生質柴油的特性與石化柴油非常相近，因此在現有的柴油引擎中並不需改裝即可添加且燃燒運轉，且生質柴油的黏度大於石化柴油，可增添引擎元件間的潤滑性。目前已有國家使用 B2 、 B5 少比例之生質柴油於民生交通工具上，且生質柴油的來源可為廢食用油、大豆油等可藉由回收或種植方式取得，具有環保的優勢。而生質柴油的優點為十六烷值較石化柴油高，較容易燃燒、燃燒時間點提前且燃燒品質較佳，但生質柴油中含有氧成分，所以在燃燒後會產生較多的氮氧化物排放。本研究主要探討不同比例的生質柴油在目前商用柴油引擎中的燃燒行為與對引擎性能與排放汙染之影響，期望本研究成果能夠對未來的新一代生質柴油引擎發展有所貢獻。

本研究將利用真實柴油引擎計算流體力學模型進行不同比例生質柴油之研究，研究中包括了引擎中的物理現象、流場變化、能量變化及使用不同比例生質柴油之燃燒行為分析探討缸內壓力、燃燒熱釋放率和 NOx 排放汙染等。本研究使用軟體內建之引擎模型、經驗模型、數學模型、NOx 模型等，進行模擬引擎作動，進氣、噴油、燃燒行為後，對模擬結果進行分析比較。因此本研究將對於穩態之數值模擬進行研究分析，當數值模擬結果達到穩態條件下，將進行冷流場穩態實驗與數值模擬的數據分析比對驗證，當確認冷流場的驗證與實驗相符後，將進行使用不同比例生質柴油進行燃燒行為分析，其中包含了缸內壓力曲線、缸內溫度曲線、燃燒熱釋放率，並與實驗作比對驗證。

最後將利用此一有效性數值模型進行不同生質柴油之熱流場燃燒行為並觀察氮氧化物排放汙染物生成與溫度場的關係與分析比較，觀察到燃燒熱釋放率曲線與汽缸內溫度場變化關係，進而了解到氮氧化物生成的關係，並希望透過此一數值模型進行不同比例生質柴油燃燒，而預測到氮氧化物污染物排放。

Since the thermophysical properties of biodiesel blends are close to that of No 2 diesel oil, they can be used and combusted in existing diesel engines without any modification directly. In addition, biodiesel blends help improve the lubrication between engine parts due to their higher viscosity. Currently, B2 and B5 biodiesel blends are used in vehicles for civic transportation in many countries. Biodiesel blends can be converted from vegetable oils such as soybean oil and waste oil. Therefore, they are good for environment protection. Furthermore biodiesel blends have higher cetane rating compared to diesel fuels, they are more ready-to-burn and they exhibit better combustion quality. On the other hand, they have the disadvantages of producing higher harmful NOx emission due to the oxygen content in biodiesel blends. The major purpose of the current study is to investigate the combustion behaviors of various biodiesel blends in diesel engines and their effects on the engine performance and emission. Hopefully, the results of this study can provide some contribution to the development of next generation of biodiesel engines in the near future.

In this study, the computational fluid dynamics (CFD) model for a real engine is constructed to investigate various physical phenomena, flow fields, cylinder pressure fields, heat release rates, and NOx emission
inside a diesel engine combusting biodiesel blends. The flow field is obtained by solving the Navier-Stokes equations and various empirical models are used to model the behaviors of fuel injection, atomization and evaporation due to the extreme complexities in numerical calculation. To justify the validity of our numerical model, the results of the steady state cold flow numerical simulation were compared to the experimental data first. Then the model will be used to predict the combustion behaviors such as in-cylinder pressure, temperature, and heat release rate inside the diesel engine burning various biodiesel blends. These data will be checked against the in-cylinder pressure obtained from experiment for verification.

In the end, we will use this model to investigate the relationship between the NOx emission and the the temperature field inside the cylinder. Decent and promising correlation is obtained by comparing the numerical prediction to the NOx emission data obtained from experiment.

[1] 王冠中, 「渦輪增壓共軌柴油引擎之計算流體力學模型」, 國立台灣科技大學機械工程學系, 碩士論文(2013).

[2] 林延鴻, 「柴油引擎使用不同比例生質柴油之燃燒行為數值模擬分析」, 國立台灣科技大學機械工程學系, 碩士論文(2015).

[3] 曾柏憲, 「生質柴油引擎燃燒行為之數值模擬分析」, 國立台灣科技大學機械工程學系, 碩士論文(2014).

[4] W. Yuan, A. C. Hansen, and Q. Zhang, “Predicting the physical properties of biodiesel for combustion modeling,” American Society of Mechanical Engineers,vol. 46(6), pp. 1487–1493, 2003.

