4种激励方式下声模态衰减率的识别  

Decay rate identification of acoustic modes under four different forms of excitation

作　　者：杨尚荣 尚帅 于涵 YANG Shangrong;SHANG Shuai;YU Han(National Key Laboratory of Aerospace Liquid Propulsion,Xi'an Aerospace Propulsion Institute,Xi'an 710100,China)

机构地区：[1]西安航天动力研究所航天液体动力全国重点实验室,陕西西安710100

出　　处：《火箭推进》2025年第1期102-110,共9页Journal of Rocket Propulsion

基　　金：全国重点实验室基金(HTKJ2021KL011001)。

摘　　要：声模态的衰减率常被用来评估液体火箭发动机的燃烧稳定性裕度,从脉动压力数据中识别衰减率的准确性决定着评估结果的可靠性。针对衰减率的准确识别问题,开展了4种激励方式下(白噪声激励、单频激励、扫频激励、脉冲激励)模型燃烧室的声模态衰减率识别研究。分析了4种识别方法间的关系以及适用的激励方式,比较了不同激励方式下声模态频率和衰减率的识别结果。数值验证发现:白噪声激励时自相关法的精度较高,偏差为1.8%;扫频激励下半功率方法和频率响应函数方法的精度相当,偏差为1.5%和1.8%;单频激励和脉冲激励采用对数减幅率方法,偏差分别为1.3%和0.8%。实验研究发现:不同激励方式下声模态频率的最大标准差为8.5%;噪声、扫频和单频激励下三者衰减率的绝对值差别较大,最大标准差为37%,但各阶声模态衰减率的排序一致。脉冲激励下衰减率整体偏大,应为激励幅值较大时模型燃烧室的非线性衰减特性所致。The decay rates of acoustic modes are often used to evaluate the combustion stability margin of liquid rocket engines.The accuracy of the decay rate identified from the pressure data determines the reliability of the evaluation results.In order to determine the method of accurately identifying the decay rate,a study on decay rate identification of acoustic modes under four different forms of excitation(white noise excitation,harmonic excitation,swept frequency excitation,and pulse excitation)has been carried out.The relationship between the four identification methods and the applicable excitation forms is analyzed.The identification results of acoustic mode frequencies and decay rates under different forms of excitation are compared.Numerical validations reveal that the autocorrelation method has a higher accuracy with a deviation of 1.8%under white noise excitation.The accuracy of the half-power method and the frequency response function method are comparable under frequency-swept excitation,with deviations of 1.5%and 1.8%.The logarithmic decrement method is used for single-frequency excitation and pulse excitation,with deviations of 1.3%and 0.8%,respectively.Experimental results show that the maximum standard deviation of the acoustic mode frequencies under different excitations is less than 8.5%.The absolute values of decay rates under white noise,sweep and single-frequency excitation are quite different,with a maximum standard deviation of 37%,but the order of decay rates is consistent for all acoustic modes.Larger decay rates are obtained under pulsed excitation,which should be caused by the nonlinear decay rate of the model combustion chamber when the excitation amplitude is large.

关 键 词：燃烧稳定性裕度 激励方式 衰减率 模态识别 

分 类 号：V231.1[航空宇航科学与技术—航空宇航推进理论与工程]