某型液体火箭发动机部分进气涡轮盘振动分析及改型设计

Vibration analysis and modification design of partial admission turbine disk for a liquid rocket engine

针对某液体火箭发动机部分进气自由叶片涡轮盘多次试车后在叶片型线根部和背弧出现疲劳裂纹的问题,采用三维弹塑性有限元法,考虑部分进气产生的Kick效应,计算了涡轮盘的静强度,得到了部分进气作用下叶片的静弯应力;考虑多场环境引起的预应力影响,计算了涡轮盘的模态,获得了涡轮盘固有频率和主振型;采用全环模型,计算了部分进气作用下涡轮盘的动态响应和动应力。在裂纹原因分析的基础上,对涡轮盘进行改型,在叶片顶部增加了围带,并对带围带涡轮盘进行了计算分析。结果表明:加围带后,涡轮盘叶片气流静应力下降了50%;气流力作用下的叶片动弯应力下降了65%;叶片之间以及叶片和轮盘之间耦合作用明显增强,涡轮盘固有振动模式发生转变,避免了叶片在共振频率附近发生的强迫振动;改型后显著降低了涡轮盘静应力及动弯应力,降低了出现裂纹的风险。

Aiming at the problem of fatigue cracks at the root and back areas of the free standing blade turbine disk of a liquid rocket engine after many test runs,the three-dimensional elastoplastic finite element method was used to calculate the static strength of turbine disk and obtain the static stress of blade,considering the Kick effect generated by partial admission.Considering the influence of prestress caused by multi-field environment,the modes of turbine disk were calculated,and the natural frequencies and main vibration mode of the turbine disk were obtained.The dynamic response and dynamic stress of turbine disk under partial admission were calculated by using the full-loop model.On the basis of analyzing the cause of crack,the turbine disk was modified by adding integral-shroud at the top of the blade,and the turbine disk with integral-shrouded blade was analyzed.The results show that the static stress of the blades decreases by 50% after the modification,and the dynamic bending stress of the blades under the action of airflow force decreases by 65%.The coupling effect between blades and disk is obviously enhanced,and the natural vibration mode of turbine disk changes,which avoids the forced vibration of blades near the resonant frequencies.After the modification,the static stress and dynamic bending stress of turbine disk are significantly reduced,and the risk of crack generation is reduced.