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This paper presents a method to invert the two-dimensional distribution of a temperature and volume concentration of soot particles from color images. By using numerical simulation, the temperature field and particle volume-concentration field of a non-uniform soot flame are simultaneously reconstructed using the wide-response spectrum of a color CCD camera without adding monochromatic filters. The influence of number of cameras, error of camera position angle, measurement noise and different reconstruction algorithms on measurement accuracy are analyzed. The numerical-simulation results demonstrate that camera-position angle errors play a crucial role in the reconstruction accuracy. In addition, increasing the number of cameras can improve the reconstruction result accuracy. Compared with the least squares algorithm, the Tikhonov-regularization algorithm has a stronger anti-noise ability and can resist 39 dB of noise. The conclusions obtained in this paper are helpful to guide following experimental studies. [ABSTRACT FROM AUTHOR]

The magnetic effect on soot properties in ethylene inverse diffusion flames (IDF) was investigated in this study. The investigation involved the use of high-resolution transmission electron microscopy analysis (HRTEM), Raman spectroscopy analysis, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction spectroscopy (XRD) to examine the nanostructure and graphitization degree of soot collected from flame exhaust gas at various height above burner surface (HAB) under both magnetic and non-magnetic conditions. Increasing the magnetic flux density resulted in modifications to soot properties. When the sampling height was HAB = 4 cm, increasing magnetic flux density resulted in longer fringe lengths, lower fringe tortuosity, less amorphous carbon content and surface oxygen content for the collected soot from flame exhaust gas. These results indicated higher graphitization degrees, which may be attributed to longer residence time and oxidation of soot particle in flames. Moreover, when the sampling height increased from HAB = 4 cm to 6 cm under non-magnetic condition, the nanostructure of soot in the flame exhaust gas was more organized, possible due to the oxidation of soot at the region between HAB = 4 and 6 cm region. However, with the magnetic field on, the crystalline structure of soot in the flame exhaust gas became increasingly disordered as the sampling height increased. This suggested that the soot may also be affected by the magnetic effects in addition to oxidation at the region between HAB = 4 and 6 cm region. The magnetic effect could trigger the transformation of graphitic carbon to amorphous carbon in soot particles as they passed through the magnetic field. With more elaborated magnetic fields, the magnetic effect on soot could contribute to strategies controlling soot emissions and removal. [ABSTRACT FROM AUTHOR]

• Soot inception limits and its difference in coflow flames are interpreted in C/O ratio space. • Effects of Z st on soot inception are studied using kinetics analysis in C/O ratio space. • The position of chemiluminescence in C/O ratio space and the effect of Z st on it are evaluated. • Considering the low-emission combustion technology, oxy-combustion. This study investigates soot inception limits of laminar coflow diffusion flames in the carbon-to-oxygen atom (C/O) ratio space, as well as the mechanism of flame structure affecting soot inception. And chemiluminescence characteristics in flames are evaluated. Oxy-ethylene flames with the same adiabatic flame temperature (2500 K) and different stoichiometric mixture fractions (Z st , 0.3–0.6) are investigated by relocating CO 2 from oxidant to fuel. The position of soot inception and the chemiluminescence of CH*, C 2 *, and CO 2 * are measured by a hyperspectral imager. A numerical model with a detailed kinetic mechanism is used to obtain the temperature and gas-phase species concentration. The results prove that the critical C/O ratio favorable for soot inception is 0.53, and the critical temperatures on the flame centerline and sheet are 1322 K and 1632 K, respectively. The comparatively low temperature on the flame centerline can cause soot inception, as the polycyclic aromatic hydrocarbons (PAHs) concentration and residence time can guarantee the collision and cluster formation of PAHs. Although fuel pyrolysis is promoted on the flame sheet, oxygen-containing species dilutes the concentrations of fuel pyrolysis products and PAHs to limit soot inception, necessitating high temperatures for chemical bond formation. Furthermore, the mixture fraction, local C/O ratio, and net reaction and production rate are calculated, and the key reaction paths are also identified. The results demonstrate that the increase of Z st achieves the suppression of soot inception by lowering the formation of benzene and PAHs in the high C/O ratio (>0.5) zone, improving the oxygenation in the low C/O ratio (<0.5) zone, and compressing the C/O ratio space favorable for soot formation. Meanwhile, the (CH* and C 2 *) chemiluminescence zone with a C/O ratio of roughly 0.5 exists in the flame. With Z st increases, the CH* and C 2 * chemiluminescence diminishes at the flame root and enhances downstream, whereas CO 2 * chemiluminescence remains unaltered. [ABSTRACT FROM AUTHOR]

This paper proposes a hyperspectral imaging technique for capturing radiative images at a high temporal–spatial resolution, for the purpose of spectrally visualizing the instantaneous combustion behaviors of single coal particles. We initially use a hyperspectral imaging device to record the combustion processes of two types of single pulverized coal particles on a McKenna flat-flame burner. From the snapshot images captured by the device, we observe the combustion processes, ignition characteristics, flame morphologies, and sizes of the two single coal particles. The observations indicate that the two single coal particles undergo volatile release/combustion and char ignition/oxidation during the luminous combustion process; moreover, both particles exhibit homogeneous ignition characteristics under the experimental conditions. Furthermore, based on the spectral radiative intensity images obtained via the device, the soot temperature and volume fraction images of the two single coal particles in the envelope flame are obtained at different burning times. Thereafter, the influences of the combustion behaviors and soot formation mechanisms on the distribution rules of the soot temperature and concentration at different combustion periods are discussed. Finally, the temperature and apparent spectral emissivity values of the two single char particles during the char oxidation process are also calculated to analyze their combustion behaviors. The results show that the temperature changes within a relatively narrow range with respect to the burning time during the oxidation stage, whereas the spectral emissivity continues to increase with the oxidation of chars and subsequently decreases. [ABSTRACT FROM AUTHOR]