JOURNAL OF MECHANICAL ENGINEERING
Year:2020 | Volume:49 | Issue:4 (89) |Papers Count:32

In this research, by coupling a Navier-Stokes solver with the genetic algorithm, an automated design procedure is prepared to change the three-dimensional shape of the rotor and the stator blades of an axial flow compressor. The lean and sweep angles of the blades are considered to change the shapes of the rotor and stator blades. The structured computational grids are developed based on these files. Setting the appropriate boundary conditions and using the mixing plane, the computational domain is prepared. Then, the steady state and compressible mass and momentum conservation and turbulence equations are solved. In each case, the isentropic efficiency and mass flow rate of the modified compressors are computed. The objective function of optimization algorithm is calculated based on the compressor efficiency. After a specified iteration number, the optimum values of lean and sweep angles are achieved. The proposed method results in 1. 35% improvements in the compressor stage efficiency in design point while; the change in mass flow rate is 1% in comparison with the original compressor.

In this paper, an artificial neural network model is presented to investigate the crack propagation in composite materials under vertical loading mode. A Finite Element model is developed, using ABAQUS software, to simulate the delamination in composite structures under mode 1 loading. A series of mode 1 simulations are carried out for different initial crack lengths and specimen thicknesses. The crack initiation force is calculated for each simulation from the related force-displacement curve. To validate the Finite Element model, the force-displacement curve of a numerical test is compared with the corresponding experimental curve. These data are used later to develop the artificial neural network model, which is capable of predicting the crack initiation force in mode 1 test. The network has two input neurons, which are the initial crack length and the specimen thickness and the crack initiation force is evaluated in the output layer. The good performance of the neural network is shown by comparing its results with finite element simulations. The good agreement between the targets and outputs in the regression plots, indicates that the network response is satisfactory.

Heat exchangers that use the Maisotsenko Cycle have high efficiency despite using evaporative cooling. Therefore, in this study, based on computational fluid dynamics, the simulation of the Maisotsenko Cycle has been investigated. In this paper, the effects of all operational parameters such as temperature, inlet air huidity, air velocity in wet and dry channels, as well as geometric parameters such as the length of the heat exchanger and the height of the channels on the efficiency of heat exchanger have been studied. The simulation results showed that the heat exchanger has a favorable efficiency in different climatic conditions, so that wet efficiency for this heat exchanger varies from 103 to 115, but the increase in humidity will reduce the efficiency and the effectiveness of the heat exchanger. Also, the results showed that an increase in the velocity inside the dry and wet channels, respectively, decreases and increases the efficiency. Finally, the optimum ratio of the mass flow rate of wet channel to dry one is determined to be 1. 3.

In this study, nanocomposites based on epoxy, nano-silica and short glass fibers were prepared with hand molding method. The resin material consisted of epoxy resin and polyamine. Nano-silica and glass fibers, with average length of 6 mm, were added to epoxy polymer matrix in three levels 0, 0. 75 and 1. 5 wt. % for nano-silica and 5, 10 and 15 wt. % for glass fibers, respectively. After sample preparation, tensile tests are performed to study tensile properties of composites and results were compared and analyzed. Results showed that by adding 0. 75 wt. % nano-silica, tensile strength, elastic modulus and elongation increased and by addition 1. 5 wt. % of nano-silica the mentioned properties decreased. On the other hand, adding just glass fibers enhanced elastic modulus continuously and declined tensile strength of the nanocomposite. Furthermore, simultaneous presence of glass fibers and nano-silica caused an enhancement in elastic modulus and a reduction in tensile strength and elongation at break.

In this study, flow dynamics and accelerated flow effects on the various parameters of the wake of a bluff body model Such as Skewness, Kurtosis and Kolmogorov scale length, investigated experimentally. In addition, the effects of acceleration in the rate and trend of variation of the various parameters of the wake studied. The blow open circuit wind tunnel used to simulate fluid flow. An inverter that causes the changes in rotational speed of the wind tunnels electro motor has increased the inlet wind velocity continuously. On all wake positions, flow Accelerate and Increasing velocity creates smaller sized vortices. The passage of time and the increase in velocity do not have any effect on the changes of the skewness and kurtusis parameters in the near wake. By increasing the velocity, the values of the Kolmogorov scale length reduced generally. also; the values of the parameter in the far wake are greater than the close wake. There is a greater energy dissipation in the parts of the wake where the effects of the shear layers are and this causes smaller sized vortices

