نشریه مهندسی مکانیک ایران
سال بیست و پنجم شماره 2 (پیاپی 71، تابستان 1402)

In this paper, a sub-coled CAES unit has been investigated to produce electricity and cooling demand during peak times, and energy efficiency and payback period have been calculated in different operational conditions. For this purpose, a computer code has been developed in MATLAB software by solving the relevant equations in repetition process with appropriate time step. The results showed that by increasing the compression and expansion stages, the energy efficiency improves. Also, increasing in compression’s stages, the system payback period has been decreased, while increasing in expansion’s stages, the system’s payback period has been increased. The system has the best its performance when the temperature of tank is equal to that of ambient. In the study of a real sample that provides 900 kW of output power over a period of 4 hours, the payback period for the average price of electricity consumed was 15 cents per kWh, excluding the 8-year inflation rate, but based on the current net value method After 11 years, the proposed system becomes profitable.

In this paper at first the chaotic behavior of a spur gear system is investigated by the use of numerical tools including phase plane trajectories, Poincare’ section and bifurcation diagrams. in order to eliminate the chaotic oscillations, a novel controller on the basis of the predictive sliding mode control is proposed in which the sliding surface is predicted using the model predictive control theory and the control input is obtained. The simulation results of the feedback system depict the effectiveness of the controller in elimination of the chaotic vibrations along with the reduction of settling time, overshoots, and energy consumption.

In some places with hard winters, the heat from sunlight and stored in the soil may not be enough to heat the greenhouse. In such a situation, the additional heat needed must be provided by heating systems. The purpose of this study is to evaluate the effectiveness of the heating system in a glass greenhouse with side air vents and mechanical fans in both night and day periods. In this study, seven different greenhouse designs have been investigated in two periods, day and night. In the daily period, by changing the pressure of the fans, tried to obtain the best condition for providing the appropriate temperature in the greenhouse. Also, in this period, the effect of sunlight on the flow field and temperature changes inside the hall were also investigated. In the night period, the amount of temperature changes by opening and closing the side valves and changing the temperature of the hall floor has been studied. The results of the research show that a greenhouse with a pressure difference of 100 pascal during the day and a greenhouse with a floor temperature of 323.15 K and side vents closed at night have more suitable conditions for growing plants in the off-season.

This paper proposes an adaptive sliding mode control scheme for steer-by-wire (SBW) vehicles subject to tire burst in the presence of uncertainties and external disturbances. To estimate the lateral slip angle of the vehicle after the tire has burst, a sliding mode observer is provided to estimate the lateral slip angle through rotational speed and lateral acceleration measurements. First, an adaptive sliding mode controller (ASMC), as a high-level lateral stability controller, is designed to calculate the modified steering angle and achieve the desired rotational speed and slip angle. In addition, an adaptive rule is included in the control rule to estimate the switching gain so as to overcome the lack of information due to complex uncertainty. The desired steering angle is then created by a lower steering controller via an adaptive sliding mode controller for an SBW wired steering system. The simulation results in MATLAB Simulink and CarSim software show the optimal stability control for different steering maneuvers by bursting the tire. Finally, the comprehensive performance of the adaptive slip mode controller design in tracking the main track and controlling lateral stability is evaluated and discussed.

In this article, considering the existing limitations in changing the length of the linear spring and, on the other hand, the ability to design and manufacture a suitable damper element and nonlinear spring in energy absorbers, the design of a mass and a nonlinear spring with a magnetic eddy current damping element for use in sequential shock excitation has been proposed. In this mechanism, the nonlinear spring and damping element is designed respectively using a telescopic mechanism consisting and neodymium magnet. The nonlinear dynamic equation of the problem is solved using Rong-Kota 4th order and Newmark beta numerical methods. The results show that by selecting the appropriate length of the telescopic arm, in addition to ensuring the convergence of the results, the energy lost can be increased several times compared to the linear mechanism.

In this paper, we investigate a two-effect adsorption refrigeration system that works with ammonium lithium nitrate and sodium ammonia thiocyanate solutions. The energy required by these systems is supplied by a solar collector. The efficiencies of the first and second laws of the absorption refrigeration system are obtained in three parallel and inverse series series arrangements and are compared with each other. In this study, we showed that the amount of energy efficiency and exergy of the two-effect system in the series arrangement is the lowest among the three arrangements. The system works with ammonia solution of lithium nitrate at a lower temperature than the ammonia solution of sodium thiocyanate . Energy consumption is supplied through preheating and collector solar energy. The system with sodium thiocyanate ammonia solution uses more solar energy, which in the lowest case is 29.64% more than the system with sodium thiocyanate ammonia solution. Burning natural gas is the heat that comes from solar energy to get the energy consumed by the generator. bring. The amount of carbon dioxide produced by preheating combustion is obtained, which in its lowest case for a series arrangement with ammonia lithium nitrate solution is 72.16% less than the same arrangement with ammonium sodium thiocyanate.