Abstract: To study the unsteady characteristic of two-stage counter-rotating fan，the steady and unsteady simulations have been conducted on a two-stage counter-rotating fan at design rotating speed. The results show that the compressor stall margin of unsteady simulation(15.3%) is larger than that of steady(14.5%)，which mainly results from the improvement of the separation of suction surface near blade tip at near stall condition. At non-stall condition，the nonlinear interactions among upstream wake，upstream leakage flow，downstream leakage flow and shock wave lead to the augment of entropy，which result in loss increment near blade tip. In addition，at all operating conditions，the upstream wakes restrain the hub corner separation and reduce loss.

Key words: Counter-rotating fan；Blade rows interactions；Harmonic balance method；Separation；Stall

摘要： 为研究两级对转风扇的非定常特性，对该风扇进行了设计转速下的定常和非定常数值模拟。结果表明:非定常得到的压气机裕度(15.3%)比定常(14.5%)的更高，主要原因在于近失速时，上游尾迹和泄漏流能改善叶尖吸力面分离；非失速工况时，上游尾迹和泄漏流与下游泄漏流、激波之间复杂的非线性作用会引起熵增，从而导致叶尖流动损失的增加；此外，所有工况下，上游尾迹对叶片根部角区分离都起到了抑制作用，降低了损失。

关键词: 对转风扇；排间干涉；谐波平衡法；分离；失速