Optimization design of piston structure for abnormal noise control in a single-cylinder gasoline engine

The noise characteristic of an entire single-cylinder gasoline engine was tested through acoustic spectral and intensity analyses to solve its abnormal noise problem in idling condition. Then, the abnormal noises were identified as piston impact noises caused by the anomalous dynamic performance of the piston mechanism. A piston multibody dynamic model was established on the basis of the key performance and the structure parameters of the piston to eliminate the abnormal noise. Then, the piston dynamic performance was improved by optimizing the piston structures. Analysis results showed that the lateral force, secondary kinetic energy, and friction power loss of the piston were reduced by approximately 51.3%, 40.2%, and 31.8%, respectively. Finally, the acoustic verification tests were implemented on the basis of the original engine when the optimized sample was manufactured and installed in the engine. The results showed that the abnormal noise was eliminated and the overall sound pressure level of the engine was reduced by 2.5dB(A) in idling condition. Meanwhile, the subjective evaluation results showed that the sound quality was obviously improved. The dynamic performance of the piston could be improved by optimizing the piston structure to reduce the impact noise.