自由湍流射流理论研究方法

Progress in Theoretical Study of Free Turbulent Jets

气固两相双平行矩形自由射流混合特性的调查是水平浓淡煤粉燃烧技术研发过程中一项基础性工作,考察自由湍流射流的实验和理论研究进展有助于确定射流混合特性研究方法。自由湍流射流理论研究综述表明:单相自由湍流射流的理论研究可采用时间平均法和直接法。时间平均法能不同程度地满足工程需要;直接法中的有限差分法和离散涡方法可以预测大尺度涡的控制作用,包括谱方法的直接法尚难以模拟耗能涡影响。气固两相湍流射流的理论研究可采用Euler方法和Lagrangian方法。关于Euler方法中双流体模型的数学描述方法,尚存在分歧;在数值模拟伪扩散、考察颗粒变化历程等方面,Euler方法和Lagrangian方法互为优缺点;Lagrangian方法更适于预测拟序结构对大颗粒的快速弥散机制,发展于中国的Euler-Lagrangian方法值得关注。

Mixing characteristic investigation on gas - solid two - phase dual parallel rectangular jets is one part basic works of horizontal bias pulverized coal combustion technological research and development, and reviewing free jet experimental and/or theoretical studies is helpful to determine the technological strategy of jets mixing characteristic investigation. Findings of reviewing free jet theoretical studies showed that time - averaged methods and time - dependent methods can be adopted to predict the turbulent structure of gas free jets, various mathematical models of the time - averaged methods are available for engineering design, finite differential technology and discrete vortex method in the time - dependent theory is able to reveal the orderly structure of gas free jets; Euler simulation and Lagrangian modeling behave complementary advantages and disadvantages for gas - solid two - phase free jets. Two - fluid model in the Euler methods should be adopted carefully in engineering applications because of false diffusion in modeling and difficulty of determining pressure distribution between gas phase and solid phase. Developed Euler- Lagrangian method in China should be closely concernd.