No abstract

Experiments were carried out in a direct injection compression ignition engine fueled with diesel-dimethylfuran blends. The combustion and emission performances of diesel-dimethylfuran blends were investigated under various loads ranging from 0.13 to 1.13 MPa brake mean effective pressure, and a constant speed of 1800 rpm. Results indicate that diesel-dimethylfuran blends have different combustion performance and produce longer ignition delay and shorter combustion duration compared with pure diesel. Moreover, a slight increase of brake specific fuel consumption and brake thermal efficiency occurs when a Diesel engine operates with blended fuels, rather than diesel fuel. Diesel-dimethylfuran blends could lead to higher NO x emissions at medium and high engine loads. However, there is a significant reduction in soot emission when engines are fueled with dieseldimethylfuran blends. Soot emissions under each operating conditions are similar and close to zero except for D40 at 0.13 MPa brake mean effective pressure. The total number and mean geometric diameter of emitted particles from dieseldimethylfuran blends are lower than pure diesel. The tested fuels exhibit no significant difference in either CO or HC emissions at medium and high engine loads. Nevertheless, diesel fuel produces the lowest CO emission and higher HC emission at low loads of 0.13 to 0.38 MPa brake mean effective pressure.

Droplet vaporization is an essential sub-process of fuel spray in diesel engines, which has important effects on combustion and emissions performance. Development of a simplified droplet vaporization model is necessary to simulate gas mixture formation in cylinder for lower computational costs, and it is also applicable in practical multi-dimension spray calculations for diesel engines. An empirical exponential equation is introduced in this paper to approximate the internal temperature profile of droplet instead of solving the partial differential equation for temperature distribution. Results indicate that the computational cost has been reduced by almost thirty percent in total. Also, the concept of effective diffusion is introduced by using an enlarged diffusivity to take account of the effect of internal circulations inside droplets. The calculated result of the simplified evaporation model has been compared with that of the infinite diffusivity model and one-dimensional model respectively. It shows that the calculation precision of the simplified model is among those two models.