Internal combustion engines for an overhaul
Under the state of the art, an efficient way to achieve the drastic reductions prescribed by legislators in nitrogen oxide (NOx) emissions from internal combustion engines is to calibrate exhaust-gas after-treatment systems. For this purpose, an engineering model for turbulent heat and mass transfer was developed to account for the all important physical effects occurring in passenger cars' and commercial vehicles' engines. Based on detailed numerical studies of the flow and turbulence structure, the model developed within the MINNOX project was still simple enough to be implemented in Computational Fluid Dynamics codes. Importantly, the thermal imprint on the viscous layer near the wall bounding the flow was integrated for simulations of internal combustion engines as well as similar industrial applications. Verification of the newly developed model was achieved for idealised flow configurations through the comparison of numerically estimated predictions with benchmark experimental data provided by project partners from the King's College London. These experimental investigations were undertaken with the aim to improve the current understanding of pulsating flows and provide accurate design guidelines for more efficient heat exchangers. The effects of driving frequencies and amplitudes of imposed flow pulsations, as well as those of Reynolds number on measured quantities were investigated by means of a dedicated experimental facility. Periodic velocity perturbations could be introduced to the fluid flow within a closed-circuit flow visualisation facility through a rotating valve driven by an electric motor of variable speed. Designed and realised to specifically enable measurements of heat transfer and unsteady fluid flows, it is nevertheless envisaged that it will provide reliable experimental data for the refinement of turbulence modelling. Investigations on the potential use of flow pulsations as a means of heat transfer enhancement, leading to significant energy savings could be further extended to cover other engineering applications.
