bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance Comparison of Enthalpy Recovery Devices Using Liquid Desiccant and Desiccant Wheel
Authors: Zhang Tao , Liu Xiaohua , Xie Ying
Published: January 2020

Heat recovery between outdoor air and indoor exhaust air is an effective approach for energy-saving in the air-conditioning system. Performances of enthalpy recovery devices using liquid desiccant (LD) and desiccant wheel (DW) are compared in the present study. Effects of key factors including desiccant flow rate, number of transfer units (NTUm), and air inlet parameters on recovery performance are analyzed. There exists the same ideal recovery efficiency with a given NTUm for these two kinds of devices. However, an optimal solution flow rate could be achieved for enthalpy recovery device using LD, while a higher rotation speed leads to a higher recovery efficiency for that using DW. Recovery efficiencies of the two devices increase with the increase in NTUm, while they have different ranges of NTUm. NTUm of the DW is usually superior to that of the LD, due to the material difference. Then, the optimum methods to improve recovery efficiency of the two devices are clarified, i.e., increasing NTUm for an enthalpy recovery device using LD and choosing a reasonable rotation speed for that using DW, respectively. The present research will be beneficial to cast light on the relation between enthalpy recovery devices using LD and DW.
Experimental Investigation on Turning of Monel K500 Alloy Using Nano Graphene Cutting Fluid Under Minimum Quantity Lubrication
Authors: Kulandaivel Arul , Santhanam Senthil Kumar
Published: January 2020

Turning operation is one of the most commonly used machining processes. However, turning of high strength materials involves high heat generation which, in turn, results in undesirable characteristics such as increased tool wear, irregular chip formation, minor variations in physical properties etc. In order to overcome these, synthetic coolants are used and supplied in excess quantities (flood type). The handling and disposal of excess coolants are tedious and relatively expensive. In this proposed work, Water Soluble Cutting Oil suspended with nanoparticles (Graphene) is used in comparatively less quantities using Minimum quantity lubrication (MQL) method to improve the quality of machining. The testing was done on Turning operation of Monel K500 considering the various parameters such as the cutting speed, feed and depth of cut for obtaining a surface roughness of 0.462μm and cutting tool temperature of 55°C for MQL-GO (Graphene oxide) process.
Enhancement of Drying Rate of Moist Porous Media With Electrohydrodynamically Assisted Slot Jet Reattachment Nozzle: A Numerical Study
Authors: Yang Mengqiao , Yagoobi Jamal , Tilley Burt
Published: January 2020

Drying of moist porous media, such as food or pulp and paper, is an energy-intensive process. Innovative impinging jet nozzles, for instance, radial jet reattachment (RJR) and slot jet reattachment (SJR) nozzles, have been proved to be one of the efficient methods to enhance the drying rate compared to traditional in-line jet and slot jet nozzles. However, the heat and mass transfer in the region immediately underneath these nozzles are relatively inefficient. In this work, the performance of the SJR nozzle is improved by the application of electrical field, specifically, ionic wind generated in the region directly between the nozzle exit and the exposed surface of moist porous material. The numerical model is based on the coupled flow field generated by electrohydrodynamically (EHD) assisted SJR nozzle with the heat and mass transfer taking place within the moist porous media during the drying process. The simulation results show a significant secondary flow induced under the nozzle due to the ionic wind. Up to 40% drying rate enhancement has been achieved. However, the enhancement of drying rate diminishes as the air exit velocity exceeds a certain threshold. The simulation results illustrate the detailed fundamental understanding of this conjugated problem and provide a foundation for the enhancement of convective drying of moist porous materials.
Thermoelastic Response of Functionally Graded Fiber-Reinforced Rotating Disk With Non-Uniform Thickness Profile Under Variable Angular Velocity
Authors: Nayeb-Hashemi Hamid , Zheng Yue , Vaziri Ashkan , Olia Masoud
Published: January 2020

Displacement and stress fields in a functionally graded (FG) fiber-reinforced rotating annular disk with a non-uniform thickness profile, subjected to angular deceleration and a temperature profile were investigated. Unidirectional fibers were considered to be circumferentially distributed within the disk with fiber volume fraction changing radially. The governing equations for displacement, stress, and temperature fields were solved using finite difference method. The results indicated that thermal induced stresses were more dominate than the rotational induced stresses. Disks which were fiber rich at the inner radius, the fibers made negligible difference on the displacement and stress fields when compared to a homogenous disk made from the matrix material. In addition, it was found that the deceleration magnitude had no effect on the radial and hoop stresses, nor the temperature on the developed shear stress. The shear stress was only affected by the disk deceleration. Tsai-Wu failure criterion was applied for decelerating disks to ascertain their failure behavior. The results show that Tsai-Wu failure index is dominated by the thermal stresses.
Fabrication and Characterization of the Recycling of Composite Palm Materials, Shell, Leaves and Branches in Saudi Arabia
Authors: Alhummidy G. Almotery Khaled , Saeed M. Alsaiari Waleed , Abdulrahman Y. Alyoussef Yazeed , Farraj M. Alsahli Mohammad , Mohammed O. Alharbi Meshal , M. A. A. El-Bagory Tarek , Alarifi Ibrahim M.
Published: January 2020

