Krithika Narayanaswamy

Assistant Professor
Computational Chemistry & Combustion group,
Thermodynamics and Combustion Engineering Lab,
Department of Mechanical Engineering,
Indian Institute of Technology Madras,
Chennai - 600036
Email: krithika (at) iitm (dot) ac (dot) in

Research Experience
Faculty page
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Scholar Profiles @ IITM

My research focuses on development of chemical kinetic models to describe oxidation of fuels. I am interested in predicting global combustion characteristics of conventional and alternative fuels and interpreting these observations based on insights gained from molecular level kinetic descriptions.

If you are interested in being a part of our team, peruse the list of available projects to identify your interests and write to me with a subject line that includes the title of the topic. Please note that I am *not* interested in hiring interns.

Abstracts for topics floated for MS admissions (Winter 2018)

Research highlights


An alternative way to formulate transportation fuels surrogates using model predictions of gas-phase combustion targets is explored and compared to conventional approaches. This study suggests that in a computational modeling context, surrogate compositions should be determined not just based on global characteristics, as has been done so far, but also on the characteristics and predictive capabilities of the chemical kinetic mechanism used for the simulations.

An accurate, fast, direct and robust algorithm to compute multi-component diffusion velocities has been proposed. To our knowledge, this is the first provably accurate algorithm scaling at a computational complexity of O(N) in nite precision. The above figure compares the total time taken by our proposed fast algorithm to compute diffusion velocities versus the total time taken by the iterative biconjugate gradient method.

A flexible and evolutive component library framework has been proposed to derive short chemical mechanisms with only the necessary kinetics for the desired surrogate mixture. Figure showd the chemical model developed our earlier works reorganized into this framework. A script to extract a chemical mechanism for a surrogate mixture, the kinetics of whose individual components are described in this parent chemical mechanism, is available under the tab publications


Ignition delay times of JP-8/Jet-A fuels at stoichiometric fuel/air equivalence ratios: Symbols - experimental data from several sources. Simulations are performed by representing the real jet fuel as a surrogate containing 30.3% n-dodecane, 21.2% m-xylene, and 48.5% methylcyclohexane (mole %). The kinetics of this surrogate mixture are extracted from a multi-component reaction mechanism using the component library approach.


Research Team

Our research focuses on development of chemical kinetic models to describe oxidation of fuels. I am interested in predicting global combustion characteristics of conventional and alternative fuels and interpreting these observations based on insights gained from molecular level kinetic descriptions. In the recent times, my team has been studying kinetics of oxygenated fuels, which being renewable and resulting in reduced emissions, are immediately relevant to the country's energy needs. Some work carried out by our alumni are showcased here.

If you are interested in being a part of our team, peruse the list of available projects to identify your interests and write to me with a subject line that includes the title of the topic. Please note that I am *not* interested in hiring interns.


  • Compact kinetic model for methyl methacrylate oxidation:

    In these days, synthetic and natural polymeric esters find applications in transport and construction sectors, where fire safety is an important concern. One polymer that is wide used is poly methyl methacrylate (PMMA), which almost completely undergoes thermal decomposition into methyl methacrylate (its monomer) CH2=C(CH3)-C(=O)-O-CH3 (MMA) at ~250-300oC. In order to analyze the high temperature gas phase oxidation of PMMA, and thereby predict its fire behaviour (such as burning rate, temperature of the material and heat fluxes) with less computational effort, a compact kinetic model for the oxidation of its primary decomposition product, MMA, is most essential.

    As a part of this work, a compact reaction model to describe the oxidation of MMA is developed and validated against fundamental experimental datasets obtained in premixed flames, starting with a detailed mechanism proposed by the Lawrence Livermore group.

    Evaluating the model against these data sets point to the need to revise the kinetic model, which is achieved by adopting rate constants of key reactions from recent literature for analogous molecules. The updated compact kinetic model is able to predict the major species in the flat flame as well the burning velocity of MMA satisfactorily. The final `short MMA mechanism' consists of 88 species and 1092 reactions.


