behrooz shahriari - Academia.edu (original) (raw)
Papers by behrooz shahriari
Modares Mechanical Engineering, Jan 10, 2020
Scientia Iranica, Aug 30, 2017
In this paper, free vibration analysis of rotating annular disc made of Functionally Graded Mater... more In this paper, free vibration analysis of rotating annular disc made of Functionally Graded Material (FGM) with variable thickness is presented. Elasticity modulus, density, and thickness of the disc are assumed to vary radially according to a power low function. The natural frequencies and critical speeds of the rotating FG annular disc of variable thickness with two types of boundary conditions are obtained employing the numerical Generalized Di erential Quadrature Method (GDQM). The boundary conditions considered in the analysis are both edges clamped (C-C): the inner edge clamped and outer edge free (C-F). The in uence of the graded index, thickness variation, geometric parameters, and angular velocity on the dimensionless natural frequencies and critical speeds is demonstrated. It is shown that we have higher critical speed and natural frequency using a plate with a convergent thickness pro le, and lower critical speed using a divergent thickness pro le. It is found that the increase in the ratio of inner-outer radii could increase the critical speed of the FG annular disk. The results of the present work could improve the design of the rotating FG annular disk in order to avoid resonance condition.
Mechanic of Advanced and Smart Materials
Buckling analysis of the composite stiffened panel in the aircraft's wing was performed. The comp... more Buckling analysis of the composite stiffened panel in the aircraft's wing was performed. The composite panel must meet the requirements of the structure and reduces the weight. For compare the types of stiffeners, the number of skin layers and stiffeners were assumed to be constant at each stage. At first, buckling strength was determined using ABAQUS and it was determined that the Hat-Type stiffener in single state and with the first layup, compared to the T-Type stiffener, 31%, J-Type 35% and the blade-Type, 41% withstand more buckling load. It also with stand higher buckling load for multiple modes and the second type of layup than the T-Type stiffener, 76%, J-Type, 79%, and blade-Type 70%. Next, important parameters such as number, dimensions and different layups on the selected stiffeners were investigated. It was found that the weight of the panel with 2 stiffeners, first layup and cross section 1 is almost equal to the weight of the panel with 3 stiffeners and cross section 3, but the buckling load of the plate with 3 stiffeners is 2.31 and the buckling load of the panel with with 2 stiffeners is 0.89.
Rotating disks function at high temperatures, therm al gradients and angular velocities in aerial... more Rotating disks function at high temperatures, therm al gradients and angular velocities in aerial or la nd gas turbines such as turbojets, turbofans, turboprops and turbojets. These working conditions result in reduced strength of disk mater i l, increased amount of thermal stresses and creation of large centrifugal forces that leads to an increased level of radial a nd ngular stresses. Therefore, thermal analysis of the disk in order to establish appropriate temperature distribution and adequate h eat transfer using an effective cooling mechanism is of peculiar importance. In thi s paper rotating disk problem is modeled in accorda nce with reality. The problem which consists of a rotating disk and cavity in ord er to cool the disk surface is considered. After th at problem is simulated by simultaneously solving flow and energy equations nu merically. The results of the velocity distribution , heat transfer and temperature distribution are comprehensively explained. Further more, te...
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 2017
With the advent of shape memory alloys, several industrial applications were proposed due to thei... more With the advent of shape memory alloys, several industrial applications were proposed due to their superior mechanical and biological properties. Since the fabrication and characterization of shape memory alloy devices is challenging and expensive, it is necessary to simulate their thermomechanical responses before fabrication. To do so, a powerful constitutive model capable of simulation of the important features of these materials is necessary. To be able to simulate a shape memory alloy device, it is vital to implement a suitable constitutive model in such a way to be used in finite element models. In this paper, an existing constitutive model based on microplane theory is numerically implemented and the effects of stress increment, different numerical integration formulas, and loading direction on the thermomechanical response of shape memory alloy is investigated through superelastic and shape memory proportional and nonproportional loadings. The obtained results show that the ...
