Showing papers in "Journal of Mechanical Science and Technology in 2017"
TL;DR: In this article, the performance and emission characteristics of a biofuel blend (diesel (40 %)-biodiesel (40 percent)-ethanol (20 %)) (denoted as BE) were compared for addition of Diethyl ether (DEE) and alumina nanoparticle (Al2O3) at various concentrations.
Abstract: The present experimental work is focused on improving the performance and emission characteristics of biofuel blend (diesel (40 %)-biodiesel (40 %)-ethanol (20 %)) (denoted as BE). Comparative analysis was done for addition of Diethyl ether (DEE) and alumina nanoparticle (Al2O3) at various concentrations. The test fuels used are BE, BE with 25 ppm Al2O3 (denoted as BN-1), BE with 50 ppm Al2O3 (denoted as BN-2), BE with 5 % DEE (denoted as BE-1) and BE with 10 % DEE (denoted as BE-2). Experimental results indicate that, DEE addition in BE results in increased HC (Hydrocarbon), CO (Carbon monoxide), CO2 (Carbon dioxide) and BSFC (Brake specific fuel consumption) with lowered NOx (Oxides of nitrogen) and smoke emission. This is attributed to high latent heat evaporation of mixture and Low temperature combustion (LTC). Al2O3addition in BE resulted in increase in NOx and smoke with lowered HC, CO, CO2 and BSFC. This could be attributed to enhanced surface area to volume ratio of mixture during rapid combustion process, higher catalytic combustion and reduced evaporation. At higher engine loads, the peak pressure of BE-1 is highest and that of BE-2 is lowest. Peak heat release rate of BE is highest and BN-1 is lowest. BE blends with additives (Al2O3 and DEE) resulted in higher Particulate matter (PM) formation, however BN-1 blend showed lowered PM at engine loads of 75 % and 100 %. Overall, BE-1 and BN-1 reflects better engine performance, combustion and emission characteristics.
83 citations
TL;DR: In this article, the effect of layer thickness and print orientation on adhesion strength of parts manufactured with 3D printing were experimentally studied and it was found that the edgewise orientation has the highest bonding strength in lower layer thicknesses, while flatwise orientation had the highest binding strength in higher layer layers.
Abstract: Three-dimensional printing is the common name given to various techniques used to manufacture different objects Fused deposition technique is a commonly used additive manufacturing technology in prototyping and production Fused deposition modelling systems are limited in terms of shape and size of parts Printing parts with less support material, for parts too large to print in a single operation or for parts with fine details, sectioning and adhesively bonding is the solution for manufacturing According to adhesion theory, the strength of adhesively bonding between three-dimensional printed parts is affected by surface roughness Effects of layer thickness and print orientation on adhesion strength of parts manufactured with three-dimensional printing were experimentally studied As a result of the study, it was found that the edgewise orientation had the highest bonding strength in lower layer thicknesses, while flatwise orientation had the highest bonding strength in higher layer thicknesses
74 citations
TL;DR: In this article, the thermal performance of a newly prepared nano-enhanced phase change material (NEPCM), constituting SiO2 Nanoparticles (NPs) in myristic acid, was investigated.
Abstract: This paper investigates the thermal performance of a newly prepared Nano-enhanced phase change material (NEPCM), constituting SiO2 Nanoparticles (NPs) in myristic acid. SiO2 NPs with mass fractions of 0.2 wt%, 0.5 wt%, 0.8 wt% and 1.0 wt% were suspended in myristic acid, which serves as the base Phase change material (PCM) separately, to determine the maximum enhancement of thermal conductivity. The size and morphology of the as synthesized SiO2 NPs were studied by Field emission scanning electron microscopy (FESEM). The phase change properties of NEPCMs were assessed with the help of Differential scanning calorimetry (DSC). The thermal conductivity enhancement of NEPCMs was measured using a Laser flash analyzer (LFA). Results clearly indicate that the duration of the melting and solidification processes of NEPCMs decreased compared to that of the base PCM. Thus, the newly prepared NEPCM is a potential candidate for harvesting solar energy for low-temperature heating systems.
60 citations
TL;DR: In this article, a 304L stainless steel was joined to copper by FSW and the optimal values of the welding parameters traverse speed, rotational speed, and tilt angle were obtained through Response surface methodology (RSM).
Abstract: Welding dissimilar metals by fusion welding is challenging. It results in welding defects. Friction stir welding (FSW) as a solid-state joining method can overcome these problems. In this study, 304L stainless steel was joined to copper by FSW. The optimal values of the welding parameters traverse speed, rotational speed, and tilt angle were obtained through Response surface methodology (RSM). Under optimal welding conditions, the effects of welding pass number on the microstructures and mechanical properties of the welded joints were investigated. Results indicated that appropriate values of FSW parameters could be obtained by RSM and grain size refinement during FSW mainly affected the hardness in the weld regions. Furthermore, the heat from the FSW tool increased the grain size in the Heat-affected zones (HAZs), especially on the copper side. Therefore, the strength and ductility decreased as the welding pass number increased because of grain size enhancement in the HAZs as the welding pass number increased.