Palm wood can be classified into three categories: leaves, branches and core-shell, and all of these were studied. Recycled composite materials are promising in the innovation field since some microstructures have unique characterization and noble applications. The micro mill used grinded the recycled materials into micro size particles approximately 20μm. SEM + EDX spectroscopy was used to analyze and indicate the morphology of the micro particle composite material’s composition content. The SEM results demonstrate the composite homogeneity. XRD analysis was conducted and showed the structural properties of the recycled composite materials examined. The recycled material was transferred into micro size particles encased by the properties of resin mixed with epoxy, this led to promising composite materials. FITR spectroscopy analysis revealed a distinct interaction between the polymer chain and the band positions. The mechanical analysis was conducted based on the recycled materials’ application. The mechanical properties were observed during the tests and reflected in the structure of the material and its uses. This project aimed to determine the possibility of efficiently recycling composite. The significant increase in demand around the world, and the increased use of composite materials in different industries, has consequently led to positive results for the production waste.
Analytical and Numerical Modeling of Soil Cutting and Transportation During Auger Drilling Operation
Authors: Abdeldayem Mohamed A. A. , Mabrouk Mohamed H. , Abo-Elnor Mootaz
Published: January 2020

Soil drilling operation has become one of the most important interest to researchers due to its many applications in engineering systems. Auger drilling is one of the ideal methods in many applications such as pile foundation engineering, sampling test for geological sciences and space. However, the dominant factor in determination of drilling parameters is real drilling operations experience, which may cause transportation blocking of chips that leads to accidents. As a result, soil drilling process using auger drilling is studied to obtain the controlling parameters and to optimize these parameters to improve drilling performance which enables proper selection of machine for a required job. One of the main challenges that faces researchers during using of modelling techniques to define the soil drilling problem is the complex nonlinear behaviour of the drilled medium itself due to its discontinuity and heterogeneous formation. This paper presents two models that can be used to predict the total resistive forces which affect the auger during soil drilling operation. The first proposed model discusses the problem analytically in a way that depends on empirical data that can be collected from previous experience while the second model discusses the problem numerically with less depending on empirical experienced data. The analytical model is developed using Matlab® interface while the numerical model is developed using discrete element method via EDEM® software. A simplified auger drilling machine is built in the soil-tool interaction laboratory, Military Technical College to obtain experimental results that can be used to verify the presented models. Data acquisition measuring system is established to obtain experimental results using a Labview® program. This program enables displaying and recording the measured data collected mainly from transducers planted in the test rig. Both Analytical and numerical models results are compared to experimental values to aid in developing the presented parametric study that can be used to define the working parameters during drilling operations in different types of soils.
Modeling and Simulation of Thermal Energy Storage for Solar Energy Utilization
Authors: Alnaimat Fadi , Mathew Bobby , I. Mourad Abdel-Hamid , Al Omari S.-A. B.
Published: January 2020

A significant research has been done on the enhancement of thermal energy storage systems. This article details the numerical study conducted to understand the heat transfer and fluid flow characteristics of a concentric thermal energy storage subjected to different heat transfer fluid (HTF) velocities. Water is used as the working heat transfer fluid. The influence of flow parameter primarily the HTF velocity is studied in this article. Studies are conducted for concentric thermal energy storage diameter of 25 mm, and 10 mm inner diameter of concentric pipe, 200 mm length, and HTF velocity of 0.02, 0.1, 0.3, 0.5 m/s. It is found that the utilization of fins improves the heat transfer in tube in tank thermal storage system. Computational fluid dynamics (CFD) enables a more detailed study of the phase change thermal characteristics.
Scaling Behavior in Electrohydrodynamic Jetting of Polymeric Solutions
Authors: Singh Abhishek K. , Dubey Kaushlendra , Srivastava Rajiv K. , Bahga Supreet Singh
Published: January 2020

An electrohydrodynamic (EHD) jet forms when a leaky-dielectric liquid issuing out of a needle is accelerated and stretched by electrostatic forces. Stability and scaling behavior of the EHD jet of polymeric solutions depend on electrostatics, fluid mechanics and rheology of the liquid. While EHD jetting of Newtonian liquids have been described in the literature, the effect of non-Newtonian rheology on EHD jetting is still not well-understood. Therefore, we present a detailed experimental investigation of the stability and scaling behavior of EHD jets of polymeric solutions that exhibit non-Newtonian flow behavior. The stability of cone-jet was analyzed by varying flow rate, electric field and polymer concentration. Experiments were performed for polymeric solutions of polycaprolactone (PCL) dissolved in acetic acid. Our experiments show that non-Newtonian viscoelastic behavior can significantly alter the stability characteristics of the EHD jet. We have found that increase of elasticity of polymeric solutions results in enhanced jet stability. Finally, we present the dependence of experimentally measured diameter dj of the EHD jet on the flow rate Q. Experimentally measured diameter of the EHD jet scales as dj ∼ Q0.65 for both Newtonian and non-Newtonian viscoelastic liquids, which can be attributed to dominant inertia forces in our experiment.
Production and Analytics of a Multi-Linked Robotic System
Authors: Rykkje Thorstein R. , Gulbrandsen Eystein , Hettervik Andreas Fosså , Kvalvik Morten , Gangstad Daniel , Tislevoll Torgeir Oliver , Aasebø Stefan , Osberg Daniel Vatle
Published: January 2020

