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Vibro-Acoustic Formulation of Elastically Restrained Shear Deformable Orthotropic Plates Using a Simple Shear Deformation Theory
Get PDFA method is presented for vibro-acoustic analysis of elastically restrained orthotropic shear deformable plates subjected to excitation forces at different locations. The vibration of the shear deformable plate is formulated on the basis of the Ritz method and a simple first-order shear deformation theory in which 4 rather than 5 displacement components are used to simulate the deformation of the plate. The accuracy of the modal characteristics (natural frequency and mode shape) of an orthotropic plate predicted using the proposed method is verified by those obtained using other methods. The vibration responses of the plate are used in the first Rayleigh integral to construct the sound pressure level (SPL) curves of the plate subjected to excitation forces at different locations. The suitability of the present method for sound radiation analysis is validated by comparing the SPL curve obtained using the present method with those obtained using the other methods. The effects of different system parameters on the SPL curve of the plate are studied by means of several numerical examples. It has been shown that excitation location has significant effects on the smoothness of the SPL curve
Humidity Effect on the Simulation Accuracy of Solar Vortex Engine Performance
Get PDFIn this study, a validated computational simulation is presented to investigate the effect of humidity on the performance prediction of the solar vortex engine system. Data from an experimental model are used to validate the CFD simulation. Three humidity cases are considered: dry air, 40% and 80% humid air. An expansion process with heat addition is taking place inside the vortex generator. When the vortex field continues outside the system, a compression process with heat rejection occurs, eventually bringing the air vortex to be thermal and mechanical equilibrium with the surrounding atmosphere. The change in total energy and the heat transfer rate for both processes, inside the vortex generator and outside the vortex generator, increase with increased humidity in the working fluid. The humidity increases the energy required by the system to generate and maintain the air vortex. Compared to the dry air, the pressure drop at the center of the vortex field decreases by (2-5%) and (4-9%) for the 40% and 80% humid air, respectively. Reduced pressure drop decreases the stability of the air vortex when it is in contact with the atmosphere. The intensity of the air vortex is not affected by the increase in humidity
Analysis of the Poly(Butylene Succinate-Co-Lactate)/ Montmorillonite-Kaolinite Nanocomposite in the Formation of Microcapsules
Get PDFA nanocomposite system comprised by a biodegradable polymer, poly(butylene succinate-co-lactate) (PBSL), and a Brazilian nanoclay (VMF1) containing montmorillonite (MMT) and kaolinite (K) is used to prepare microcapsules by solvent diffusion method. The nanocomposite PBSL/MMT-K and the microcapsules were characterized by wide angle X-ray diffractometry (XRD), scanning electron microscopy (SEM), stereomicroscopy, and Fourier transform infrared spectroscopy (FTIR). The overall results show that PBSL/MMT-K presents intercalated nanostructure of montmorillonite and kaolinite, both PBSL and PBSL/MMT-K proved to be very effective as matrix for production of uniform spherical microcapsules, as surveyed by scanning electron microscopy and stereomicroscopy. The spherical microcapsules repared from PBSL/MMT-K nanocomposite presented diameters smaller than 50Ž¼m, and can probably be used as delivery systems
Numerical Study on the Effect of Natural Gas on Aircraft Turbofan Engine Propulsion
Get PDFThe world has been concerned and worried about the depletion of the liquid oil fuel, besides new environmental rules are to be followed to reduce pollution hazards and global warming. The utilization of natural gas (as a near term fuel) and hydrogen (as long-term fuel) are receiving great attention, because they have less pollution effects. Since the aviation has a great deal in environmental pollution effects due to the cruise flight in the upper troposphere (supersonic aircraft) or in the lower stratosphere (subsonic aircraft) where most of the ozone concentrate, which helps in protecting the earth form ultra violet radiation. Therefore, the use of alternate fuel has a great attention in aviation. In the present study, the thrust specific fuel consumption and specific thrust for the aircraft during aircraft flight profile are predicted, when using aviation fuel and natural gas. The P&W JT9D –7R-turbofan jet engine is taken as a base line engine propelling the Boeing 747-200 aircraft as a base line aircraft with four engine nacelles mounted on wings. The model engine fuel-air cycle representation is carried out for design point calculations based on sea level static conditions and variable specific heats along engine components. The predicted engine performance results compared very well with the reported values by the manufacture. Predictions carried out using aviation fuel and natural gas show an increase in the specific thrust by 3% and decrease in the thrust specific fuel consumption by 14% and fuel to air ratio by 11%, when using natural gas
Maximum Power Point Tracking of a Network-Connected Photovoltaic System Based on Gravity Search Algorithm and Fuzzy Logic Controller
Get PDFThis paper presents a novel hybrid approach based on fuzzy logic controller and gravity search algorithm to track the global maximum power point of a network-connected photovoltaic system in partially shaded conditions. One of the most critical issues in this context, which has been neglected in previous studies, is the consideration of speed and accuracy at the same time. Hence, this paper uses a boost converter with a fuzzy logic controller to increase the model\u27s accuracy. Also, the speed of the method is increased by utilizing the gravity search algorithm. Finally, maximum power is subjected to a power network via a three-phase multi-level inverter. Simulation results show the proposed method\u27s performance and accuracy in tracking the PV system\u27s maximum power point with high-speed responses in partial and variable shadow conditions
Theoretical Study Oxygen Reduction Activity of Phosphorus-doped Graphene Nanoribbons
