Staring deep into the flame

A new X-ray technology to measure temperatures in a combustion flame could lead to cleaner biofuels.

Understanding the dynamics of combustion Biofuels Fuels made from plants, algae or animal waste are essential to building clean, efficient biofuel engines. An important driver of these dynamics is temperature.

Scientists from the US Department of Energy’s (DOE) Argonne National Laboratory, Yale University and Penn State University have refined and used an X-ray technique to measure temperatures in an extremely hot, soot-borne flame. Such measurements have historically been difficult. The new technology could help reduce emissions from biofuel engines.

“Temperature has a significant impact on chemical reaction rates in flames. If the models do not contain accurate temperatures, they probably do not predict the chemistry correctly. Better combustion models allow researchers to design better combustion systems.” – Alan Kastengren, Argonne physicist

The need for improvement Biofuels

Reducing emissions of greenhouse gases and other pollutants from fossil fuel combustion will require major changes to energy systems. The US Energy Information Administration Reports indicate that there are more than a billion fossil-powered vehicles worldwide, and the conventional vehicle fleet is expected to reach its peak in 2038.

Advanced, cleaner burning Biofuels It can help reduce pollutants in the meantime. This is especially true for aircraft, ships and other heavy vehicles that are still difficult to electrify with current technologies.

But developing new combustion systems for advanced biofuels is not an easy task. The main barrier was the accurate measurement of temperatures in the flames from the combustion of biofuels. Temperatures are a critical input into the models that researchers use to simulate flames and their emissions.

“Temperature has a significant impact on chemical reaction rates in flames,” said Alan Castingren, an Argonne physicist who was one of the study’s authors. “If the models do not have accurate temperatures, they probably do not predict the chemistry correctly. Better combustion models allow researchers to design better combustion systems – whether they are internal combustion engines or electricity generation systems.”

X-ray temperature measurement and krypton atoms

Measuring flame temperatures is surprisingly difficult. Researchers have previously used lasers and other devices to assess flames. However, the soot particles in the flame can interfere with its ability to measure temperature.

X-rays are largely unaffected by soot particles, so another possibility is to use X-ray beams to analyze the flame. Argonne, Yale and Penn State researchers used and refined a technique known as X-ray fluorescence. The technique involved several steps. First, they inserted a small amount of gaseous krypton into a flame consisting of air and methane (an essential component of natural gas). This is the standard flame used by laboratories around the world in combustion research. Krypton is an element with a very low reactivity, so it does not change the chemistry of the flame.

Then, at the Argonne Advanced Photon Source (APS), a DOE Office of Science User FacilityThe researchers bombarded the flames with high-energy X-rays. In response, the krypton atoms released X-rays with a unique amount of energy in a process called fluorescence. The team then used an X-ray spectrometer to detect the energy of the X-rays emitted. This enabled the researchers to map the presence of krypton atoms and determine their density throughout the flame. Next, the team calculated the temperatures in different parts of the flame, using an equation known as the ideal gas law that relates temperature and density.

The key to the experiment’s success was the use of ultra-bright X-rays in APS. X-ray beams generated from facilities such as APS It has a much greater intensity and more focused rays than those created in laboratories.

“The lab-scale X-ray source is a bit like a light bulb. X-rays are coming out in all directions,” Castingren said. “With synchrotrons, all the X-ray beams go in the same direction. This makes it easier for us to use the beam effectively to measure interactions with the flame.”

Many ways to apply technology

As the researchers refine the X-ray technique using methane flames, the methods can be applied to measure temperatures in other flames, including those from biofuel combustion. This could help improve the accuracy of models used to simulate flames in biofuel combustion systems. More powerful models could enable discovery of new ways to power aircraft engines, gas turbines and other power generation systems so that they are more efficient and with lower emissions.

“Imagine converting aircraft from standard fuels to sustainable jet fuel,” said Robert Tranter, a senior chemist at Argonne and author of the study. “You need to understand the effect this switch has on the combustion properties of the engine to make sure it is working properly. It is very expensive to physically test new fuels in a real-world engine. Accurate combustion models can sift through the fuel to help determine when to perform those tests.”

More broadly, X-ray methods can enhance understanding of fundamental aspects of combustion, supporting a wide range of research areas. For example, they could direct efforts to develop systems that burn hydrogen to produce energy. They can help research the use of flames to create silicon nanoparticles, which have potential applications in medicine, batteries and other fields.

This technique can even be applied outside the scope of combustion research. It can support any laboratory experiments that require accurate temperature measurements in hostile environments.

“We always run into different systems in which researchers need accurate temperature measurements,” Tranter said. “We are open to cooperating with them.”

The study was published in science progress. In addition to Kastengren and Tranter, the authors are Matthew J.Montgomery, Yale; Hyungok Kwon, Penn State; Lisa de Pfeverley, Yale; Travis Sykes, Argonne; Yuan Xuan, Penn State and Charles S. McNally, Yale.

This research was supported by the Department of Energy’s Office of Energy Efficiency and Renewable Energy in the Bureau of Bioenergy Technologies and the Office of Vehicle Technologies as well as the Basic Energy Science and Gas Phase Chemical Physics Programs in the DOE Office of Science.

About the advanced photon source

The US Department of Energy’s (APS) Advanced Photon Source at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. APS provides high-brightness X-rays to a diverse community of researchers in materials science, chemistry, condensed matter physics, life sciences, the environment, and applied research. These X-rays are ideally suited for the exploration of biological materials and structures; the distribution of the elemental chemical, magnetic and electronic states; and a wide range of technologically important engineering systems from batteries To supply fuel injector nozzles, all of which are the basis of the economic, technological and material well-being of our nation. Each year, more than 5,000 researchers use APS to produce more than 2,000 publications detailing the influential discoveries, solving more vital protein structures than any other research facility uses for an X-ray light source. APS scientists and engineers create technology that is at the heart of driving accelerators and light sources. This includes input devices that produce extremely bright X-rays that researchers value, lenses that focus X-rays down to a few nanometers, devices that increase the way X-rays interact with the samples under study, and software that collects and manages the massive amount of data generated by APS discovery research. .

This research used Advanced Photon Source Resources, a US Department of Energy user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract DE-AC02-06CH11357.

Argonne National Laboratory It seeks to find solutions to pressing national problems in science and technology. Argonne, the country’s first national laboratory, conducts groundbreaking basic and applied scientific research in nearly every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state, and municipal agencies to help them solve their specific problems, advance American scientific leadership, and prepare the nation for a better future. With employees from more than 60 countries, Argonne is managed by UChicago Argonne, LLC to US Department of Energy Office of Science.

US Department of Energy Office of Science It is the largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information visit ience.