Combustion Physics

Lund University

Description of our activities

At the Division of Combustion Physics research and education is carried out in the fields of combustion diagnostics and chemical calculations of combustion phenomena.

Diagnostic methods are needed to build knowledge of how combustion works. At Combustion physics optical measurement methods are developed, in the vast majority of cases based on the use of lasers. A laser is a special light source which can generate light with unique characteristics. Ordinary light from the sun or a light bulb is made up of a large number of different wavelengths (colors) and the light is issued in all directions. Laser light is generated on esentially one single wavelength and is shaped in a beam, which means that one, using optical lenses, effectively can direct and shape this into many ways. In addition, a great advantage with laser light is the very high peak power obtainable.

What do we use the laser light for? Well, by sending a laser beam through a region of interest, you can interact with the molecules or particles in this region. This perturbation often causes a new light emission, this time originating from the molecules or particles themselves, a light emission that can be measured and interpreted in the form of, for example, temperature or species concentrations. Interaction between the laser light and the matter will also affect the laser beam characteristics. This is used in some techniques and hfor these the information is read from a measurement of these properties before and after passage through the region of interest. You can learn more about our measurement methods here.

The advantage of optical methods to alternative ones in which measurement probes are used, is that they are non-intrusive. Certainly we disrupt a number of molecules or particles in the measurement region, but it happens in as short periods of time and to such a low extent that we, as a rule do not affect the combustion process. We thus have the ability to measure without disturbing what we measure - a task that is quite difficult in many cases. An obvious drawback of optical techniques is that they require optical access to the area we want to measure. This is no problem in an ordinary test flame in a laboratory, but studies of the combustion process in a Diesel engine require specially designed engines equipped with special windows.

With our measurement methods, we can measure for instance temperatures, species concentrations, particle sizes and flow rates. In addition to giving us a direct understanding of a combustion process, such data is very useful to validate both chemical and fluid dynamic models. At our division one activity involves development of chemical computational techniques to simulate combustion processes in, for example, a car engine. As hundreds of chemical reactions takes place simultaneously during a typical combustion process, these models can be very complicated. Much effort is thus directed towards finding ingenious ways of reducing the number of elementary reactions without significantly changing the quality of the predictions. One creates so-called reduced mechanisms that can describe the complete mechanism sufficiently well. Measurements with our diagnostic methods are used to validate models in different contexts. It can be anything from detailed studies of a test flame to direct measurements inside a Diesel engine.

In addition to research we conduct education in these areas. We have three courses at LTH and take part in courses run by the national centre CeCOST, in which we are a part.