单螺杆膨胀机泄漏通道长度变化规律的理论分析

Theoretical Analysis of Variation of Leakage Path Length in Single Screw Expander

对于回转式的容积型膨胀机,内部泄漏是影响其性能的重要因素。单螺杆膨胀机具有复杂的三维空间结构,使得其内部泄漏规律变得很复杂。为了研究单螺杆膨胀机内泄漏规律,从单螺杆膨胀机的几何结构出发,建立泄漏通道长度的数学模型,并分析进气孔口,螺杆直径和星轮直径等因素对泄漏通道长度的影响规律。结果表明,在进气过程中,当进气孔口完全加入时,泄漏通道L_9达到最大值,在膨胀过程中,泄漏通道的长度大小关系依次为L_8>L_7>L_1+L_2+L_4>L_9>L_6>L_3+L_5;单螺杆膨胀机螺头处泄漏通道的长度与内容积比有关,进气过程螺头处泄漏通道的长度随着内容积比的增大而减小;在内容积比不变的情况下,螺杆直径和星轮直径相等(等径)时,直径越大,泄漏线越长,且螺杆直径和星轮直径不相等(不等径)的泄漏线比等径时的更长,受进气孔口的影响更大。通过上述工作,为单螺杆膨胀机内泄漏量的分析计算提供基础数据,并为单螺杆膨胀机的结构优化提供理论指导。

Leakage loss has great influence on the performance of rotary positive displacement type expander. Single screw expander has very complex internal leakage law for its sophisticated three-dimensional structure. In order to investigate the internal leakage law of the expander, a mathematical model is built based on the geometry structure, the influence of the size of inlet port and the diameters of the screw and the star wheel on the length of the leakage path is analyzed. Results shows that, during the intake process, the length of leakage path L_9 reaches the maximum when intake orifice completely joined, the order of leakage path length relationship in the expansion process is L_8L_7L_1＋L_2＋L_4L_9L_6L_3＋L_5. The length of leakage path at the screw head of the expander is related to the internal volume ratio and decreases with the increase of internal volume ratio during the intake process. Under the condition of fixed internal volume ratio, the length of the leakage path rises with the increased diameter of both when the diameters of screw and star wheel are equal, and the inlet port has a far greater impact on leakage path length which is longer in the case of different diameters, which provide basis data for the analysis and calculation of the leakage rate in the single screw expander and theoretical guidance for structure optimization of the expander.