bluuebunny/crossref_metadata_2025 huggingface dataset:
Sustained Integration for Computer-Aided Manufacturing: Integrating With Successive Versions of Step or IGES Files
Authors: Kirkwood Robert , Sherwood James A.
Published: July 2018

Computer-aided design (CAD)/computer-aided manufacturing (CAM)/computer-aided engineering (CAE) integration offers designers, analysts, and manufacturers the opportunity to share data efficiently throughout the product development process. CAM for NC programing and tool design integrated with solid model data from CAD systems represents a large portion of the CAD/CAM/CAE domain. Sustained integration whereby successive changes to a CAD model are reintegrated with downstream applications is considered the most advanced and useful integration. Sustained integration is typically maintained when working in a homogeneous CAD/CAM environment. However, when working with applications that do not share a common environment (i.e., heterogeneous integration), sustained integration fails, and this lack of sustained integration can result in a loss of detailed information as a design progresses through the engineering design process. In the current paper, the authors discuss and demonstrate a novel approach to achieve sustained integration when working in heterogeneous CAD/CAM environments. After providing basic background information to establish a context, then discussing state-of-the-art and emerging solutions, the paper discusses virtual persistent identifiers as described via design change vectors (VPI/DCV). A series of three case studies shows sustained integration based on neutral formats like STEP working as well as that observed in homogeneous environments. This novel approach demonstrates success as a generic solution using common export formats from the current CAD systems and avoids the need to establish any new standards to achieve sustained integration. The paper finishes with a summary of observations learned from these case studies along with possible future research topics.
Effect of Longitudinal Vortex Generator Location on Thermoelectric-Hydraulic Performance of a Single-Stage Integrated Thermoelectric Power Generator
Authors: Deshpande Samruddhi , Ravi Bharath Viswanath , Pandit Jaideep , Ma Ting , Huxtable Scott , Ekkad Srinath
Published: July 2018

Vortex generators have been widely used to enhance heat transfer in various heat exchangers. Out of the two types of vortex generators, transverse vortex generators and longitudinal vortex generators (LVGs), LVGs have been found to show better heat transfer performance. Past studies have shown that the implementation of these LVGs can be used to improve heat transfer in thermoelectric generator systems. Here, a built in module in COMSOL Multiphysics® was used to study the influence of the location of LVGs in the channel on the comprehensive performance of an integrated thermoelectric device (TED). The physical model under consideration consists of a copper interconnector sandwiched between p-type and n-type semiconductors and a flow channel for hot fluid in the center of the interconnector. Four pairs of LVGs are mounted symmetrically on the top and bottom surfaces of the flow channel. Thus, using numerical methods, the thermo-electric-hydraulic performance of the integrated TED with a single module is examined. By fixing the material size D, the fluid inlet temperature Tin, and attack angle β, the effects of the location of LVGs and Reynolds number were investigated on the heat transfer performance, power output, pressure drop, and thermal conversion efficiency. The location of LVGs did not have significant effect on the performance of TEGs in the given model. However, the performance parameters show a considerable change with Reynold's number and best performance is obtained at Reynold number of Re = 500.
On the Generation of Isolated Green Water Events Using Wet Dam-Break
Authors: Hernández-Fontes Jassiel V. , Vitola Marcelo A. , Silva Monica C. , Esperança Paulo de Tarso T. , Sphaier Sergio H.
Published: July 2018

Green water occurs when an incoming wave exceeds the freeboard and propagates onto the deck of naval/offshore structures, such as floating production storage and offloading units and platforms. This water can affect the integrity of facilities and equipment that are installed on the deck, compromise the safety of the crew, and affect the dynamic stability of the structure. Traditionally, wave trains have been used to study the green water problem, which is a good approach to analyzing consecutive green water events. However, to carry out systematic studies that allow local details to be identified for different types of green water, an alternative method is to study isolated events generated by a single incoming wave. The purpose of this paper was to experimentally investigate the generation of different types of isolated green water events using the wet dam-break (DB) approach as an alternative to generating the incoming wave. Tests were carried out in a rectangular tank with a fixed internal structure. Different freeboard conditions were tested for two aspect ratios of the wet DB (h0/h1=0.40 and 0.6). Conventional wave probes were used to measure the water levels in the tank, and a high-speed camera was set to capture details of the generated green water events. The results demonstrated the ability of this approach to represent different types of green water, similar to those obtained with unbroken regular waves in barge-shaped fixed structures, including DB, plunging-dam-break (PDB) and hammer-fist (HF).
Tactical Operating Room Planning Based on System Transient Performance Control
Authors: Zeng Zhigang , Brennan Robert W. , Freiheit Theodor
Published: July 2018

