Dr. Ratna Kishore V. received his Ph. D. in Mechanical engineering from Indian Institute of Technology, Delhi (IITD) in 2010. His dissertation was titled, Experimental and Computational Investigations on Open Laminar Flames of Multi-Component Gaseous Fuel Mixtures. The objective of this research is to study the laminar burning velocity using Heat Flux Method, effect of stretch diffusive-thermal instability of multi-component fuel mixtures burning in air (21% O2 & 79% N2 by volume). The work also involves flames simulations for 2D slot burners and 3D flat flame burner using FLUENT. Dr. Ratna Kishore has published 5 research articles in international journals and 5 at international conferences.

His current areas of research are: Premixed Combustion for Multi-components Mixtures (for ex. Propane + hydrogen), High Temperature Natural Convection Flows and Flow through industrial valves.

Education

YEAR

DEGREE

INSTITUTION

2002

B. Tech., Mechanical Engineering

National Institute of Technology, Surathkal

2004

M. Tech., Thermal Engineering

Indian Institute of Technology, Delhi

2013

Ph. D., Mechanical Engineering

Indian Institute of Technology, Delhi

Employment Record

Teaching Assistant: IIT Delhi, New Delhi, India, August 2002 to May 2010

Assistant Professor: Department of Mechanical Engineering, Amrita Vishwa Vidyapeetham, Coimbatore. Jan 2011 - Present

Reviewer in Journals/ Conferences

Dr. Ratna Kishore V involved in the reviewing of research papers/ articles as follows

International Journal of Hydrogen Energy

Energy, An international Journal

International Journal of Thermal Sciences

IMECHE, Journal of Aerospace Engineering, Part G

Renewable and Sustainable Energy Reviews

International Journal of Renewable Energy Research

Journal of Nanomaterials

COURSE HANDLED - THEORY

UG Level

PG Level

Gas Dynamics and Jet Propulsion

Design of Thermal Systems

Advanced Fluid Mechanics

Heat Transfer

Computational Fluid Dynamics

Applied Mathematics

Thermodynamics

Fluid Mechanics and Machinery

Publications

Publication Type: Journal Article

Year of Publication

Publication Type

Title

2016

Journal Article

A. Nair, Kishore, V. R., and Kumar, S., “Effect OF CO2/N2 dilution on laminar burning velocity of liquid petroleum gas-air mixtures at elevated temperatures”, Energy, vol. 100, pp. 145-153, 2016.[Abstract]

Ba Aravind, Kishore, V. R., Singh, A. Pa, Yoon, Yc, Minaev, Sd, and Kumar, Sa, “Investigations on flame dynamics of premixed H2-air mixtures in microscale tubes”, RSC Advances, vol. 6, pp. 50358-50367, 2016.[Abstract]

E. J. Veetil, Rajith, C. V., and Kishore, V. R., “Numerical simulations of steady perforated-plate stabilized Syngas air pre-mixed flames”, International Journal of Hydrogen Energy, 2016.[Abstract]

Numerical investigations of steady, laminar premixed Syngas-air flames are presented in this paper. Three-dimensional simulations were performed to examine the impact of operating conditions on steady state characteristics of perforated burner flame. A detailed H2 CO reaction mechanism having 12 species and 38 reactions was used for combustion modelling. The three dimensional simulation results are validated against the 1D flat flame result using PREMIX. Effects of inlet velocity, fuel composition and equivalence ratio on flame stability were examined. A clearly identified recirculation zone was present above the top surface of the burner plate in the case of 50% H2-50% CO Syngas mixture. The strength recirculation zone was diminishing with the increase in percentage of hydrogen in the Syngas mixture, and the flame has stabilized closer to the top surface of the burner plate. The flame stand-off distance is found to decrease with increase in inlet velocity. Effect of increase in H2 fraction in Syngas has less effect on flame height at higher H2 fractions.
More »»

2015

Journal Article

V. R. Kishore, Vivek, M., Goutham, K., Sreekanth, G. R., Dharmarajan, S., and Goel, M., “Numerical study of a buoyant plume from a multi-flue stack into a variable temperature gradient atmosphere”, Environmental Science and Pollution Research, vol. 22, pp. 16814–16829, 2015.[Abstract]

Air pollution is one of the major global hazards and industries have been one of its major contributors. This paper primarily focuses on analyzing the dispersion characteristics of buoyant plumes of the pollutant released from a multi-flue vertical stack into a variable temperature gradient atmosphere (α) in a constant-velocity cross wind using two stack configurations—inline and parallel. The study is conducted for different Froude numbers, Fr = 12.64, 9.55, and 8.27. The atmospheric temperature gradients considered for the study are 0, +1, +1.5, and +2 K/100 m. The numerical study is done using the commercial computational fluid dynamics (CFD) code FLUENT. The effects of stack configuration, α, and Fr on the plume characteristics are presented. It is observed that the plume rises higher and disperses over a larger area with the inline configuration due to better mixing and shielding effect. With higher α, it is seen that the plume rises initially and then descends due to variation of the buoyant force. The plume rise initially is strongly influenced by the momentum of the jet, and as it moves downstream, it is influenced by the cooling rate of the plume. Furthermore, the plume rises higher and disperses over a larger area with a decrease in Fr.