This paper extends research into flexible robotics through a collaborative, interdisciplinary senior design project. This paper deploys the Moving Frame Method (MFM) to analyze the motion of a relatively high multi-link system, driven by internal servo engines. The MFM describes the dynamics of the system and enables the construction of a general algorithm for the equations of motion. Lie group theory and Cartan’s moving frames are the foundation of this new approach to engineering dynamics. This, together with a restriction on the variation of the angular velocity used in Hamilton’s principle, enables an effective way of extracting the equations of motion. The result is a dynamic 3D analytical model for the motion of a snake-like robotic system, that can take the physical sizes of the system and return the dynamic behavior. Furthermore, this project builds a snake-like robot driven by internal servo engines. The multi-linked robot will have a servo in each joint, enabling a three-dimensional movement. Finally, a test is performed to compare if the theory and the measurable real-time results match.
Stability Measures and Criteria for Autonomous Mobile Robotic Platforms: Analysis, Comparison and Numerical Evaluation
Authors: Nazem Tahmasebi Kaveh , Belotti Roberto , Vidoni Renato , Von Ellenrieder Karl
Published: January 2020

The tip-over instability of an autonomous mobile robot is a significant problem as it can diminish its maneuverability and increase the possibility of damaging the robot and its surrounding environment. For these reasons, it is important to define the stability margin and predict the edge of the tip-over instability considering different robot specifications and environmental conditions. Different stability measures have been developed to evaluate and analyze robot stability margins for diverse conditions. In this work, the Zero Moment Point, Energy Stability Margin, Force-Angle Stability Measure, and Mass-Moment Height Stability Measure methods are considered and applied to different mobile robot architectures including three-wheeled, four-wheeled (with rectangular and trapezoidal base surface) and articulated systems. The stability margins are discussed considering the four different stability criteria and evaluating the effect of a sloped surface. Then, the sensitivity of the tip-over instability in relation to the variation of the center of mass height as an important robot configuration parameter is evaluated. Finally, after a theoretical extension of the Force-Angle Stability and Mass-Moment Height stability measurement methods, the articulated mobile robot’s stability margin is considered and evaluated.
Numerical Investigation of Combined Sensible/Latent Heat Thermal Energy Storage With Supercritical Carbon Dioxide As Heat Transfer Fluid at 650°C
Authors: Osterman Kelly , Guillen Diego , Goswami D. Yogi
Published: January 2020

This paper numerically explores a high-temperature sensible-latent hybrid thermal energy storage system designed to store heat with output temperatures stabilized at approximately 550–600 °C for direct coupling with supercritical carbon dioxide (sCO2) power cycles operating at their design point. sCO2 and dry air at 25 MPa are used as heat transfer fluid (HTF) in a packed bed storage system that combines rocks as sensible heat storage and AlSi12 as latent heat storage. The base model using dry air at atmospheric pressure is compared to similar work done at ETH Zurich; the model is then extended for use with sCO2 to compare the performance of air and sCO2 at similar volumetric flow rates. It was found that sCO2 is capable of storing a significantly larger amount of energy (∼40 kWh) in the same time period as the air system (∼19 kWh), and can discharge that energy much quicker (1.5 hours compared to 4 hours). However, in order to achieve similar degrees of temperature stabilization, the total height of PCM had to be increased significantly, from 9 cm to 45 cm or more.
Three-Dimensional Modeling of Reduced Material Properties in Ceramics With Added Porosity
Authors: Wimmer Stephanie A. , DeGiorgi Virginia G. , Gorzkowski Edward P. , Ryou Heonjune
Published: January 2020

Manufacturing methods to create ceramic coatings with tailored thermal conductivity are crucial to the development of thermal protection systems for many components including turbine blades in high temperature engines. A designed microstructure of grains, pores, and other defects can reduce the thermal conductivity of the ceramic. However, the same microstructure characteristics can reduce mechanical properties to the point of failure. This work is part of a larger program with the goal of optimizing ceramic coating microstructure for thermal protection while retaining sufficient mechanical strength for the intended application. Processing parameters have been examined to identify methods designed to maintain a nano-sized grain structure of yttria-stabilized zirconia while controlling the added porosity with a specific shape and size. In this paper computational modeling is used to evaluate the effects of porosity on coating performance, both thermal and structural. Coating porosity is incorporated in the computational models by randomly placing empty spaces or defects in the shape of spherical voids, oblate pores, or penny cracks. In addition to computational modeling, prototype coatings are developed in the laboratory with specific porosity. The size and orientation of defects in the computational modeling effort are statistically generated to match experiments. The locations of the defects are totally random. Finite element models are created which include various levels of porosity to calculate effective thermal and mechanical properties. Comparisons are made between three-dimensional finite-element simulations and measured data. The influences of pore size as well as three dimensional computational modeling artifacts are examined.
Non-Invasive Tracking of Micro-Scale Microrobot Using Photoacoustic Imaging
Authors: Yan Yan , Carey Zachary , Mehrmohammadi Mohammad , Jing Wuming
Published: January 2020

