صمد جعفرمدار

The intake manifold is a part of the air intake system to the engine, which plays an important role in improving performance such as high torque and low fuel consumption, as well as keeping emissions low. In this paper, by changing the pattern of the air path, its role in engine breathing has been investigated numerically. For this purpose, first, the design of the manifolds was modeled in 3D in SolidWorks software. Also, two manifolds with different geometries were simulated as a 1D-3D couple in GT-SUITE and Ansys Fluent software. Air base fluid was used in this analysis. Using the 3D printer method, the designed manifold was produced, and then practically tested. The obtained results showed that the average speed in the optimized manifold is higher than the existing manifold, which increases the mass flow rate and volume flow rate of the output flow. Also, the amount of intake air for the four ports in the designed manifold has found a more uniform distribution. Performance tests on the engine confirm the performance improvement in terms of increased power with the same fuel and reduced emissions with the new manifold.

Considering the high importance and necessity of replacing fossil fuels with renewable and environmentally friendly fuel sources, for many years researchers have been working on hydrogen production methods as one of the cleanest and most available alternative fuels. have focused their research. One of these studied methods is hydrogen production using water and aluminum. In the current research, thermodynamic analysis is done on this method and the Liebig condenser is the production process of thermodynamic analysis. The efficiency of the condenser and the whole system is calculated. In the next step, system failure factors are identified based on technical literature and experts' opinions, and using one of the multi-criteria decision making methods called the best-worst method, the identified factors are weighted and ranked, and the impact The most important index on system performance is studied and solutions to increase system efficiency are provided.

In the present study, a novel tri-generation system is proposed. The system produces heat, electric power, and cooling water using concentrated solar cells alongside thermoelectric coolers. The simulation of the system is performed analytically. A zerodimensional model for thermoelectric cooler is applied and the thermal resistance network model is used for a more accurate simulation of the cooling system of the concentrated solar cells. The results indicate that the system can deliver 270 kW electrical power and 2 kg/s of cold water flow in 10℃ and 10 kg/s of hot water flow in 50℃ using 1000× CPV panels with an overall surface area of about 2 m2 which are divided into 1×1 cm pieces. The parametric study conducted on the system for different hours of the day shows that solar radiation has a minimal effect on the output cold water temperature, but it strongly affects the generated power.

The use of thermoelectric generators has a special place in recovering the waste heat of combustion gases. In the proposed model, a thermodynamic analysis with the effect of the thermoelectric generator module area on the performance characteristics of the device was studied. To develop the model, the properties of the thermoelectric generator were assumed to be temperature dependent. The convective heat transfer of water in the cold channel was also considered as variable. The effects of water flow regime and the module area were investigated both in the longitudinal direction and for five different values of the module rows on the functional characteristics of the device. The results showed that increasing the number of module rows and module area decreased the power and efficiency of energy and exergy and increased the rate of exergy destruction. The module area is also optimized in two different cases. One was done to achieve the maximum net power and the second to achieve the maximum ratio of maximum net power to the area module. The optimal area in the first and second cases were 0.4641m2 and 0.2207m2 , respectively.

The current study reviews the exergo-economic analysis of a new system for producing power, heat, and distilled water. This proposed system includes a gas turbine (GT) which its waste heat first was recovered by a heat recovery steam generator (HRSG) for producing saturated water vapor and then recycled by an organic Rankine cycle (ORC) for generating more power. Also, this system includes a geothermal energy resource for reheating organic fluid because of power and efficiency increase and a reverse osmosis (RO) desalination unit on the production of freshwater. Feed-water temperature is increased in the condenser via decreasing its mass flow rate. As a result, the unit cost of produced freshwater decreases by 32.24%. The exergo-economic factor of the system is 12.14%, suggesting that exergy destruction accounts for a high proportion of costs. GT/HRSG have the highest share in terms of the capital cost (86.10%). Finally, the effects of the pinch temperature difference in the HRSG and re-heating pressure on the unit cost of the power generated in the ORC, produced water vapor, distilled water, and the overall cost rate were investigated.

