测试燃烧器放喷流动及燃烧特性数值模拟

针对气井测试大流量放喷时燃烧产生的高热辐射和噪声对人员及设备造成的危害问题,采用RSM湍流模型、简化的甲烷-氧气2步反应组分输运模型、离散坐标法辐射传热模型、宽频噪声及F-W-H噪声模型对页岩气测试燃烧器大流量放喷燃烧过程进行了数值模拟,考察了大流量放喷时放喷流场及噪声传播规律。分析结果表明:测试燃烧器放喷为扩散燃烧方式,燃烧效率较低,燃烧不完全易冒黑烟,同时扩散燃烧形成上浮火焰形态,火焰根部距离套筒出口较近,形成的高温热辐射使燃烧器本体受热变形而失效;燃烧器内放喷头径向喷孔流速过高导致高射流噪声,进而产生高燃烧噪声,严重威胁人员和设备安全;采用提高燃气和空气混合效果的预混燃烧方式,并合理设计喷孔流速可以抑制现有燃烧器缺陷。所得结果可为大流量测试放喷燃烧器结构改进提供理论指导。

Numerical Simulation of Flow and Combustion Characteristic of the Testing Burner

To address the hazards caused by high thermal radiation and noise generated by high-volume gas combustion to personnel and equipment during gas well testing,a RSM turbulence model,a simplified methane and oxygen 2-step component transport model,and a discrete coordinate method for radiant heat transfer model,wideband noise and F-W-H noise model are used to numerically simulate the large-flow discharge combustion process of the shale gas testing burner. The discharge flow field and noise propagation law during large-flow discharge are investigated. The analysis results show that the testing burner is diffused combustion,which has low combustion efficiency and incomplete combustion that is easy to emit black smoke. The diffused combustion forms a floating flame shape. The flame root is closer to the outlet of the sleeve. The burner body is prone to failure due to thermal deformation caused by high temperature thermal radiation. The excessively high radial velocity of the radial nozzle of the nozzles in the burner results in high jet noise,which in turn generates high combustion noise that seriously threatens the safety of personnel and equipment. A premixed combustion method that improves the gas and air mixing effect and reasonable design of the nozzle flow rate can suppress the current burner defects. The study results can provide theoretical guidance for the improvement of the structure of the large-flow testing burner.