V. R. Kishore, Arun, J., Padmanabhan, R., and V, B., “Parametric studies of dissimilar friction stir welding using computational fluid dynamics simulation”, International Journal of Advanced Manufacturing Technology, vol. 80, pp. 91-98, 2015.[Abstract]

Aa Nair, Kishore, V. R., and Kumar, Sb, “Dynamics of Premixed Hydrogen-Air Flames in Microchannels with a Wall Temperature Gradient”, Combustion Science and Technology, vol. 187, pp. 1620-1637, 2015.[Abstract]

B. M. M. S. R. S., Kishore, V. R., S. P. Anbuudayasankar, and Balaji, K., “Power generation by high head water in a building using micro hydro turbine—a greener approach”, Environmental Science and Pollution Research, 2015.[Abstract]

S. A.P., Kishore, V. R., S., M., and S., K., “Numerical investigations of unsteady flame propagation in stepped microtubes”, RSC Advances, vol. 5, pp. 100879-100890, 2015.[Abstract]

B. Aravind, Kishore, V. R., and Mohammad, A., “Combustion characteristics of the effect of hydrogen addition on LPG–air mixtures”, International Journal of Hydrogen Energy, vol. 40, pp. 16605–16617, 2015.[Abstract]

The present study reports the effect of hydrogen addition on combustion characteristics of LPG–air mixtures for different mixture compositions, temperatures and pressures. Numerical simulation has been carried out using USC Mech II reaction mechanism, consisting of 111 species and 784 reactions. It is found that, variation of the flame speeds were relatively small for various compositions of LPG–air mixtures used. Thus 50% propane – 50% butane mixture is considered for the present work. The effect of volumetric H2 addition on laminar flame speed and ignition delay of selected LPG (50% propane + 50% butane) air mixtures is then studied for hydrogen addition ratio varying from 0 < RH < 0.5 and over a wide range of mixture equivalence ratio. Also, the investigation is carried out for mixture temperature up to 450 K and pressure ranging from 1 to 10 bar. A parabolic variation of laminar flame speed is observed with equivalence ratios giving peak value for slightly rich mixture. A linear correlation has been observed for the flame speed as a function of hydrogen addition, RH at all the conditions studied. Whereas, power law correlation has been proposed for the hydrogen added LPG–air mixture, to understand the dependency of laminar flame speed on temperature and pressure. A generic correlation has been proposed to study the combined effect of temperature and pressure on laminar flame speed.

E. V. Jithin, Kishore, V. R., and Varghese, R. J., “Three-dimensional simulations of steady perforated-plate stabilized propane-air premixed flames”, Energy and Fuels, vol. 28, pp. 5415-5425, 2014.[Abstract]

R. Padmanaban, Kishore, V. R., and Balusamy, V., “Numerical Simulation of Temperature Distribution and Material Flow During Friction Stir Welding of Dissimilar Aluminum Alloys”, Procedia Engineering, vol. 97, pp. 854–863, 2014.[Abstract]

Joining dissimilar materials is required in many engineering applications and conventional fusion welding of dissimilar materials often results in defective welds. Friction Stir Welding (FSW) has paved way for joining dissimilar alloys and defect-free joints have been obtained for a number of dissimilar material combinations. Numerical modelling of FSW process can provide reasonable insight into the physics of the process and will aid in minimising the number of experimental trials. In this paper, Computational Fluid Dynamics (CFD) based numerical model is developed to predict the temperature distribution and material flow during FSW of dissimilar aluminum alloys AA2024 and AA7075. Volume of fluid approach is used and the FSW process is modelled as a steady-state visco-plastic laminar flow past a rotating cylindrical tool. Results indicate that peak temperature in the welded plates increases with the increase of Tool Rotation Speed (TRS) and Shoulder Diameter (SD), whereas the peak temperature decreases with increase in Welding Speed (WS). Increasing TRS and SD increases material flow, while increasing WS decreases material flow in the stir zone.

S. Chandramouli, Premsai, T. P., Prithviraj, P., Mugundhan, V., and Kishore, V. R., “Numerical analysis of effect of pitch angle on a small scale vertical axis wind turbine”, International Journal of Renewable Energy Research (IJRER), vol. 4, pp. 929–935, 2014.[Abstract]

The current work involves a numerical study of the effect of preset pitch angle on the performance of a Vertical Axis Wind Turbine (VAWT). A three bladed H-Darrieus VAWT has been considered for the study. The equations governing the flow are solved using a commercial CFD code ANSYS CFX 13. The turbine with NACA 0015 profile and zero pitch angle as the reference case for comparison. The analysis has been done for three pitch angles -6o, 0o, +6o, tip speed ratios (TSR) from 1 to 2.2 and wind velocities of 6, 8 and 10 m/s. Of the pitch angle considered, the best performance is observed with -6o for all tip speed ratios and wind velocities. This has been explained by studying the instantaneous torque characteristics of the turbine. It is seen that at any given instant, the blade in the upwind region contributes significantly to the positive torque with other blades either contributing less or negating the positive torque. The pressure coefficient distributions over the upwind blade and stream lines at different azimuthal angles have also been analysed to understand the effect of pitch.

