20 kHz空气射流激振技术及涡轮叶片高阶振动研究

The research of the high-order vibration characteristics of turbine blade will play an important role in the study of the high cycle fatigue failure of turbine blades caused by high-frequency vibration. However， due to the limitation of existing vibration excitation technology， it is difficult to study the high-order vibration characteristics of turbine blade above 8 kHz. This paper focuses on the study of air jet excitation test technology with the highest excitation frequency up to 20 kHz， and applies it to the study of high-order vibration characteristics of turbine blade. The air jet excitation technology is based on the principle of air jet， and utilizes the nozzle plate to cooperate with the tested blade to form a harmonic airflow excitation for the high-pressure air sprayed out. Theoretical analysis and experimental test are used to verify the air jet excitation technology. The results show that the excitation force also obviously shows the higher multiple harmonic excitations in addition to the theoretical excitation frequency， but the maximum values of linearity S ₂ and S ₃ are only 11.63% and 4.71%， respectively， indicating that the air jet excitation technology has the good fixed frequency excitation ability. Comparing the high-order vibration characteristics of turbine blade using air jet excitation technology with modal test results， the maximum relative error of the first four natural frequencies is only 1.49%. Therefore， the high-order vibration characteristics of turbine blades can be accurately obtained by the air jet excitation test technology proposed in this paper.