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The gas temperature fields of axisymmetric co-annular laminar diffusion ethylene flame jets in air and oxygen-enriched atmospheres were measured and visualized using large lateral shearing interferometry technique. Seven cases of reconstructed temperature fields were investigated using various compositions of fuel/oxidant with an average correction factor. The phase difference field were obtained using a fringe trace algorithm. A discrete Abel inversion process was adopted to resolve the refractive index distribution from the line-of-sight integrated data. The peak temperatures of the flame varied between 1980 K and 2050 K using air as the oxidant and increased to more than 2150 K when oxygen was added. Two separate high temperature zones, one located at the side edge of the flame, the other in the upper part of the flame around the centerline of the burner were observed in four of the seven instances of high mixture stoichiometry. The proposed methodology was verified to be suitable for the reconstruction of temperature distributions from the experimental measurement results. [ABSTRACT FROM AUTHOR]

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]

Effects of radiation reabsorption on the burning flux of freely propagating laminar premixed flames at atmospheric and elevated pressures were numerically investigated for CH 4 /O 2 /N 2 /CO 2 mixtures. Models with SNBCK 9 bands and 7 bands based on the spectral band lumping for H 2 O, CO 2 , CO and CH 4 were developed to improve the computational efficiency. It is found that the burning flux is promoted by the upstream radiation reabsorption and with increasing CO 2 concentration. Furthermore, with increasing pressure, radiation reabsorption first increases and then reduces the burning flux because of the corresponding increases of the reabsorption efficiency and the optical thickness, respectively. The blockage of radiation emission from the burnt mixture due to the increased optical thickness is dominant with the addition of the stronger radiative species CO 2 at higher pressures. Extensive computation further demonstrates that, compared with the benchmark case of 367 bands, the SNBCK 9 bands lumping retains good accuracy while substantially facilitates the computational efficiency. [ABSTRACT FROM AUTHOR]

A novel planar micro-combustor with four-corner entrances is proposed by considering high and uniform outer wall temperature distribution used in micro thermo-photovoltaic generator. For this, a three-dimensional numerical model with detailed chemical mechanism, transport, and heat transfer and a thermo-photovoltaic energy conversion model are developed to examine its performance. Results show that the proposed micro-combustor has excellent wall temperature uniformity because a uniform distribution of high-temperature zones of four individual flames is formed in the combustion chamber. Thermal performance and energy efficiency of the proposed micro-combustor are better than conventional micro-combustor at a low flow rate (m) and large equivalence ratio (φ). Additionally, the implemented plate-insertion strategy effectively overcome the deterioration of combustor performance under higher m or lower φ. Proposed micro-combustor with plates insertion has the largest wall temperature and energy efficiency, no matter what φ and m are adopted. Plates extend the fluid ravel path and produce some recirculation zones, which promotes heat transfer, preferential diffusion, and flame anchoring, while its pressure loss is larger. Of all the tested cases, the system efficiency reaches a maximum of 6.39%, corresponding to 12.1 W electricity output. This work provides effective combustor design and research insights to develop high-efficiency micro-power system. • A novel micro-combustor with four entrances is proposed for micro-TPV system. • Excellent performance of wall temperature uniformity is obtained. • Inserting plates boosts thermal performance and energy conversion efficiency. • A maximum system efficiency of 6.39% is achieved with 12.1 W electric output. [ABSTRACT FROM AUTHOR]