R. Abhinav, Sunder, P. B. S., Gowrishankar, A., Vignesh, S., Vivek, M., and Kishore, V. R., “Numerical study on effect of vent locations on natural convection in an enclosure with an internal heat source”, International Communications in Heat and Mass Transfer, vol. 49, pp. 69-77, 2013.[Abstract]

M. K. Lalith, Dinesh, A., Unnikrishnan, S., Radhakrishnan, A., Srihari, S., and Kishore, V. R., “Modeling of homogeneous mixture formation and combustion in GDI engine with negative valve overlap”, ISRN Mechanical Engineering, vol. 12, no. 1, 2013.[Abstract]

Ma Akram, Kishore, V. R., and Kumar, Sa, “Laminar burning velocity of propane/CO 2/N 2-air mixtures at elevated temperatures”, Energy and Fuels, vol. 26, pp. 5509-5518, 2012.[Abstract]

Ra Padmanaban, Balusamy, Vb, and Kishore, V. R., “Effect of axial pressure and tool rotation speed on temperature distribution during dissimilar friction stir welding”, Advanced Materials Research, vol. 418-420, pp. 1934-1938, 2012.[Abstract]

V. R. Kishore, Ravi, M. R., and Ray, A., “Adiabatic burning velocity and cellular flame characteristics of H 2–CO–CO 2–air mixtures”, Combustion and Flame, vol. 158, pp. 2149–2164, 2011.[Abstract]

The objective of this work was to study the effect of dilution with carbon dioxide on the adiabatic burning velocity of syngas fuel (with various H2/CO ratios)-air(21% O2–79% N2 by volume) mixtures along with detailed understanding of cellular flame structures. Heat flux method with a setup similar to that of de Goey and co-workers [1] was used for measurement of burning velocities. Validation experiments were done for H2 (5%)–CO (95%)–air and H2 (5%)–CO (45%)–CO2 (50%)–air mixtures at various equivalence ratios and the results were in good agreement with published data in the literature. The mixtures considered in this work had 1:4, 1:1 and 4:1 H2/CO ratio in the fuel and 40%, 50% and 60% CO2 dilution. The burning velocity increased significantly with the increase in H2 content in mixture of H2–CO with fixed CO2 dilution. The burning velocity reduced remarkably with carbon dioxide dilution in H2–CO mixture due to reduction in heat release, flame temperature and thermal diffusivity of the mixture. The location of peak adiabatic burning velocity shifted from ϕ = 1.6 for 40% CO2 to ϕ = 1.2 for 60% CO2, whereas it remained unchanged with variation of H2:CO ratio (4:1, 1:1 and 1:4) at a given CO2 dilution. A comparison of experiments and simulations indicated that the Davis et al. [2] mechanism predicted burning velocities well for the most of experimental operating conditions except for rich conditions. For some lean mixtures, flames exhibited cellular structures. In order to explain the structures and generate profiles of various field variables of interest, computations of three dimensional porous burner stabilized cellular flames were performed using commercial CFD software FLUENT. Simulations for lean H2 (25%)–CO (25%)–CO2 (50%)–air mixtures (ϕ = 0.6 and 0.8) produced cellular flame structures very similar to those observed in the experiments. It was found that the in the core region of a typical cell, stretch rate was positive, the volumetric heat release rate was high and the net reaction rate for the reaction O + H2 ⇄ H + OH and the net consumption rate of H2 were both high.

V. R. Kishore, Muchahary, R., Ray, A., and Ravi, M. R., “Adiabatic burning velocity of H 2–O 2 mixtures diluted with CO 2/N 2/Ar”, international journal of hydrogen energy, vol. 34, pp. 8378–8388, 2009.[Abstract]

Global warming due to CO2 emissions has led to the projection of hydrogen as an important fuel for future. A lot of research has been going on to design combustion appliances for hydrogen as fuel. This has necessitated fundamental research on combustion characteristics of hydrogen fuel. In this work, a combination of experiments and computational simulations was employed to study the effects of diluents (CO2, N2, and Ar) on the laminar burning velocity of premixed hydrogen/oxygen flames using the heat flux method. The experiments were conducted to measure laminar burning velocity for a range of equivalence ratios at atmospheric pressure and temperature (300 K) with reactant mixtures containing varying concentrations of CO2, N2, and Ar as diluents. Measured burning velocities were compared with computed results obtained from one-dimensional laminar premixed flame code PREMIX with detailed chemical kinetics and good agreement was obtained. The effectiveness of diluents in reduction of laminar burning velocity for a given diluent concentration is in the increasing order of argon, nitrogen, carbon dioxide. This may be due to increased capabilities either to quench the reaction zone by increased specific heat or due to reduced transport rates. The lean and stoichiometric H2/O2/CO2 flames with 65% CO2 dilution exhibited cellular flame structures. Detailed three-dimensional simulation was performed to understand lean H2/O2/CO2 cellular flame structure and cell count from computed flame matched well with the experimental cellular flame.

