نشریه مهندسی مکانیک و ارتعاشات
سال یازدهم شماره 4 (پیاپی 41، زمستان 1399)

Identifying the location, magnitude of nonlinear loads, and the effects of harmonics is one of the most important parts of maintenance planning, troubleshooting, and modification of power systems. Therefore to determine the keying pattern of selective deletion of harmonics, a new salp congestion algorithm has been used which has been applied to a 7-levels inverter and the results have been investigated in different cases. In the following, first, we discuss how to simulate the 7-levels inverter and the harmonic produced by it in MATLAB software, and then the results of the proposed design are reviewed. The results show that using the proposed design since the output line voltage of the 3phase inverter is used, the harmonic is reduced by more than 5% compared to the ground state. In this case, the overall harmonic value of the line voltage is approximately 14%, which has been reduced by 8.73% by normal implementation with offline calculations and by 8.43% by online calculations, which shows the accuracy and the performance of the proposed algorithm is to reduce the harmonic distortion at the output voltage…

This research presents a solar energy recovery system consisting of three main parts including a thermoelectric generator, a convex lens, and a thermal heatsink. The most important feature of the proposed recycling system is its simple structure and design, without complexity and reasonable price. In the design of the recycling system, one side of the thermoelectric is hotted by solar energy, and the other side of the thermoelectric is cooled by the heatsink which is exposed to river water. The temperature gradient is created on both sides of the thermoelectric, which recycles solar energy, resulting in voltage and electrical power. To evaluate the proposed system for solar energy recovery, after its construction, all data and effective parameters on both sides of the thermoelectric generator during the test are recorded every ten minutes, and then the recycling system and information recorded in the engineering equation solver software as codes. Based on the experimental tests, the maximum output voltage of the recycling circuit at a temperature difference of 25 ° C is reported to be 229 mV.

The effect of the amount and type of metal elements in the steel as well as its subsequent effects on microstructure and mechanical properties during the heat treatment process is a proven issue. In this paper, the effect of two important elements, carbon and manganese, on steel 1050 heat treatment, quenching, is investigated. The results of the simulation including, relation between wight percentage variation of them and the effects on surface and depth hardness and also the hardness behavior are analyzed using AC3 software. The elements used in this study were carbon and manganese (%C & %Mn), for either of them the hardness diagram and its behavior at the surface and depth have been prepared. The comparison of the simulation results with the experimental data showed relatively good adaptation. This method can be used in other steels and this software has a very good accuracy to study the effects of elements on the heat treatment of steels.

In this research, the effect of the corrugate inside a two-fluid torsional heat exchanger containing a hybrid water-copper-carbon nanotube nanofluid is investigated numerically using computational fluid dynamics. The geometry of the torsion heat exchanger is prepared using Design Modler software. Also, in order to analyze the fluids, the finite volume method and Ensys Fluent software are used. The hybrid nanofluid stream is in the turbulent and the K Omega turbulence model is used to model it. The geometry of the simple torsional heat exchanger is compared with the torsional heat exchanger with the corrugate and the output results are presented in the form of graphs of mean Nusselt number, pressure drop and PEC index. The study is performed for Reynolds numbers 6000 to 24000, volume fraction of 1 to 5% and three different heights of 1, 2 and 3 mm from the congress. The results obtained from numerical simulation show that the use of water-copper-carbon nanotube hybrid nanofluid causes higher thermal performance than water-based fluid.

Delta wing is studied in several Mach numbers, sweep angles, sharp and curved edges of attack. Algorithm of flow on upper side of the wing is studied and illustrated. Algorithm of flow is compared with the elder studies and changes of these options by Mach number and angle of attack and sweep angle is determined. Illustrations show that on the upper side of the delta wing, a vortex arises that by increasing Mach number, stretches and comes near the wing. Also addition to the primary vortex, secondary vortex arises. In Mach numbers up to 1.2 edge of attack becomes supersonic and expansion waves, accelerate the flow. In higher angles of attack, vortex breakdown occurred that in different Mach numbers and different angles of attack is studied.

In this study, the effect of spinning tape on the thermal hydraulic performance of water-hybrid water-hybrid carbon nanotubes-aluminum oxide inside a linear parabolic solar collector has been investigated numerically. The study is in turbulent flow regime and in order to model it, the k epsilon turbulence model has been used. In order to solve the survival equations, the finite volume method and the SIMPLE C algorithm have been used. The study was performed to investigate the hydraulic and thermal performance of the parabolic solar collector equipped with 1, 2 and 3 twisted strips. Also, the results obtained from the simulation of a linear parabolic solar collector with a radiant strip are compared with when the solar collector is simple (without a radiant strip). Different concentrations of nanoparticles (1 to 3% by volume) were used for Reynolds numbers from 3000 to 18000. The obtained results are presented in the form of Nusselt dimensionless number diagrams, pressure drop and thermal hydraulic performance evaluation criteria(PEC).