This paper presents the innovative integration of both frontier submillimeter magnetic microrobot and integrated ultrasound and photoacoustic (USPA) imaging. The integrative technique will allow for potential real non-invasive microrobot operation in deep biological tissue for biomedical applications. In this study, the magnetic microrobot prototypes are fabricated in series of different sizes through patterning SU-8 photoresist mixed with nickel particles. In order for proof-of-concept, the magnetic microrobot is actuated by a static magnetic field, which is produced by a multiple magnet cone array. As mimicking the opaque biological environment, the magnetic microrobot is placed in a fluid environment bounded by a non-transparent phantom. The USPA imaging system consists of a laser system to illuminate working space and an ultrasound system to receive the acoustic signal generated by imaging object due to photonic signal absorption. The experimental tests prove that the USPA imaging protocol can detect single microrobot smaller than 100 μm through the 15 mm thick opaque phantom. The imaging test has been accomplished both statically and in a motion of approximately 2.0 mm/s. Further investigation of this concept will focus on the collaboration of photoacoustic imaging and magnetic manipulation of microrobot under real biological fluid media.
Effect of Particle Breakage on Explosibility of Coal/Rock Dust Mixtures due to Dispersion in 20-L Chambers
Authors: Rayyan Naseem , Perera Inoka E.
Published: January 2020

Research has shown that particle size has a significant impact on the explosibility of coal dust/rock dust mixtures. Previous explosion studies conducted using the U.S. Bureau of Mines’ (BOM) 20-L explosion chamber tend to show a difference in the amount of inerting material needed to prevent an explosion when compared to the 20-L Siwek chamber. To reconcile these differences, samples were comparatively tested in the historic BOM 20-L chamber and the new NIOSH 20-L Siwek chamber with an emphasis on particle breakage. Rock dust and coal dust samples were dispersed in the chambers without ignitors and their specific surface areas were compared to the undispersed specific surface areas in order to quantify the breakage. Then, rock dust and coal dust mixtures were prepared, dispersed using the Siwek chamber, collected and tested for explosibility in the BOM 20-L chamber to see if the severe particle breakage in the Siwek chamber would influence the inerting limits of the BOM chamber. Results indicate that the particle breakage of friable brittle materials during explosion testing should be considered when evaluating the explosion risks in the process industries.
Experimental and Numerical Investigations of Pressure Loss and 3-D Flow Separations in a Linear Compressor Cascade
Authors: El-Shahat Saeed A. , El-Batsh Hesham M. , Attia Ali M. A. , Li Guojun , Fu Lei
Published: January 2020

Flow separation is a major parameter affecting the compressor performance. It reduces the compressor efficiency, limits static pressure rise capability and contributes to instability in compressors. In applied research, there is a lack of understanding of the nature and mechanism of the three-dimensional (3-D) flow separation in the axial compressor especially on the juncture of the endwall and blade corner region. In the present study, the 3-D flow field in an axial compressor cascade has been studied experimentally as well as numerically.

For the experimental study part, a linear compressor cascade has been installed in an open loop wind tunnel. The experimental data was acquired for a Reynolds number Rec = 2.98 × 105 based on the blade chord and the inlet flow conditions. The total pressure loss progress through the blade passage has been measured by using calibrated five and seven-hole pressure probes connected to ATX sensor module data acquisition system. The static pressure distribution on the endwall has been measured employing static pressure taps connected to digital micromanometers. To investigate the loss mechanism through the cascade, the total pressure loss coefficient has been calculated from the measured data.

The computational fluid dynamics (CFD) study of the flow field was performed to gain a better understanding of the flow features. Two turbulence models, Spalart-Allmaras (S-A) and shear stress transport SST (k-ω) were used. From both parts of study, the flow field development and total pressure loss progress through the cascade have been investigated and compared. Moreover, the received data demonstrated a good agreement between the experimental and computational results. The predicted flow streamlines by numerical calculations showed regions characterized by flow separation and recirculation zones that could be used to enhance the understanding of the loss mechanism in compressor cascades. All measurements taken by 5-hole and 7-hole pressure probes have been analyzed and compared. It was found that their readings were almost the same and there are no excellences for using 7-hole probe. Furthermore S-A turbulence model calculations showed more consistencies with experimental results than SST (k-ω) model.
Effect of Processing Technique on the Mechanical Properties of a Functionalized Superhydrophobic Silane
Authors: Baruwa Akinsanya Damilare , Akinlabi Esther Titilayo , Oladijo O. P. , Dutta-Majumdar Jyotsna , Krishna Shree
Published: January 2020