P. Parthasarathy, Talukdar, P., and Kishore, V. R., “Enhancement of heat transfer with porous/solid insert for laminar flow of a participating gas in a 3-D square duct”, Numerical Heat Transfer, Part A: Applications, vol. 56, pp. 764–784, 2009.[Abstract]

In recent years, porous or solid insert has been used in a duct for enhancing heat transfer in high temperature thermal equipment, where both convective and radiative heat transfer play a major role. In the present work, the study of heat transfer enhancement is carried out for flow through a square duct with a porous or a solid insert. Most of the analyses are carried out for a porous insert. The hydrodynamically developing flow field is solved using the Navier–Stokes equation and the Darcy–Brinkman model is considered for solving the flow in the porous region. The radiative heat transfer is included in the analysis by coupling the radiative transfer equation to the energy equation. The fluid considered is CO2 with temperature dependent thermophysical properties. Both the fluid and the porous medium are considered as gray participating medium. The increase in heat transfer is analyzed by comparing the bulk mean temperature, Nusselt number, and radiative heat flux for different porous size and orientation, Reyonlds number, and Darcy number.

V. R. Kishore, Ravi, M. R., and Ray, A., “Effect of hydrogen content and dilution on laminar burning velocity and stability characteristics of producer gas-air mixtures”, Journal of Combustion, vol. 2008, 2008.[Abstract]

Producer gas is one of the promising alternative fuels with typical constituents of H2, CO, CH4, N2, and CO2. The laminar burning velocity of producer gas was computed for a wide range of operating conditions. Flame stability due to preferential diffusional effects was also investigated. Computations were carried out for spherical outwardly propagating flames and planar flames. Different reaction mechanisms were assessed for the prediction of laminar burning velocities of CH4, H2, H2-CO, and CO-CH4 and results showed that the Warnatz reaction mechanism with C1 chemistry was the smallest among the tested mechanisms with reasonably accurate predictions for all fuels at 1 bar, 300 K. To study the effect of variation in the producer gas composition, each of the fuel constituents in ternary CH4-H2-CO mixtures was varied between 0 to 48%, while keeping diluents fixed at 10% CO2 and 42% N2 by volume. Peak burning velocity shifted from to 1.1 as the combined volumetric percentage of hydrogen and CO varied from 48% to 0%. Unstable flames due to preferential diffusion effects were observed for lean mixtures of fuel with high hydrogen content. The present results indicate that H2 has a strong influence on the combustion of producer gas.
More »»

2008

Journal Article

V. R. Kishore, Duhan, N., Ravi, M. R., and Ray, A., “Measurement of adiabatic burning velocity in natural gas-like mixtures”, Experimental Thermal and Fluid Science, vol. 33, pp. 10–16, 2008.[Abstract]

Experimental measurements of the adiabatic burning velocities were carried out for natural gas-like mixtures burning in air over a range of equivalence ratios at atmospheric pressure. Effect of CO2 dilution up to 60%, N2 dilution up to 40% and 25% enrichment of ethane on burning velocity of methane–air flames were studied. Heat flux method with setup similar to that of [K.J. Bosschaart, L.P.H. de Goey, Detailed analysis of the heat flux method for measuring burning velocity, Combustion and Flame 132 (2003) 170–180] was used for measurement of burning velocities. Initially experiments were done for methane–air and ethane–air mixtures at various equivalence ratios and the results were in good agreement with published data in the literature. Computations were performed using PREMIX code with GRI 3.0 reaction mechanism for all the mixtures. Predicted flame structures were used to the explain the effect of N2 and CO2 dilution on burning velocity of methane–air flames. Peak burning velocity for CH4/CO2–air mixtures occur near to ϕ = 1.0.

Dr. Ratna Kishore V. received his Ph. D. in Mechanical engineering from Indian Institute of Technology, Delhi (IITD) in 2010. His dissertation was titled, Experimental and Computational Investigations on Open Laminar Flames of Multi-Component Gaseous Fuel Mixtures. The objective of this research is to study the laminar burning velocity using Heat Flux Method, effect of stretch diffusive-thermal instability of multi-component fuel mixtures burning in air (21% O2 & 79% N2 by volume). The work also involves flames simulations for 2D slot burners and 3D flat flame burner using FLUENT. Dr. Ratna Kishore has published 5 research articles in international journals and 5 at international conferences.

His current areas of research are: Premixed Combustion for Multi-components Mixtures (for ex. Propane + hydrogen), High Temperature Natural Convection Flows and Flow through industrial valves.

