<p>Diesel engines have been used in lot of vehicles and power generation units since a long time due to their less fuel consumption and high trustworthiness. With reference to upcoming emission norms, various engine out emissions have proved to be causing adverse effect on human health and environment. Soot, or particulate matter is one of the major pollutants in diesel engine out emissions and causes various lung related issues. There have been efforts to reduce the amount of soot generated using after-treatment devices like diesel particulate filter (DPF) to filter out particles and get clean tailpipe emissions. These technologies increase load on the system and involves additional maintenance. Also, deposition based soot sensors have been found to be inoperative in certain scenarios like cold start conditions. In this research work, an effort has been made to develop a phenomenological model that predicts soot mass generated and a controller to minimize the same. The process of soot generation involves soot formation phase that includes sequence of chemical processes like fuel pyrolysis, nucleation, surface growth, coalescence and agglomeration. This phase is followed by soot oxidation phase in which the soot formed is oxidized due to remaining oxygen. The model uses in-cylinder conditions such as pressure, bulk mean temperature, fuel mass flow rate and injector orifice diameter. These parameters are used to estimate significant characteristics like fuel spray angle, liquid length, lift-off length, temperature distribution and thermodynamic equilibrium and equivalence ratio. The liquid length also depends on certain thermodynamic properties of air-fuel mixture such as their densities, initial and final enthalpies at equilibrium, etc. &nbsp;The mass rate of soot formation is mainly dependent on equivalence ratio and in-cylinder conditions whereas mass rate of soot oxidation is a function of net soot mass and oxidation temperature. The difference between these two yields the gross rate of soot generation at engine out end. &nbsp;Furthermore, the generated soot mass is compared with benchmark results for specific load conditions and appropriate controller is designed to minimize this tradeoff. The control parameter being used here is fuel rail pressure which controls the lift-off length and ultimately equivalence ratio which predicts mass of soot generated in formation phase. Thus, this model can be used for a wide range of diesel engines not only for soot mass prediction but also to control to soot mass formed and as a result, reduce load on after treatment devices. The approach presented in this research work is generic and can be operated as stand-alone system or an integrated subsystem in a higher order control architecture. &nbsp;&nbsp;</p>

A Control Oriented Soot Minimization Model for Diesel Engines Using an Integrated Approach

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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