Research Paper
Thermodynamics and Cumbustion
M. V. S. Murali Krishna; R. P. Chowdary; T. Kishen Kumar Reddy; P. V. K. Murthy
Abstract
Investigations were carried out to evaluate the performance of direct injection diesel engine with medium grade low heat rejection (LHR) combustion chamber and 3 mm air gap insulated piston, 3 mm air gap insulated liner, and ceramic coated cylinder head [ceramic coating with the thickness of 500 µ ...
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Investigations were carried out to evaluate the performance of direct injection diesel engine with medium grade low heat rejection (LHR) combustion chamber and 3 mm air gap insulated piston, 3 mm air gap insulated liner, and ceramic coated cylinder head [ceramic coating with the thickness of 500 µ was made on the inside portion of the cylinder head].The engine had different operating conditions [normal temperature and pre–heated temperature] of crude waste fried vegetable oil (WFVO) which was collected from restaurants, hotels, etc. with varied injector opening pressure and injection timing. Performance parameters and exhaust emissions were evaluated at various values of brake mean effective pressure of the engine, while combustion parameters were determined at full load operation of the engine using special pressure–crank angle software package. Comparative studies were performed between vegetable oil operation and diesel operation in the engine with both versions of the combustion chamber with varied injection timing and injector opening pressure. Conventional engine (CE) showed deteriorated performance, while the engine with medium grade LHR combustion chamber had improved performance with waste fried vegetable oil operation at the recommended injection timing and pressure. Performance of both versions of the combustion chamber improved with advanced injection timing and at higher injector opening pressure compared with CE with pure diesel operation. The optimum injection timing was 32o bTDC (before top dead centre) with conventional engine, while it was 30o bTDC for the engine with LHR combustion chamber and vegetable oil operation. Compared with pure diesel operation in the conventional engine, at manufacturer's recommended injection timing of 27o bTDC, peak brake thermal efficiency increased by 9% at full load operation, brake specific energy consumption decreased by 2%, volumetric efficiency decreased by 13%, smoke levels decreased by 10%, and nitrogen oxide (NOx) levels increased by 44% with waste fried vegetable oil operation in the engine with LHR combustion chamber.
Research Paper
Fracture Mechanics
Kamal Kolasangiani; Mahmoud Shariati; Khalil Farhangdoost
Abstract
Forming limit curves are used as a parameter in finite element analysis to control the material's level of formability. In this research, forming limit diagram (FLD) of SS304L sheet was obtained by ABAQUSfinite element software. In practice, the experimental determination of a forming limit curve is ...
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Forming limit curves are used as a parameter in finite element analysis to control the material's level of formability. In this research, forming limit diagram (FLD) of SS304L sheet was obtained by ABAQUSfinite element software. In practice, the experimental determination of a forming limit curve is a very time-consuming procedure which requires special and expensive equipment. Forming limit diagram (FLD) is derived by the simulation of Erichsen test (out-of-plane stretching test) using hemispherical punch. There are few studies on the prediction of necking time, which is obtained by the application of Pepelnjak algorithm and ductile fracture criterion. In order for the validation, the numerical result of forming limit diagram (FLD) was compared with the experimental and analytical results and a good correlation was observed. Forming limit stress diagram (FLSD) and MSFLD were determined by plotting the principal in-plane stress and FLD corresponding to the onset of necking localization, respectively. Effect of the thickness of the sheet on forming limit curves was investigated and the results showed that increased thickness of the sheet led to raised level of the FLD and MSFLD; but, FLSD did not change considerably.
Research Paper
Heat and Mass Transfer
S. Mohammed Ibrahim; K. Suneetha
Abstract
The present paper was aimed to study the effects of variable thermal conductivity and heat generation on the flow of a viscous incompressible electrically conducting fluid in the presence of a uniform transverse magnetic field, thermal radiation, porous medium, mass transfer, and variable free stream ...
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The present paper was aimed to study the effects of variable thermal conductivity and heat generation on the flow of a viscous incompressible electrically conducting fluid in the presence of a uniform transverse magnetic field, thermal radiation, porous medium, mass transfer, and variable free stream near a stagnation point on a non-conducting stretching sheet. Equations of continuity, momentum, energy, and mass were transformed into ordinary differential equations and solved numerically using shooting method. Velocity, temperature, and concentration distributions were numerically discussed and presented in the graphs. Skin-friction coefficient, the Nusselt number, and Sherwood number on the sheet were derived and discussed numerically. Their numerical values for various values of physical parameters were presented in the tables. It was found that temperature increased with increasing radiation parameter, R, and concentration decreased with increasing the Schmidt number, Sc. The numerical predications were compared with the existing information in the literature and a good agreement was obtained.