60 citations
TL;DR: This paper presents a compilation of previous studies on the Stewart platform, which is a class of six degree of freedom parallel manipulators, to discuss the existing methods for the analysis of the Stewartplatform manipulator due to their unique applications.
Abstract: This paper presents a compilation of previous studies on the Stewart platform, which is a class of six degree of freedom parallel manipulators. The abstraction of a parallel manipulator is appropriated for the entire class of it. The paper focuses on the studies in the different fields which are closely checked to determine the direction of research and identify the solved problem areas. A significant investigation has been presented to discuss the existing methods for the analysis of the Stewart platform manipulator due to their unique applications. Studies on analysis and design of the Stewart platform manipulator using flexible joints are included. Modeling and analysis of parallel manipulators by Matlab SimMechanics environment are also highlighted.
57 citations
TL;DR: In this article, an intelligent fault diagnosis method based on Intrinsic Time-Scale Decomposition (ITD)-Singular value decomposition (SVD) and Support vector machine (SVM) is proposed.
Abstract: The gear vibration signal is nonlinear and non-stationary, gear fault diagnosis under variable conditions has always been unsatisfactory. To solve this problem, an intelligent fault diagnosis method based on Intrinsic time-scale decomposition (ITD)-Singular value decomposition (SVD) and Support vector machine (SVM) is proposed in this paper. The ITD method is adopted to decompose the vibration signal of gearbox into several Proper rotation components (PRCs). Subsequently, the singular value decomposition is proposed to obtain the singular value vectors of the proper rotation components and improve the robustness of feature extraction under variable conditions. Finally, the Support vector machine is applied to classify the fault type of gear. According to the experimental results, the performance of ITD-SVD exceeds those of the time-frequency analysis methods with EMD and WPT combined with SVD for feature extraction, and the classifier of SVM outperforms those for K-nearest neighbors (K-NN) and Back propagation (BP). Moreover, the proposed approach can accurately diagnose and identify different fault types of gear under variable conditions.
57 citations
TL;DR: In this paper, the authors investigated the oxidation stability of biodiesel blends at 100 % and 20 % volume concentrations with diesel through induction time determined by Rancimat instrument and concluded that the biodiesel (B100) shows good oxidation stability (I.P = 8.47 h).
Abstract: Use of alcohols blended with biodiesel as alternative fuel in diesel engine is an attractive solution for depletion and demand of fossil fuels in transportation and industrial applications. Calophyllum Inophyllum is a higher oil yielding species with high heating value and notably non-edible oil. One of the most important criteria used for assessing the quality of biodiesel blended fuel is ‘storage oxidation stability’. Deprived oxidation stability is the important technical obstacle associated with the biodiesel commercialization. This study investigated the oxidation stability of biodiesel blends at 100 % (B100) and 20 % (B20) volume concentrations with diesel through induction time determined by Rancimat instrument. Effects of pentanol addition with B20 biodiesel at 10 % (P10) and 15 % (P15) volume concentrations are also analyzed. FTIR spectroscopy characterizes the oxidation variability of all test fuels. It can be concluded that the biodiesel (B100) shows good oxidation stability (I.P = 8.47 h). Addition of pentanol (10 %) enhances the storage ability by 44.57 % than B20, whereas further addition of pentanol (15 %) declines by 19.48 % when compared to P10. More concentration of pentanol weakens the hydrophilic and hydrophobic clusters formed between pentanol/diesel/biodiesel compounds which have been characterized using infra red spectroscopic analysis.
56 citations
TL;DR: In this paper, the influence of ZrO2 and graphite on the mechanical and tribological behavior of aluminum-based metal matrix composite (AA6061) fabricated through the stir casting was investigated.
Abstract: This study investigates the influence of zirconium dioxide (ZrO2) and graphite (C) on the mechanical and tribological behavior of aluminum-based metal matrix composite (AA6061) fabricated through the stir casting. Metal matrix composites (MMC) are prepared with the following weight percentages: 100 % AA; 96 % AA-2 % ZrO2-2 % C; 88 % AA-6 % ZrO2-6 % C; 92 % AA-6 % ZrO2-2 % C; and 96 % AA-2 % ZrO2-6 % C. The microstructure and the mechanical and tribological behavior are characterized, and their correlations are obtained. Microstructural studies of the MMC reveal a uniform distribution of ZrO2 and C particles in the AA6061 matrix. The addition of ZrO2 improves the hardness from 6 % to 12 % (30 HRC to 40.94 HRC) and the ultimate tensile strength from 8 % to 15 % (128 MPa to 166.3 MPa) of the base metal (AA6061). The tribological behavior of wear and the frictional properties of the MMC are also studied by performing dry sliding wear test using pin-on-disc method. Result shows that the minimum and maximum wear rates of MMC are 5 E-9 and 6.2 E-9 (g/mm), respectively, at speed of 850 rpm and constant sliding distance of 1000 m.