Periodica Polytechnica Civil Engineering
The dynamic time history analysis is the most accurate method for calculating the structure respo... more The dynamic time history analysis is the most accurate method for calculating the structure response relative to the vibrating load. The use of this method is time-consuming due to the long-duration earthquakes and is generally less commonly used. Wavelet trans-forms are one of the new methods for filtering waves. The duration of a strong ground motion is actually a concept that can be used to turn an earthquake with a long time into an earthquake with a shorter time. In this paper, two concepts of filtration using wavelet transform and the use of a duration of strong ground motion are used for the time history analysis of structures. For this purpose, the acceleration of the earthquake in 5 states was filtered by wavelet transform. In each stage, the high and low frequencies are separated, and the number of earthquake acceleration points is half-past. Then the beginning and the end of the main earthquake and the approximate waves obtained from the wavelet transform are removed usin...
Mechanic of Advanced and Smart Materials
In this paper, an exact analytical solution for thermoelastic analysis of a rotating drum under i... more In this paper, an exact analytical solution for thermoelastic analysis of a rotating drum under internal and external loadings for both homogeneous and FGM materials has been presented. Except for the Poisson's ratio, which is assumed to be constant along drum's radial direction, for FGM state supposed that mechanical properties are varying exponentially. Distribution of thermal function is considered as an arbitrary function of radius. To apply drum's thermal distribution, the heat transfer function in steady-state conditions has been used. After calculating the displacement and stresses, the effect of various parameters which affect stresses and displacements, including rotating speed, types of loading carrying on internal and external surfaces, thickness, and type of material (non-homogeneous constants) have been investigated. Also, the equivalent stress was obtained using Von Mises criteria. The results show that changing the values of noted affecting parameters has significant affection on stresses and displacements reduction and changing type of radial loadings, rotating speed, thickness and choosing FGM material with appropriate FG coefficients instead of homogeneous state can lead to design a drum with lower stresses and consequently higher safety factor.
Acta Mechanica, 2020
The presented paper investigates the nonlinear vibration of a nanobeam with a piezoelectric layer... more The presented paper investigates the nonlinear vibration of a nanobeam with a piezoelectric layer bounded to its top surface considering the nonlocal piezoelectricity theory. To do this, Hamilton’s principle is implemented to derive the governing nonlinear vibration equations of the nanobeam by assumption of nonlocal piezoelectricity and a nonlinear strain–displacement relation. Then, the Galerkin separation method is applied to transform and simplify the partial differential equation of the nonlinear oscillation to an ordinary one with quadratic and cubic nonlinearities in the time domain. By implementing the multiple-scale perturbation method, an analytical relation for the nonlinear natural frequencies is obtained as a function of the oscillation amplitude and the nonlocal size scale parameter. Then, the nonlinear vibration characteristics of the nanobeam are investigated at higher modes of vibration and the size scale effects are reviewed comprehensively. It is observed that the nonlocal parameter decreases the nonlinear natural frequencies and becomes noticeable at higher modes of vibration. Moreover, by increasing the amplitude ratio, the nonlocal effects are decreased and the nonlocal nonlinear frequency approaches the local one. Also, the amplitude ratio has increasing effects on the nonlinear frequencies.
Meccanica, 2018
In recent years, porous shape memory alloys have found several industrial applications. Thanks to... more In recent years, porous shape memory alloys have found several industrial applications. Thanks to biocompatibility, corrosion resistance, and superior mechanical properties, porous NiTi has been introduced as a promising candidate for being used as bone scaffolds. Since the mechanical response of a scaffold is of importance in order to prevent stressshielding phenomena and trigger ossteointegration, predicting the mechanical response of these scaffolds before fabrication is inevitable. In this paper, a new mesoscale model based on Voronoi tessellation of three-dimensional space is presented for the simulation of porous shape memory alloys. To do so, after tessellating the space, some cells are selected randomly to be assigned as pores and a suitable constitutive model of dense SMA is attributed to the other cells. The model is validated against experimental findings reported in the literature demonstrating good agreement. In addition, the effects of number of cells, level of randomness, and the type of boundary conditions on the stress-strain response is assessed. The results show that in order to achieve desirable results, the number of cells and the value of randomness must be chosen greater than minimum corresponding values. As another result, the geometrically periodic model is more computationally efficient than the mechanically periodic one.
