双级跨音风扇轴向缝处理机匣结构优化的数值研究

Further Numerical Investigation of Optimum Structure of Axial Slot Casing Treatment on a Two-Stage Transonic Fan

文章以1台高负荷、高转速的双级跨音轴流风扇为对象,基于对原型风扇失稳机理及原始处理机匣扩稳机理的认识,设计了3种新的处理机匣,在其上进行轴向缝处理机匣结构优化的数值研究。数值计算结果表明,跨音工况下新设计的3种处理机匣对风扇的裕度均没有改进,这与原始处理机匣的实验和计算结果是一致的,而新设计的机匣结构2和结构3在亚音工况下均比原始处理机匣获得更大的裕度改进量。通过对亚音工况下风扇内部流场进行了详细分析,探索了新设计的第2、第3种处理机匣结构获得更大扩稳能力的流动机理。流场分析表明,机匣结构2处理面积的增加提高了轴向缝抽吸或吹除叶顶低能气团的能力,使叶顶通道的流通能力提高。较之于结构2,前置的处理机匣结构3更好地利用了叶顶通道的压差,因而其扩稳能力进一步提高并获得了一定程度的性能改进。

Aim.This paper is another small step forward in NWPU（Northwestern Polytechnical University） long-standing research on improving axial slot casing treatment.The numerical investigation of the optimum structure of axial slot casing treatment is performed on a high rotating speed and high load two-stage transonic fan.Section 1 of the full paper explains our new ideas on optimizing the axial slot casing treatment;in particular,in addition to the original optimum structure,we propose three new structures,which we call structures No.1,No.2 and No.3.Section 2 briefs the numerical calculation method which we have been using.Section 3 presents numerically calculated results,given in Figs.2 through 6 and Table 1,and their analysis,which show preliminarily that：（1） the three new casings have no capacity for extending the operating range of the fan under transonic condition,and this is consistent with the experimental and calculated results of the original casing;（2） the stall margin improvement is higher with the structures No.2 and No.3 of the new casing treatment than with the original casing treatment under subsonic condition;the mechanism of extending the stall margin under subsonic condition is explored with detailed analysis of flow-field in the fan as given in Figs.4 through 6;the extension of the treated area of casing structure No.2 increases the ability of bleeding or blowing blade tip low energy flow mass,thus improving the flow capacity near tip passage;（3） because the structure No.3 uses the pressure difference better than structure No.2,its stall margin improvement is further increased with the accompanying improvement of the fan performance;the compressor efficiency is higher with No.3 casing treatment than with No.2 casing treatment as shown by the results in Fig.3.