Qualification: 
Ph.D
Email: 
v_ratnakishore@cb.amrita.edu

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. January 2011 - November 2016
  • Associate Professor, November 2016 - 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

2017

Journal Article

A. Pa Singh, Dr. Ratna Kishore V., Yoon, Yc, Minaev, Sd, and Kumar, Sa, “Effect of Wall Thermal Boundary Conditions on Flame Dynamics of CH4-Air and H2-Air Mixtures in Straight Microtubes”, Combustion Science and Technology, vol. 189, pp. 150-168, 2017.[Abstract]


Unsteady numerical simulations with detailed chemistry have been carried out for premixed stoichiometric CH4-air and H2-air mixtures in straight microtubes to understand the flame-wall coupling and its effect on flame dynamics for a range of wall heat transfer conditions. Varying flame shapes were observed during the unsteady flame propagation mode. These flame modes are represented with flame shape angles and the corresponding flame shape is correlated to the wall heat transfer conditions. Various similarities in flame propagation characteristics have been observed for both of the fuels. A normalization technique has been adopted to establish the independence of variation of nondimensional flame propagation velocity on fuel type. It has been observed that an increase in convective heat transfer coefficient, h, though increasing the heat loss from a propagating flame, does not necessarily lead to a monotonic decrease in flame propagation speed. A transition regime where 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 better understanding of flow redirection and its impact on flame shape and flame propagation behavior. © 2017 Taylor & Francis.

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2017

Journal Article

Dr. Ratna Kishore V., Minaev, Sb, Akram, Mc, and Kumar, Sd, “Dynamics of premixed methane/air mixtures in a heated microchannel with different wall temperature gradients”, RSC Advances, vol. 7, pp. 2066-2073, 2017.[Abstract]


The observation of various flame propagation modes for externally heated tubes has led to many fundamental studies aimed at understanding flame propagation in microtubes. During these studies, it has been observed that for moderately low flow velocities, flames with repetitive extinction and ignition (FREI) have been observed to exist in various experimental, theoretical and numerical studies. The formation of these FREI flame modes depends on various parameters such as channel dimensions, wall temperature gradient, flow rates and mixture type. In the present work, an effort has been made to understand the effect of the wall temperature gradient on the FREI phenomenon through a 1 mm diameter circular tube using 2D numerical studies with detailed GRI Mech3.0 for premixed methane/air mixtures. The different wall temperature gradients analyzed are varied from 33.3-1 K mm−1, with an upper range corresponding to experimental conditions. Five different phases of flame propagation have been observed during the FREI flame propagation mode. The entire fuel gets consumed during the cycle and a significant amount of unburned CO remains during the weak reaction phase, towards the extinction of FREI mode. The effect of the wall temperature gradient on the FREI ignition phenomenon has been investigated to understand the development of ignition kernels. It is observed that the ignition happens at the axis and not at the wall of the channel. This happens due to a boundary-layer phenomenon discouraging ignition at the wall. It has been observed that a decrease in the temperature gradient results in movement of the ignition point towards the low-temperature region. The peak CO value increases with a decrease in the wall temperature gradient. © The Royal Society of Chemistry.

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2017

Journal Article

A. N. Mohammed, Juhany, K. A., Kumar, S., Dr. Ratna Kishore V., and Mohammad, A., “Effects of CO2/N2 dilution on laminar burning velocity of stoichiometric DME-air mixture at elevated temperatures”, Journal of Hazardous Materials, vol. 333, pp. 215-221, 2017.[Abstract]


