Simulation study on multi-mode misfire fault of diesel engine

To address the high experimental costs and data acquisition challenges in misfire fault diagnosis of high-speed diesel engines, this paper proposes a high-fidelity numerical simulation model based on Matlab/Simulink. The model employs harmonic order analysis for misfire fault diagnosis, significantly improving data acquisition efficiency compared to conventional fault detection methods. By integrating torsional vibration characteristics, the dynamic influence of misfire faults on harmonic excitation torque was systematically investigated. The results reveal that under normal operating conditions, the crankshaft speed spectrum is dominated by principal harmonics (e.g., 2.5th order) and their multiples, while non-principal harmonics exhibit negligible amplitudes. Misfire events disrupt the amplitude equilibrium across 0.5-7.0 harmonic orders: single-cylinder misfires can be precisely localized through amplitude and phase features of a single harmonic (e.g., 0.5th order), whereas dual-cylinder misfires require comprehensive analysis of multi-harmonic amplitude variations for classification. Simulation results demonstrate that synchronous energy spectrum analysis effectively extracts fault features, though model boundary conditions impose limitations on distinguishing specific fault patterns. This study provides low-cost and high-efficiency data support for the diagnosis of diesel engine misfire, establishing a foundation for intelligent diagnostic algorithms, which is significant for enhancing the operational stability of high-speed diesel engines.