مجله مکانیک سازه ها و شاره ها
سال چهاردهم شماره 2 (خرداد و تیر 1403)

Using the strategy of low-temperature combustion engines is one of the effective solutions to reduce nitrogen oxides; In the present study, a single-zone code was developed considering the detailed chemical kinetic mechanism to investigate the performance of an RCCI engine with WCO-gasoline diesel/biodiesel hybrid fuel. The study of the consumption of chemical species showed that unsaturated fatty acids are consumed more quickly in the combustion process. Diesel consumption speed is also lower than WCO in all loads. According to the results, with an increase in load from 20 to 80%, the moment of starting hot combustion is closer to the moment of starting fuel injection by about 2.5 degrees. Also, with the increase of fuel mass, due to the high proportion of LR fuel, the period of formation of cold ignition becomes shorter. In all cases, the beginning of the production of formaldehyde species is the same time as the beginning of the low temperature heat release and the beginning of the production of the hydroxyl species is the same time as the beginning of the high temperature heat release process.

Considering the challenges related to the level of pollution and the limitation of fossil fuel resources, the design, construction and operation of all-electric ships with on clean energy resources is being developed. On the other hand, due to the prominent features of hydrogen and the possibility of achieving a zero-pollution hydrogen production, , in recent years, hydrogen has received much attention as the main fuel of the future. The growth of the hydrogen usage in the electric transportation industry has also been significant, and in the ships’ industry, the use of hydrogen fuel and the development of fuel cell technology have been significantly developed. In this paper, a conceptual design process of an all-electric fuel cell ship is proposed.To create a comprehensive and systematic approach in the proposed design process, by investigating the phases of internationally recognized projects in the field of design, construction and operation of fuel cell ships, a conceptual design flowchart has been presented. By using this flowchart and having the ship’s input parameters such as power capacity, energy required for each trip, load change rates, ship’s dimensions, fuel tank capacity, available space, and available technologies including fuel cell modules and hydrogen supplyment and storage methods, it is possible to design the basic power system of all-electric hybrid ship based on fuel cell.

The inlet temperature to the nozzle of the turbine engine is one of the most influential parameters in increasing the thrust, Therefore it is necessary to use methods to increase the inlet temperature of the nozzle. impingement cooling is one of these methods, which by passing cooler air and then passing through jets, hits the hot wall of the nozzle and causes the heat of the nozzle wall to be absorbed. In this article, the optimization of impingement cooling system has been investigated in three dimensions. The studied geometry is the end walls of the nozzle, which is in the form of a flat plate. This plate includes cooling holes with a circular cross-section. The optimum design is to find the diameter and distances between of the holes. With coupling of software and the code developed with C programming language, different geometries for hole optimization are generated automatically by determining the appropriate constraints and the design is optimized. The optimization is multi-objective and the optimization algorithm is differential evolution. The goal of optimization is to reach a relatively uniform temperature and also temprature lower than the maximum temperature allowed in the nozzle wall. The results of multi-objective optimization are presented as a Pareto front.

Due to the high pressure of natural gas compression for use in cars, there is always a possibility of danger such as explosion and fire. In this article, the possible scenario of the explosion in the storage tanks of the station has been investigated. First, the explosion in a single 80-liter tank and then the explosion in a group of tanks that form a domino incident are modeled. The results show that at a distance of 2 meters from the explosion site of a single tank, the pressure continues up to 4 bar and the probability of fatality of people in this distance is 99%. At a distance of 16 meters from the explosion site of a group of tanks, the pressure will reach 20 bar and the fatality of people in this range will be 99%. In both modeling modes, the amount of radiation heat flux reaches 37.5 kW⁄m2. Radiation in the explosion of the 80-liter tank covers a radius of 17.66 meters, and in the explosion of a group of tanks, the radius covers a radius of 55 meters, which will lead to the damage of the surrounding buildings and the fatality of people. By comparing the results, safely privacy and the amount of damage have also been predicted. The results of the research can be used to improve safety in the correct use of compressed natural gas and the correct positioning of station equipment.

The purpose of this work is to investigate a different geometry in the parabolic collector in order to increase the thermal efficiency through simultaneous surface and volume absorption in a combined condition. Recently, it has been observed that if the inlet temperature is above 250 °C, Direct absorption collectors can increase efficiency up to 10% Considering that there is a direct relationship between the concentration of nanofluid and the diameter of the transparent tube carrying the fluid with the absorption coefficient, On the other hand, as the concentration of nanofluid increases, fluid sedimentation and system maintenance problems occur. In this research, the amount of nanocarbon used as a suspension of 0.02 gr/l in oil base fluid is considered. According to experimental data, this amount of nano carbon concentration completely absorbs light rays at a depth of 24 (mm) and this absorption coefficient has been used for this specific geometry of the collector. The results show that the rest of the radiation is absorbed on the surface using the central tube, so that the thermal efficiency is up to 6% compared to the usual copper absorption collector, which is about 19 degrees Kelvin.

