Study of cavitation in hydro turbines - a review

Reaction turbines basically Francis turbines and propeller/Kaplan turbines are suitable for medium and low head hydropower sites. The management of the small hydropower plants is an important factor, for achieving higher efficiency of hydro turbines with time. Turbines show declined performance after few years of operation, as they get severely damaged due to various reasons. One of the important reasons is erosive wear of the turbines due to cavitation. Reaction turbines, however are more prone to cavitation especially Francis turbines where a zone in the operating range is seriously affected by cavitation and considered as forbidden zone. Cavitation is a phenomenon which manifests itself in the pitting of the metallic surfaces of turbine parts because of the formation of cavities. In the present paper, studies undertaken in this field by several investigators have been discussed extensively. Based on literature survey various aspects related to cavitation in hydro turbines, different causes for the declined performance and efficiency of the hydro turbines and suitable remedial measures suggested by various investigators have been discusse

A study on Morphological and Mechanical Characterization of Al-4032/SiC/GP Hybrid Composites

The pattern of metal matrix composites can be enhanced by integrating the concept of hybrid metal matrix composite to produce newer engineering materials with improved properties. The morphological and mechanical characteristics of Al-4032/SiC/GP hybrid composites have been investigated. The aluminium alloy (Al-4032) based hybrid composites have been fabricated through the bottom pouring stir casting set up, by reinforcing the silicon carbide (SiC) and granite powder ceramic particles as the reinforcement material at various fraction levels i.e. 0, 3, 6, 9 weight% in equal proportion. The reinforcement particle size is up to 54μm. The microstructural characterization of the hybrid composite samples has been carried out using an optical microscope, SEM, and XRD. The study reveals that the reinforcement hybrid particles (SiC + GP) are almost uniformly distributed throughout the matrix phase. The mechanical properties (tensile strength, impact strength, and microhardness) of the hybrid composite samples have been obtained and found to be better than the unreinforced alloy.

Systematic review on applicability of magnetic iron-oxides integrated photocatalysts for degradation of organic pollutants in water

Owing to biocompatibility, abundance, and low cost, magnetic iron oxides are well suited for the design of efficient and magnetically separable photocatalysts for water treatment. This review presents a detailed survey of magnetic iron oxide–integrated photocatalysts (MIOIPs), in which we have discussed essential conditions needed for designing of efficient MIOIPs for water purification. The synthesis methods and detailed experimental setups for fabrication of MIOIPs were discussed, and the integration manners of iron oxides (Fe2O3, Fe3O4, FeO, and ferrites) with binary, ternary, and quaternary non-magnetic photocatalysts have been categorized. The mechanistic view of enhanced photocatalytic activity caused by different MIOIPs under various light sources was also elaborately argued. The role of various reactive species in photocatalytic oxidative degrading of organic pollutants was investigated. Altogether, this review article has compressively considered and discussed various signs of advancements made toward the synthesis of MIOIPs and their stability, recyclability, and catalytic efficacy for wastewater treatment

Synthesis of Eu3+−doped ZnO/Bi2O3 heterojunction photocatalyst on graphene oxide sheets for visible light-assisted degradation of 2,4-dimethyl phenol and bacteria killing

We reported the immobilization of binary heterojunction Eu3+-ZnO/Bi2O3 over the surface of graphene oxide (GO) sheets by precipitation method to compose a visible light drive photocatalyst. The ternary nanocomposites were characterized by different spectral technique like FESEM, FTIR, XRD, XPS, EDX, HRTEM, UV–visible, PL, HPLC and LCMS analysis. The high specific surface area of 106.0 m2g-1 of Eu3+-ZnO/Bi2O3/GO nanocomposites was ascertained by BET adsorption-desorption isotherm. The nano-composite exhibit excellent photo-efficiency for the photodegradation of 2, 4-dimethyl phenol (DMP) under visible region and was almost completely mineralized in 100 min as compared to the bare and binary system. The mineralized products of DMP were analyzed by HPLC and LCMS analysis. The kinetic model suggests the degradation pathway obeys pseudo-first order kinetic. Their antibacterial property were assessed against E. coli bacteria and nearly 90% of gram negative bacteria were killed by using ternary photocatalyst as determined by CFU method. Also, Eu3+-ZnO/Bi2O3/GO nanocomposites possessed significant recycle efficiency up to six consecutive cycles which is beneficial to minimize the tariff. The improved photo-efficiency is due to the extension towards visible region, increase surface area, and high charge separation in ternary heterojunction

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Study of cavitation in hydro turbines--A review