Get PDFPhosphorus-doped graphene is known to exhibit good electrocatalytic activity for oxygen reduction reaction (ORR). While the ORR activity of P-doped graphene nanoribbons (PGNR) is still unclear. Taking the common graphene nanoribbons with the edges of armchair as an example in this study, we research the mechanistic investigation of ORR on the PGNR under acidic electrolytic conditions by density functional theory (DFT). Based on the keen observation of the atomic charge distribution and adsorption energy at different sites, P atom in PGNR is considered to be the strongest adsorption site with oxygen. Detailed ORR mechanistic was deduced by the investigation of reaction heat, reaction barrier for each possible step and molecular dynamics (MD) simulation. Based on our calculations, when the contribution of the intermediate product to the ORR activity is not considered, PGNR does not possess the property as an ORR catalyst due to several high reaction barriers and some endothermic reactions for ORR path
Study on Multiscale Hydrodynamic Step Bearing
Get PDFIn a step bearing, when the surface separation is so low that it is comparable with the thickness of the physical adsorbed layer on the bearing surface, the physical adsorbed layer should have an influence on the bearing performance. The present paper presents a multiscale analysis for this multiscale hydrodynamic bearing by considering the effect of the adsorbed layer but neglecting the interfacial slippage on any interface. The adsorbed layer flow is described by the nanoscale flow equation, and the intermediate continuum fluid flow is simulated based on the Newtonian fluid model. The pressure distribution and carried load of the bearing were derived. Exemplary calculations show that when the surface separation in the bearing outlet zone is below 100nm but no less than 10nm, for a weak fluid-bearing surface interaction both the pressure and carried load of the bearing are just slightly higher than those calculated from the conventional hydrodynamic lubrication theory, for a medium fluid-bearing surface interaction the differences are further enlarged, and for a strong fluid-bearing surface interaction the differences are mostly enlarged. The results show the very significant multiscale effect in this bearing resulting in the pronounced improvement of the load-carrying capacity of the bearing by the medium and strong fluid-bearing surface interactions when the surface separation in the bearing outlet zone is below 100nm
Analysis of a Direct Current Compressor for Solar Cooler
Get PDFRefrigeration systems have higher electricity consumption ratio in overall energy consumption especially in household utilization. On the other hand, these systems have an advantage of being powered by renewable energy sources such as solar or solar-wind hybrid systems because of their lower power demand. Since the efficiency improvement of refrigeration systems is crucial for domestic and industrial systems in the present study, solar energy powered compressor for vapour compression refrigeration systems have been investigated. Compressor is the most important part and often the costliest component of any refrigerant system. There are two different options for powering the compressor such as alternative current (AC) and direct current (DC).For that reason, this study focused on thermal analysis of critical component inside the novel DC compressor. Computational Fluid Dynamics (CFD) analysis has been realized to figure out the heat transfer mechanism inside the compressor components and also thermodynamics efficiency. Temperature distribution in the compressor during the operation was presented and the component of the compressor position re-designed with resulted parameter and discussed affects of the volumetric efficiency.Furthermore, in this study, experimental performance analysis of the novel DC type refrigeration compressor implemented in a 50 l refrigerator to show its cooling performance and compare well known DC compressor in the market. Energy usage reduction and operational improvement potential of the solar powered DC compressor via variable speed operation were investigated. The comparison showed that variable speed operation of the novel DC compressor can be much more efficient than constant speed operation
The Effect of Fuel Emulsion on Fuel Saving in Cement Kilns
Get PDFIn this work, the combustion of heavy oil and its emulsions with water, in the cement kilns, was investigated in experiments on an industrial scale. The performance of the cement rotary kilns, used in Tartous Company for cement and construction materials, was studied when they were employed to be operated with heavy fuel oil (HFO) and with the water phase of emulsified heavy oil containing 8 vol. % water and 92 vol. % heavy fuel oil (HFO). The emulsified water/heavy fuel oil (W/HFO) with 8 vol. % of water content showed no separation and contained the smallest and most homogeneous water-in-HFO (W/HFO) droplets after stability tests. Four rotary kilns have been operated for 4 months with a regular heavy fuel oil HFO and W0.08/HFO0.092. It has been found that the micro-explosion, observed in W0.08/HFO0.092, improved the kiln efficiency and reduced the fuel consumption by 10.31% in the case of normal feeding while the fuel saving increases with decreasing the feeding rate and reaches 12.99 at low feeding rate. The effect of emulsified fuel on the composition of Portland cement clinker that produced in Tartous Company for cement and construction materials using these two types of fuels is investigated. It is found that the influence is practically negligible on the Alite and Ferrite phases of clinker composition while the influence on the other two phases is important
A Review Study on the Modeling and Simulation of Solar Tower Power Plants
Get PDFMuch attention has been paid to concentrating solar power technologies (CSP) in the last two decades. Among the CSP that have been developed so far are the parabolic trough, the parabolic dish, the Fresnel collectors and the solar tower. However, the most widely used of these technologies is the solar tower power plant (STPP). This review aims to summarize the state-of-the-art modeling approaches used to simulate the performances and the reliability of the STPP. The review includes the different analytical and numerical models used in literature to predict the thermal efficiency of these STPP. A general description and comparison of different CSP technologies are first provided. An overview of STPP technology, current status and a presentation of the major components including the heliostat field and the solar receiver are then highlighted. The different research works, developed on the modeling and simulation of the STPP performances and reliability, are also investigated in this review. In summary, this work presents a comprehensive review of the existing numerical and analytical models and could serve as a guideline to develop new models for future trends in solar tower power plants