Study on Feature Extraction Method for Diesel Engine Valve Faults

Abstract

Valve faults diagnosis technique of a diesel engine is studied deeply in this paper. The experiment of valve clearance and air leakage faults are done in a diesel engine, and cylinder head vibration and transient speed signals are measured synchronously on normal and fault conditions respectively. These signals are used to feature extraction. In order to avoid the leakage and aliasing of vibration signal’s frequent spectrum, resample method based on order tracking is proposed, and vibration signal was transformed from time domain to crank angle domain accurately. Considering the non-stationary characteristic of vibration signal, a series of intrinsic mode functions with different scales were obtained using the empirical mode decomposition method, and fault features parameters were extracted through 3D Hilbert spectrums of the intrinsic mode functions. Experimental results show that the method can effectively extract fault features of diesel engine and use them to realize the valve system faults diagnosis further.

Analysis on the failure mechanism of flying hammers in nuclear power plant steam turbines

“…Mechanical overspeed protection device is composed of centrifugal flying hammer, Angle valve, brake device and other parts. The flying hammer is mainly subjected to centrifugal force FL and spring force FT during operation [3] . The structure and installation diagram of the flying hammer is shown in Figure1.…”