Application of A Multiple-Step Phenomenological Soot Model to HSDI Diesel Multiple Injection Modeling

Multiple injection strategies have been revealed as an efficient means to reduce diesel engine NOx and soot emissions simultaneously, while maintaining or improving its thermal efficiency. Empirical soot models widely adopted in engine simulations have not been adequately validated to predict soot formation with multiple injections. In this work, a multiple-step phenomenological (MSP) soot model that includes particle inception, surface growth, oxidation, and particle coagulation was revised to better describe the physical processes of soot formation in diesel combustion. It was found that the revised MSP model successfully reproduces measured soot emission dependence on the start-of-injection timing, while the two-step empirical and the original MSP soot models were less accurate. The revised MSP model also predicted reasonable soot and intermediate species spatial profiles within the combustion chamber. In addition, the revised MSP model provides information about the soot particle number density, soot precursor radical, and acetylene growth species concentration during diesel combustion. This provides more insight about the soot formation process which is helpful to emissions reduction studies.