Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884
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Item Sustainable Nanoplasmon-Enhanced Photoredox Reactions: Synthesis, Characterization, and Applications(Wiley-VCH Verlag info@wiley-vch.de, 2020) Bhattacharya, C.; Saji, S.E.; Mohan, A.; Madav, V.; Jia, G.; Yin, Z.Plasmonic materials with their unique properties, such as light-excitable resonant oscillation of conduction electrons, strong local electric field, and energetic hot charges (electrons/holes) etc., have overcome the limitations of traditional photoredox catalysts. They are especially important due to their superior light focusing ability, from free-space wavelengths to the sub-wavelength range. Although noble metal plasmonic enhancement has been recognized as one of the most important strategies in photocatalysis, the high cost and limited spectral range absorption of noble metals remain the biggest challenges for their practical application, which has led to a gradual shift in the focus on the abundant and less expensive non-noble metal plasmonics. Recently, various non-noble plasmonic materials such as non-noble metals (Cu, Al, Ni and Bi), metal oxides and chalcogenides (WO3-x, MoO3-x, NiO, MNbO3, where M = Ca, Sr or Ba; Fe2O3, SrTiO3, In2O3, Cu2-xS and Bi2Se3), nitrides (TiN, ZrN, HfN and WN) have emerged as efficient photocatalysts. Herein, the door to the relatively new and exciting world of noble metal-free plasmonic materials and their promising applicability in solar-energy driven photo-redox catalysis such as water splitting, CO2 reduction, nitrogen reduction, organic transformations and environment remediation is opened. Their synthesis methods and a plethora of characterization techniques are also systematically exhibited. © 2020 Wiley-VCH GmbHItem Directional synthesis of aviation-, diesel-, and gasoline range hydrocarbon fuels by catalytic transformations of biomass components: An overview(Elsevier Ltd, 2023) Dutta, S.; Madav, V.; Joshi, G.; Naik, N.; Kumar, S.Selective conversion of heavily oxygenated biomolecules into hydrocarbon-based liquid transportation fuels with stipulated structural traits is of academic and industrial significance. This work provides an overview of producing fuel precursors from biomass components and their catalytic transformation into aviation-, diesel-, and gasoline-range hydrocarbon fuels (HCFs). Strategic applications of various organic transformations for the molecular design of targeted products have been rationalized. Construction and alteration of the carbon skeletal system in the fuel candidates via chemical-catalytic transformations have been highlighted. Emphasis has also been given to the process conditions and details of the catalysts employed in these processes. Critical analysis of the literature data presented in this review will assist the researchers in developing more proficient processes for the biorenewable production of drop-in HCFs. © 2023 Elsevier LtdItem Studies for removal of tar from producer gas in small scale biomass gasifiers using biodiesel(Elsevier Ltd, 2019) Madav, V.; Das, D.; Kumar, M.; Surwade, M.; Parikh, P.P.; Sethi, V.Biomass gasification based electricity generation systems are emerging as an important component of the decentralised energy supply systems in rural India. Each type of gasifier has different reaction conditions, temperature, residence time, pressure, feedstock, reactor design, and therefore the tar and particulate matter (PM) compositions and concentrations are found to vary. A field study was conducted on a 35 kWe downdraft gasifier to measure and characterize the tar in producer gas using GC-MS, for rice husk and pine needles as the two biomass feeds. Use of water-based scrubbers for removal of tar and PM is prevalent, however it is often the case that such clean-up is not adequate for meeting the engine manufacturers’ requirements for the quality of intake gas. Limited attempts have been reported for the use of organic solvent based gas cleaning in small scale downdraft gasifiers in the range 15–50 kWe. In the present work, toluene, naphthalene and phenol were selected as representative compounds of tar, and methyl oleate was selected to represent biodiesel as an organic solvent. A bench scale packed bed scrubber was designed for 95% removal of toluene. An 86–97% removal of toluene from the gas stream was achieved, and similar results were obtained for phenol and naphthalene. Further experiments were carried out with actual producer gas from a 1 kWe downdraft wood gasifier. Pongamia pinnata based biodiesel was used as the solvent, and 88–92% of the tar removal from the producer gas stream was achievable. © 2019 Elsevier LtdItem Characterization and upgradation of crude tire pyrolysis oil (CTPO) obtained from a rotating autoclave reactor(Elsevier Ltd, 2019) Mohan, A.; Dutta, S.; Madav, V.Many of the inferior fuel properties of crude tire pyrolysis oil (CTPO) can be attributed to the presence