Design of an additively manufactured hydraulic directional spool valve: an industrial case study

An industrial case study of an additively manufactured hydraulic spool valve that was designed in close collaboration with our industrial partner Wandfluh AG is presented herein. An existing conventional valve design was redesigned for laser powder bed fusion while considering the current functional and technical requirements. The entire development process is described based on real world requirements, considering the manufacturing and post-processing constraints. The final design was manufactured, tested, and compared with the conventionally manufactured valve. The pressure drop was reduced by 60% through the valve redesign, and a weight reduction of 50% was achieved. This study is concluded by reflecting the development process and identifying potential, learnings, and challenges that can be transferred to other hydraulic components. The importance of generating a large variety of concepts in the divergent design generation phase and performing computational fluid dynamics simulations to assess the potential of these concepts are highlighted

Design and fabrication of a stringer stiffened discrete-tube actively cooled panel for a hypersonic aircraft

A 0.61 x 1.22 m (2 x 4 ft) test panel was fabricated and delivered to the Langley Research Center for assessment of the thermal and structural features of the optimized panel design. The panel concept incorporated an aluminum alloy surface panel actively cooled by a network of discrete, parallel, redundant, counterflow passage interconnected with appropriate manifolding, and assembled by adhesive bonding. The cooled skin was stiffened with a mechanically fastened conventional substructure of stringers and frames. A 40 water/60 glycol solution was the coolant. Low pressure leak testing, radiography, holography and infrared scanning were applied at various stages of fabrication to assess integrity and uniformity. By nondestructively inspecting selected specimens which were subsequently tested to destruction, it was possible to refine inspection standards as applied to this cooled panel design

XHAB Microgravity Food Growth Chamber

NASA and other organizations are preparing to send humans deeper into space, including a NASA manned mission to Mars in the 2030s, in order to learn more about our universe and the origin of life and to ensure the survival of the human race. Long journeys in space require efficient, dependable, and sustainable methods to provide for astronauts\u27 metabolic needs such as oxygen, water, and food. In order for microgravity plant growth chambers to become a viable solution, several challenges encountered by past growth chambers must be resolved. One problem with existing space food growth chambers is hypoxia, or lack of oxygen, in the root zone, which decreases growth and causes epinasty and leaf chlorosis. Plant leaves produce oxygen and consume carbon dioxide through photosynthesis while roots consume oxygen and produce carbon dioxide through root respiration. Consequently, there are high levels of oxygen near the leaves and high levels of carbon dioxide near the roots. In microgravity, surface tension forces dominate. Instead of filling the pores from the bottom up, water tends to collect on the surface of the soil pores and trap air bubbles from which roots remove oxygen. Oxygen from the plant atmosphere is slow to diffuse into the water-trapped bubbles and the water doesn\u27t naturally drain from the pores without gravity. These factors prevent oxygen near the leaves from quickly diffusing to the roots and carbon dioxide and ethylene near the roots from diffusing out of the substrate. A method is needed to enable continuous quick gas diffusion between the leaf chamber and the root zone in space food growth chambers. Our project was to assess whether an additively manufactured lattice plant substrate composed of nylon facilitates gas diffusion between the leaf chamber and the root zone in a passively watered hydroponic space food growth chamber. In space, water collects on the sides of tubes first, leaving a column of air in the middle. We designed a substrate so that in space the columns would have the optimal balance of water and air for the plant roots. In order to test out design on Earth, we created a plant substrate lattice that has columns of various diameters. Water is then drawn upward at varying heights depending on the diameter of the substrate column. This creates spaces of water and air for the plant roots. We found the optimal column diameters through analytic calculations, simulations in the program HYDRUS, and experimental testing. We designed and built a complete microgravity food growth chamber and tested our substrate in it. Our growth chamber is passively watered. As plants absorb water from the substrate, the pressure difference causes water from the reservoir to naturally diffuse into the root zone. We planted mizuna in the substrate and it successfully grew for 30 days. We plan to continue experimental testing over the summer in order to further improve our substrate design

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

An investigation into miniature hydraulic actuation techniques for needle control on industrial knitting and sewing machines

The thesis is presented in four main parts: (1) the design and development of a hydraulic circular weft knitting machine; (2) the construction and testing of a hydraulic lockstitch sewing machine; (3) a detailed design study and analysis of pulse-generating rotary valves; (4) the design of a multi-feeder hydraulic circular weft knitting machine. Part 1 deals with the knitting machine aspect of the project consisting of verifying that a multi-actuator rotary valve system would operate with the desired time displacement profile, and in the correct sequence. This was then used as the basis for developing a ninety-six-needle, single feeder hydraulic circular weft knitting machine. This prototype machine was tested to obtain an assessment as to the advantages offered by hydraulic knitting techniques. Part 2 involved replacing the needle and thread take-up mechanisms of a lockstitch sewing machine, by two miniature hydraulic actuators, controlled by a rotary valve. The purpose of this machine was to prove that stitches could be formed successfully, thus demonstrating any beneficial features offered by hydraulic sewing devices. Part 3 deals with the detailed design study for pulse-generating rotary valves resulting from the previous applications. This valve was a new concept in valve technology and having established its definite potential, warranted the formation of a design procedure. The study outlines a method of optimising the torque required to rotate the bobbin by the construction of a mathematical model. Part 4 was concerned with designing a multi-feeder hydraulic circular weft knitting machine. This machine, controlled by an integrated actuator rotary collar valve to generate pulses, demonstrated how a series of twelve knitting time-displacement profiles could be created by ninety-six actuators positioned in a circular configuration. Thus, the research programme has been aimed at demonstrating how high speed motions, normally obtained by mechanical devices (cams, linkages) can be produced by miniature hydraulic actuation techniques. The feasibility of using these techniques has been verified by the building and testing of probably the first ever hydraulic knitting and sewing machines

Automotive Stirling Engine Development Program

Program status and plans are discussed for component and technology development; reference engine system design, the upgraded Mod 1 engine; industry test and evaluation; and product assurance. Four current Mod 1 engines reached a total of 2523 operational hours, while two upgraded engines accumulated 166 hours

Pressure losses in hydraulic manifolds

Hydraulic manifolds are used to realize compact circuit layout, but may introduce a high pressure drop in the system. Their design is in fact oriented more toward achieving minimum size and weight than to reducing pressure losses. This work studies the pressure losses in hydraulic manifolds using different methods: Computational Fluid Dynamic (CFD) analysis; semi-empirical formulation derived from the scientific literature, when available; and experimental characterization. The purpose is to obtain the pressure losses when the channels' connections within the manifold are not ascribable to the few classic cases studied in the literature, in particular for 90° bends (elbows) with expansion/contraction and offset intersection of channels. Moreover, since CFD analysis is used to predict pressure losses, general considerations of the manifold design may be outlined and this will help the design process in the optimization of flow passages. The main results obtained show how CFD analysis overestimates the experimental results; nevertheless, the numerical analysis represents the correct trends of the pressure losses

Guidelines to Select Between Self-Contained Electro-Hydraulic and Electro-Mechanical Cylinders

Author's accepted manuscript.acceptedVersio