Cold and hot model investigation of flow and mixing in a multi-jet flare.

摘要

The objective of this study is to advance the understanding of mixing and combustion in an offshore flare burner and to propose a new design for the flare burner.; The geometry definition work started with the characterization of mixing in cold model of the flare burner using a single laser beam and laser sheet Mie scattering visualization. These experiments were carried out in a 0.45 x 0.45 x 1.8 m test section of a wind tunnel with the jet marked with oil smoke. The cross-flow velocity was 2.8 m/s and the jet exit velocity was 68 m/s. The corresponding Reynolds numbers are respectively 84,000 and 17,240. Long series of CCD images allowed quantitative and qualitative analysis of the flow, which were used for selecting a single geometry and position of each mixing altering device.; Subsequently, the hot-model experiments were performed outdoors under calm atmospheric conditions with a cross flow stream supplied by an open wind tunnel operating at a nominal velocity of 4 m/s (turbulence intensity of 12.3–14.2%). Total radiation flux, temperature, gas composition and flame images were data acquired from the flames. The full burner test matrix was performed at a single cross flow velocity for all four burner arrangements and five gas flow rates. The jet Reynolds number ranged from 3,800 to 16,800 and the heat released did not exceed 0.5 MW.; Numerical models were tuned reproducing the investigated flames and prepared for the scaling-up to real flare size flames. The open flames in cross-flow air were simulated as integral lines of top-hat profiles of properties. The simulation method included 27 differential equations, which were numerically solved using a Milne predictor and a Hamming corrector method with a fourth order Runge-Kutta starter. The measured length and trajectory of the flames were reproduced as close as possible.; Finally, using the tuned numerical simulators the length and trajectory of real size flare flames were designed and their radiative fluxes calculated. A precessing nozzle flare was designed as capable of burning 10,000,000 Nm3/day (20°C and 1 atm) of gas in a boom with length L_B = 106 m and elevation angle α_B = 60° without exceeding the maximum allowable radiation flux over the working areas. Several other combinations of boom length, elevation angle and burner arrangements satisfied the posed technical requirements. (Abstract shortened by UMI.)