## 4 Results and Discussion
At the same time, similar results are registered with the TR1 shape on the R2 operating condition, with an increase of 4.6% for diesel fuel and 3.5% for B20. These results occurred because, for all triangular shapes, the combustion durations are shorter and the combustion process is well situated relative to the region with minimum cylinder volume variation, leading thus to higher peak in-cylinder temperatures and increased efficiency values of engine operation. Using the BO2 shape, lower power was obtained. The brake power has almost the same value for both fuels on the R1 test condition, because the increase in fuel consumption of 4.1% when fuelling with B20 relative to diesel fuel is high enough to compensate for the decrease of 3.1% in the lower heating value. However, in the R2 operating state, the increase in fuel consumption of B20 is only 1.5% and this cannot compensate for its reduced lower heating value, the brake power standing smaller for all the injection shapes considered. Figure 10: Peak in-cylinder pressure rise rate variation by different shapes of ROI. The variation of brake-specific fuel consumption (BSFC) generated by the alteration of the injection rate shape is presented in Figure 12. The triangular shapes offering the highest engine brake power involve the lowest values of BSFC (high performance and efficiency). For these shapes, on R1 there are reductions in BSFC of 2.9% for both fuels, and for TR1 on R2 the reductions are 4.3% for diesel fuel, respectively of 3.5% for B20. The TH and BO2 shapes with minimum performances lead to maximum values of BSFC. There are not practically significant differences in the BSFC variation with the ROI shapes for B20 relative to diesel fuel, because the altering of the ROI shape does not significantly change the brake power variation when switching from diesel fuel to B20. The slightly elevated values of BSFC in the case of B20 usage, for all the ROI shapes considered, are determined by the higher amounts of fuel injected. The physical properties of biodiesel, notably viscosity and density, are responsible for the higher injected amounts of B20 fuel. In [13], it was also highlighted that the boot-like rate shapes which concentrate higher amounts of fuel at the end of the injection process produce a general increase in BSFC. Figure 13 shows the variation of nitrogen oxides (NO\({}_{\text{x}}\)) emissions depending on the ROI shape. The minimum values are obtained for the BO2 shape with decreases of 17.2%  
Figure 11: Brake power variation by different shapes of ROI. Figure 12: Brake-specific fuel consumption (BSFC) variation by different shapes of ROI. for diesel fuel and 11.2% for B20 on R1. Higher reductions of 27.8% for diesel fuel and 21.7% for B20 are registered on R2 due to the combined effect of smaller peak in-cylinder temperatures and the development of diffusion combustion. The maximum values of NO\({}_{x}\) are obtained for RT and TR1 shapes with average increases on R1 by 47.4% for diesel fuel, and 40.4% for B20, respectively on R2 by 62.3% for diesel fuel, and 55% for B20, because, with these shapes, the highest values of peak in-cylinder temperature are attained. For the R2 test condition, although the peak in-cylinder temperatures are lower when using B20 than diesel fuel, the NO\({}_{x}\) emissions are higher due to its superior oxygen content. However, this effect is overpassed, and the trend is reversed in the case of the R1 test condition because of the elevated differences existing between the two fuels in terms of peak cylinder temperatures and combustion durations. Comparable results regarding the NO\({}_{x}\) emissions when using diesel fuel were reported in [9; 10; 12; 13; 15; 18; 21; 22]. However, different results are presented in [7], where, for some increases applied at the beginning of the injection rate on certain boot shapes, the decrease of NO\({}_{x}\) emissions was registered. Figure 14 exhibits the values of Soot emissions relative to the ROI shapes.