Mechanical Engineering Commons^™

Aerodynamic Performance Characterization Of Leading Edge Protrusions On Small Propellers, Kevin Moore, Andrew Ning

Faculty Publications

The relatively large tubercles or protruding bumps on the leading edge of the humpback whale fin create counter-rotating chordwise vortices. At high Reynolds numbers, these vortices have been shown to delay stall with minimal effect on drag. The range of Reynolds numbers that these types of vortices form is unknown, and so an investigation of the potential for an increased envelope of operation for small aircraft propellers was done. For the cases tested in this report no benefits were observed. The addition of leading edge protrusions decreased propeller performance in both efficiency and thrust. Because of the inherent restrictions on …

Integration Of Advanced Stiffness-Reduction Techniques Demonstrated In A 3d-Printable Joint, Larry L. Howell, Ezekiel G. Merriam, Kyler A. Tolman

Faculty Publications

his work details the integration of three distinct methods for altering the stiffness of compliant joints: lattice flexures, compound joints, and static balancing. The methodology for applying these strategies is discussed in detail. Lattice flexures are a flexure modification that leads to low motion-direction bending stiffness. Compound joints improve a compliant joint’s load-carrying ability and off-axis stiffness. Static balancing in this case is achieved through the addition of an auxiliary energy storage device. To statically balance a compound lattice-flexured cross-axis flexural pivot, the load-dependent stiffness behavior of a cross-axis flexural pivot (CAFP) with two lattice flexure types is determined. A …

Compound Joints: Behavior And Benefits Of Flexure Arrays, Larry L. Howell, Ezekiel G. Merriam, Jason M. Lund

Faculty Publications

Because compliant mechanisms achieve their motion through deflection of flexible members, they have a limited range of motion and finite stiffness. Many common flexure geometries also suffer from a non-stationary center of rotation. These properties can be obstacles to their adoption in applications that require large displacements, low stiffness, or stationary centers of rotation. This work presents the concept of compound flexures: by assembling arrays of flexures, we can increase range of motion, decrease stiffness, and reduce center shift. We first develop the theory behind some of the basic behavior of compound joints. Then finite element analysis is used to …

Constructal Alkaline Membrane Fuel Cell (Amfc) Design, E. M. Sommer, J. V. C. Vargas, Lauber De Souza Martins, J. C. Ordonez

Faculty Publications

This paper introduces a structured procedure to optimize the internal structure (relative sizes, spacing) and external shape (aspect ratios) of a single alkaline membrane fuel cell so that net power is maximized. The optimization of flow geometry is conducted for the smallest (elemental) level of a fuel cell stack, i.e., the single alkaline membrane fuel cell, which is modeled as a unidirectional flow system. The polarization curve, total and net power, and efficiency are obtained as functions of temperature, pressure, electrolyte solution concentration (KOH), geometry and operating parameters. The optimization is subjected to fixed total volume. There are two levels …

Size-Controlled Large-Diameter And Few-Walled Carbon Nanotube Catalysts For Oxygen Reduction, Xianliang Wang, Qing Li, Hengyu Pan, Ye Lin, Yujie Ke, Haiyang Sheng, Mark T. Swihart, Gang Wu

Faculty Publications

We demonstrate a new strategy for tuning the size of large-diameter and few-walled nitrogen-doped carbon nanotubes (N-CNTs) from 50 to 150 nm by varying the transition metal (TM = Fe, Co, Ni or Mn) used to catalyze graphitization of dicyandiamide. Fe yielded the largest tubes, followed by Co and Ni, while Mn produced a clot-like carbon morphology. We show that morphology is correlated with electrocatalytic activity for the oxygen reduction reaction (ORR). A clear trend of Fe > Co > Ni > Mn for the ORR catalytic activity was observed, in both alkaline media and more demanding acidic media. The Fe-derived N-CNTs exhibited …

Rigidly Foldable Origami Gadgets And Tessellations, Thomas A. Evans, Robert J. Lang, Spencer P. Magleby, Larry L. Howell

Faculty Publications

Rigidly foldable origami allows for motion where all deflection occurs at the crease lines and facilitates the application of origami in materials other than paper. In this paper, we use a recently discovered method for determining rigid foldability to identify existing flat-foldable rigidly foldable tessellations, which are also categorized. We introduce rigidly foldable origami gadgets which may be used to modify existing tessellations or to create new tessellations. Several modified and new rigidly foldable tessellations are presented.

