Advanced Turbulence Model for SI Combustion in a Heavy-Duty NG Engine
2022-01-0462
03/29/2022
- Event
- Content
- In the recent years, the interest in heavy-duty engines fuelled 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 fuel 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 coupled with the fractal combustion pattern, already widely tested. The supplied SI heavy-duty CNG engine has a flat head derived from a diesel engine, so turbulence is generated primarily for swirl and squish unlike conventional tumble-assisted SI engines. Current commercially available predictive combustion models are mostly based on data derived from high speed passenger car engines, where tumble is the primary driver for in cylinder turbulence. In this study, the turbulence model has been modified taking into account the greater reliance on squish and swirl instead of tumble. To achieve this goal, a 3D simulation campaign was carried out, for the same engine head geometry and valve opening, that allowed to validate the 1D turbulence model. A robust turbulence sub-model is essential to precisely know the TKE trend, so the Turbulence Intensity, which governs the laminar flame velocity of the fractal combustion pattern to which it is coupled. The numerical results are largely satisfactory and the equations of this turbulence model can be a valid basis for SI Heavy-Duty engine for simulating the Turbulence Kinetic Energy (TKE), generated by squish and swirl.
- Citation
- Riccardi, M., De Bellis, V., Bozza, F., Sforza, L. et al., "Advanced Turbulence Model for SI Combustion in a Heavy-Duty NG Engine," SAE Technical Paper 2022-01-0462, 2022, .