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The model of bio-diesel fuel's free spray was founded by using three-dimensional Computational Fluid Dynamics (CFD) software. The distance of fuel jet penetration and sauter mean diameter (SMD) of bio-diesel fuel spray were computed and discussed. The atomization progress of fuel jet was simulated and the pictures of high speed photography were analyzed and compared in detail. The results showed that the cone angle of bio-diesel fuel was smaller than that of diesel fuel nearly 3 degrees. The high speed photograph of fuel jet along with time was similar to the simulated results. The distance of fuel jet penetration and SMD of bio-diesel fuel was different from that of diesel fuel, and the differences changed along with the time. We found that the main reasons were that the density and viscosity of bio-diesel fuel were greater than that of diesel fuel. The fact will have great effect on the combustion and performance of the engine.

An expert system for analysing the performance and diagnosing faults of d.I. diesel engine is presented in this paper. This system consists of three parts. First is the transient data acquiring part by which the incylinder pressure, fuel pipe pressure and other parameters can be acquired through the A / D transforming circuits. Second is the simulative calculation and analysis part by which most of the parameters, such as the fuel injection rate, fuel heat release rate etc. can be calculated. Third is the expert diagnostic part established on the fuzzy theory, which is applied to evaluate the matching relations among various transient parameters. Some faults of engine can be detected by this part. Furthermore, the proposals to improve the performance of engine can be put forward by this system.