Diesel Engine Valve Clearance Fault Diagnosis Based on Improved Variational Mode Decomposition and Bispectrum

Xiaoyang Bi,Shuqian Cao,Daming Zhang

doi:10.3390/en12040661

Abstract

The evaluation and fault diagnosis of a diesel engine’s health conditions without disassembly are very important for diesel engine safe operation. Currently, the research on fault diagnosis has focused on the time domain or frequency domain processing of vibration signals. However, early fault signals are mostly weak energy signals, and the fault information cannot be completely extracted by time domain and frequency domain analysis. Thus, in this article, a novel fault diagnosis method of diesel engine valve clearance using the improved variational mode decomposition (VMD) and bispectrum algorithm is proposed. First, the experimental study was designed to obtain fault vibration signals. The improved VMD method by choosing the optimal decomposition layers is applied to denoise vibration signals. Then the bispectrum analysis of the reconstructed signal after VMD decomposition is carried out. The results show that bispectrum image under different working conditions exhibits obviously different characteristics respectively. At last, the diagonal projection method proposed in this paper was used to process the bispectrum image, and the fourth order cumulant is calculated. The calculation results show that three states of the valve clearance are successfully distinguished.

Highlights

Abnormal valve clearance is one of the most common faults in the valve mechanism of a diesel engine [1]. It can cause valve switch timing changes, affect the quality of air exchange in the cylinder, cause combustion deterioration, and affect the emission and economy of the diesel engine. It is of great significance for condition monitoring and fault diagnosis of diesel engine valve clearance
This paper presented a new fault diagnosis method for diesel engines based on improved variational mode decomposition (VMD), bispectrum and fourth-order cumulant that employs a cylinder head vibration signal
The research results indicate that the valve clearance fault characteristics can be extracted from the vibration signals clearly

Summary

Introduction

Abnormal valve clearance is one of the most common faults in the valve mechanism of a diesel engine [1] It can cause valve switch timing changes, affect the quality of air exchange in the cylinder, cause combustion deterioration, and affect the emission and economy of the diesel engine. It is of great significance for condition monitoring and fault diagnosis of diesel engine valve clearance. The vibration signal of diesel engine cylinder head contains much information about working state and fault characteristics. Extracting proper characteristic parameters from the vibration signal can effectively identify the working state and related faults of a diesel engine [2,3,4]. In the early stage of the engine fault, the vibration characteristic energy which indicates the fault information is weak and cannot be extracted directly

Methods

Results

Conclusion