【作者】 严春吉；

【导师】 殷佩海；

【作者基本信息】 大连海事大学 ， 轮机工程， 2005， 博士

【摘要】 燃油的分裂与雾化过程实际上是液体射流的一种失稳现象,在工程上常常利用射流的这种失稳过程来实现燃油的雾化,以增加燃油的表面积提高燃烧效率。因此对射流分裂与雾化机理的研究不仅具有重要的理论意义,而且还具有深远的工程应用背景。本文对粘性液体射流分裂与雾化过程的机理进行了理论和数值研究,并将结果应用于内燃机缸内工作过程的模拟中。具体完成了以下几方面的工作。 一、概括总结了前人关于射流稳定性及其分裂雾化机理的研究成果,同时还对内燃机工作过程中,燃油在缸内的雾化模型进行了介绍。 二、将圆柱形粘性液体射流模型进一步推广,即考虑到气体的粘性在射流分裂与雾化过程中的作用,使射流分裂雾化模型更加完善;采用线性稳定性分析的方法对射流模型进行了求解,得到了具有普遍三维扰动形式下的射流自由表面扰动发展的色散关系;本文手算推导的色散关系得到了代数及符号软件MATHEMATICA的验证。 三、对上述的色散关系作了比较详尽的数值分析并针对若干实际工况进行了大量数值计算;通过数值模拟本文首次确定了临界气体韦伯数We_2c=1,可以作为区分粘性液体射流分裂与雾化模态的判据。当We₂<1时,射流处于分裂模态,而当We₂>1时,射流过程为雾化模态。将理论分析及数值计算结果与射流分裂雾化特性相结合得到了一套计算射流的未受扰液核长度、喷雾的平均滴径的方法。 四、将空心圆柱形粘性液体射流模型也作了推广,即建立了旋转气流中的空心圆柱射流分裂与雾化三维模型;通过手算得到了空心圆柱形粘性液体射流的具有普遍三维扰动形式下的自由表面扰动发展的色散关系,该关系也得到了代数及符号软件MATHEMATICA的验证。 五、对空心圆柱形粘性液体射流自由表面扰动发展的色散关系进行比较全面的数值分析,比较了各参数在低速射流与高速射流中的作用及异同。 六、将圆柱形粘性液体射流分裂雾化机理研究的结果应用于一小型高速4缸柴油机缸内工作过程的模拟中,同时还对该型柴油机的工作特性进行了实验研究。更多还原

【Abstract】 In fact, the process of fuel breakup and atomization is a kind of instability phenomenon of the liquid jet. In order to increasing the oil surface area and promoting efficient combustion, the instability process of the jet is always used to make the fuel atomization in engineering. So studying on the mechanisms of breakup and atomization of a jet is not only important on theory but it owns the engineering background. This thesis conducts a theoretic and numerical investigation on the mechanisms of the breakup and atomization of viscous liquid jets, and the results that obtained from this studying are applied in the process simulation in cylinder of the internal combustion engine. The following terms have been finished.1. The detailed review of the previous works on the stability analysis of liquid jets and it’s breakup and atomization are given, in addition, the fuel atomization models in cylinder of the ICE are introduced in this dissertation.2. The model of viscous liquid round jets is extended, namely, it includes the action of the gas viscosity in the breakup and atomization process, and in such way that makes the model of the jet more consummate. Based on the linear analysis method, the dispersion relation is obtained which delineates the evolution of a general 3-dimensional disturbance on the free surface of a viscous liquid jet. The manually deduced dispersion relation has been verified by means of the computer algebra software MATHEMATICA.3. For above obtained dispersion relation, comprehensive numerical analysis has been carried out, and so as a certain number of operating mode. By numerical simulation, a critical Weber number(We_2c=1) is first found in this dissertation, which can be as a criterion to distinguish the breakup and atomization of viscous liquid jets. When Weber number We₂<1, the process of viscous liquid jets is in the case of breakup, while We₂>1, it shows the behavior of atomization. By combining theoretical analysis and numerical results, formulas are obtained to compute the intact breakup length and the mean radius of the jet.4. The model of viscous liquid annular jets is also promoted, namely, 3-D model of an annular liquid jet surrounded by swirling airstreams has been established. Themanually deduced dispersion relation that delineates the evolution of a general 3-dimensional disturbance on the free surface of a viscous liquid jet has also been verified by means of the computer algebra software MATHEMATICA.5. For the dispersion relation of the viscous liquid annular jet, comprehensive numerical analysis has been earned out, and actions of many parameters on the low-speed and high-speed jet have been compared in this thesis.6. The results, which are obtained from the studying on the mechanism of viscous liquid round jets, are applied in the simulating for a high-speed 4- cylinder diesel engine, and the properties of this diesel engine are experimented in the dissertation.更多还原