Instabilities of horizontal magnetoconvection with rotating fluid in a sparsely packed porous media

We studied linear and nonlinear instabilities of horizontal magnetoconvection with rotating fluid in a sparsely packed porous media. We studied the critical Rayleigh number and traced marginal stability curves at different parameters , , , and . We obtained Takens‐Bogdanov and co‐dimension two bifurcation points. The Newell‐Whitehead multiple scheme was employed to derive amplitude equations at Pitchfork and Hopf bifurcation. At the onset of Pitchfork bifurcation we identified Eckhaus and Zigzag instability regions and studied Nusselt number. The system of coupled Landau Ginzburg equations were derived at the onset of Hopf bifurcation and identified secondary instability regions for fixed parameters, steady state mode shifted to standing and traveling waves as increases.     

Hall and ion-slip effects on MHD free convection flow of rotating Jeffrey fluid over an infinite vertical porous surface

An attempt has been made to explore Hall and ion-slip effects on an unsteady magnetohydrodynamic rotating flow of an electrically conducting, viscous, incompressible, and optically thick radiating Jeffrey fluid past an impulsively vertical moving porous plate. Analytical solutions of the governing equations are obtained by Laplace transform technique. The analytical expressions for skin friction, Nusselt number, and Sherwood number are also evaluated. The velocity, temperature, and concentration distributions are displayed graphically in detail. From engineering point of view, the changes in skin friction, Nusselt number, and Sherwood number are observed with the computational results presented in a tabular manner. It is observed that the effects of rotation and Hall current tend to accelerate secondary velocity and decelerate primary velocity throughout the boundary layer region. Thermal and concentration buoyancy forces tend to accelerate both velocity components. Thermal radiation and thermal diffusion tend to enhance fluid temperature throughout the boundary layer region. Rotation and Jeffrey fluid parameters tend to enhance both stress components.     

Environment-friendly fuel Cymbopogon flexuosus: Analysis of fuel properties,performance, and emission parameters of a Direct Injection Compression Ignition research engine

The novelty of this study  discusses on the influence of neat lemongrass oil (LGO) on fuel analysis, performance and emission analysis, naturally aspirated diesel engine. The critical parameters include iodine value, flash point, kinematic viscosity, saponification and cetane numbers, calorific value, Fourier transform infrared spectroscopy (FT-IR), and gas chromatography–mass spectroscopy (GC-MS) studies were investigated. The oxygenated elements, such as naphthalene, caryophyllene, pentadecanoic acid, dihydropyridine, d -limonene are observed using GC-MS analysis. The higher hydrocarbon (HC) chain length indicates a rise in energy density and boiling point with a reduction of volatility. Using FT-IR analysis, C–H stretching vibrations are found at a frequency of 1672 cm⁻¹. The C≐C stretching vibrations at 1740 cm⁻¹ reveals the availability of the alkenes/fingerprint phase. Experiments were conducted at four different volumetric blend ratios of LGO-diesel blends at typical injection parameters under different loading conditions. Brake thermal efficiency (BTE) decreased for all the test combinations of LGO than diesel. BTE is observed as 30.79% at diesel, 30.06% at LGO25, 28.71% at LGO50, 27.77% at LGO75%, and 27.23% at LGO100. The cylinder pressure and heat release rate increased proportionately with the LGO fuel mixture. Carbon monoxide, HC, and smoke emissions are reduced by LGO mixtures than diesel at the full load of the engine. It was noted that greater blends of LGO and diesel resulted in increased nitrogen oxide (NO_x) emissions and engine tribological characteristics. The NO_x is increased by 21.2% at LGO25, 24.3% at LGO50, 26.5% at LGO75 and 30.8% at LGO100 when compared with diesel. Without any chemical processing, Cymbopogon flexuosus oil can be blended directly with diesel fuel.     

Characterization of sodium flow over hexagonal fuel subassemblies

Steady flow of liquid sodium over a bundle of heat generating hexagonal subassemblies has been investigated. The cross flow pressure drop and heat transfer are characterized using the general purpose CFD code STAR-CD. Analysis has been carried out for both laminar and turbulent regimes of interest to liquid metal fast reactors. Turbulence has been modeled using low Reynolds number (Re) k-ε model. The estimated pressure drop and heat transfer coefficients are compared against that of a straight parallel plate channel. It is seen that in the low Reynolds number range, the pressure drop for the hexagonal path is nearly equal to that of the parallel plate channel for the same length. However, in the high Reynolds number range, the pressure drop of the hexagonal path is much higher than that in the parallel plate channel, the ratio being 2 at Re = 2000 while it is 3.6 at Re = 20,000. Two competing factors, viz., (i) jet impingement/flow development effect and (ii) flow separation effect are found to influence the average Nusselt number (Nu). In the laminar regime, the latter effect dominates leading to a decrease of the Nusselt number with an increase in the Reynolds number. However, in the turbulent regime, the former effect dominates leading to an increase in the Nusselt number with Reynolds number. The Nusselt number in the hexagonal path is about twice that of the parallel plate channel due to under development of velocity/temperature profiles and the recirculation associated with the hexagonal path due to the changes in flow direction. Detailed correlations for both the pressure drop and the average Nusselt number have been proposed.     

