Engine diagnosis using laser technology

Non-intrusive optical diagnostic techniques are particularly suitable for obtaining precise measurement of gas temperatures in the combustion chamber.

Gilles Bruneaux Energy Application Techniques Division gilles.bruneaux@ifpen.fr	Gabrielle Tea Energy Application Techniques Division gabrielle.tea@ifpen.fr

The development of increasingly efficient and ever cleaner engines requires precise measurement of gas temperatures in the combustion chamber since the temperature has a direct impact on the formation of the air-fuel mixture, self-ignition and pollutant formation. However measurement is made difficult by the engine environment. What's more, the very marked temperature sensitivity of the phenomena studied demands a very high level of precision.

These non-intrusive optical diagnostic techniques are particularly suitable for obtaining information of this type. Numerous studies have demonstrated the potential of laser induced fluorescence for temperature measurement. However, its application in a diesel jet, characterized by marked temperature gradients, is still a major challenge.

It is against this background that IFPEN has developed this technique in a high-pressure cell enabling the thermo-dynamic conditions of the diesel engine to be reproduced. An original methodology has been implemented to simultaneously optimize the experimental set-up, image processing and measurement error, as well as quantify the latter.

The results obtained have proved to be highly satisfactory. Temperatures of up to 700 K have been measured, with a precision of ±20K and a systematic error of less than ±30K. A promising first step has therefore been taken and it will be necessary to continue developing the technique to include simultaneous temperature and fuel and oxygen concentration measurements, in order to gain an even more precise understanding of the physical phenomena at play.

Image of the temperature in a non-reactive diesel jet obtained by laser induced fluorescence.

Publications

• G. Tea, G. Bruneaux, J. T. Kashdan, C. Schulz, Unburned gas temperature measurements in a surrogate Diesel jet via two-color toluene-LIF imaging, Proceedings of the Combustion Institute, 33 (2011) 783-790.

>> See also IFPEN Publications database