Research On Diesel Engine Noise And Vibration Signal Feature Extraction And Low Noise And Vibration Block Structure Improvement

Vibration noise control of diesel engine is a systematic and complexinterdisciplinary project. In this research area, there are two key parts. The first part isidentification of vibration noise source and its characteristics while the second part isrelation between vibration noise source and vibration noise of the whole diesel engine.In order to better control vibration and noise, based on two parts, structuraloptimization and measuring of vibration noise signal energy distribution have to beapplied to predict and control vibration and noise from the initial design period.Based on Vibration Control and Optimization Design of Coupling Engine Piston,a National Natural Science Foundation of China project and Identification of NoiseSource and Structural Optimization of Gas Engine with the Purpose of LoweringNoise, a Natural Science Foundation Project of Tianjin, concentrating on the featureextraction, calculation of contribution degree, signal energy appraisal, characteristicprediction, transfer characteristic and structural improvement design of block, thispaper carries out research work on source identification and overall control of dieselengine vibration with the goal of creating engine with low vibration noise. Withtime-frequency technique, this paper conducts the feature extraction of vibration andnoise, sources identification and contribution degree calculation, and then renders ananalysis method for vibration and noise sources identification and contribution degreecalculation of diesel engine. Based on signal features extracting research, this paperintroduces in signal energy appraisal index, analyses the main vibration signalfrequency components of diesel engine, establishes sensitivity factor calculationmodel, analyses vibration signal source which is related closely to oil supplyparameters, and the change rule of the vibration source energy characteristics. Thispaper establishes the prediction procedure of the whole diesel engine, analysesvibration transmission and carries out diesel engine structure research with lowvibration noise as the goal, which has been proved to be effective on this virtualplatform. The research results are listed below:1. On the basis of wavelet analysis&empirical mode decomposition principlesand their calculation research, combining signal relativity analysis, combined modefunction and wavelet packet technology, this paper works out signal abstraction method and further points out questions to be noticed during the process. The methodis proved to be practical and effective in the application research of signal characterextraction.2. Aiming at the shortcomings of single channel and low signal noise ration ofdiesel engine in extracting signal source, this paper renders the coordinated signalsource identification method based on empirical mode decomposition andindependent component analysis, overcoming the assumption of less signal sourcethan observed ones and avoiding intrinsic mode function mode mixing due to noiseinterference. Meanwhile, aiming at contribution degree problem of different signalsource, this paper defines independent component contribution degree andcontribution matrix based on blind source separation model based on ICA andEMD-ICA, works out the contribution degree by various noise source which has beentested to be correct.3. This paper builds a set of vibration noise prediction procedure, namelyMultibody dynamics (MBS)-Finite element method (FEM)-Method of ExternalVibration Velocity. Through the analysis procedure, this paper works out the value ofvibration severity and radiation noise acoustic power of main engine parts, analyzesthe relation between excitation and engine vibration signal, which have been provedto be accurate in the test of spectrum of average sound pressure level. Meanwhile, thispaper explores into engine transmission characters using transfer function and spectralcorrelation technique, and calculates vibration source’s contribution degree to engineblock using contribution degree calculation method. The application of the predictionprocedure allows us to predict vibration and noise of diesel engine under differentworking conditions, decreasing the testing work, providing an ideal research platformfor diesel engine excitation, transmission characters and mutual-relation betweenvibration signals.4. Based on diesel engine vibration signal extraction, introducing in signalenergy evaluation index (instantaneous energy, spectral analysis of instantaneous,amplitude acceleration energy, spectral analysis of amplitude acceleration energy andenergy change index), this paper analyses the main vibration signal frequencycomponents of diesel engine, and evaluate the speed and load condition influencing tovibration signal energy feature by the energy change index; meanwhile, builds thecalculation model of sensitive model. this paper analyses and identifies the vibrationsource of diesel engine, which is closely to the supply oil parameters (fuel supply pressure), and according to the influence principles on engine vibration signal energyunder different fuel supply pressure, which will favor proper selection of engine fuelsupply pressure and realize vibration and noise control.5. This paper establishes the virtual simulation platform and structuraloptimization procedure to decrease vibration and noise of diesel engine. Firstly, thispaper carries out multi-target optimization to engine parts based on the slowestvibration speed and then analyzes different design parameters’ influence on vibrationspeed and displacement. Secondly, this paper explores into the application of topologyand shape optimization in diesel engine structural design, which turns to be rational intest. Finally, this paper works out structural characters evaluation methods based onsignal features to evaluate the change of vibration signal energy and frequency beforeand after structural improvement. The procedure enables us to design rationallow-vibration engine parts, enhance calculation accuracy and improves automationdegree of design.