Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884
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Item Effect of preheated mixture on heat transfer characteristics of impinging methane-air premixed flame jet(Elsevier Ltd, 2015) Tajik, A.R.; Kuntikana, P.; Prabhu, S.V.; Hindasageri, V.Energy from spent flame or other low grade energy can be used to increase the temperature of the air before mixing with fuel. This would improve the heat transfer characteristics of the impinging flame jet. The studies on impinging flame jets reported in the literature are based on the fuel-air mixture at ambient temperature. In the present work, the inlet air for mixture is heated by an electrical heater. The heat flux distribution is estimated using an inverse heat conduction (IHCP) technique. The Nusselt number (Nu) and effectiveness (?) distributions are obtained by estimating the adiabatic wall temperature (Taw) by the analytical-numerical method. A circular burner of 13.5 mm is used for impingement on quartz plate of 3 mm thickness. Reynolds number (Re) varying from 500 to 2000 for the non-dimensional burner tip to impingement plate spacing (Z/d) of 2-6 and stoichiometric condition (Ø = 1.0) is considered for varying preheated condition. The effect of equivalence ratio is studied for Ø = 0.75 to 1.5 for Re = 1000 and Z/d = 4. By increase in preheat temperature, the stagnation point heat flux increases from 20% to 50% unless the inner premixed zone touches the impingement plate. CFD simulations are carried out in FLUENT software to explain the distribution of heat flux. © 2015 Elsevier Ltd. All rights reserved.Item A numerical investigation on heat transfer and emissions characteristics of impinging radial jet reattachment combustion (RJRC) flame(Elsevier Ltd, 2015) Tajik, A.R.; Hindasageri, V.Radial Jet Reattachment combustion (RJRC) flame jet is used in applications where the impingement surface is delicate and demands low impingement pressure. In the present study, a two dimensional axisymmetric computational fluid dynamics (CFD) simulation is carried out. The turbulence-combustion interaction in the flame field is modeled in a k-?/EDM framework. The distribution of heat flux, pressure coefficient and emissions is presented for varying Reynolds number (Re = 1000 to 30,000) and different non-dimensional nozzle tip to plate spacing (X/R = 0.5 to 3). It is found that the peak heat flux increases and pressure coefficient reduces significantly with the increase in Reynolds number. However, with the increase in the nozzle tip to plate spacing the peak heat flux and the pressure coefficient decrease. Furthermore, the concentrations of NOx and CO emissions increase with the increase in Reynolds number and the distance of the location of the nozzle tip from the impingement plate. © 2015 Elsevier Ltd. All rights reserved.Item Heat transfer distribution of impinging flame and air jets - A comparative study(Elsevier Ltd, 2016) Kadam, A.R.; Tajik, A.R.; Hindasageri, V.Heat transfer distribution of impinging flame jet is compared with that of the impinging air jet based on the experimental data reported in literature for methane-air flame jet and air jet impingement for Reynolds number, R=600-1400 and the non-dimensional nozzle tip to impingement plate distance, Z/d=2-6. The comparative data based on mapping experimental data reported in literature suggest that there is a good agreement between the Nusselt numbers for higher Z/d near stagnation region. However, away from the stagnation region, the Nusselt number for flame jet is higher than that of air jet for similar operating conditions of Re and Z/d. A CFD simulation for impinging air jet and impinging flame jet is carried out to explain the physics and reason for the deviations observed in experimental data. A scale analysis is carried out to identify the dominant forces and their influence on the heat transfer distribution on the impingement plate. © 2015 Elsevier Ltd. All rights reserved.Item Local heat transfer distribution on a flat plate impinged by a swirling jet generated by a twisted tape(Elsevier Masson SAS 62 rue Camille Desmoulins Issy les Moulineaux Cedex 92442, 2017) Kumar, S.S.; Hindasageri, V.; Prabhu, S.V.An experimental investigation is conducted to study the local heat transfer distribution on a flat surface normally impinged by a swirling air jet. Twisted tapes of twist ratios equal to 2, 3.2, 4.5 and 7.5 (corresponding swirl numbers S = 0.79, 0.49, 0.35, 0.21) are inserted in a circular tube to generate swirling effect. Experiments are carried out for Reynolds number varying from 500 to 3000 for jet to plate spacing varying from 1 to 4. The local heat transfer characteristics are estimated using thermal images obtained by thermal infrared imaging technique. The jet flow profile on the target plate is evaluated by the flow visualisation carried out using lamp black technique. The heat transfer rate is found to initially increase with the increase in twist ratio (or decrease in swirl number) from 2 to 4.5 and thereafter it reduces with the increase in the twist ratio from 4.5 to 7.5. The heat transfer rate is maximum for a twist ratio of 4.5 and minimum for a twist ratio of 7.5. The jet to plate spacing also shows strong influence on the heat transfer rate. With the increase in jet to plate spacing, the heat transfer rate decreases. The maximum heat transfer rate is obtained at z/d = 1 for the different twist ratios and Reynolds number. © 2016 Elsevier Masson SASItem An experimental and numerical study on effects of exhaust gas temperature and flow rate on deposit formation in Urea-Selective Catalytic Reduction (SCR) system of modern automobiles(Elsevier Ltd, 2017) Prabhu S, S.; Nayak, N.S.; Kapilan, N.; Hindasageri, V.Urea Water Solution (UWS) is injected to generate NH3 in Selective Catalytic Reduction (SCR) system of modern automobiles. Thermal and fluid dynamic conditions such as temperature and Reynolds number of the flow favors ammonia generation in terms of heat transfer to UWS droplets by forced convection. During extremely cold weather conditions and low exhaust temperatures, the overdosing of UWS results in deposits of urea and its byproducts. As deposit depletion changes the stoichiometry of NOx/NH3, any predictive method becomes complementary to experimental studies on deposit formation. In the present work, we experimentally investigated deposit formation and its rate by a newer concept of usage of Stainless Steel (SS) foils considering temperature and flow rate as variables. According to numerical results, the droplet evaporation of UWS decreases as flow rate increases. For a fixed rate of UWS quantity of deposits decrease with increase in temperature and flow rate. Accordingly, structural changes are observed. Numerical values of time dependent deposit formation found slightly superior to the experimental values. The study revealed that deposit areas at low temperatures are comparable to numerical values. Phenomenological model is proposed to find deposit conversion factor for low temperatures (150–250°C), which helps in tuning of UWS dosage strategy to prevent NH3 slip. © 2016 Elsevier Ltd