Advanced Materials Research, 2014
This paper is focused on the application of Adaptive Nuerofuzzy Inference system (ANFIS) techniqu... more This paper is focused on the application of Adaptive Nuerofuzzy Inference system (ANFIS) techniques in the model-based Fault Detection and Isolation (FDI). The objective of this study has been to create an online system for condition monitoring and diagnosis of specific faults for a Gas Turbine (GT) power plant. In order to study FDI and condition monitoring, accurate model of GT is needed. In this paper, the nonlinear Rowen's model is developed in Matlab/Simulink software to simulate the GT system behavior. Then, regarding the gain of artificial intelligence systems in FDI, the neurofuzzy inference system with capability of reliable learning and data approximating, is employed in developing the proposed FDI algorithm. In this paper, three types of faults have been considered, fault in the fuel flow rate, fault in the performance of turbine which affects the turbine exit gas temperature, and fault in the turbine which affects the turbine output torque. The results illustrate the...
Measurement, 2014
Abstract High speed rotors are vulnerable to vibrations resulting in the failure of the whole ope... more Abstract High speed rotors are vulnerable to vibrations resulting in the failure of the whole operating system. To avoid resonant conditions at operating speeds, modal analysis of such rotors is very important in the design and development of the system. Full rotor dynamic analysis during operating conditions is also mandatory to investigate the dynamic behavior of the rotating structure. In this paper, full dynamic analysis of a high speed rotor with certain geometrical and mechanical properties is carried out using 3D finite element model, one-dimensional beam-type model and experimental modal test. Good agreement between the theoretical and experimental results indicates the accuracy of the finite element models. The Campbell diagram, critical speeds, operational deflection shapes, and unbalance response of the rotor are obtained in order to completely investigate the dynamic behavior of the rotating system.
مهندسی دریا, 2017
Launching pads are among the essential elements of missiles and their main function is to prepare... more Launching pads are among the essential elements of missiles and their main function is to prepare missiles for launch. Tower launchers dimension and configuration depend on effective loads, dimension and weight of the missile. In the majority of tower launchers, two bars connected to each other with crossbar connectors are considered to be the basic parts. Therefore, it is essential to calculate accelerations (forces) applied from ship to structure of the tower launcher. Space frame element is used for designing and a finite element code has been written in MATLAB Software to calculate stress and deformities of the structure. A Genetic algorithm which is codified in MATLAB has been used for optimization. All of the written codes have been compared to experimental data and results confirm the accuracy and exactness of the outcome. In this design weight of the tower launcher was the target equation, displacement and yield stress were constraints and geometrical specifications of the c...
In this research for reducing the effect of losses and increasing the efficiency, the bowing in t... more In this research for reducing the effect of losses and increasing the efficiency, the bowing in the rotor and stator blades is used. In one mode rotor blades are curved and in other one, stator blades are curved. The amount of rotor loss, due to changes in the thickness of the trailing edge and operating rotational speed, have been investigated. To confirm the accuracy of the results, a turbine stage whose experimental results are available is modeled and numerical results have been compared with experimental results that indicate acceptable compliance. The turbulence model k-w-SST is used to solve turbulent flow. The positive bowing, creates a pressure gradient from the two ends of the blade towards the center of the blade, which leads to the directing of the secondary flows toward the center of the blade. This reduces the losses in the two ends of the blade and increases the loss in the middle part of the blade. Increasing the thickness of the trailing edge, as well as increasing ...
The growing demand of energy coupled with decreasing in fossil fuels supplies, on the other hand,... more The growing demand of energy coupled with decreasing in fossil fuels supplies, on the other hand, environmental pollution of fossil fuels and harm effect of it on lives of humans and other creations in world led to research in situated energy resources. The cogeneration or combined heat and power generation (CHP) and distributed generation could be the key strategy to achieve reduce energy consumption and environmental pollution. With considering this facts, thermophotovoltaic (TPV) technology could be very useful. Thermophotovoltaic is a system to convert into electrical energy the radiation emitted from an artificial heat source (i.e. the combustion of fuel) by the use of photovoltaic cells. A domestic gas furnace based on this technology can provide the entire thermal need of an apartment and can also contributes to satisfy the electrical demand. In this research, the initial studies and fundamental concepts in area of thermophotovoltaic and comparison of this technology with oth...
