基于连续小波变换的柴油机涡轮增压器振源识别

Identification of Vibration Source for Diesel Engine Turbocharger Based on Continuous Wavelet Transform

柴油机涡轮增压器高频振动严重影响到柴油机及整个动力系统的运转可靠性。针对涡轮增压器的主要振源进行识别分析研究,可有效地指导振动控制和本体振动响应优化。针对涡轮增压器本体振动响应具有的高频、宽频带、时变非稳态等特征,利用连续小波变换方法在信号处理中具有的多尺度计算分析频率、精准定位发生时间等时频特性优势,开展瞬态激励下动态振源信号识别分析研究。结合涡轮增压器结构特征及工作原理,对瞬态工况下涡轮增压器振动响应的主要振动源进行识别分析研究,获得气动载荷、转子质量不平衡等激励下的时频特性。通过解析稳态工况(50 513 r/min)下涡轮增压器的振动响应频谱特征信息,结合涡轮增压器结构特征,对涡轮增压器主要振源识别结果进行分析验证。研究结果表明:连续小波变换方法可直观、精准识别涡轮增压器本体振源时频特征。在瞬态工况和稳态工况下,涡轮增压器本体振动受气动载荷激励冲击影响最大,主要表现为叶片通过频率处的空气冲击振动和高频宽频带的结构振动。在稳态工况下,涡轮增压器受转子质量不平衡激励影响明显,主要表现为转频及倍频处发生振动响应峰值现象。

The operation reliability of diesel engine and entire power system was seriously affected by the high frequency vibration of diesel engine turbocharger. The identification and analysis of main vibration sources for the turbocharger could effectively guide the vibration control and optimize the vibration response of body. For the turbocharger vibration response characteristics of high frequency, wide frequency band and time-varying unsteady state, the continuous wavelet transform method was used to carry out signal identification and analysis of dynamic vibration source under transient excitation because it had the advantages of time-frequency characteristics such as the multi-scale calculation and analysis frequency and the precise determination of occurrence time in signal processing. Combining the structural characteristics and working principle of turbocharger, the main vibration sources of turbocharger were identified and analyzed under the transient condition. The time-frequency characteristics of excitation were obtained including aerodynamic load and rotor mass imbalance. By analyzing the vibration response spectrum characteristic information of turbocharger under the steady-state condition of 50 513 r/min, the main vibration source identification results were analyzed and verified. The research results showed that the continuous wavelet transform method can intuitively and accurately identify the time-frequency characteristics of turbocharger vibration source. Under transient and steady conditions, the turbocharger vibration is mainly affected by the aerodynamic load excitation, which is characterized as the air impact vibration at the blade passing frequency and the structural vibration with high frequency and wide frequency band. Under steady-state condition, the turbocharger is significantly affected by the rotor mass imbalance excitation, which is characterized as the vibration response peak phenomenon at the rotation frequency and multiplication frequency.