Diesel Engine Stable Parts Vibration Transfer Characteristics Analysis

The diesel engine is widely used in the field of mechanical structure, such as ships, vehicles and other high-power machine. The vibration and noise of diesel engine in operating condition become urgent research content. Research on diesel engine vibration transfer characteristics has important practical value and scientific significance.Diesel engine stable parts as a kind of compositional elastomer, which mainly including the oil pan, bearing, cylinder head and other parts; The vibration transfer characteristics analysis of compositional elastomer is transfer path analysis. That is to determine the main flow path of vibration and the analysis of contribution amount. Vibration signal has a number of different paths in composite elastomer. Each path is difficult to use the exact physical analytical to express, but can be represented by the mathematical model, such as transfer function. Using a finite element analysis results data to identify the transfer function method, the acceleration signals of response output points of diesel engine can be obtained by using the transfer function of the structure, which are used to analyze the transfer path contribution.In this paper a kind of inline four-cylinder diesel engine was carried out the following research:1. To illustrate the effectiveness of the method of transfer function identification based on finite element analysis of elastomer, first make a cantilever beam as an example. The finite element model is established to determine incentive location, size and direction. The steady-state kinetics and transient dynamics is analyzed by ABAQUS software. Using the response analysis data to identify the parameter by the time domain and frequency domain method, according to the time-frequency characteristics of transfer function shows that the identification results are reliable.2. To establish finite element model of simple structure of diesel engine stable parts, analyze and determine the incentives, responsive to the position. According to the cantilever beam identification process obtains its transfer function. For the levy frequency domain identification method, compared with X, Y, Z direction of the transfer function of amplitude-frequency curve and CAE dynamics analysis response amplitude frequency curve, found the curve peak corresponding to each frequency point is tiny, identification result is reliable. Using ARM time domain identification method and MATLAB system identification toolbox to recognize the diesel engine vibration transfer function, the time history curve of the projection signal and the measured signal can reflect the output characteristic of structure.3. Analyzing the source of diesel engine vibration, the diesel engine stable parts vibration transfer path model is set up. Excitation signal acquired of bearing seat turn into time domain signal by Fourier transform. It is mainly concentrated in the low frequency range and the amplitude at the frequency of 17.56 Hz is the largest. The output signal of response point of each path is calculated by transfer function. Drawing the curve of the amplitude and frequency to the output signal and obtaining the vibration transfer path contribution under the different frequencies. The total output signal is calculated by vector superposition. Drawing the amplitude frequency curve of output signal, found that it is mainly concentrated in the low frequency range too. Therefore, the change of frequency component of the incentive signal from bearing seat which is spread in diesel engine stable parts is little.