## 5 Conclusions  
The impact of ammonia port injection on a gasoline/ethanol dual-fuel engine was investigated in this paper. The engine was numerically modeled in the AVL BOOST software and validated against experimental data obtained from physical engine tests. The presented results are an evaluation of the impact of ammonia port injection on a spark-ignition engine across a range of engine speeds with respect to engine performance parameters, such as net rate of heat release, engine power, equivalent BSFC and emissions such as nitrogen oxides, CO and HC emissions. The key conclusions of this study are as follows:  
* By adding ethanol to gasoline at various volume shares, the rate of engine nitrogen oxides production increased, while the BSFC decreased and the engine power was changed minimally compared to a single-fueled gasoline engine;
* The port injection of ammonia increased engine power up to 1.4%;
* The equivalent BSFC of the engine increased with the port injection of ammonia by 3% (at a 10% injection ratio);
* The engine combustion chamber cooled with the port injection of ammonia up to 50 K, which resulted in a significant reduction in engine nitrogen oxide emissions up to ~50% across the engine speed range;
* The share of fuel energy wasted through the exhaust increased by approximately 2% following the increase in ammonia injection up to 10%;
* The other engine emissions, such as CO and HC, increased by 30% and 21%, respectively, when ammonia was injected at a 10% ratio. However, this issue can be controlled by having an appropriate after-treatment system in place;
* The required minimum octane number of the main fuel for preventing knock decreased when ammonia was injected at a 10% injection ratio, indicating that the port injection of ammonia can positively affect the engine knock;
* The proposed combustion mode could be studied for heavy-duty diesel engines in future research, with possible positive impacts on efficiencies and GHG, since for passenger cars the efficiency is lower compared to conventional diesel combustion. Figure 15: Minimum fuel octane number requirement at various engine speeds at different fractions of ammonia. **Author Contributions:** Conceptualization, methodology, software, F.S., M.B. and A.Z. ; validation, and S.V.H. ; formal analysis, F.S., M.B. and T.B. ; resources, S.V.H. and M.B. ; writing--original draft preparation, M.B., F.S. and A.S.; writing--review and editing, M.B., A.Z. and T.B. ; visualization, F.S. and A.S.; supervision, M.B. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Acknowledgments:** AVL List GmbH support for proving the simulation tools for University of Salford through their University Partnership Program is greatly appreciated. Special thanks to Dina Motors company for their support during this research. **Conflicts of Interest:** The authors declare no conflict of interest. **Abbreviations**  
SOC Start of combustion BDUR Burn duration Crank shaft angle m Vibe shape a Vibe parameter CO Carbon monoxide HC Hydrocarbons NOx Nitrogen monoxide DME Dimethyl ether CAT Catalytic converter E Engine SB System boundary Cylinder CL Air cleaner PL Phenum MP Measuring point LHV Lower heating value (kJ/kg) E Ethanol A Ammonia BSFC Brake specific fuel consumption (g/kWh) R Injection ratio BMEP Brake mean effective pressure (bar) V Volume C Constant \(r\) Reaction rate ON Octane number P Pressure (bar) T Temperature (K) Subscripts PPM Post processing multiplier KM Kinetic multiplier iD Ignition delay b Burnt zone u Unburnt zone a Ammonia e Ethanol  
* _[PERSON] and [PERSON] (2019)_ [PERSON]; [PERSON] Experimental investigation and evaluation of using ammonia and gasoline fuel blends for power generators. _Appl. Ther. Eng._**2019**, _154_, 1-8. [CrossRef]
* [PERSON] (2013) [PERSON] Combustion characteristics and exhaust emissions in spark-ignition engine using gasoline-ammonia.