The need to test for the durability and capability of a coating before being subjected to service is highly important for engineering applications. Ultra-low indentation of nano-hardness and nano-scratch are valuable methods of measuring durability and near-surface mechanical properties of thin films. AISI 304 stainless steel was coated with Repellix superhydrophobic coating using chemical vapor deposition (CVD) and atomic layer deposition (ALD) techniques at constant processing parameters. The deposited films were characterized through nanoindentation, nanoscratch, and water contact angle to establish the effect of coating technique on the mechanical properties of the thin films. The results established that the ALD deposition technique has better hardness but less wear resistance when compared to the sample produced using the CVD method. ALD also showed to have a lower contact angle in comparison with a coating deposited by CVD. Overall, it is expected that the substrate coated by CVD would outperform samples produced via ALD as regards to typical applications where good wear and corrosion resistance are required.
Recycling Lithium-Ion Battery: Mechanical Separation of Mixed Cathode Active Materials
Authors: Al-Shammari Hammad , Esmaeeli Roja , Aliniagerdroudbari Haniph , Alhadri Muapper , Hashemi Seyed Reza , Zarrin Hadis , Farhad Siamak
Published: January 2020

Lithium-ion batteries (LIBs) have driven the industry of rechargeable batteries in recent years due to their advantages such as high energy and power density and relatively long lifespan. Nevertheless, the dispose of spent LIBs has harmful impacts on the environment which needs to be addressed by recycling LIBs. However, none of the currently developed recycling processes is economical. The physical recycling process of LIBs may be economical if the cathode active materials can be separated, regenerated, and reused to make new LIBs. However, the first barrier for regeneration and reusing is the separation of different types of spent cathode active materials in the filter cake that are mixed with each other and come in the form of very fine powders with various sizes (< 30 μm) from the physical recycling process. The aim of this study is to separate the mixture of cathode active materials by adopting Stokes’ law. The focus will be only on mechanical separation with no thermal or chemical separation methods. For the validation, an experiment was designed and successfully performed where different types of spent cathode materials (e.g., LiCoO2, LiFePO4, and LiMn2O4) were separated from the spent anode materials (e.g., graphite) with high efficiency and reasonable time.
A Novel Ferrofluid-Based Valve-Less Pump
Authors: Michelson Trevor , Rudnick Joshua , Baxter Joshua , Rashidi Reza
Published: January 2020

This paper demonstrates the development of a fluidic pump, magnetically actuated by a ferrofluid through a circular channel. The pump has a rotary design with a tangential input and output. It is designed to house a magnet to create a ferrofluid plug in one place between the inlet and outlet. There are two magnets outside of the housing attached to a rotating apparatus that move the ferrofluid around. The ferrofluid then moves around the channel, taking in and moving water through the channel towards the outlet. The pump was fabricated using a 3D printing technique. The pump was tested at three different configurations at a zero back pressure including single small moving magnet, double small moving magnet and single large moving magnet. The volumetric flow rate was measured at different rotational speeds from 9.375 rpm to 25 rpm. The highest average flow rate measured was 0.8 ml/min at 25 rpm with a single large magnet. This pump can be used for a circuit board cooling device; the pump would deliver a coolant through miniature tubes to cool the system.
Influence of Blending Hydrogen and Biogas Into Natural Gas on the Combustion Performance of a Tankless Water Heater
Authors: Zhao Yan , Morales David , McDonell Vincent
Published: January 2020

Utilizing renewable gases including biogas and renewable hydrogen instead of natural gas helps reduce greenhouse gases from fossil fuel combustion. Due to the fuel property variation, it is not practical to replace pipeline natural gas with these renewable fuels while still keeping the combustion devices at its designed operating condition. Therefore, this study mixes renewable hydrogen and simulated biogas into pipeline natural gas and investigates the combustion performance of a commercial tankless water heater. Up to around 10 vol% carbon dioxide and 20 vol% hydrogen are mixed into natural gas, then the mixtures are supplied to the water heater. Appliance performance such as operability, emissions (CO, UHC, NO, NO2, N2O, NH3) and efficiency are examined. The feasibility of injecting renewable gases into the existing natural gas infrastructure is evaluated from the perspective of the representative tankless water heater performance. The results show a positive sign for mixing hydrogen into pipeline natural gas, due to the small variation of the water heater emissions and an increase of the efficiency.
2D and 3D Stability of Cavity Flows in High Mach Number Regimes
Authors: Doshi Parshwanath S. , Ranjan Rajesh , Gaitonde Datta V.
Published: January 2020

