It is a difficult scientific problem of applied fluid mechanics that the flame is too long and does not match the furnace chamber in a small restricted heating space. This paper aims to investigate the effect of the air quantity distribution ratio on the flame height of a flue gas self-circulation burner. In order to obtain a better combustion emission effect and a shorter flame height, a burner head structure with a small flue gas selfcirculation was designed. Numerical simulation was employed to investigate the effect of the different distributions of central air, swirling air and secondary air on flame height. The periodic boundary condition model was adopted and the numerical model was compared and validated by experiment. Correlation analysis was used to determine the influence of the air inlet ratio of each part on the flame height and recirculating flue gas ratio (RFGR). The results show that the influence of different air quantity distributions on flame length is very significant. A reasonable central air ratio is a necessary condition for the good combustion of this flue gas self-circulation burner. Secondary air can effectively increase the RFGR, and flame height was significantly shorter with the increase of RFGR, but when it increased to more than 12%, the flame length was basically no longer shortened. On the premise of stable combustion, when the ratio of central air, swirling air and secondary air are respectively 25%, 35% and 40%, the shortest flame length is achieved. This work reveals an influence mechanism of the flame height of a small burner with a flue gas circulation structure. These results can provide theoretical support and an engineering design basis for the short flame problem in a small restricted space.
It is widely accepted that vortex-induced vibration (VIV) is a major concern in the design of deep sea top-tensioned risers, especially when the riser is subjected to axial parametric excitations. An improved time domain prediction model was proposed in this paper. The prediction model was based on classical van der Pol wake oscillator models, and the impacts of the riser in-line vibration and vessel heave motion were considered. The finite element, Newmark-β and Newton‒Raphson methods were adopted to solve the coupled nonlinear partial differential equations. The entire numerical solution process was realised by a self-developed program based on MATLAB. Comparisons between the numerical calculation and the published experimental test were conducted in this paper. The in-line and cross-flow VIV responses of a real size top-tensioned riser in linear sheared flow were analysed. The effects of the vessel heave amplitude and frequency on the riser VIV were also studied. The results show that the vibration displacements of the riser are larger than the case without vessel heave motion. The vibration modes and frequencies of the riser are also changed due to the vessel heave motion
The burning state of a plateau environment is attracting more and more attention. In this paper, in order to have a deeper scientific understanding of diesel spray combustion and the characteristics of a flame under different spray cone angles in a plateau environment, experiments were carried out in a low pressure chamber. The flame morphology was recorded by a high speed video instrument, and the temperature change was recorded by a thermal imager and thermocouples. The MATLAB programming was used to process the video image of the flame, and the probability of its binarization was calculated. The results indicate that the flame becomes longer and wider under different pressures with the same spray angle. The variation is more pronounced at a smaller spray taper angle. The flame uplifted height characteristic is mainly negatively related to the atmospheric pressure. According to the normalized flame temperature and the dimensionless horizontal projection, the length can be divided into three regions. In the region of buoyancy flame, the dimensionless temperature varies with sub-atmospheric pressure more than with normal pressure. In addition, under different spray cone angle conditions, the law of variation in the normalized flame temperature under sub-atmospheric pressure is exactly opposite to that under normal pressure. This study is of great significance to the scientific research on flames in a low pressure environment, and the design of different fuel nozzles for application in a plateau environment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.