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首页> 外文期刊>International Journal of Pressure Vessels and Piping >Transferability of decompression wave speed measured by a small-diameter shock tube to full size pipelines and implications for determining required fracture propagation resistance
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Transferability of decompression wave speed measured by a small-diameter shock tube to full size pipelines and implications for determining required fracture propagation resistance

机译：小直径减震管测得的减压波速度到全尺寸管道的可传递性及其对确定所需裂缝传播阻力的影响

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The control of propagating ductile (or tearing) fracture is a fundamental requirement in the fracture control design of pipelines. The Battelle two-curve method developed in the early 1970s still forms the basis of the analytical framework used throughout the industry. GASDECOM is typically used for calculating decompression speed, and idealizes the decompression process as isentropic and one-dimensional, taking no account of frictional effects. While this approximation appears not to have been a major issue for large-diameter pipes and for moderate pressures (up to 12 MPa), there have been several recent full-scale burst tests at higher pressures and smaller diameters for which the measured decompression velocity has deviated progressively from the predicted values, in general towards lower velocities. The present research was focused on determining whether pipe diameter was a major factor that could limit the applicability of frictionless models such as GASDECOM. Since potential diameter effects are primarily related to wall friction, which in turn is related to the ratio of surface roughness-to-diameter, an experimental approach was developed based on keeping the diameter constant, at a sufficiently small value to allow for an economical experimental arrangement, and varying the internal roughness. A series of tests covering a range of nominal initial pressures from 10 to 21 MPa, and involving a very lean gas and three progressively richer compositions, were conducted using two specialized high-pressure shock tubes (42 m long, I.D. = 38.1 mm). The first is honed to an extremely smooth surface finish, in order to minimize frictional effects and better simulate the behaviour of larger-diameter pipelines, while the second has a higher internal surface roughness. The results show that decompression wave speeds in the rough tube are consistently slower than those in the smooth tube under the same conditions of mixture composition and initial pressure & temperature. Preliminary analysis based on perturbation theory and the fundamental momentum equation indicates that the primary reason for the slower decompression wave speed in the rough tube is the higher spatial gradient of pressure pertaining to the decompression wave dynamics, particularly at lower pressure ratios and higher gas velocities. The magnitude of the effect of the slower decompression speed on arrest toughness was then evaluated by a comparison involving several hypothetical pipeline designs, and was found to be potentially significant for pipe sizes DN 450 and smaller.
机译：传播的韧性（或撕裂）断裂的控制是管道断裂控制设计的基本要求。 1970年代初开发的Battelle两曲线法仍然是整个行业使用的分析框架的基础。 GASDECOM通常用于计算减压速度，并且在不考虑摩擦影响的情况下，将减压过程理想化为等熵和一维。尽管对于大直径管道和中等压力（最高12 MPa）来说，这种近似似乎不是主要问题，但最近在高压和较小直径下已进行了几项全尺寸爆破测试，测得的减压速度为从预测值逐渐偏离，通常朝着较低的速度。目前的研究集中在确定管道直径是否是可能限制无摩擦模型（如GASDECOM）的适用性的主要因素。由于潜在的直径影响主要与壁摩擦有关，而壁摩擦又与表面粗糙度与直径的比率有关，因此基于保持直径恒定（足够小以允许进行经济的实验）开发了一种实验方法排列，并改变内部粗糙度。使用两个专用的高压冲击管（长42 m，内径= 38.1 mm）进行了一系列测试，测试范围从10到21 MPa的标称初始压力范围，涉及非常稀薄的气体和三种逐渐富集的成分。为了使摩擦效应最小化并更好地模拟大直径管道的性能，第一个经过珩磨以达到极其光滑的表面光洁度，而第二个则具有较高的内表面粗糙度。结果表明，在相同的混合物组成和初始压力和温度条件下，粗管中的减压波速度始终比平滑管中的减压波速度慢。基于微扰理论和基本动量方程的初步分析表明，在粗管中减压波速度较慢的主要原因是与减压波动力学有关的压力的较高空间梯度，特别是在较低的压力比和较高的气体速度下。然后，通过涉及几种假设管道设计的比较，评估了较慢的减压速度对阻滞韧性的影响程度，发现对DN 450及以下的管道尺寸可能具有显着意义。

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