Search Results

Mechanical properties, formability and crash worthiness of a new sheet steel having an ultrafine grained (UFG) multi-phase (MP) microstructure are shown. The fabricated UFG-MP steel showed significant work hardening caused by deformation induced martensitic transformation of retained austenite, which resulted in a combination of high strength and large tensile elongation. It was confirmed by dynamic collapse test and FEM simulation that the large work hardenability of the UFG-MP steel promoted compact mode collapse that improved the absorbed energy.

The objective of the present study is to elucidate the combustion process of partial premixed charge compression ignition (PCCI) combustion using multiple injections in diesel engines. The effects of the ratio of the quantity of fuel used in the first and second injections, and the injection dwell time on heat release rate, soot and nitrogen oxide (NOx) formations are investigated in simulated partial PCCI combustion using a constant-volume vessel. N-heptane is used as fuel. The experiments are carried out under an ambient condition of 2 MPa and 900 K, which simulates a PCCI-like heat release rate with long ignition delays. The oxygen concentration is set to 21 and 15% to simulate conditions without and with exhaust-gas recirculation (EGR), respectively. The fuel quantity in the first injection is varied between 10 to 40% of the total fuel quantity, and the injection dwell is varied between 0.5 to 2.0 ms.

A diesel combustion model for CFD simulation is established taking into account the auto-ignition process of a non-homogeneous mixture. In a previous paper, the authors revealed that the non-homogeneity of a fuel-air mixture has a more significant effect on the auto-ignition process with respect to, for example, ignition delay or combustion duration, as compared to the turbulent mixing rate. Based on these results, a novel diesel combustion model is proposed in the present study. The transport calculation for the local variation of the fuel-air PDF is introduced, and the chemical reaction rate is obtained based on the local non-homogeneity. Furthermore, this model incorporates RANS-based CFD simulation of the spray combustion in a constant-volume vessel under a high-temperature, high-pressure condition. The results show that the combustion process is well described for a wide range of temperature and pressure conditions.