测试井口固定油嘴内的流体流动特性

Fluid Flow Characteristics of Fixed Throttle Choke in Gas Well Testing

采用RNGk-ε湍流模型及Sutherland Viscosity Law可压缩流体黏度修正模型,对测试井口的一种固定节流油嘴内的流体流动过程进行了数值模拟研究。通过数值模拟得到的节流油嘴内质量流率变化规律与理论计算结果对比,验证了所采用的模型和计算方法的准确性。分析了不同节流压力对油嘴内流体流动特性的影响规律。计算结果表明,由于油嘴节流降压,气体体积膨胀出现超音速流动,所形成的高速射流促使油嘴外壁附近出现漩涡流动;油嘴内部压力变化趋势为先下降后升高,然后又缓慢降低的过程;由于节流降温效应,气体流过油嘴时温度下降,油嘴内出入口压力比小于临界压力比时,最易形成天然气水合物,出现堵塞管路的风险。

Based on the RNG k-ε turbulent model and the Sutherland Viscosity Law compressible fluid viscosity advanced model,the flow in a kind of fixed throttle choke used in the gas well testing process was studied in this paper by numerical simulation.The calculated mass flow variation law in the throttle choke is comparable with the theoretical calculations,which verified the adopted models and calculating methods.And then the fluid flow characteristics of the throttle choke was studied to check its specific law with different throttle pressure.The results show that,due to the compressibility of the gas,there was a supersonic flows appeared in the choke and a highspeed jet region came up near its outlet.Vortex flows produced near the outer walls of the throttle choke.The inner pressure in the choke was drop at first and then went high,and finally became lower slowly.Another conclusion is the temperature of the gas would decrease when it flow through the choke due to the throttling cooling effect.When the pressure ratio of the gas less than the critical pressure ratio,the gas hydrates would be formed in the choke and the danger of blocked pipe would be appeared.