54 citations
TL;DR: In this paper, the authors present a new solver for massively parallel simulations of fully three-dimensional multiphase flows based on a parallel implementation of the LCRM hybrid front tracking/level set method.
Abstract: We present a new solver for massively parallel simulations of fully three-dimensional multiphase flows. The solver runs on a variety of computer architectures from laptops to supercomputers and on 262144 threads or more (limited only by the availability to us of more threads). The code is wholly written by the authors in Fortran 2008 and uses a domain decomposition strategy for parallelization with MPI. The fluid interface solver is based on a parallel implementation of the LCRM hybrid front tracking/level set method designed to handle highly deforming interfaces with complex topology changes. We discuss the implementation of this interface method and its particular suitability to distributed processing where all operations are carried out locally on distributed subdomains. We have developed parallel GMRES and Multigrid iterative solvers suited to the linear systems arising from the implicit solution of the fluid velocities and pressure in the presence of strong density and viscosity discontinuities across fluid phases. Particular attention is drawn to the details and performance of the parallel Multigrid solver. The code includes modules for flow interaction with immersed solid objects, contact line dynamics, species and thermal transport with phase change. Here, however, we focus on the simulation of the canonical problem of drop splash onto a liquid film and report on the parallel performance of the code on varying numbers of threads. The 3D simulations were run on mesh resolutions up to 10243 with results at the higher resolutions showing the fine details and features of droplet ejection, crown formation and rim instability observed under similar experimental conditions.
53 citations
TL;DR: A novel rolling bearing fault diagnosis strategy is proposed based on Improved multiscale permutation entropy (IMPE), Laplacian score (LS) and Least squares support vector machine-Quantum behaved particle swarm optimization (QPSO-LSSVM).
Abstract: A novel rolling bearing fault diagnosis strategy is proposed based on Improved multiscale permutation entropy (IMPE), Laplacian score (LS) and Least squares support vector machine-Quantum behaved particle swarm optimization (QPSO-LSSVM). Entropy-based concepts have attracted attention recently within the domain of physiological signals and vibration data collected from human body or rotating machines. IMPE, which was developed to reduce the variability of entropy estimation in time series, was used to obtain more precise and reliable values in rolling element bearing vibration signals. The extracted features were then refined by LS approach to form a new feature vector containing main unique information. By constructing the fault feature, the effective characteristic vector was input to QPSO-LSSVM classifier to distinguish the health status of rolling bearings. The comparative test results indicate that the proposed methodology led to significant improvements in bearing defect identification.
52 citations
TL;DR: In this paper, the authors investigate the flow development of a single bladed vertical axis wind turbine using Computational fluid dynamics (CFD) methods and demonstrate that the turbine is observed to generate negative power at certain azimuth angles.
Abstract: The aim of this study is to investigate the flow development of a single bladed vertical axis wind turbine using Computational fluid dynamics (CFD) methods. The blade is constructed using the NACA 0012 profile and is operating under stalled conditions at tip speed ratio of 2. Two dimensional simulations are performed using a commercial CFD package, ANSYS Fluent 15.0, employing the Menter-SST turbulence model. For the preliminary study, simulations of the NACA 0012 airfoil under static conditions are carried out and compared with available measurement data and calculations using the boundary layer code XFOIL. The CFD results under the dynamic case are presented and the resulting aerodynamic forces are evaluated. The turbine is observed to generate negative power at certain azimuth angles which can be divided into three main zones. The blade vortex interaction is observed to strongly influence the flow behavior near the blade and contributes to the power production loss. However, the impact is considered small since it covers only 6.4 % of the azimuth angle range where the power is negative compared to the dynamic stall impact which covers almost 22 % of the azimuth angle range.
TL;DR: In this paper, five characteristic parameters of Alpha stable distribution (ASD) are identified by fitting the ASD distribution to the vibration acceleration signals and computing the Probability density function (PDF), and kurtosis also has be calculated.
