Research On The Combustion Characteristic And Wind-Resistant Principle Of Industry Torch Heads

The industry flare is widely used in many industries, such as oil, chemical and plastic, and so on, as the important safety and environmental friendly facility. In practical applications, the torch head in windy areas is so often burnt that the flare system cannot operate normally. In order to improve the life of the torch head, installing a breaking-wind ring around the torch cylinder is a common solution in practical engineering. However, due to the limitation of the test and the difficulty of the actual measuring, research on the combustion characteristic and wind-resistant principle of torch heads still stays in the theoretical stage, and no visual or quantitative research is found. Therefore, in this paper the combustion characteristic of torch heads and the actual effect of the breaking-wind ring are studied by numerical simulation.The FLUENT software is used as the solver, and the DES method based on SST k-ω turbulence model and the Eddy dissipation combustion model are selected as numerical simulation method, and the Semi-Implicit Method for Pressure-Linked Equation (SIMPLE) is adopted. This paper examines numerically models of the torch head and the breaking-wind ring with different parameters. By studying the basic characteristic of each model in the non-reaction and combustion flow field, the burnt reason of the torch head under wind and the working mechanism of the breaking-wind ring are carefully examined. Some useful results are presented for practical design of the breaking-wind ring. The numerical simulation for the torch head of the cylinder diameter D=100mm at the wind speed U=20m/s is performed to examine the flow and combustion state. Then, a detailed visual analysis for the easily burnt reason of the torch head is carried out by using variable contour plot in the simulation results. The following conclusions are got:In the non-reaction flow field, the "Karman vortex" phenomenon appears in the wake-flow region of the torch cylinder, the CH4emitting from the torch head flows into vortex structures in the wake-flow region of the torch cylinder, and flows downstream together with vortex structures; In the combustion flow field, the flame distributes on the leeward side of the torch cylinder, falls off the torch cylinder wall and spreads downstream in the form of vortex structures; In short, the main reason that the torch head is easily burnt is the vortex structures formed in the wake-flow region of the torch cylinder.Next, the breaking-wind ring models with different installation gaps A and shielding rates k, respectively, A=0.2D with k=50%, A=0.5D with k=50%and A=0.5D and k=30%, are discussed by the numerical simulation. A qualitative analysis for design parameters of the breaking-wind ring is conducted by using the pressure and temperature contours from simulation results. The following conclusions are got:In the view of suppressing the high-temperature region of the torch head leeward side, when the shielding rate k is unchanged, the model with the installation gap of0.5D is superior to the model of0.2D; When the installing gap is fixed, the model with the shielding rate of50%is better than the model of30%; So, the installing gap A of the breaking-wind ring is recommended about0.5D, and the shielding rate k about50%.Finally, a comprehensive comparison between the torch head models with the breaking-wind ring at A=0.5D and k=50%and without the breaking-wind is carried out. Some useful results are obtained:With the breaking-wind ring, the intensity of vortex near the torch cylinder decreases sharply, the formation of large vortex structures in the wake-flow region of the torch cylinder delays backward, the flame elongates and obliquely spreads upward, the high-temperature area on the torch cylinder leeward side reduces drastically. All in all, the breaking-wind ring plays an important pole in improving the life of the torch head.