The stability characteristics of an open cavity flow at very high Mach number are examined with BiGlobal stability analysis based on the eigenvalues of the linearized Navier-Stokes equations. During linearization, all possible first-order terms are retained without any approximation, with particular emphasis on extracting the effects of compressibility on the flowfield. The method leverages sparse linear algebra and the implicitly restarted shift-invert Arnoldi algorithm to extract eigenvalues of practical physical consequence. The stability dynamics of cavity flows at four Mach numbers between 1.4 and 4 are considered at a Reynolds number of 502. The basic states are obtained through Large Eddy Simulation (LES). Frequency results from the stability analysis show good agreement when compared to the theoretical values using Rossiter’s formula. An examination of the stability modes reveals that the shear layer is increasingly decoupled from the cavity as the Mach number is increased. Additionally, the outer lobes of the Rossiter modes are observed to get stretched and tilted in the direction of the freestream. Future efforts will extend the present analysis to examine current and potential cavity flame holder configurations, which often have downstream walls inclined to the vertical.
Advanced Calculation Flutter Procedure Developed for Ultra-Long Last Stage Blades for Steam Turbines
Authors: Slama Vaclav , Rudas Bartolomej , Macalka Ales , Ira Jiri , Zivny Antonin
Published: January 2020

An advanced in-house procedure, which is based on a commercial numerical code, to predict a potential danger of unstalled flutter has been developed and validated. This procedure using a one way decoupled method and a full-scale time-marching 3D viscous model in order to obtain the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations in the time domain thus calculate an aerodynamic work and a damping ratio is used as an essential tool for developing ultra-long last stage rotor blades in low pressure turbine parts for modern steam turbines with a large operating range and an enhanced efficiency. An example is shown on a development of the last stage blade for high backpressures.
Effect of Graphene Nanoplatelets Incorporation on Microstructural and Tribological Properties of Aluminium Metal Matrix Composites
Authors: Sharma Ankit , Priyadarshini Amrita , Sujith Ravindran , Subrahmanyam M. V. Sankara , Thomas P. Alen , Gupta Amit Kumar
Published: January 2020

Aluminium metal matrix composites exhibiting superior mechanical and tribological properties have gained immense interest in recent years. These comosites are finding broad applications in the fields of automotive, aerospace, military and marine. Graphene Nanoplatelets (GNPs), as reinforcement in composites, have become a prime focus because of its exceptional characteristic properties. In the present study, GNPs are dispersed into the aluminium alloy as reinforcements by using stir casting method. To ensure proper dispersion, sintered pellets of aluminium mixed with GNPs are added to the molten metal. The dispersion of the GNPs and the microstructural changes due to the addition of GNPs are observed using Scanning Electron Microscopy (SEM) and elemental mapping. Vickers hardness tester is used to measure hardness of these samples. To compare the tribological properties of Al/GNP composite as well as pure alumimum samples, pin-on-disc experiments are conducted for a specific combination of sliding speed and sliding distance at different loading conditions. The weight loss, wear rate and coefficient of friction are measured and favourable effects of GNPs on tribological properties of Al/GNP composite are discussed. In addition, the wear mechanism has been understood in detail by conducting microstructural studies of the worn surfaces using SEM and Energy Dispersive Spectroscopy. It is observed that the Vickers hardness of the composite increased to a maximum of 25% while coefficient of friction decreased to a minimum of 26% for Al/GNP composite.
Investigating the Micro-EDM Machinability of Bulk Metallic Glass in Micro-EDM Drilling
Authors: Liu Chong , Rashid Asif , Jahan Muhammad P. , Ma Jianfeng
Published: January 2020

Bulk Metallic Glass (BMG) is a solid metallic material with disordered atomic structure, that has the characteristics of high elasticity, hardness, fracture toughness, and superior corrosion resistance. High aspect ratio micro-through holes on BMG has prospective applications in space, nuclear reactor, thermodynamics engineering, biomedical, and electronics industries. In this study, the micro-EDM machinability of BMG (Vit 1b: Zr67Cu10.6Ni9.8Ti8.8Be3.8 (wt%)) is evaluated. The micro-EDM machinability of BMG has been assessed based on the volume of material removal rate (MRR), tool wear rate (TWR), micro-hole surface quality, and dimensional accuracy. The effect of various electrical and non-electrical parameters is studied. It is found that micro-EDM is capable producing high aspect ratio micro-holes on difficult-to-machine BMG. The deposition of resolidified debris around the edge of the micro-holes, both at the entrance and exit side, are found to be a common phenomenon in micro-EDM of BMG. The reduction of capacitance was found to be the effective way for reducing the resolidified debris around the edges. Capacitance was found to be have more pronounced effect, with gap voltage having little effect on the quality of micro-holes. The electrode rotational speed had insignificant effect on the quality of micro-holes. In terms of dimensional accuracy, which was measured by overcut and taper angle, both the gap voltage and electrode rotational speed had little effect. The lower electrode rpm was found to reduce the taperness of the micro-holes, although the material removal rate decreases and tool wear rate increases. Finally, analysis of the composition of tool electrode before and after machining indicates the migration of materials from the dielectric and workpiece to the tool electrode and vice versa.
Irregular Shape Optimization for the Film Cooling Nozzle of Gas Turbines Using Numerical Optimization Tool
Authors: Alshehaby Mohammad M. , El-Gabry Lamyaa
Published: January 2020

