空氣汙染是國際上重大的議題，空氣污染可能導致人體的健康受損，而造成空氣汙染的很大一個原因就是由汽、機車及船舶所排放的廢氣所產生。隨著國家新的空氣汙染防制法提升，預計削減細懸浮微粒(PM2.5)、氮氧化物(NOX)及硫氧化物(SOX)，抵禦空氣品質差的問題。近年許多研究學者開發替代性燃料，並且探討如何減少汙染物質的排放，減少能源不足與環境破壞的問題。
選用異丙醇為柴油引擎的輔助燃料，是因為異丙醇擁有較高的蒸發潛熱、屬於富氧燃料及較低的熱值，這些特性能夠有效降低引擎的汙染物Smoke及NOx的排放，還能有效提升引擎性能；且不含有硫成份，故燃燒後不會有硫氧化物產生。本研究使用單缸直噴式柴油引擎加裝密閉式循環系統，於進氣處加熱及導入異丙醇，且用EGR來減少排放廢氣中NOx濃度。經由改變引擎轉速、負荷、KOH含量、進氣溫度及EGR比例進行交叉實驗，探討進氣處噴入異丙醇對密閉式柴油引擎性能與污染排放產生之影響。由模擬程式KIVA-3V,RELEASE2調整程式中的進氣組成，執行數值運算分析，探討進氣端添加異丙醇對密閉式柴油引擎特性與燃燒造成之影響，模擬結果中之汙染物質的計算與缸內壓力並與實驗數據相互印證。
實驗研究結果顯示，進氣處添加異丙醇可以改善引擎燃燒狀況，增加引擎燃燒壓力及熱釋放率，因而減少排放汙染物質中NOx及Smoke。進氣端加熱能夠抑制排放物中HC和CO濃度，並且導入EGR可以減緩NOx濃度的上升。提升CCDE中的KOH比率可以吸收排放汙染物質中的二氧化碳。從模擬結果得知，進氣處添加異丙醇能夠提高缸內壓力、降低燃燒溫度及增加點火延遲，讓缸內中的混合氣更加均勻，改善燃燒。並從實驗與模擬結果，所得到結論可相互對應。

Air pollution is a major international issue that can endanger human health. The main cause of air pollution is exhaust emissions from cars, locomotives and ships. Regulations are expected to reduce fine suspended particulate matter (PM2.5), nitrogen oxides (NOX), and sulfur oxides (SOX) to address poor air quality. In recent years, many researchers have developed alternative fuels to explore how to reduce pollutant emissions, energy shortages and environmental damage.
Isopropanol was selected as the auxiliary fuel for diesel engines due to its higher latent heat of evaporation, oxygen-enriched fuel and lower heating value. These characteristics can effectively reduce engine soot and NOx emissions, thereby improving engine performance. Sulfur-free characteristics make the exhaust gas free from sulfur oxides. The work uses a single-cylinder direct-injection diesel engine equipped with a closed- cycle system and introduces isopropanol at the heated air intake. The EGR system is used to reduce the NOx concentration in the exhaust. Cross experiments were performed by changing engine speed, load, KOH content, intake air temperature, and EGR ratio. The author discussed the relationship between the performance and the pollutant emissions of a closed cycle diesel engine injected with isopropanol at the air intake. The numerical analysis of the intake air composition was performed with the simulation program KIVA-3V,RELEASE2. Combustion characteristics are obtained through simulation and experimental data to confirm each other.
The experimental results after the study show that the addition of isopropanol at the air intake can improve the combustion conditions of the engine, increase the cylinder pressure and heat release rate, and thereby reduce NOx and smoke in pollutant emissions. Intake air heating can suppress HC and CO concentrations emissions, and the introduction of EGR can slow the increase in NOx concentration. Increasing the KOH ratio in CCDE can absorb more carbon dioxide in the discharged pollutants. According to the simulation results, the addition of isopropanol to the intake can increase the pressure in the cylinder, reduce the bulk gas temperature, and prolong the ignition delay. Isopropanol injection makes the mixture in the cylinder homogeneous and improves combustion conditions compare to neat diesel. After comparing the results of experiments and simulations, the conclusions correspond to each other.

[1]. https://www.wri.org/blog/2019/12/co2-emissions-climb-all-time-high-again-2019-6-takeaways-latest-climate-data
[2]. J.B. Heywood, “Internal combustion engine fundamentals”, New York, U.S.A: McGraw-Hill Book Company, 1988.
[3]. A.O. Emiroğlu, M. Şen, “Combustion, performance and emission characteristics of various alcohol blends in a single cylinder diesel engine”, Fuel, Vol 212, pp.24-40, 2018.
[4]. Z. H. Huang, H. B. Lu, D. M. Jiang, K. Zeng, B. Liu, J. Q. Zhang and X. B. Wang, “Engine performance and emissions of a compression ignition engine operating on the diesel-methanol blends, ”Proc. Instn. Of Mech. Engrs. ,Part D: J. of Automobile engineering, Vol. 218, 2004.
