نشریه یافته های نوین کاربردی و محاسباتی در سیستم های مکانیکی
سال سوم شماره 3 (پاییز 1402)

The piston is the heart of an engine, which is subjected to thermal and mechanical loading, and due to the fact that it withstands extreme fluctuations in temperature and gas pressure, it is considered a very critical part. The aim of this study is to evaluate the effect of oil gallery on the thermo-mechanical stresses for XU7JP/L3 engine piston. For this purpose, first Solidworks software was used to model the XU7JP/L3 engine piston. An oil gallery was also created on the piston head. Then ANSYS software was used to analysis the thermo-mechanical stress of the piston. Finally, the effect of the oil gallery on the thermomechanical stress distribution of the piston was studied. Boundary conditions in thermal and mechanical analysis were extracted from one-dimensional simulation in GT-POWER and MATLAB software. The results of the thermal analysis showed that the oil gallery reduces the temperature of the engine piston by about 12°C. The results of the mechanical analysis showed that the Von-Mises stress in the modified piston is reduced by about 13 MPa. To evaluate properly of thermo-mechanical results, the simulated results is compared with real sample of damaged piston and it has been shown that critical identified areas, match well with areas of failure in the real sample.

Magnetic stem cell delivery is a promising method for imaging and regenerating damaged cells. To increase the accuracy of delivering stem cells to the target tissue, a precise and cost-effective magnetic system is needed. In this research, a method for arranging magnets to improve the efficiency of stem cell transfer has been designed. The effects of these magnets on the movement of stem cells have been investigated. Different magnets with different arrangements were used for stem cell transfer and compared with each other. This research focuses on three categories of nerve-producing stem cells: bone marrow mesenchymal stem cells, nerve stem cells, and induced pluripotent stem cells. The results show that the arrangement of four magnets, with the side magnets of opposite poles, is more accurate in bringing all three types of stem cells to the injury site. The designed magnetic system can improve the accuracy of delivery of various stem cells in the spinal cord compared to previous methods. Also, the results show that the proposed method is more efficient in the neural stem cell category than in other categories. This method can be a good alternative to invasive methods including surgery.

One of the biggest consumers of water is fossil energy plants, and most of this water consumption is in cooling systems. The considered power plant (reference power plant) in this research has a 100 MW unit in full load mode. Cooling towers have a high cooling capacity, but their high-water consumption due to the use of evaporative cooling causes steam to escape from the opening of the tower and be expelled it into the atmosphere. Wet towers provide lower temperatures than dry towers and as a result higher efficiency, but they have high water consumption. In this research, the environmental parameters affecting the compensatory water consumption required by the hybrid cooling towers (wet-dry) are investigated. Using cycle tempo software, simulation has been done to evaluate the performance of hybrid cooling towers in environmental conditions. The comparison of the volume of compensating water in the same cooling cycle, where only the hybrid cooling tower was replaced by the cooling tower, showed that it is possible to reduce the water consumption in the cooling process by 20% by using the hybrid cooling tower. Also, the use of hybrid tower cooling means that the increase in ambient temperature up to 30 degrees does not affect the amount of electricity produced by the power plant, and the amount of electricity produced in the power plant does not change with the increase in air humidity.

Cooling is one of the most important challenges in saving energy and increasing the productivity of many industries. The first serious obstacle in compressing and making heat transfer devices more efficient is the weak properties of heat transfer fluids. The energy efficiency of heat transfer equipment depends on the heat flux changes created in them. The use of common fluids such as water and ethylene glycol as cooling fluids in the cooling system of various heat transfer devices is not the answer to the removal of very high heat flux (tens of megawatts per square meter). Today, nanofluids are made as new heat transfer fluids by adding nanoparticles to fluids that have low heat transfer and by creating changes in the density, specific heat and viscosity of these fluids in order to increase thermal conductivity and improve heat transfer performance. In this research, the results of laboratory research on heat transfer in nanofluids under laminar, turbulent flows and pool boiling are discussed and investigated.

The non-linear vibration analysis of a clamped circular nano-plate is performed using the nonlocal strain gradient model. For this purpose, a combination of the differential form of the nonlocal elasticity theory and strain gradient model, along with Hamilton’s principle, are used in conjunction with the von Kármán nonlinear strain-displacement relationships and Galerkin weighted residual method to discretize the governing equations. The analysis has focused on the effect of nonlocal and material parameter, initial conditions, and frequency number, on the overall behavior of the nano-plate. Using Galerkin method, the system of non-linear differential equations is obtained and the natural non-linear frequencies, as well as the mode shapes, are determined. Results indicate that increasing the parameters of nonlocal and material has a decreasing and increasing effect (respectively) in the frequency ratio in all modes. This indicates that these parameters have a softening and hardening behavior on the plate vibrational behavior respectively. Also, increasing the initial value of deflection produces a rising trend in the frequency ratio for all modes, nonlocal parameter λ and material parameter Ls.

Reducing energy consumption is of great importance today, considering that residential buildings have a significant contribution to energy consumption, so strategies to reduce energy consumption in this sector can have a great impact on reducing energy consumption in countries. In this paper, the energy analysis of a building has been done using the effects of using air gaps in the walls on the amount of energy consumption reduction. In order to check the results, the building design stages were first simulated using AutoCAD maps in DesignBuilder software, and EnergyPlus engine was used for energy calculations. To investigate the effect of using air gap in walls on reducing energy consumption, three different thicknesses of air gap (1cm, 2.5cm and 5cm) were analyzed. The results of energy simulation for these three different walls with the base wall show that the use of air gaps has reduced the total energy consumption and heating and cooling loads in different months of the year in the building, so that the monthly cooling load of the building in the hottest month of the year is 10.3, 12.8 and 14%, and in the coldest month of the year, Also, the annual heating load consumption of the building decreases by 25.7, 30.9, and 33.6 percent, respectively, and the annual cooling load decreases by 8.3, 10, and 10.9 percent, respectively, which is a significant percentage considering the high annual cooling energy consumption of the building.