The use of liquid metal magnetic hydrodynamic energy units, despite reducing maintenance costs and improving reliability, requires a high-temperature source, which must be supplied by fossil fuels. The present study aims to cover this shortage by proposing a new design for liquid metal magnetic hydrodynamic power and desalination cogeneration plant by applying concentrating solar power. The results show that 73.2 kW and 21.06 m3/day power and freshwater can be produced by the proposed cogeneration plant, respectively. The energy utilization factor  and total exergy efficiency are 97.45 and 26.34%. The results also indicate that the receiver accounts for the highest exergy destruction, followed by the heliostat with 270.4 kW and 240.9 kW, respectively. Increasing the efficiency of the humidifier/dehumidifier or reducing the mass flow rate of the second magnetic hydrodynamic loop improves the energetic and exergetic performances of the system. Besides, the receiver and solar tower have the highest cost of investment and maintenance, and the total unit cost of the system is 103.4 $/GJ.

In piston engines, as the engine speed increases, the combustion cycle time decreases. Reducing the engine combustion cycle time, the opportunity for complete fuel combustion is reduced. As a result, in order to complete the fuel combustion, at high engine speeds, the spark plug must ignite sooner. Now that the natural gas flame is slower than gasoline, this problem is becoming more noticeable. As a result, the spark ignition timing should be increased further in CNG fuel mode than in the case of gasoline combustion. This leads to an increase in negative work during the compression phase, resulting in reduced cycle efficiency. Researchers have suggested adding hydrogen to improve natural gas combustion (HCNG). By adding hydrogen, the flammability properties of natural gas are improved. In this study, using Hydrogen generator, hydrogen and oxygen (HHO) gas is produced and consumed water by electrolysis method. The gas (HHO) produced together with the gas (CNG) is combined with the air entering the engine. Then the effect of gas (HHO-CNG) on the parameters of efficiency, power and pollution has been investigated. The results show that the thermal efficiency increases with the addition of HHO. Under these conditions, CO and UHC levels have decreased. This reduces contamination and increases efficiency due to reduced need for spark plug advance and complete fuel combustion.

In the present study, natural convection of Al2O3–water nanofluid and nano-particles local distribution inside trapezium enclosure has been investigated using non-homogenous two-phase Buongiorno’s model. The effect of the variation of trapezium enclosure inclantion angle on heat transfere, mass and momentum has been investigated. The governing equations of the problem are momentum, energy and volume fraction of nanoparticles that are solved using the finite volume method and the SIMPLE algorithm. Diffusion and convective terms are descritized using a second-order central difference and upwind schemes. The left and right walls of cavity are kept at constant temperatures Th and Tc, respectively, while the other walls are thermally insulated. Using the finite volume method and the SIMPLE algorithm, the governing equations have been discretized. Simulations have been carried out for different inclination angle( ), Rayleigh number(102≤Ra≤104) as well as particle average volume fraction (φ) ranging from 0.01 to 0.04. Results show that at low Rayleigh number for a specific particle volume fraction, with increasing the inclination angle from zero to 45 degree, the average Nusselt number (NuAve)and heat transfer decreases 81%. On the other hand, optimum results were obtained for the inclination angle of 30 degree. The Nuselt enhancement percent was obtained 5.5 compared to the square enclosure and 6.8 compared to inclination angle of 45 degrees. Results also showed a uniform distribution for nanoparticles in high Rayleigh numbers and in enclosures with different inclination angle.

The goal of the present study, has been to investigate one of methods for increasing the double absorption heat transformer’s (DAHT’s) productivity. For this propose, first, due to the special importance of the solution flow path shape on AHT’s operation, five novel schemes were proposed for DAHTs and then, their performance was compared numerically to the most efficient type of DAHTs as basic cycle in this research, through a parametric study. The operation of cycles has been studied from the energy coefficient of performance, exergy coefficient of performance and produced vapor amount, point of view. The effect of adding third heat exchanger to the cycles, is at least a minimum increment of vapor amount equal to 10.49% for basic DAHT, 8.6% for first scheme and 10.33% for second scheme. According to the optimization results, the third scheme in the higher and the fifth scheme in the middle range of absorber temperatures have the ability to produce the most water vapor amount, among all the schemes.

