气液两相流临界分配特性及相分离控制
Gas？？Liquid Two？？Phase Flow Critical Distribution Characteristic and Phase Splitting Control

为实现对气液两相流的均匀分配,提出了一种由旋流叶片、整流器以及两个分流喷嘴组成的新型分配装置。其工作原理是:通过旋流叶片将来流调整为均匀环状流型,以保证两分流喷嘴入口接触气液两相流的几率相等;通过喷嘴加速两相流达到当地声速,形成临界流动,以克服喷嘴下游各支管路阻力特性不一致所导致的相分离。在气液两相流实验环道上开展了实验测试,实验分配器分流喷嘴喉部直径为8 mm,扩张角为21°。实验气相折算速度范围为7～20 m/s,液相折算速度范围为0.013～0.16 m/s,出现的流型包括波浪流、段塞流以及半环状流。结果表明:在喷嘴喉部气液混合物速度达到声速的条件下,气液相分流系数接近理论值0.5,不受上游流型以及气液流速的影响。侧支管干度与主管干度最大偏差小于±5％,而当液相折算速度小于0.02 m/s时,无法形成均匀环状流,气相更容易进入侧支管。提高液相折算速度以及喷嘴差压在分配总压降中所占比重,将有助于降低相分离程度。所提出的分配器结构紧凑,无分离装置和控制元件,基本无需维护,有望在高压两相流分配系统中获得广泛应用。
A novel distributor was proposed to uniformly distribute the gas？？liquid two？？phase flow. The distributor consists of a swirl vane, a flow adjuster and two nozzles. The swirl vane is used to change the upstream flow into annular flow with uniform film thickness for both nozzles having same inlet condition. The function of the nozzles is to accelerate the gas？？liquid mixture to reach local sonic velocity and eliminate the phase separation due to the difference of resistance characteristics of the two branches. The throat diameter of the experimental nozzle is 8 mm and the expansion angle is 21°. Experiments were carried out in an air？？water two？？phase flow loop. The superficial liquid velocity was in the range of 0.013？？0.16 m/s and the superficial gas velocity varied from 7 m/s to 20 m/s. The flow patterns observed included wavy flow, slug flow and semi？？annular flow. It was found that equal distribution was obtained under critical flow condition. The splitting ratio of gas and liquid was close to the theoretical value (0？？5) and independent of flow patterns, superficial gas or liquid velocity. The maximum quality deviation between outlet branch and the inlet pipe was less than ±5%. When the superficial liquid velocity was below 0.02 m/s, no uniform annular flow was achieved and the gas preferred to enter the top branch. Increasing the superficial liquid velocity and the ratio of nozzle pressure loss to the total pressure loss could help to reduce phase separation. The proposed device has the advantages of small size and low cost, and can be used in high pressure gas？？liquid two？？phase system