World Academy of Science, Engineering and Technology, International Journal of Mechanical and Mechatronics Engineering, 2014
World Academy of Science, Engineering and Technology, International Journal of Mechanical and Mechatronics Engineering, 2014
Most flexible rotors can be considered as beam-like structures. In many cases, rotors are modeled... more Most flexible rotors can be considered as beam-like structures. In many cases, rotors are modeled as one-dimensional bodies, made basically of beam-like shafts with rigid bodies attached to them. This approach is typical of rotor dynamics, both analytical and numerical, and several rotor dynamic codes, based on the finite element method, follow this trend. In this paper, a finite element model based on Timoshenko beam elements is utilized to analyze the lateral dynamic behavior of a certain rotor-bearing system in operating conditions. Keywords—Finite element method, Operational deflection shape, Timoshenko beam elements, Unbalance response.
The presented article investigates vibration sensitivity analysis of Nano-mechanical piezo-lamina... more The presented article investigates vibration sensitivity analysis of Nano-mechanical piezo-laminated beams with consideration of size effects. To do this, the vibration governing equation of the stepped Nano-mechanical piezo-laminated beam is firstly derived by implementation of the nonlocal elasticity theory. The nonlocal formulation is considered for both of the beam and the piezoelectric layer and the obtained equation is solved analytically. Moreover, there is a need to recognize the importance and relative effects of the beam parameters on the natural frequencies and resonant amplitudes of the nonlocal beam. Therefore, the Sobol sensitivity analysis is utilized to investigate the relative effects of geometrical and the nonlocal parameters on the natural frequencies and the resonant amplitude of the nanobeam. The obtained results show that the length and the thickness of the piezoelectric layer have prominent effects on the vibration characteristics of the beam. Moreover, it is ...
Increasing the temperature of the turbine entrance gases increases the efficiency of the gas turb... more Increasing the temperature of the turbine entrance gases increases the efficiency of the gas turbine cycle. Under these conditions, the combustion chamber wall temperature also increases, while there is no high temperature resistance alloy fitted with air motors. Therefore, it is necessary to use cooling methods to reduce the wall temperature. In this study, the cooling effect with compound angles investigated on the combustion chamber wall temperature. The three-dimensional combustion chamber k-ɛ is modelled under the conditions of the input speed and the turbulence model in the ANSYS Fluent software. Inlet air is injected from the cooled holes to the mainstream with compound angle, where the cooling flow angle is constant with the 30° horizontally, and the lateral angle changes from Beta =0 up to Beta=60 degrees. The combustion chamber has two flat planes and two sloping plates, in which the arrangement of cooling holes is different. The results show that this method better distri...
Modares Mechanical Engineering, Jan 10, 2020
Scientia Iranica, Aug 30, 2017
In this paper, free vibration analysis of rotating annular disc made of Functionally Graded Mater... more In this paper, free vibration analysis of rotating annular disc made of Functionally Graded Material (FGM) with variable thickness is presented. Elasticity modulus, density, and thickness of the disc are assumed to vary radially according to a power low function. The natural frequencies and critical speeds of the rotating FG annular disc of variable thickness with two types of boundary conditions are obtained employing the numerical Generalized Di erential Quadrature Method (GDQM). The boundary conditions considered in the analysis are both edges clamped (C-C): the inner edge clamped and outer edge free (C-F). The in uence of the graded index, thickness variation, geometric parameters, and angular velocity on the dimensionless natural frequencies and critical speeds is demonstrated. It is shown that we have higher critical speed and natural frequency using a plate with a convergent thickness pro le, and lower critical speed using a divergent thickness pro le. It is found that the increase in the ratio of inner-outer radii could increase the critical speed of the FG annular disk. The results of the present work could improve the design of the rotating FG annular disk in order to avoid resonance condition.
Mechanic of Advanced and Smart Materials
Buckling analysis of the composite stiffened panel in the aircraft's wing was performed. The comp... more Buckling analysis of the composite stiffened panel in the aircraft's wing was performed. The composite panel must meet the requirements of the structure and reduces the weight. For compare the types of stiffeners, the number of skin layers and stiffeners were assumed to be constant at each stage. At first, buckling strength was determined using ABAQUS and it was determined that the Hat-Type stiffener in single state and with the first layup, compared to the T-Type stiffener, 31%, J-Type 35% and the blade-Type, 41% withstand more buckling load. It also with stand higher buckling load for multiple modes and the second type of layup than the T-Type stiffener, 76%, J-Type, 79%, and blade-Type 70%. Next, important parameters such as number, dimensions and different layups on the selected stiffeners were investigated. It was found that the weight of the panel with 2 stiffeners, first layup and cross section 1 is almost equal to the weight of the panel with 3 stiffeners and cross section 3, but the buckling load of the plate with 3 stiffeners is 2.31 and the buckling load of the panel with with 2 stiffeners is 0.89.
