Journal of Applied and Computational Sciences in Mechanics
Year:2018 | Volume:29 | Issue:2 (18) |Papers Count:10

The main objective of this study is to analyze the performance parameters and simulation of PW615F turbofan engines both with and without secondary combustion chamber. For validation a commercial software called GasTurb & GSP is used. The purpose of the the propulsion system plays an important role in determining of mission and flight regime of an aircraft In this study, the first choice and then simulate a turbine engine thrust which is equivalent to 6. 35 KN produce. And more the method for analyzing on-design and off-design analysis of twin-spool unmixed flow turbofan engines and also we present scaling method to produce the characteristics performance maps of compressor and fans. Mathematical modeling of engine performance has been conducted by serial nested loops algorithm. Performance of components have been modeled by performance diagrams, thermodynamics and gas dynamic equations. Mathematical modeling of a turbofan engine is somewhat complex. Therefore, initially, the off-design performance of a twin spool power generating gas generator and twin spool turbofan are analyzed. Finally, the off-design performance of a twin spool unmixed flow turbofan engine is simulated and the generated performance diagrams have been analyzed. The results show that the cycles that Advantage the secondary combustion chamber dramatically increase the specific thrust, reduce the main secondary combustion chamber outlet emissions and increase the output power of the low pressure turbine.

In the present study the heat transfer of nanofluid flow inside a channel with different arrangements of nanoparticles injection (dispersive elements) is investigated. In the heat transfer phenomena, nanoparticles presence in the fluid flow is known as one of the most important factor for the thermal dispersion. In this work, the distribution of dispersive elements or nanoparticles in the channel is considered to be uniformly distributed in the central region and near the walls. The validation of results is verified by the analytical solution for a simple state of the problem and also by comparison with previous published papers. The presence of the nanoparticels in the center region, increase the Nusselt number and heat transfer characteristics with an ascending form. For the boundary arrangement, increasing the thickness of injected nanoparticles lead to an ascending-descending behavior for Nusselt number. Therefore in this distribution, the optimum thickness for dispersive elements is obtained. Also it can be seen that the presence of the nanoparticels with parabolic distribution increase the Nusselt number with a univocal form. For the exponential arrangement, especially for large values of dispersive coefficient, increasing the Nusselt number has a nonlinear behavior that is the most important distinction of these two distribution functions.

In this study, a linear parabolic trough concentrating photovoltaic/thermal system has been simulated and the effects of using Al2O3/ethylene glycol-water 50: 50 nanofluid with different nanoparticle shapes including platelet, cylindrical, blade and brick shapes from energy and exergy standpoints in the laminar and turbulent regimes have been numerically investigated. The proposed model has been validated using existing experimental results where good agreement was observed. The results indicated that using nanoparticles of cylindrical shape in laminar regime and brick-shaped one in turbulent regime lead to the best system performance compared to others. In addition, applying nanofluid in laminar regime is more effective compared to turbulent regime.

In this paper the steady state radial stagnation point flow impinging on an infinite cylinder has been investigated. The impinging free stream is steady with a constant strain rate k and axis is rotating with constant angular velocity. Similarity solution of the Navier-Stokes and energy equations is presented in this research. A reduced from of these equations are obtained by using appropriate transformations introduced in this study. For all Reynolds numbers, as the particle fraction increases, fluid velocity component in radial and axial directions and axial component of shear-stresses decrease and in the contrary the angular component of shear stress and velocity field and Nusselt number increase.

In this article, an inverse algorithm based on the conjugate gradient method is applied to estimate the unknown location and time-wise varying strength of the point and distributed heat source in functionally graded rectangular plate from the knowledge of temperature measurements taken from the boundaries of plate. It is assumed that no prior information is available on the functional form of timewise variation of the heat source strength so estimation process starts with an arbitrary initial guess. The conjugate gradient method is employed for optimization process and the finite element method is applied to solve the governing differential equations. Results show that the estimation of location and strength of point heat source can be obtained with any arbitrary initial guesses.

The purpose of this paper is to consider the ring systems in the context of a modified gravity theory. In fact, the gravitational stability of a ring system consisted of N particle with the same mass m rotating around a massive object at the center is studied. After finding the equation of motion and considering the dynamics of the system in the equilibrium state, perturbative analysis is used in order to find the linearized version of the equations of motion. Finally using the Fourier analysis, the dispersion relation of the system is derived. At the end, using the observational values of the free parameters of the above mentioned theory and also the dispersion equation the stability criterion of the system for several cases is derived. Finally, the results have been compared with the corresponding results in Newtonian gravity.

In this study, ten novel quadrilateral Kirchhoff’ s bending plate elements based on the Trefftz displacement functions and satisfying equilibrium equation are suggested. First, the most suitable arrangement of degrees of freedom and nodes are achieved by benefiting from previous researches. Afterwards, using the symmetry of terms, ten elements with different interpolation functions for the two top arrangements will be introduced. Numerical tests reveal that the correct choice of the interpolation’ s terms from the incomplete Trefftz functions leads to more efficient elements with lower degrees of freedom and higher order than the complete elements. Since the Trefftz functions meet the equilibrium conditions, the force responses of the most cases have a higher accuracy than the displacement responses.

Bent pipes have been widely used in industrial usage. In this work different materials have been used as mandrel and it is realized that a bunch of flexible wire is more preferable to optimize bending parameters. This way doesn’ t need laborious adjustments and because common flexible wires have plastic deformation even during excessive bending angles, they can be used so many times and also they are easy to remove after bending process. Cross section distortion, cracking at the extrados, wrinkling at the intrados, spring back phenomenon and wall thickness change are issues associated with pipe bending. In this work the effect of flexible wires on bending parameters has been analyzed and the results are confirmed with finite element simulation.

In the present study, the effect of tooth profile modifications on the static transmission error is investigated. The most important factor for investigating noise between two gears is the transmission error. First, the static transmission error is analytically calculated by estimating tooth compliance. The compliance of gear is calculated considering tooth as cantilever beam deflection; rigid body tooth rotation at its base and Hertzian contact. After estimating the static transmission error, tooth profile is modified in four ways: tip relief on the gear teeth only, tip and root relief on the gear teeth only, tip relief on both the gear and pinion teeth and tip and root relief on both the gear and pinion teeth. The results indicate the tip and root relief on both the gear and pinion tooth is the best way for transmission error reduction.

In this paper, an approach for reducing the shaking force of a spherical parallel robot using extra mechanisms is proposed. The proposed method vanishes the Coriolis acceleration terms due to moving the slider links on each branch from force balancing equation. For this purpose, two links are added to each branch of the manipulator as an extra linkage mechanism. Next, three weights are added to each branch of the robot for reducing the applied shaking forces on the base platform. Finally, the dynamic numerical simulations is performed using ADAMS software. The results show a reduction in the applied shaking forces on the base as much as 98%, 79% and 99. 4% along the X, Y and Z axes, respectively.