of polar organic compounds such as various oxygenates, nitrogen heterocycles and sulfur-containing compounds. An efficient, straightforward and scalable pathway of removing the polar fraction from CTPO is crucial in improving its fuel properties. In this work, CTPO produced by thermal pyrolysis (400 °C, 0.2 bar, 4 rpm, 5 h) of scrap automotive tires in a rotating autoclave reactor (8-tons) has been upgraded using silica gel (60–120 mesh) as adsorbent and petroleum ether as diluent. In two different strategies, CTPO was first diluted with petroleum ether and (1) passed through a column of silica gel (CoTPO) or (2) mechanically stirred with silica gel (StTPO) followed by solvent evaporation to afford upgraded oil. Both crude and upgraded TPO samples were extensively analyzed for chemical composition and fuel properties and compared with each other. Analytical techniques like GC–MS, 1H NMR, FTIR, and elemental analysis showed significantly less polar fractions in CoTPO and StTPO compared to CTPO. The cetane index of CoTPO and StTPO were found to be 35 and 40, respectively compared to 33 in CTPO. Sulfur content decreased by 19% and 34% in CoTPO and StTPO, respectively. The acid value of CoTPO and StTPO were found to be 0.8 and 0.6 compared to 12.2 in CTPO. The TGA data showed better thermal stability of upgraded oil samples. StTPO showed better chemical composition and fuel properties compared to CoTPO that can be explained by its longer contact time with silica gel adsorbent. © 2019 Elsevier LtdItem Analytical solution to transient inverse heat conduction problem using Green’s function(Springer Science and Business Media B.V., 2020) Parida, R.K.; Madav, V.; Hindasageri, V.A transient inverse heat conduction problem concerning jet impingement heat transfer has been solved analytically in this paper. Experimentally obtained transient temperature history at the non-impinging face, assumed to be the exposed surface in real practice, is the only input data. Aim of this study is to estimate two unknown thermo-physical parameters—overall heat transfer coefficient and adiabatic wall temperature—at the impinging face simultaneously. The approach of Green’s Function to accommodate both the transient convective boundary conditions and transient radiation heat loss is used to derive the forward model, which is purely an analytical method. Levenberg–Marquardt algorithm, a basic approach to optimisation, is used as a solution procedure to the inverse problem. An in-house computer code using MATLAB (version R2014a) is used for analysis. The method is applied for a case of a methane–air flame impinging on one face of a flat 3-mm-thick stainless steel plate, keeping Reynolds number of the gas mixture 1000 and dimensionless burner tip to impinging plate distance equals to 4, while maintaining the equivalence ratio one. Inclusion of both radiation and convection losses in the Green’s function solution for the forward problem enhances the accuracy in the forward model, thereby increasing the possibility of estimating the parameters with better accuracy. The results are found to be in good agreement with the literature. This methodology is independent of flow and heating conditions, and can be applied even to high-temperature applications. © 2020, Akadémiai Kiadó, Budapest, Hungary.Item Studies on application of vertical axis hydro turbine for sustainable power generation in irrigation channels with different bed slopes(Elsevier Ltd, 2021) Shashikumar, S.; Honnasiddaiah, R.; Hindasageri, V.; Madav, V.The present work is carried out to study the performance of a Savonius rotor for small-scale hydropower generation. It has been observed that some of the irrigation channels available in the rural areas are having enough bed slope to generate kinetic energy, which can be harnessed through a Savonius rotor. An in-house fabricated scale-down model of the Savonius rotor is tested at an inclination of the re-circulating indoor multipurpose tilting flume at 0°, 0.5°, 1.0°, 1.5° and 2.0° to determine performance under controlled conditions. It is observed that at the tip speed ratio of 0.92 and channel inclination of 0.5° compared to 0° inclination, the coefficient of power and coefficient of torque improved to 40% and 10%, respectively. Furthermore, it is found that the torque and power developed by the turbine are maximum at a bed slope of 2.0° owing to the maximum available energy. © 2020 Elsevier LtdItem Numerical investigation of conventional and tapered Savonius hydrokinetic turbines for low-velocity hydropower application in an irrigation channel(Elsevier Ltd, 2021) Shashikumar, S.; Vijaykumar, H.; Madav, V.In the present work, computational fluid dynamics simulation was carried out using ANSYS Fluent to study the performance of conventional and tapered turbine blades for hydrokinetic power generation. The sliding mesh technique is used to study the influence of taper on conventional Savonius turbine using the SST k-? turbulence model