Advanced Turbulence Model for SI Combustion in a Heavy-Duty NG Engine

Marco Riccardi; Vincenzo De Bellis; Lorenzo Sforza; Carlo Beatrice; Fabio Bozza; Tommaso Lucchini; Mohsen Mirzaeian; Simon Langridge; Valentina Fraioli; Stefano Golini

doi:10.4271/2022-01-0384

In the recent years, the interest in heavy-duty engines fueled with Compressed Natural Gas (CNG) is increasing due to the necessity to comply with the stringent CO₂ limitation imposed by national and international regulations. Indeed, the reduced number of carbon atoms of the NG molecule allows to reduce the CO₂ emissions compared to a conventional fuel. The possibility to produce synthetic methane from renewable energy sources, or bio-methane from agricultural biomass and/or animal waste, contributes to support the switch from conventional liquid fuels to CNG.

To drive the engine development and reduce the time-to-market, the employment of numerical analysis is mandatory. This requires a continuous improvement of the simulation models toward real predictive analyses able to reduce the experimental R&D efforts.

In this framework, 1D numerical codes are fundamental tools for system design, energy management optimization, and so on. The present work is focused on the improvement of the turbulence sub-model, originally conceived to describe turbulence evolution in tumble-promoting engines.

The turbulence model is here developed with reference to a SI heavy-duty CNG engine derived from a diesel engine. In this architecture, due to the flat cylinder head, turbulence is generated primarily by swirl and squish flow motions unlike conventional tumble-assisted SI engines.

To extend the turbulence model, a 3D simulation campaign was carried out aiming at extracting the information for model conceptualization and validation.

The turbulence sub-model demonstrated to properly predict turbulence and swirl/tumble evolution under various operating conditions, without the need for any case-dependent tuning. It hence presented the potential for appropriately support the predictive capabilities of any combustion model for SI heavy-duty tumble- and swirl-promoting engines.

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Advanced Turbulence Model for SI Combustion in a Heavy-Duty NG Engine 2022-01-0384

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