Shanmugasundaram D

Shanmugasundaram obtained his B. Tech and M. Tech in Mechanical Engineering from Pondicherry Engineering College, Puduchery in 2014 and 2016 respectively. He is currently pursuing his PhD at IIT Madras. His project revolves around chemical kinetic modeling and reactive simulations of fuels relevant to fire research, one among them being methylmethacrylate. His thesis is co-advised by Dr. V. Raghavan at IIT Madras.


  • Importance of unsaturated ester constituent in biodiesel surrogates:

    In one of our recent studies, we investigated the kinetics of a small ester, which is a potentially important candidate to represent the longer chain molecules in the real biodiesel fuel, namely methylbutanoate. While methylbutanoate is a saturated ester, the real biodiesel also contains a significant degree of unsaturation (depending on the source of the oil), which results in considerable differences in combustion characteristics, such as in ignition delay times. In this work, the importance of including an unsaturated molecule in the bioidiesel surrogate will be investigated.

    A kinetic scheme is being developed for methyl crotonoate, which is a simple unsaturated ester, that is representative of the long chain unsaturated esters in the real biodiesel. To validate the kinetic model, experimental data at intermediate temperatures for ignition delays measured in an RCM and species profiles in a JSR will be utilized, in addition to the experimental data available at high temperatures. Besides ascertaining the importance of including an unsaturated ester constituent in biodiesel surrogates, the reaction scheme proposed and the rate constants used therein will act as a basis to build reaction mechanisms for longer chain unsaturated esters, which are less understood presently.

Praise Noah Johnson

Praise obtained his B.E in Mechanical Engineering from Maharaja Engineering College, Coimbatore in 2017. He is presently pursuing his Masters at IIT Madras. His research work centers on kinetics of alternative fuels, particularly relevant to aviation.


  • Surrogates for liquid phase applications:

    Surrogate mixtures are often used to emulate gas phase combustion characteristics of real fuels, such as heating value, sooting characteristics, and propensity to ignition. These cannot be used as such in liquid phase applications, where multi-phase processes, such as spray injection, are important. Typically, for these applications, surrogates are proposed by matching targets such as density, viscosity, and distillation curves between the real fuel and the surrogate. However, these targets do not pertain to a combustion environment. One attractive option to include evaporation and phase equilibrium dynamics in the surrogate definition is to study the combustion characteristics of an isolated droplet. This project involves simulating the burning process of isolated fuel droplets at low gravity for neat fuel components as well as mixtures of hydrocarbons relevant as transportation fuel surrogates. Evaporation rates of fuels in this simple configuration may be useful quantities to describe the multi-phase effects in a combusting environment.

    In this project, numerical solution procedure to predict the droplet burning accounting for the interface conditions will be developed. Techniques to obtain solutions with reduced computational time will be explored. The validity of the model will be ascertained based on the vast data available in the literature. Thereafter, evaporation rate rules will be developed for the surrogate mixture in terms of the components, and investigated if it is indeed an appropriate measure or if other additional parameters may be needed to come up with a good surrogate valid for liquid-phase applications.

Pragnesh Rajubhai Rana

Pragnesh obtained his B.E. in Mechanical Engineering from Gujarat Technological University in 2016. He is currently pursuing his Masters (interdisciplinary) at IIT Madras. His research topic focuses on simulation of droplet combustion with accurate chemical kinetics. His thesis is co-advised by Dr. Sivaram Ambikasaran at IIT Madras.


  • Optimization techniques in combustion kinetics:

    The progress rates of individual steps in the oxidation of fuels are uncertain. In combustion studies, an optimized model is arrived at by taking these uncertainties into account. A black box tool will be developed to optimize reaction schemes based on existing ideas. A starting point will be the in-house code -- Reaction mechanism optimization. Improvements will be suggested to existing methods to achieve reduced computational cost as well ensure consistency in the optimized models.

Krunal Rajeshkumar Panchal

Krunal obtained his B.E. in Mechanical Engineering from Government Engineering College, Modasa, Gujarat in 2016. Thereafter, he obtained his M. Tech in Mechanical Engineering from Nirma Unirversity, Ahmedabad, Gujarat in 2018. His research topic focuses on optimization methods in combustion kinetics.