Impact of cosolvent (glucose) on the stabilization of ovalbumin

Proteins are stabilized by glucose against denaturation due to extremes of pH. This was studied by means of density, ultrasonic velocity, viscosity and surface tension measurements in the ovalbumin (5 mg/ml) dissolved in phosphate buffer (pH 2, 5, 7, 9 and 12). Few thermo-acoustical parameters such as adiabatic compressibility, intermolecular free length, acoustic impedance, the partial apparent specific volume and the partial apparent specific adiabatic compressibility were calculated for the said systems. Obtained results suggest that the stabilization of ovalbumin occurs in the presence of glucose through strengthening of hydrophobic interactions supported by other non-covalent interactions and the steric exclusion effect of the cosolvent molecules.     

Nitrogen‐doped graphene catalysts: High energy wet ball milling synthesis and characterizations of functional groups and particle size variation with time and speed

Nitrogen‐doped graphene (N‐G) catalyst emerges as one of the promising non‐platinum group metal (non‐PGM) catalysts with the advantages of low cost, high oxygen reduction reaction (ORR) activity, stability, and selectivity to replace expensive PGM catalysts in electrochemical systems. In this research, nanoscale high energy wet (NHEW) ball milling is first investigated for the synthesis of N‐G catalysts to make conventional problems such as sintering or localized overheating issues negligible. The successful synthesis of N‐G catalysts with comparable catalytic performance to 10 wt% Pt/C by using this method has been published. This paper focuses on understanding the effect of grinding speed and grinding time on the particle size and chemical state of N‐G catalysts through the physical and chemical characterization. The research result shows that (1) the final particle size, nitrogen doping percentage, and nitrogen bonding composition of synthesized N‐G catalysts are predictable and controllable by adjusting the grinding time, the grinding speed, and other relative experimental parameters; (2) the final particle size of N‐G catalysts could be estimated from the derived relation between the cracking energy density and the particle size of ground material in the NHEW ball milling process with specified experimental parameters; and (3) the chemical composition of N‐G catalysts synthesized by NHEW ball milling is controllable by adjusting the grinding time and grinding speed.     

Additive manufactured bipolar plate for high-efficiency hydrogen production in proton exchange membrane electrolyzer cells

Additive manufacturing (AM) technology is capable of fast and low-cost prototyping from complex 3D digital models. To take advantage of this technology, a stainless steel (SS) plate with parallel flow field served as a combination of a cathode bipolar plate and a current distributor; it was fabricated using selective laser melting (SLM) techniques and investigated in a proton exchange membrane electrolyzer cell (PEMEC) in-situ for the first time. The experimental results show that the PEMEC with an AM SS cathode bipolar plate can achieve an excellent performance for hydrogen production for a voltage of 1.779 V and a current density of 2.0 A/cm². The AM SS cathode bipolar plate was also characterized by SEM and EDS, and the results show a uniform elemental distribution across the plate with very limited oxidization. This research demonstrates that AM method could be a route to aid cost-effective and rapid development of PEMECs.     

Effect of carboxyl graphene nanofluid on automobile radiator performance

Nanofluid is a promising solution for the improvement of the radiator performance. In the current research work, the effect of the nanofluid carboxyl graphene on the performance of a radiator is studied. Carboxyl graphene nanoplatelets are added to 50:50 ethylene glycol–distilled water at three concentrations of 0.02, 0.03, and 0.04 vol%. The liquid flow rate is varied from 3 liters per minute (LPM) to 6 LPM, and the inlet liquid to the radiator has been maintained at constant temperatures of 40 °C and 50 °C. The inlet air Reynolds number is varied between 1200 and 2500. The effects of these on performance parameters such as Nusselt number, effectiveness, and friction factor are investigated. It is observed that addition of carboxyl graphene nanoplatelets increases the Nusselt number and effectiveness of radiator while friction factor is unaltered. The effectiveness of radiator increases by 27.38% and 23.41% for inlet temperatures of 40 °C and 50 °C respectively at 0.02 vol% and 5 LPM flow rate.     

Advance Electronic Load Controller for Micro Hydro Power Plant

Most of the MHP （micro hydro power） plants use ELC （electronic load controller） for speed control. Various types of ELC have been developed so far. A dummy ballast load is connected across each phase of generator terminals and ELC controls the power consumed by the ballast load to result in constant speed operation. The ELC developed so far uses thyristor switches in each phase to control ballast load power. The ELC senses the system frequency and comparing it with reference frequency, it generates a common value of firing angle for all three thyristor pairs of each phase. The performance of such ELC is not perfect for unbalanced consumers load connected in each phase, which overloads the generator. This paper presents an advanced type of ELC which senses frequency as well as consumer＇s load current of each phase and fires the thyristor pairs with different value of firing angles for different phases. This solves the problem of overloading of the generator with unbalanced consumer＇s load. Simutink model is developed to perform transient analysis of the proposed scheme and the prototype of hardware is also fabricated. The simulation results and experimental results are presented.