In the present work, in order to improve performance characteristics such as power output and reduce fuel consumption in spark ignition engines and engines used in the aerospace industry, combined gasoline fuels with dimethyl ether and iron oxide nano catalysts that can be synthesized at lower prices than other catalysts , Has been studied in a gasoline spark ignition engine. In order to achieve the steady state in the experimental stages, the temperature of the water and engine oil before each test of the EF7 spark ignition engine at engine speed of 2800 rpm is about 10 to 15 minutes to reach the various parts of the engine. The tests are carried out at full load conditions and engine speed rpm 2800 and between torques 0 to N.m 100. The output power and fuel consumption of the engine, with the combination of gasoline with 10% of the dimethyl ether, increased by 22.5% and 28.28% respectively, and in the case of gasoline in combination with 10% of dimethyl ethyl and 10ppm of iron oxide nano additive, lead to output power 19.44% increased and fuel consumption 19.5% reduced. in the case of gasoline in combination with 10% of dimethyl ether and 20ppm nano additive of iron oxide lead to output power 13.93% increased and fuel consumption 11.08% reduced, compared to the base fuel gasoline. emissions have also been reduced by combined fuel with iron oxide nano catalysts.

In the present study, exergo-economic analysis of a combined solid oxide fuel cell (SOFC) with a gas turbine, a generator-absorber heat exchanger (GAX) and heating process heat exchanger for heating, cooling and power production as a tri-generation system is conducted. Also, an external steam reformer is applied to convert dimethyl ether as oxygenated fuel to hydrogen for the electrochemical process of the SOFC. The influence of the primary design parameters (fuel utilization factor and anode inlet temperature) on several variables (energy and exergy efficiencies, exergy destruction and unit costs of the power) are examined. Results show that energy efficiency of proposed system is 38% higher than standalone SOFC. It was found that the maximum exergy destructions occurred in afterburner, SOFC and recuperator. An increase in anode inlet temperature leads to reduction of exergy destruction in afterburner and fuelcell, while it has reverse effect on exergy destruction rate in recuperator. Unit cost of power is equal to 23.51 $⁄GJ at a specific condition and decreases with an increase in fuel utilization factor or increasing of anode inlet temperature. Increasing of utilization factor will increase all exergy efficiencies by 12%. The effect of an increase in anode inlet temperature on exergy efficiencies is positive but compared with the other parameter is lower and will increase them by 8%.

A new configuration base on Sabalan geothermal wells is proposed to utilize two wells with different thermodynamic properties in Sabalan region in Iran and generate more power as well as supply of natural gas from Liquefied Natural Gas (LNG). A Kalina cycle and Transcritical CO2 Rankine cycle are using sabalan geothermal wells as a heat source and LNG as a thermal heat sink. A comprehensive parametric study is investigated to understand the characteristics of the system. The effects of the separator 1&2 pressures, pinch point temperature difference in the evaporators, the higher pressure of the Kalina cycle, the ratio of the Transcritical higher pressure to the critical pressure and pressure of LNG pump are studied on the power generation and thermal and exergy efficiencies. The results show that the thermal and exergy efficiencies can be increased by increasing separator 1&2 pressures and LNG pump. Also decreasing the higher pressure of the Kalina cycle and pinch point temperature of evaporators lead to increasing the net output power, thermal and exergy efficiencies. Additionally, exergy analysis results showed that the highest exergy destruction rate belongs to the heat exchanger 1&2. Optimization of the proposed cycle is performed by using genetic algorithm method, and it is observed in the optimal condition that the net output power, thermal efficiency, and exergy efficiency can be obtained as 30610 kW, 29.16%, and 56.92%, respectively. The results of this study indicate that the net output power and thermal efficiency is better performance compared to the previous studies.

