Current Research Projects
Real-time Diagnostic Techniques for Electrochemical Device Materials
Heat Transfer in Fiber Blanket Insulation
Highly porous fibrous ceramics are widely used as insulating materials in thermal systems due to their high temperature limits and light weight. Due to high temperature applications, the high porosity (>95%), and orientation of the fibers in the construction of the insulation, radiation is the main mechanism for heat transfer in these materials.
A computational model has been developed to evaluate radiative heat transfer in the fibrous ceramic materials. From the model, an effective radiative thermal conductivity of the fibrous insulation is computed and compared to thermal conductivities measured in experiments. The model and the experiments will identify critical parameters of fibrous ceramics to maximize insulating properties.
FASTER-BAT: Fundamental Analysis of Safety factors in design Tools for Extreme Rapid-charging BATteries
Electrochemical Hydrogen Compression
Protonic-ceramic membranes are predominately proton conducting high temperature membranes. These membranes are stable in many environments, which encourages pairing with other processes. The major objective of this project is to produce high pressure hydrogen, which is valuable for applications such as fuel cell cars.
Current technology requires three separate steps to reach high pressure hydrogen: generation, separation, and compression. The generation step is typically achieved by steam reforming natural gas into hydrogen. The separation step removes the extra reforming products such as carbon monoxide from the hydrogen in a pressure swing adsorption process. The final compression step is achieved with a mechanical compressor. This project proposes combining all the steps into a single process, which can be achieved with a protonic-ceramic electrochemical hydrogen compressor. A combination of experiments and simulation are used to understand and optimize the system.
- Students: Jamie Kee, David Curran
- Collaborators: Prof. Robert Kee
- Sponsor: Mines Foundation
Past Research Projects
Improved atomization of liquid fuels is key to reducing pollution and increasing efficiency in diesel engines. Despite significant advances in injector design, there remains a lack of understanding of primary spray breakup in the near-nozzle region. Due to high levels of optical scattering near the nozzle, traditional imaging methods are unable to capture spray structure with sufficient resolution suitable for validating computational models.
Ballistic imaging is able to successfully image dense sprays using a short pulse laser combined with a very fast optical shutter, polarization filtering and spatial filtering. In our approach, we use a 532 nm, 15 picosecond laser pulse that passes through the spray near the injector tip. Using telescopic optics, we are able to image a very small area of the spray and resolve very fine spray structures.
An optical Kerr effect shutter, which is composed of a 2mm pathlength optical cell filled with carbon disulfide and activated by a separate laser pulse at 1064nm, is positioned after the spray. This shutter is able to chop laser pulse exiting the spray down to 7 picoseconds. The shutter and a spatial filter remove much of the scattered light leaving the spray resulting in a high resolution image with highly resolved spray features.
The objectives of this researcher are two-fold: first, we seek to develop advanced ballistic imaging techniques to probe high-injection pressure diesel sprays, and second, we seek to apply ballistic imaging to diesel, JP8, and biodiesel sprays at conditions typical of pre-ignition in diesel engines. The resulting images provide insight into spray behavior and are used to extract quantitative data useful for validation of numerical models.
- Co-PIs: Terry Parker, Derek Dunn-Rankin
- Students: Sean Duran, David Curran
- Sponsor: Army Research Office
Char Gasification Kinetics
Gasification of coal proceeds in two steps: devolatilization and combustion of hydrocarbons trapped within the coal followed by slower char gasification reactions, which convert the remaining fixed carbon to CO and H2 (syngas). These slower char gasification reactions are rate limiting and often determine the size, pressure, and temperature of the gasifier necessary to achieve complete conversion. Though it is a critical step in the coal gasification process, the kinetics of char gasification reactions are not well known at temperatures and pressures typical of entrained flow coal gasifiers, which often operate at temperatures exceeding 1900K and pressures exceeding 40 atm. At these high temperatures, char kinetics are known to be strongly influence by surface and pore diffusion, meaning that mass transport through the particle boundary layer and especially within the pores of the particle determine the rate of the char gasification reactions.
The kinetics of char gasification will be measured using well-characterized coal-derived char particles. These measurements will be made possible by incorporating novel in-situ laser diagnostics into the laboratory-scale entrained flow reactor. Temperature and water vapor concentration will be measured in the argon-buffered steam-char environment of the CSM gasifier’s reactor core. The in-situ diagnostics will be combined with existing online gas chromatography and particle collection diagnostics to measure gasification rates of coal-derived chars in the entrained-flow reactor. Measured reaction rates will be used to develop and validate advanced char gasification models.