Efficient management of operating room (OR) schedules is important as the OR is the largest cost and revenue center in a hospital and can substantially impact its staffing and finances. A major problem associated with developing OR schedules for elective surgeries is the schedule disruption from uncertainty inherent in the duration of surgical services. Another problem is the cascaded impact on overall system performance of facilities and resources upstream and downstream to the OR. Using a manufacturing system analytical approach, the peri-operative process is modeled as a transfer line with three machines and two buffers by a discrete time Markov chain. Uncertain surgical and recovery duration is quantified probabilistically and incorporated in the Markov chain model with multistate geometrical machines. Model predictive control (MPC) to pace patient release into the ORs is then applied to control system transient performance. With this model and empirical studies of surgery and recovery duration, guidance can be given to OR managers on how to dynamically schedule and reschedule patients throughout an OR's day that minimizes cost for a given workload. The proposed predictive control model can also control other transient performance metrics such as OR and recovery room (RR) utilization, patient flow, and cost.
Thermo-Economic Operation Analysis of SOFC–GT Combined Hybrid System for Application in Power Generation Systems
Authors: Pirkandi Jamasb , Ommian Mohammad
Published: July 2018

This study investigated the combination of the direct and indirect hybrid systems in order to develop a combined hybrid system. In the proposed system, a direct solid oxide fuel cell (SOFC) and gas turbine (GT) hybrid system and an indirect fuel cell cycle were combined and exchanged the heat through a heat exchanger. Several electrochemical, thermal, and thermodynamic calculations were performed in order to achieve more accurate results; then, beside the parametric investigation of the abovementioned hybrid system, the obtained results were compared to the results of direct and indirect hybrid systems and simple GT cycle. Results indicate that the efficiency of the combined hybrid system was between those of the direct and indirect hybrid systems. The electrical efficiency and the overall efficiency of the combined hybrid system were 43% and 59%, respectively. The generation power in the combined hybrid system was higher than that of both other systems, which was the only advantage of using the combined hybrid system. The generation power in the combined hybrid system was higher than that of the direct hybrid system by 16%; accordingly, it is recommended to be used by the systems that are supposed to have high generation power.
Application of Adaptive Neuro-Fuzzy Inference System Techniques to Predict Water Activity in Proton Exchange Membrane Fuel Cell
Authors: Mammar Khaled , Laribi Slimane
Published: July 2018

This work defines and implements a technique to predict water activity in proton exchange membrane fuel cell. This technique is based on the electrochemical impedance spectroscopy (EIS) as sensor and adaptive neuro-fuzzy inference system (ANFIS) as estimator. For this purpose, a proton exchange membrane fuel cell (PEMFC) model has been proposed to study the performances of the fuel cell for different operating conditions where the simulation model for water activity behavior is in the proposed structure. The technique based on ANFIS predicts the PEM fuel cell relative humidity (RH) from the EIS. For creation of ANFIS training and checking database, a new method based on factorial design of experimental is used. To check the proposed technique, the ANFIS estimator will be compared with the output humidity relative observation.
Drag Characterization Study of Variable Camber Continuous Trailing Edge Flap
Authors: Kaul Upender K. , Nguyen Nhan T.
Published: July 2018

A Reynolds-averaged Navier–Stokes (RANS) computational study was conducted to investigate the effect of various variable camber continuous trailing edge flap (VCCTEF) configurations on the lift and drag of a NASA generic transport model (GTM) wing section. Out of the five two-dimensional (2D) VCCTEF configurations considered with varying camber in the three-segment flap region, with a total deflection of 6 deg, the best stall performance was exhibited by the circular and parabolic arc camber flaps. Both circular and parabolic arc flaps give similar lift performance, with the circular arc yielding a higher lift coefficient and parabolic arc resulting in the lowest drag and hence the best L/D performance at design Cl. Analysis of results based on linear theory shows excellent agreement between computed and theoretical incremental lift.
Comparison of Diesel Engine Efficiency and Combustion Characteristics Between Different Bore Engines
Authors: Li Jue , Jacobs Timothy J. , Bera Tushar , Parkes Michael A.
Published: July 2018

