In recent years, functional ceramic devices have become smaller, thinner, more refined, and highly integrated, which makes it difficult to realize their rapid prototyping and low-cost manufacturing using traditional processing. As an emerging technology, multi-material 3D printing offers increased complexity and greater freedom in the design of functional ceramic devices because of its unique ability to directly construct arbitrary 3D parts that incorporate multiple material constituents without an intricate process or expensive tools. Here, the latest advances in multi-material 3D printing methods are reviewed, providing a comprehensive study on 3D-printable functional ceramic materials and processes for various functional ceramic devices, including capacitors, multilayer substrates, and microstrip antennas. Furthermore, the key challenges and prospects of multi-material 3D-printed functional ceramic devices are identified, and future directions are discussed.
Concentration probes are employed in supersonic flow mixing measurements. Because the typical design of such probes is essentially based on an inviscid, adiabatic, quasi-1D analysis, the scope of this work is to understand better and quantify the severe impact of viscous effects on the probe's internal gasdynamics and the associated uncertainties in the measured quantities via a computational fluid dynamics analysis. Specifically, the focus is on the augmented errors due to the aforementioned viscous effects when coupled with various cases of probe-flow misalignment, which is a typical scenario encountered in mixing measurements of binary gas compositions (air and helium in the present work) in vortex-dominated flows. Results show phenomena such as shock induced boundary layer separation and the formation of an oblique shock train. These flow features are found to noticeably affect the accuracy of the composition measurement. The errors associated with the inviscid, adiabatic, quasi-1D analysis of the probes are quantified in this study.
The present work details the preliminary analysis and design of a model scramjet combustor intended to serve as a research platform for mixing and combustion studies in support of current non-reactive research. The shock tunnel located at the Aerodynamics Research Center of The University of Texas at Arlington, capable of producing test conditions simulating scramjet flight at Mach numbers ranging from ~5 to ~16 at altitudes of ~24 km to ~85 km, will serve as the test facility for the model combustor. Specifically, the modular design of the model scramjet combustor will allow for the study of supersonic combustion and flameholding characteristics of specific fuel injection strategies based on enhanced fuel-air mixing via pre-imposed selected modes of streamwise vortex interactions and consequent dynamics. In this paper, the fundamental requirements for the combustor design and the performance of the UTA hypersonic tunnel are discussed. A parametric sizing of the model combustor is utilized to define a suitable design that meets the specified requirements, and the inevitable constraints imposed by the limitation of ground testing facilities, discussed in the manuscript.
Nomenclature= Area γ = Specific heat ratio h = Enthalpy M = Mach number P = Pressure ψ = Combustor to freestream flight static temperature ratio ρ = Density η = Adiabatic compression efficiency T = Temperature t = time θ = Inlet compression angle u = Velocity Subscripts 1 = Driven condition 4 = Driver condition 5 = Stagnation condition c = Combustor condition e = Nozzle exit condition i = ignition r = reaction * = Throat condition ∞ = Freestream condition
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