## 4 Results and Discussion
### Numerical Results  
Figure 11 shows the profiles of the range of combustion chamber pressure change with the crank angle for all fuel samples prepared at a load of 200 Nm. It can be observed that the burning rate increases due to the addition of nanomaterials resulting from the high Cetane number and short ignition delay, and this is due to the higher surface area of the nano additives and their catalytic effect. Developments in the combustion pattern after adding the nanomaterial were represented by an increase in the peak cylinder pressure. Figure 12 displays the most important changes in cylinder pressure (Pcy) during the combustion process with the crank angle for all fuel samples tested at a load of 200 Nm, where we notice an increase in Pcy for the nano fuel mixture compared to diesel fuel due to the increase in fuel consumption in the combustion process, along with the Pcy with an increasing proportion of nanoparticles in the biodiesel blend for the tested samples D80B20N50, D80B20N100, and D80B20N150. Figure 13 displays the peak cylinder pressure under the influence of nano-particles at different load conditions. The peak cylinder pressure of D80B20N50 at 50 ppm was a higher value from the biodiesel blend at different loads. Also, this behavior repeated for D80B20N100 and D80B20N150 at 100 and 150 ppm. The increases in the peak cylinder pressures for D80B20N50, D80B20N100, and D80B20N150 about D80B20 were 3%, 5% and 8%, respectively, at a load of 200 Nm. These results are consistent with the results of several researchers in [9; 17; 18]. Figure 10: Variation of the NOx emissions with the load for all fuel blend samples: D100, D80B20, D80B20N50, D80B20N100, and D80B20N150. Figure 11: Contours of cylinder pressure variation with the crank angle of all tested fuels at a load of 200 Nm. Figure 12: Variation of cylinder pressure with the crank angle of all tested fuels at a load of 200 Nm. Figure 13: Peak cylinder pressure of the diesel and biodiesel blend with nano additives at different loads. Figure 14 displays the contours of the temperature distribution for the diesel and biodiesel blends with nanomaterial (Al\({}_{2}\)O\({}_{3}\)) at 150 ppm D80B20N150 with the crank angle from combustion modes in numerical procedures. At a state engine load of 200 Nm and crank angle of 720 deg, the combustion temperature reached up to 1164 K inside the cylinder. While uniform distributions of combustion temperature were recorded inside the cylinder for all crank angles within the combustion cycle, it is clear from the figure that the best combustion was achieved by adding 150 ppm of nanomaterials to the fuel sample D80B20N150. The maximum temperature recorded from this combustion was about 1188 K. After comparing both pure diesel and the rest of the fuel samples, no high difference appeared in terms of temperature. Figure 15 presents the maximum temperature of all fuel samples at different loads. Through the simulation, the maximum temperature for D80B20 was found to be higher than that for D100; this was due to the higher hydrocarbon values of D80B20. Nano additives caused a decrease in temperatures in the combustion of biofuels. Figure 14: Contours of cylinder temperature variation with the crank angle of B20N150 at a load of 200 Nm. Figure 15: Max. temperature of the diesel and biodiesel blend with nano additives at different loads. Figure 16 shows the contours of the burn charge velocity distribution during the combustion cycle using D80B20N150. The profiles describe that the low value of charge velocities were recorded in the center portion of the cylinder compared to the near-piston edge region. The main cause of this behavior was the lower swirl value during the compression stroke and combustion. Generally, the data of recorded swirl values are higher through the intake stroke due to suction operation, while there is a reduction during compression and combustion strokes. But there is swirl enhancement after the fuel charge injection by fuel diffusion.