This study investigates the effects of engine bore size on diesel engine performance and combustion characteristics, including in-cylinder pressure, ignition delay, burn duration, and fuel conversion efficiency, using experiments between two diesel engines of different bore sizes. This study is part of a larger effort to discover how fuel property effects on combustion, engine efficiency, and emissions may change for differently sized engines. For this specific study, which is centered only on diagnosing the role of engine bore size on engine efficiency for a typical fuel, the engine and combustion characteristics are investigated at various injection timings between two differently sized engines. The two engines are nearly identical, except bore size, stroke length, and consequently displacement. Although most of this diagnosis is done with experimental results, a one-dimensional model is also used to calculate turbulence intensities with respect to geometric factors; these results help to explain observed differences in heat transfer characteristics of the two engines. The results are compared at the same brake mean effective pressure (BMEP) and show that engine bore size has a significant impact on the indicated efficiency. It is found that the larger bore engine has a higher indicated efficiency than the smaller displaced engine. Although the larger engine has higher turbulence intensities, longer burn durations, and higher exhaust temperature, the lower surface area to volume ratio and lower reaction temperature leads to lower heat losses to the cylinder walls. The difference in the heat loss to the cylinder walls between the two engines is found to increase with increasing engine load. In addition, due to the smaller volume-normalized friction loss, the larger sized engine also has higher mechanical efficiency. In the net, since the brake efficiency is a function of indicated efficiency and mechanical efficiency, the larger sized engine has higher brake efficiency with the difference in brake efficiency between the two engines increasing with increasing engine load. In the interest of efficiency, larger bore designs for a given displacement (i.e., shorter strokes or few number of cylinders) could be a means for future efficiency gains.
A Comprehensive Investigation of Blade Row Interaction Effects on Stator Loss Utilizing Vane Clocking
Authors: Smith Natalie R. , Key Nicole L.
Published: July 2018

Blade row interactions drive the unsteady performance of high-pressure compressors. Vane clocking is the relative circumferential positioning of consecutive stationary vane rows with the same vane count. By altering the upstream vane wake's path with respect to the downstream vane, vane clocking changes the blade row interactions and results in a change in steady total pressure loss on the downstream vane. The open literature lacks a conclusive discussion of the flow physics governing these interactions in compressors. This paper presents the details of a comprehensive vane clocking study on the embedded stage of the Purdue three-stage axial compressor. The steady loss results, including radial total pressure profiles and surface flow visualization, suggest a shift in the stator 2 corner separations occurs between clocking configurations associated with the maximum and minimum total pressure loss. To better understand the flow mechanisms driving the vane clocking effects on the steady stator 2 performance, time-resolved interrogations of the stator 2 inlet flow field, surface pressure unsteadiness, and boundary layer response were conducted. The stator 2 surface flows, both pressure unsteadiness and boundary layer transition, are influenced by vane clocking and interactions between rotor 1 and rotor 2, but neither of these results indicate a cause for the change in steady total pressure loss. Moreover, they are a result of upstream changes in the flow field: the interaction between the stator 1 wake and rotor 2 results in a circumferentially varying pattern which alters the inlet flow field for the downstream row, including the unsteadiness and frequency content in the tip and hub regions. Therefore, under different clocking configurations, stator 2 experiences significantly different inlet blockage and unsteadiness from the rotor 2 tip leakage flow and hub corner separation, which, in turn, shifts the radial blade loading distribution and subsequent loss development of stator 2.
Constrained Buckling of Spatial Elastica: Application of Optimal Control Method
Authors: Liakou Anna
Published: July 2018

A post-buckling analysis of a constant or variable length spatial elastica constrained by a cylindrical wall is performed for a first time by adopting an optimal control methodology. Its application in a constrained buckling analysis is shown to be superior when compared to other numerical techniques, as the inclusion of the unilateral constraints is feasible without the need of any special treatment or approximation. Furthermore, the formulation is simple and the optimal configurations of the spatial elastica can be also obtained by considering the minimization condition of the Hamiltonian. We first present the optimal control formulation for the constrained buckling problem of a constant length spatial elastica, including its associated necessary optimality conditions that constitute the Pontryagin's minimum principle. This fundamental constrained buckling problem is used to validate the proposed methodology. The general buckling problem of a variable length spatial elastica is then analyzed that consists of two parts; (1) the solution of the optimal control problem that involves the inserted elastica inside the conduit and (2) the derivation of the buckling load by taking into account the generation of the configurational or Eshelby-like force at the insertion point of the sliding sleeve. A variety of examples are accordingly presented, where the effects of factors, such as the presence of uniform pressure, the clearance of the wall, and the torsional rigidity, on the buckling response of the spatial elastica, are investigated.
Fractional-Order Nonlinear Disturbance Observer Based Control of Fractional-Order Systems
Authors: Muñoz-Vázquez Aldo Jonathan , Parra-Vega Vicente , Sánchez-Orta Anand
Published: July 2018

The robust control for a class of disturbed fractional-order systems is presented in this paper. The proposed controller considers a dynamic observer to exactly compensate for matched disturbances in finite time, and a procedure to compensate for unmatched disturbances is then derived. The proposed disturbance observer is built upon continuous fractional sliding modes, producing a fractional-order reaching phase, leading to a continuous control signal, yet able to reject for some continuous but not necessarily differentiable disturbances. Numerical simulations and comparisons are presented to highlight the reliability of the proposed scheme.
Lyapunov Control Strategy for Thermoelectric Cooler Activating an Ice-Clamping System
Authors: Mironova Alexandra , Mercorelli Paolo , Zedler Andreas
Published: July 2018