Using high-performance thermodynamic cycles to generate power from existing heat sources is an effective strategy for sustainable energy development. In this study, a new integrated cycle (triple flash and single flash combined cycle with Organic Rankine cycle) based on different real temperatures and pressures in Sabalan geothermal power plant is proposed and analyzed from thermodynamic and exergy viewpoint. A comprehensive parametric study is performed by EES software and then, the proposed cycle is optimized for four considered working fluids relative to the flash chambers’ pressure (or valve 1, 2 and 3 pressures), the evaporator temperature, and the pinch point temperature difference of evaporator. The results show that isobutane is the most suitable fluid for the Rankine cycle. The power generation, thermal and exergy efficiency, in this case for optimum condition, was calculated to be 23073 kW, 19/73%, and 75.67%, respectively. In optimum condition and compared to other studies which has similar wellhead for Sabalan geothermal power plant, the proposed cycle had better performance from energy and exergy viewpoints.

In this article, a new power, cooling and heating trigeneration system consisting of a hydrogen-fed SOFC (solid oxide fuel cell) - GT (gas turbine ), a HRSG, a GAX absorption refrigeration cycle and a HR has been studied from a parametric and optimization perspective. In contrast with most of the previous investigations, in which the HRSG is located at the downstream of GAX, in the present research, in order to control the wasted heat, HRSG is located at upstream of GAX. The electrochemical analysis is complete for the fuel cell and the cell temperature is computed for all the working conditions of the cell. Then, the parametric study of the hybrid system, the influences of current density, fuel utilization factor, compressor pressure ratio and air utilization factor on the performance of the system are investigated. The optimization of the system is performed in the method of the genetic algorithm to determine the optimal functional points. After optimization and exergoeconomic analysis, minimum SUCP, the exergy destruction cost rate and exergoeconomic factor for the overall system is equal to 277.2 $/GJ, 40.8 $/h and 27.8%, respectively. Therefore, the increase in the components' capital costs can improve the exergoeconomic performance of the system.

In the present research, the performance of a single-cylinder engine with a pre-chamber and natural gas fuel designed in Urmia University has been investigated and the effect of Exhaust Gas Recirculation (EGR) on engine performance has been analyzed. The results indicate that the simultaneous use of the pre-chamber and the EGR reduces significantly nitrogen oxides emission. Also, the amount of unburned hydrocarbons (HC) decreases in the low EGR, but the amount of HC increases significantly with higher EGR. EGR increases the carbon monoxide (CO) emission but does not have a significant effect on carbon dioxide (CO2) emission. Simultaneous use of EGR and pre-chamber can reduce the amount of emission while it can maintain the engine braking. The engine power and the indicated mean effective pressures (IMEP) which are the main indicators of the engine's performance, decrease by 3 to 4 percent for every 5 percent of the EGR. The results show that the EGR reduces the velocity of the jet flames out of the pre-chamber which ultimately reduces the advance of the flame front. Analysis of the results of the experimental test and the simulated model shows that an ideal range for EGR in an engine with a pre-chamber can be defined in which the emission is minimal and the engine power is maintained. In the engine used in this research, the exhaust gas reaction is in the ideal 10% range.

In Iran, Sabalan geothermal power plant has been utilized with two wells having different and mass flow rates and thermal properties. In this study, in order to achieve the maximum power, four new configures; a single flash-binary, a double flash (I)–binary, a double flash (II)–binary and a triple flash-binary cycles were examined. These four configurations were initially investigated considering the effective parameters of energy and exergy analysis, and then optimization was performed using three working fluids. The results show that in the optimum state, the double flash (II)–binary using isobutane shows better results compared to the other three configurations. Furthermore, for the optimum case, the net power of 23084 kW, the thermal efficiency of 19.74%, the exergy efficiency of 75.7%, and the exergy destruction rate of 6250 kW were obtained which show an improvement in terms of energy and exergy for the Sabalan geothermal power plant compared to the previous studies.