[5] M. T. Shervani-Tabar, M. Sheykhvazayefi, and M. Ghorbani, “Numerical study on the effect of the injection pressure on spray penetration length,” Applied Mathematical Modelling, vol. 37(14-15), pp. 7778–7788, 2013.

[6] P. J. Tennison, T. L. Georjon, P. V. Farrell, and R. D. Reitz, “An experimental and numerical study of sprays from a common rail injection system for use in an hsdi diesel engine,” SAE Technical Paper, 980810.

[7] N. R. Banapurmath, P. G. Tewari, and V. N. Gaitond, “Experimental investigations on performance and emission characteristics of honge oil biodiesel (home) operated compression ignition engine,” Renewable Energy, vol. 48(4), pp. 193–201, 2012.

[8] L. Labecki and L. C. Ganippa, “Effects of injection parameters and egr oncombustion and emission characteristics of rapeseed oil and its blends in diesel engines,” Fuel, vol. 98, pp. 15–28, 2012.

[9] D. Qi, M. Leick, Y. Liu, and C.-F. F. Lee, “Effect of egr and injection timing on combustion and emission characteristics of split injection strategy di-diesel engine fueled with biodiesel,” Fuel, vol. 90(5), pp. 1884–1891, 2011.

[10] Z. Jinghua, H. Wei, L. Xuejun, X. Fangxi, and J. Li, “Study about effects of egr and injection parameters on the combustion and emissions of high-pressure common-rail diesel engine,” International Conference on Industrial Mechatronics and Automation, vol. 1, pp. 290–294, 2010.

[11] M. R. Herfatmanesh, P. Lu, M. A. Attar, and H. Zhao, “Experimental investigation into the effects of two-stage injection on fuel injection quantity,combustion and emissions in a high-speed optical common rail diesel engine,” Fuel, vol. 109, pp. 137–147, 2013.

[12] T. L. Gianlua D’Errico and R. R. Frank Atzler, “Computational fluid dynamics simulation of diesel engines with sophisticated injection strategies for in-cylinder pollutant controls,” ENERGY and FUELS, vol. 26, pp. 4212–4223, 2012.

[13] H. K. N. Kar Mun Pang and S. Gan, “Simulation of temporal and spatial soot evoluation in an automotive diesel engine using the moss-brookes soot model,” Energy Conversion and Management, vol. 58, pp. 171–184, 2012.

[14] B. Jayashankara and V. Ganesan, “Effect of fuel injection timing and intake pressure on the performance of a di diesel engine - a parametric study using cfd,” Energy Conversion and Management, vol. 51, pp. 1835–1848, 2010.

[15] J. A. S. et al., Ansys fluent Guide. ANSYS Inc., 2013.

[16] T. M. Belal, E. S. M. Marzouk, and M. M. Osman, “Investigating diesel engine performance and emissions using cfd,” Energy and Power Engineering, vol. 5(2), pp. 171–180, 2013.

[17] B. Dhingra, S. Sharma, K. Vora, and B. Ashok, “Cfd modeling of advanced swirl technique at inlet-runner for diesel engine,” SAE Technical Paper, 2015-26-0095.

[18] R. K. D. A. K. Lichtarowicz and E. Markland, “Discharge coefficients for incompressible non-cavitating flow through long orifices,” Journal of Mechanical Engineering Science, 1965.

[19] W. H. Nurick, Orifice Cavitation and Its Effects on Spray Mixing.

[20] T. R. White, B. E. Milton, and M. Behnia, “Direct injection of natural gas/liquid diesel fuel sprays,” 15th Australasian Fluid Mechanics Conference, 2014.

[21] H. O. Hardenberg and F. E. Hase, “An empirical formula for computing the pressure rise delay of a fuel from its cetane number and from the relevant parameters of direct-injection diesel engines,” SAE Technical Paper, 790493.

[22] D. N. Assanis, Z. S. Filipi, S. B. Fiveland, and M. Syrimis, “A predictive ignition delay correlation under steady-state and transient operation of a direct injection diesel engine,” Journal of Engineering for Gas Turbines and Power, vol. 125, pp. 452–457, 2003.

[23] Y. V. Aghav, V. M. Thatte, M. N. Kumar, P. A. Lakshminarayanan, and M. K. G. Babu, “Predicting ignition delay and hc emission for di diesel engine encompassing egr and oxygenated fuels,” SAE Technical Paper, 2008-28-0050.

[24] J. B.Heywood, Internal Combustion Engine Fundamentals, 1988.