Experimental Investigation of Catalytic Surface Reaction for Different Metal Surfaces

The use of a catalytic surface to enhance chemical reaction rates is a well established and common practice. However, its use in combustion devices for enhancing combustion reaction is somewhat less common and more recent. Catalytic combustors, because of their inherent ability to operate at very lean air fuel mixtures, can maintain a relatively low combustion temperature and hence reduce the formation of NOx significantly. Further the catalytic coating on the combustion chamber walls enhances the combustion process by increased rate of pre-flame reactions. This provides a basis for catalytic combustion in lean burn engine. A considerable amount of effort has been devoted in the present work to this experimental study and compares different catalyst reaction performance.A cylindrical chamber is fabricated and air-fuel mixture is passed through the chamber. A metal tube coated with the catalyst is placed inside the control volume and it is heated by an electric heater. The air-fuel mixture undergoes pre-flame combustion reaction and as a result of this, the miniature temperature increases. Various catalytic surfaces like mild steel, Nickel, Chromium and copper were tested. The activation temperatures of these catalytic surfaces were obtained from this experimental work. Keywords: catalytic reaction, LPG, activation energy, catalytic coatin

Green synthesis of ZnO nanoparticles and their photocatalyst degradation and antibacterial activity

The current study aimed to synthesize nanoparticles of Zinc oxide (ZnO) using the extract of Acalypha indica leaves and their photocatalyst degradation and antibacterial properties were also measured. The biosynthesized nanoparticles were analyzed using XRD, UV-visible, FT-IR, and SEM with EDAX, DLS, PL, and Zeta potential analysis. The synthesized nanoparticles had a mean size of 16 nm measured by XRD which was highly pure, and their spherical shape was confirmed by SEM. The UV-visible confirmed that ZnO nanoparticles have a direct band gap energy is 3.34 eV. The measured zeta size and potential of synthesized nanoparticles were 46 nm and -27 mV, respectively, determined by the DLS technique can be considered moderately stable colloidal solutions. The FT-IR analysis confirmed the presence of functional groups in the leaf extract and the ZnO nanoparticles. The biosynthesized ZnO nanoparticles have a homogeneous spherical morphology and the average particle is 35 nm. The PL analyses performed on synthesized nanoparticles showed a sharp blue band at 362 nm, which was attributed to the defects of structure in ZnO crystals. During natural sunlight illumination, ZnO nanoparticles demonstrated notable degradation of the dye methyl blue (MB). At 90 min of illumination, the degradation efficiency achieved was 96 %. Antibacterial properties were observed for synthesized nanoparticles against four bacterial strains, including Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The highest zone of inhibition was observed against Escherichia coli (25.2 mm). Overall, these studies indicate that Acalypha indica is a good sell for planting, and has the greatest chance of being used to develop nanoparticles for protection against environmental pollution and human health

A joint numerical study of multi-regime turbulent combustion

This article presents a joint numerical study on the Multi Regime Burner configuration. The burner design consists of three concentric inlet streams, which can be operated independently with different equivalence ratios, allowing the operation of stratified flames characterized by different combustion regimes, including premixed, non-premixed, and multi-regime flame zones. Simulations were performed on three LES solvers based on different numerical methods. Combustion kinetics were simplified by using tabulated or reduced chemistry methods. Finally, different turbulent combustion modeling strategies were employed, covering geometrical, statistical, and reactor based approaches. Due to this significant scattering of simulation parameters, a conclusion on specific combustion model performance is impossible. However, with ten numerical groups involved in the numerical simulations, a rough statistical analysis is conducted: the average and the standard deviation of the numerical simulation are computed and compared against experiments. This joint numerical study is therefore a partial illustration of the community's ability to model turbulent combustion. This exercise gives the average performance of current simulations and identifies physical phenomena not well captured today by most modeling strategies. Detailed comparisons between experimental and numerical data along radial profiles taken at different axial positions showed that the temperature field is fairly well captured up to 60 mm from the burner exit. The comparison reveals, however, significant discrepancies regarding CO mass fraction prediction. Three causes may explain this phenomenon. The first reason is the higher sensitivity of carbon monoxide to the simplification of detailed chemistry, especially when multiple combustion regimes are encountered. The second is the bias introduced by artificial thickening, which overestimates the species’ mass production rate. This behavior has been illustrated by manufacturing mean thickened turbulent flame brush from a random displacement of 1-D laminar flame solutions. The last one is the influence of the subgrid-scale flame wrinkling on the filtered chemical flame structure, which may be challenging to model.</p

