نشریه علم و فناوری در مهندسی مکانیک
سال سوم شماره 1 (پیاپی 4، بهار و تابستان 1403)

A novel compressed air energy storage system integrated with combined cooling, heating and power is proposed and investigated in this study. The system under study uses sulfur dioxide as the working fluid under the ejector refrigeration system to produce coolant, which has not been used in previous studies, and the waste heat is recovered and stored in the compressed air storage device, which shows the innovative aspect of the present study. A complete and comprehensive thermodynamic and economic analysis is performed on the proposed system. The proposed system is examined from different perspectives and the system performance is quantified through output parameters. Using up-to-date cost functions, the studied system is examined from an economic perspective to clearly demonstrate the cost-effectiveness of the proposed system. In addition, a parametric analysis is performed to evaluate the system behavior by changing key parameters under different operating conditions. The results of the thermodynamic analysis indicate the optimal thermodynamic performance of the proposed system, such that an energy efficiency of 21% and an exergy efficiency of 55% are achieved for the studied system. In addition, an economic analysis yields a total system cost of $232 per gigajoule.

The purpose of this paper is to investigate response of a profile with a square cross section filled with aluminum foam in single and double wall mode under lateral and axial impact load in order to evaluating the effect of using aluminum foam on the energy dissipation caused by the impact. First, single-walled and double-walled square profiles simulated in CAE ABAQUS and the effect of the parameters such as aluminum foam density, number of walls, effect of interaction between foam and wall on general response of model, etc. examined. Then, in order to validate the simulation results, the experimental test of lateral and axial impact using drop weigh impact test performed and the results compared with simulation results. By performing tests and simulations, it was found that aluminum foam has a moderate effect on the amount of crushing and energy absorption of the structure under axial impact load, but in the case of lateral impact, due to high brittleness, the use of foam prepared in the structure under impact is not appropriate. Therefore, it is better to use stronger foam.

The absorber tube is the main part of the solar collectors which its appearance and operational characteristic can play key role in absorbing of solar irradiation amounts. Researchers have proposed various offers to improve the solar collector performance such as inserting a turbulator in the absorber tube and using of nanofluid (especially hybrid nanofluids) instead of simple working fluid. In present study, the various shapes of turbulators proposed by the researchers have been reviewed. Turbulators can be classified according to their shapes. In the first category, turbulency in fluid flow is made by providing ribs or corrugations on the inner wall of absorber tube. But in the second category, external obstacles can be inserted in the absorber tube to improve its performance. Most literatures disscused about the second category of turbulators. By comparing the hydrothermal performance between the smooth absorber tubes with the improved one, it can be concluded that addition of turbulator enhances the thermal properties of all collector types up to 82%. The turbulators can increase the pressure drop and friction factor due to its operation as an obstacle in the fluid flow. Also, the use of nanofluids (especially hybrid nanofluids) beside the turbulators can improve the collector’s performance. However, several characteristics such as the concentration of nano particles, different kinds of hybrid nano fluid and collectors, the various shapes of the turbulator, etc., are all effective parameters on the collector performance.

This study investigated the turbulent flow behavior in a horizontal channel containing elliptical cylinders with aspect ratio 0.45 and 0.5 and Reynolds number 5000. Using the finite element method to solve heat and fluid equations, the effect of parameters such as heat transfer rate, Nusselt number, temperature distribution and velocity distribution on fluid flow has been investigated. The results show that the presence of cylinders increases the vortices and changes the flow patterns from symmetric to asymmetric. Also, as the Reynolds number increases, the flow becomes increasingly turbulent and the rotating mechanics of the cylinders contribute to a different distribution of temperature and velocity. In the investigation of the flow around the elliptical cylinders, it was observed that the maximum temperature point occurs between the third and fourth cylinders in the case of constant properties and behind the fifth cylinder in the case of variable properties. Also, the fluid velocity has a greater effect on the heat transfer rate than the heat exchange surface. The reduction of the aspect ratio leads to the reduction of the heat transfer rate in the turbulent flow and the temperature contours are more uniform in this flow, which is due to the mixing and transverse vibrations of the turbulent flow. These findings can help to improve the design of heat transfer and flow control systems in engineering applications.