Funding sources

  • New Faculty Initiation Grant, Project No. MEE/15-16/845/NFIG: September 2015--2017
  • Exploratory Research Project, May 2016--2017
  • Indo-Russian project awarded by DST under Grant No. 16-49-02017: October 2016--2019
  • InnoINDIGO BiofCFD project awarded by DST: November 2017--2020
  • New Faculty Seed Grant, Project No. MEE/15-16/845/NFIG: November 2017--2020

Collaborations



  • Kinetics of biodiesel surrogate components:

    One of our recent interests concerns with developing a kinetic scheme for a small ester, which is a potentially important candidate to represent the longer chain molecules in the real biodiesel fuel, namely methylbutanoate. A compact reaction scheme is derived for methylbutanoate from an existing detailed mechanism, revised based on recent experimental measurements and theoretical rate constant calculations. The revised kinetic model has been validated comprehensively against a wide range of experimental data along with ignition delays at intermediate temperatures measured in an RCM at PTB, Germany.


    Thereafter, a novel approach is used to propose surrogates to represent biodiesel fuel, consisting of methylbutanoate and n-dodecane, and assessed thoroughly (Fig. below). This work serves as our first step towards the development of a compact reaction scheme for a biodiesel surrogate which will be coupled with combustion studies to investigate the use of biodiesels and its blends with diesel in CI engines.


    Fig: Ignition delays in a shock tube and Species profiles in a jet stirred reactor; symbols: experiments for biodiesel, lines: Surrogate (presented at the 10th U.S. National Combustion Meeting, 2017)


Aditya Dilip Lele

Aditya obtained his B. Tech in Mechanical Engineering from Vishwakarma Institute of Technology, Pune in 2015. He received his Masters at IIT Madras in 2018, for his work on kinetic modeling of biodiesel surrogates and reacting flow simulations in CI engines. His thesis was co-advised by Dr. K. Anand at IIT Madras. He is currently pursuing his PhD at Penn State.
  • Extinction studies of oxygenated fuels:

    Addition to oxygenates to diesel fuel has been found to reduce soot emissions. Nonetheless, the resulting changes in the extinction and auto-ignition characteristics of the fuel mixture have not yet been fully understood. Considering two important oxygenates, dimethyl ether and methanol, we undertook a fundamental analysis, which reveals that blending small amounts of oxygenates with diesel increases its resistance to extinction, which can be of use in applications such as burners, furnaces and pre-vaporizers. We also find that the auto-ignition characteristics are not altered much due to blending. This study suggests that in the presence of oxygenate, a combustion system can be made more stable even at higher strain rates and at the same time operate with reduced emissions.



    In order to critically evaluate the overall combustion behaviour of DME via numerical simulations, an accurate as well as compact kinetic mechanism to describe its oxidation is most essential. A short kinetic mechanism consisting of 23 species and 88 elementary reactions is proposed to describe the oxidation of DME based on the detailed San Diego mechanism. The short mechanism accurately reproduces the available experimental data for ignition delays, laminar flame speeds, and species profiles in flow reactors as well as jet-stirred reactors.

    To assess the validity of this reaction mechanism in non-premixed systems, extinction strain rates of DME-air mixtures, which are not available in the literature, are measured in a counter-flow diffusion flame burner. Details on the experimental set up can be found here.

    The 23-species reaction mechanism is able to predict the experimental data for extinction within the uncertainty limits. This mechanism is further reduced by introducing quasi-steady state assumptions for six intermediate species to finally obtain a 14-step global kinetic scheme. A code is developed in MATLAB to obtain these 14 global steps and their corresponding rate expressions in terms of the elementary reaction rates. The 14-step mechanism performs as good as the 23-species mechanism for all the experimental data sets tested for.

Rohit Sanjay Khare

Rohit obtained his B. Tech in Mechanical Engineering from Vishwakarma Institute of Technology, Pune in 2015. He received his Masters at IIT Madras in 2018, for his work on fundamental experimental and computational studies of extinction strain rates of oxygenated fuels and their blends with conventional fuels. His thesis was co-advised by Dr. V. Raghavan at IIT Madras. He is currently pursing his PhD with Dr. Alexandra Loukou and Prof. Dr.-Ing. Dimosthenis Trimis in the Combustion Technology department of the Engler-Bunte-Institute at Karlsruhe Institute of Technology.