Abstract: When low-speed rolling bearings fail, it is hard to diagnose the extent of their damage. We developed a test rig to simulate the lowspeed rolling bearing operating condition, where bearings with various fault states are installed on the test wheelset and subjected to the same external loading condition. The collected bearing box acceleration time histories are processed with the Empirical mode decomposition (EMD) method combined with kurtosis criterion to filter the trend and noise components. Five characteristic parameters of Alpha stable distribution (ASD) are identified by fitting the ASD distribution to the vibration acceleration signals and computing the Probability density function (PDF). To highlight the advantage of ASD method in feature extraction, kurtosis also has be calculated. Through sensitivity and stability analysis of the six parameters and utilization of Least squares support vectors machine (LSSVM) with Particle swarm optimization (PSO), three most sensitive and stable feature parameters including the characteristic exponent α, the scale factor γ and the peak value of the PDF h are located and applied to evaluate the low-speed rolling bearings’ damage position and damage extent. The proposed method was validated by test data, and the results demonstrated that the ASD characteristics combined with PSO-LSSVM can not only achieve fault diagnosis of low-speed rolling bearings' damage position and damage extent, but also have better diagnosis accuracy and operational efficiency than other methods.
TL;DR: In this paper, an out of the paradigm investigation of electric discharge machining on Si3N4-TiN with copper electrode was conducted. And the significant machining parameters were obtained by Analysis of variance (ANOVA) based on Grey relational analysis (GRA) and value of regression coefficient was determined for each model.
Abstract: Electric discharge machining (EDM) is a highly promising machining process of ceramics. This research is an out of the paradigm investigation of EDM on Si3N4-TiN with Copper electrode. Ceramics are used for extrusion dies and bearing balls and they are more efficient, effective and even have longer life than conventional metal alloys. Owing to high hardness of ceramic composites, they are almost impossible to be machined by conventional machining as it entirely depends on relative hardness of tool with work piece. Whereas EDM offers easy machinability combined with exceptional surface finish. Input parameters of paramount significance such as current (I), pulse on (Pon) and off time (Poff), Dielectric pressure (DP) and gap voltage (SV) are studied using L25 orthogonal array. With help of mean effective plots the relationship of output parameters like Material removal rate (MRR), Tool wear rate (TWR), Surface roughness (Ra), Radial overcut (ROC), Taper angle (α), Circularity (CIR), Cylindricity (CYL) and Perpendicularity (PER) with the considered input parameters and their individual influence were investigated. The significant machining parameters were obtained by Analysis of variance (ANOVA) based on Grey relational analysis (GRA) and value of regression coefficient was determined for each model. The results were further evaluated by using confirmatory experiment which illustrated that spark eroding process could effectively be improved.
TL;DR: In this article, a multi-response optimization approach for the Nd: YAG laser cutting parameters of titanium superalloy sheet (Ti-6Al-4V) was proposed.
Abstract: This study proposes a multi-response optimization approach for the Nd: YAG laser cutting parameters of titanium superalloy sheet (Ti-6Al-4V). The Box-Behnken design was utilized to plan the experiments, and response surface methodology was employed to develop experimental models. Four input parameters, including pulse width, pulse energy, cutting speed, and gas pressure, were set during the experiment, and kerf deviation and metal removal rate were considered as the performance characteristics. Pores, dross, and striation lines were observed on the kerf wall of the laser-cut surface through scanning electron microscopy. With the suitable mathematical models established, a search optimization procedure based on the use of desirability function was used to optimize the performance characteristics. A confirmation experiment was also conducted to validate the optimized process parameters. The relative error is less than ±2 %, thus confirming the feasibility and effectiveness of the adopted approach.
TL;DR: In this article, the authors conducted a numerical study via ADINA 8.8 software on the non-Newtonian pulsatile flow of blood through an elastic blood artery with single and consecutive stenosis.
Abstract: Atherosclerosis develops due to different hemodynamic factors, among which time-averaged Wall shear stress (mean WSS) and Oscillatory shear index (OSI) are two of the most important. These two factors not only depend on flow geometry, but are also influenced by rheological characteristics of blood. Since analytical solutions are limited to simple problems and since experimental tests are costly and time consuming, CFD solutions been prominently and effectively used to solve such problems. We conducted a numerical study via ADINA 8.8 software on the non-Newtonian pulsatile flow of blood through an elastic blood artery with single and consecutive stenosis. The studied stenosis cross sectional area was 70 % that of the unstenosed artery. The single stenosis results were compared with the consecutive stenosis results. The five non-Newtonian flow models, the Carreau model, the Carreau-Yasuda model, the modified Casson model, the power-law model, and the generalized power-law model, were used to model the non-Newtonian blood flow. The obtained results showed that increasing the number of stenoses would lead to reduced length of the oscillatory area after the first stenosis, thus forming another oscillatory area with a larger length after the second stenosis. Thus, a consecutive stenosis would develop a larger disease prone area. Upon examining the mean WSS and OSI, we found that, as compared with the other models, the modified Casson model and the power-law model produced predictions for the most extent of damage to endothelial cells and the most disease prone areas, respectively.