The laminar burning velocity of CO2/N2 diluted stoichiometric dimethyl ether (DME) air mixtures is determined experimentally at atmospheric pressure and elevated mixture temperatures using a mesoscale high aspect-ratio diverging channel with inlet dimensions of 25 mm × 2 mm. In this method, planar flames at different initial temperatures (Tu) were stabilized inside the channel using an external electric heater. The magnitude of burning velocities was acquired by measuring the flame position and initial temperature. The mass conservation of the mixture entering the inlet and the stationary planar flame front is applied to obtain the laminar burning velocity. Laminar burning velocity at different initial mixture temperatures is plotted with temperature ratio (Tu/Tu,o), where a reference temperature (Tu,o) of 300 K is used. Enhancement in the laminar burning velocity is observed with mixture temperature for DME-air mixtures with CO2 and N2 dilutions. A significant decrease in the burning velocity and slight increase in temperature exponent of the stoichiometric DME-air mixture was observed with dilution at same temperatures. The addition of CO2 has profound influence when compared to N2 addition on both burning velocity and temperature exponent. © 2017 Elsevier B.V.

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2017

Journal Article

A. Subramanian, Yogesh, S. A., Sivanandan, H., Giri, A., Vasudevan, M., Mugundhan, V., and Dr. Ratna Kishore V., “Effect of airfoil and solidity on performance of small scale vertical axis wind turbine using three dimensional CFD model”, Energy, vol. 133, pp. 179-190, 2017.[Abstract]


This paper presents a study on the effect of solidity and airfoil profile on the performance of Vertical Axis Wind Turbines (VAWTs). A 1.1 kW commercially viable Darrieus VAWT was studied using ANSYS Fluent. Four different airfoils – NACA 0012, NACA 0015, NACA 0030 and AIR 001 – were considered in the analysis. The tip speed ratios (λ) were varied from 1 to 2.5 with an incoming wind velocity of 10 m/s. It was observed that NACA 0030 performed better at lower values of λ due to long duration of attached flow; while NACA 0012 performed better at λ > 1.8 with a wider range of λ. The shed vortex dissipates much faster for thinner airfoils than for thicker airfoils at higher values of λ. Two bladed VAWTs generated more power than the three bladed turbines. This indicated that turbines with lower solidity perform better at high λ. © 2017 Elsevier Ltd

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2017

Journal Article

D. K. Valappil, Somasekharan, N., Krishna, S., Dr. Laxman Vaitla, and Dr. Ratna Kishore V., “Influence of solidity and wind shear on the performance of VAWT using a free vortex model”, International Journal of Renewable Energy Research, vol. 7, pp. 787-796, 2017.[Abstract]


Performance analysis of a VAWT and HAWT is highly complex due to fluid structure interactions and blade vortex interactions. However, there are simplified methods such as momentum theory to most expensive CFD models available for performance prediction. CACTUS is neither as simple as the momentum theory nor as complex as the CFD models, it is an open source code that uses the free vortex method to predict the performance of a wind turbine. In this paper, the effect of solidity and wind shear on the performance of an H-type Darrius VAWT is studied using CACTUS. Variation of solidity was achieved by changing the chord length (c/R =0.04-0.07) and number of blades (N =2,3). It has been observed that at lower tip speed ratio (TSR < 3) the turbine with longer c/R was found to be more efficient due to large wind interception by the blades; and at higher TSR ( > 3) shorter c/R was more efficient due to relatively low wake blade interaction. The improvement in performance due increasing the number of blades is effective only up to a particular TSR. Effect of wind shear due to the tower height from the ground using the power law equation with values of power law coefficient ranging from 0.1 to 0.3 has also been studied. It is observed that the power coefficients of the VAWT under a turbulent boundary layer are in congruence with the experimental results.

