低温液化天然气膨胀机非定常数值模拟

Unsteady numerical simulation of cryogenic LNG expander

为了研究低温膨胀机的压力脉动特性,采用数值模拟方法对膨胀机水力模型进行数值模拟。首先通过定常数值模拟得到膨胀机的外特性,并将模拟结果与试验结果进行对比,验证了模拟结果的精确度,然后以定常数值模拟结果为基础进行非定常数值模拟,得到导叶与转轮内不同监测点的时域图,并通过快速傅里叶变换得到监测点的频域图。结果表明:转轮内监测点主频与导叶叶片数对流体的影响一致,导叶内监测点主频与转轮叶片数对流体的影响一致。监测点主频的幅值与监测点的位置相关,当监测点靠近导叶与转轮之间的无叶区时,幅值更大;与无叶区距离越远,幅值越小,受到导叶与转轮之间动静干涉的影响越小。研究结果可为低温膨胀机的设计提供参考。(图9,表1,参21)

To study the pressure pulsation characteristics of the cryogenic expander,the numerical simulation was performed on the expander hydraulic model by the numerical simulation method.Firstly,external characteristics of expander were obtained by steady numerical simulation.Simulation results were compared with test results,verifying the accuracy of simulation results.The unsteady numerical simulation was performed based on the results of steady numerical simulation.The time-domain plot at different monitoring points of the guide vane and the runner was drawn,and the frequency-domain plot at monitoring points was obtained through fast Fourier transform.The results show that the effect of dominant frequency at the monitoring point of the runner on fluid is as consistent as that of the number of the guide vanes and the effect of dominant frequency at the monitoring point of the guide vanes on fluid is as consistent as that of the number of the runner.The amplitude of the dominant frequency at the monitoring point is related to the point location.When the monitoring point is close to the vaneless area between the guide vane and the runner,the amplitude is larger.The further the distance from the vaneless area is,the smaller the amplitude is,and the smaller the influence of dynamic and static interference between the guide vane and the runner is.The research could provide reference for the design of cryogenic expander.(9 Figures,1 Table,21 References)