Deformation-free clamping plays an important role in manufacturing systems helping to ensure zero-defect production. The fixture of workpieces during machining processes poses challenges not only for microparts but also for thin-walled pieces or free-form surfaces in macromanufacturing. To address this challenge, a nontraditional adhesive technique, using frozen water to clamp, is introduced in this paper. By increasing the cooling power and thus reducing the temperature of the clamping plate, higher adhesive ice strength and, therefore, a safer clamping system during machining process, can be achieved. The objective of this investigation is to ensure a stable low temperature and to compensate for thermal disturbances. Thanks to their structural robustness, Lyapunov-based control strategies demonstrate an appropriate capability to achieve these results in real industrial applications. Model design of the clamping system as well as simulation and experimental results are shown and discussed.
Observational Seismic Fragility Curves for Steel Cylindrical Tanks
Authors: D'Amico Marta , Buratti Nicola
Published: July 2018

The evaluation of seismic vulnerability of atmospheric above ground steel storage tanks is a fundamental topic in the context of industrial safety. Depending on the shell portion affected, on the extent of damage, and on toxicity, flammability, and reactivity of stored substances, liquid leakages can trigger hazardous chains of events whose consequences affect not only the plant but also the surrounding environment. In light of that, the study proposed herein provides an analysis of the seismic fragility of cylindrical above ground storage tanks based on observational damage data. The first phase of this work has consisted in collecting a large empirical dataset of information on failures of atmospheric tanks during past earthquakes. Two sets of damage states have then been used in order to characterize the severity of damage and the intensity of liquid releases. Empirical fragility curves have been fitted by using Bayesian regression. The advantage of this approach is that it is well suited to treat direct and indirect information obtained from field observations and to incorporate subjective engineering judgement. Different models have been employed in order to investigate the effects of tank aspect ratio, filling level, and base anchorage. Moreover, the effects of interaction between these critical aspects are included in fragility analysis. The hazard parameter used is the peak ground acceleration (PGA). Seismic fragility curves obtained from the described procedure are compared to those available in the technical literature.
Study of Erosion–Corrosion and Corrosion Behavior of Commercially Pure-Ti During Slurry Erosion
Authors: Khayatan N. , Ghasemi H. M. , Abedini M.
Published: July 2018

The erosion–corrosion (EC) and pure erosion of commercially pure titanium have been investigated in a 3.5% sodium chloride solution containing 10, 30, and 60 g/l SiO2 particles with an average size of 318 μm. The tests were performed at impact velocities of 4, 6, and 9 m/s under two impact angles of 40 deg and 90 deg. Polarization technique was used to study corrosion behavior of the material during erosion–corrosion. The eroded surfaces were examined by a scanning electron microscope (SEM) and a surface profilometer. The pure erosion, corrosion, and erosion–corrosion rates increased as impact velocity and sand concentration increased. The corrosion rates of the eroding surfaces under a normal impact were lower than those at an impact angle of 40 deg. The S/T ratio, i.e., the ratio of synergy to erosion–corrosion rates was about 80% at an impact velocity of 4 m/s, which indicated the high effect of the electrochemical corrosion on the degradation of CP-Ti at low velocity. The S/T ratio decreased to 30% and 15% at the impact velocities of 6 and 9 m/s, respectively. The S/T ratio was also decreased with increasing sand concentration indicating a greater role of mechanical degradation upon the erosion–corrosion rate in the concentrated slurries.
Kinematic Design of a New Four Degree-of-Freedom Parallel Robot for Knee Rehabilitation
Authors: Aginaga Jokin , Iriarte Xabier , Plaza Aitor , Mata Vicente
Published: July 2018

Rehabilitation robots are increasingly being developed in order to be used by injured people to perform exercise and training. As these exercises do not need wide range movements, some parallel robots with lower mobility architecture can be an ideal solution for this purpose. This paper presents the design of a new four degree-of-freedom (DOF) parallel robot for knee rehabilitation. The required four DOFs are two translations in a vertical plane and two rotations, one of them around an axis perpendicular to the vertical plane and the other one with respect to a vector normal to the instantaneous orientation of the mobile platform. These four DOFs are reached by means of two RPRR limbs and two UPS limbs linked to an articulated mobile platform with an internal DOF. Kinematics of the new mechanism are solved and the direct Jacobian is calculated. A singularity analysis is carried out and the gained DOFs of the direct singularities are calculated. Some of the singularities can be avoided by selecting suitable values of the geometric parameters of the robot. Moreover, among the found singularities, one of them can be used in order to fold up the mechanism for its transportation. It is concluded that the proposed mechanism reaches the desired output movements in order to carry out rehabilitation maneuvers in a singularity-free portion of its workspace.
Efficient Reliability Assessment With the Conditional Probability Method
Authors: Mansour Rami , Olsson Mårten
Published: July 2018

