확산 화염 내 생성된 그을음 입자의 농도 측정에 관한 연구

Abstract

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.