A comparison of injector flow and spray characteristics of biodiesel with petrodiesel
A comparison of injector flow and spray characteristics of biodiesel with petrodiesel
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DOI：
10.1016/j.fuel.2010.05.004
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发表时间：
2010-12
期刊：
影响因子：
7.4
通讯作者：
S. Som;D. Longman;A. Ramirez;S. Aggarwal
中科院分区：
文献类型：
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作者：
S. Som;D. Longman;A. Ramirez;S. Aggarwal
压燃式发动机的性能和排放特性很大程度上取决于喷嘴内的流动和喷雾特性。这些过程控制燃料空气混合，这反过来又是燃烧过程的关键。石油柴油和生物柴油的物理性质的差异，预计将显着改变内部喷嘴的流动和喷雾结构，因此，发动机的性能和排放特性。在这项研究中，这些燃料的内部喷嘴流动动力学的特点是使用基于混合物的空化模型在FLUENT v6.3。由于其较低的蒸气压，生物柴油被观察到比石油柴油更少的空化。生物柴油的粘度越高，流动效率越低，喷射速度越慢。对于生物柴油，喷嘴孔出口处的湍流水平也较低。使用最近开发的KH-ACT模型，它结合了空化和湍流的影响，除了气动破碎，内喷嘴流模拟耦合与喷雾模拟在一个“准动态”的方式。因此，除了这些燃料的物理性质的影响，内部喷嘴的流量差异对喷雾发展的影响可以被捕获。生物柴油的喷雾穿透率略高，而锥角较低，这是由于其雾化特性差。计算的石油柴油和生物柴油的液体长度与桑迪亚国家实验室的数据进行了比较。由于生物柴油的沸点和汽化热较高，其液体长度较高。虽然模拟很好地捕捉到了这一趋势，但液体长度被低估了，这是由于实验中使用的生物柴油性质的不确定性。进行参数研究，以确定一个单一的参数，可以用来解释所观察到的石油柴油和生物柴油的燃料喷射和喷雾行为的差异;燃料温度似乎是最好的参数调整。
Performance and emission characteristics of compression ignition engines depend strongly on inner nozzle flow and spray behavior. These processes control the fuel air mixing, which in turn is critical for the combustion process. The differences in the physical properties of petrodiesel and biodiesel are expected to significantly alter the inner nozzle flow and spray structure and, thus, the performance and emission characteristics of the engine. In this study, the inner nozzle flow dynamics of these fuels are characterized by using the mixture-based cavitation model in FLUENT v6.3. Because of its lower vapor pressure, biodiesel was observed to cavitate less than petrodiesel. Higher viscosity of biodiesel resulted in loss of flow efficiency and reduction in injection velocity. Turbulence levels at the nozzle orifice exit were also lower for biodiesel. Using the recently developed KH-ACT model, which incorporates the effects of cavitation and turbulence in addition to aerodynamic breakup, the inner nozzle flow simulations are coupled with the spray simulations in a “quasi-dynamic” fashion. Thus, the influence of inner nozzle flow differences on spray development of these fuels could be captured, in addition to the effects of their physical properties. Spray penetration was marginally higher for biodiesel, while cone angle was lower, which was attributed to its poor atomization characteristics. The computed liquid lengths of petrodiesel and biodiesel were compared with data from Sandia National Laboratories. Liquid lengths were higher for biodiesel due to its higher boiling temperature and heat of vaporization. Though the simulations captured this trend well, the liquid lengths were underpredicted, which was attributed to uncertainty about the properties of biodiesel used in the experiments. Parametric studies were performed to determine a single parameter that could be used to account for the observed differences in the fuel injection and spray behavior of petrodiesel and biodiesel; fuel temperature seems to be the best parameter to tune.