Film cooling, along with other approaches, is well known to be an important technique for preserving the integrity of turbine blades against high temperature gases. Accordingly, continuous enhancement of film cooling performance is still one of the gas turbines community’s interests. The coolant nozzle geometry, as an important parameter controlling the film cooling behavior, has been yielded to close test in the current study seeking for the optimum one that gives best cooling performance in terms of adiabatic film effectiveness and heat transfer coefficient at blowing ratio of one. An experimentally validated model, realizable k-ε model with scalable wall function, has been utilized through the current numerical study. The racetrack slot (rectangular slot with fully round ends) was proven to outperform the typical round hole in terms of the cooling effect. The racetrack aspect ratio of seven has been designated by previous study to give the best cooling performance. Therefore, it served as a starting point for further optimization of the coolant pipe shape utilizing ANSYS Fluent Adjoint solver. The advantage of the numerical optimization tool is that it allows for irregular shape optimization. The concern that used to face irregular geometry designs is the lack of manufacturability. Nevertheless, the recent advancement in manufacturing processes, especially with the wide range and spread of additive manufacturing technique, paved the way for more powerful shape design through less constrained optimization process. Starting from the optimum racetrack geometry, the optimum irregular pipe shape was designated in two optimization steps, through which the average adiabatic film effectiveness over the test surface has increased from 0.24 to 0.34, recording a remarkable improvement.
An Initial Study Towards In-Situ Ultrasonic Monitoring and Measurement of Part Properties During Photopolymer Based Additive Manufacturing
Authors: Su Tong , Jiang Menghan , Wang Qing-Ming , Zhao Xiayun
Published: January 2020

This paper presents our recent preliminary study on using a novel in-house ultrasonic measurement technique to investigate ex situ the elastic modulus evolution during a photopolymer based additive manufacturing (PAM). Experiment is designed to study the effects of PAM process parameters on the elastic modulus of fabricated samples. A unique lab-built line-focused ultrasonic transducer based on time-resolved defocusing is employed to measure velocities of the surface waves (Rayleigh waves and longitudinal bulk waves) leaking from the samples. The samples’ elastic properties can be calculated from the obtained wave velocities. As a result, changes in elastic modulus with the varying PAM process conditions are successfully detected and quantified by this ex situ ultrasonic technique, revealing important information on both the “need-to” and “how-to” develop an in-situ monitoring and measurement system for part properties during PAM processes. The research outcome will not only enhance understanding about evolution of mechanical properties during PAM, but also offer insightful guidance on a future development based on the reported ex-situ ultrasonic technology towards an in-situ ultrasonic system for in-process measurement and advanced control of PAM.
On the Role of Segmentation in the Analysis of Micro-CT Data of Impact Damage in the CFRP Composites
Authors: Zhupanska Olesya I.
Published: January 2020

In this paper we discuss the role of different image segmentation methods that are used for the analysis of the micro computed tomography (micro-CT) data of damage in the carbon fiber reinforced polymer (CFRP) composites due to low velocity impact. Segmentation is one of the most critical steps in the image processing of the three dimensional (3D) CT data and accurate assessment of the damage from CT data depends to a great extent on the image segmentation. We have extensively studied low velocity impact damage in the CFRP composites using 3D CT. CFRP textile composite laminates were impacted using an Instron 8200 Dynatup drop-weight impact machine. ZEISS METROTOM 1500 CT scanner was used to evaluate internal impact damage. VGStudio MAX was used for reconstruction of CT images. Different segmentation procedures were used during image processing of the CT images. Differences in the estimates of the damage zone obtained using different segmentation techniques have been assessed.
Investigations of Three-Dimensional Flow Field Development in an Axial Compressor Cascade
Authors: El-Shahat Saeed A. , El-Batsh Hesham M. , Attia Ali M. A. , Li Guojun , Fu Lei
Published: January 2020

This paper presents a complete study about three-dimensional (3-D) flow field development in a linear compressor cascade where flow field in the blade passage has been studied experimentally as well as numerically.

In the experimental work, a linear compressor cascade test section was installed in an open loop wind tunnel. The experimental data was acquired for a Reynolds number of 2.98 × 105 based on the blade chord and the inlet flow conditions. The flow field characteristics in blade passage including 3-D flow velocity and velocity magnitude have been measured by using calibrated five and seven-hole pressure probes connected to ATX sensor module data acquisition system (DAQ). To investigate flow development in the blade passage, velocity coefficient through streamwise planes has been calculated from the measured data. The computational fluid dynamics (CFD) study of the flow field was performed to gain a better understanding of the flow features. Present computational study was first validated with previous experimental and numerical work to check mesh accuracy and give confidence for computational results. Then, two turbulence models, Spalart-Allmaras (S-A) and shear stress transport SST (k-ω) were used for the present work. From both parts of study, the flow field development through the cascade have been investigated and compared. Moreover, the received data demonstrated a good agreement between the experimental and computational results. The predicted flow streamlines by numerical calculations showed regions characterized by flow separation and recirculation zones such as corner separation that could be used to enhance the understanding of the loss mechanism in compressor cascades. All measurements taken by the two probes, 5 and 7-hole pressure probes, have been analyzed and compared. The 5-hole pressure probe measurements have showed more agreements with computational results than 7-hole probe. Furthermore S-A turbulence model calculations showed more consistencies with experimental results than SST (k-ω) model.
A Clinical Test to Capture Humidity From Exhalation: Self-Humidification
Authors: Grau-Bartual Sandra , Al-Jumaily Ahmed M.
Published: January 2020