In this paper a two-dimensional axisymmetric CFD model is used to investigate the effect of bristle pack free length (the distance between bristle pack tip and front plate), fence height (the distance between backing ring and bristle pack tip), bristle pack thickness and clearance (the gap between rotor surface and bristles tip) on leakage flow of brush seals using Reynolds-Averaged-Navier-Stokes (RANS) and non-Darcian porous medium approach. The results show, the leakage flow decreases with increasing the bristle pack thickness and decreasing the fence height while there is almost no change in leakage flow, when increasing the bristle pack free length. The leakage flow of the brush seal increases with increasing the clearance. This work demonstrates that in order to have the minimum leakage, fence height and clearance should have their minimum values and bristle pack thickness should be increased. Moreover, the effect of rotor speed on leakage flow is investigated. As results indicate, increasing the rotational speed leads to a slight decrease in leakage flow.

Damage is a progressive physical process, which at last leads to failure. During the damage process, material experiences some changes such as nucleation, growth, and coalescence of microscopic voids and microcracks. If the metal material is under the plastic strain, some defects like voids and microcracks are created. Increasing the plastic strains, these defects develop and eventually crack is created in the material which causes fracture in it. Therefore, measuring the damage is very important and various methods have been proposed to determine the damage in materials yet. In this paper first, different methods of estimating the ductile damage are presented and then, ductile damage for stainless steel 316L is determined, using the measurement of elasticity modulus and also measurement of velocity of ultrasonic wave propagation methods. Finally, value of critical ductile damage parameter for the material is calculated by each of these methods and compared.

This study has mainly focused on derivation of aerodynamic data for an airship in particular conditions especially at high angles of attack. When such data are inserted into a flight simulator as a closed loop, it is vital to make use of special computational means and methods, so that the ability to send and receive flight conditions would be achieved through an “ in-the-loop” manner. Therefore, using an open source environment such as OpenFOAM is suggested in this regard. Through this study, the aerodynamic coefficients of the airship are calculated by three different CFD approaches and empirical data collected from wind-tunnel tests while geometrical parameters were set for angles of attack between-10 to 20 degrees. In order to achieve aerodynamic goals, air simulation is of great importance. So, the aerodynamic results are compared based on the three methods of calculating fluid "computing" in the loop, the wind tunnel test and the analytical method of the geometric parameters of the ship's aircraft. In this study, the stability of the aircraft, the longitudinal and lateral aspects of the aircraft is examined. Also, by examining the ratio of the coefficients of the lift to the drag, based on the angle of attack, the angle of attack that the aircraft has the best performance is determined.

In addition to variable properties of fluids, heat interaction with ambient, and axial wall conduction, the temperature distribution of a three-fluid heat exchanger, is strongly affected by Geometric and design parameters. Geometric parameters such as exchanger length and tube diameter and design parameters are fluid flow rate and ambient temperature. In this study, the effect of geometric and design parameters on the temperature distribution and effectiveness of a three-fluid heat exchanger with three thermal communication have been investigated. The governing equations on the flow, are simulated considering heat-in-leak to the cold fluid and variable properties of the fluids, and are solved based on the first law of thermodynamics and analytical methods. Cooling the hot fluid and heating the cold fluid, have been considered as the objective of the three-flow heat exchanger, in order to effectiveness investigation. The effect of ambient heat in leak is to increase the cold fluid temperature, leading to a little lift on hot fluid temperature profile, will result in an enhancement in the cold effectiveness and a reduction on hot effectiveness. Increasing ambient temperature, enhances the effects of heat in leak from ambient. An increase in the diameter of outer tube, Where the cold fluid is flowing and is in contact with the ambient, makes the hot and cold temperatures become farther apart in each cross-section, and decreases the hot and cold effectiveness. An increase in the flow rate of the cold fluid, results in a higher hot effectiveness and reduces the cold effectiveness. Due to An increase in the hot flow rate, both the hot and cold effectiveness are enhanced.