TL;DR: In this paper, a two-frequency, elliptical-vibration texturing (TFEVT) device was designed to be used in a surface texturing process, and its functionality is based on a combination of ultrasonic (> 20 kHz) and low vibration frequencies (> 100 Hz).
Abstract: This study presents the design of a Two-frequency, elliptical-vibration texturing (TFEVT) device. The device was designed to be used in a surface texturing process, and its functionality is based on a combination of ultrasonic (> 20 kHz) and low vibration frequencies (> 100 Hz). The device consists of two parts: The Ultrasonic elliptical motion transducer (UEMT) and the Low frequency displacement amplifier (LFDA). A modal analysis simulation and dynamic experiments were conducted to investigate the dynamic characteristics of the device. The modal simulation was carried out using finite element analysis and the dynamic experiment was evaluated using Frequency response function (FRF) analysis. The working principle of the UEMT is based on a resonance transducer, and the angle between the two Langevin transducers was set as 90°. The UEMT has two vibration modes, symmetric and asymmetric, and according to experimental data, its working frequency is 24 kHz at the 6th resonance vibration mode when a Polycrystalline diamond (PCD) tool is attached. The UEMT is able to generate an elliptical locus that has a vertical amplitude of 1.4 μm and a horizontal amplitude of 0.6 μm, under a phase-shift of 90°. The design of the LFDA is based on a double parallel four-bar flexure hinge, and the displacement output ratio is set to 5. The working principle of the LFDA is based on a non-resonance transducer. The working frequency of the LFDA is below its first of natural frequencies (≈1060 Hz), and it is able to generate sinusoidal motion with a maximum peak-to-peak amplitude of 9 μm. Finally, to investigate the feasibility of the TFEVT device for use in a surface texturing process, several micro-groove cutting tests were performed on an AISI 1045 alloy steel.
TL;DR: In this article, the authors describe the complete design process of a passive prosthetic foot manufactured of Polylactic acid (PLA) and focus on the reduction in the weight of prosthetic feet.
Abstract: This paper describes the complete design process of a passive prosthetic foot manufactured of Polylactic acid (PLA) It focuses on the reduction in the weight of prosthetic feet Most of the prosthetic feet are designed with more weight and material than required The structure of this passive prosthetic foot is designed and optimized as light as possible by using topology optimization The topology-optimized model is printed from a Three-dimensional (3D) printer directly rather than interpreting the model using a Computer-aided design (CAD) software The finite element analysis and the experiments are conducted to validate the structure The test equipment is designed and installed for simulating the boundary conditions of the Heel strike (HS) and Toe off (TO) Since the weight of the prosthetic directly affects the mobility of patients, the weight of the proposed model is reduced 62 % when compared initial model to the final model
TL;DR: In this article, an analytical model is developed in specific mechanical thermal shocking conditions to characterize the smart structures in cubic reconnaissance satellites, based on experimentation and simulation, the optimum resistance is predicted for the various frequencies and temperatures.
Abstract: Piezoelectric materials are widely used as smart structures in cubic reconnaissance satellites because of their sensing, actuating, and energy-harvesting abilities. In this study, an analytical model is developed in specific mechanical thermal shocking conditions. A special circuit and apparatus is designed for experimentation on the basis of the inverse piezoelectric effect. An equivalent circuit method is used to establish the relationship between the resistance and peak-to-peak voltage of lead zirconate titanate used as smart materials for cubic reconnaissance satellites. Various frequencies and resistance were applied in different mechanical thermal shocking conditions. Moreover, numerical simulations are conducted in various mechanical loading conditions to determine the accumulative effect. The model provides a novel mechanism to characterize the smart structures in cubic reconnaissance satellites. A rise in temperature increases peak-to-peak voltage; a rise in frequency decreases peak-to-peak voltage; and intensified resistance decreases peak-to-peak voltage. Based on experimentation and simulation, the optimum resistance is predicted for the various frequencies and temperatures. The various conditions may correspond to the different applications of smart structures for cubic reconnaissance satellites. The analytical calculations are in good agreement with experimental and numerical calculations.
TL;DR: The objective of this work is to optimize the SAW process parameters using a simple optimization algorithm, which is fast, robust and convenient, and is compared with well-known optimization algorithms such as Genetic algorithm (GA), Particle swarm optimization (PSO), Imperialist competitive algorithm (ICA) and Teaching learning based optimization (TLBO).
