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Controlling combustion has been always a matter of interest to be exploited in combustion systems such as internal combustion engines. Experimentalists found that magnetic field has favorable effects on this phenomenon, applied either directly to the flame or the fuel nozzle. In the current work, the effect of magnetic field on the fuel nozzle of hydrogen-nitrogen mixture (30% hydrogen and 70% nitrogen by volume fraction) is investigated numerically to study the non-premixed flame shape, maximum temperature, maximum velocity, heat of reaction, and its emission including unburnt hydrogen. Magnetic field was applied on three sections of fuel line with various magnitudes. Magnetic field generates Lorentz force which brakes the fuel flow in the nozzle generating a converging-diverging shape resulting in the velocity increase in the center of the nozzle. It was found that the flame length decreased as the magnetic field increased when magnetic field applied to the tip-section of the nozzle, there was no change for the mid and initial sections though. The maximum flame temperature decreased marginally while the heat of reaction remained roughly unchanged. However, the maximum temperature was decreased due to the better heat transfer. Further, unburned hydrogen and OH decreased when the magnetic field applied to the nozzle exit. The results show that magnetic field application to the nozzle exit leads to a better mixing, and reduction in fuel consumption which is interpreted as more complete combustion.

There has been huge attention has been given to renewable energy resources including biomass, to meet the sustainable energy production plans. As one of the first systematic studies, biomass gasification integrated internal reforming solid oxide fuel cell (SOFC) plant is designed and fed by municipal solid waste (MSW) using four different gasification agents including air (case 1), oxygen-enriched air (case 2), oxygen (case 3) and steam (case 4). Tubular SOFC in the atmospheric pressure is considered in a combined heat and power (CHP) system here. The four cases above are simulated, assessed and compared through energy, exergy, environmental and exergoeconomic analyses to identify the best case scenario. Thereby, the influence of varying several key parameters on the performance of the cases are studied. It is found that, oxygen blown plant (case 3) has the exergy efficiency of 43.6% after optimization which is 0.64%, 10.88% and 19.33% higher than cases 4, 2 and 1, respectively. The total exergy unit cost of the products for oxygen blown case is 3.02 cent/kWh, makes it cost efficient case in comparison to other cases. Moreover, it is observed that the exergy destruction rate of gasification reactor as a main irreversible component decreases while moving from case 1 to 4. Besides, case 3 is the most environmentally-friendly option due to lower emission damage cost. Current contribution clearly exhibits the superiority of alternative gasification agents over conventional one.

Since the 1960s, the idea of using supercritical carbon dioxide (s-CO2) as the working fluid in a Brayton power cycle has been entertained (Angelino, 1968). But due to technical limitations of the time, the idea did not progress forward much. Presently, due to the availability of more know-how, better technological platform, and advanced analysis tools, many believe it is time to revisit the idea of using s-CO2 as the working fluid for power generation. Among various working fluids, s-CO2 has several significant advantages over other fluids. Primarily, the attractive qualities of s-CO2 are high efficiency, much smaller turbomachinery size and plant footprint (and therefore lower capital cost), and the potential for full carbon capture. However, the realization of these benefits will depend on overcoming several technical, engineering, and materials science challenges. Even though theoretically, the concept is highly attractive and promising, there are yet major hurdles to be passed, namely, the designing, developing, and testing a reasonable size (10 MWe or higher) prototype of a s-CO2 Brayton-cycle-based power gas turbine. This paper reviews the s-CO2 Brayton cycle technologies for power generation and critically assesses the recent challenges and development status. Further, a two-dimensional in-house code was utilized to design an impeller for an s-CO2 simple recuperated Brayton cycle, generating 10-MWe power. The results were validated first with Eckardt’s design which is often referred to as a benchmark due to the most extensive measurements he performed on centrifugal compressors. Then, a centrifugal compressor was designed by the present authors for a simple recuperated cycle, and the results were reported in detail. The results show that the designed compressor has a wide operation range, making it a viable option to be employed for the commercialization purpose of a 10-MWe s-CO2 Brayton cycle.

