Numerical investigation & comparison of a tandem-bladed turbocharger centrifugal compressor stage with conventional design

Extensive numerical investigations of the performance and flow structure in an unshrouded tandem-bladed centrifugal compressor are presented in comparison to a conventional compressor. Stage characteristics are explored for various tip clearance levels, axial spacings and circumferential clockings. Conventional impeller was modified to tandem-bladed design with no modifications in backsweep angle, meridional gas passage and camber distributions in order to have a true comparison with conventional design. Performance degradation is observed for both the conventional and tandem designs with increase in tip clearance. Linear-equation models for correlating stage characteristics with tip clearance are proposed. Comparing two designs, it is clearly evident that the conventional design shows better performance at moderate flow rates. However; near choke flow, tandem design gives better results primarily because of the increase in throat area. Surge point flow rate also seems to drop for tandem compressor resulting in increased range of operation.     

Okra (Hibiscus esculentus) seed oil for biodiesel production

Biodiesel was derived from okra (Hibiscus esculentus) seed oil by methanol-induced transesterification using an alkali catalyst. Transesterification of the tested okra seed oil under optimum conditions: 7:1 methanol to oil molar ratio, 1.00% (w/w) NaOCH₃ catalyst, temperature 65 °C and 600 rpm agitation intensity exhibited 96.8% of okra oil methyl esters (OOMEs) yield. The OOMEs/biodiesel produced was analyzed by GC/MS, which showed that it mainly consisted of four fatty acids: linoleic (30.31%), palmitic (30.23%), oleic (29.09%) and stearic (4.93%). A small amount of 2-octyl cyclopropaneoctanoic acid with contribution 1.92% was also established. Fuel properties of OOMEs such as density, kinematic viscosity, cetane number, oxidative stability, lubricity, flash point, cold flow properties, sulfur contents and acid value were comparable with those of ASTM D 6751 and EN 14214, where applicable. It was concluded that okra seed oil is an acceptable feedstock for biodiesel production.     

Aqueous solution of basic fuchsin as food irradiation dosimeter

Dosimetric characterization of aqueous solution of basic fuchsin was studied spectrophotometrically for possible application in the low-dose food irradiation dosimetry. Absorption spectra of unirradiated and irradiated solu- tions were determined and the decrease in absorbance with the dose was noted down. Radiation-induced bleaching of the dye was measured at wavelengths of maximum absorption λmax (540nm) as well as 510nm and 460 nm. At all these wavelengths, the decrease in absorbance of the dosimeter was linear with respect to the absorbed dose from 50 Gy to 600 Gy. The stability of dosimetric solution during post-irradiation storage in the dark at room temperature showed that after initial bleaching during first ten to twenty days, the response was almost stable for about 34 days. The study on the effect of different light and temperature conditions also showed that the response gradually decreased during the storage period of 34 days, which shows that basic fuchsin dye is photosensitive as well as thermally sensitive.     

Application of response surface methodology for optimizing transesterification of Moringa oleifera oil: Biodiesel production

Response surface methodology (RSM), with central composite rotatable design (CCRD), was used to explore optimum conditions for the transesterification of Moringa oleifera oil. Effects of four variables, reaction temperature (25–65 °C), reaction time (20–90 min), methanol/oil molar ratio (3:1–12:1) and catalyst concentration (0.25–1.25 wt.% KOH) were appraised. The quadratic term of methanol/oil molar ratio, catalyst concentration and reaction time while the interaction terms of methanol/oil molar ratio with reaction temperature and catalyst concentration, reaction time with catalyst concentration exhibited significant effects on the yield of Moringa oil methyl esters (MOMEs)/biodiesel, p < 0.0001 and p < 0.05, respectively. Transesterification under the optimum conditions ascertained presently by RSM: 6.4:1 methanol/oil molar ratio, 0.80% catalyst concentration, 55 °C reaction temperature and 71.08 min reaction time offered 94.30% MOMEs yield. The observed and predicted values of MOMEs yield showed a linear relationship. GLC analysis of MOMEs revealed oleic acid methyl ester, with contribution of 73.22%, as the principal component. Other methyl esters detected were of palmitic, stearic, behenic and arachidic acids. Thermal stability of MOMEs produced was evaluated by thermogravimetric curve. The fuel properties such as density, kinematic viscosity, lubricity, oxidative stability, higher heating value, cetane number and cloud point etc., of MOMEs were found to be within the ASTM D6751 and EN 14214 biodiesel standards.     

