Effect of ultrasonic-fed time on combustion and emissions performance in a single-cylinder engine

In this study, a numerical simulation method for multi-field coupling is proposed in which the ultrasonic is physically fed in the combustion chamber of a gasoline engine. The fine-tuning regulation of activity and reaction paths of gas-liquid two-phase (GLP) fuel is studied by using ultrasonic under in-cylinder complex conditions. The three-dimensional (3D) computational fluid dynamics (CFD) model of the original engine is calibrated, based on the bench test data. The multi-field coupling model of the sound field and combustion field is established by embedding the feature of the sound source surface in the combustion chamber. The ultrasonic with 20 kHz frequency and 100 μm amplitude is fed into the combustion chamber by using the dynamic grid technology. By comparing the simulation results of four ultrasonic-fed schemes (S1∼S4) and ultrasonic-free scheme (No), it is concluded that compared with the No scheme, the average turbulent kinetic energy (TKE) of the schemes S1, S2, and S3 are all increased by 23.2% at the top dead center (TDC), the peak pressure of the schemes S1 and S2 are both increased by 0.58 MPa. The CO and soot formations of scheme S1 are the lowest at 6.5% and 6.1%, respectively, compared with the No scheme. The reasonable use of ultrasonic can promote the fuel oxidation and combustion process, and accelerate the formation of the OH radicals. The ultrasonic-fed has a significantly quantitative control effect on fuel activity and oxidation reaction paths within 10 ms, under the in-cylinder transient and complex combustion condition of the gasoline engine.