## Education

YEARDEGREEINSTITUTION## Employment Record

Teaching Assistant: IIT Delhi, New Delhi, India, August 2002 to May 2010Assistant Professor: Department of Mechanical Engineering, Amrita Vishwa Vidyapeetham, Coimbatore. Jan 2011 - Present## Reviewer in Journals/ Conferences

Dr. Ratna Kishore V involved in the reviewing of research papers/ articles as follows

## COURSE HANDLED - THEORY

UG LevelPG Level## Publications

The present experimental study reports the effect of CO2/N2 dilution on laminar burning velocity of premixed LPG (liquid-petroleum-gas)-air mixtures at elevated temperatures using a preheated mesoscale diverging channel technique. The experiments were carried out for a range of equivalence ratios varying from 0.8 < Φ < 1.3 with percentage dilution of the fuel component by volume (β) for CO2 varying from 10% < β < 30% and N2 varying from 10% < β < 40%. A power-law correlation has been obtained for the present experimental data as a function of percentage dilution, mixture temperature and equivalence ratio. It has been observed that an increase in dilution with CO2/N2 leads to an increase in temperature exponent (α). The increase in temperature exponent due to CO2 dilution is more pronounced as compared to N2 dilution case. A flame structure study has been carried out to understand the effect of mixture temperature and diluent using USC (University of Southern California) Mech II reaction mechanism. © 2016 Elsevier Ltd. More »»

Detailed numerical studies through unsteady simulations with detailed hydrogen chemistry have been reported for premixed H2-air flames in straight microtubes to understand the role of flame-wall coupling and its effect on flame dynamics for a range of wall heat transfer conditions. Depending on the wall heat transfer conditions, and tube diameters, varying flame shapes were observed. These flame modes are represented with flame shape angles and corresponding flame shape is correlated to wall heat transfer conditions. It has been observed that an increase in wall heat transfer coefficient, h, though it increases the heat loss from a propagating flame, does not necessarily lead to a monotonic decrease in flame propagation speed. A transition regime, where the propagating flame changes its shape, has been identified. The variation of mass flux in the vicinity of the propagating flame has been used to gain a better understanding of flow-redirection and its impact on flame shape and flame propagation speed for premixed H2-air mixtures. © 2016 The Royal Society of Chemistry. More »»

Numerical investigations of steady, laminar premixed Syngas-air flames are presented in this paper. Three-dimensional simulations were performed to examine the impact of operating conditions on steady state characteristics of perforated burner flame. A detailed H2 CO reaction mechanism having 12 species and 38 reactions was used for combustion modelling. The three dimensional simulation results are validated against the 1D flat flame result using PREMIX. Effects of inlet velocity, fuel composition and equivalence ratio on flame stability were examined. A clearly identified recirculation zone was present above the top surface of the burner plate in the case of 50% H2-50% CO Syngas mixture. The strength recirculation zone was diminishing with the increase in percentage of hydrogen in the Syngas mixture, and the flame has stabilized closer to the top surface of the burner plate. The flame stand-off distance is found to decrease with increase in inlet velocity. Effect of increase in H2 fraction in Syngas has less effect on flame height at higher H2 fractions. More »»

Air pollution is one of the major global hazards and industries have been one of its major contributors. This paper primarily focuses on analyzing the dispersion characteristics of buoyant plumes of the pollutant released from a multi-flue vertical stack into a variable temperature gradient atmosphere (α) in a constant-velocity cross wind using two stack configurations—inline and parallel. The study is conducted for different Froude numbers, Fr = 12.64, 9.55, and 8.27. The atmospheric temperature gradients considered for the study are 0, +1, +1.5, and +2 K/100 m. The numerical study is done using the commercial computational fluid dynamics (CFD) code FLUENT. The effects of stack configuration, α, and Fr on the plume characteristics are presented. It is observed that the plume rises higher and disperses over a larger area with the inline configuration due to better mixing and shielding effect. With higher α, it is seen that the plume rises initially and then descends due to variation of the buoyant force. The plume rise initially is strongly influenced by the momentum of the jet, and as it moves downstream, it is influenced by the cooling rate of the plume. Furthermore, the plume rises higher and disperses over a larger area with a decrease in Fr.

More »»A two-dimensional steady state visco-plastic model has been developed for friction stir welding of dissimilar metals using a commercial CFD code, FLUENT®. Volume of Fluid (VOF) approach is used to model the welding process of dissimilar metals. Initially, the model developed is validated against experimental measurements of Peel et al. (Metall Mater Trans A 37 A:2183–2193, 2006). Simulations were done for two different material combinations, AA 5083–AA 6061 and AA 2024–AA 7075. The temperature distribution and material flow around the tool is studied for different position of materials, process parameters, and tool profiles. It is seen that the peak temperature is generated on harder material side with change in position of materials. This is mainly because on harder material side more heat is generated due to viscous dissipation. The trivex pin profile is found to be better than circular pin profile by reducing welding traverse force and an efficient symmetric mixing of materials. © 2015, Springer-Verlag London.

More »»Two-dimensional numerical investigations on flame dynamics in a microchannel have been carried out for premixed hydrogen-air mixtures with detailed chemistry. Detailed studies on the formation of flames with repetitive extinction and ignition (FREI) mode have been carried out for a 0.75-mm diameter tube with fixed conditions of flow velocity of 10 cm/s and Φ = 0.5-1.0 with wall temperature linearly varying from 300 K to 960 K. An unsteady flame propagation behavior similar to FREI has been observed to appear for a range of mixture equivalence ratios and channel diameters. FREI was observed to occur for 0.5 < 0.8 for 0.75-mm diameter channel and disappears for higher mixture equivalence ratios. The effect of tube diameter has also been analyzed for 10 cm/s inlet velocity of mixture at 300-1050 K wall temperature for diameters of 0.6 mm, 0.75 mm, and 1.0 mm. As the tube diameter increased, the frequency of the FREI process decreased, which hints to the contribution of disappearance of FREI phenomenon. © Taylor & Francis Group, LLC.

