*3.1. Particle Number Emission Indices*

The average PM number emission indices (EIN) and their associated error bars were calculated from EEPS data, as provided in Figure 1, for the different rotation speed. The average EIN for 1800 rpm decreased from 1.9 × <sup>10</sup><sup>15</sup> to 9.3 × 1013 particles per kilogram of fuel as the engine torque increased from 15 to 55 Nm. From a 55 Nm average, EIN increased to 5.9 × 1015 for 95 Nm, which was the highest EIN for 1800 rpm. The figure shows that, in comparison to the other rotation speeds, 1800 rpm had the highest EIN values over the entire range of engine torque. For 2100 rpm rotation speed, EIN values decreased from 8.9 × <sup>10</sup><sup>13</sup> to 6.8 × 1013 particles per kilogram of fuel as the engine torque increased from 15 to 115 Nm. About torque equal to 144 Nm regeneration of DPF (diesel particulate filter) has become. It caused an increase of EIN value from 6.9 × <sup>10</sup><sup>13</sup> to 4.9 × 1014 particles per kilogram as the engine torque increased from 115 to 144 Nm. The average EIN for 2400 rpm is after regeneration of DPF; thus, the average values of particles per kilogram of fuel are significantly lower than for 1800 and 2100 rpm. The values of EIN decreased from 1.9 × 1013 to 1.0 × <sup>10</sup><sup>13</sup> as the engine torque increased from 15 to 135 Nm.
