Flame Spectra of a Turbulent Liquid-Fueled Swirl-Stabilized Lean-Direct Injection Combustor

摘要

Flame spectra within theUV/visible-light range aremeasured for a turbulent, liquid-fueled, swirl-stabilized, lean-ndirect injection combustor. The flame spectra are quite similar to those of lean premixed combustion, which can benattributed to the small droplet size and fast fuel/airmixing. Broadband background emissions around 431 nm,whichnmainly consist ofnu0001n2 chemiluminescence, are found to be self-similar with wavelength for both stable and unstablencombustion.Chemiluminescence from u0001,nu0001, and u0001n2 is found to be a nonlinear function of the airflowrate, thenequivalence ratio, preheat temperature, and pressure. Procedures for the determination of the instantaneous heatnrelease rate and equivalence ratios along the flame front are developed. For both combustion instability and forcednflame responses, the prediction errors are within 2.0%in themean heat release rate, themean air consumption rate,nand the mean equivalence ratio. The assumption that chemiluminescence is proportional to the instantaneous heatnreleaser rate is generally invalid. Probably the proportionality is valid only in the weakly turbulent or wrinklednflamelet region in the absence of equivalence ratio variations and strong acoustic oscillations.