Mechanical filtration of solid/liquid phases using pusher centrifuge has been a prevalent operation in industry. The purpose of the current study is the functional and structural analysis of the two-stage pusher centrifuge dynamic performance. In this regard, modal, particle behavior scatter, and transient state dynamic analysis have been considered. The results have revealed a safety margin of 40% for resonance plausibility for the entire set and inner basket subset due to the internal linear and rotary forces. In addition, based on the results of the transient dynamics analysis, the stability of particle behavior has been about 5.5 s or 68% of the particle feeding time, the maximum displacement at the critical point of the inner basket subset was 1.3 mm, and the critical stress on it was about 70 MPa. In overall, it has been recommended to keep the rotational speed as it is (36.68 rad/s), together with the same feed rate as specified (0.56 kg/s).

The aim of this research is to produce a copper alloy matrix composite reinforced with micron diamond particles and to investigate the mechanical properties of this composite. One of the most important issues in the manufacture of this type of composite is to optimize the strength of diamond particles in the metal matrix and the intended wear properties of this type of composite. The composite powders were produced using high-energy (abrasive) milling and hot-press sintering. In order to investigate the flexural strength, hardness and wear properties, samples were manufactured by adding different metals to the matrix, different milling conditions and different hot-pressing parameters. The aim of this research is to produce a copper alloy matrix composite reinforced with micron diamond particles and to investigate the mechanical properties of this composite. One of the most important issues in the manufacture of this type of composite is to optimize the strength of diamond particles in the metal matrix and the intended wear properties of this type of composite. The composite powders were produced using high-energy (abrasive) milling and hot-press sintering. In order to investigate the flexural strength, hardness, and wear properties, samples were fabricated by adding different metals to the matrix, using different milling conditions, and using different hot pressing parameters.

The application of the low temperature combustion (LTC) technology improves the performance and emission characteristics of the engine. However, the most important challenges regarding the integration of this technology in mass-production engines are the limited operating range and uncontrollability. To get the utmost from LTC advantages it is possible to use the diesel combustion in load points undeliverable by LTC. Experimental study in this research on a diesel engine reveals that the change in fuel injection timing from 176 to 2 CAD, bTDC (crank angle degrees before top dead center) leads to the combustion regime change. Fuel injection near top dead center from 11 to 2 CAD,bTDC, resulting in the dependence of the injection and combustion processes, leads to the diesel combustion. In this region, the combustion sensitivity as a measure of fuel injection timing on combustion timing is between 1.2 to 1.3. Advancing the injection to early timings in the compression stroke from 86 to 176 CAD, bTDC and providing enough time for the complete mixing of the fuel and air, yields HCCI combustion having almost zero combustion sensitivity. The fuel injection timing between these ranges, resulting in a mixture which is neither fully homogeneous nor fully stratified, leads to the PPC. In this region, the combustion sensitivity is between 0.1 to 0.2.

This article examines the design and construction of a hardware-based two-axis angle control mechanical device in the loop in order to build a two-axis test bed. This device aims to reach the test bed of two-axis angle control with a small error in order to evaluate and test position sensors or as a small two-degree-of-freedom table to control the position of satellite components. The device consists of two main parts, a mechanical structure and an electronic part, and the control algorithm is written in the hardware platform in the ring, and there is the ability to define all kinds of controllers on it. The structure consists of a rotatable rod, coupling, bearings, body, base and electronic part of a processor board, encoder sensor, battery, telecommunication module and a coreless motor with a rotating disk as a reaction wheel. This device has the ability of pitch and yaw maneuvers as two degrees of freedom, and its position error is proportional to the control algorithm. The reliability of the accuracy of this device per hundred repetitions of the test for the mentioned maneuvers is 0.11 and 0.2 degrees, respectively, with the PID controller. The performance analysis of the device has been investigated in detail by examining different input angles, various controller coefficients, different initial conditions, single-axis and two-axis maneuvers. The obtained results indicate the proper performance of the device with an average error of less than 0.23 degrees.

