at larger scales (electric vehicle or gridscale energy storage) has been hampered by insufficient energy densities, prohibitive material costs, and safety concerns. [2] While significant progress has been made in the development of high energy density battery materials, the implementation of these materials in practical systems without sacrificing cell longevity or safety remains a pressing scientific challenge. One of the best studied approaches to improve the energy density of LIBs is to replace existing graphitic anodes (372 mA h g −1 capacity) with metallic lithium (3860 mA h g −1 capacity). [3] Unfortunately, uneven lithium plating and stripping in conventional organic liquid electrolytes promotes the growth of lithium dendrites, accelerating the formation of internal short-circuits. Additionally, the low thermal stability of electrolyte solvents (often mixtures of cyclic and linear carbonates) incurs exothermic decomposition of the electrolyte in the event of cell failure, often resulting in catastrophic thermal runaway. [4-6] While many approaches have been explored to address these issues, one of the most promising options is the elimination of the liquid electrolyte in favor of a solid electrolyte. [7] Transitioning from conventional liquid electrolytes to Li +conducting solid electrolytes (SEs) presents two primary advantages. The high mechanical rigidity of inorganic SEs may act to suppress the formation of dendrites at lithium anodes, reducing the possibility of internal short circuits. [8] Additionally, the negligible flammability of most SEs dramatically lowers the risk of uncontrolled thermal runaway in the event of cell failure. [9,10] These potential benefits motivate the search for materials with sufficiently high ionic conductivities to serve as replacements for their liquid counterparts. Among the known SE formulations, the thiophosphate class of superionic conductors exhibit exceptionally fast lithium transport at room temperature. [11] Specifically, Li 10 GeP 2 S 12 (LGPS) demonstrates an ionic conductivity of ≈10 mS cm −1 , comparable to conductivities achievable in conventional liquid electrolytes. [12] Despite the favorable ionic conductivity of LGPS, its poor chemical and electrochemical stabilities remain key challenges for practical application. The narrow window of electrochemical stability of LGPS and many other thiophosphate

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The multiphase flow inside a diesel injection nozzle is imaged using synchrotron X-rays from the Advanced Photon Source at Argonne National Laboratory. Through acquisitions performed at several viewing angles and subsequent tomographic reconstruction, in-situ 3D visualization is achieved for the first time inside a steel injector at engine-like operating conditions. The morphology of the internal flow reveals strong flow separation and vapor-filled cavities (cavitation), the degree of which correlates with the nozzle's asymmetric inlet corner profile. Micron-scale surface features, which are artifacts of manufacturing, are shown to influence the morphology of the resulting liquid-gas interface. The data obtained at 0.1 ms time resolution exposes transient flow features and the flow development timescales are shown to be correlated with in-situ imaging of the fuel injector's hydraulically-actuated valve (needle). As more than 98.5% of the X-ray photon flux is attenuated within the steel injector body itself, we are posed with a unique challenge for imaging the flow within. Time-resolved imaging under these low-light conditions is achieved by exploiting both the refractive and absorptive properties of X-ray photons. The data-processing strategy converted these images with a signal-to-noise ratio of ~ 10 into a meaningful dataset for understanding internal flow and cavitation in a nozzle of diameter 200 μm enclosed within 1-2 millimeters of steel.

The effects of jet fuel composition on ignition probability have been studied in a flowfield that is relevant to turbine engine combustors, but also fundamental and conducive to modeling. In the experiments, a spark kernel is ejected from a wall and propagates transversely into a crossflow. The kernel first encounters an air-only stream before transiting into a second, flammable (premixed) stream. The two streams have matched velocities, as verified by hot-wire measurements. The liquid fuels span a range of physical and chemical kinetic properties. To focus on their chemical differences, the fuels are prevaporized in a carrier air flow before being injected into the experimental facility. Ignition probabilities at atmospheric pressure and elevated crossflow temperature were determined from optical measurements of a large number of spark events, and high-speed imaging was used to characterize the kernel evolution. Eight fuel blends were tested experimentally; all exhibited increasing ignition probability as equivalence ratio increased, at least up to the maximum value studied (∼0.8). Statistically significant differences between fuels were measured that have some correlation with fuel properties. To elucidate these trends, the forced ignition process was also studied with a reduced-order numerical model of an entraining kernel. The simulations suggest ignition is successful if sufficient heat release occurs before entrainment of colder crossflow fluid quenches the exothermic oxidation reactions. As the kernel is initialized in air, it remains extremely lean during the initial entrainment of the fuel–air mixture; thus, richer crossflows lead to quicker and higher exothermicity.

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