基于特征线法的CO_(2)减压波传播模型构建及止裂壁厚研究

Construction of CO_(2) decompression wave propagation model based on method of characteristics and research on crack arrest wall thickness

基于特征线法并结合描述CO_(2)状态的S-W方程,构建了减压波传播模型。将减压波波速模拟结果与工业规模实验结果对比,验证了模型的可靠性。采用构建的减压波模型与日本高强度管道研究委员会(HLP)提出的HLP模型,分别对不同初始压力或温度下一维超临界CO_(2)管道泄漏过程中减压波波速及X65和X70管钢裂纹扩展速度进行模拟计算与比较,以探究初始压力或温度变化对初期减压波速及管道止裂最小壁厚的影响。结果表明:减压波速近似等于初始条件下的声速,故初始压力升高和温度降低(声速上升)会提高减压波的传播速度;当初始压力由7.5 MPa升至9.5 MPa,初期减压波速(0.01 s)上升了53%,X65和X70管钢止裂最小壁厚分别减少了13%和14%;当初始温度由45℃降至35℃时减压波速上升了56%,X65和X70管钢止裂最小壁厚分别减少了20%和19%;当工作压力都低于8.0 MPa (工作温度为35℃)或工作温度分别高于41℃和39℃(工作压力为9.0MPa)时,由GB 150—2011所计算X65和X70管钢壁厚不具备止裂能力。

Based on the method of characteristics and combined with the S-W equation describing the CO_(2) state,a propagation model of decompression wave was constructed.The simulation results of decompression wave velocity were compared with the industrial-scale experimental results to verify the reliability of the model.Using the constructed decompression wave model and the HLP model proposed by the Japan High Strength Pipeline Research Committee(HLP),the decompression wave velocity and crack propagation velocity of X65 and X70 pipe steel during one-dimensional supercritical CO_(2) pipeline leakage under different initial pressures or temperatures were simulated and compared to explore the impact of initial pressure or temperature changes on the initial decompression wave velocity and the minimum wall thickness for crack arrest.The results show that the velocity of the decompression wave is approximately equal to the sound velocity under the initial conditions,so an increase in initial pressure and a decrease in temperature(increase in sound velocity) will increase the propagation speed of the decompression wave.When the initial pressure increased from 7.5 MPa to 9.5 MPa,the initial decompression wave velocity(0.01 s) increased by 53%,and the minimum wall thickness of X65 and X70 pipe steel for minimum wall thickness for crack arrest decreased by 13% and 14%,respectively.When the initial temperature decreased from 45℃ to 35℃,the velocity of the decompression wave increased by 56%,and the minimum wall thickness of X65and X70 tube steels for minimum wall thickness for crack arrest decreased by 20% and 19%,respectively.When the working pressure is both lower than 8.0 MPa(working temperature is 35℃),or the working temperature is higher than 41℃ and 39℃(working pressure is 9.0 MPa),the X65 and X70 pipe steel wall thickness calculated by GB 150—2011 does not have the ability to stop cracking.