NON-PREMIXED TRANSVERSELY OSCILLATING PLANE JET FLAMES IN CO-FLOWING AIR STREAMS

Reuben Mwanza Kivindu ； Rong Fung Huang ； Ching Min Hsu

《Journal of Marine Science and Technology》 26卷2期 (2018/04) Pp. 194-206

https://doi.org/10.6119/JMST.2018.04_(2).0007

摘要

This study examined the flame behavior and thermal structure of non-premixed transversely oscillating plane jet flames. A V-shaped fluidic oscillator was installed with deflection plates to merge alternately issued pulsating jets, and induce transverse oscillations of the merged jet. Co-flowing air streams were supplied with two planar air jets arranged next to the burner. Isothermal jet frequencies were detected using single hot-wire anemometry. Flame behaviors were studied using photographic techniques. Flame temperatures were measured using a fine-wire type-R thermocouple, and combustion concentrations of products were measured using a gas analyzer. The Strouhal number for the transversely oscillating jet shows an asymptotic value of 0.188. Three flame modes exist in the domain of the jet Reynolds number Re and the co-flow air Reynolds number Re_a: attached flame, transitional flame, and lifted flame. At Re ＜ 1204, the axial location of the maximum flame width decreases as Re_a increases, while at Re ＞ 1204, the axial location of the maximum flame width increases as Re_a increases. As Re_a increases, the flames become thinner, the maximum flame width decreases, and the maximum flame temperature increases. Co-flow air Re_a of 846 produces higher flame temperatures by approximately 100°C compared with the co-flow air Re_a of 445. The analysis reveals that high velocity co-flow air results in better combustion performance when compared to low velocity co-flowing air. The combustion characteristics of the transversely oscillating plane jet flames improved significantly, especially with high velocity co-flow air due to the enhanced jet turbulence, entrainment, and mixing.

關鍵字

oscillating jet flame ； fluidic-oscillator ； flame behavior ； co-flowing air