Effect Of Airfoil And Composite Layer Thicknesses On An Aerostructural Blade Optimization For Wind Turbines, Ryan Barrett, Ian Freeman, Andrew Ning

Faculty Publications

The purpose of this research is to enhance the performance of wind turbine blades by exploring the effect of adding airfoil and material layer thicknesses to the optimization design process. This is accomplished by performing an aerostructural blade optimization to minimize mass over annual energy production and thereby reduce the cost of energy. Changing airfoil thickness allows the airfoil shape to evolve as part of the optimization. The airfoil thicknesses are allowed to vary within two airfoil families, the TU-Delft and NACA 64-series, that are used in the NREL 5-MW reference turbine. Both experimental wind tunnel and computational data are …

Wind Farm Layout Optimization Using Sound Pressure Level Constraints, Eric Tingey, Jared Thomas, Andrew Ning

Faculty Publications

This project explored wind farm layout optimization using turbine acoustic and wake models. For two existing wind farms, the position of each wind turbine was optimized to maximize power output while constraining noise. Semi-empirical calculations were used for both the acoustic and wake models to predict how the turbine noise and wake disturbances propagated downstream. Turbine layout was optimized using a sequential quadratic programming optimizer called SNOPT. The optimization was able to constrain the noise level of the wind farms with a small impact on power output.

Comparison Of Two Wake Models For Use In Gradient-Based Wind Farm Layout Optimization, Jared Thomas, Eric Tingey, Andrew Ning

Faculty Publications

Wind farm layout has a significant impact on the productivity of a wind farm. To ensure that the turbines are placed in the most advantageous arrangement, optimization algorithms are often used during the layout design process. Depending on the wake model used for the optimization, optimizing the layout can be time intensive or potentially inaccurate. In this paper we present a comparison of optimization results using two simple wake models, the FLORIS model and the Jensen model. Results highlight some of the key similarities and differences of layout optimization results when different wake models are used.

Curved-Folding-Inspired Deployable Compliant Rolling-Contact Element (D-Core), Todd Nelson, Robert Lang, Spencer P. Magleby, Larry L. Howell

Faculty Publications

This work describes a deployable compliant rolling-contact element joint (DCORE joint) that employs curved-folding origami techniques to enable transition from a flat to deployed state. These deployable joints can be manufactured from a single sheet of material. Two fundamental configurations of the D-CORE are presented. The first configuration allows for motion similar to that of a Jacob’s ladder when the joint is in a planar state while achieving the motion of a CORE when in the deployed state. The second configuration constrains all degrees of freedom to create a static structure when the joint is in the planar state and …

High Aspect Ratio, Carbon Nanotube Membranes Decorated With Pt Nanoparticle Urchins For Micro Underwater Vehicle Propulsion Via H2O2 Decomposition, Kevin M. Marr, Bolin Chen, Eric J. Mootz, Jason Geder, Marius Pruessner, Brian J. Melde, Richard R. Vanfleet, Igor L. Medintz, Brian D. Iverson, Jonathan C. Claussen

Faculty Publications

The utility of unmanned Micro Underwater Vehicles (MUVs) is paramount for exploring confined spaces, but their spatial agility is often impaired when maneuvers require burst-propulsion. herein we develop high-aspect ratio (150:1), multi-walled carbon nanotube microarray membranes (CNT-MMs) for propulsive, MUV thrust generation by the decomposition of hydrogen peroxide (H₂O₂). The CNT-MMs are grown via chemical vapor deposition with diamond shaped pores (nominal diagonal dimensions of 4.5 × 9.0 [µm]) and subsequently decorated with urchin-like, platinum (Pt) nanoparticles via a facile, electroless, chemical deposition process. The Pt-CNT-MMs display robust, high catalytic ability with an effective activation energy …

Detect And Avoid For Small Unmanned Aircraft Systems Using Ads-B, Timothy Mclain, Laith R. Sahawneh, Matthew O. Duffield, Randall W. Beard

Faculty Publications

With the increasing demand to integrate unmanned aircraft systems (UAS) into the National Airspace System (NAS), new procedures and technologies are necessary to ensure safe airspace operations and minimize the impact of UAS on current airspace users. Currently, small UAS face limitations on their use in civil airspace because they lack the ability to detect and avoid other aircraft. This article presents a framework that consists of an Automatic Dependent Surveillance-Broadcast (ADS-B)-based sensor, track estimator, conflict/collision detection, and resolution that mitigates collision risk. ADS-B offers long-range, omni-directional intruder detection with comparatively few size, weight, power, and cost demands. The proposed …

Non-Dimensional Approach For Static Balancing Of Rotational Flexures, Ezekiel G. Merriam, Larry L. Howell