and performance parameters were determined. The geometric parameters used in the present simulation for conventional and tapered turbine blades are aspect ratio and overlap ratio of 1.0 and 0.0. The inlet velocity and depth of water used for present simulation are 0.5 m/s and 103.6 mm for both conventional and tapered turbine blades. The results show that a 5% increase in the performance of a conventional turbine as compare to tapered turbine blade with a taper angle of 5°. The value of maximum coefficient of power for conventional Savonius turbine blade is 0.21 with a tip speed ratio 0.9. The flow field around the conventional and tapered turbine blades at different angular positions are analysed. It was found that there is a loss of energy at the exit side of the advancing blade for the case of tapered turbine, that leads to 5% reduction of performance as compared to the conventional turbine. © 2020 Elsevier LtdItem Liquid fuel from waste tires: novel refining, advanced characterization and utilization in engines with ethyl levulinate as an additive(Royal Society of Chemistry, 2021) Mohan, A.; Dutta, S.; Saravanan, S.; Madav, V.Pyrolysis is a promising thermochemical strategy to convert scrap tires into diesel-like fuels. Crude tire pyrolysis oil (CTPO) was produced in a 10 ton rotating autoclave reactor by thermal depolymerization of the tire polymers. In this work, the prior-reported straightforward and inexpensive strategy of upgrading CTPO using a combination of silica gel (as adsorbent) and petroleum ether (as the solvent) has been scaled up with minimal loss in mass of oil and improved physicochemical characteristics (e.g., lowered acid value, low sulfur content). The upgraded TPO (StTPO) was characterized extensively to better understand their chemical compositions, physicochemical properties, and combustion characteristics. StTPO was mixed with diesel in different volumetric proportions and the blends were studied for performance and emission characteristics in a single-cylinder engine. The use of biomass-derived ethyl levulinate (EL) as a fuel oxygenate improved the cold-flow properties of StTPO-diesel blends as well as lowered the exhaust emissions (e.g., lower NOx). A fuel blend consisting of 50% diesel, 40% StTPO, and 10% EL demonstrated the best fuel properties in the single-cylinder diesel engine. © The Royal Society of Chemistry 2021.Item Experimental and numerical investigation of novel V-shaped rotor for hydropower utilization(Elsevier Ltd, 2021) Shashikumar, S.; Honnasiddaiah, R.; Hindasageri, V.; Madav, V.Hydrokinetic technologies harvest renewable power by harnessing the kinetic energy of water from free-flowing rivers, streams, dam head/tailrace and irrigation channels. Savonius rotor is one of the simple and low-cost vertical axis drag type devices used for the extraction of hydrokinetic power. The main limitation of Savonius hydrokinetic turbine is its low efficiency due to negative torque developed by the returning blade without augmentation techniques. In this paper, an experimental investigation is carried out in a multipurpose tilting water flume using V-shaped rotor blade profiles by maintaining a fixed V-angle of 90°, varying length of V-edges, arc radius and with a constant aspect ratio of 0.7. The simulations were carried out using commercial software, ANSYS Fluent. From the experimental and numerical results, it was found that, the optimum blade profile (V4) has developed a maximum coefficient of power 0.22 and 0.21 respectively, at a tip speed ratio 0.87. It was found that, the maximum coefficient of power of optimal V-shaped blade profile (V4) is 19.3% higher than the semi-circular blade profile. © 2021 Elsevier LtdItem Heat transfer characterisation of impinging flame jet over a wedge(Elsevier Ltd, 2021) Parida, R.K.; Kadam, A.R.; Madav, V.; Hindasageri, V.This paper aims to estimate two unknown parameters - Nusselt number and effectiveness – analytically and study the heat transfer characteristics of impinging flame jet over a wedge-shaped structure similar to a missile deflector plate. Experimentally obtained raw transient temperature history at the non-impinging face of a 4-mm-thick test object made of stainless steel is the only input data. An analytical Inverse Heat Conduction Technique based on Green's Function Approach is employed to estimate both parameters simultaneously. Multiple experimental cases are considered in this work by varying methane-air gas mixture Reynolds number (800, 1000, 1200, and 1500), non-dimensional nozzle tip to test object distance (2, 4, and 6), and wedge-angle (90° and 120°). The observations concerning heat transfer characteristics of the impinging flame jet are discussed in detail. The flame jet's heating effect has been observed to improve as the wedge angle is increased from 90° to 120°. Uncertainty of the estimated parameters is evaluated using the Monte Carlo technique. © 2021
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