Reaction turbines basically Francis turbines and propeller/Kaplan turbines are suitable for medium and low head hydropower sites. The management of the small hydropower plants is an important factor, for achieving higher efficiency of hydro turbines with time. Turbines show declined performance after few years of operation, as they get severely damaged due to various reasons. One of the important reasons is erosive wear of the turbines due to cavitation. Reaction turbines, however are more prone to cavitation especially Francis turbines where a zone in the operating range is seriously affected by cavitation and considered as forbidden zone. Cavitation is a phenomenon which manifests itself in the pitting of the metallic surfaces of turbine parts because of the formation of cavities. In the present paper, studies undertaken in this field by several investigators have been discussed extensively. Based on literature survey various aspects related to cavitation in hydro turbines, different causes for the declined performance and efficiency of the hydro turbines and suitable remedial measures suggested by various investigators have been discussed.Hydro turbine Cavitation Rotating machinery Computational fluid dynamics

GdVO4 modified fluorine doped graphene nanosheets as dispersed photocatalyst for mitigation of phenolic compounds in aqueous environment and bacterial disinfection

The agglomeration of graphene based photocatalysts is major bottleneck for their applicability in slurry type photoreactors. In this work, we have prepared fluorine doped graphene (FG) as high dispersed adsorbent by sonochemical exfoliation method. GdVO4 nanoparticles were anchored on FG to fabricate GdVO4/FG photo catalyst. The high-dispersion of FG and GdVO4/FG was ascertained by zeta potential measurements and Tyndall effect. The atomic force microscope analysis depicted that thickness of FG and GdVO4/FG was less than 2.0 nm. The band gap of GdVO4/FG was 2.1 eV. The high surface area of GdVO4/FG was suited for adsorption coupled photocatalysis involving mineralization of phenol and 2, 4-dinitrophenol (DNP) in aqueous medium. The photodegradation process followed pseudo first order kinetics. The simultaneous adsorption and photocatalysis was most efficient process for degradation of selected phenolic compounds. Under visible light, both phenol and DNP mineralized in 7 and 9 h, respectively. The high performance liquid chromatography and mass spectrometry confirmed the formation of intermediate during degradation process which ultimately mineralized into CO2 and H2O. The photocatalytic activity of GdVO4/FG was also tested for bacterial disinfection of Pseudomonas fluorescence, Staphylococcus aureus, Streptococcus enterica, Bacillus subtilis and Escherichia coli bacteria. The oxidative radical species OH center dot and O-2(center dot-) played vital role in photodegradation and disinfection process. Due to high dispersion and recyclability, GdVO4/FG could be used as an efficient photocatalyst for removal of both biotic and abiotic pollutants present in water

Fabrication of fluorine doped graphene and SmVO4 based dispersed and adsorptive photocatalyst for abatement of phenolic compounds from water and bacterial disinfection

During heterogeneous photocatalysis, high dispersion of photocatalyst is vital for efficiency of slurry type photoreactors. In this work, we have prepared fluorine doped graphene (FG24) as a highly dispersible adsorbent by sonochemical exfoliation method. Moreover, SmVO4 (SV) nanoparticles were immobilized onto the surface of FG24 to prepare SV/FG24 photocatalyst, using post synthesis method. The zeta potential and Tyndall effect experiments confirmed the formation of highly dispersed SV/FG24 photocatalyst. The thickness of both FG24 and SV/FG24 was less than 2.0 nm. The band gap of SV/FG24 was 2.28 eV. The high surface area of SV/FG24 was suitable for adsorptive removal of phenol and 2, 4-dinitrophenol (DNP). The simultaneous process of adsorption and photocatalysis was the most effective for the degradation of selected phenolic compounds. Both phenol and DNP were mineralized in 10 h under visible light. The intermediates formation during the degradation process was proved by high-performance liquid chromatography and mass spectrometry analysis. The photocatalytic activity of SV/FG24 was also tested for photocatalytic bacterial disinfection of Escherichia coli, Bacillus subtilis, Pseudomonas fluorescence, Staphylococcus aureus, and Streptococcus enterica bacteria. The selected bacteria were deactivated using SV/FG24 in 3 h under visible light. Both OH˙ and O2˙¯ radicals played an important role during both degradation and disinfection process. Due to significant recyclability, SV/FG24 could be used as cost-effective photocatalyst for wastewater treatment. Unlike conventional slurry photo-reactors, no magnetic stirring was used during photocatalytic degradation reactions. We have successfully fabricated high-dispersed photocatalyst which remained dispersed for 10 h and effectively used for photocatalytic water purification process