-GATE president; Rob White, city of Livermore Economic Development director and i-GATE CEO; Louis Stewart, deputy director of Innovation and Entrepreneurship, California Governor’s Office of Business and Economic Development; and Buck Koonce, director of Economic Development at Lawrence Livermore National Laboratory.
The fourth FLC award was an honorable mention for Notable Technology Development that went to DAKOTA software and the project lead, computer scientist Brian Adams (1441). Engineers often need computational simulations to solve scientific problems.
Sandia’s Design Analysis Kit for Optimization and Terascale Applications (DAKOTA) is an open-source software tool that helps researchers adjust and assess the accuracy of such models.
DAKOTA helps researchers know if their simulations are accurate and how they can be optimized to produce the most realistic, reliable predictions. The software answers such questions as how reliable or variable a system is and what models or parameters best match experimental data.
DAKOTA shortens design cycles and cuts development costs. It is used extensively at national laboratories to solve a wide range of energy and national security-related problems, and to conduct research with academic, government, and industrial partners.
“This year we were honored for our technology transfer successes across the globe as well as closer to home,” Jackie says. “Whether our impact was in Japan or our own Livermore community, our technologies and our people are making a difference.”
The FLC is a nationwide network of more than 300 members that provides the forum to develop strategies and opportunities for linking laboratory mission technologies and expertise with the marketplace.
The FLC Awards Program annually recognizes federal laboratories and their industry partners for outstanding technology transfer efforts. Since its establishment in 1984 the FLC has presented awards to nearly 200 federal laboratories, becoming one of the most prestigious honors in technology transfer.-- Nancy Salem
Sandia benchmark helps wind industry measure success
A just-released Sandia study on wind plant reliability should help the nation’s growing wind industry benchmark its performance, understand vulnerabilities, and enhance productivity.
Until now, wind farm owners and operators had no way to compare their output with the output of similar operations. To benchmark the reliability of the US wind turbine fleet and identify major causes of failures and downtime, DOE commissioned Sandia in 2010 to build the Continuous Reliability Enhancement for Wind, or CREW, database. This is the first effort to compile a comprehensive, operator-independent dataset that accurately reflects the performance of the US wind fleet.
Every year, Sandia surveys the database and publishes the results to help benchmark the industry. The more than 800 wind turbines studied for the 2012 Wind Plant Reliability Benchmark are either producing electricity or are available to produce electricity 97 percent of the time, up from 94.8 percent in 2011.
“With better understanding of how major turbine systems are performing, wind operators can focus on improving those areas that will drive increased reliability and efficiency,” says CREW team lead Alistair Ogilvie (6121).
In 2008, a DOE collaborative published “20% Wind Energy by 2030.” The report suggests that by 2030, wind could supply 20 percent of the nation’s electricity, compared to less than 1 percent in 2007 and 3 percent in 2011. The report also discussed industry-wide risks related to lower-than-expected reliability and growing costs of operations and maintenance.
Objectively characterizing the fleet
“Our assignment from DOE is to objectively characterize the national fleet,” says Valerie Peters (6121), CREW lead reliability analyst. “We’re looking across technologies, locations and companies to create benchmarking statistics for the entire US wind turbine fleet.”
Major turbine systems include a set of three blades, rotor, shaft, generator, and gearbox, and all of those components might break or otherwise need maintenance. Sandia’s team is working to determine which components are the most vulnerable and help industry address those concerns to prevent downtime. The costs associated with a turbine going offline add up quickly. The owner not only loses productivity, but the cost of hiring a crane for repairs can be upward of $250,000. Since only a few cranes in the nation are large enough to handle turbine heights and component weights, it may be months before the turbine is up and running again.
Four wind plant owner/operators are participating in the development phase of the CREW project: EDF Renewable Energy (formerly enXco Service Corp.), ShellWind Energy, Wind Capital Group, and Xcel Energy. Sandia researchers are able to collect high-resolution data from key operating parameters such as wind speed, ambient temperatures, blade angles, component temperatures, and torques. Every few seconds, a wind turbine’s SCADA system captures a complete picture of how the turbine and its components are performing, compared to a defined operating environment.
CREW database contains data for more than 800 turbines
Sandia’s CREW database contains data for more than 800 turbines, which have generated two terabytes of raw data, about 20 percent as large as the entire print collection of the US Library of Congress. Sandia’s Enterprise Database Administration Team is processing this enormous dataset into a usable database that can readily support a wide range of rapid queries.
The gathered data is used for various analyses, including public benchmark reporting and DOE reports. DOE uses its reports to guide research and development investments by identifying critical issues and strategies to improve wind technologies.
The annual public benchmark report characterizes the operations and maintenance experience of the US fleet, using aggregated reliability and performance metrics that let owner/operators compare their plant against the CREW fleet.
“We’re excited about the results so far and look forward to the next few years as we make an important contribution to the industry to improve reliability through a component-level focus,” Alistair says. “It’s an important project that will help encourage increased use of a low-carbon power source, and it could not have succeeded without the outstanding support and leadership of the wind industry and DOE. Together we can share our expertise to help shape the future of the nation’s wind energy generation.”
The CREW Database Wind Turbine Reliability Benchmark and other Sandia wind energy publications are available on Sandia’s website at http://energy.sandia.gov/crewbenchmark.
-- Stephanie Hobby