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2016

Journal Article

A. Nair, Dr. Ratna Kishore V., 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]


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 »»

2016

Journal Article

A. Tummala, Dr. Ratna Kishore V., Sinha, D. Kumar, Indraja, V., and V. Krishna, H., “A review on small scale wind turbines”, Renewable and Sustainable Energy Reviews, vol. 56, pp. 1351 - 1371, 2016.[Abstract]


Abstract Meeting future world energy needs while addressing climatic changes has led to greater strain on conventional power sources. One of the viable sustainable energy sources is wind. But the installation large scale wind farms has a potential impact on the climatic conditions, hence a decentralized small scale wind turbines is a sustainable option. This paper presents review of on different types of small scale wind turbines i.e., horizontal axis and vertical axis wind turbines. The performance, blade design, control and manufacturing of horizontal axis wind turbines were reviewed. Vertical axis wind turbines were categorized based on experimental and numerical studies. Also, the positioning of wind turbines and aero-acoustic aspects were presented. Additionally, lessons learnt from various studies/countries on actual installation of small wind turbines were presented. More »»

2016

Journal Article

Ba Aravind, Dr. Ratna Kishore V., 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]


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 »»

2016

Journal Article

E. J. Veetil, Rajith, C. V., and Dr. Ratna Kishore V., “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

Dr. Ratna Kishore V., 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.

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2015

Journal Article

Dr. Ratna Kishore V., Arun, J., Dr. Padmanaban 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]


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.

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2015

Journal Article

Aa Nair, Dr. Ratna Kishore V., 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]


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 &lt; 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 &amp; Francis Group, LLC.

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2015

Journal Article

B. M. M. S. R. S., Dr. Ratna Kishore V., Dr. Anbuudayasankar S. P., 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]


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

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2015

Journal Article

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


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.

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2015

Journal Article

B. Aravind, Dr. Ratna Kishore V., 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.

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2015

Journal Article

A. Gowrishankar, Vignesh, S., Sunder, P. B. Shyam, Abhinav, R., Vivek, M., and Dr. Ratna Kishore V., “Numerical Study of Natural Convection in an Enclosure with an Internal Heat Source at Higher Rayleigh Numbers”, Heat Transfer - Asian Research, vol. 44, pp. 620-640, 2015.[Abstract]


Natural convection is extensively used in cooling of large scale electrical and electronic equipments. This work involves study of flow and heat transfer characteristics in enclosures with partial openings having an internal heat source at higher Rayleigh number (Rah > 106). It involves the numerical simulation of 2D steady state natural convection in enclosures of different aspect ratios (H/W = 2 and 3) for five Rayleigh numbers (Rah = 107, 108, 109, 1010, and 1011). Two different configurations have been considered based on the number and position of vents-diagonal side (DS) and two inlets one outlet (2I1O). The time dependent nature of the flow is characterized by performing a Fast Fourier Transform (FFT) analysis of temperature and velocity at a characteristic location in the enclosure. The global parameters considered are the mass flow rate driven through the cavity by the heater and the average Nu defined over the heater surface. It is seen that with increase in Rah, flow becomes more fluctuating and moves towards chaotic regime and this transition is quicker at lower H/W. For the given configuration both the global parameters increases with increase in Rah and decrease in H/W. © 2015 Wiley Periodicals, Inc.

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2014

Journal Article

E. V. Jithin, Dr. Ratna Kishore V., 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]


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.

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2014

Journal Article

S. Chandramouli, Premsai, T. P., Prithviraj, P., Mugundhan, V., and Dr. Ratna Kishore V., “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.

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2013

Journal Article

R. Abhinav, Sunder, P. B. S., Gowrishankar, A., Vignesh, S., Vivek, M., and Dr. Ratna Kishore V., “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]


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.

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2013

Journal Article

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


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.

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2012

Journal Article

Ma Akram, Dr. Ratna Kishore V., 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]


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.

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2012

Journal Article

Dr. Padmanaban R., Balusamy, Vb, and Dr. Ratna Kishore V., “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]


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

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2011

Journal Article

Dr. Ratna Kishore V., 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.

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2009

Journal Article

Dr. Ratna Kishore V., 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.

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2009

Journal Article

P. Parthasarathy, Talukdar, P., and Dr. Ratna Kishore V., “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.

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2008

Journal Article

Dr. Ratna Kishore V., 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

Dr. Ratna Kishore V., 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.

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