Reliability assessment is an important procedure in engineering design in which the probability of failure or equivalently the probability of survival is computed based on appropriate design criteria and model behavior. In this paper, a new approximate and efficient reliability assessment method is proposed: the conditional probability method (CPM). Focus is set on computational efficiency and the proposed method is applied to classical load-strength structural reliability problems. The core of the approach is in the computation of the probability of failure starting from the conditional probability of failure given the load. The number of function evaluations to compute the probability of failure is a priori known to be 3n + 2 in CPM, where n is the number of stochastic design variables excluding the strength. The necessary number of function evaluations for the reliability assessment, which may correspond to expensive computations, is therefore substantially lower in CPM than in the existing structural reliability methods such as the widely used first-order reliability method (FORM).
Design of Three New Cam-Based Constant-Force Mechanisms
Authors: López-Martínez Javier , García-Vallejo Daniel , Arrabal-Campos Francisco Manuel , Garcia-Manrique Jose Manuel
Published: July 2018

Constant-force mechanisms are designed to keep a constant or nearly constant input force along a prescribed stroke of the mechanism. The implementation of this kind of mechanisms has been approached in literature using compliant mechanisms or through a certain combination of springs and nonlinear transmissions. In this work, three new constant-force mechanisms based on the use of springs, rollers, and cams are presented and analyzed. The rolling friction forces between the rollers and the cam are included in the force equilibrium equations and considered in the integration of the cam profile. The influence of the friction force on the input force as well as the design parameters involved is studied based on numerical techniques and simulations. In fact, the results evidence that to obtain a precise constant-force mechanism, rolling friction forces must be considered in the cam profile definition. The main design guidelines for the three constant-force mechanisms proposed are described.
Experimental and Theoretical Rotordynamic Coefficients of Smooth and Round-Hole Pattern Water-Fed Annular Seals
Authors: Jolly Pascal , Arghir Mihaï , Bonneau Olivier , Hassini Mohamed-Amine
Published: July 2018

This work presents the comparison between experimental and theoretical results obtained for three straight annular seals. One of the annular seals has smooth rotor and stator while the others have a textured stator; the textures are equally spaced shallow round holes, with two different depths. The experimental results were obtained on a test rig dedicated to the identification of the dynamic coefficients of high Reynolds bearings and annular seals. The test rig uses hot water (<50 °C) as a working fluid. Dynamic excitations imposed by piezoelectric shakers to the rotor enable the identification of dynamic coefficients via complex impedances. Theoretical results compared with experimental findings were obtained by numerically solving the “bulk flow” equations (film thickness averaged equations dominated by inertia effects). The numerical model was extensively validated for smooth annular seals but is less confident for textured surfaces. The present comparisons between experimental and numerical results enable to estimate the accuracy of the numerical model employed for the textured seals.
Design Methodology for Supersonic Radial Vanes Operating in Nonideal Flow Conditions
Authors: Anand Nitish , Vitale Salvatore , Pini Matteo , Otero Gustavo J. , Pecnik Rene
Published: July 2018

The stator vanes of high-temperature organic Rankine cycle (ORC) radial-inflow turbines (RIT) operate under severe expansion ratios and the associated fluid-dynamic losses account for nearly two-thirds of the total losses generated within the blading passages. The efficiency of the machine can strongly benefit from specialized high-fidelity design methods able to provide shapes attenuating shock wave formation, consequently reducing entropy generation across the shock-wave and mitigating shock-wave boundary layer interaction. Shape optimization is certainly a viable option to deal with supersonic ORC stator design, but it is computationally expensive. In this work, a robust method to approach the problem at reduced computational cost is documented. The method consists of a procedure encompassing the method of characteristics (MoC), extended to nonideal fluid flow, for profiling the diverging part of the nozzle. The subsonic section and semibladed suction side are retrieved using a simple conformal geometrical transformation. The method is applied to design a supersonic ORC stator working with Toluene vapor, for which two blade shapes were already available. The comparison of fluid-dynamic performance clearly indicates that the MoC-Based method is able to provide the best results with the lowest computational effort, and is therefore suitable to be used in a systematic manner for drawing general design guidelines.
Graphite Supported Silica Immobilized Phosphotungstic Acid Based Ion-Conducting Inorganic Membrane
Authors: Pandey Jay , Seepana Murali M.
Published: July 2018

An asymmetric, inorganic ion-conducting membrane was synthesized by depositing a top layer containing silica-immobilized phosphotungstic acid (Si-PWA) over a graphite sheet. Surface morphology, thermal stability, and structure of the top layer of the membrane were studied using scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR), respectively. The transport number and specific conductivity of the membrane were measured using membrane potential and impedance measurements, respectively. The composition of the top layer was varied by changing the molar ratio of PWA and tetraethoxy orthosilicate (TEOS) in the casting sol. The transport number and specific conductivity of the membrane increased on increasing PWA fraction in the casting solution. The highest transport number for sodium ion was 0.98 for PWA: TEOS molar ratio of 1.5. Specific conductivity of the membrane, with 0.5 PWA: TEOS, was 0.0082 S cm−1 which was lower compared to the membrane with 1.5 PWA: TEOS of specific conductivity 0.017 S cm−1. The specific conductivity of the membrane increased with increase in the temperature for both 0.5 and 1.5 molar ratio of PWA: TEOS with the calculated activation energy 18.9 and 8.8 kJ/mol, respectively.
Analysis and Control of Torque Split in Hybrid Electric Vehicles by Incorporating Powertrain Dynamics
Authors: Bidarvatan Mehran , Shahbakhti Mahdi
Published: July 2018