Research Paper
Welding
M. Azizpour; M. Ghoreishi; A. Khorram
Abstract
This paper was aimed to report the 3D finite element analysis simulation of laser welding process of Ti6Al4V 1.7 mm sheets in butt joint in order to predict the temperature distribution, hardness, and weld geometry. The butt-joint welds were made using CO2 laser with the maximum power of 2.2 kW in the ...
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This paper was aimed to report the 3D finite element analysis simulation of laser welding process of Ti6Al4V 1.7 mm sheets in butt joint in order to predict the temperature distribution, hardness, and weld geometry. The butt-joint welds were made using CO2 laser with the maximum power of 2.2 kW in the continuous wave mode. A part of the experimental work was carried out to verify the weld geometry with specific weld parameters including power, speed, and focal position. Another part investigated the effect of focal position on the weld bead geometry. Subsequently, the shapes of the molten pool were predicted by the numerical analysis method and compared with the results obtained through the experimentation, which led to finding a good agreement.
Research Paper
Turbulance
S. F. Ahmed; M. S. A. Sarker Sarker
Abstract
The energy equation for turbulent flow of fiber suspensions was derived in terms of second order correlation tensors. Fiber motion of turbulent energy including the correlation between pressure fluctuations and velocity fluctuations was discussed at two points of flow field, at which the correlation ...
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The energy equation for turbulent flow of fiber suspensions was derived in terms of second order correlation tensors. Fiber motion of turbulent energy including the correlation between pressure fluctuations and velocity fluctuations was discussed at two points of flow field, at which the correlation tensors were the functions of space coordinates, distance between two points, and time.
Research Paper
Composite Materials
Y. Bayat; H. Ekhteraei Toussi
Abstract
In many cases, a torsional shaft may be a thick-walled radially inhomogeneous cylindrical object. The hollow shafts made of functionally graded materials (FGMs) are such kind of compositions which were studied in this paper. Cylindrical FG shafts are composed of ceramic and metallic parts with power ...
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In many cases, a torsional shaft may be a thick-walled radially inhomogeneous cylindrical object. The hollow shafts made of functionally graded materials (FGMs) are such kind of compositions which were studied in this paper. Cylindrical FG shafts are composed of ceramic and metallic parts with power function distribution across the radial direction. The ceramic phase is isotropic elastic and the metallic phase was elastic-plastic. In this paper, the volume fraction-based elastic–plastic mixture rule of renowned Tamura–Tomota–Ozawa (TTO) was used to model the behavior of the composite material. The elasto-plastic torsion problem was modeled and solved analytically. The results were compared with the simulations of ABAQUS and the accuracy of the solutions was evaluated. Depending on the thickness and level of inhomogeneity, different modes of yielding were obtained. The results showed that plastic zone could occur at the inner or outer surfaces or simultaneously at both surfaces; even it may start in-between the thickness. Moreover, the influence of material inhomogeneity and thickness of shaft upon the plastic zone development were studied and discussed.
Research Paper
Manufacturing Processes
Mehdi Tajdari; Saeed Zare Chavoshi
Abstract
In the present study, five modeling approaches of RA, MLP, MNN, GFF, and CANFIS were applied so as to estimate the radial overcut values in electrochemical drilling process. For these models, four input variables, namely electrolyte concentration, voltage, initial machining gap, and tool feed rate, were ...
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In the present study, five modeling approaches of RA, MLP, MNN, GFF, and CANFIS were applied so as to estimate the radial overcut values in electrochemical drilling process. For these models, four input variables, namely electrolyte concentration, voltage, initial machining gap, and tool feed rate, were selected. The developed models were evaluated in terms of their prediction capability with measured values. It was clearly seen that the proposed models were capable of predicting the radial overcut. However, the MLP model predicted the radial overcut with higher accuracy than the other models. The statistical analysis showed how much the radial overcut was mainly influenced by voltage and electrolyte concentration during the electrochemical drilling process.