A joint numerical study of multi-regime turbulent combustion

This article presents a joint numerical study on the Multi Regime Burner configuration. The burner design consists of three concentric inlet streams, which can be operated independently with different equivalence ratios, allowing the operation of stratified flames characterized by different combustion regimes, including premixed, non-premixed, and multi-regime flame zones. Simulations were performed on three LES solvers based on different numerical methods. Combustion kinetics were simplified by using tabulated or reduced chemistry methods. Finally, different turbulent combustion modeling strategies were employed, covering geometrical, statistical, and reactor based approaches. Due to this significant scattering of simulation parameters, a conclusion on specific combustion model performance is impossible. However, with ten numerical groups involved in the numerical simulations, a rough statistical analysis is conducted: the average and the standard deviation of the numerical simulation are computed and compared against experiments. This joint numerical study is therefore a partial illustration of the community's ability to model turbulent combustion. This exercise gives the average performance of current simulations and identifies physical phenomena not well captured today by most modeling strategies. Detailed comparisons between experimental and numerical data along radial profiles taken at different axial positions showed that the temperature field is fairly well captured up to 60 mm from the burner exit. The comparison reveals, however, significant discrepancies regarding CO mass fraction prediction. Three causes may explain this phenomenon. The first reason is the higher sensitivity of carbon monoxide to the simplification of detailed chemistry, especially when multiple combustion regimes are encountered. The second is the bias introduced by artificial thickening, which overestimates the species’ mass production rate. This behavior has been illustrated by manufacturing mean thickened turbulent flame brush from a random displacement of 1-D laminar flame solutions. The last one is the influence of the subgrid-scale flame wrinkling on the filtered chemical flame structure, which may be challenging to model.</p

Effects of ultraviolet-B enhanced radiation and temperature on growth and photochemical activities in Vigna unguiculata

Changes in growth characteristics and photochemical activities in Vigna unguiculata L. Walp seedlings maintained at constant temperature of 10, 20, 30 and 40 °C under control and ultraviolet-B enhanced radiation (UV-B) were investigated. UV-B retarded the shoot elongation and also leaf expansion to a great extent at 30 °C but produced only marginal changes at 20 and 40 °C. Similar response was also observed with respect to changes in leaf fresh and dry masses and total chlorophyll (Chl) content under these temperatures. At 10 °C the total Chl content was 3-fold higher under the treatment than under control conditions. In seedlings growing at 20 and 30 °C the overall photosynthetic electron transport (H2O → methyl viologen) showed a significant enhancement during the 36-h UV-B treatment and thereafter a gradual reduction. Although a similar trend was found in photosystem 1 (PS1), the inhibition even after 60 h of UV-B treatment was not statistically significant. Photosystem 2 (PS2) activity was inhibited in seedlings treated for 60 h by UV-B at 20 and 30 °C. However, no inhibition was observed at 40 °C. No detectable photochemical activity was found in seedlings grown at 10 °C under either control or UV-B enhanced irradiation although the chloroplasts contained Chl.Peer Reviewe

Effects of ultraviolet-B radiation in the CO2 fixation, photosystem II activity and spectroscopic properties of the wild and mutant Anacystis cells

