نشریه مهندسی مکانیک تبدیل انرژی
سال دهم شماره 1 (پیاپی 35، بهار 1402)

A novel scramjet multi-stage open cooling cycle for electricity and hydrogen co-production is proposed in which the fuel of scramjet is used as coolant of cooling cycle. Thermodynamic and exergetic examination of the advanced system have been conducted to appraise the system’s performance, electricity and hydrogen productions and multi-expansion effects. For the fuel mass flow rate of 0.4 kg/s, the cooling capacity of the new proposed cycle is computed 9.16 MW, the net electricity output is calculated about 3.38 MW and the hydrogen production is attained 42.16 kg/h. On the other hand, the exergetic results have proved the fact that PEM electrolyzer has the highest exergy destruction ratio by 44% among different components of the cycle. Moreover, the results of exergy analysis exhibited that employing the multi-expansion process concept outstandingly decline the overall exergy destruction of the system. In this case, the energy and exergy efficiencies of the overall set-up are acquired by 13.01% and 22.12%, correspondingly

Today, many countries are trying to reduce their dependence on fossil fuels and acquire the energy they need through renewable energy such as wind energy. On the other hand, the design and analysis of wind turbines is suitable for more energy one of the challenges of engineers. Therefore, in this study, momentum models, which is one of the basic methods in the aerodynamics modeling of the vertical axis wind turbine, are examined. These methods are based on the theory of the momentum (actuator disc) and are widely used to evaluate the performance of vertical axis wind turbines. Also it has been attempted to collect basic fair models for designing and analyzing the performance of these turbines. The following are the three models of the stream tubes: the SST model, the MST model, and the dual actuator MST or the same DMST. Each of these models has the advantages and disadvantages that are fully discussed in this research.

In this research, parameter estimation and fault detection in hydraulic pump which is one of the most common systems used in sensitive industries such as aerospace and it has nonlinear behavior is investigated. The detection criterion is the residual signal calculated from the difference between the system output and an unknown input parameter. The reason for using the nonlinear observer is the timely detection of faults and its resistance to model disturbances and uncertainties. In this research, the leakage in the pump and the change of swashplate angle of the hydraulic pump are considered as faults and they could be detected by a nonlinear observer in time. Finally, it is proved by Matlab simulation software that the proposed method is able to estimate the system states well and reveal the faults.

The present study was conducted to optimally select equipment for a grid-connected photovoltaic solar power station using the method of analytical hierarchy process (AHP) and the Expert Choice software. AHP is one of the most widely used multi-criteria decision-making tools. Criteria and sub-criteria such as efficiency, price, number of years of warranty, and amount of equipment were considered. For selection of optimal equipment using the AHP method, realized in Expert Choice, pairwise comparison is made between the sets for weighting once the hierarchical levels, including the goal, criteria, sub-criteria, and alternatives (intended equipment), are specified. As the sets are weighted, the compatibility of judgments is analyzed, which must be less than 0.1. The research addressed the equipment available over the market in Iran. Given the measures considered here, 500W Mono Trina Solar was selected as the best panel, and 25KW Growatt MID KTL3-X was the best inverter. The other alternatives were assigned the next priorities based on the corresponding weights. Moreover, sensitivity analysis was made on the main criteria, and the effect of parameter weight on the alternatives was assessed.

Friction and wear are ubiquitous, from nano-electro-mechanical systems in biomedicine to large-scale integrated electric propulsion in aircraft carriers. Applications of nanomaterials as lubricating oil additives have achieved great advances, which are of great significance to control friction and wear. This review focuses on the applications of nanomaterials in lubricating oil and comprehensively compares their tribological characteristics as lubricating oil additives. Finally, suggestions for future research on nanomaterials as lubricating oil additives are proposed. Hence, this review will promote a better fundamental understanding of nanomaterials for lubricating oil application and help to achieve the superior design of nanoadditives with outstanding tribological performances.

In this study, at the first, the wind capacity of the city of Zahedan was evaluated, and then examined the performance of a vertical axis wind turbine. A V-rotor is obtained by angering the turbine blade to the axis. Therefore, the free wind is deflected by colliding with its angled blades and part of it vertically going out along the turbine axis. This causes the turbine rotation, in addition to producing power, have a flow called ventilation flow. This ventilation flow can be used in warm climate areas so that in addition to generating energy, the ventilation of the site can be performed. The semi-analytical method was used in the 3D modeling for the parametric analysis of the turbine. The results of this study show that the blade angle was directly related to the amount of ventilation flow, and at the angle of 10 degrees and the turbine's work point of about 10,000 m3/hr, the ventilation flow is going out from the bottom of the turbine. This occurs while the turbine's power decreases, but its efficiency at this angle has the highest amount.