Measurement of transient soot emissions by means of full stream, in-situ laser induced incandescence

The Laser Induced Incandescence technique (LII) is an emerging optical method for reliable spatially and temporally resolved measurement of soot concentration and potentially for monitoring primary soot particle size. Due to its origin [1], this method appears to be suitable for measurement of fast transient emissions from Diesel engines, which form the main fraction of total emissions during standardized test cycles[2]. Current existing commercial LII devices require modifications in the exhaust gas flow, dilution, or measure with a partial stream in a preconditioned cell [3, 4]. We present the results from the development of a single access in-situ LII setup for rapid measurement of soot during the combustion process of a Diesel production engine, suitable for direct full stream, measurements in the tail-pipe without needs of dilution or a sampling cell. Further, the issue of the optical window cleaning, temperature dependency of the LII signal due to the laser - tailpipe interaction and possible suppressing of disrupted emission signal by means of shifted time delay is addressed. Obtained and corrected LII results are further compared to commercially available devices for measurement of soot emissions.