In this study, effects of joints design geometry on the weld metal metallurgical transformations and fracture mode in the Hadfield steel welding joints were investigated. For this purpose, initially 4 austenitized sheets with thickness 2 mm were prepared from Hadfield steel. Then joints design with two chamfered V and X forms were prepared and SMAW process was used for welding. The joints mechanical properties were examined by uniaxial tensile machine, charpy impact test and microhardness measuring test. The evaluation of the microstructures of weld metal in welding joints were conducted by optical microscopy and the fracture modes were determined by scanning electron microscopy examination. The results indicated that with using joints design containing chamfered V-shape in comparison with joints design containing chamfered X-shape in the Hadfield steel welded joints, resulted microstructures consisted from smaller grains and more carbide precipitates. Thus higher microhardness and higher yield and tensile strengths were observed. But impact energy and fracture strain was reduced. Also, scanning electron microscopy images indicated the occurrence of ductile fractures in both joints prepared with X and V-shaped chamfered. However as clearly was visible in scanning electron microscopy images, using joints design containing X-shaped chamfered in comparison with joints design containing V-shaped chamfered led to occurrence of more ductile fractures in the Hadfield steel weld joints.

The reconditioning of a diesel-engine crankshaft by welding process and its influence on premature failure of the crankshaft was experimentally investigated. The fracture occurred between the web and the first crankpin where a repair welding process was previously carried out on the crankpin. Macroscopic features of the fracture surface indicated that fatigue damage was the governing failure mechanism. The chemical composition, mechanical properties, hardness, and microstructure of the crankshaft material at two locations, the fractured region and an intact section, were determined. Comparison of the results revealed a substantial difference between the repaired and sound sections. The premature failure of the crankshaft was attributed to an uncontrolled change in microstructure of the repaired section assisted by a high level of stress concentration.

Investigation of the Effect Mixed Hydrophilic and Hydrophobic Fibers in the Gas Diffusion Layer of a Polymer Electrolyte Membrane Fuel Cell

In the present study, a computer program is developed which can be used for thermal analysis of radiators with corrugated louvered fin and flat tube. This program is able to capture all the geometry-dependent aspects of heat transfer regarding these radiators. It also gains the capability of capturing the air flow non-uniformity through the radiator. The program showed a good agreement when it was tested against experimental data. The maximum error in the experimented range of cooling flowrate and air velocity is 5%. Two important parametric studies have been performed on air mal-distribution and radiator aspect ratio effects on the radiator thermal performance. Results show that air mal-distribution reduces thermal performance by 20%. Increasement of aspect ratio introduces up to 45% performance improvement. Finally, a novel efficient geometry for fin profiles has been introduced and its improving effect on thermal performance is shown using the program.

Application of porous structures whose voids are naturally or artificially contain fluids is common in several engineering fields such as plates with foams containing humidity or damping fluids, wooden plates subject to humidity, and bones. In the present paper, impact analysis of the poroelastic plates is accomplished for the first time. In this regard, the constitutive equations of the poroelastic materials are proposed based on Biot’ s theory and then, the governing equations of the impact of the plate are derived based on the classical plate theory and the non-linear Hertz law. The non-linear finite element form of the governing equations is obtained based on Galerkin method and solved using a special algorithm. Newmark’ s numerical time integration method is employed to consider the time-dependency of the resulting equations. Based on the written computer code, effects of various parameters are investigated. Results reveal that presence and flow of the trapped fluid can lead to behaviors that are in contradiction to those of the traditional plates. Furthermore, the contact force, indentation, central deflection of the plate and the bending moment due to the trapped fluid may increase by increasing the diffusion coefficient.

Injection system of a diesel engine is heart of the engine and could have significant effects on its performance. In this paper an annulus nozzle has been considered in the injection system of the Kubota V3300 diesel engine and the engine’ s performance has been investigated by considering different fuel injection pressures and different pressure of the combustion chamber due to the turbocharging. Numerical results show that under turbocharging circumstances, increasing the injection pressure leads to more perfect combustion and the magnitude of SFC decreases to 0. 195. Results also show that increasing the injection pressure during turbocharging lead to the increasing of engine’ s power and torque and to the increasing of pollutants. It is found that in the absence of turbocharging, increasing the injection pressure leads to the increasing of SFC. It is also found that for the injection pressure equal to 60MP, SFC is equal to 0. 21. Numerical results indicate that in the absence of turbocharging, increasing the injection pressure leads to the increase of the engine’ s power, torque and its pollutants. Comparisons between both cases of presence and absence of turbocharging show that amount of soot in the case of turbocharging is less than its amount when the engine is naturally aspirated. These comparisons also show that NO emission in the absence of turbocharging is considerably less than generation of NO in the other case.

