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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., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The rotary engine constitutes promising propulsion for unmanned aerial vehicles, and creating turbulence within the rotor chamber is an effective means to strengthen the combustion of this engine concept since it is characterized by a unidirectional flow from the trailing side to the leading side of the rotor chamber. Based on CFD modeling, this work proposed a novel turbulence-induced blade (TIB) configuration and carried out a feasibility assessment focused on this innovation for improving engine performance under different operation/design parameter conditions (spark timing, hydrogen enrichment, and compression ratio). The results of this work confirmed the benefit of this proposed configuration as a useful tool to enhance combustion characteristics and control emissions formation. When the TIB was arranged at the leading part of the rotor chamber, better turbulent flow could be formed in the desired location and actually enhanced the combustion. Compared with the no-blade rotor chamber, the indicated thermal efficiency of the leading-blade, middle-blade, and trailing-blade rotor chambers increased by 7.3%, 5.1%, and 0.8%, respectively. Further assessment of TIB benefits demonstrated that the introduction of the TIB could postpone the optimal spark timing, and effectively increase the pressure within the rotor chamber, and the later the spark timing is, the more significant the increment in the peak pressure. Compared with hydrogen-enriched rotary engines, the TIB is more sensitive to the combustion improvement of pure gasoline rotary engines, and the difference between the no-blade and leading-blade rotor chambers reduced notably in terms of emissions formation as hydrogen enrichment increased. It is recommended that a higher compression ratio could be realized by decreasing the chamber volume, thus producing better engine performance. The turbulence intensity in the leading-blade rotor chamber is higher than that in the non-blade rotor chamber, and the discrepancy shows an increasing trend with the increase of the compression ratio. The effect of the TIB on efficiency improvement and emissions reduction is negligible at a relatively higher compression ratio (9.6)., (Copyright © 2022 Elsevier Ltd. All rights reserved.)