Faculty Publications

This work presents a nondimensional method for statically balancing flexural hinges, including those with stiffness that varies with load. Using a set of non-dimensional parameters, it is shown that one can quickly design a balancing mechanism for an idealized hinge/torsion spring system. This method is then extended to load-dependent systems, and is demonstrated with the design of a balanced cross-axis-flexural pivot with stiffness that varies as a function of compressive preload. A physical prototype is built and tested to verify the design method. The prototype demonstrates an average stiffness reduction of 87% over an 80 degree deflection range. The method …

Electrochemical Capture Of Co2 From Natural Gas Using A High-Temperature Ceramic-Carbonate Membrane, Jingjing Tong, Lingling Zhan, Jie Fang, Minfang Han, Kevin Huang

Faculty Publications

This study reports the first investigation of using a ceramic-carbonate dual-phase membrane to electrochemically separate CO₂ from a simulated natural gas. The CO₂ permeation flux density was systematically studied as a function of temperature, CO₂ partial pressure and time. As expected, the flux density was observed to increase with temperature and CO₂ partial pressure. Long-term stability test showed that flux density experienced an initial performance-improving “break-in” period followed by a slow decay. Post-test microstructural analysis suggested that a gradual loss of carbonate during the test could be the cause of the flux-time behavior observed.

Rigidly Foldable Origami Twists, Thomas A. Evans, Robert J. Lang, Spencer P. Magleby, Larry L. Howell

Faculty Publications

Rigid foldability is an important characteristic of origami structures that becomes significant with non-paper materials. A rigidly foldable origami tessellation is one where the sectors remain rigid and all deflection occurs at the crease lines. Many rigidly foldable patterns have only one degree of freedom, making them potentially useful for deployable structures. Methods have been developed to construct rigidly foldable origami tessellations using materials with finite thickness based on zero-thickness rigidly foldable patterns. [Tachi 11].

Origami methods have been considered for application in deployable structures such as solar panels [Miura 85] [Zirbel et al. 13] and sterile shrouds [Francis et …

Stabilizing Electrochemical Carbon Capture Membrane With Al2O3 Thin-Film Overcoating Synthesized By Chemical Vapor Deposition, Jingjing Tong, Fengzhan Si, Lingling Zhang, Jie Fang, Minfang Han, Kevin Huang

Faculty Publications

Development of high-efficiency and cost-effective carbon capture technology is a central element of our effort to battle the global warming and climate change. Here we report that the unique high-flux and high-selectivity of electrochemical silver-carbonate dual-phase membranes can be retained for an extended period of operation by overcoating the surfaces of porous silver matrix with a uniform layer of Al₂O₃ thin-film derived from chemical vapor deposition.

La0.7Sr0.3Fe0.7Ga0.3O3-Δ As Electrode Material For A Symmetrical Solid Oxide Fuel Cell, Zhibin Yang, Yu Chen, Chao Jin, Guoliang Xiao, Minfang Han, Fanglin Chen

Faculty Publications

In this research, La_0.7Sr_0.3Fe_0.7Ga_0.3O_3−δ (LSFG) perovskite oxide was successfully prepared using a microwave-assisted combustion method, and employed as both anode and cathode in symmetrical solid oxide fuel cells. A maximum power density of 489 mW cm⁻² was achieved at 800 °C with wet H₂ as the fuel and ambient air as the oxidant in a single cell with the configuration LSFG|La_0.8Sr_0.2Ga_0.83Mg_0.17O_3−δ|LSFG. Furthermore, the cells demonstrated good stability in H₂ and acceptable sulfur tolerance.

La0.6Sr1.4Mno4+Δ Layered Perovskite Oxide: Enhanced Catalytic Activity For The Oxygen Reduction Reaction, Yarong Wang, Zhibin Yang, Fanliang Liu, Chao Jin, Jiao Wu, Ming Shen, Ruizhi Yang, Fanglin Chen

Faculty Publications

Efficient electrocatalysts for the oxygen reduction reaction (ORR) is a critical factor to influence the performance of lithium–oxygen batteries. In this study, La_0.6Sr_1.4MnO_4+δ layered perovskite oxide as a highly active electrocatalyst for the ORR has been prepared, and a carbon-coating layer with thickness <5 nm has been successfully introduced to enhance the electronic conductivity of the as-prepared oxide. XRD, XPS, Raman, SEM and TEM measurements were carried out to characterize the crystalline structure and morphology of these samples. Rotating ring-disk electrode (RRDE) technique has been used to study catalytic activities of the as-prepared catalysts for the ORR in 0.1 M KOH media. RRDE results reveal that carbon-coated La_0.6Sr_1.4MnO_4+δ exhibits better catalytic activity for the ORR. For the carbon-coated La_0.6Sr_1.4MnO_4+δ, the ORR proceeds predominately via a direct four electron process, and a maximum cathodic current density of 6.70 mA cm⁻² at 2500 rpm has been obtained, …