A Group Theoretic Construction of Large Number of AES-Like Substitution-Boxes

Wireless Personal Communications - Modern block ciphers have been used to design security schemes to fulfil the security requirements in different areas of applications. The substitution boxes,...     

Effects of Molecular Structure on the Physical,Chemical, and Electrical Properties of Ester-Based Transformer Insulating Liquids

This article presents the experimental studies carried out on the environmental friendly polyol ester insulating liquids to investigate the effect of molecular structure on the physical, chemical, and electrical properties. Six different polyol esters that can be produced from the transesterification of various methyl esters with neopentylglycol/trimethylolpropane alcohols were synthesized and compared with those of refined, bleached, and deodorized palm oil (RBDPO) and mineral transformer oil. The finding suggests that the physical properties like fire point, pour point, and viscosity are very much affected by the molecular weight and molecular composition of the polyol esters. The electrical properties are also highly influenced by the molecular structure-related characteristics, such as the polarity, dipole polarization, carbon chain length, and degree of branching. The results confirm the findings of previous studies that the polyol esters and RBDPO have more polarity and dipole polarization compared to mineral oil. The experimental evidence showed that the newly synthesized insulating liquids have favorable thermal and electrical properties, thus suggesting that the insulating liquids have the potential to replace conventional insulating liquids to provide a more sustainable power system in the future.     

Growth of (K0.5Na0.5)NbO3–SrTiO3 lead-free piezoelectric single crystals by the solid state crystal growth method and their characterization

Lead zirconate titanate (PZT) piezoelectric ceramics are commonly used in various applications, e.g. gas igniters, high-voltage generators and microbalances. However, due to increasing health and environmental concerns over their high lead content, lead-free piezoelectric ceramics are being developed. Lead-free piezoelectric single crystals offer superior performance over their polycrystalline counterparts but are difficult to grow by conventional methods. In this paper, (K_0.5Na_0.5)NbO₃–SrTiO₃ (KNN–ST) single crystals are grown for the first time by the solid state crystal growth (SSCG) method. 〈100〉 KTaO₃ single crystal seeds are buried in the center of pellets of pressed KNN-ST powder. The single crystal grows from the seed crystal during sintering at 1100 °C for 20 h. The grown single crystals contain porosity, which is incorporated from the matrix during growth. The effect of SrTiO₃ addition on single crystal growth behavior, chemical composition and structure is evaluated.     

Functional finishing and coloration of textiles with nanomaterials

Global demand for functional textiles is continually increasing for both conventional as well as advanced technical applications. Nanomaterials have the potential to transform the textile industry by imparting multifunctional properties such as physical, chemical and biological self‐cleaning, ultraviolet (UV) protection, wrinkle resistance and coloration to textiles without compromising the inherent characteristics of the substrate. This review highlights some of the major applications of nanomaterials to textile substrates to obtain different functional properties. Possible side effects of the nanomaterials on textiles are also reviewed, along with potential hazards to humans and the environment.     

Synthesis and Optimization of 2-ethylhexyl Ester as Base Oil for Drilling Fluid Formulation

A stable ester was synthesized to overcome the ester hydrolysis problem during the drilling of oil or gas wells using a conventional ester-based drilling fluid. The thermal and hydrolytic stability of the produced ester was high owing to the transesterification method employed in this study. The reaction was performed using 2-ethylhexanol and methyl laureate esters in the presence of sodium methoxide as a catalyst. In order to obtain the optimum synthesis conditions, a response surface methodology (RSM) was appraised based on the central composite design (CCD). The optimum conditions were determined as follows: 0.6 wt.% catalyst, 70°C reaction temperature, 1:1.5 molar ratio, and 11.5 min of reaction time. The results of 77 wt.% 2-ethylhexyl ester (2-EH) illustrated a high agreement between the experimental and RSM models. The reaction product contained 77 wt.% 2-EH and 23% 2-ethylhexanol. The kinematic viscosity was 5 mm²/s at 40°C and 1.5 mm²/sec at 100°C; the specific gravity was 0.854, flash point was 170°C, and pour point was ?7°C. The produced product showed similar properties to the available commercial product. However, it was observed that the mud formulation using the synthesized base oil had superior rheological properties at 121°C.