In northwestern Iran, two wells with different temperature and pressure conditions have been exploited in Sabalan region. According to the thermodynamic properties of wells, the combined cycle (flash combined cycle with transcritical CO2 and Kalina 11) is proposed for Sabalan geothermal. In the Kalina 11 and transcritical CO2 heat exchangers, in which the fluid temperature is rising, there is a different temperature variation gradient, therefore, a new method is proposed for the determination of pinch point and other thermodynamic properties. The effects of the Kalina high pressure, amoina concentration, transcritical CO2 cycle pressure ratio, pinch points temperature difference and separators’ pressure on the thermal and exergy efficiencies of the proposed combined cycle were studied, Finally the proposed combined cycle was optimized thermodynamically using the EES (Engineering Equation Solver) software. Based on identical operation conditions, the net power of the combined cycle is 20046 kW, the thermal efficiency is 17.15%, the rate of exergy destructions is 8259 kW and the exergy efficiency is 65.74%. It was found that the net power output, the thermal and exergy efficiencies of combined cycle are about 17.55%, 17.55% and 18.35% higher than the previously proposed system.

In this article, a new power, cooling and heating cogeneration system consisting of a solid oxide fuel cell (SOFC) - gas turbine (GT), a heat recovery steam generator (HRSG), Generator-Absorber-heat eXchange (GAX) absorption refrigeration cycle and a heat exchanger for heat recovery (HR) has been studied from a thermodynamic and economic perspective. The modeling of this cycle was done by solving the electrochemical, thermodynamic and exergoeconomic equations for fuel cell and system components, simultaneously. The results showed that the exergy of our proposed combined cycle is 14.9% more and the irreversibility rate of this cycle is 10.6% less than that of the combined SOFC-GT-GAX systems in the same conditions. Also, the fuel cell and the afterburner have the highest rate of exergy destruction among other components due to irreversibility. Exergoeconomic analysis showed that the sum of uint cost of products (SUCP), the exergoeconomic factor, the capital cost rate and the exergy destruction cost rate for the overall system is equal to 331.1 $/GJ, 29.3%, 10.47 $/h and 25.32 $/h, respectively. Parametric studies showed that increasing the current density will increase the net electrical power, heating capacity of HRSG and HR heat exchanger, cooling capacity and total irreversibility. Also, with increasing of the current density, both the exergy efficiency and SUCP decrease.

In this paper, shell-side stream flow distribution on the shell-side fluid flow of shell-tube heat exchanger by baffle space and baffle cut variation computationally was conducted. Flow distribution plays an important role to obtaining high performance in the effective operation of a shell-tube heat exchanger. Uniform flow distribution is critical to obtaining high performance and without tube vibration in shell-tube heat exchanger devices. Also Stream flow rate is a very useful to understand the heat transfer and pressure drop along a shell-tube heat exchanger with the flow distribution. So the shell-side designs of a shell-tube heat exchanger, in particular the baffle spacing and baffle cut dependencies of the stream flow rate are investigated. In the present article a novel technique base on the proposed method presented to measure the flow rates in different baffle sections. The proposed analysis method used hydraulic network principals for evaluation flow velocity distribution on a shell-tube heat exchanger has been developed. According to obtained results baffle space and baffle cut configuration significantly affect the flow field distribution. window-section flow stream have higher flow rate in the shell-side.

The use of new energies, including geothermal energy, is rapidly devoloping in the world. In Iran, the Sabalan area has a great potential for generating energy from geothermal energy sources. In this paper, a new power generation combined cycle (flash combined cycle with supercritical carbon dioxide and organic Rankine cycle) is proposed with respect to two wells with different temperatures and pressures for Sabalan geothermal sources. For the organic Rankine cycle, four fluids are considered appropriately and then proposed combination cycle is investigated by energy and exergy analysis. In this study, a new method proposed for the determination of Pinch point for carbon dioxide heat exchangers. In the end the proposed cycle has been optimized relative to seprators pressure, the second evaporator temperature and the carbon dioxide cycle pressure ratio. The results show that the n-butane agent has been selected as the most suitable fluid for the Rankine cycle. For the optimal condition, the net power of the proposed cycle is 19934 kW, the cycle efficiency will be 17.05% and the exergy efficiency will be65.38 %.The results of exergy analysis show that the low pressure turbine in geothermal have the highest value of exergy destruction. The results show that net power output, energy and exergy efficiencies of the proposed cycle in this paper is 15.29 %, 17.06% and 18.35% higher than the corresponding values obtained for the previously proposed system.