The objective of this research is to measure overall char-gasification kinetics in such a way as to enable extraction of intrinsic rate information through in-situ diagnostics, CFD, and detailed particle modeling. This requires not only measuring the overall char reactivity, but also predicting the char temperature history. The char temperature history will be estimated using a CFD code that will use the in-situ gas temperature measurement provided by the water sensor for calibration. Gas sampling and analysis of CO2, CO, H2, and Ar flow rates will provide carbon mass balance, but without in-situ water detection it is not possible to ensure hydrogen and oxygen mass balance, as extractive sampling of H2O at these temperatures and pressures is extremely challenging. Finally, char characterization before and after gasification will enable the creation of realistic detailed particle models.
Optical Diagnostics for Ionic Liquids
Room temperature ionic liquids (RTILs) have received renewed interest in recent years for applications from batteries to environmentally-friendly solvents. RTILs are salts that are liquids at room temperature with very low vapor pressures, large electrochemical windows, and are chemically and thermally stable. The performance of RTILs is highly dependent upon their purity, and producing high purity RTILs is often difficult and expensive. In addition, optical diagnostics provide a tool to study the behavior of RTILs in-situ in applications where transport, chemical stability, or thermal stability is unknown (e.g. as a battery electrolyte).
Our group has developed optical diagnostics for measuring RTIL purity, quantitatively measuring species concentrations, and studying thermal decomposition. These quantitative diagnostics utilize wavelengths in the ultraviolet and the infrared, depending upon the RTIL and the application. We have also applied these techniques in RTILs at elevated temperatures using a specially-designed heated optical cell.
The optical diagnostics are being engineered for in-situ control of RTIL purity during manufacturing. Diagnostics at high temperature will be employed to study thermal decomposition temperatures and kinetics. This work will be assisted by quantum mechanical modeling for interpretation of measured spectra. Finally, this work supports the sodium battery diagnostics being developed separately.
Thermal Imaging of Defects in Fuel Cell Manufacturing
Optical Diagnostics for Sodium-Ion Batteries
- Applying UV/VIS and infrared specroscopy and diagnostics to an optically accessible sodium-ion battery to study transport in the liquid electrolyte at elevated temperature.
- Collaborators: Prof. Robert Kee
- Student: Jeffrey Wheeler
- Sponsors: Sandia National Laboratories, DOE Office of Electricity
Metal Vapor Optical Diagnostics
Carbon buildup on catalyst materials (catalyst coking) is a major issue in the natural gas reforming industry. Poisoning of the active surface by unwanted carbon deposits leads to a loss of catalyst activity, introduces process inefficiencies, and ultimately requires replacement of the catalyst, which is expensive and time consuming. To avoid coking, most reformers operate using excess steam. This requires additional energy to heat the reactants, while decreasing the yield and purity of the products. An in situ carbon sensor that can detect the presence of coking conditions in the feed stream can help to avoid potentially detrimental poisoning of the catalyst and will allow for better control of the feed stoichiometry, thereby improving the reformer efficiency.
We use an inkjet printer capable of printing colloidal suspensions of ceramic powders to make thin layers of catalytic and conductive elements on zirconia discs. These printed layers make up the elements of a Wheatstone bridge electrical circuit. The electrical conductivity of the bridge elements change as carbon deposits form on the sensor surface leading to a change in sensor electrical resistance when it is placed in a coking environment. Monitoring the bridge output voltage provides insight into the poisoning of the catalyst particles in real-time.
The carbon sensor is being designed to function consistently in conditions typical in steam reforming of methane. A functional sensor can successfully detect the early onset of catalyst coking by providing a strong electrical signal when the environment gas composition is conducive to coking. The reusability of the sensor will also be investigated by regenerating the catalyst surface under hot steam. We are also working to identify and minimize false signals due to unwanted gas-phase responses to enable real-time control of the feed composition to avoid coke formation. Electron microscopy is extensively utilized to understand the nature of the carbon deposits on the surface of coked sensors.
- Solid-state sensor to detect coke formation on nickle catalysts in steam- methane reforming.
- Collaborators: Prof. Neal Sullivan
- Students: Jeffrey Wheeler, Najmus Saqib
- Sponsor: Slater Family Research Fund
Hydrogen Separation from Coal-Derived Syngas
- Generating syngas from coal in the CSM gasifier to produce a pure hydrogen stream using membrane separators.
- Student: Madison Kelley
- Sponsor: Praxair/Department of Energy
Thermal Transport in Ceramic Fiber Insulation
- Modeled heat transfer in high porosity ceramic fiber insulation.
- Student: Nicholas Lumley
- Sponsor: MTI