More »»Demand for green energy production is arising all over the world. A lot of emphasis is laid in making the buildings green. Even a small amount of energy savings made contribute to saving the environment. In this study, an idea is proposed and studied to extract power from the high head water in the pipelines of a building. A building of height 15 m is considered for this study. Water flowing in the pipe has sufficient energy to run a micro hydro turbine. The feasibility of producing electrical energy from the energy of pipe water is found. The motivation is to find the feasibility of generating power using a low-cost turbine. The experimental setup consists of micro turbine of 135 mm diameter coupled to a 12-V DC generator; LEDs and resistors are employed to validate the results. The theoretical calculations were presented using the fundamental equations of fluid mechanics. The theoretical results are validated using experimental and numerical results using CFD simulation. In addition, exergy analysis has been carried out to quantify the irreversibilities during the process in the system. © 2015 Springer-Verlag Berlin Heidelberg

More »»Transient numerical simulations with detailed chemistry have been carried out for premixed stoichiometric CH4-air and H2-air flames in two-dimensional stepped microtubes for a range of wall heat transfer conditions. Investigations on such configurations are important from the perspective of the design of micro combustion devices, flame arresters and safety in domestic and industrial combustion devices. Similarities in flame propagation characteristics have been brought out through a detailed analysis for both the fuels. Detailed analysis of the propagating flame near the channel step revealed an interesting phenomenon of sudden increase in flame propagation velocities for a certain range of wall heat transfer coefficient, h. A quantitative value of ratio of heat-loss to heat-generation at the contraction has been proposed which helps predict the flame propagation through sudden channel steps. © The Royal Society of Chemistry 2015.

More »»The present study reports the effect of hydrogen addition on combustion characteristics of LPG–air mixtures for different mixture compositions, temperatures and pressures. Numerical simulation has been carried out using USC Mech II reaction mechanism, consisting of 111 species and 784 reactions. It is found that, variation of the flame speeds were relatively small for various compositions of LPG–air mixtures used. Thus 50% propane – 50% butane mixture is considered for the present work. The effect of volumetric H2 addition on laminar flame speed and ignition delay of selected LPG (50% propane + 50% butane) air mixtures is then studied for hydrogen addition ratio varying from 0 < RH < 0.5 and over a wide range of mixture equivalence ratio. Also, the investigation is carried out for mixture temperature up to 450 K and pressure ranging from 1 to 10 bar. A parabolic variation of laminar flame speed is observed with equivalence ratios giving peak value for slightly rich mixture. A linear correlation has been observed for the flame speed as a function of hydrogen addition, RH at all the conditions studied. Whereas, power law correlation has been proposed for the hydrogen added LPG–air mixture, to understand the dependency of laminar flame speed on temperature and pressure. A generic correlation has been proposed to study the combined effect of temperature and pressure on laminar flame speed.

More »»A numerical investigation of steady laminar premixed propane-air flames is presented. A three-dimensional simulation has been performed to examine the impact of operating conditions on steady-state characteristics of a perforated burner flame. A numerical simulation has been carried out using a reduced propane-air reaction mechanism having 30 species and 192 reactions. The results are validated against the one-dimensional flat-flame result obtained using PREMIX. Effects of the equivalence ratio, inlet velocity, hole-hole distance, and plate thermal conductivity on flame stability are examined. The flame stand-off distance increases with the increase in the inlet velocity. As the equivalence ratio increases, the heat flux to the plate increases as the flame moves closer to the plate. When the plate is adiabatic, the conical flame rests on the plate. The flame stand-off distance increases as the plate thermal conductivity is increased. The flame moves downstream of the plate as the distance between the adjacent holes is increased. © 2014 American Chemical Society.

More »»Joining dissimilar materials is required in many engineering applications and conventional fusion welding of dissimilar materials often results in defective welds. Friction Stir Welding (FSW) has paved way for joining dissimilar alloys and defect-free joints have been obtained for a number of dissimilar material combinations. Numerical modelling of FSW process can provide reasonable insight into the physics of the process and will aid in minimising the number of experimental trials. In this paper, Computational Fluid Dynamics (CFD) based numerical model is developed to predict the temperature distribution and material flow during FSW of dissimilar aluminum alloys AA2024 and AA7075. Volume of fluid approach is used and the FSW process is modelled as a steady-state visco-plastic laminar flow past a rotating cylindrical tool. Results indicate that peak temperature in the welded plates increases with the increase of Tool Rotation Speed (TRS) and Shoulder Diameter (SD), whereas the peak temperature decreases with increase in Welding Speed (WS). Increasing TRS and SD increases material flow, while increasing WS decreases material flow in the stir zone.