Rotating disks function at high temperatures, therm al gradients and angular velocities in aerial... more Rotating disks function at high temperatures, therm al gradients and angular velocities in aerial or la nd gas turbines such as turbojets, turbofans, turboprops and turbojets. These working conditions result in reduced strength of disk mater i l, increased amount of thermal stresses and creation of large centrifugal forces that leads to an increased level of radial a nd ngular stresses. Therefore, thermal analysis of the disk in order to establish appropriate temperature distribution and adequate h eat transfer using an effective cooling mechanism is of peculiar importance. In thi s paper rotating disk problem is modeled in accorda nce with reality. The problem which consists of a rotating disk and cavity in ord er to cool the disk surface is considered. After th at problem is simulated by simultaneously solving flow and energy equations nu merically. The results of the velocity distribution , heat transfer and temperature distribution are comprehensively explained. Further more, te...
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 2017
With the advent of shape memory alloys, several industrial applications were proposed due to thei... more With the advent of shape memory alloys, several industrial applications were proposed due to their superior mechanical and biological properties. Since the fabrication and characterization of shape memory alloy devices is challenging and expensive, it is necessary to simulate their thermomechanical responses before fabrication. To do so, a powerful constitutive model capable of simulation of the important features of these materials is necessary. To be able to simulate a shape memory alloy device, it is vital to implement a suitable constitutive model in such a way to be used in finite element models. In this paper, an existing constitutive model based on microplane theory is numerically implemented and the effects of stress increment, different numerical integration formulas, and loading direction on the thermomechanical response of shape memory alloy is investigated through superelastic and shape memory proportional and nonproportional loadings. The obtained results show that the ...
Periodica Polytechnica Civil Engineering
The dynamic time history analysis is the most accurate method for calculating the structure respo... more The dynamic time history analysis is the most accurate method for calculating the structure response relative to the vibrating load. The use of this method is time-consuming due to the long-duration earthquakes and is generally less commonly used. Wavelet trans-forms are one of the new methods for filtering waves. The duration of a strong ground motion is actually a concept that can be used to turn an earthquake with a long time into an earthquake with a shorter time. In this paper, two concepts of filtration using wavelet transform and the use of a duration of strong ground motion are used for the time history analysis of structures. For this purpose, the acceleration of the earthquake in 5 states was filtered by wavelet transform. In each stage, the high and low frequencies are separated, and the number of earthquake acceleration points is half-past. Then the beginning and the end of the main earthquake and the approximate waves obtained from the wavelet transform are removed usin...
Mechanic of Advanced and Smart Materials
In this paper, an exact analytical solution for thermoelastic analysis of a rotating drum under i... more In this paper, an exact analytical solution for thermoelastic analysis of a rotating drum under internal and external loadings for both homogeneous and FGM materials has been presented. Except for the Poisson's ratio, which is assumed to be constant along drum's radial direction, for FGM state supposed that mechanical properties are varying exponentially. Distribution of thermal function is considered as an arbitrary function of radius. To apply drum's thermal distribution, the heat transfer function in steady-state conditions has been used. After calculating the displacement and stresses, the effect of various parameters which affect stresses and displacements, including rotating speed, types of loading carrying on internal and external surfaces, thickness, and type of material (non-homogeneous constants) have been investigated. Also, the equivalent stress was obtained using Von Mises criteria. The results show that changing the values of noted affecting parameters has significant affection on stresses and displacements reduction and changing type of radial loadings, rotating speed, thickness and choosing FGM material with appropriate FG coefficients instead of homogeneous state can lead to design a drum with lower stresses and consequently higher safety factor.
Acta Mechanica, 2020
The presented paper investigates the nonlinear vibration of a nanobeam with a piezoelectric layer... more The presented paper investigates the nonlinear vibration of a nanobeam with a piezoelectric layer bounded to its top surface considering the nonlocal piezoelectricity theory. To do this, Hamilton’s principle is implemented to derive the governing nonlinear vibration equations of the nanobeam by assumption of nonlocal piezoelectricity and a nonlinear strain–displacement relation. Then, the Galerkin separation method is applied to transform and simplify the partial differential equation of the nonlinear oscillation to an ordinary one with quadratic and cubic nonlinearities in the time domain. By implementing the multiple-scale perturbation method, an analytical relation for the nonlinear natural frequencies is obtained as a function of the oscillation amplitude and the nonlocal size scale parameter. Then, the nonlinear vibration characteristics of the nanobeam are investigated at higher modes of vibration and the size scale effects are reviewed comprehensively. It is observed that the nonlocal parameter decreases the nonlinear natural frequencies and becomes noticeable at higher modes of vibration. Moreover, by increasing the amplitude ratio, the nonlocal effects are decreased and the nonlocal nonlinear frequency approaches the local one. Also, the amplitude ratio has increasing effects on the nonlinear frequencies.
