Experimental study of unsteady laminar and turbulent flame propagation in an enclosure by Rayleigh scattering
- Consiglio Nazionale della Ricerche, Naples (Italy). Ist. Motori
- Lawrence Berkeley Lab., CA (United States)
The Rayleigh scattering technique has been used to investigate the flame structure of unsteady propane/air flames propagating under quiescent and turbulent conditions initiated by three ignition methods: (1) conventional spark plug (2) pulse jet combustion (PJC) and (3) Pre-Chamber ignition (PCI). The Rayleigh signal obtained for the laminar cases are all characterized by a sharp transition associated with the large density change which occurs as leading flame front of the expanding flame kernel crosses the measurement point. This indicates that the local flame structures are independent of the ignition source and may be characterized as flamelets. The maximum burning rates deduced from the pressure records show that PJC and PCI increases the burning rate from two to three times above that of conventional spark ignition. The Rayleigh scattering signal obtained for the turbulent cases are also characterized by sharp transition. The wrinkled laminar flamelet model, therefore, provides a valid description of the flame structures for all these unsteady flames. For a given equivalence ratio, the maximum turbulent burning rate deduced for the three turbulent cases with different ignition sources are similar. This suggests that while PJC and PCI enhances burning rate when conditions in the chamber are quiescent, the enhancement is not significant when turbulence fluctuations are present. The PJC and PCI, however, are capable of igniting leaner conditions than the spark plug. This may be due to the injection process which initially disperses ignition sites to a larger volume at a faster rate.
- Research Organization:
- Lawrence Berkeley Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 10103695
- Report Number(s):
- LBL-32928; CONF-9210213-4; ON: DE93002570
- Resource Relation:
- Conference: 1992 Combustion Institute fall meeting of the western states section,Berkeley, CA (United States),12-13 Oct 1992; Other Information: PBD: Sep 1992
- Country of Publication:
- United States
- Language:
- English
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