Electrowetting Force And Velocity Dependence On Fluid Surface Energy, Qi Ni, Daniel E. Capecci, Nathan B. Crane

Faculty Publications

Electrowetting on Dielectric is a phenomenon in which the shape and apparent contact angle of a droplet changes when an electric field is applied across the droplet interface. If the field is asymmetric with respect to the droplet, then a net force can be applied to the droplet. In this work, we have measured the electrowetting force by confining the droplet shape beneath a glass plate and measuring the force on the plate. The force was measured as a function of voltage for a range of fluids with different surface energy. Measured forces show excellent agreement with predictions based on …

Development And Validation Of A New Blade Element Momentum Skewed-Wake Model Within Aerodyn, Andrew Ning, Greg Hayman, Rick Damiani, Jason Jonkman

Faculty Publications

Blade element momentum methods, though conceptually simple, are highly useful for analyzing wind turbines aerodynamics and are widely used in many design and analysis applications. A new version of AeroDyn is being developed to take advantage of new robust solution methodologies, conform to a new modularization framework for National Renewable Energy Laboratory’s FAST, utilize advanced skewed-wake analysis methods, fix limitations with previous implementations, and to enable modeling of highly flexible and nonstraight blades. This paper reviews blade element momentum theory and several of the options available for analyzing skewed inflow. AeroDyn implementation details are described for the benefit of users …

Stress-Limiting Test Structures For Rapid Low-Cost Strength And Stiffness Assessment, Andrew Katz, Craig P. Lusk, Nathan B. Crane

Faculty Publications

Purpose: Evaluate the use of a simple printed geometry to estimate mechanical properties (elastic modulus, yield strength) with inexpensive test equipment.

Design Methodology/Approach: Test geometry is presented that enables controlled strains with manual deformation and repeatable measurement of vibrational frequencies. This is tested with multiple FDM machines to assess measurement accuracy and repeatability. Printing orientation and some printing parameters are varied to assess the measurement sensitivity.

Findings: The test methods show good correlation with manufacturer material specifications in the X-Y plane and reported elastic strain limits. It is also sensitive to printing orientation and printing parameters.

Research Limitations/Implications: Further work …

Thick Rigidly Foldable Structures Realized By An Offset Panel Technique, Bryce Edmondson, Robert J. Lang, Michael R. Morgan, Spencer P. Magleby, Larry L. Howell

Faculty Publications

Rigid-panel origami is often mathematically modeled with idealized zero-thickness panels. When paper is used to realize an origami design, the zero-thickness models are a good approximation. However, many origami-inspired designs require the use of thicker materials that likely will not behave as the zero-thickness kinematic models predict.

The offset panel technique defined previously by the authors [Edmondson et al. 14] maintains the kinematics of a zero-thickness origami source model over its full range of motion. The offset panel technique accommodates uniform and varying panel thickness as well as offset panels or gaps between panels. The preserved kinematic behavior allows designers …

A Reversible And Stable Flake-Like Licoo2 Cathode For Lithium Ion Batteries, Tao Wei, Rui Zeng, Yongming Sun, Yunhui Huang, Kevin Huang

Faculty Publications

A dense and thick flake-like cathode structure was demonstrated to have a preferential crystallographic orientation for Li+ migration and a better tolerance to cracking, both of which enable a reversible and stable capacity at moderate rates from 0.1 to 2 C.

Flex-16: A Large-Displacement Monolithic Compliant Rotational Hinge, Robert Mcintyre Fowler, Alex Maselli, Peter Pluimers, Spencer P. Magleby, Larry L. Howell

Faculty Publications

This paper describes the design, analysis, and testing of a large-displacement monolithic compliant rotational hinge, called the Flex-16. The Flex-16 achieves 90 of rotation from monolithic construction and is aimed for application as a compliant satellite deployment hinge. Five prototypes were fabricated from three different materials (polypropylene, titanium, and a carbon nanotube framework) on two different size scales (macro and micro). A parametric finite element model was created to rapidly analyze a variety of design identified during a configuration study. Prototypes were tested for their ability to reach 90 of rotation without failure or self collision, and for their nonlinear …

Direct Synthesis Of Methane From Co2-H2O Co-Electrolysis In Tubular Solid Oxide Electrolysis Cells, Long Chen, Fanglin Chen, Changrong Xia

Faculty Publications

Directly converting CO₂ to hydrocarbons offers a potential route for carbon-neutral energy technologies. Here we report a novel design, integrating the high-temperature CO₂–H₂O co-electrolysis and low-temperature Fischer–Tropsch synthesis in a single tubular unit, for the direct synthesis of methane from CO₂ with a substantial yield of 11.84%.