Hybrid electric vehicle (HEV) energy management strategies usually ignore the effects from dynamics of internal combustion engines (ICEs). They usually rely on steady-state maps to determine the required ICE torque and energy conversion efficiency. It is important to investigate how ignoring these dynamics influences energy consumption in HEVs. This shortcoming is addressed in this paper by studying effects of engine and clutch dynamics on a parallel HEV control strategy for torque split. To this end, a detailed HEV model including clutch and ICE dynamic models is utilized in this study. Transient and steady-state experiments are used to verify the fidelity of the dynamic ICE model. The HEV model is used as a testbed to implement the torque split control strategy. Based on the simulation results, the ICE and clutch dynamics in the HEV can degrade the control strategy performance during the vehicle transient periods of operation by around 8% in urban dynamometer driving schedule (UDDS) drive cycle. Conventional torque split control strategies in HEVs often overlook this fuel penalty. A new model predictive torque split control strategy is designed that incorporates effects of the studied powertrain dynamics. Results show that the new energy management control strategy can improve the HEV total energy consumption by more than 4% for UDDS drive cycle.
Control of Droplet Detachment Frequency in a GMAW Process by a Hybrid Model Predictive Control
Authors: Sartipizadeh Hossein , Haeri Mohammad
Published: July 2018

Efficient control of a gas metal arc welding (GMAW) process enables one to obtain high quality products as a consequence of achieving a high quality weld. Although control of the droplet detachment frequency in the welding process would play a great role in improving the welding quality, measuring this variable is difficult and expensive. In this paper, we attempt to control the frequency of droplet detachments without directly measuring it. To this end, we utilize the hybrid property of the GMAW process to indirectly control the frequency. Specifically, a mixed logical dynamical (MLD) model is obtained by considering the hybrid act of the process during droplet detachment. Then, a nonlinear model predictive controller with variable control and prediction horizons is designed incorporating the hybrid behavior of the process. The controller regulates the droplet detachment frequency without measuring this variable directly. Computer simulation results show that the proposed controller leads to a higher quality weld compared to the present approaches.
Influence of Turbulent Combustion Noise on the Decrement Estimates of Gas Oscillations
Authors: Karmalita V.
Published: July 2018

This paper deals with the autoregression method to determine the logarithmic decrement and natural frequency of gas oscillations in a combustion chamber. The proposed approach to quantify the impact of combustion noise on the estimates of oscillation decrement is based on a linear model of the vibrating combustion phenomena. An application of the proposed approach for afterburner tests is presented as well.
Analysis of Parametric Resonances in In-Plane Vibrations of Electrostrictive Hyperelastic Plates
Authors: Tripathi Astitva , Bajaj Anil K.
Published: July 2018

Electrostriction is a recent actuation mechanism which is being explored for a variety of new micro- and millimeter scale devices along with macroscale applications such as artificial muscles. The general characteristics of these materials and the nature of actuation lend itself to possible production of very rich nonlinear dynamic behavior. In this work, principal parametric resonance of the second mode in in-plane vibrations of appropriately designed electrostrictive plates is investigated. The plates are made of an electrostrictive polymer whose mechanical response can be approximated by Mooney Rivlin model, and the induced strain is assumed to have quadratic dependence on the applied electric field. A finite element model (FEM) formulation is used to develop mode shapes of the linearized structure whose lowest two natural frequencies are designed to be close to be in 1:2 ratio. Using these two structural modes and the complete Lagrangian, a nonlinear two-mode model of the electrostrictive plate structure is developed. Application of a harmonic electric field results in in-plane parametric oscillations. The nonlinear response of the structure is studied using averaging on the two-mode model. The structure exhibits 1:2 internal resonance and large amplitude vibrations through the route of parametric excitation. The principal parametric resonance of the second mode is investigated in detail, and the time response of the averaged system is also computed at few frequencies to demonstrate stability of branches. Some results for the case of principal parametric resonance of the first mode are also presented.
Integrating Operator Information for Manual Grinding and Characterization of Process Performance Based on Operator Profile
Authors: Das Jayanti , Bales Gregory L. , Kong Zhaodan , Linke Barbara
Published: July 2018