The most obvious feature of heat sinks is their ability to transfer heat and their cooling properties. In this research, a vertical single-channel active heat sink with Galinstan liquid metal fluid was used and the discretization of Navier Stokes equations was done using the second-order upwind finite volume method. Investigation of Mixed Convection heat transfer with Richardson numbers 0.45, 1 and 10 has been done in both directions of flow from top to bottom and flow direction from bottom to top and the effects of external magnetic field in two directions perpendicular to the flow axis have been investigated. The results showed that the flow direction from bottom to top with a Richardson number of 10 without the presence of a magnetic field improved the Nusselt number by 11.30% compared to the flow direction from top to bottom. With the Richardson number of 1 and the flow direction from bottom to top, the effect of applying the magnetic field in the Z direction (perpendicular to the current axis) with the Hartmann number of 129, 164.5, and 194, respectively, is 11.29, 13.63, and 15.88 percent of the Nusselt number has been improved. With the Richardson number of 1 and the flow direction from the bottom to the top, the effect of applying the magnetic field in the X direction (perpendicular to the flow axis) with the Hartmann number of 64.6, 129 and 194, respectively, is 7.08, 8.28 and 8.76% of the Nusselt number has improved.

Phase change materials (PCMs) can be used in solar water heaters to store excess heat energy available during sunny hours. The purpose of this study is to investigate the performance of the solar water heater system with heat pipe, along with the energy storage system containing phase change materials (PCMs). In this study, a cylindrical galvanized tank with double spiral coil and containing PCM acts as a thermal energy storage unit. Paraffin is used as PCM and water is used as a heat transfer fluid (HTF) to transfer heat from the water heater tank to the spiral tubes and from there to the energy storage tank. The charging and discharging process tests are carried out on sunny days and in real operating conditions. The importance of temperature changes of HTF heat transfer fluid and PCM phase change material as well as the range of changes have been discussed. Functional variables of charge and discharge energy and thermal energy efficiency have been studied. The calculated charging efficiency, 75.7 %and the efficiency of the energy storage unit for the discharge process was 61.1 %. PCM saved 2700 kJ of heat in 70 minutes for 80 ° C during charging and 1650 kJ of heat in 50 minutes at 25 ° C and 42 liters per minute in storage, discharge. He made energy. From the tests, it was found that PCM improves the performance of the system by increasing the charging energy efficiency and the thermal efficiency of the hot water storage tank.

In this research, the presentation and development a robust control algorithm system for stabilization in-wheel motor electric vehicle by implementing the sliding mode control technique is carried out. Based on the proposed algorithm, a shared weight control is implemented between the yaw rate of vehicle and the sideslip angle of the vehicle. Also, a weighting coefficient is used using fuzzy algorithm to control the yaw torque of the vehicle. In the following, the optimal distribution of torque to the four wheels of in-wheel motor electric vehicle, considering the limit of the maximum torque of the electric motor and considering the coefficient of friction of the road surface and tire, is done. Based on the proposed algorithm, a shared weight control is implemented between the yaw rate of vehicle and the sideslip angle of the vehicle. Also, a weighting coefficient is used using fuzzy algorithm to control the yaw torque of the vehicle. The proposed control system is jointly implemented in MATLAB/Simulink-Carsim softwares. The results of the performed simulations show the optimal and effective performance of the proposed control algorithm system.

In this research, the mechanical behavior and the phenomenon of ductile damage of Al5083 are studied and the relationship between the fracture strain and the state of stress at the damage location is presented based on the classic damage models of Johnson-Cook, Rice-Tracy and Hooputra. Based on the results, in the studied stress triaxilality range, the difference between the models is insignificant and each of them can be used with reasonable accuracy. Calibrating of the models has been done using experimental results on the both smooth and notched flat specimens. In order to check the results of the obtained model, the process has been simulated in the Abaqus and its results have been compared with the experimental results. The results of the numerical and experimental simulations were in good agreement and based on them, the extracted model was able to predict the maximum force with the accuracy of more than ±2.5%.

In this article, the mechanical properties of stainless steel are measured at different strain rates. Then, considering the Swift work-hardness equation, the forming limit diagram (FLD) of the sheet has been obtained with two experimental and finite element methods. After designing the experiment based on Box-Behnken method and performing them using the finite element method (FEM), the effect of the input parameters of the radius of the die opening, the distance between the punch and the die, the force of the plate holder, the cutting direction of the primary blank relative to the rolling direction and the coefficient of friction has been obtained on the depth of the product without tearing. Finally, the optimal parameters to achieve the maximum stretching depth have been extracted. After defining the properties extracted from the steel sheet in the software, in order to validate and ensure the accuracy of the finite element analysis, the thickness distribution in a certain path on the experimental product has been compared with the finite element. After designing the experiments and conducting them using the FEM, it was found that in the investigated range, the clearance between the punch and the die has no effect on the depth of tension; Also, by increasing the radius of the opening of the die, the depth of stretching increases. The coefficient of friction has the greatest effect on the depth of stretching and with its decrease, the depth of stretching increases.