  • SMILES based interface to Thermodynamic Property Estimation Using THERM:

    Fuels, both renewable and non-renewable, are major sources of energy. Reaction schemes describing the oxidation of fuels are increasingly incorporated within computations where the focus is in capturing reactivity and the amounts of emissions. Thermodynamic properties of the species, which include the heat of formation, specific heat capacity and entropy, must be provided as part of such a kinetic scheme. These properties are used in determining the (a) equilibrium constant and thereby, the (b) reverse reaction rate constant using the principle of microscopic reversibility and (c) the heat release term of the energy conservation equation.

    To find the thermodynamic property values of a species, group additivity approach can be used, which is a simple and feasible method. It hinges on the idea that: for any species, the thermodynamic property values can be calculated as the sum of contributions to the property from all groups present in that species. THERM is a software that uses this method to find property values, taking in the group type, number of rotors and symmetry number of the species, as inputs. In this project, a program is developed that can calculate all the inputs needed for THERM, from either molfile or SMILES of a given species. This program is capable of processing any non-cyclic stable or single radical species, made up of carbon, hydrogen and oxygen atoms. The code is available open-source on github.
  • Reaction mechanism optimization:

    In this study, a framework for reaction mechanism optimization is developed and the idea has been implemented as a black box tool. This tool requires target information and uncertainty of rate constants as inputs. This modular Python script uses FlameMaster (Pitsch, H. FlameMaster v3.3.10) for kinetics simulations and NLopt for minimization of objective function. Numerical simulations are decoupled from the optimization by a response surface that approximates the target values as algebraic functions of normalized reaction rate constants. As opposed to the factorial design approach, a sensitivity based method adopted here (Davis et al. 2004). It generates a response surface with fewer computations, but with comparable accuracy. Finally, the minimization is carried out on an objective function indicative of the error between calculated and observed target values. To demonstrate the applicability of this tool, a reaction mechanism for n-heptane is considered.

    Scope of performing optimization in multiple stages utilizing the underlying kinetic knowledge is also explored. The optimization tool developed as a part of this work is made available on github in a black-box fashion for the use of the combustion community.
  • Fast multi-component diffusion within FlameMaster:

Open source codes

Conference proceedings

2017 -- Present

  • A. D. Lele, K. Anand, K. Narayanaswamy, "Development of a chemical kinetic mechanism for biodiesel surrogate", 10th U.S. National Combustion Meeting, 2017.

  • R. Khare, V. Raghavan, K. Narayanaswamy, "A chemical kinetic modeling study of the effects of oxygenated species on soot emissions from diesel engines", Proceedings of the International Conference on Sustainable Energy and Environmental Challenges, 2017.

  • R. Khare, V. Raghavan, K. Narayanaswamy, "Study of auto-ignition and extinction characteristics of diesel blended with oxygenates in laminar opposed non-premixed flames", 10th U.S. National Combustion Meeting, 2017.

  • M. Hunyadi-Gall, G. Mairinger, R. Khare, K. Narayanaswamy, V. Raghavan, K. Seshadri, "The Influence of Stoichiometric Mixture Fraction on Extinction of Laminar, Nonpremixed DME Flames", 10th U.S. National Combustion Meeting, 2017.

Journal publications

*Submitted versions of manuscripts that are still under review and pre-prints of publications are provided to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by the authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's or publisher's copyright. These documents may not be reposted without the explicit permission of the copyright holder.

Book Chapter

  • A. D. Lele, K. Anand, and K. Narayanaswamy. "Surrogates for Biodiesel: Review and Challenges." Biofuels. Springer Singapore, 2017. 177-199.

Write-up coming soon ...
  • Development of kinetic model for oxygenated fuels (knock-reduction additives)
  • Automatic reaction mechanism generation
  • Methods for mechanism reduction
  • Development of structure based compact reaction models
  • Development of canonical kinetics solvers and post-processing tools
  • Simulation driven surrogate formulation
  • Thermodynamic property estimation for cyclic species

Alma mater

Vivekananda Vidyalaya, Perambur
DAV Girls, Gopalapuram
Indian Institute of Technology Madras
Stanford University
Cornell University

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