191 research outputs found
Small scale cryogenic refrigeration technology
Issued as final reportVirtual Aerosurface Technologie
The Effects of Coolant Pipe Geometry and Flow Conditions on Turbine Blade Film Cooling
The performance of gas turbine engines can be improved by increasing the inlet gas temperature. Turbine blades can be damaged by high gas temperature, unless additional cooling mechanisms are incorporated to maintain the blades below an acceptable temperature limit. Film cooling techniques are often used to cool the blades to avoid damages. The performance of film cooling depends on several parameters, however. In this paper past research on film cooling is reviewed and areas in need of further investigation are identified. Computational fluid dynamics (CFD) simulations are then conducted on the widely-used single-hole film cooling arrangements in which coolant jets are injected into air flows inside a straight channel before issuing onto the blades. Cooling pipe-blade configurations and flow conditions are varied and the resulting flow hydrodynamics are examined. Counter rotating vortex pairs (CRVPs) formed in the flow strongly influence the film cooling performance. Small coolant inclination angles, exit holes enlargement in span wise direction, higher injected fluid density, and higher injectedambient fluid velocity ratios are all found to maintain the CRVPs away from each other and close to wall - both of which promote cooling. Pipe curvature can be used for enhancing cooling by exploiting the centrifugal force effect
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Microstructure and Mechanical Properties of Additively Manufactured Haynes 282: A Comparative Analysis between Laser Powder Bed Fusion and Laser Powder Directed Energy Deposition Technologies
This study compares the microstructure and tensile properties of Haynes 282 fabricated using laser powder
bed fusion and laser powder directed energy deposition. Both sets underwent stress-relieving, followed by hot
isostatic pressing, and the standard double aging heat treatment. Tensile testing was conducted at room
temperature on specimens fabricated with both technologies to evaluate and compare their tensile behaviors.
Results show that the ultimate tensile and yield strengths of laser powder bed fused specimens were 18% and
57% higher, respectively than those of laser powder directed energy deposited ones, whereas the elongation to
failure was similar in both. The difference in strengths is attributed to the differences in the size of Îł' precipitates
and grains, i.e., those in the laser powder directed energy deposited specimens being larger, whereas similar
elongation to failure is attributed to the carbide debonding dominating the fracture mechanism in both batches.Mechanical Engineerin
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Effect of heat treatment on the microstructure and mechanical properties of Monel K500 alloy fabricated via L-PBF and LP-DED
This study examines and compares the effect of different heat treatments (HT) on the microstructure
and mechanical properties of Monel K500 fabricated using laser powder bed fusion (L-PBF) and laser
powder directed energy deposition (LP-DED) technologies. The as-fabricated Monel K500 specimens
exhibited dendritic microstructure and elemental micro-segregation due to high cooling rates induced during
the fabrication process. The applicability of HT proposed in the literature for wrought Monel K500 was
investigated for L-PBF and LP-DED using four different HT procedures involving hot isostatic pressing
(HIP), solution annealing (SA), and aging. The mechanical properties of test specimens were evaluated
using uniaxial tensile testing at room temperature. The microstructural evolution of test specimens during
HT was analyzed using a scanning electron microscope. For all HT conditions investigated, L-PBF Monel
K500 specimens consistently displayed higher strength and lower ductility compared to the LP-DED
counterparts. The HT procedure involving HIP at 1160°C for 3hr at 100 MPa, SA at 1100°C for 15 min, and
three step aging at 610°C for 16 hr, 540°C for 6 hr, and 480°C for 8 hr resulted in highest strength for both
L-PBF and LP-DED fabricated Monel K500.Mechanical Engineerin
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A Comparison of Microstructure and Mechanical Performance of Inconel 718 Manufactured via L-PBF, LP-DED, and WAAM Technologies
The microstructure and mechanical properties of additively manufactured (AM) alloys can be significantly
affected by variations in cooling rates, resulting from different process conditions across different additive
manufacturing (AM) platforms. Therefore, it is crucial to understand the effect of manufacturing process on the
microstructure and mechanical properties of AM Inconel 718. This study examines three AM processes: laser
powder bed fusion, laser powder directed energy deposition, and wire arc additive manufacturing. Results show
that fully heat treated laser powder bed fused (L-PBF) and wire arc additively manufactured (WAAM) Inconel
718 specimens exhibit higher strength compared to laser powder directed energy deposited (LP-DED) ones due
to finer grain structure in L-PBF and retained dendritic microstructure in WAAM. The ductility in LP-DED
Inconel 718 was slightly higher compared to WAAM and L-PBF due to relatively small carbide size, which causes
stress concentration in a small material volume, leading to delayed fracture.Mechanical Engineerin
Energy conversion under conjugate conduction, magneto-convection, diffusion and nonlinear radiation over a non-linearly stretching sheet with slip and multiple convective boundary conditions
Energy conversion under conduction, convection, diffusion and radiation has been studied for MHD free convection heat transfer of a steady laminar boundary-layer flow past a moving permeable non-linearly extrusion stretching sheet. The nonlinear Rosseland thermal radiation flux model, velocity slip, thermal and mass convective boundary conditions are considered to obtain a model with fundamental applications to real world energy systems. The Navier slip, thermal and mass convective boundary conditions are taken into account. Similarity differential equations with corresponding boundary conditions for the flow problem, are derived, using a scaling group of transformation. The transformed model is shown to be controlled by magnetic field, conduction-convection, convection-diffusion, suction/injection, radiation-conduction, temperature ratio, Prandtl number, Lewis number, buoyancy ratio and velocity slip parameters. The transformed non-dimensional boundary value problem comprises a system of nonlinear ordinary differential equations and physically realistic boundary conditions, and is solved numerically using the efficient Runge-Kutta-Fehlberg fourth fifth order numerical method, available in Maple17 symbolic software. Validation of results is achieved with previous simulations available in the published literature. The obtained results are displayed both in graphical and tabular form to exhibit the effect of the controlling parameters on the dimensionless velocity, temperature and concentration distributions. The current study has applications in high temperature materials processing utilizing magnetohydrodynamics, improved performance of MHD energy generator wall flows and also magnetic-microscale fluid devices
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Z-inertial fusion energy: power plant final report FY 2006.
This report summarizes the work conducted for the Z-inertial fusion energy (Z-IFE) late start Laboratory Directed Research Project. A major area of focus was on creating a roadmap to a z-pinch driven fusion power plant. The roadmap ties ZIFE into the Global Nuclear Energy Partnership (GNEP) initiative through the use of high energy fusion neutrons to burn the actinides of spent fuel waste. Transmutation presents a near term use for Z-IFE technology and will aid in paving the path to fusion energy. The work this year continued to develop the science and engineering needed to support the Z-IFE roadmap. This included plant system and driver cost estimates, recyclable transmission line studies, flibe characterization, reaction chamber design, and shock mitigation techniques
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