Fuel cells offer one of the most eco-friendly and efficient ways of energy production. In this study a thermodynamic and exergoeconomic assessment of a proton exchange membrane fuel cell (PEMFC) system at steady-state operation condition are carried out. Thereafter, the feasibility of integrating a proton exchange membrane Electrolyzer (PEME) to supply required fuel for a PEMFC, operating in the same outlet power range is investigated. The results demonstrate that increasing the current density rises the following parameters in the system: the power and power density rates of the PEMFC and PEME, the exergy destruction rate of each component, the hydrogen production and consumption rates in the cycles, the PEME output voltage, cost rate of power generation and the power cost of the PEMFC. By increasing the PEMFC output voltage, the energy and exergy efficiencies reduce. Moreover, rising the outlet temperature of the PEMFC increases the power and power density rates of the PEMFC and also the energy and exergy efficiencies of the system. While increasing the outlet and operating temperature of the PEME increases the power consumption rate and reduces the energy and exergy efficiencies. The highest energy efficiency of the PEMFC is 36.7% and corresponding maximum exergy efficiency is found 54%, while the lowest values are found 31% and 45.3%, respectively. The cost rate of the power generation by PEMFC is varied between 7.96 × 10−4 and 1.33 × 10−3 $/s and the corresponding rate of the exergy unit cost range is 115.6–132.2 $/GJ.

A comparative analysis is performed for three different layouts of SOFC-GT hybrid systems with internal reformer from the viewpoints of energy, exergy, environmental and economic. The three considered designs are distinguished by number of SOFC stack, as single SOFC stack is employed in one system, while two SOFC stacks (cell numbers halved) are used for the other designs. For the second system, two stacks are fed by fuel and air in parallel way; however, in the third case, two stacks are fed by fuel in parallel and air serially. A mathematical model is developed in EES software to simulate the performance of the cycles through a parametric study. In addition, exergy destruction rate of components of the plants are achieved to recognize the main sources of ireversibilities. The analyses demonstrated that two-stack SOFC-GT series type is more efficient, leading energy and exergy efficiencies to reach 63.22% and 60.81% correspondingly, which are about 20.3% and 8.89% higher than conventional SOFC-GT and parallel type, respectively. The highest source of exergy destruction amongst all system components belongs to after burner. Furthermore, it is observed that the highest total cost, 24.95 $/h, is attributed to conventional SOFC-GT hybrid system while the least amount corresponds to SOFC-GT series type, 18.5 $/h. The CO2 gas emission obtained for two-stack SOFC-GT hybrid system series type, 313.3 kg/MWh, obtained to be the lowest.

A new cogeneration system is proposed consisting of biomass gasification fed by wood, a solid oxide fuel cell (SOFC) and a Goswami cycle, which is a combination of a Kalina and an absorption refrigeration cycle. The Goswami cycle acts as a bottoming cycle to recover waste heat of the SOFC in order to produce cooling effect along with additional electricity. The combined cooling and power (CCP) system is modeled via Engineering Equation Solver (EES) and assessed in terms of energy (or first law) efficiency and exergy (or second law) efficiency. The effects on the system performance of varying several key parameters are examined via sensitivity assessments. It is found that raising the SOFC current density increases the produced electricity generation and cooling, but reduces the energy and exergy efficiencies of the system. It is also found that, as the SOFC inlet flow temperature and the turbine inlet pressure increase, the electricity generation rate and the energy and exergy efficiencies of the system rise to the optimal values of 481.6 kW, 60.2% and 34.7%, respectively, and then decrease. The exergy analysis also demonstrates that the gasification reactor, the boiler and the second air heat exchanger are the main irreversible components.

A cogeneration system based on a methane-fed solid oxide fuel cell (SOFC) integrated with a Stirling engine is analyzed from the viewpoints of energy and exergy. The effects on the system performance are investigated of varying four key system parameters: current density, SOFC inlet temperature, compression ratio and regenerator effectiveness. The energy efficiency of the combined system is found to be 76.32% which is about 24.61% more than that of a stand-alone SOFC plant under the same conditions. Considering exergy efficiency as the only objective function, it is found that, as the SOFC inlet temperature increases, the exergy efficiency of the cogeneration system rises to an optimal value of 56.44% and then decreases. The second law analysis also shows that the air heat exchanger has the greatest exergy destruction rate of all system components. The cooling water of the engine also can supply the heating needs for a small home.

In this study, methane fed trigeneration systems producing power, cooling and heating by means of combination of SOFC, generator-absorber heat exchanger (GAX) absorption refrigeration and heat recovery systems are proposed. Accentuating on the gas recycle of anode and cathode of the SOFC stack, performance of four different suggested configurations are compared with each other. Thermodynamic model is developed for the proposed systems using the mass, energy and exergy balance equations. To give information about the viability of the systems, economic point of view is also taken into account. Meanwhile, the comparison is performed through parametric studies in which the effects of anode recycle and cathode recycle on the net electrical power, energy and exergy efficiency as well as on the unit product cost of trigeneration systems are investigated. The results show that the total energy efficiency of the trigeneration system with anode gas recycle (Tri-SOFC-AR) is 82.5% which is almost 6% larger than that of the simple base case system proposed (Tri-SOFC). In addition, results revealed that among the proposed systems, the one in which the anode and cathode gas recycle (Tri-SOFC-ACR) is used shows the highest exegetic and economic performance in comparison with the other configurations.

