Effect mechanism and quantitative analysis of injector faults on diesel engine performance

The nozzle deterioration, caused by carbon deposition, cavitation erosion, and other reasons, has a great influence on the power performance, emissions, and thermal load of the direct injection (DI) engine. To understand the manifold effects of nozzle fault on engines, a systematic explanation for the diverse fault phenomena and effect mechanism of nozzle abnormality on the engine performance is needed. The joint action of orifice diameter and fuel spread direction on the performance of a double-swirl diesel engine are numerically revealed and decoupled. The results show that the engine power performance is mainly affected by the change of orifice diameter, while the abnormal spray direction has a great influence on the emissions and the piston surface thermal load. Insufficient spray tilt angle leads to a more concentrated fuel distribution because the fuel of the faulty orifice is not effectively channeled and dispersed by the circular ridge, which causes a 15.29% increase in NO_x and an 8.73% increase in soot emissions. Spray circumferential offset leads to increased soot, decreased NO_x, and slightly decreased power due to asymmetric fuel distribution. Some fuel is directly injected and burned in the clearance between the piston crown and cylinder head due to the abnormal spray direction, which causes the maximum heat flux at the piston crown to be about 1.8 times that under normal state, greatly increasing the possibility of piston damage. In contrast, the spray circumferential offset mainly causes the position change of the thermal load, but not the magnitude change.