## 4 Result and Discussion
### Port Injection of Ammonia  
Figure 6 shows the engine power trend when ammonia is injected in different fractions at different engine speeds for the E20 fuel. As can be seen, ammonia injection had a small positive impact on engine power. The variation in engine equivalent BSFC caused by the injection of ammonia is also shown in Figure 7. The port injection of ammonia showed a positive impact on BSFC via a slight increase in engine equivalent BSFC. At the maximum ammonia injection (A10), the engine equivalent BSFC increased up to approximately 3%. Figure 4: Engine equivalent BSFC at various engine speeds at different fractions of ethanol. Figure 3: The engine power at various engine speeds at different fractions of ethanol. Figure 8 shows the shares of fuel energy converted to brake power, as well as the wasted energy through the friction loss, piston walls, cylinder head walls, cylinder liner walls, valves walls and exhaust gas at engine rated RPM (6000 RPM). As indicated in this figure, the percentage of the fuel energy converted to brake power decreased by 0.4% and 2% following increases in ammonia injection to 5% and 10%, respectively, due to the reduction in the in-cylinder pressure (Figure 9). On the other hand, the share of the fuel energy wasted through the exhaust increased by approximately 2% following the increment of ammonia injection up to 10%. Considering the ammonia lower heating value (LHV), the total fuel energy released during combustion increases following the increment in ammonia injection rate, as confirmed by Figure 10. So, the in-cylinder pressure increased minimally by increasing the ammonia injection rate, as is shown in Figure 9, resulting in a slight increment in engine power shown in Figure 6.  
Figure 5: Engine nitrogen oxide production at various engine speeds at different fractions of ethanol. Figure 6: Engine power at various engine speeds at different fractions of ammonia. The changes to engine nitrogen oxides emissions and peak cylinder temperature caused by the injection of ammonia at different engine speeds are shown in Figures 11 and 12, consecutively. As discussed before, the ethanol fraction increment in the fuel mixture results in a considerable increase in nitrogen oxides. However, ammonia injection causes nitrogen oxide reduction, as shown in Figure 11. The injection of ammonia up to 5% and 10% led to engine nitrogen oxide reductions of 25% and 48%, respectively, on average at various engine speeds for E20. Figure 8: The energy shares of fuel energy converted to brake power and friction, and that wasted at engine rated RPM. Figure 7: Engine equivalent BSFC at various engine speeds at different fractions of ammonia. The main parameter affecting nitrogen oxide production is the in-cylinder combustion temperature. As demonstrated in Figure 12, the engine in-cylinder temperature was reduced with the injection of ammonia, which led to the observed nitrogen oxide reduction. The main cause of nitrogen oxide reduction is the decrement in engine volumetric efficiency, caused by the injection of ammonia. By increasing the ammonia injection ratio up to 10%, the engine in-cylinder temperature decreased by approximately 50 K, across the engine speed range. Figure 4:0 The net rate of heat release in various crank angles at engine rated RPM. Figure 4:1 The in-cylinder pressure in various crank angles at engine rated RPM. Figure 13 demonstrates the effect of ammonia port injection on CO emission at various engine speeds. The injection of ammonia resulted in a reduction in in-cylinder temperature, as presented in Figure 4:2 This reduction in in-cylinder temperature will impose a negative effect on engine CO due to the extension of unburnt zones, which directly affects engine CO production. Our results show that an increase in ethanol fraction in the fuel mixture results in a significant decrease in the CO generation rate.