Abstract: Submerged arc welding (SAW) is characterized as a multi-input process Selection of optimum combination of process parameters of SAW process is a vital task in order to achieve high quality of weld and productivity The objective of this work is to optimize the SAW process parameters using a simple optimization algorithm, which is fast, robust and convenient Therefore, in this work a very recently proposed optimization algorithm named Jaya algorithm is applied to solve the optimization problems in SAW process In addition, a modified version of Jaya algorithm with oppositional based learning, named “Quasi-oppositional based Jaya algorithm” (QO-Jaya) is proposed in order to improve the performance of the Jaya algorithm Three optimization case studies are considered and the results obtained by Jaya algorithm and QO-Jaya algorithm are compared with the results obtained by well-known optimization algorithms such as Genetic algorithm (GA), Particle swarm optimization (PSO), Imperialist competitive algorithm (ICA) and Teaching learning based optimization (TLBO)
TL;DR: In this paper, the effect of relative roughness width and roughness height on heat transfer and friction factor was analyzed by developing CFD code on non-commercial ANSYS (Fluent) 12.1 software.
Abstract: The heat transfer can be improved by providing artificial roughness on absorber plate of the solar air heat. Many studies are available on circular, semi-circular, triangular and rectangular rib roughened solar air heater. But in present study heat transfer enhancement by providing elliptical ribs on absorber plate was analyzed by developing CFD code on non-commercial ANSYS (Fluent) 12.1 software. The simulations were performed on 2-D CFD model and analysis was carried out to study the effect of relative roughness width, relative roughness height and relative roughness pitch on heat transfer and friction factor. The Reynolds number range from 4000 to 15000 and turbulence phenomena is modeled by using Reynolds-average Navier-Stokes equations (RANS). The mathematical modeling is validated and compared with available results. The strong vortex formation takes place in the main stream flow because of elliptical roughness, which improved heat transfer augmentation in the solar air heater. The local turbulence kinetic energy strongly influenced by orientation of the elliptical ribs. The value of average Nusselt number increases by increasing relative roughness height but it decreases with the increase of relative roughness width and relative roughness pitch. The rib width has significant effects on heat transfer enhancement and maximum Nusselt number is observed for relatively small roughness width (i.e., 0.5) among the considered range of 0.5 mm to 2.0 mm. The maximum value of Nusselt number and friction factor is observed for relative roughness width of 0.5, relative roughness height of 0.045, and relative roughness pitch of 6.
TL;DR: In this article, the authors evaluated the 3D flow occurring in the inboard area of an isolated rotor blade operating in stalled conditions, and the delayed detached-eddy simulation approach was applied, and a high-order weighted essentially nonoscillatory scheme was used for flux computation.
Abstract: The present study evaluates the 3D flow occurring in the inboard area of an isolated rotor blade operating in stalled conditions. The delayed detached-eddy simulation approach is applied, and a high-order weighted essentially non-oscillatory scheme is used for flux computation. The load data obtained from available literature are used to validate the numerical computations, and a good agreement is obtained. Three different velocity components, namely, axial, tangential, and radial, are evaluated. An accelerated nozzle flow effect is observed in the root area, generating a distinct root flow vortex that travels downstream in a helical manner. Furthermore, a strong radial flow is observed within the separated flow area that causes 3D effects; this radial flow is strong only in the blade inboard area with a chord to radius ratio (c/r) that is larger than 0.1. Consequently, the 3D lift coefficient in the blade inboard area is remarkably larger compared with the corresponding 2D condition.
TL;DR: In this article, the effect of jet diameter and strut geometry on the near field mixing in strut ramp configuration is discussed for both the fuels, and the numerical results are assessed based on various parameters for the performance evaluation of different strut ramp configurations.
Abstract: The strut-based injector has been found to be one of the most promising injector designs for a supersonic combustor, offering enhanced mixing of fuel and air. The mixing and flow field characteristics of the straight (SS) and Tapered strut (TS), with fixed ramp angle and height at freestream Mach number 2 in conjunction with fuel injection at Mach 2.3 have been investigated numerically and reported. In the present investigation, hydrogen (H2) and ethylene (C2H4) are injected in oncoming supersonic flow from the back of the strut, where jet to freestream momentum ratio is maintained at 0.79 and 0.69 for H2 and C2H4, respectively. The predicted wall static pressure and species mole fractions at various downstream locations are compared with the experimental data for TS case with 0.6 mm jet diameter and found to be in good agreement. Further, the effect of jet diameter and strut geometry on the near field mixing in strut ramp configuration is discussed for both the fuels. The numerical results are assessed based on various parameters for the performance evaluation of different strut ramp configurations. The SS configuration for both the injectant has been found to be an optimum candidate; also it is observed that for higher jet diameter larger combustor length is required to achieve satisfactory near field mixing.
