双级跨声风扇双段轴向缝式机匣扩稳机理分析

Mechanism of stall margin improvement of two stages transonic fan with two-portion axial slot casing treatment

关键词:  跨音速压气机  机匣处理  数值模拟  扩稳机理+

Key words:  Transonic compressor  Casing treatment  Numerical simulation  Mechanism of stall margin improvement+

摘要:

以高负荷,高转速的双级跨声轴流风扇为对象,用数值模拟的方法研究了双段轴向倾斜槽类机匣的扩稳机理。计算得到的实体壁机匣和处理机匣的性能曲线与实验结果符合得较好。计算和实验均表明,双段缝式处理机匣扩大亚声速工况下的稳定工作范围。通过详细的流场分析表明,亚声工况下双级风扇第1级动叶吸力面附面层分离造成的叶顶通道阻塞是双级风扇流动失稳的关键因素。双段缝式处理机匣利用叶顶通道的压差在缝内形成回流,该回流将转子顶部通道内的低能流体抽吸进入缝中并向缝上游输运,在输送过程中在压差的作用下加速,最后在缝上游区重新进入主流。通过这种方式激励了转子顶部通道端壁区的低能气团,从而有效地扩大了亚声速工况下该跨声速风扇的稳定工作范围。

Abstract:

The mechanism of stall margin improvement is investigated on a high rotating speed and high load two-stage transonic compressor with two-portion axial slot casing treatment by 3D numerical simulation. The calculated overall performance curves good agree well with the experiments. The results show that the stable operating range is extended with two-portion axial slot casing treatment in the subsonic condition. The detailed analysis of the calculated flow-filed at the blade tip shows that the separation of the rotor blade suction boundary of the first stage cause blockage in the blade tip passage,which is the primary reason for compressor stall in the subsonic condition. Back flow come into being in the slots by pressure difference,which makes low energy air mass of blade tip enter slot or transport the low energy of slot downstream to slot upstream. The low energy air mass is accelerated by pressure difference during transportation and it turns into mainstream again at the slot upstream. This kind of flow manner can inspirit the low energy air mass of blade tip near end wall and extend the stable operating range of transonic compressor in the subsonic condition effectively.