Optimum Profiles of Endwall Contouring for Enhanced Net Heat Flux Reduction and Aerodynamic Performance

Successfully utilized non-axisymmetric endwalls to enhance turbine efficiencies(aerodynamic and turbine inlet temperatures) by controlling the characteristics of the secondary flow in a blade passage. This is accomplished by steady-state numerical hydrodynamics and deep knowledge of the field of flow. Because of the interaction between mainstream and purge flow contributing supplementary losses in the stage, non-axisymmetric endwalls are highly susceptible to the inception of purge flow exit com...     

Engineering microstructure of LiFe(MoO4)2 as an advanced anode material for rechargeable lithium-ion battery

Graphite is considered as an ideal anode material for lithium-ion battery (LIB) due to its high stability, good conductivity and wide source of availability. However, the low energy density and theoretical capacity of graphite cannot meet the needs of high performance anode materials. To circumvent this issue, alternative materials have been sought for many years now. Herein, we report the synthesis of highly crystalline lithium iron molybdate LiFe(MoO₄)₂ by combustion method and evaluated its performance as an anode material for lithium-ion batteries. Triclinic LiFe(MoO₄)₂ crystals having particle size 2–5 μm with good crystallinity were obtained. The material shows long cycle life and high rate performance than commercial graphite and exhibits first reversible discharge capacity of 931.6 mAh/g at a current density of 100 mA/g which is three times higher than commercial graphite. The high specific capacity together with the outstanding rate and cycle performance makes LiFe(MoO₄)₂ a promising anode material for LIB. A detailed analysis on the crystal structure and electronic properties of LiFe(MoO₄)₂ is presented based on DFT studies to complement the experimental observations.

     

On the facile polyvinyl alcohol assisted sol-gel synthesis of tetragonal zirconia nanopowder with mesoporous structure

A facile template assisted sol-gel method has been used to prepare nanoparticles of tetragonal zirconia (t-ZrO₂) with spherical morphology and porous structure along with mono dispersibility. The medium assisting growth of nanoparticles mainly consisted of ZrOCl₂·8H₂O and NH₄OH as reactants in a 1:2 mixture of Isopropyl alcohol (IPA)-polyvinyl alcohol (PVA) as the dispersing agent. The effect of medium, IPA-PVA mixture on crystallite size and agglomeration was studied and discussed on the basis of XRD and also based on possible surface reactions. More over reacting medium and calcination temperature has vital role in determining the crystallinity and morphology of ZrO₂. Trials based on mode of addition of the reacting medium followed by calcination provides mesoporous, spheroid, monoclinic zirconia (m-ZrO₂) with an average particle size of 15?nm. The sample prepared under optimized conditions (2?wt% PVA-IPA) showed pure tetragonal crystallite phase with an average particle size of 5?nm, surface area of 56?m²?g^?1, and a mesoporous structure after calcination at 600?°C for 5?h. The tetragonal (t-ZrO₂) phase formed were stable and showed spherical morphology up to 600?°C after which the nanostructure was disturbed drastically; the agglomeration leads to structure collapse forming hard conglomerates and finally leads to monoclinic crystalline phase.     

Turbine Passage Secondary Flow Dynamics and Endwall Heat Transfer Under Different Inflow Turbulence

This study presents endwall hydrodynamics and heat transfer in a linear turbine cascade at Re 5×10⁵ at low and high intensities of turbulence. Results are numerically predicted using the standard SST model and Reθ-γ transition model as well as using the high-resolution LES separately. The major secondary flow components, comprising the horseshoe, corner, and passage vortices are recognized and the impact on heat or mass transfer is investigated. The complicated behavior of turbine passage secondary flow generation and establishment are impacted by the perspective of boundary layer attributes and inflow turbulence. The passage vortex concerning the latest big leading-edge vane is generated by the enlargement of the circulation developed at the first instance adjacent to the pressure side becomes powerful and mixes with other vortex systems during its migration towards the suction side. The study conclusions reveal that substantial enhancements are attained on the endwall surface, for the entire spanwise blade extension on the pressure surface, and in the highly 3-D region close to the endwall on the suction surface. The forecasted suction surface thermal exchange depicts great conformity with the measurement values and precisely reproduces the enhanced thermal exchange owing to the development and lateral distribution of the secondary flows along the midspan of the blade passage downstream. The impacts of the different secondary flow structures on the endwall thermal exchange are described in depth.