TL;DR: In this paper, Mahua biodiesel- diesel blend and n-butanol diesel blend were determined and compared on eco-friendly and economical basis to gain the suitable substitute fuel for diesel.
Abstract: This study experimentally focuses on finding the optimum blend ratio for Direct injection (D.I) diesel engine fuelled with mahua oildiesel and n-butanol- diesel without any modifications in the engine. Test fuels were prepared by choosing 8 different concentrations as B10 (10 % Biodiesel and 90 % Diesel), B20 (20 % Biodiesel and 80 % Diesel), B30 (30 % Biodiesel and 70 % Diesel), B40 (40 % Biodiesel and 60 % Diesel), BU10 (10 % n-butanol and 90 % Diesel), BU20 (20 % n-butanol and 80 % Diesel), BU30 (30 % n-butanol and 70 % Diesel), BU40 (40 % n-butanol and 60 % Diesel). Experiments were performed at constant speed and variable loads at standard injection timing of 23 Crank angle degree BTDC and standard compression ratio of 16.5:1 to determine the engine performance indicators and exhaust gas emissions such as carbon monoxide, carbon dioxide, hydrocarbon, soot content and oxides of nitrogen. The optimum blend ratio for mahua biodiesel- diesel blend and n-butanol- diesel blend were determined and compared on eco-friendly and economical basis to gain the suitable substitute fuel. The result showed that Mahua biodiesel blend is eco-friendly and economically apt alternative fuel for diesel.
TL;DR: In this article, the impact of grid for accurate prediction of the MEXICO rotor under stalled conditions is investigated. And the results are validated against measurement data with regards to the sectional loads and the chordwise pressure distributions.
Abstract: The present study focuses on the impact of grid for accurate prediction of the MEXICO rotor under stalled conditions Two different blade mesh topologies, O and C-H meshes, and two different grid resolutions are tested for several time step sizes The simulations are carried out using Delayed detached-eddy simulation (DDES) with two eddy viscosity RANS turbulence models, namely Spalart-Allmaras (SA) and Menter Shear stress transport (SST) k-ω A high order spatial discretization, WENO (Weighted essentially nonoscillatory) scheme, is used in these computations The results are validated against measurement data with regards to the sectional loads and the chordwise pressure distributions The C-H mesh topology is observed to give the best results employing the SST k-ω turbulence model, but the computational cost is more expensive as the grid contains a wake block that increases the number of cells
TL;DR: In this article, the authors presented an improved calculation method for the mesh stiffness of helical gears with effect of friction incorporated, and the stiffness difference between cases with and without friction is affected by gear geometry and mounting parameters like module, helix angle and mounting misalignment.
Abstract: As one of the most important excitation sources of vibration, time-varying mesh stiffness of helical gear pairs need accurately calculated. Compared with spur gears, friction in helical gears is significant. This work for the first time presents an improved calculation method for the mesh stiffness of helical gears with effect of friction incorporated. Firstly, helical gear is sliced into number of pieces along its axis direction and each piece could be regarded as spur gear. Then forces applied to each piece including friction force are analyzed. Potential energy method is employed to develop time-varying mesh stiffness of each piece pair of both kinds of helical gears with different transverse and axial contact ratios. Furthermore, influences of various working conditions and misalignment on mesh stiffness are also investigated. Results indicate that effect brought by friction on total mesh stiffness should be not neglected. The reduction amount of stiffness increases with lower speed, heavier load and rougher surface. The stiffness difference between cases with and without friction is affected by gear geometry and mounting parameters like module, helix angle and mounting misalignment. This work provides an essential tool for comprehensive dynamics analysis with consideration of the relationship between stiffness and working conditions.
TL;DR: In this paper, a numerical simulation model was developed to predict the delamination behavior of carbon fiber reinforced aluminum laminates (CARALL) in order to evaluate the interlaminate shear strength of VARTM manufactured CARALL.
Abstract: Carbon fiber reinforced aluminum laminates (CARALL) are one of the aluminum based Fiber metal laminates (FMLs) which, due to their high strength to weight ratio and good impact resistance are greatly replacing aluminum alloys in aircraft structures. In this research work, interlaminate shear strength of Vacuum assisted resin transfer molding (VARTM) manufactured CARALL has been investigated. Numerical simulation model incorporated with real time material data has been developed to predict the delamination behavior of CARALL laminates. Standard CARALL specimens with different surface morphologies were prepared by electric discharge machining, mechanical, chemical and electrochemical surface treatments. T-peel tests were carried out according to standard ASTM D1876-08 to find out inter laminate shear strength. FMLs made out of mechanically, chemically and electrochemically cleaned metal sheets depicted high interlaminate shear strength. SEM micrographs of failed surfaces verify the high adhesive strength of epoxy. Developed numerical simulation model accurately predicts the delamination behavior of CARALL as observed during experimentation.