The current study assesses the thermo-economic performance of a H2O[Formula: see text][EMIM][DMP] (1-ethyl-3-methylimidazolium dimethyl phosphate) working fluid-based absorption machine coupled with various solar collectors to cater the cooling load to business building at Gandhinagar city, India. H2O[Formula: see text][EMIM][DMP] could be an alternative to conventional LiBr[Formula: see text]H2O working fluid pair of absorption machines as it can operate without problem of crystallization which is perquisite for the continuous operation of the system. A mathematical model is developed to simulate the proposed system with 10[Formula: see text]kW cooling capacity at 5∘C. The sensitivity assessment is carried out to find the effect of various parameters including heat source temperature on the coefficient of performance (COP) and exergetic efficiency for each collector case. The optimum SCOP of parabolic trough collector (PTC)-based system is 11.43% higher compared to ETC-based system, whereas the ETC-based system is 25.10% economical than the PTC-based system. Furthermore, payback period for ETC-based system is only one month higher than FPC-based system, which altogether exhibits the superiority of ETC-coupled H2O[Formula: see text][EMIM][DMP] absorption refrigeration system over FPC-based system.

Shear-driven cavitation plays an important role in many technological applications, including fuel injectors and power generators. Cavitation affects the performance of components and hence it is desirable to understand and predict its behavior since it can have favorable as well as adverse consequences. Although there have been a vast number of studies, a full understanding or theoretical framework describing its behavior has not yet been achieved. This is in part due to the complexities associated with cavitating flows including, internal flow physics, turbulence, two-phase flow and non-equilibrium thermodynamics. Further, experimental techniques are limited in their ability to visualize the phenomena with sufficient resolution for a detailed analysis. In this work, an unstructured, finite volume, computational fluid dynamic (CFD) code coupled to the Eulerian-Eulerian multi-fluid model is utilized to study cavitation phenomena in a nozzle. The well-reported Winkhlofer nozzle at a range of conditions including ΔP = 20, 40, 60, 70, 75, 80, and 85 bar is modeled using n-dodecane reference fuel properties. Three cavitation sub-models were investigated and the results compared with previous experimental and simulation flow data. The flow turbulence was modeled using Reynolds Averaged Navier Stokes Equation (RANS) and Large Eddy Simulation (LES) models and the results evaluated. A mesh sensitivity analysis was conducted with minimum cell sizes of 13.40, 9.48, 7.55, and 6.13 μm were considered to show grid convergence. Further, a novel erosion model was also integrated to identify the potential vulnerability damage zones with respect to the nozzle flow operating conditions. The results were in good agreement with experimental data from optical nozzles as well as previous simulation results. The models capture the cavitation near the solid boundary region and were able to predict the critical cavitation as well as the chocked flow regions. This was consistent with all the models. The results from the erosion model revealed a direct relationship between surface erosion, in terms of Mean Depth of Penetration Rate (MDPR) and incubation time, to higher pressure drops across the nozzle. These findings can be useful to develop future injector nozzle designs that can better mitigate cavitation induced material damage for improved engine endurance.

A new solar-based, combined cooling, heating, and power system is designed and developed for the school of engineering at Urmia University in Urmia, Iran. The proposed arrangement consists of a solar subsystem with parabolic trough solar collectors, an organic Rankine cycle, two heating processes, and two single-effect absorption chillers. The system is thermodynamically studied for the summer air conditioning requirements, considering genuine energy demand and variable solar radiation in three different operational modes (solar, solar and storage, and storage modes). The influences on the system performance are assessed of varying three main variables including the number of days, organic Rankine cycle pump inlet temperature, and organic Rankine cycle turbine inlet pressure. The results demonstrate that the highest cooling, heating and electrical loads in the summer air conditioning are 896.9 kW, 228.5 kW, and 1500 kW, respectively. The energy load is provided by employing 449–1625 number of PTSCs throughout the year. Furthermore, for summertime the energetic and exergetic analyses reveal that the energy efficiency of the system in the solar mode, solar and storage mode, and storage mode is found to be 98%, 47.3%, and 98%, respectively. Accordingly, the exergy efficiencies were equal to 17%, 8.3%, and 17%.