Meccanica, 2018
In recent years, porous shape memory alloys have found several industrial applications. Thanks to... more In recent years, porous shape memory alloys have found several industrial applications. Thanks to biocompatibility, corrosion resistance, and superior mechanical properties, porous NiTi has been introduced as a promising candidate for being used as bone scaffolds. Since the mechanical response of a scaffold is of importance in order to prevent stressshielding phenomena and trigger ossteointegration, predicting the mechanical response of these scaffolds before fabrication is inevitable. In this paper, a new mesoscale model based on Voronoi tessellation of three-dimensional space is presented for the simulation of porous shape memory alloys. To do so, after tessellating the space, some cells are selected randomly to be assigned as pores and a suitable constitutive model of dense SMA is attributed to the other cells. The model is validated against experimental findings reported in the literature demonstrating good agreement. In addition, the effects of number of cells, level of randomness, and the type of boundary conditions on the stress-strain response is assessed. The results show that in order to achieve desirable results, the number of cells and the value of randomness must be chosen greater than minimum corresponding values. As another result, the geometrically periodic model is more computationally efficient than the mechanically periodic one.
Advanced Materials Research, 2014
This paper is focused on the application of Adaptive Nuerofuzzy Inference system (ANFIS) techniqu... more This paper is focused on the application of Adaptive Nuerofuzzy Inference system (ANFIS) techniques in the model-based Fault Detection and Isolation (FDI). The objective of this study has been to create an online system for condition monitoring and diagnosis of specific faults for a Gas Turbine (GT) power plant. In order to study FDI and condition monitoring, accurate model of GT is needed. In this paper, the nonlinear Rowen's model is developed in Matlab/Simulink software to simulate the GT system behavior. Then, regarding the gain of artificial intelligence systems in FDI, the neurofuzzy inference system with capability of reliable learning and data approximating, is employed in developing the proposed FDI algorithm. In this paper, three types of faults have been considered, fault in the fuel flow rate, fault in the performance of turbine which affects the turbine exit gas temperature, and fault in the turbine which affects the turbine output torque. The results illustrate the...
Measurement, 2014
Abstract High speed rotors are vulnerable to vibrations resulting in the failure of the whole ope... more Abstract High speed rotors are vulnerable to vibrations resulting in the failure of the whole operating system. To avoid resonant conditions at operating speeds, modal analysis of such rotors is very important in the design and development of the system. Full rotor dynamic analysis during operating conditions is also mandatory to investigate the dynamic behavior of the rotating structure. In this paper, full dynamic analysis of a high speed rotor with certain geometrical and mechanical properties is carried out using 3D finite element model, one-dimensional beam-type model and experimental modal test. Good agreement between the theoretical and experimental results indicates the accuracy of the finite element models. The Campbell diagram, critical speeds, operational deflection shapes, and unbalance response of the rotor are obtained in order to completely investigate the dynamic behavior of the rotating system.
مهندسی دریا, 2017
Launching pads are among the essential elements of missiles and their main function is to prepare... more Launching pads are among the essential elements of missiles and their main function is to prepare missiles for launch. Tower launchers dimension and configuration depend on effective loads, dimension and weight of the missile. In the majority of tower launchers, two bars connected to each other with crossbar connectors are considered to be the basic parts. Therefore, it is essential to calculate accelerations (forces) applied from ship to structure of the tower launcher. Space frame element is used for designing and a finite element code has been written in MATLAB Software to calculate stress and deformities of the structure. A Genetic algorithm which is codified in MATLAB has been used for optimization. All of the written codes have been compared to experimental data and results confirm the accuracy and exactness of the outcome. In this design weight of the tower launcher was the target equation, displacement and yield stress were constraints and geometrical specifications of the c...
