诱导轮液化天然气空化热力学效应数值计算研究

Numerical study on thermodynamic effect of inducer cavitation in liquefied natural gas

为了探究诱导轮内部低温热敏介质的空化流动特性,采用RNG k-ε湍流模型和添加热力学效应项的Merkle模型,以常温水和液化天然气(LNG)为介质,采用添加了热力学效应项的Merkle模型对诱导轮进行空化两相数值模拟。通过与实验数据比较,验证了修正的Merkle模型的准确性。模拟结果表明,相较于原Merkle模型的等温假设,修正后的Merkle模型模拟得到的空化核心区域的面积和气相体积分数显著减小,体现了热力学效应对低温空化的抑制作用。相较于常温水,诱导轮LNG的空化发展更缓慢,空化区域的叶片载荷随空化数的减小变化不明显,LNG的临界空化数比常温水的临界空化数低16.7%。当诱导轮处于完全空化状态时,LNG气相体积分数的峰值比常温水气相体积分数的峰值低13.48%,LNG的最大温降是常温水最大温降的2.3倍。在相同空化数下,诱导轮LNG空化模拟得到的空化区域和高值气相体积分数更低,热力学效应对液化天然气的空化具有更强的抑制作用,且随着空化数的减少,空化的抑制作用更明显。

In order to explore the cavitation flow characteristics of the low-temperature thermosensitive medium inside the inducer,the RNG k-εturbulence model and the Merkle model with added thermodynamic effect terms are used,and normal temperature water and liquefied natural gas are used as the medium,and the Merkle model with thermodynamic effect terms added are respectively adopted.The gas-liquid two-phase numerical simulation is performed on the inducer.By comparing with experimental data,the accuracy of the modified Merkle model is verified.The simulation results show that compared with the isothermal assumption of the original Merkle model,the area and gas phase volume fraction of the cavitation core region simulated by the modified Merkle model are significantly reduced,which reflects the thermodynamic effect of inhibiting lowtemperature cavitation,the cavitation of inducer LNG develops more slow ly than that of normal temperature water.The blade load in the cavitation zone does not change significantly with the decrease of ca vitation number.The critical cavitation number of LNG is 16.7%lower than that of water at room temperature.When the inducer is in a completely cavitation state,the peak value of the LNG meteorological volume fraction is 13.48%lower than the peak valu e of the normal temperature water vapor phase volume fraction,and the maximum temperature drop of LNG is 2.3 times the maximum temperature drop of normal temperature water.Under the same cavitation number,the cavitation area and high-value mete orological volume fraction obtained by the inducer LNG cavitation simulation are lower,and the thermodynamic effect has a strong er inhibitory effect on the cavitation of liquefied natural gas,and with the decrease of the cavitation number,the inhibitory effect of cavitation is more obvious.