高压容器泄漏中发生的焦耳-汤姆逊效应研究

压缩天然气的海上运输技术由于其经济效益而即将走向商业化。在运输船上的压强高达25 MPa的压力容器是其设计的重点。破前漏准则是维护压力容器完整性的一个重要方法。然而,在压力容器泄漏中发生的焦耳-汤姆逊效应所导致的裂纹周围金属温度的降温可能会影响到破前漏准则的有效性。对在压力容器的泄漏中发生的焦耳-汤姆逊效应做了相关的试验研究。因氩气不易燃烧且具有与甲烷相似的焦耳-汤姆逊系数而被选作试验气体。设计一个全新的用于压力容器泄漏试验的焦耳-汤姆逊测试系统。根据美国机械工程师学会(American Society of Mechanical Engineers,ASME)锅炉和压力容器规范设计和加工一个试验用的压力容器。采用液氮断裂方法在一块测试板上制作一个与自然裂纹相似的贯穿裂纹。在30℃的环境温度和9.1 MPa的最大内部压强下,测试板外表面沿裂纹方向测得的最低温度是12.5℃,沿裂纹对角线方向测得的最低温度是7.9℃,裂纹出口处得到的氩气的温度是-9.2℃;测试板内表面沿裂纹方向测得的最低温度是15℃,容器内部裂纹附近测得的氩气的温度是-7.1℃。试验结果表明,在整个测试过程中,测试板内外表面的温度沿裂纹不同方向的变化趋势基本上一致。

Study on the Joule-Thomson Effect during Leakage in High Pressure Vessels

Due to its economic profits, the marine transportation of compressed natural gas is about to enter the commercial stage. The highly pressurized containers (up to 25 MPa) on vessels are in the focus of the design. The key to maintaining the integrity of the pressured pipes is the philosophy of leak-before-break(LBB). However, the temperature drop in the vicinity of a crack caused by Joule-Thomson cooling effect during leakage in a pressure vessel may impact on the validation of the LBB principle. Experiments are carried out to study the Joule-Thomson effect occurred during leaks through cracks on a pressure vessel. Argon is selected as the gas used in the experiment due to its incombustibility and similar Joule-Thomson coefficient to that of methane. A new Joule-Thomson testing facility with a pressure vessel is designed to perform the leak test. The pressure vessel is designed and fabricated according to ASME Boiling and Pressure Vessel Code. Liquid nitrogen cracking method is employed to fabricate a realistic through-thickness crack in a test plate. Under the condition of an ambient temperature of 30℃ and maximum internal pressure of 9.1 MPa, the lowest temperature measured along the crack line on the outside surface of the test plate is 12.5℃. It is 15℃ along the crack line on its inside surface and?9.2℃ of the escaping argon. And it is 7.9℃ along the crack diagonal line on its outside surface and?7.1℃ of the argon inside the pressure vessel. It shows that the changing trends of temperature in test plate along different crack directions are basically identical in the whole test process.