Investigation of Soot Formation in Laminar Diesel Diffusion Flame by Two-Color Laser Induced Incandescence

Laser-Induced Incandescence and Smoke Point Measurements to Characterize the Sooting Propensity of Biodiesel Diffusion Flame

ASME 2010 4th International Conference on Energy Sustainability, Volume 2 ◽

10.1115/es2010-90202 ◽

2010 ◽

Author(s):

Michael Tran ◽

Trinh Pham

Keyword(s):

Diffusion Flame ◽

Combustion Zone ◽

Soot Formation ◽

Smoke Point ◽

Band Pass Filter ◽

Pass Filter ◽

Substantial Impact ◽

Yag Laser ◽

Soot Particles ◽

Laser Induced Incandescence

Combustion of biodiesel is rapidly expanding around the world, mainly for its significant reduction of emissions such as soot particulates. The presence of carbonaceous soot emitted indicates a reduction in efficiency of practical combustion systems. In addition, sub-micron soot particles can have substantial impact on the environment and human health. Common emission studies of neat and blends of biodiesel and diesel fuels have been investigated using compression ignition engines and capturing soot particles in the post-combustion zone. However, soot particles produced in the primary combustion zone can greatly influence the products in the post-combustion zone. To study soot formation in the primary combustion zone, laser diagnostic is performed on a laminar diffusion wick lamp. In this paper, the sooting propensity of various blends of soybean biodiesel and Ultra Low Sulfur Diesel (ULSD) fuels are investigated using both a traditional ASTM D-1322 standard smoke lamp and modern Laser-Induced Incandescence (LII) technique. Laser excitation is achieved using a pulsed Nd: YAG laser operating at 532nm wavelength. Although ultraviolet and infrared spectra can be used, the choice of an Nd: YAG laser operating at the second harmonic wavelength is preferred because interference from excitation of polycyclic aromatic hydrocarbons (PAHs) and the C2 Swan band can be reduced. A fast-gate Intensified Charge Coupled Device (ICCD) camera and a 450nm narrow band-pass filter are used to detect the spatially resolved LII signal. The qualitative LII signal provides the soot profile of different volume mixtures of biodiesel and diesel diffusion flame. Many researches report show reduction in soot particles emitted in the exhaust when biodiesel is used as a blend in compression ignited engines. The contribution of this research is to investigate whether similar sooting characteristics can be seen in the primary combustion zone by making measurements in the proximity of the flame front. In general, the LII signals and smoke point measurements show a decrease in soot particles produced when blending ratios of 25% biodiesel – 75% diesel (by volume) are used. One limitation of using the ASTM standard wick lamp is flame instability at higher blending ratios due to the increases in carbon deposit on the wick, which reduces the fuel vaporization rate. Therefore, smoke point measurement for blending ratios above B25 is not accurate since the flame height is not stable; hence, future experiments rely on LII technique to characterize soot emission properties. In order to perform LII laser diagnostics using higher blending ratios, comparison between smoke point measurements and LII signals will be characterized in this report using lower blending ratios.

Download Full-text

Experimental Analysis of Soot Formation in Sooting Diffusion Flame by Using Laser-Induced Emissions

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2056536 ◽

2005 ◽

Vol 128 (2) ◽

pp. 241-246 ◽

Cited By ~ 26

Author(s):

Kazuhiro Hayashida ◽

Kenji Amagai ◽

Keiji Satoh ◽

Masataka Arai

Keyword(s):

Diffusion Flame ◽

Soot Formation ◽

Emission Spectra ◽

Laser Wavelength ◽

Relative Location ◽

Fluorescence Image ◽

Laser Induced Incandescence ◽

Polycyclic Aromatic ◽

Fluorescence Radiation ◽

The Individual

Two-dimensional images of OH fluorescence, polycyclic aromatic hydrocarbons (PAHs) fluorescence, and laser-induced incandescence (LII) from soot were measured in a sooting diffusion flame. To obtain an accurate OH fluorescence image, two images were taken with the laser wavelength tuned to (“on”) and away from (“off”) the OH absorption line. An accurate OH fluorescence image was obtained by subtracting the off-resonance image from the on-resonance image. For the PAH fluorescence and LII measurements, temporally resolved measurements were used to obtain the individual images; the LII image was obtained by detecting the LII signal after the PAH fluorescence radiation had stopped and the PAH fluorescence image was obtained by subtracting the LII image from the simultaneous image of PAH fluorescence and LII. Based on the obtained images, the relative location of OH, PAH, and soot in the flame was discussed in detail. To investigate the PAH size distribution in a sooting flame using LIF, an estimation strategy for PAH size is proposed. Emission spectra were measured at several heights in the flame using a spectrograph. Since the emission wavelength of PAH fluorescence shifts toward longer wavelengths with increasing PAH size, the main PAH components in the emission spectra could be estimated. The results suggest that PAH grows and the type of PAH changes as the soot inception region was approached. Near the soot inception region, we estimated that the PAHs, which have over 16 carbon atoms, mainly constituted the emission spectrum.

Download Full-text