Accordingly, it was assumed that the change of the max. cylinder temperature in the actual engines was caused mainly by the dispersion of p_max/p_c in every engine rating, and then the values of T₄/T_s defined by the following equation (5), which is derived from equation (1), were calculated by means of the measured data of p_max/p_me, p_s/p_me and pmae/pc and of the other calculated variables.

The calculated results of T₄/T_s against p_max/p_c are shown in the figure (a) in Fig. 9. Here Ts represents the scavenging temperature, and the values of k₁₂=1.37, k₂₄=1.31 and η_m=0.95 are adopted. It is seen from this figure that the data in each group with the different values of pme and etc. get together fairly well respectively, and the slope of T₄/T_s against p_max/p_c in every groups are almost same.

(a) Relation between P_max/P_c and T₄/T_s

(b) Relation between T₄/T_s and NOx

Fig. 9 Relation between p_max/p_c and T₄/T_s and that between T₄/T_s and NOx

　

Also the measured values of NOx against T₄/T_s are shown in the figure (b). There are found the well correspondence between NOx and T₄/T_s in each group, although with the relatively large dispersion. Here the NOx values in each group are different each other against the same T₄/T_s. The reason of it is considered due to the different configuration of the fuel injection nozzle in each group.

As mentioned above, since the main reason of the scattering of NOx is considered due to the change of T_max cased*** by the dispersion of p_max/p_c at shop trials, the relations between NOx values and p_max/p_c in each group are examined. The results are shown in Fig. 10. As seen from this figure, the NOx values lie in the relatively well proportional relation with p_max/p_c.

　

4.3 Relation between NOx and p_me/p_me0

Here, it was assumed that the normal values of p_max/p_c against p_me/p_me0 in each group were given by the liner approximation curves obtained from the measured data shown in the figure (a) to (c) in Fig. 8. Then the compensation calculations of the NOx values regarding the dispersion of p_max/p_c were executed by means of the slope of NOx against p_max/p_c shown in Fig. 10. The compensated NOx values against engine speed n are shown in Fig. 11.

(a) group I

(b) group II

(c) group III

Fig. 10 Relations between p_max/p_c and NOx in each engine group

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