Journal of Engineering and Thermal Sciences
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Computational investigation of cavitating flow around two dimensional NACA 4424 and MHKF-240 hydrofoil
Get PDFThis study focuses on the comparison of the performance of two unsymmetrical hydrofoils, NACA 4424 and MHKF-240 at 60 angle of attack under cavitation. The Schnerr and Sauer cavitation model along with Realizable k-ε turbulence model is used for numerical computation in commercial software ANSYS Fluent. The lift, drag and pressure coefficients for different cavitation numbers were studied. Among both the hydrofoils MHKF-240 gives a higher lift coefficient which is the parameter of better performance
Dynamic load computational modelling of containers placed on a flat wagon at railroad ferry transportation
Get PDFThe article presents result of computational modelling of container dynamic load during transportation as a part of trains of intermodal transport on a railway ferry. The computational models were developed which account the movement of the container with regard to the frame of the flat wagon while moving of the railway ferry. It was assumed that there is no movement of the flat wagon with regard to the deck, since these movements were limited by fastening means. The obtained acceleration rates, as components of the dynamic loads acting on the container, were accounted while determining the containers stability coefficient with regard to the flat wagons. The railway ferry heeling angles which ensure the stability of the containers were determined. The researches will ensure safety of transportation of containers as a part of trains of intermodal transport on a railway ferry, as well as increase the efficiency of operation of intermodal transport in the international transport
Influence of ultrasonic vibration on discrete media filled tubes during forward extrusion
Get PDFThe coupled deformation of composite structures of discrete media filled thin-walled tubes under the action of forces is a complicate mechanical process, especially when it is superimposed with external vibration. A Jenike shear cell connected with an ultrasonic exciting system was used to test the friction angles of the aggregations of ferric powder and steel ball under quasi-static and high frequency vibration conditions; then forward extrusion of Al6061 tubes filled with these discrete materials under different conditions were examined by experiment and numerical simulation. The results showed that the friction angles of both the discrete materials decreased under vibration, and those of the powders were reduced more, indicating that the “surface effect” of vibration on the particles with smaller granularity is more obvious. Under the combining action of “volume” and “surface” effects of vibration, the extrusion loads of the structures significantly decrease with the superposition of vibration, meanwhile the loads of the tubes filled with powders reduced more. With the imposed vibration, the density of fillers after forming are higher and the tube wall thickness distribution is more uniform
Experimental study on secondary bearing mechanism of weakly cemented broken rock mass
Get PDFIn order to study the secondary bearing mechanism of weakly cemented broken surrounding rock, the surface of granite, limestone and mudstone broken rock samples were poured by cement slurry, and the weakly cemented rock mass was formed by static pressure infiltration method, and then an uniaxial loading test was carried out. The results show that the weakly cemented broken rock mass has a certain bearing capacity, but the bearing capacity is low, and the dispersion is high. The secondary bearing capacity of weakly cemented rock mass is affected by factors such as broken rock strength, rock particle size and rock gradation. The larger the rock particle size and strength are, the higher the secondary bearing capacity of the weakly cemented rock mass is. The average bearing capacity of the mudstone weak cementation specimen is 18.77 kN, and the residual bearing capacity is 1.46 kN, and a dispersion coefficient is 0.34. The average bearing capacity of granite is 343.65 kN, and the residual carrying capacity is 25.81 kN, and a dispersion coefficient is 0.11. The average bearing capacity of limestone is 367.22 kN, and the residual carrying capacity is 22.78 kN, and a dispersion coefficient is 0.3. After a certain grading, the average residual secondary bearing capacity of the weakly cemented rock mass is obviously improved, and the dispersion coefficient of peak bearing capacity is reduced. The grading scheme 1 has an average peak carrying capacity of 330.06 kN, a residual carrying capacity of 34.56 kN, and a dispersion coefficient is 0.07. The averaging scheme 2 has an average peak carrying capacity of 297.8 kN, a residual carrying capacity of 29.86 kN, and a dispersion coefficient is 0.14. The cementation regeneration mechanism of the broken rock mass mainly includes the cement-bonding effect of the cement slurry inside and on the broken rock mass. Under the loaded condition, the internal load-bearing network of the broken rock mass is the main mechanism for the secondary load of the broken rock mass, and the stability of the force-chain network is affected by the constraint. After the loss of the confinement, the force chain network fails, and the residual secondary bearing mechanism of the weakly cemented broken rock mass is transformed into the friction between the broken rock masses in the residual core rock pillar
Computational fluid dynamics (CFD) modelling of hybrid photovoltaic thermal system
