Experimental Study on Critical Flow of Supercritical Carbon Dioxide at Transient State
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摘要: 当超临界系统发生破口事故时，系统内高温高压流体在破口处会发生临界流动现象，瞬态临界流动特性对事故进程有较大影响。与临界流稳态相比，瞬态喷放过程中的泄压速度对临界质量流速有着重要的影响，为此开展了以超临界二氧化碳（SCO2）为工质的临界流瞬态试验，试验段采用直径2 mm、长径比L/D为3、进口为圆角的喷管，试验初始压力为7.70~7.98 MPa，初始温度为35.5~40.6℃，进行了4种泄压速度的瞬态试验。试验结果表明，在喷放开始阶段，泄压速度越大，临界质量流速越小；然而在喷放后期，泄压速度越大，临界质量流速越大。Abstract: When a break accident occurs in a supercritical system, the high-temperature and high-pressure fluid in the system will have a critical flow at the break, and the transient critical flow characteristics have a great influence on the process of the accident. Compared with the steady state of critical flow, the pressure relief speed in the process of transient blowout has an important influence on the critical mass flow rate. Therefore, a transient test of critical flow with supercritical carbon dioxide (SCO2) as working medium was carried out. A nozzle with a diameter of 2 mm, a length diameter ratio (L/D) of 3 and a rounded inlet was used as the test section. The initial pressure was 7.70~7.98 MPa and the initial temperature was 35.5-40.6℃. Transient tests with four depressurization velocities were carried out. The experimental results show that the greater the velocity of depressurization, the smaller the critical mass flow rate at the initial stage of blowout. However, at the later stage of blowout, the greater the velocity of depressurization, the greater the critical mass flow rate.
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图 1 临界流瞬态试验系统
VAJ—电动调节阀；VCO—电动截止阀；VHO—手动截止阀；VSO——电磁阀；T—温度测点；PIT—压力测点；DPIT—差压测点；FIT—流量测点
Figure 1. Diagram of the Transient Test System
图 3 旁路阀开度0%时喷放过程中压力和质量流速的变化
Figure 3. Variation of Pressure and Mass Velocity with Time during Blowout with Bypass Valve Opening of 0%
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