Combustion Visualization

Exploring Combustion Using Advanced Imaging Techniques

Fig. 1. The GM diesel test cell is shown with vehicle exhaust aftertreatment hardware (diesel particulate filtration and diesel oxidation catalyst) along with other advanced technology—such as a variable geometry turbocharger, cooled exhaust gas recirculation and a common-rail fuel injection system.

Fig. 2. Two-dimensional image of hydrogen combustion OH chemiluminescence.

Fig. 3. Combustion visualization of diesel fuel from inside the engine combustion chamber using visible light soot radiation.

Detailed information about combustion is needed to make advances that will meet stringent U.S. Environmental Protection Agency emissions standards while maintaining high fuel efficiency and power density.

Information such as soot formation, presence of intermediate combustion reaction species, in-cylinder mixing, fuel spray characterization and combustion temperature are explored using advanced imaging techniques. Tools such as state-of-the-art endoscopes, advanced cameras and fiber-optic instruments are also used. Figure 1 shows a test cell configured for data collection.

Using real-world engines and technologies, these projects provide detailed combustion information, giving automobile and truck manufacturers the data they need to build environmentally-friendly vehicles.

Manufacturers are exploring non-traditional combustion regimes that produce low-temperature combustion, allowing for very low NO_x (nitrogen oxides) formation during the combustion process, which significantly eases the burden on exhaust aftertreatment systems.

Argonne's Combustion Research Projects

Combustion Imaging Techniques. Using an endoscope, this technique provides a two-dimensional look at combustion characteristics, such as soot radiation data for soot volume fraction and soot temperature, or chemical information for combustion species emission in the visible wavelength band.

In addition, information such as ignition location and timing, and spray/air interactions are measured. Figure 2 shows a two-dimensional image of hydrogen combustion visualized by using hydroxyl radical (OH*) chemiluminescence inside a running engine. The image provides qualitative information about hydrogen combustion intensity, location and temperature.

OH*/CH* Spectroscopy. Fiber optics, such as OH*/CH* (hydroxyl radical/methylidyne radical) spectroscopy, can capture very high resolution measurements of the radiation emission of excited chemical species in the combustion reaction zone. This allows for a combustion temperature estimation to be calculated as a highly resolved function of time, providing a temperature profile of the combustion event from beginning to end.

Figure 3 shows diesel combustion from inside the engine combustion chamber using visible light soot radiation. The injector tip and injection sprays can be clearly seen, along with the combustion reaction. Images like this can be analyzed to calculate soot volume fraction and soot radiation temperature.

Funding

This work is supported by the U.S. Department of Energy’s Vehicle Technologies Program under Gurpreet Singh.

December 2009