Due to its high versatility and scalability, manual grinding is an important and widely used technology in production for rework, repair, deburring, and finishing of large or unique parts. To make the process more interactive and reliable, manual grinding needs to incorporate “skill-based design,” which models a person-based system and can go significantly beyond the considerations of traditional human factors and ergonomics to encompass both processing parameters (e.g., feed rate, tool path, applied forces, material removal rate (MRR)), and machined surface quality (e.g., surface roughness). This study quantitatively analyzes the characteristics of complex techniques involved in manual operations. A series of experiments have been conducted using subjects of different levels of skill, while analyzing their visual gaze, cutting force, tool path, and workpiece quality. Analysis of variance (ANOVA) and multivariate regression analysis were performed and showed that the unique behavior of the operator affects the process performance measures of specific energy consumption and MRR. In the future, these findings can be used to predict product quality and instruct new practitioners.
Twin-Fluid Atomized Spray Combustion of Straight Vegetable Oil at Elevated Pressures
Authors: Niguse Yonas , Agrawal Ajay K.
Published: July 2018

The effect of the chamber pressure on combustion of a twin-fluid-atomized spray of straight vegetable oil (VO) in a swirl stabilized combustion system is experimentally studied. A system with high pressure capabilities was developed, and flame and emissions characteristics of VO are investigated at elevated pressures up to about 5 bars, different heat release rates (HRRs), and atomizing air to liquid ratios (ALR) by mass. An image analysis technique was developed to infer flame and soot characteristics from visual images acquired by a digital camera. An increase in the ALR resulted in improved combustion of VO, characterized by blue flames, lower CO and NOx emissions, and minimal soot formation. For a given fuel flow rate, an increase in the chamber pressure resulted in smaller volume flames with lower CO levels but higher NOx emissions. Compared to diesel, as pressure increased, straight VO flames produced lower NOx and more voluminous flames characterized by distributed combustion with less soot formation. Overall, straight VO could be atomized and combusted at elevated pressures using the twin-fluid atomizer of the present study, and the resulting VO flames exhibited less sensitivity to chamber pressure variations.
Influence of Nonflow Zone (Back Cavity) Geometry on the Performance of Pumps as Turbines
Authors: Doshi Ashish , Channiwala Salim , Singh Punit
Published: July 2018

The larger objective of this research comes from the fact that optimization studies in “pumps operated as turbines” have concentrated only within flow zones without any physical perception regarding the influence of nonflow zones such as back-cavities in standard end-suction pumps. Four pumps of different designs are selected and their back cavities are reduced by inserting solid material, leaving a very small axial clearance. The effects are investigated on an experimental platform, which reveal unique phenomena taking place. The first is associated with the reduction of expected disk friction (hence improvement in shaft torque), while the second is more intricate considering the effect on fluid momentum through reorganization of tangential velocities, based on the mixing zone theory proposed in the paper. The net effect of reducing the volume of nonflow zones (i.e., filling of cavity) is the enhancement of efficiency in the range of 1.3% to 3.6% (±0.4%) in turbine mode. The experimental disk friction coefficient as a function of blade Reynolds number is corroborated with the established theory proposed by different researchers. A significant phenomenon observed was the elimination of vibration and noise at overload operating conditions with the minimal axial clearance.
On Modeling and Simulation of Innovative Ship Rescue System
Authors: Zilakos Ilias , Toulios Michael
Published: July 2018

Inflatable devices that provide reserve buoyancy to damaged ships, preventing capsizing and/or sinking, along with lifting wreckages from the seabed, were studied within the framework of the European funded project “SuSy” (Surfacing System for Ship Recovery). Part of the work involved material evaluation and testing as well as simulations of the structural response. This paper first describes an orthotropic hyperelastic constitutive model for a candidate material also used in the fabrication of prototype inflatable devices. A strain energy density function is proposed that is further used to derive the stress and elasticity tensors required for the numerical implementation of the model in the user-defined subroutine (UMAT) of abaqus/standard. The second part of the paper presents the finite element simulation of the latter stages of inflation of two salvage devices inside an actual double bottom structure. The numerical results are in good agreement with tests conducted in dry land and under water, with the structure raised following the inflation of the devices. The evolving stress state in both the devices and the double bottom structure under increased contact interaction leads to useful conclusions for future use in the development of this salvage system.
Considerations in Using Photometer Instruments for Measuring Total Particulate Matter Mass Concentration in Diesel Engine Exhaust
Authors: Northrop William F. , Zarling Darrick , Li Xuesong
Published: July 2018