Changes in photosystem II activity measured in wild and DCMU resistant mutant cells of Anacystis nidulans, after ultraviolet-B (UV-B) irradiation were investigated. UV-B treatment of wild cells drastically decreased PS II activity, while the mutant cells demonstrated certain degree of resistance to such damages. Decrease in the photosynthetic rate was found to be primarily due to the loss of energy transfer from phycobilisoms (PBS) to chlorophyll (Chl) as the former in cyanobacteria acts as the primary light harvesting complex, This is supported by studies of the absorption and fluorescence excitation and emission spectra.Peer Reviewe

Ultraviolet-B (280-320 nm) radiation induced changes in photosynthetic electron transport during aging of isolated Vigna chloroplasts

Chloroplasts isolated from Vigna unguiculata L. seedlings grown under control and ultraviolet-B (UV-B) enhanced fluorescent radiations, when incubated at 0 °C under irradiation and in darkness showed differential loss in various photosynthetic activities. In control chloroplasts, the whole chain and photosystem (PS) 2 reactions were drastically reduced under both irradiation and darkness. PS1 activity also showed significant reduction. In contrast to this, UV-B affected chloroplasts demonstrated high stability by slowing down the inactivation processes. Diphenyl carbazide and NH2OH restored the PS2 activity more in control chloroplasts than in UV-B chloroplasts. Mn2+ failed to restore the PS2 activity in both chloroplast samples. The loss in PS2 activity was primarily due to the loss of 33, 23, and 17 kDa polypeptides in control chloroplasts and to a marginal loss of them in the UV-B chloroplasts.Peer Reviewe

Studies on performance and emission characteristics of multicylinder diesel engine using hybrid fuel blends as fuel

539-543This study compared performance and emission characteristics of hybrid fuel blend [diesel-ethanol (anhydrous)-biodiesel (methyl esters of pungamia oil)] with diesel in a multi cylinder, naturally aspirated, direct injection diesel engine. Brake thermal efficiency of engine operated with hybrid fuel blends is found to be slightly higher than that of diesel fuel. Smoke and oxides of nitrogen (NOx) are found to be reduced simultaneously, while using hybrid fuel blends as fuel. Hydrocarbon (HC) emission is higher than diesel fuel for 10% ethanol addition, however when percentage of pungamia methyl ester (PME) increases in blends, HC emission is reduced.Carbon monoxide emission (CO) is found to be higher and a significant reduction is observed whenincreasing percentage of PME in blends

Study on the Synthesis, Structural, Optical and Electrical Properties of ZnO and Lanthanum Doped ZnO Nano Particles by Sol-Gel Method

International audienceIn this study, pure and lanthanum doped ZnO nano particles have been succaessfully synthesized by sol-gel method using the mixture of Zinc acetate dihydrate and ethanol solution. The powders were calcination at 600°C for 2h. The effect of lanthanum incorporation on the structure, morphology, optical and electrical conductivity were examined by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Absorption (EDAX), Fourier transform infrared spectroscopy (FTIR), UV and Photo Luminescence (PL) Characterization. The average particle size of the synthesized ZnO nanoparticles is calculated using the Scherrer formula and is found to be of less than 20 nm. Luminescence as well as conductivity properties were found to be enhanced for the La doped ZnO nanoparticles. Introduction. Synthesize and study of nanostructured materials have become a major attractive interdisciplinary area of research over the past few decades. Recently rare earth ion doped II-IV semiconductor nano particles have received much attention because such doping can modify and improve optical properties of II-VI semiconductor nanoparticles by large amount [1-4]. Zinc Oxide is a transparent electro conductive and piezo electric material. Zinc Oxide is an excellent ultraviolet absorber and antibacterial agent. ZnO is one of the metal oxides which attracts due to its direct band gap energy of 3.37eV and large excitation binding energy of 60 meV at room temperature which provides excitonic emission more efficiently even at high temperature. ZnO is particularly important because of their unique optical/electronic properties and promising applications in various fields such as photonic catalysis [5], light emitting diodes [6], field emission, gas sensors [7], fluorescent materials and solar cells [8]