In the present study, non-intrusive technique for the concentration measurements of
soot particles formed within the flames was experimentally investigated. In the previous
investigations, the light extinction technique has been widely used to measure the
concentration of soot particles produced from the combustion process since its optical
system consists of less expensive optical components and can be easily configured
compared to other non-intrusive optical measurement systems. Although the light extinction
technique is one of the most common measurement methods for soot particle concentration
due to its ease of use and cost competitiveness, there exists some disadvantages that should
be overcame. For example, only the concentration of soot particles which is integrated
along the line path of light source can be calculated using the conventional light extinction
technique.
The local concentration and distribution of soot particles formed within the flame
(that can not be obtained from the conventional light extinction technique) are factors for a
qualitative flame analysis (that can influence the flame temperature through radiative heat
transfer process and thus the flame extinction). To overcome such disadvantages of the
conventional light extinction method, the full field light extinction apparatus (that enables
us to obtain the spatial distribution and local concentration of soot particle within the
flames) was developed and implemented as part of this study. The 3 point abel inversion algorithm was also coded using a Fortran software to recover the spatial distribution and
concentration of soot particles from the projected values obtained from the CCD camera.
The dimensionless extinction constant of soot particle is a critical parameter that is
inevitably needed to the concentration measurement of particles. In this thesis, the
dimensionless extinction constant of soot particles produced from a small laminar flame
burning kerosene was measured at the wave length of 635 nm. Measurements were fulfilled
with a Transmission Cell (TC) in which simultaneous gravimetric sampling and light
extinction techniques were employed. The measured dimensionless extinction constant for
kerosene fuel was 11.3 ± 0.3. To obtain the local concentration and distribution of soot
particles formed within the flame, laser-backlit images produced with a 635 nm light source
were captured using a CCD camera built in the full field light extinction apparatus and
digitized. From digitized laser-backlit images, projected values along the path line were
determined and deconvoluted using a 3 point abel inversion technique. The abel inversion
analysis clearly indicates that the spatial distribution of soot particles within the flame can
be faithfully reconstructed from the projected light extinction image captured by a CCD
camera.