CRF Visitors, November 2012-March 2013
Swetaprovo Chaudhuri, Princeton University
Host: Jackie Chen
Postdoc Swetaprovo Chaudhuri visited the CRF to collaborate with Jackie Chen and Hemanth Kolla on extracting flame thickness and conditional scalar dissipation rate statistics. These statistics—which were obtained from recent direct numerical simulations (DNS) of a hydrogen/air premixed temporal slot jet flame in intense shear-driven turbulence—aid in determining turbulent burning velocity and understanding the effects of intermittency of the scalar dissipation rate in reactive scalars, particularly in turbulent premixed flames. The intermittency statistics require resolutions down to the smallest turbulence and flame scales, as well as a detailed representation of the chemical mechanism—information readily and uniquely available from DNS. This research is part of an ongoing collaboration with Professors Chung K. Law of Princeton University and Evatt Hawkes at University of New South Wales.
Kristine Dalen, Student, Technical University of Denmark
Host: Lyle Pickett
During her four months at the CRF, Kristine Dalen expanded on her current research by studying soot formation and radiative emission in a constant-volume, high pressure combustion vessel under conditions relevant to diesel engines. Kristine contributed to the setup of a high-speed soot extinction diagnostic that was used to obtain quantitative measurements of soot volume fraction. She also participated in experiments using an imaging spectrometer to measure radiation along the centerline of the spray flame. The quantitative soot and radiation measurements will provide valuable targets to researchers developing computational tools for designing advanced internal combustion engines.
Utsav KC, University of Texas at Austin
Host: Robert Barlow
Bringing a spectrometer from his university for highly resolved measurements of spontaneous Raman scattering spectra, Ustav KC collaborated with CRF staff to measure Raman spectra of several small hydrocarbon fuels and combustion intermediates, including methane, dimethyl ether, ethane, and ethylene, over a range of temperatures. This work involved using the gas flow systems and gas heater in the Turbulent Combustion Laboratory and will help to extend Raman scattering techniques to allow quantitative measurement of all major species in turbulent flames burning a wide range of fuels.
Alex Krisman, University of New South Wales, Australia
Host: Jackie Chen
Following in the footsteps of his mentor Professor Evatt Hawkes, a former CRF postdoc, PhD student Alex Krisman joined Ankit Bhagatwala and Jackie Chen to conduct direct numerical simulation (DNS) and modeling of turbulent combustion relevant to diesel engines. His research, which focuses on DNS of lifted dimethyl ether jet flames at elevated pressure and with a heated co-flow, aims to reveal interesting chemistry-turbulence dynamics associated with diesel lift-off stabilization in autoignition intermediates upstream of the lift-off location. After mining the DNS data to develop stochastic field models for large-eddy simulation, Alex will be presenting preliminary results of the collaborative research at the upcoming 9th Asia-Pacific Conference on Combustion in South Korea in May 2013.
Maarten Meijer, Eindhoven University of Technology, The Netherlands
Host: Lyle Pickett
To complement his studies at university, Maarten Meijer used a variety of optical diagnostics at the CRF to help advance research on the spray characteristics of multi-hole fuel injectors and internal combustion engine fuel-air mixing. Specifically, Maarten used Rayleigh scattering, Mie scattering, and schlieren imaging. Maarten also applied a unique thermocouple array to quantify temperature variations and the boundary layer thickness in Sandia’s constant-volume combustion vessel.
Aziz Nanthaamornphong, University of Alabama
Hosts: Damian Rouson and Karla Morris
During his time at the CRF, Aziz helped refactor the laser-induced incandescence (LII) code developed by Dr. Hope Michelsen with the goal of creating an open-source LII software package for the combustion research community. This software package will help researchers understand how mass and energy exchange (interplay between annealing, oxidation, conduction, sublimation, radiation, and thermionic emission) affects the measured incandescence emitted from irradiating soot particles with intense laser light. Sandia will host the main repository for this software, which provides all the infrastructure required to develop a collaborative model that can be extended, modified, and used by different researchers.
Jens Prager, formerly, University of Heidelberg, Germany
Host: Habib Najm
Postdoc Jens Prager was involved in numerous projects while focused on computational modeling of reacting flow at the CRF from 2007 until January 2013. A major emphasis was developing massively parallel low Mach‒number reacting flow codes in rectangular and axisymmetric geometries. He also conducted computational studies of edge flames and laminar jet flames with complex hydrocarbon fuels and studied flame structure using computational singular perturbation analysis. In addition, Jens worked on uncertainty quantification in jet flame computations and in chemical ignition, focusing on the role of parametric correlations resulting from rate rules and experimental fitting. Broadly, his work has advanced predictive modeling of flames with complex hydrocarbon fuels.
Thomas Sharples, Heriot Watt University, Edinburgh, Scotland
Host: Dave Chandler
As part of a collaboration with Dr. Ken McKendrick and Matthew Costen of Heriot Watt University, graduate student Thomas Sharples studied the dynamics of electronically excited state collisions while at the CRF—work that aims to improve understanding of quantitative laser diagnostics and the details of collisional energy transfer. Specifically, Thomas came to learn how to use the equipment at the CRF so that he could help develop apparatus for performing similar experiments in Scotland.
Johannes Trost, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
Host: Paul Miles
As part of a collaborative project, student visitor Johannes Trost helped identify, characterize, and evaluate various fluorescent tracers to enable measurements of in-cylinder equivalence ratios when using diesel primary reference fuels. The initial characterization of the tracer photophysics was performed at facilities in Erlangen, and the first measurements in an operating engine were performed in the CRF’s optical engine facilities.
Julia Warkentin, University of Bielefeld, Germany
Host: Nils Hansen
As a student visitor, Julia Warkentin performed experiments on the detailed chemistry of flames fueled by iso-pentanol, a next-generation biofuel. Data obtained from simple model flames revealed the chemical pathways on the high-temperature oxidation pathways of this emerging biofuel. The experimental results served as benchmarks for the development of a predictive detailed chemical kinetic model.
Ruigang Zhou, University of Cambridge, UK
Host: Jonathan Frank
Working in the Advanced Imaging Laboratory, Ruigang Zhou conducted experiments with Jonathan Frank to improve understanding of turbulence-chemistry interactions in stratified combustion, a process relevant to many practical combustion devices that have local variations in fuel/oxidizer mixtures. This work is part of a collaboration with Simone Hochgreb of Cambridge that involves conducting complementary measurements at Sandia and Cambridge. For this, Cambridge sent to the CRF a stratified combustion burner that serves as a target burner for the Turbulent Nonpremixed Flame Workshop, an open and ongoing international collaboration among experimental and computational researchers in turbulent combustion.