基于冷库环境下的涡扇发动机叶片冰脱落试验

发动机结冰脱落现象因其随机性和复杂性很难通过计算仿真获得可靠的结果，而冰风洞试验又因其高昂的使用成本限制了该方法的普及。为此建立了一个兼顾可行性及经济性，同时具有一定可靠性的试验方法，即借助冷库环境并利用斜流风机、喷雾耙、温度调节系统等模拟飞行过程中可能面临的结冰环境；以某型号民用飞机涡扇发动机缩比带动力模型为对象，研究不同工况下叶片结冰及冰脱落的特性和规律。在正式试验之前，通过热线风速仪、喷雾激光粒度仪、标准冰刀和金属格栅分别对来流速度、流场中液态水含量、水滴的平均粒径进行了标定。为克服云雾循环/聚集的问题，开发了云雾吸附系统，便于在封闭的冷库环境中维持流场的稳定性。试验结果表明：当转速为2 400 r/min不变时，随着环境温度的降低，冰脱落所需的时间及剩余冰的特征长度均先减小后增大，其拐点出现在-3.5~-5℃的区间内；当环境温度为-7℃不变时，叶片绕转轴的转速越大，冰脱落所需的时间及剩余冰的特征长度均单调减小。

Test of ice shedding on turbofan engine blade in refrigeratory environment

Due to the complexity and randomness of the turbofan blade icing shedding characteristics, it is difficult to use computational simulation to obtain reliable results. On the other hand, icing wind tunnel test can hardly be always applied due to its high cost. In this paper, a feasible, economical and reliable test method is proposed by using mixed-flow fan, water spray and temperature control system in the environment of refrigerator to simulate freezing weather condition during real flight. A scaled powered model of a certain civil aircraft turbo-fan-engine is used as research object to study the blade icing and ice shedding characteristics and rules in different working conditions. Before formal test, parameters such as flow velocity, liquid water content, and mean volumetric diameter are calibrated by anemometer, particle sizer, standard ice blade and metallic grille. A fog absorber is created to solve the problem of fog recycling and accumulation, which makes it possible to keep the stability of flow field in an enclosed refrigeratory environment. The test results show that when the rotational speed is fixed at 2 400 r/min, consuming time for shedding and residual ice characteristic length decrease initially and increase afterwards with the decrease of environment temperature. The inflection point appears when the temperature is in the range of -3.5℃- -5℃; when the temperature is fixed at -7℃, the consuming time for ice shedding and the characteristic length of residual ice decrease monotonously with the increase of the rotational speed of blade.