Flamelet based analysis of non equilibrium effects and No-formation in turbulent hydrogen diffusion flames
32nd Joint Propulsion Conference and Exhibit, 1996, Florida, Amerika Birleşik Devletleri, 1 - 03 Temmuz 1996, ss.1-11, (Tam Metin Bildiri)
- Yayın Türü: Bildiri / Tam Metin Bildiri
- Doi Numarası: 10.2514/6.1996-3033
- Basıldığı Şehir: Florida
- Basıldığı Ülke: Amerika Birleşik Devletleri
- Sayfa Sayıları: ss.1-11
- Orta Doğu Teknik Üniversitesi Adresli: Evet
Özet
The prediction of thermal JVO-formation in turbulent hydrogen-air diffusion flames is studied using the laminar flamelet concept. With this concept, which is in principal valid for fast chemical processes, the mean thermo-chemical quantities in the turbulent flame are obtained by appropriately averaging the scalar versus mixture fraction profiles in laminar counterflowing flames (flamelets). Each of the laminar flamelets is subject to a different fluid dynamic stretch rate, which quantifies the state of non-equilibrium. This stretch rate has to be associated with its turbulent (averaged) counterpart to obtain the mean quantities from the instantaneous laminar flame data. There is, however, no absolute certainty as to which averaged turbulent quantity should be associated with the laminar flamelet stretch rate; the scalar dissipation rate or one of the strain rates. This question is addressed by analysing scaling behavior of the NO emission index with jet exit parameters. Results imply that the scalar dissipation rate is the only parameter with which experimentally established NO scaling behavior can be predicted. Also detailed comparisons between flamelet based predictions and measurements of temperature, major species and NO for diluted turbulent hydrogen diffusion flames are performed. The results of these comparisons, regarding non equilibrium effects and differential diffusion effects, are in line with the EINOx analysis.