Hao Zhi-yong

Study of engine noise based on independent component analysis

Independent component analysis was applied to analyze the acoustic signals from diesel engine. First the basic principle of independent component analysis (ICA) was reviewed. Diesel engine acoustic signal was decomposed into several independent components (ICs); Fourier transform and continuous wavelet transform (CWT) were applied to analyze the independent components. Different noise sources of the diesel engine were separated, based on the characteristics of different component in time-frequency domain.

Virtual design and performance prediction of a silencing air cleaner used in an I.C. engine intake system

This paper reports results of the authors’ studies on the virtual design method used in the development of low noise intake system of I.C. engine. The resulting high pass-by noise at level above the legislative target at full throttle when engine speed was around 5200 r/min necessitated a BEM-aided redesign task, following the typical process of design and development of an intake system. During the initial design, based on the acoustic theory and the requirements (1. The air flux of the redesigned should equal to or exceed the value of the original flux; 2. The filtering area must not be degraded), and considering the constraint of space in the engine compartment, total volume and rough internal dimensions were determined. During the detailed design, the exact internal dimensions of the air cleaner were determined, and an effective method was applied to improve the acoustic performance at low frequency. The predicted sound power of the intake system indicated that the objective of reducing the overall engine noise by minimizing intake system noise was achieved.

An Improved Flowchart for Gabor Order Tracking

Based on the simulations on the ability of the Gaussian-function windowed Gabor coefficient spectrum to separate order components, an improved flowchart for Gabor order tracking (GOT) is put forward. With the conventional GOT flowchart with Gaussian window, successful order waveform reconstruction depends significantly on the analysis parameters, such as the time sampling step, frequency sampling step, window length in point number, and try-and-error method is needed to find the appropriate analysis parameters. While with the improved flowchart, if the speed-time curve and order difference between the adjacent order components are known, 1) it can be judged whether there exist appropriate analysis parameters to allow for successful waveform reconstruction of all the order components within given order range and speed range, 2) if there exist appropriate analysis parameters, they can be found automatically.

ACTIVE CONTROL SIMULATION OF TORSIONAL VIBRATION FOR TURBINE-GENERATOR SHAFT SYSTEM BASED ON GLOBALLY OPTIMAL CONTROL ALGORITHMS OF QUADRATIC REGULATOR

Global optimal control algorithms of linear quadratic regulator is combined with torsional vibration theory of turbine- generator shaft system, and torsional vibration energy of shaft system and control energy are chosen as performance index of active control. The global optimal control theory with linear quadratic regulator is brought about to control the tortional vibration of the large turbine-generator shaft system. And space state equations on active control of torsional vibration of turbine-generator shaft system are constructed. A solution way on Algebraic Ricatti Equation is proposed to determine the feedback control input matrix. This method is to construct a Hamiltonian matrix and solve its eigenvalue. A simulation program on active control of torsional vibration for discrete system is compiled and simulation analysis on active control of torsional vibration is carried out in a shaft system of 200 MW turbine-generator to examine the active control effectiveness. The results of time domain analysis on active control of torsional vibration show that employing the global optimal control theory of linear quadratic regulator can effectively decrease torsional vibration and control torque input.

Study on High Efficiency Separation Oil Mist Separator

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