More »»The current work involves a numerical study of the effect of preset pitch angle on the performance of a Vertical Axis Wind Turbine (VAWT). A three bladed H-Darrieus VAWT has been considered for the study. The equations governing the flow are solved using a commercial CFD code ANSYS CFX 13. The turbine with NACA 0015 profile and zero pitch angle as the reference case for comparison. The analysis has been done for three pitch angles -6o, 0o, +6o, tip speed ratios (TSR) from 1 to 2.2 and wind velocities of 6, 8 and 10 m/s. Of the pitch angle considered, the best performance is observed with -6o for all tip speed ratios and wind velocities. This has been explained by studying the instantaneous torque characteristics of the turbine. It is seen that at any given instant, the blade in the upwind region contributes significantly to the positive torque with other blades either contributing less or negating the positive torque. The pressure coefficient distributions over the upwind blade and stream lines at different azimuthal angles have also been analysed to understand the effect of pitch.

More »»Natural convection is a widely studied phenomenon because of the extensive applications in cooling of large scale electrical and electronic equipments. The current study involves study of effect of vent locations on natural convection in enclosures with partial openings having an internal heat source. It involves the numerical simulation of 2D steady state natural convection in enclosure of different aspect ratios (H/W=1, 2 and 3) for lower Rayleigh numbers (Rah=103, 104 and 105). Four different configurations have been considered based on the number and position of vents - same side (SS), diagonal side (DS), one inlet two outlets (1I2O) and two inlets one inlet (2I1O). The mass flow rate driven through the enclosure and the average Nusselt number over the heater surface for all the four configurations have been compared. It is found that the 2I1O configuration yielded better heat transfer rates of the four considered. It was found that the mass flow rates and Nu increased with increase in Rah and decrease in the aspect ratio. © 2013 Elsevier Ltd.

More »»Mixture homogeneity plays a crucial role in HCCI engine. In the present study, the mixture homogeneity was analysed by three-dimensional engine model. Combustion was studied by zero-dimensional single zone model. The engine parameters studied include speed, injector location, valve lift, and mass of fuel injected. Valve lift and injector location had less impact on mixture formation and combustion phasing compared to other parameters. Engine speed had a noticeable effect on mixture homogeneity and combustion characteristics. © 2013 M. K. Lalith et al.

More »»The laminar burning velocity of pure and diluted high-temperature propane-air mixtures is extracted from the planar flames stabilized in the preheated mesoscale diverging channel. The experiments were carried out for a range of equivalence ratios of 0.7 ≥ Φ ≥ 1.3 and mixture temperatures of 370-650 K. The effect of dilution using CO 2 and N 2 gases (up to 40%) on C 3H 8-air burning velocity is also studied. Experiments complimented with computational studies of experimental conditions confirm that the stabilized flames were planar in both transverse and depth directions, and the burning velocity with heat flux in the present case is nearly equal to the adiabatic burning velocity. The detailed uncertainty analysis shows the accuracy of the present measurement within ±5%. Computational predictions of burning velocity and detailed flame structure were performed using PREMIX code. The present experiments are successfully validated against existing experimental and computational results. The peak burning velocity was observed for slightly rich mixtures even at higher mixture temperatures. The minimum value of the temperature exponent is observed for slightly rich mixtures. The burning velocity was observed to decrease with the dilution of inert gases. The addition of CO 2 shows a pronounced decrease in the burning velocity, as compared to N 2. © 2012 American Chemical Society.

More »»A computational fluid dynamics(CFD) based numerical model is developed to predict the temperature distribution during Friction Stir Welding(FSW) of dissimilar aluminum alloys. The effect of tool rotation speed and axial pressure on heat transfer during FSW has been studied. Numerical results indicate that the maximum temperature in FSW process can be increased with the increase of the axial pressure and tool rotation speed. The influence region of the tool shoulder in the direction of thickness can be increased with the increase in the axial pressure on the shoulder. © (2012) Trans Tech Publications, Switzerland

More »»The objective of this work was to study the effect of dilution with carbon dioxide on the adiabatic burning velocity of syngas fuel (with various H2/CO ratios)-air(21% O2–79% N2 by volume) mixtures along with detailed understanding of cellular flame structures. Heat flux method with a setup similar to that of de Goey and co-workers [1] was used for measurement of burning velocities. Validation experiments were done for H2 (5%)–CO (95%)–air and H2 (5%)–CO (45%)–CO2 (50%)–air mixtures at various equivalence ratios and the results were in good agreement with published data in the literature. The mixtures considered in this work had 1:4, 1:1 and 4:1 H2/CO ratio in the fuel and 40%, 50% and 60% CO2 dilution. The burning velocity increased significantly with the increase in H2 content in mixture of H2–CO with fixed CO2 dilution. The burning velocity reduced remarkably with carbon dioxide dilution in H2–CO mixture due to reduction in heat release, flame temperature and thermal diffusivity of the mixture. The location of peak adiabatic burning velocity shifted from ϕ = 1.6 for 40% CO2 to ϕ = 1.2 for 60% CO2, whereas it remained unchanged with variation of H2:CO ratio (4:1, 1:1 and 1:4) at a given CO2 dilution. A comparison of experiments and simulations indicated that the Davis et al. [2] mechanism predicted burning velocities well for the most of experimental operating conditions except for rich conditions. For some lean mixtures, flames exhibited cellular structures. In order to explain the structures and generate profiles of various field variables of interest, computations of three dimensional porous burner stabilized cellular flames were performed using commercial CFD software FLUENT. Simulations for lean H2 (25%)–CO (25%)–CO2 (50%)–air mixtures (ϕ = 0.6 and 0.8) produced cellular flame structures very similar to those observed in the experiments. It was found that the in the core region of a typical cell, stretch rate was positive, the volumetric heat release rate was high and the net reaction rate for the reaction O + H2 ⇄ H + OH and the net consumption rate of H2 were both high.