Present work considers the thermo-economic analysis of solid oxide fuel cell (SOFC), gas turbine (GT) and steam turbine (ST) hybrid system. The annualized cost is considered to economic analysis and for thermodynamics analysis, the energy equations are solved to obtain the energy efficiency. Directly or indirectly connection of SOFC and GT and also heating the SOFC input reactants with only GT output or the GT output with the after burner output offers four different configurations. These different configurations can cause condition that SOFC and GT have different operating pressure or the same ones, and also can cause different SOFC operating temperatures. Results show that the hybrid system with SOFC and GT direct connection and using only the GT output for heating is the optimum thermodynamics hybrid system with 59. 3% efficiency and 416290 $/year annualized cost for 1000 A/m2 current density. And the hybrid system with these condition is the optimum economic hybrid system with 52. 7% efficiency and 212438 $/year annualized cost for 5000 A/m2 current density.

Microelectromechanical systems as a promising and efficient technologies of present age can bring about a great revolution in the industrial and commercial products. The increasing development of technology requires the use of wireless sensors (without power supply); so the study and modeling of micro energy harvesters is an important issue. In this paper, a micro flow sensor consists of a symmetric multilayer piezoelectric with a micro energy harvester have been modeled and simulated. In order to model this sensor, coupled equations between solid mechanics, fluid mechanics and piezoelectric have been solved with finite volume and finite element method. To ensure the solution, a fully fluid-structure interaction simulation of micro flow sensor in COMSOL Multiphysics have been presented. With the flow rate of 60 micro liter per minute, the transverse displacement of the free end of the beam is 9. 5 Nano meters and the generated voltage is 2. 30 millivolt.

Multilayer insulation using nanofiber materials has been numerically investigated. High surface to volume ratio of nanofibers results an important effect on both the radiation heat transfer and conduction heat transfer. Thus it is considered as an effective spacer of the multilayer insulators for investigation. The radiation heat transfer is calculated considering the optically thick assumption on the fibers and using the diffusion approximation. Thermal conductivity of alumina fiber and carbon nanofiber are determined using experimental results available in the literature. It is presented that the specific extinction coefficient of carbon nanofiber is approximately 31 percent higher than the one of alumina fiber at 500 K. The results show that using carbon nanofiber as the spacer of multilayer insulation improves the insulation performance. Thus it is suggested to be used as the spacer material.

Superhydrophobic surfaces have extensive applications like as heat transfer improvement, surface corrosion reduction, and fluid drag reduction. In this research, micro-nano structures were grown on the copper using an electrochemical process. The electrolyte is a two-component solution composing of Potassium persulfate and Sodium hydroxide. An octa-decane-thiol coating is used to reduce the surface energy. In the following, effects of different papmrters including the duration of the process and the concentration of electrolyte components on the contact angle increment are examined. To investigate the created micro/nano structures building block scanning electron microscopy pictures in different conditions were taken and inspected. X-ray diffraction analysis of samples’ surfaces showed that micro-nano structures are copper oxide (I). The maximum contact angle of 158. 8 degrees was reached after 10 minute of electrochemical process and 24 hour of coating with low surface energy. Also, the durability of the samples exposing to the open air, pure water and seawater are studied. The samples retained their superhydrophobicity property after up to 6 weeks of exposition to the air; in addition, they showed good durability in contact with pure water and sea water.

In the present numerical study, 2D effect of presence of porous media on radiative efficiency in micro combustion chamber is investigated with taking account of conservative equations of momentum, energy and species. The effect of equivalence ratio of mixture and thermal conductivity of combustor wall as key parameters on radiative efficiency are also studied. . Based on simulation results, using of porous media in combustion chamber causes to increase of mean wall temperature and consequently radiation efficiency of micro combustor will increased. moving flame front toward downstream and reduction of maximum flow temperature is as result of applying porous media as well. Furthermore, maximum radiation efficiency is occurred in lean condition of fuel-air mixture. wall thermal conductivities is also perused on radiative efficiency. It is observed that there is an optimum value for conduction heat transfer coefficient of combustor walls, and the combustor material play an important role on radiative efficiency.

