Numerical investigations of cooling holes system role in the protection of the walls of a gas turbine combustion chamber

Numerical simulations in a gas turbine Swirl stabilized combustor were conducted to investigate the effectiveness of a cooling system in the protection of combustor walls. The studied combustion chamber has a high degree of geometrical complexity related to the injection system as well as the cooling system based on a big distribution of small holes (about 3,390 holes) bored on the flame tube walls. Two cases were considered respectively the flame tube without and with its cooling system. The calculations were carried out using the industrial CFD code FLUENT 6.2. The various simulations made it possible to highlight the role of cooling holes in the protection of the flame tube walls against the high temperatures of the combustion products. In fact, the comparison between the results of the two studied cases demonstrated that the walls temperature can be reduced by about 800°C by the mean of cooling holes technique.     

Description of complementary actions of mineral and organic additives in thermoplastic polymer composites by Flame Retardancy Index

This work visualizes the complementary actions of organic and mineral additives in model thermoplastic polymer composites in terms of Flame Retardancy Index (FRI). Thermal and flame retardancy behaviors of ethylene‐vinyl acetate copolymer (EVA) composites containing calcium carbonate (CC) mineral and ammonium polyphosphate (APP) organic additives were studied varying composition of additives in the 80/20 EVA/(xCC + (20 ? x)APP) composites with x denoting 0, 5, 10, 15, and 20 wt%. Thermogravimetric analysis (TGA) revealed that the onset temperature of composites and the remaining residue were increased by combination of APP and CC, while cone calorimetry results were indicative of a promising flame retardancy performance at a given composition of APP and CC. Based on FRI values, we made distinguished samples from flame retardancy performance viewpoint, where the best flame retardancy was obtained by combination of 15 wt% APP and 5 wt% CC, as reflected in FRI value of 3.08. By contrast, samples containing only APP or CC revealed low resistance against flame, as signaled by FRI values of 0.99 and 0.89, respectively. X‐ray diffraction (XRD) analysis was made on remaining residue collected at the end of cone calorimetry measurements. Moreover, Raman analysis confirmed barrier effect of flame retardancy for EVA/(5APP + 15CC) sample, featured by a higher graphitization level as well as a thicker yet more homogenous char layer. Mechanical behavior analysis of composites revealed an acceptable level of properties, particularly high elongation at break, which was almost independent of formulation. However, a minor loss in yield stress was observed, especially for EVA(10CC + 10APP) sample.     

Thermal performance of an integrated collector storage solar water heater (ICSSWH) with a storage tank equipped with radial fins of rectangular profile

The thermal behavior of an integrated collector storage solar water heater (ICSSWH) is numerically studied using the package Fluent 6.3. Based on the good agreement between the numerical results and the experimental data of Chaouachi and Gabsi (Renew Energy Revue 9(2):75–82, 2006), an attempt to improve this solar system operating was made by equipping the storage tank with radial fins of rectangular profile. A second 3D CFD model was developed and a series of numerical simulations were conducted for various SWH designs which differ in the depth of this extended surface for heat exchange. As the modified surface presents a higher characteristic length for convective heat transfer from the storage tank to the water, the fins equipped storage tank based SWH is determined to have a higher water temperature and a reduced thermal losses coefficient during the day-time period. Regarding the night operating of this water heater, the results suggest that the modified system presents higher thermal losses.     

Reactivity of 4,5-Dichlorophthalic Anhydride towards Thiosemicarbazide and Amines: Synthesis,Spectroscopic Analysis,and DFT Study

The cyclic anhydrides are broadly employed in several fields, such as the chemical, plastic, agrochemical, and pharmaceutical industries. This study describes the chemical reactivity of 4,5-dichlorophthalic anhydride towards several nucleophiles, including thiosemicarbazide and different amines, to produce the carboxylic acid derivatives resulting from anhydride’s opening, namely, phthalimide and dicarboxylic acid (1–12) products. Their chemical structures are confirmed by NMR, IR and MS spectra analyses. Density–functional theory (DFT) studies are performed using (DFT/B3LYP) with the 6-311G(d, p) basis sets to recognize different chemical and physical features of the target compounds.     

Rapid Validated Thin-Layer Chromatography—Densitometry for the Simultaneous Determination of Three Co-formulated Drugs Used for Common Cold Treatment

JPC – Journal of Planar Chromatography – Modern TLC - A rapid validated thin-layer chromatography (TLC)—densitometric method has been developed for the simultaneous determination...     

