Non-premixed compression ignition direct injection (CIDI) and premixed spark ignition (SI) combustion belong to the class of conventional combustion technologies. The CoMo group utilizes demonstrated turbulent combustion sub-models within CFD in addition to the in-house development of new methods to account for the turbulent closure issues. Furthermore, phenomenological models to simulate CIDI and SI combustion are also being tested. This development is focused at providing a better insight into dual-mode engines where conventional combustion modes are integrated with advanced HCCI-ish technologies.
The activities of the CoMo engine research are aimed at combining the detailed population balance based soot modelling capability with the PDF-based stochastic reactor model. Such a seamless integration enables the calculation of detailed soot particle size distribution in the combustion chamber, which was developed keeping in mind the potential incorporation of particle number density, size distribution, morphology as well as composition of particulates within futuristic emissions regulations.
Soot particle size distribution in a Cummins B series engine, Injection at -10 CAD ATDC.
In the figure above, the sub-figure on the left shows:
- Direct injection at CAD ATDC in a lean air-fuel charge - evolution towards higher local equivalence ratios;
- Decrease in the local temperature due to evaporative cooling;
- Turbulent mixing taking into account localness in composition space;
- Ignition event: Local temperature shoots up following auto-ignition;
- Local richness in the regime of equivalence ratio, 2.0 to 4.0 and temperatures in the range of 1500 and 2000 soot formation.
The figure on the right shows the particle size distribution, (PSD) prediction as a function of crank angle degrees (CAD). Note that this PSD is bimodal in nature with inception of small soot particles in addition to larger particles as a result of accumulation mode.