In this research for reducing the effect of losses and increasing the efficiency, the bowing in t... more In this research for reducing the effect of losses and increasing the efficiency, the bowing in the rotor and stator blades is used. In one mode rotor blades are curved and in other one, stator blades are curved. The amount of rotor loss, due to changes in the thickness of the trailing edge and operating rotational speed, have been investigated. To confirm the accuracy of the results, a turbine stage whose experimental results are available is modeled and numerical results have been compared with experimental results that indicate acceptable compliance. The turbulence model k-w-SST is used to solve turbulent flow. The positive bowing, creates a pressure gradient from the two ends of the blade towards the center of the blade, which leads to the directing of the secondary flows toward the center of the blade. This reduces the losses in the two ends of the blade and increases the loss in the middle part of the blade. Increasing the thickness of the trailing edge, as well as increasing ...
The growing demand of energy coupled with decreasing in fossil fuels supplies, on the other hand,... more The growing demand of energy coupled with decreasing in fossil fuels supplies, on the other hand, environmental pollution of fossil fuels and harm effect of it on lives of humans and other creations in world led to research in situated energy resources. The cogeneration or combined heat and power generation (CHP) and distributed generation could be the key strategy to achieve reduce energy consumption and environmental pollution. With considering this facts, thermophotovoltaic (TPV) technology could be very useful. Thermophotovoltaic is a system to convert into electrical energy the radiation emitted from an artificial heat source (i.e. the combustion of fuel) by the use of photovoltaic cells. A domestic gas furnace based on this technology can provide the entire thermal need of an apartment and can also contributes to satisfy the electrical demand. In this research, the initial studies and fundamental concepts in area of thermophotovoltaic and comparison of this technology with oth...
World Academy of Science, Engineering and Technology, International Journal of Mechanical and Mechatronics Engineering, 2014
World Academy of Science, Engineering and Technology, International Journal of Mechanical and Mechatronics Engineering, 2014
Most flexible rotors can be considered as beam-like structures. In many cases, rotors are modeled... more Most flexible rotors can be considered as beam-like structures. In many cases, rotors are modeled as one-dimensional bodies, made basically of beam-like shafts with rigid bodies attached to them. This approach is typical of rotor dynamics, both analytical and numerical, and several rotor dynamic codes, based on the finite element method, follow this trend. In this paper, a finite element model based on Timoshenko beam elements is utilized to analyze the lateral dynamic behavior of a certain rotor-bearing system in operating conditions. Keywords—Finite element method, Operational deflection shape, Timoshenko beam elements, Unbalance response.
The presented article investigates vibration sensitivity analysis of Nano-mechanical piezo-lamina... more The presented article investigates vibration sensitivity analysis of Nano-mechanical piezo-laminated beams with consideration of size effects. To do this, the vibration governing equation of the stepped Nano-mechanical piezo-laminated beam is firstly derived by implementation of the nonlocal elasticity theory. The nonlocal formulation is considered for both of the beam and the piezoelectric layer and the obtained equation is solved analytically. Moreover, there is a need to recognize the importance and relative effects of the beam parameters on the natural frequencies and resonant amplitudes of the nonlocal beam. Therefore, the Sobol sensitivity analysis is utilized to investigate the relative effects of geometrical and the nonlocal parameters on the natural frequencies and the resonant amplitude of the nanobeam. The obtained results show that the length and the thickness of the piezoelectric layer have prominent effects on the vibration characteristics of the beam. Moreover, it is ...
Increasing the temperature of the turbine entrance gases increases the efficiency of the gas turb... more Increasing the temperature of the turbine entrance gases increases the efficiency of the gas turbine cycle. Under these conditions, the combustion chamber wall temperature also increases, while there is no high temperature resistance alloy fitted with air motors. Therefore, it is necessary to use cooling methods to reduce the wall temperature. In this study, the cooling effect with compound angles investigated on the combustion chamber wall temperature. The three-dimensional combustion chamber k-ɛ is modelled under the conditions of the input speed and the turbulence model in the ANSYS Fluent software. Inlet air is injected from the cooled holes to the mainstream with compound angle, where the cooling flow angle is constant with the 30° horizontally, and the lateral angle changes from Beta =0 up to Beta=60 degrees. The combustion chamber has two flat planes and two sloping plates, in which the arrangement of cooling holes is different. The results show that this method better distri...