Micellization and Adsorption Parameters of Poly(Propylene Oxide)/Poly(Ethylene Glycol) Block and Graft Copolymers in Aqueous Medium

This work aims to measure the adsorption and micellization parameters of new water soluble nonionic amphiphilic block and graft copolymers based on hydrophilic poly (ethylene glycol) (PEG) and hydrophobic poly (propylene oxide) (PPO) at ambient temperature and normal atmospheric pressure. The chemical composition and molecular weights of the prepared copolymers were determined from ¹H NMR analyses. The surface properties of the prepared surfactants were determined by measuring the surface tension at different temperatures. The surface tension, critical micelle concentration, and surface activities were determined at different temperatures. Surface parameters such as surface excess concentration, the area per molecule at interface and the effectiveness of surface tension reduction were determined from the adsorption isotherms of the prepared surfactants. Some thermodynamic data for the adsorption and micellization process were calculated and are discussed.     

Synthesis and characterization of styrenic polymers with pendant pyrazole groups. II

The synthesis of styrenic monomers that have pyrazolic or bipyrazolic pendant groups is described. Their homopolymerization and their copolymerization with maleic anhydride (MA) and N-(3-acetoxy propyl) maleimide is reported. The monomers were prepared from the Williamson reaction between 2-pyridine carbinol, hydroxy monopyrazole, hydroxy bipyrazole, and chloromethyl styrene. The homopolymerizations of such styrenic monomers were tried under different conditions, which led to low molecular weight polymers with a high polydispersity. However, alternating copolymers were obtained using maleic anhydride or N-(3-acetoxy propyl) maleimide as comonomers, as shown by ¹H-NMR, elemental analysis, and reactivity ratios r₁ and r₂. Furthermore, the hydrolysis of the acetate function of different copolymers was performed quantitatively. Unlike the acetoxy copolymers, such products do not have any glass transition temperature. Thermogravimetric investigations have shown that these copolymers exhibit good thermostability. © 1994 John Wiley & Sons, Inc.     

4‐[Bis(1,5‐dimethyl‐1H‐pyrazol‐3‐yl­meth­yl)­amino]phenol monohydrate

The crystal structure of the title compound, C₁₈H₂₃N₅O·H₂O, shows mol­ecules containing a phenol group linked perpendicularly to a roughly planar fragment comprising two pyrazole rings. Mol­ecules are stacked perpendicular to the [101] direction, with their phenol groups disposed alternately. The mol­ecular packing in the crystal is stabilized by hydrogen bonding involving water mol­ecules.     

Densities and volumetric properties of (N-(2-hydroxyethyl)morpholine + ethanol, + 1-propanol, + 2-propanol, + 1-butanol,and + 2-butanol) at (293.15, 298.15, 303.15, 313.15, and 323.15) K

Densities of binary mixtures of N-(2-hydroxyethyl)morpholine with ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol were measured over the entire composition range at temperatures from (293.15 to 323.15) K and atmospheric pressure using a vibrating-tube densimeter. The excess molar volumes, V^E were calculated from density data and fitted to the Redlich–Kister polynomial equation. Apparent molar volumes, partial molar volume at infinite dilution and the thermal expansion coefficient of the mixtures were also calculated. The V^E values were found to be negative over the entire composition range and at all temperatures studied and become less negative with increasing carbon chain length of the alkanols.     

Neutral pyridyl-functionalized C,N-ortho-chelated aminoaryl platinum(II) corner building blocks for application in coordination reactions

Two homoleptic pyridyl-functionalized C,N-ortho-chelating aminoaryl platinum(II) complexes, cis-[Pt(eta(2)-C,N)] (3a,b), were prepared via an unconventional method involving the initial synthesis of a bromide-functionalized C,N-chelating aminoaryl platinum(II) precursor complex 8, to which subsequently pyridyl groups were attached via a Suzuki-Miyaura C-C coupling reaction. The electron-donating properties of the pyridyl nitrogen atoms of the resulting complexes (3a,b) were used in complexation reactions with monocationic NCN-pincer (NCN = [C6H3(CH2NMe2)(2-)2,6]-) platinum(II) (11a) and palladium(II) (12a) nitrate complexes [M(NCN)(NO3)], thereby obtaining four trimetallic coordination complexes 16-19. The difference in the pyridine-metal coordination behavior between platinum and palladium was studied by varying the ratios of the reagents and by variable-temperature NMR experiments. IR and Raman analyses of 11a and 12a were performed to determine the coordination behavior of the nitrate counteranion, and it was found that both NO3- and H2O coordinate to the metal centers. The crystal structure determinations of free pyridyl complex 3a, [Pt(NCN)(NO3)] (11a), and [Pt(NCN)(NO3)].(H2O) (11b), as well as the crystal structure of trisplatinum coordination complex 16, are reported.