Utilization of natural gas as a clean fuel in internal combustion engines, has potential to reduce pollutants compared to other fuels. New mixture preparation technologies and optimal combustion management has led to a reduction in the pollutants of natural gas engines and efficiency increase. Study of the research works on natural gas engines shows that use of lean combustion strategies has important role in reducing pollutants and improving efficiency. In this study, lean combustion of natural gas with pre-chambered spark plug is reviewed. Experimental study showed that in many engine operating conditions, the combustion stability range was increased and emissions were reduced. Pre-chambered plug ignites the mixture with more speed and turbulence and has more energy to maintain combustion stability. In the experimental study, performance tests were performed on stoichiometric and lean mixture at different loads. For numerical simulation quasi-dimensional model of Gt-power software and 3D simulation of Fire software are used. For validation of analytical and simulation modeling, results of empirical combustion pressure are used

Vortex tube or Ranque–Hilsch vortex tube is a mechanical device with a simple geometry and without any intricacy in its components, which can produce two colder and hotter streams from compressible inlet air. In this investigation, computational fluid dynamics (CFD) technique is used to study of key design parameter influence, i.e. inlet pressure on the performance of vortex tubes and energy separation phenomenon. The novelty of the present paper is the special focus on the Mach number inside vortex chamber and its changes due to the inlet pressure effect which has not been investigated in other papers yet. The governing equations have been solved by FLUENT code in 3D compressible and turbulent model using standard k-ε turbulence model. In this study on the basis of obtained results by the CFD study, different inlet pressures of vortex tube are studied. Finally in order to attain the more temperature separation in the vortex tube system, some suggestions and results is presented. This article believes that every vortex tube has an optimum pressure which is commercially optimized in heating and cooling processes. This optimum pressure was found to be 4.8 bar in the present research. The present obtained software results indicate that for cooling purpose, the cold mass fraction of about 0.3 will be recommended for higher cold temperature difference and for heating purposes in throughput of the cold mass ratio of about 0.8 is used. The obtained CFD results are validated by available experimental results. Also the inlet pressure increment reveals the increase of entropy generation and irregularity in the system.

Environmental pollution and energy constraints have made engineers research a new method of ignition in the internal combustion engines. Also, the automotive industries are searching to replace SI and CI engines due to the strict regulations of international organizations actives in the eld of environment. (HCCI) is a suitable method for combustion in SI and CI engines. The HCCI engine uses a premixed air/fuel mixture that is pressed with high compression ratio. In the research, a CFD model has been used for the analysis of HCCI engine. In order to validate the model, we used the experimental results obtained from Dutez engines with Methane fuel and a secondary fuel injection diesel in 270oCAD position. Investigation showed that concordance between the model and experimental results is acceptable. Maximum cylinder pressure decreases with the increase of EGR. With an increase in EGR percentage, the rate of carbon black increases which it results from the incomplete combustion. Therefore, performance of EGR is acceptable within a certain range. Also, an increase of EGR reduces cylinder temperatures. Incomplete combustion causes a part of the air/fuel mixtures to leave the cylinder without participating in the combustion process. As a result, those parts of the air/fuel mixtures leave the cylinder without producing thermal energy. Increase of EGR rate reduces the amount of heat release due to incomplete combustion, but heat release increases even despite non-combustion. This performance is due to the increase of temperature which, in turn, causes the increase of cylinder density. As a result, heat release is produced even despite non-combustion. It is noteworthy that maximum heat releases occur under non-EGR condition. Change in the heat release rate regarding dierent EGR rates shows that the combustion occurs in dierent positions. The increase of EGR greatly reduces NOX emissions. So, EGR system can provide adequate eect on reducing NOX emissions.