More »»Global warming due to CO2 emissions has led to the projection of hydrogen as an important fuel for future. A lot of research has been going on to design combustion appliances for hydrogen as fuel. This has necessitated fundamental research on combustion characteristics of hydrogen fuel. In this work, a combination of experiments and computational simulations was employed to study the effects of diluents (CO2, N2, and Ar) on the laminar burning velocity of premixed hydrogen/oxygen flames using the heat flux method. The experiments were conducted to measure laminar burning velocity for a range of equivalence ratios at atmospheric pressure and temperature (300 K) with reactant mixtures containing varying concentrations of CO2, N2, and Ar as diluents. Measured burning velocities were compared with computed results obtained from one-dimensional laminar premixed flame code PREMIX with detailed chemical kinetics and good agreement was obtained. The effectiveness of diluents in reduction of laminar burning velocity for a given diluent concentration is in the increasing order of argon, nitrogen, carbon dioxide. This may be due to increased capabilities either to quench the reaction zone by increased specific heat or due to reduced transport rates. The lean and stoichiometric H2/O2/CO2 flames with 65% CO2 dilution exhibited cellular flame structures. Detailed three-dimensional simulation was performed to understand lean H2/O2/CO2 cellular flame structure and cell count from computed flame matched well with the experimental cellular flame.

More »»In recent years, porous or solid insert has been used in a duct for enhancing heat transfer in high temperature thermal equipment, where both convective and radiative heat transfer play a major role. In the present work, the study of heat transfer enhancement is carried out for flow through a square duct with a porous or a solid insert. Most of the analyses are carried out for a porous insert. The hydrodynamically developing flow field is solved using the Navier–Stokes equation and the Darcy–Brinkman model is considered for solving the flow in the porous region. The radiative heat transfer is included in the analysis by coupling the radiative transfer equation to the energy equation. The fluid considered is CO2 with temperature dependent thermophysical properties. Both the fluid and the porous medium are considered as gray participating medium. The increase in heat transfer is analyzed by comparing the bulk mean temperature, Nusselt number, and radiative heat flux for different porous size and orientation, Reyonlds number, and Darcy number.

More »»Producer gas is one of the promising alternative fuels with typical constituents of H2, CO, CH4, N2, and CO2. The laminar burning velocity of producer gas was computed for a wide range of operating conditions. Flame stability due to preferential diffusional effects was also investigated. Computations were carried out for spherical outwardly propagating flames and planar flames. Different reaction mechanisms were assessed for the prediction of laminar burning velocities of CH4, H2, H2-CO, and CO-CH4 and results showed that the Warnatz reaction mechanism with C1 chemistry was the smallest among the tested mechanisms with reasonably accurate predictions for all fuels at 1 bar, 300 K. To study the effect of variation in the producer gas composition, each of the fuel constituents in ternary CH4-H2-CO mixtures was varied between 0 to 48%, while keeping diluents fixed at 10% CO2 and 42% N2 by volume. Peak burning velocity shifted from to 1.1 as the combined volumetric percentage of hydrogen and CO varied from 48% to 0%. Unstable flames due to preferential diffusion effects were observed for lean mixtures of fuel with high hydrogen content. The present results indicate that H2 has a strong influence on the combustion of producer gas. More »»

Experimental measurements of the adiabatic burning velocities were carried out for natural gas-like mixtures burning in air over a range of equivalence ratios at atmospheric pressure. Effect of CO2 dilution up to 60%, N2 dilution up to 40% and 25% enrichment of ethane on burning velocity of methane–air flames were studied. Heat flux method with setup similar to that of [K.J. Bosschaart, L.P.H. de Goey, Detailed analysis of the heat flux method for measuring burning velocity, Combustion and Flame 132 (2003) 170–180] was used for measurement of burning velocities. Initially experiments were done for methane–air and ethane–air mixtures at various equivalence ratios and the results were in good agreement with published data in the literature. Computations were performed using PREMIX code with GRI 3.0 reaction mechanism for all the mixtures. Predicted flame structures were used to the explain the effect of N2 and CO2 dilution on burning velocity of methane–air flames. Peak burning velocity for CH4/CO2–air mixtures occur near to ϕ = 1.0.

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Dr. Supriya P.Sonali AgrawalDr. Govindaraju M.Sini Raj P.