[5]. J. Lee, S. Lee, S. Lee, “Experimental investigation on the performance and emissions characteristics of ethanol/diesel dual-fuel combustion”, Fuel, Vol. 220, pp.72-79, 2018.
[6]. D. Li, Z. Huang, X.C. Lu, W. Zhang, J. Yang, “Physico-chemical properties of ethanol–diesel blend fuel and its effect on performance and emissions of diesel engines”, Renewable Energy, Vol. 30, pp.967-976, 2005.
[7]. G. Belgiorno, G. Di Blasio, S. Shamun, C. Beatrice, P. Tunestal, M. Tuner, “Performance and emissions of diesel-gasoline-ethanol blends in a light duty compression ignition engine”, Fuel, Vol. 217, pp.78-90, 2018.
[8]. Y. Li, J.K. Gong, Y.W. Deng, W.H. Yuan, J. Fu, B. Zhang, “Experimental comparative study on combustion, performance and emissions characteristics of methanol, ethanol and butanol in a spark ignition engine”, Applied Thermal Engineering, Vol. 115, pp.53-63, 2017.
[9]. B. Prbakaran, D. Viswanathan, “Experimental investigation of effects of addition of ethanol to bio-diesel on performance combustion and emission characteristics in CI engine”, Alexandria Engineering Journal, Vol 57, pp.383-389, 2018.
[10]. C.H. Lin, “An applicable Study on Isopropyl Alcohol Mixed Fuel in Spark Ignition Engine”, Master's Degree, Department of Vehicle Engineering, National Taipei University of Science and Technology, 2012.
[11]. T. Ura, T. Obara, “Development of Depth Independent Closed Cycle Diesel Engine for an Autonomous Underwater Vehicle”, Proc, Unmanned Untethered Submersible Tech. pp. 1-9, 1991.
[12]. C.T. Shu, H.W. Wu, “Effects of Operating Parameters on Steady and Transient Behaviors of A Closed Cycle Diesel Engine”, Energy Conversion and Management, Vol. 47, pp. 2070-2080, 2006.
[13]. T.V. Babu, B.V. AppaRao, A. Kolakoti, “Engine combustion analysis of an IDI-diesel engine with Rice Bran Methyl Ester and Isopropanol Injection at suction end”, J. Multidisciplinary Engineering Science and Technology, Vol. 1, pp.254-261, 2014.
[14]. Y.B. Liu, B. Xu, J.H. Jia, J.A. Wu, W.W. Shang, Z.H. Ma, “Effect of injection timing on performance and emissions of DI-diesel engine fueled with isopropanol”, International Conference on Electrical, Electronics and Mechatronics, ICEEM 2015, 2015.
[15]. J. Gong, Y.J. Zhang, C.L. Tang, Z.H. Huang, “Emission characteristics of iso-propanol/gasoline blends in a spark-ignition engine combined with exhaust gas re-circulation”, Thermal Science, Vol. 18, pp.269-277, 2014.
[16]. A. Uyumaz, “An experimental investigation into combustion and performance characteristics of an HCCI gasoline engine fueled with n-heptane, isopropanol and n-butanol fuel blends at different inlet air temperatures”, Energy Conversion and Management, Vol. 98, pp. 199-207, 2015.
[17]. X.C. Lu, X.X. Zhou, L.B. Ji, Z. Yang, D. Han, C. Huang, Z. Huang,“ Experimental studies on the dual-fuel sequential combustion and emission simulation”, Energy, Vol. 51, pp.358-373, 2013.
[18]. S.J. Lan, “The Study on Diesel Engine Performance with Characteristic of Isopropanol Fuel Mixed with Super Diesel Fuel in Direct Injection Diesel Engine”, Master'sThesis, Department of Vehicle Engineering, National Taipei University of Science and Technology, 2012.
[19]. M.T. Luo, “A Study of the effect of iso-propanol additive on the performance and exhaust emissions for a diesel engine”, Master's Thesis, Department of Mechanical and Civil Engineering, Thesis of National Taiwan University of Oceanic University, 2005.
[20]. A. Fowler, “Closed-Cycle Diesel Engine for Underwater Work”, Marine Engineers, Review, pp.26-27, 1983.
[21]. T. Asada, M. Nagai, “Investigations on Recycle and Closed-Cycle Diesel Engines”, SAE, Vol.800964, pp.33-52, 1980.
[22]. J.O. Hawley, G.T. Reader, I.J. Potter, “Increasing the Submerged Endurance of a Naval Submarine using a Synthetic Atmosphere Diesel”, Proceedings of the 25th Intersociety Energy Conversion Engineering Conference, published by IEEE, pp. 525-529, 1990.
[23]. Z.X. Yin, “Study of Experiment and Simulation of Hydrogen Added at the Inlet Port on the Combustion Characteristics of Closed Cycle Diesel Engines”, Master Thesis, Department of Systems and Naval Mechatronic Engineering, NCKU, 2012.
