Simultaneous phosphor and CARS thermometry at the wall–gas interface within a combustor

详细信息    查看全文

• 作者：J. Brü ; bach ; M. Hage ; J. Janicka ; A. Dreizler
• 关键词：Thermometry ; Thermographic phosphors ; CARS ; Thermal boundary layer
• 刊名：Proceedings of the Combustion Institute
• 出版年：2009
• 出版时间：2009
• 年：2009
• 卷：32
• 期：1
• 页码：855-861
• 全文大小：185 K

文摘

Phosphor thermometry and vibrational coherent anti-stokes Raman spectroscopy (CARS) were applied simultaneously to examine gas–solid interfaces in a generic combustor. For this purpose, an internally air-cooled obstacle was installed within an optically accessible, pressurized combustion chamber. During the operation of a turbulent, swirled n-heptane flame, the obstacle’s surface temperature and the surface-normal gas temperature distribution were measured. The surface temperature was determined by Thermographic Phosphors, materials whose phosphorescence decay times depend on their temperature. Following a pulsed UV laser excitation (355 nm), the 659 nm emission band of Mg₄FGeO₆:Mn was monitored by a photomultiplier tube.

Non-invasive temperature measurements in the flue gas region of the n-heptane spray flame near the surface were performed pointwise by vibrational CARS of diatomic nitrogen. Beams from a frequency doubled Nd:YAG laser (532 nm) and a modeless broadband dye laser (607 nm) were phase-matched within a surface-parallel, planar BOXCARS configuration. This allowed gas phase thermometry as close as 30 μm to the surface.

The thermal boundary layer and wall temperature measurements were consistent with each other. This demonstrates the potential of spectrocopic techniques to study gas–solid interfaces with high temporal and spatial resolution. Using the interior surface temperature within the cooling channel measured by a thermocouple, the heat flux through the wall and the local heat transfer coefficient at the front side of the obstacle were estimated.