Microcombustion at LSU

About the lab

Microcombustion at LSU focuses on research on combustion technologies and diagnostics.

- Premixed combustion and ignition phenomena (theory, experiments and simulations);
- Computational diagnostics for detailed reacting flow simulations (CEMA);
- Combustion with conjugate heat transfer and microcombustion;
- Limited view tomography in optical combustion diagnostics;
- Tunable diode laser absorption spectroscopy, focusing Schlieren imaging;
- Thermochemical energy conversion of alternative fuel sources (fuel reforming, gasification).

Other expertise:
- Materials processing for ceramic manufacturing and microfluidics (co-extrusion, embossing);
- Mechatronics & instrumentation.

Featured projects (3)

The DOE funded project “Microliter Fuel Characterization and Property Prediction” seeks to enable small volume (<20 μl), high throughput (>100 tests/device/month) measurements of transportation fuels and blends that are relevant to co-optimized fuels and engines. In this context, the ability to quantify the performance of a fuel in terms of autoignition metrics (e.g. octane number/sensitivity), combustion properties (e.g. flame speed) and physical properties (e.g. volatility and viscosity) is of significant interest. Predictions of fuel performance in a combustion engine require a link to be made between small volume measurements and combustion behavior of a fuel blend at engine relevant conditions.
Research on combustion with conjugate heat transfer focuses on phenomena that arise due to the interaction of a combustion zone with a conducting wall. Thermal interaction with a wall can change local combustion characteristics significantly. While cold walls impede combustion due to local quenching of reactions, flame stabilization by thermal anchoring along hot walls is based on the opposite effect.
Temperature measurements based on spectral radiation emitted from a surface are often limited by prior knowledge of the target and by the sensitivity of the detector. In this project, temperature estimates are obtained through a multispectral pyrometry method that does not require prior on surface emissivity or model calibration.

Featured research (32)

Within the area of combustion, externally heated microtubes have been introduced to study the combustion characteristics of fuels and fuel blends. Microreactors have advantages over other conventional fuel testing methods because of their potential to test small volumes (< 20 μl) at high throughput. In this work, a high-pressure microreactor is designed and implemented to test fuels up to a pressure of 20 bar where automated testing reduces test time substantially. The novelty of this device is its capability to operate at pressure exceeding the current state of the art of 12 bar. The combustion behavior of fuels is tested in an externally heated quartz tube, with a diameter less than the conventional quenching diameter of the fuel. The ultimate objective of the experiment is to investigate the impact of fuel on flame characteristics. The ability to reach engine relevant pressure conditions and its inherent small volume requirements make this device a potential candidate for measurements of laboratory transportation fuels and fuel blends. For initial validation, tests from an earlier intermediate pressure experiment with ethane/air and nitrogen mixtures are repeated. Chemiluminescence images are taken to evaluate the combustion characteristics in terms of the three classical flame regimes: weak flames, Flames with Repetitive Extinction, and Ignition (FREI) and normal flames. Previous results at intermediate pressure showed that as the pressure increases, the weak flame and FREI regimes shift towards lower velocities. Also, as dilution level increase (i.e. reducing oxygen concentration), the transition from the weak flame to FREI becomes less abrupt and is completely lost for marginal oxygen concentration. The objective of this study is to document flame dynamics at higher pressures.
This study investigates the impact of pressure and dilution on combustion behavior of C2H6/air/N2 mixtures within an externally heated micro-tube using both experimental and analytical techniques. Experiments are conducted for pressures up to 10 bar at multiple dilution levels and document three flame regimes, i.e. weak flames, FREI and normal flames. Characteristic temperatures for flame stabilization, as well as ignition and extinction are obtained by applying a novel thin filament pyrometry method (TFP), which uses a thin silicon carbide (SiC) filament that enables temperature measurements for both reacting and non-reacting cases. Results show a decrease of characteristic temperatures with increasing pressure, which can be partially compensated by a decrease of O2 content. Further, regime transitions occur at lower velocities as the pressure increases, whereas weak flame positions are insensitive to dilution at a given pressure. Predictions from an analytical model compare favorably with experimental results. The most prominent finding is that as dilution increases, the transition from weak flame to FREI becomes less abrupt and is completely lost for high dilution levels (i.e. low O2 content). Both experimental and analytical results indicate that the unstable FREI combustion regime does not exist at high dilution levels, i.e. weak flame and normal flame regimes are no longer clearly separated. As FREI correspond to a cyclic transition from an ignition zone to a propagating flame, results for highly diluted conditions are interpreted as a combustion regime where classical flame propagation ceases to exist.
Temperature measurements based on spectral radiation emitted from a target surface are often limited by prior knowledge of the emissivity of the surface. As an alternative, multi-wavelength pyrometry approaches, in which thermal radiation is evaluated at two or more wavelengths, allow both emissivity and temperature of the target surface to be estimated, as long as the emissivity function is known. In the present work, a 10-bit CMOS near-infrared machine vision camera is employed to the evaluation of temperatures along a thin filament calibration target through a variation of the multi-wavelength pyrometry technique, in which prior knowledge of the emissivity function is not necessary. Optical bandpass filters are used to selectively limit the wavelengths imaged by the camera. The low dynamic range limitation of the CMOS sensor is overcome by the application of the high dynamic range (HDR) imaging technique. Temperature estimates are obtained from the resulting HDR image through a multiband multi-wavelength pyrometry. Measurements obtained from the thermoelectric effect in a thin butt-welded K-type thermocouples are used to validate the results from pyrometry for temperatures from 800 K to 1400 K.
In this study, combustion characteristics of Primary Reference Fuels (PRFs: n-heptane/iso-octane mixtures) are investigated at atmospheric and moderate pressure in a microchannel exposed to a controlled temperature profile produced by a flat flame burner. Tests with stoichiometric PRF/air mixtures are carried out with inlet velocities ranging from5 to80 cm s−1. Three distinct combustion regimes are observed: weak flames, flames with repetitive extinction and ignition (FREI), and strong flames. Chemi-luminescence from excitedCH?radicals is captured by a machine vision camera at each set point. Photographic images of the observed flame structures are processed to identify the flame position as well as locations where ignition and extinction occur. The temperature at which each flame structure is observed is obtained in terms of the measured wall temperature profile since both are related to the axial position. Results for different fuel blends are compared showing that ignition and extinction temperatures of fuels are affected by the octane number, which is consistent with weak flame results from the literature.

Lab head

Ingmar Schoegl
  • Department of Mechanical Engineering
About Ingmar Schoegl
  • Ingmar Schoegl currently works at the Department of Mechanical Engineering, Louisiana State University. Ingmar does research in Mechanical Engineering with a focus on combustion and its applications.

Members (5)

Pawan Sharma
  • Louisiana State University
David Akinpelu
  • Louisiana State University
Veerendra Naralasetti
  • Louisiana State University
Dakota Hebert
  • Louisiana State University
Robert Frazee
  • Louisiana State University
Chris Breath
Chris Breath
  • Not confirmed yet

Alumni (8)

Mohsen Ayoobi
  • Wayne State University
Vinicius Sauer
  • California State University, Northridge
Girguis Sedky
  • Princeton University
Avishek Guha
  • Air Products and Chemicals Inc.