Analysis of turbulence and surface growth models on the estimation of soot level in ethylene non-premixed flames

Soot prediction in a combustion system has become a subject of attention, as many factors influence its accuracy. An accurate temperature prediction will likely yield better soot predictions, since the inception, growth and destruction of the soot are affected by the temperature. This paper reported the study on the influences of turbulence closure and surface growth models on the prediction of soot levels in turbulent flames. The results demonstrated that a substantial distinction was observed in terms of temperature predictions derived using the k-ε and the Reynolds stress models, for the two ethylene flames studied here amongst the four types of surface growth rate model investigated, the assumption of the soot surface growth rate proportional to the particle number density, but independent on the surface area of soot particles, f(A_s) = ρN_s, yields in closest agreement with the radial data. Without any adjustment to the constants in the surface growth term, other approaches where the surface growth directly proportional to the surface area and square root of surface area, f(A_s) = A_s and f(A_s) = √A_s, result in an under-prediction of soot volume fraction. These results suggest that predictions of soot volume fraction are sensitive to the modelling of surface growth.     

Effect of Binary and Ternary Combination of Metal Salt Mordants on Dyeing and Fastness Properties of Natural Protein Fibre with Juglans regia L. Dye

The present article focuses on the effect of different combinations of metal mordants on color characteristics and fastness properties of natural dye extracted from Juglan regia L bark powder. The influence of different types of mordant combinations such as alum + ferrous sulphate, alum + stannous chloride, ferrous sulphate + stannous chloride, and alum + ferrous sulphate + stannous chloride on color parameters has been investigated in terms of CIELab (L*, a*, b*, c*, and h°) and K/S values. The fastness properties with respect to light, washing, and crocking of developed shades were determined according to ISO and AATCC test methods. Based on the experimental results, it has been found that 96 shades with novel and fashionable hues were produced by the use of these metal salt combinations. It was also found that all mordanted samples had satisfactory light and wash fastness ratings. Dry rub fastness was found relatively better than wet rub fastness.     

Hydroxyapatite and Fluoridated Hydroxyapatite Coatings and Their Effects on Commercially Pure Magnesium Corrosion Response

Dicalcium-phosphate dehydrate, converted to hydroxyapatite by post-treatment in sodium hydroxide, and fluoridated hydroxyapatite were electrodeposited on commercially pure magnesium substrates that were pretreated with sodium hydroxide. The coatings’ crystalline structure, thickness, scratch hardness, morphology and chemical composition were characterised by GIXRD, microscratch testing platform, SEM and EDS. The results showed that the apatite coatings had highly crystalline structure, acceptable scratch hardness, flake-like morphology and acceptable chemical composition. Corrosion behaviour of the uncoated and coated substrates was investigated by potentiodynamic polarization and immersion tests in simulated body fluid. The coated substrates, especially fluoridated hydroxyapatite coated substrates, showed significantly lower corrosion rates compared to uncoated substrates. The polarisation curves showed that the coatings hindered anodic reactions; the corrosion potentials were shifted toward less-negative. In general, this study concluded that the corrosion rate of commercially pure magnesium could be significantly decreased to be a candidate for future cost-effective biodegradable orthopaedic implants.