Constraints of two-colour TiRe-LII at elevated pressures
- 153 Downloads
The main objective of this work is to investigate the influence of high-pressure conditions on the determination of primary particle size distributions of laser-heated soot particles using pyrometrically determined temperature decays. The method is based on time-resolved laser-induced incandescence measurements carried out at two different wavelengths (two-colour TiRe-LII). The LII signals are transferred into a particle ensemble averaged (effective) temperature using Planck’s thermal radiation formula. Assuming that all particles within the size distribution possess a unique temperature at the end of the laser pulse, the size distribution can be determined by numerically simulating the measured temperature decay. From our investigations, for pressures up to a few bars it is obvious that this strategy can be successfully applied if standard laser pulses of nano-second duration are used as an LII-excitation source. At higher pressures the time scales of heat conduction are decreased to such an extent that a unique temperature for all particles within the ensemble cannot be assumed at the end of the nano-second laser pulse. However, further investigations show that the presented two-colour TiRe-LII technique can be successfully adopted under technical high-pressure conditions as well, if the pulse duration of the TiRe-LII-excitation source is reduced into the pico-second range.
KeywordsLaser Pulse Soot Particle Particle Heating Particle Ensemble Unique Temperature
Unable to display preview. Download preview PDF.
- 5.D.L. Hofeldt, SAE Tech. Paper Ser. No. 930079 (1993), p. 45 Google Scholar
- 6.N.P. Tait, D.A. Greenhalgh, Ber. Bunsenges. Phys. Chem. 97, 1619 (1993) Google Scholar
- 13.D.R. Snelling, G.J. Smallwood, I.G. Campbell, J.E. Medlock, Ö.L. Gülder, in Proc. Congr. Advanced Non-Intrusive Instrumentation for Propulsion Engines (AGARD, Neuilly, 1997) Google Scholar
- 20.H.A. Michelson, F. Liu, B.F. Kock, H. Bladh, A. Boiarciuc, M. Charwath, T. Dreier, R. Hadef, M. Hofmann, J. Reimann, S. Will, P.-E. Bengtsson, H. Bockhorn, F. Foucher, K.-P. Geigle, C. Mounaïm-Rousselle, C. Schulz, R. Stirn, B. Tribalet, R. Suntz, Appl. Phys. B 87, 503 (2007) ADSCrossRefGoogle Scholar
- 26.F. Liu, D.R. Snelling, G.J. Smallwood, in Proc. IMECE2005, ASME Int. Mechanical Engineering Congr. Expos., 5–11 November 2005, Orlando, FL, USA (2005), pp. 355–364 Google Scholar
- 30.K. Schäfer, E. Lax (eds.), Landolt-Börnstein, II2a, 6th edn. (Springer, Berlin, 1960), pp. 1–30 Google Scholar
- 33.S.C. Lee, C.L. Tien, Proc. Combust. Inst. 18, 1159 (1981) Google Scholar