Lung supportive devices are widely used for non-invasive positive airway pressure ventilation and respiratory therapy to help provide breathing support for patients with various lung diseases including Obstructive Sleep Apnea. These devices deliver air to the patient through a facial or nasal mask, and the use of these devices normally results in dryness in the upper airways. However, the exhaled air consists of very high humidity content hence the moisture content of this air can be reused in the inhalation process. This research focuses on testing clinically a previously developed element which can recover the moisture from the exhaled air and use it for re-inhalation. 21 healthy volunteers between the ages of 21 and 55, where 38.1% were females and 61.9% males, were invited to participate in this study. The results show a viable element which is able to trap water molecules from the expiration airflow and release them into the inspiration airflow.
Topology Optimization of Plastic Parts for Injection Molding
Authors: Oliver Kathryn , Anwar Sohel , Tovar Andres
Published: January 2020

Topology optimization is broadly recognized as a design approach to generate high-performance conceptual designs suitable for freeform fabrication, e.g., additive manufacturing. When other fabrication methods are considered, topology optimization must integrate manufacturing constraints. The integration of constraints for extrusion and casting has been addressed in the past by a few researcher groups. In this work, extrusion and casting constraints are revisited and extended to include plastic injection. The proposed method relies on the use of intersection planes and the definition of a parting line within the planes. The resulting topologies can be injected in a two-plate mold without the use of inserts. The implementation and results of the proposed approach are demonstrated in classic three-dimensional problems that include a cantilevered beam with different load conditions.
Large Deformation Behavior of Porous Polymer Materials With 3D Random Pore Structure: Experimental Investigation and FEM Modeling
Authors: Emori Kanako , Miura Tatsuma , Yonezu Akio
Published: January 2020

This study investigates the deformation behavior of porous polymer materials with 3D random pore structure. The test sample has sub-micron-sized pores with an open cellular structure, which plays a critical role for water purification. The base polymer is PVDF (polyvinylidene difluoride). First, the surface and cross section of the sample are observed using FESEM to investigate the microstructure (cell size and geometry of the cell ligament, etc). Next, uni-axial tensile loading is carried out for polymeric membrane and it is found that the membranes underwent elasto-plastic deformation. In order to establish a numerical model, finite element metod (FEM) is employed. Using a software of Surface Evolver, 3D random pore structure is created in the representative volume element (RVE). The established computational model can predict both elastic deformation and plastic deformation. Furthermore, viscoplastic deformation behavior (i.e. time-dependent deformation and creep deformation) is investigated, experimentally and numerically. In particular, creep compliance is measured, and we investigate the effect of applied loading on creep deformation behavior. Using the time–temperature–stress superposition principle (TTSSP), we obtain a new master curve, which covers higher stress level, and successfully establish an FEM model of creep deformation of the test sample. The present model enables the prediction of the macroscopic and microscopic deformation behavior of the porous materials, by taking into account of 3D random pore structure.
Electrostatically Actuated MEMS Circular Plate Resonators: Frequency Response of Superharmonic Resonance of Third Order
Authors: Beatriz Julio , Caruntu Dumitru I.
Published: January 2020

This paper deals with the frequency response of superharmonic resonance of order three of electrostatically actuated MicroElectroMechanical Systems (MEMS) circular plate resonators. The MEMS structure in this work consists of an elastic circular microplate parallel to an electrode ground plate. The microplate is elelctrostatically actuated through an AC voltage between the microplate and the ground plate. The voltage is in the category of hard excitations. The AC frequency is near one sixth of the natural frequency of the resonator. Since the electrostatic force acting on the resonator is proportional to the square of the voltage, it leads to superharmonic resonance of third order. Besides the electrostatic force, the system experiences damping. The damping force in this work is proportional to the velocity of the resonator, i.e. it is linear damping. Three methods are employed in this investigation. First, the Method of Multiple Scales (MMS), a perturbation method, is used predictions of the resonant regions for weak nonlinearities and small to moderate amplitudes. Second, the Reduced Order Model (ROM) method using two modes of vibration are also utilized to investigate the resonance. ROM is solved numerically integrated using Matlab in order to simulate time responses of the structure, and third, the ROM is used to predict the frequency response using AUTO, a software for continuation and bifurcation analysis. All methods are in agreement for moderate nonlinearities and small to moderate amplitudes. For relatively large amplitudes, when compared to the gap between the microplate and the ground plate, ROM more accurately predicts the behavior of the system. Effects of the parameters of the system on the frequency response are reported.