TL;DR: In this paper, the effect of adding nanoparticles was investigated in relation to the thermal conductivity of lubricants and tribological properties of nanolubricants, and the overall performance of a vapor compression refrigeration system with nanorefrigerants was evaluated.
Abstract: Nanorefrigerants, which are a new class of nanofluids, are mixtures of nanoparticles and refrigerants. They have several potential applications in various fields, such as for refrigeration and air-conditioning systems and heat pumps, among others. Accordingly, adding nanoparticles to conventional refrigerants results in anomalous improvements in the thermophysical properties and heat transfer characteristics of refrigerants, thereby further improving the performance of refrigeration systems. In the present study, R134a-based nanorefrigerant from R134a + CuO/Polyalkylene glycol (PAG) oil nanolubricant was prepared by dispersing copper oxide nanoparticles in the PAG lubricant. The effect of adding nanoparticles was investigated in relation to the thermal conductivity of lubricants and tribological characteristics of nanolubricants. The overall performance of a vapor compression refrigeration system with nanorefrigerants was evaluated. Enhanced heat transfer rate, coefficient of performance, freezing capacity, and reduced power consumption were observed for the refrigeration system. The thermal conductivity of the nanolubricant was better than that of the pure lubricant. Experimental results also showed that the low concentrations of CuO nanoparticles suspended in synthetic oil enhanced the tribological properties of the base oil.
TL;DR: In this article, the authors have made an attempt to establish the optimal combination of control parameters for machining of micro-channels on quartz glass, which is a highly stochastic process involving a number of complex parameters.
Abstract: The electrochemical discharge machining is a highly stochastic process involving a number of complex parameters. Controlling of these process parameters simultaneously to fetch the best possible performance is a difficult task. Determining an optimal parametric combination has become complex owing to interdependency of the parameters. In this work, the authors have made an attempt to establish the optimal combination of control parameters for machining of micro-channels on quartz glass. Taguchi’s standard orthogonal array (L9) with Grey relational analysis (GRA) approach was used to establish the optimal parametric conditions for reducing the Width overcut (WOC) of micro-channels and increasing the Material removal rate (MRR). In order to optimize MRR and WOC together, the optimal combination of the selected control variables was obtained using the GRA. The experimental results showed the effectiveness of the adapted method to indicate the performance of the electrochemical discharge machining process.
TL;DR: In this paper, a self-cleaning and anti-fogging glass surface was fabricated using a non-lithographic, anisotropic etching technique using a predeposited SiO2 film in a glow discharge chamber.
Abstract: Nanostructured transparent glass surfaces with self-cleaning and anti-fogging properties were fabricated using a non-lithographic, anisotropic etching technique. The superhydrophilic glass surface was achieved by nanostructuring pre-deposited SiO2 film in a glow discharge chamber. For superhydrophobicity, the surface energy of the nanostructured glass was lowered by treatment with 1H,1H,2H,2H-perfluorooctyl trichlorosilane. The self-cleaning and anti-fogging behavior was compared for glasses with different wettabilities by measuring the optical transmittance as well as the surface morphology and contact angles. In measuring the anti-fogging behavior, we included the effects of air flow impinging on the glass surface to emulate many practical situations. The superhydrophobic glass was superior to the superhydrophilic glass when considering both the self-cleaning and anti-fogging behavior with durability, particularly under air flow. The work can be used to fabricate transparent glass products for which minimizing surface contamination is crucial, e.g., eyeglasses, solar cells, and optical instruments.
TL;DR: In this article, a new method for the numerical identification of bearing support force coefficients in flexible rotor-bearing systems based on the 3D transient flow calculation is proposed, which can predict the dynamic coefficients of the journal bearing in a rotor bearing system effectively, and provide a further tool for stability analysis.
Abstract: The dynamic coefficients of journal bearing are necessary components in the analysis of linear stability and response of rotating dynamic systems. We propose a new method for the numerical identification of bearing support force coefficients in flexible rotor-bearing systems based on the 3D transient flow calculation. The CFD commercial software FLUENT is mainly used in this simulation, which employs a finite volume method for the discretization of the Navier-Stokes equations. To determine the dynamic coefficients, a new mesh movement approach is presented to update the volume mesh when the journal moves during the 3D transient flow calculation of a journal bearing. Existing dynamic mesh models provided by FLUENT are not suitable for the transient oil flow in journal bearings. Measurements and identification are performed on a test rotor supported on a pair of identical two-lobe fluid film bearings, and the results obtained from the CFD methods agree well with experimental results. The results indicate that the methods proposed in this paper can predict the dynamic coefficients of the journal bearing in a rotor-bearing system effectively, and provide a further tool for stability analysis.