Figure 10 shows comparison of the emission characteristics against injection timing at high load of Pe=0.7MPa on the condition of injection pressure of Po=50MPa. Comparison is made between the fuels AR0CN56 and AR38CN55, which are the same cetane number and different aromatic content. Reduction of NO and increase of smoke, particulate and fuel consumption are seen for both fuels at retarded injection timing. In particular, fuel with aromatics produces higher NO and particulate emissions. The increase of particulate mainly comes from the increase of SOLID. The difference of NO and particulate concentration between the two fuels keeps same level with changing injection timing θi.

The effect of aromatics is investigated for the case of the fuel with low cetane number. Figure 11 shows the emission characteristics for the fuels AR0CN43 and AR38CN43. These fuels have the low cetane number of CN43 and different aromatic content. On the condition of Po=50MPa, high aromatic content fuel AR38CN43 produces higher NO and particulate emissions than AR0CN43, which is the same trend in the case of high cetane number fuel of CN55.

　

Fig.9 Effect of Aromatics On Combustion Characteristics (CN55)

　

Fig.10 Effect of Aromatics and Injection Timing on Emission Characteristics (CN55)

　

Fig.11 Effect of Aromatics on Emission Characteristics (CN43)

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