Get PDFIn this paper an attempt has been made to simulate and evaluate the distribution of temperature and heat flux for the hybrid photovoltaic thermal system with CFD (computational fluid dynamics) module in ANSYS 19.1 software. The simulation was carried to determine the temperature and heat flux across the different layers of HPVT (hybrid photovoltaic thermal) system. The temperature and heat flux were found to gradually decrease from the top glass layer to the bottom tedlar layer. The temperature varied from 36.4 °C (ambient) to 26.8 °C across the layers from top glass layer to bottom tedlar layer. The heat flux of (561.2 W/m2) at the glass layer due to solar insolation was also found to gradually decrease with the increasing thickness. The reduction in temperature and heat flux with increasing thickness is attributed to fluid flowing beneath the system. The water flowing beneath the tedlar layer takes the excess heat out of the photovoltaic layer, thereby increasing the efficiency of the hybrid photovoltaic thermal system
Modelling and simulation on behaviours of mild steel
Get PDFThe objective of the paper is to simulate the behaviours of mild steel at different strain rates (1-1500s-1) under tension and compression by using finite element analysis code in ANSYS. Numerical simulation are done using Cowper-Symonds (C-S) and Johnson-Cook (J-C) material models to represent the flow stresses of mild steel. The simulated results have good agreement with the predicted results of the above material models
Near-field acoustic holography for high-frequency weak sound sources under low signal-to-noise ratio
Get PDFThe mechanical noise in the cabin of the ship is so large that the leakage of high-pressure fluid is not easily noticed. In view of this situation, a near-field acoustic holography for high-frequency weak sound source under low signal-to-noise ratio is proposed. The method uses the empirical mode decomposition method to add weights to the time-domain sampling signals of each array element, and then uses the plane equivalent source near-field acoustic holography combined with compressive sensing to find the holographic surface acoustic pressure distribution. The simulation and experiment show that this method has certain feasibility under low signal-to-noise ratio, and the results are better than the method based on Fourier transform and the traditional boundary element method. It is of positive significance to apply it to engineering practice
Analysis of vibration based windmill coupled micromachined energy harvester
Get PDFThe present work exploits the centripetal, Coriolis and Euler forces generated in a rotating windmill. The MEMS device is placed on the blade of a windmill to harvest the energy. Modal analysis is carried out to optimize the dimensions of the structure to match the desired conditions. The real time response of the structure and the voltage generated in the piezoelectric layer are evaluated using transient analysis. It was noticed that Euler and Coriolis forces have a significant contribution in the initial time when the wind turbine accelerates from rest. The later portion is dominated by the Coriolis and Euler forces, and in some instances they cancel out each other. However, there is always a steady contribution from the centripetal force which is proportional to the magnitude of angular velocity of the wind turbine
PCA based health indicator for remaining useful life prediction of wind turbine gearbox
Get PDFFault prognosis of wind turbine gearbox has received considerable attention as it predicts the remaining useful life which further allows the scheduling of maintenance strategies. However, the studies related towards the RUL prediction of wind turbine gearbox are limited, because of the complexity of gearbox, acute changes in the operating conditions and non-linear nature of the acquired vibration signals. In this study, a health indicator is constructed in order to predict the remaining useful life of the wind turbine gearbox. Run to fail experiments are performed on a laboratory scaled wind turbine gearbox of overall gear ratio 1:100. Vibration signals are acquired and decomposed through continuous wavelet transform to obtain the wavelet coefficients. Various statistical features are computed from the wavelet coefficients which return form high-dimensional input feature set. Principal component analysis is performed to reduce the dimensionality and principal components (PCs) are computed from the input feature set. PC1 is considered as the health indicator and subjected to further smoothening by linear rectification technique. Exponential degradation model is fit to the considered health indicator and the model is able to predict the RUL of the gearbox with an error percentage of 2.73 %
Effect of in-wheel motor suspension system on electric vehicle ride comfort
Get PDFThis paper presents the effect of in-wheel motor (IWM) suspension system on electric vehicle (EV) ride comfort. To analyze the impact on the vehicle ride comfort caused by IWM suspension system, a dynamic model of quarter vehicle is established with the combination of IWM and road surface roughness excitations. The weighted root-mean-square (r.m.s.) acceleration of the vertical vehicle body (awbz) according to the international standard ISO 2631-1 (1997) is selected as an objective function to analyze the effect of IWM suspension system when the road surface and IWM mass conditions change. The study results indicate that the effect of IWM suspension system on the EV ride quality is significant and the value of awbz reduces by 8.6 % in comparison to without IWM suspension system. The IWM suspension system has significantly improved the EV ride quality when the road surface and IWM mass conditions change