In this paper, the velocity graph is used in terms of Crankshaft variation to obtain the pressure graph according to the time of spraying fuel. Time dependent boundary conditions are used with ANSYS FLUENT17. 1 software and C ++ programming code. For mesh independent study, has been used eight different meshes, resulting in an optimal mesh with 1520400 points. For code validation, comparison numerical results with the experimental results show good agreements for two-dimensional model. Threedimensional analysis for different conditions of input and output pressure and the representation of the cavitation contour for the 3-phase mode, with the accuracy of solving the equations of third-order flux vector matrix are done for achieve to the accuracy of the convergence 10-6 and obtaining the mesh node values, and, lastly, corrosion and effects of It has been discussed.

In drilling operation, the surface quality, cutting forces, burr formation mechanism and burr size (height, thickness), tool wear and tool life are considered as the important elements for drilling hole quality assessment which low amount of information is available in this regards. Therefore, on the basis of review of literature, the main aim of this work is to study the effects of MQL and dry lubrication strategies on thrust force, surface quality and burr formation morphology and size (height and thickness) when drilling 6061-T6. According to experimental observations, increased speed and feed rate under dry and MQL modes led to lower burr height, while under lower cutting speed, the direct effect of MQL is sensible. In addition, in dry drilling, lower average surface roughness was monitored. Those chips recorded under dry condition have higher quality and less segmentations on the free surface as compared to those chips recorded under MQL mode, which however resembles more hardness on the chips and higher cutting forces required for drilling operation.

The purpose of this study is the numerical analysis of hyperthermia on the damage of cancerous tissue in the presence of magnetic nanoparticles under the influence of external magnetic field. For this purpose the governing equations continuity, momentum, energy and arrhenius damage equation are coupled and solved by COMSOL, a finite element based code. The blood flow in capillary is assumed as non-newtonian fluid with the Carreau viscosity model. A three dimensional geometric model includes the capillary and surrounding tissue. The results indicated that the temperature of the blood stream increases with the application of the magnetic field, and the surrounding tissue is damaged over time as a result of this heat. The effect of field strength and concentration was also investigated, which was found to correlate with the amount of damaged tissue. In general, this method can be used to degrade the tissues by placing the nearby magnetic field and injecting nanoparticles at low scales.

Reliability-based topology optimization (RBTO) is used to obtain an optimal topology satisfying given constraints, as well as to consider uncertainties in design variables. Most real structures are subjected to different load at different time. This is referred to as multiple load cases. Topology optimization for multiple load cases can consider loads applied at the same time or at different times (by using weight factors). This article presents an approach for RBTO using multiple load cases. The optimal topology obtained by two method in multiple load cases is compared and also the topology obtained by RBTO compared to that obtained by deterministic topology optimization (DTO). The results show that optimal topology obtained through weight factors is more stable than another method when only one load is applied.

Aluminum extrusion processes is a common method for production of prismatic aluminum profiles with identical cross-section. In extrusion process, friction is one of the most important factors and it plays a crucial role in this process. Friction affects the output profile shape, temperature distribution, extrusion load and etc. One of the best methods to control and reduce the friction between different surfaces during extrusion process is using a lubricant. The aim of this paper is studying the effect of lubricant in aluminum extrusion process of the AA6082 alloy by employing the varying friction coefficient between interfaces. For this purpose the finite element analysis has been adopted by using the commercial DEFORM 3D finite element software and in order to verify the obtained results, the experimental results which are available in the literature have been used. The results show that, the friction reduction decreases the required extrusion force and maximum temperature of work piece significantly. In addition, by reducing the amount of friction between interfaces, the more uniform velocity distribution at the output profile is obtained which leads to improvement in the output profile shape and reduction in the dead metal zones.

The purpose of the current study is to investigate the performance of a shell-and-tube heat exchanger in the crude oil distillation unit of Imam Khomeini oil refining company in order to increase its heat exchange duty. The influence of different heat transfer intensification techniques such as using twisted-tape inserts, changing the baffle space and baffle cut of segmental baffles, using external tube fins, and replacing the conventional segmental baffle with helical baffles are investigated and the results are discussed. In order to simulate the heat exchanger performance, an in-house code is developed and utilized. Results show that the most effective techniques are using external tube fins and twisted-tape inserts while changing the baffle space and baffle cut or using helical baffles instead of segmental baffles do not have any effect on the heat transfer enhancement.