[24]. H.W. Wu, Z.Y. Wu, J.Y. Yang, R.H. Wang, W.H. Lin, “Combustion characteristics of a closed cycle diesel engine with different intake gas contents”, Applied Thermal Engineering, Vol. 29, pp.848-858, 2009.
[25]. H.W. Wu, R.H. Wang, Y.C. Chen, D.J. Ou, T.Y. Chen, “Influence of port-inducted ethanol or gasoline on combustion and emission of a closed cycle diesel engine”, Energy, Vol. 64, pp.259-267, 2014.
[26]. N. Dimitrakopoulos, G. Belgiorno, M. Tuner, P. Tunestal, G. Di Blasio, “Effect of EGR routing on efficiency and emissions of a PPC engine”, Applied Thermal Engineering, Vol. 152, pp.742-750, 2019.
[27]. M. Koegl, B. Hofbeck, S. Will, L. Zigan, “Influence of EGR and ethanol blending on soot formation in a DISI engine”, Proceedings of the Combustion Institute, Vol. 37, pp.4965-4972, 2019.
[28]. M. Fathi, R.K. Saray, M.D. Checkel, “The influence of Exhaust Gas Recirculation (EGR) on combustion and emissions of n-heptane/natural gas fueled Homogeneous Charge Compression Ignition (HCCI) engines”, Applied Energy, Vol. 88, pp.4719-4724, 2011.
[29]. K. S. Kumar, R. R. Thundil Karuppa, “Effect of fuel Injection Timing and Elevated Intake Air Temperature on the Combustion and Emission Characteristics of Dual Fuel Operated Diesel Engine”, Procedia Engineering, Vol. 47, pp. 1191-1198, 2013.
[30]. A. Sarkar, U.K. Saha, “Role of global fuel-air equivalence ratio and preheating on the behaviour of a biogas driven dual fuel diesel engine”, Fuel Vol. 232, pp. 743-754, 2018.
[31]. R.G. Papagiannakis. “Study of air inlet preheating and EGR impacts for improving the operation ofcompression ignition engine running under dual fuel mode”, Energy Convers Manage, Vol. 68, pp.40-53, 2013.
[32]. N. Li, C.N. Masano, R. Friedrich, E. Medda, S. Brandstetter, M. Kabesch, C. Apfelbacher, M. Melter, B. Sealbach-Gobel, I. Annesi-Maesano, D. Sarigiannis, “A model for estimating the lifelong exposure to PM2.5 and NO2 and the application to population studies”, Environmeantal Research, Vol. 178, 2019.
[33]. L. Kucka, E.Y. Kenig, A. Gorak, “Kinetics of the Gas-Liquid Reaction between Carbon Dioxide and Ydroxide Ions”, Ind. Eng. Chem, Vol. 41, pp. 5952-5957, 2002.
[34]. T. Shudo, H. Szuki, “Applicability of heat transfer equations to hydrogen combustion”, JSAE Rev, 23 pp. 303-308, 2002.
[35]. L.D. Cloutman, Dukowicz J.K., Ramshaw J.D., & Amsden, A.A., “CONCAS-SPRAY: A Computer Code for Reactive Flow with Fuel Sprays,” Los Alamos Scientific Laboratory Report, LA-9294-MS, 1982.
[36]. A.A. Amsden, T.D. Butler, P.J. O’Rourke, J.D. Ramshaw, “KIVA-AComprehensive Model for 2-D and 3-D Engine Simulation,” SAE 850554, 1985.
[37]. A.A. Amsden, “KIVA-3V, Release 2, Improvments to KIVA-3V,” Los Alamos National Laboratory report LA-13608-MS, May, 1999.
[38]. C. Liu, “An Experimental and Analytical Investigation into the Combustion Characteristics of HCCI and Dual Fuel Engines with Pilot Injection”, Ph.D. diss., Dept. of Mechanical and Manufacturing Engineering, Calgary Univ, 2006.
[39]. P.C. Pei, Y.F. Liu, “Asymptotic analysis on autoignition and explosion limits of hydrogen-oxygen mixtures in Homogeneous systems”, International Journal of Hydrogen Energy, Vol. 31, pp.639-647, 2006.
[40]. K. Seshadri, N. Peters, G. Paczko, “Rate-ratio asymptotic analysis of autoignition of n-heptane in laminar non-premixed flows”, Comb. & Flame, Vol. 146, pp. 131-141, 2006.
[41]. S. Liu, J.C. Hewson, J.H. Chen, “Nonpremixed n-heptane autoignition in unsteady counterflow”, Combustion and Flame, Vol. 145, pp. 730-739, 2006.
[42]. J.P. Holman, Experimental Methods for Engineers,Eighth Ediotion , McGraw Hill Publications, Americas,New York, 2012.
[43]. R.B. Abernethy, R.P. Benedict, R.B. Dowdell, ASME Measurement Uncertainty, ASME Journal of Fluids Engineering, Vol. 107, pp. 161-164,1985.
[44]. Environmental Analysis Laboratory EPA, ROC. EPA, http://www.niea.gov.tw /.