Synthesis And Formation Mechanism Of Cuins2 Nanocrystals With A Tunable Phase, Chao Yu, Linlin Zhang, Long Tian, Dan Liu, Fanglin Chen, Cheng Wang

Faculty Publications

Chalcopyrite CuInS₂ (CIS) hierarchical structures composed of nanoflakes with a thickness of about 5 nm were synthesized by a facial solvothermal method. The thermodynamically metastable wurtzite phase CIS would be obtained by using InCl₃ instead of In(NO₃)₃ as In precursor. The effects of the In precursor and the volume of concentrated HCl aqueous solution on the phases and morphologies of CIS nanocrystals have been systematically investigated. Experimental results indicated that the obtained phases of CIS nanocrystals were predominantly determined by precursor-induced intermediate products. The photocatalytic properties of chalcopyrite and wurtzite CIS in visible-light-driven degradation of …

Biphilic Nanoporous Surfaces Enabled Exceptional Drag Reduction And Capillary Evaporation Enhancement, Xianming Dai, Fanghao Yang, Ronggui Yang, Xinyu Huang, William A. Rigdon, Xiaodong Li, Chen Li

Faculty Publications

Simultaneously achieving drag reduction and capillary evaporation enhancement is highly desired but challenging because of the trade-off between two distinct hydrophobic and hydrophilic wettabilities. Here, we report a strategy to synthesize nanoscale biphilic surfaces to endow exceptional drag reduction through creating a unique slip boundary condition and fast capillary wetting by inducing nanoscopic hydrophilic areas. The biphilic nanoporous surfaces are synthesized by decorating hydrophilic functional groups on hydrophobic pristine multiwalled carbon nanotubes. We demonstrate that the carbon nanotube-enabled biphilic nanoporous surfaces lead to a 63.1% reduction of the friction coefficient, a 61.7% wetting speed improvement, and up to 158.6% enhancement …

Host-Guest Interaction Dictated Selective Adsorption And Fluorescence Quenching Of A Luminescent Lightweight Metal-Organic Framework Toward Liquid Explosives, Dan Liu, Xiaojuan Liu, Yongxin Liu, Yang Yu, Fanglin Chen, Cheng Wang

Faculty Publications

In this article, we report the successful preparation of a Mg-based luminescent MIL-53 metal–organic framework (MOF), namely [Mg2(BDC)2(BPNO)]·2DMF (1) (BDC = 1,4-benzene dicarboxylate, BPNO = 4,4’- dipyridyl-N,N’-dioxide, DMF = N,N-dimethylformamide) in a mixed solvent containing a 2 : 3 volume ratio of DMF and ethanol (EtOH) under solvothermal conditions. Desolvated compound 1a can be used as an absorbent for selective adsorption and separation of liquid explosives, including nitroaromatic (nitrobenzene (NB)) and nitroaliphatic (nitromethane (NM) and nitroethane (NE)) compounds, through single crystal-to-single crystal (SC–SC) transformations. As one of the weakly luminescent MOFs, the luminescence of compound 1a could be quenched by …

A Simple Solution Method For The Blade Element Momentum Equations With Guaranteed Convergence, Andrew Ning

Faculty Publications

The blade element momentum equations, though conceptually simple, can be challenging to solve reliably and efficiently with high precision. These requirements are particularly important for efficient rotor blade optimization that utilizes gradient-based algorithms. Many solution approaches exist for numerically converging the axial and tangential induction factors. These methods all generally suffer from a lack of robustness in some regions of the rotor blade design space, or require significantly increased complexity to promote convergence. The approach described here allows for the blade element momentum equations to be parameterized by one variable: the local inflow angle. This reduction is mathematically equivalent, but …

Extended Formation Flight At Transonic Speeds, Andrew Ning, Ilan Kroo, Michael Aftosmis, Marian Nemec, James Kless

Faculty Publications

Aircraft flown in formation can realize significant reductions in induced drag by flying in regions of wake upwash. However, most transports fly at transonic speeds where the impact of compressibility on formation flight is not well understood. This study utilizes an Euler solver to analyze the inviscid aerodynamic forces and moments of transonic wing/body configurations flying in a two-aircraft formation. Formations with large streamwise separation distances (10-50 wingspans) are considered.

This work indicates that compressibility-related drag penalties in formation flight may be eliminated by slowing 2-3% below the nominal out-of-formation cruise Mach number (either at fixed lift coefficient or fixed …