In this work, engine-out particulate matter (PM) mass emissions from an off-highway diesel engine measured using a low-cost photometer, scanning mobility particle sizer (SMPS), elemental versus organic carbon (EC/OC) analysis, and a photo-acoustic analyzer are compared. Tested engine operating modes spanned the range of those known to result in high semivolatile particle concentration and those that emit primarily solid particles. Photometer measurements were taken following a primary dilution stage and a sample conditioner to control relative humidity prior to the instrument. Results of the study show that the photometer could qualitatively track total particle mass trends over the tested engine conditions though it was not accurate in measuring total carbon (TC) mass concentration. Further, the required photometric calibration factor (PCF) required to accurately measure total PM mass changes with the OC fraction of the particles. Variables that influence PCF include particle effective density, which changes both as a function of particle diameter and OC fraction. Differences in refractive index between semivolatile and solid particles are also significant and contribute to high error associated with measurement of total PM using the photometer. This work illustrates that it may be too difficult to accurately measure total engine PM mass with a photometer without knowing additional information about the sampled particles. However, removing semivolatile organic materials prior to the instrument may allow the accurate estimation of EC mass concentration alone.
Computational Fluid Dynamics Simulations of the Effect of Water Injection Characteristics on TSCI: A New, Load-Flexible, Advanced Combustion Concept
Authors: Boldaji Mozhgan Rahimi , Sofianopoulos Aimilios , Mamalis Sotirios , Lawler Benjamin
Published: July 2018

Homogeneous charge compression ignition (HCCI) combustion has the potential for high efficiency with very low levels of NOx and soot emissions. However, HCCI has thus far only been achievable in a laboratory setting due the lack of control over the start and rate of combustion and its narrow operating range. In the present work, direct water injection (WI) was investigated to solve the aforementioned limitations of HCCI. This new advanced combustion mode is called thermally stratified compression ignition (TSCI). A three-dimensional computational fluid dynamics (3D CFD) model was developed using CONVERGE CFD coupled with detailed chemical kinetics to gain a better understanding of the underlying phenomena of the water injection event in a homogeneous, low temperature combustion (LTC) strategy. The CFD model was first validated against previously collected experimental data. The model was then used to simulate TSCI combustion and the results indicate that injecting water into the combustion chamber decreases the overall unburned gas temperature and increases the level of thermal stratification prior to ignition. The increased thermal stratification results in a decreased rate of combustion, thereby providing control over its rate. The results show that the peak pressure and gross heat release rate (HRR) decrease by 37.8% and 83.2%, respectively, when 6.7 mg of water were injected per cycle at a pressure of 160 bar. Finally, different spray patterns were simulated to observe their effect on the level of thermal stratification prior to ignition. The results show that the symmetric patterns with more nozzle holes were generally more effective at increasing thermal stratification.
Design for Additive Manufacturing: Optimization of Piping Network in Compact System With Enhanced Path-Finding Approach
Authors: Cao Pei , Fan Zhaoyan , Gao Robert X. , Tang J.
Published: July 2018

This research aims at unleashing the potential of additive manufacturing technology in industrial design that can produce structures/devices with irregular component geometries to reduce sizes/weights. We explore, by means of path-finding, the length minimization of freeform hydraulic piping network in compact space under given constraints. Previous studies on path-finding have mainly focused on enhancing computational efficiency due to the need to produce rapid results in such as navigation and video-game applications. In this research, we develop a new Focal Any-Angle A* approach that combines the merits of grid-based method and visibility graph-based method. Specifically, we formulate pruned visibility graphs preserving only the useful portion of the vertices and then find the optimal path based on the candidate vertices using A*. The reduced visibility graphs enable us to outperform approximations and maintain the optimality of exact algorithms in a more efficient manner. The algorithm proposed is compared to the traditional A* on Grids, Theta* and A* on visibility graphs in terms of path length, number of nodes evaluated, as well as computational time. As demonstrated and validated through case studies, the proposed method is capable of finding the shortest path with tractable computational cost, which provides a viable design tool for the additive manufacturing of piping network systems.
Compliant Assembly Variation Analysis of Scalloped Segment Plates With a New Irregular Quadrilateral Plate Element Via ANCF
Authors: Yu Haidong , Zhao Chunzhang , Lai Xinmin
Published: July 2018

The accurate calculation of deformation during assembly process is important for deviation propagation of large-scale thin-walled hemisphere structures with manufacturing deviations due to the nonuniformed material properties and nonlinear geometrical behavior. In this study, a new irregular quadrilateral plate element based on the absolute nodal coordinate formulation (ANCF) is proposed to discretize the scalloped segment plates with shape deviations. The high-order shape functions of the new element are developed by considering the variable geometrical boundaries. The generalized elastic forces (GEFS) of the new elements for anisotropic and orthotropic materials are derived based on continuum mechanics approach. The bending deviation mode is defined and the evaluation indexes for assembly quality of thin-walled hemisphere structures are proposed. The force equilibrium equations are employed to study the deformation during assembly process for large-scale thin-walled hemisphere structures with multiple scalloped segment plates. The numerical results are compared with that from experimental data and abaqus. The correlation between the assembly quality and the bending deviation, the clamping methods, the geometrical parameters, and the material properties of structures is also investigated.