In the present study, a series of experimental measurements are carried out over a wide range of water temperatures and air velocities. This relatively wide range of 0. 01 ≤     ≤ 100 was produced using air average velocities of, 0. 1, 0. 3, 0. 9, 2, 4, 5, and 6 m/s and the water temperatures from 20 to 55 ℃ . The Investigations show that the evaporation rate strongly depends on the flow regimes. The results show that the evaporation rate increases with the difference in vapor pressures over both forced convection(0. 01 ≤ Gr  Re ≤ 0. 1), and turbulent mixed convection regimes(0. 15 ≤ Gr  Re ≤ 25). However, the escalation rate of evaporation, decreases with     in the forced convection regime, whereas in the turbulent mixed convection it increases. In addition, over the range of the free convection regime  Gr  Re > 25 , the evaporation rate is affected not only by the vapor pressure difference but also by the density variation.

In this paper, a control system with two layers is analytically designed using prediction-based optimal control method for nonlinear vehicle dynamics. In the first layer, an optimal external yaw moment for stabilizing the vehicle lateral dynamics is designed. After transforming this external yaw moment to differential forces between the four wheels and by using the inverse tire model for extraction of desired longitudinal slips, the desired values are sent to the second layer. In the second layer, each wheel motor regulates the control torque to track the desired slip. Since the energy consumption of battery is important in electric vehicles, considering the optimal control idea for designing the torque vectoring system reduces the battery consumption. Therefore, by examining suitable weighting factors, the electric motors are forced to operate within the admissible range and also the minimum usage of batteries are provided. The simulation results demonstrate that the designed control system has a suitable performance to cope with nonlinearities and consequently stabilizes the vehicle.

Polishing of surfaces by Magnetic Float Polishing, is a non-traditional method of machining. This article aims to study polishing of spherical lenses by magnetic float polishing (MFP). Principle of this method is based on magneto-hydrodynamic behavior of magnetic fluid. Optical lenses which are used in military industry are the most important parts polished by MFP. Because of the Military Binoculars and military camera in the Drones it’ s important that optical lenses used in them, should have a high level of roughness possible. By this method, it is possible to polish such surfaces up to nanometer scales, which traditional methods can not satisfy such precision. Amount of mixing the abrasives in a magnetic fluid, abrasives size, spindle speed and process time are studied in this investigation. At this study, a device was designed and manufactured and transparency and the roughness obtained are two features of the process that has been studied. After designing and applying of MFP, the experiments carried out on it and its results have been analyzed. Finally, after analyzing and optimizing the factors in MFP process experimentally and statistically, a roughness of Rz= 14nm has been obtained and it’ s found that by increasing of the spindle speed and amount of mixing the abrasives in a magnetic fluid and abrasives size, the roughness will be improved at least 10 percent. By Using the MFP for spherical lenses, polishing process is not related to their core radius and it makes the cost savings and speed to be paid. Effective parameters and the regression equations governing the process are also determined.

Tissue Engineering and animal cell culture have received considerable interest over the last few decades. Hollow fiber membrane bioreactor is one of the most modern and efficient type of bioreactors. In the present paper, four hollow fibers inside a bioreactor are simulated using ANSYS FLUENT software package and their effects on the cell environment were studied. In order to optimum design and predict of membrane bioreactor, the flow parameters and concentration distribution of important metabolites such as oxygen and glucose were studied. Investigation the effect of cell concentration and distance from inlet on oxygen and glucose concentrations showed that at high cell concentrations (2×108 cells/ml), by increasing the distance from inlet, caused to decrease the glucose and oxygen concentrations, considerably. Also, increasing the inlet velocity caused to increase the oxygen and glucose concentrations inside the bioreactor. The obtained results from investigation of the bioreactor lengths showed that the glucose and oxygen concentrations did not change along the fibers in different distances from inlet.

International Civil Aviation Organization (ICAO) has proposed alternative solutions for cases when Global Navigation Satellite Systems (GNSS) is blocked. Among them, DME/DME has features that make it as a good and cost-effective option. In this paper, DME/DME navigation is implemented based on Extended Kalman Filter (EKF) and its performance and accuracy from the APNT perspective has been investigated in a real aerial route based on current operable DME network in I. R. IRAN. These investigations show that the integrated aerial navigation via DME/DME cover the specified APNT requirements and their proper dispersal provides the required coverage according to RNAV/RNP requirements.