小型 LNG 装置混合制冷剂螺杆压缩机工作过程模拟

摘要

The two stage screw compressor is suitable for the mixed refrigerant cycle (MRC)in the small scale LNG unit,and the interstage pressure is a important parameter to influence the working condition of the compressor.In this paper,the arc and arc envelope line is chose to constitute the rotor profile and the variation of chamber volume is calculated.A mathematic model is set up,and the gas pressure,interstage pressure,isentropic efficient is simulated in the working process of a two stage screw compres-sor.The results shows that the interstage pressure is automatic built according to the dynamic mass flow rate of each stage.The mass flow rate of each stage is equal when the interstage pressure is stable.The interstage pressure decreases with the increase of rotating speed,and the isentropic efficiency increase with the increase of rotating speed,especially for the second stage.%螺杆压缩机具有结构紧凑、维护方便和工况适应性强等优点，在采用混合制冷剂液化流程工艺（MRC）的小型LNG 装置中具有良好的应用前景。在 MRC 流程中需要两级压缩，级间压力是影响两级螺杆压缩机运行状态的主要参数之一。本文根据混合制冷剂工艺流程参数特点，采用圆弧及圆弧包络线构建了螺杆转子型线，分析了两级压缩机工作腔容积的变化规律，建立了两级螺杆压缩机工作过程的数学模型，研究了压缩机工作过程中工作腔内气体压力、级间压力、等熵效率等参数的变化规律。结果表明：两级螺杆压缩机的级间压力依据各级瞬态质量流量自动形成，压缩机稳定运行时的级间压力能使各级质量流量相等；级间压力随转速的增大而逐渐降低，各级等熵效率均随转速的增大而增大。