The combination of aluminum and its alloys with the powder metallurgy process has enabled various industries to take advantage of the advantages of powder metallurgy production while using the unique properties of this light metal. In this research, B4C reinforcement was used to strengthen aluminum alloy 5083, and Al-B4C nanocomposite was produced by mechanical alloying method and then extrusion and press-sintering operations were performed on the powders. Al5083 and Al5083-B4C powders were produced during the alloying process for 24 hours with a pellet to powder ratio of 20:1 and under argon atmosphere. First, the produced powders are compressed by cold press, and then the press-sinter samples are extruded at 600 degrees under nitrogen atmosphere and the extrusion samples are extruded at 505 degrees with an extrusion ratio of 9:1. In the following, the deformation behavior of Al5083 in the temperature range of 550-350 and strain rate of 0.01-0.1 has been studied. Also, a structural equation has been obtained in each of the production states for the silane stress in the form of a hyperbolic sine. The microstructure of the samples produced by both extrusion and press-sintering methods before the hot pressure test was also examined by optical microscope (OM) and scanning electron microscope (SEM) equipped with EDS spectrometer. The results of thermomechanical tests and microstructural studies show that the samples produced by the extrusion method have better mechanical properties than the press-sintered samples.

Natural ventilation is one of the most important passive strategies for reducing building energy consumption, creating thermal comfort, and improving indoor air quality, and is one of the key solutions for achieving sustainability in the construction industry. On the other hand, the potential of natural ventilation is highly dependent on climatic conditions and varies significantly from region to region. In this paper, the feasibility of passive cooling and natural ventilation has been assessed for different cities in Iran. Iranian cities are divided into 9 climates using the Köppen-Geiger climatology method. The impact of climatic conditions on natural ventilation of buildings was assessed using the Köppen-Geiger method and a few selected cities in these climates by the Climate Consultant software using the ASHRAE 55 standard method. By importing the climate parameter file of the selected cities into the Climate Consultant software, the output results including comfort conditions, natural ventilation, and other results were obtained for 9 climates in Iran. The results showed that the climate of Abadan city with 673 hours of natural ventilation provides the most comfort, while the climate of Rasht and Anzali cities with less than 10 hours provide the least comfort using natural ventilation. Also, the cities of Yazd and Sabzevar have the highest potential with 25.8 percent and 22.5 percent per year, respectively, and the cities of Anzali and Meshginshahr have the lowest potential with 0.1 and 0.8 percent, respectively, for using evaporative cooling systems (water coolers).

In this study, a new geothermal energy-based multiple generation system is investigated. This system consists of a modified organic Rankine cycle, a single-effect absorption chiller, and a hydrogen liquefaction cycle that produces power, heat, cold, and liquid hydrogen. In the proposed system, by using geothermal energy as the primary energy source required for liquid hydrogen production, environmental pollution is minimized. The hydrogen gas produced by the electrolyzer in the proposed system is pre-cooled by an absorption heat transformer, and the power consumption of the hydrogen liquefaction cycle is reduced. In the present study, the effect of changes in important performance parameters on the system performance is evaluated. In addition, the optimal performance of the system is investigated using a two-objective genetic algorithm, and the optimal point of the system is obtained using the TOPSIS decision criterion. A complete thermodynamic analysis is performed in the present study, and the results show that an energy efficiency of 42% and an exergy efficiency of 51% are obtained for the proposed system. The economic evaluation conducted in the present study using updated cost functions shows that the total cost of the multiple generation system is $16.37/GJ, which demonstrates the high economic justification of the proposed system.

Under non-ideal weather conditions, distance measuring equipment (DME) must be optimally positioned to reduce landing errors. In this context, interval type-2 fuzzy logic is used as an efficient method for determining the optimal position of the DME. With this method, factors such as weather conditions, flight path, and other related variables are evaluated fuzzily to determine the optimal position of the DME. When unequal distances from the normal landing strip exist for each of the DMEs, it is necessary to identify the most suitable location for the secondary DME. To this end, the system is designed dynamically so that after identifying the assumed centerline based on the initial placement of each DME, the optimal location for the secondary DME is ultimately determined. These conditions only apply if both DMEs have unequal distances. The results show that the use of the Grey Wolf Optimization (GWO) algorithm has a significant impact on improving aircraft landing conditions. With this algorithm, the reduction in the impact of turbulence has increased from 20% to 40%. The probability of landing error has decreased from 10% to 5%, and measurement accuracy has increased from 85% to 95%. These results indicate a substantial improvement in landing safety under non-ideal conditions. Given the reduction in the impact of turbulence and the increase in measurement accuracy, the GWO algorithm plays a crucial role in enhancing the safety and efficiency of aircraft landings.