贫油直接喷射低排放燃烧技术研究

发布时间：2018-03-23 14:23

本文选题：航空发动机　切入点：低排放燃烧室　出处：《南京航空航天大学》2015年硕士论文

【摘要】：为了控制航空发动机排放对环境造成的影响,以研制高效低排放燃烧室为背景,开展贫油直接喷射(LDI)低排放燃烧技术的研究,进行了单点、四点及九点LDI燃烧室方案设计及加工,进行了单点和九点LDI燃烧室总压损失和有效面积测量。采用数值模拟的方法,研究了几种LDI燃烧室的速度分布、温度分布、组分浓度、污染物排放等燃烧特性。获得成果主要包括:(1)根据高效低排放燃烧室技术要求,完成了单点、四点和九点贫油直接喷射燃烧室的方案设计,包括60°和45°两种不同旋流角的轴向旋流器、文氏管、四点和九点阵列方式布局等,并进行了试验件加工,初步测量了单点和九点LDI燃烧室的总压损失和有效面积,获得了总压损失系数和有效面积随进口流量的变化规律。(2)介绍了燃烧室数值计算所需要的守恒方程,分析了LDI燃烧室数值计算所采用的Realizable k-ε湍流模型、EDC湍流燃烧模型、PDF模型、离散型模型及NOX模型等特点和适应性。进行LDI燃烧室各试验件模型进行简化,并进行网格划分和边界条件确定。(3)建立了旋流器出口角分别为60°及45°顺时针旋向的单点LDI燃烧室模型,分别设置常温常压及高温高压两种进口条件,以研究进口条件及出口角对单点LDI燃烧室燃烧特性及NO排放特性的影响。研究结果表明:高温高压进口条件下的单点LDI燃烧室内流场轴向速度较大,使得NO排放量较低;45°单点LDI燃烧室燃烧温度较高,高温区面积较大,轴向速度较小,使得其NO排放量比60°单点LDI燃烧室高。(4)建立了单元体中心距不同的三组四点LDI燃烧室模型,分别进行H2的燃烧模拟。研究结果表明:由于燃烧室的当量比相同,燃烧室内的燃烧温度基本相同,但随着中心间距的减小,相邻流场的相互作用逐渐加强,轴向速度有所增加,且最小中心间距的四点LDI燃烧室的NO排放量显著降低,这充分说明了小间距对控制多点LDI燃烧室NO排放量的优势。(5)建立了旋流器出口角分别为60°及45°的九点LDI燃烧室模型,且都有四种阵列形式,对四种阵列形式下的各出口角的九点LDI燃烧室燃烧特性进行数值模拟。研究结果表明:阵列分布的多点LDI燃烧室可以显著减小回流区长度及高温区面积,且更有利于贫油混合气的生成,从而有效降低NO的排放量;同向阵列分布结构的相邻流场的相交处的剪切应力方向相反,从而加强了油雾破碎,更有利于贫油燃烧,从而NO排放量较低;45°九点LDI燃烧室流场相互作用较弱,使得其并没有表现出多点结构在控制NO排放上的优势。研究结果为深入开展贫油直接喷射(LDI)低排放燃烧技术研究打下了坚实的基础,为LDI燃烧室的设计及工程应用提供理论依据和技术支持。
[Abstract]:In order to control the impact of aero-engine emissions on the environment, the low-emission combustion technology of lean oil direct injection (LDI) combustion was studied on the background of developing a high-efficiency and low-emission combustion chamber, and a single point was carried out. The design and processing of four-point and nine-point LDI combustor were carried out. The total pressure loss and effective area of single and nine-point LDI combustor were measured. The velocity distribution, temperature distribution and component concentration of several LDI combustors were studied by numerical simulation. Combustion characteristics such as pollutant emissions. The main results obtained include: 1) according to the technical requirements of high efficiency and low emission combustors, the scheme design of single point, four point and nine point lean oil direct injection combustor has been completed. Axial hydrocyclones, Venturi tubes, four-point and nine-point array configurations with different swirl angles of 60 掳and 45 掳were processed and the total pressure loss and effective area of single-point and nine-point LDI combustor were preliminarily measured. The variation law of total pressure loss coefficient and effective area with inlet flow is obtained. The conservation equation required for numerical calculation of LDI combustor is introduced. The Realizable k- 蔚 turbulence model used in numerical calculation of LDI combustor is analyzed. The characteristics and adaptability of discrete model and NOX model are analyzed. The model of LDI combustion chamber is simplified. A single-point LDI combustor model with outlet angles of 60 掳and 45 掳clockwise rotation was established by mesh division and boundary condition determination. The inlet conditions of atmospheric pressure and high temperature and high pressure were set up, respectively. The effects of inlet conditions and outlet angles on combustion characteristics and no emission characteristics of single point LDI combustor are studied. The results show that the axial velocity of flow field in single point LDI combustion chamber under high temperature and high pressure inlet conditions is larger. Three groups of four-point LDI combustor models with different central distance between unit body and center are established because no emission is lower than that of 60 掳single-point LDI combustion chamber with higher combustion temperature, larger area in high temperature and smaller axial velocity, so that no emission is higher than 60 掳single-point LDI combustor. The results show that the combustion temperature in the combustion chamber is basically the same because the equivalent ratio of the combustion chamber is the same, but with the decrease of the center spacing, the interaction between adjacent flow fields is gradually strengthened. The axial velocity increases and the no emission from the four-point LDI combustor with the minimum center spacing decreases significantly. This fully shows that the advantage of small spacing to control no emission from multi-point LDI combustor is to set up a nine-point LDI combustor model with outlet angles of 60 掳and 45 掳, respectively, and there are four kinds of arrays. The combustion characteristics of nine-point LDI combustor with four kinds of arrays are numerically simulated. The results show that the multi-point LDI combustor with array distribution can significantly reduce the length of the reflux zone and the area of the high temperature region. Moreover, it is more favorable to the formation of lean oil mixture, thus effectively reducing no emission, and the shear stress at the intersection of adjacent flow fields with the same array distribution structure is opposite, which enhances the oil mist fragmentation and is more favorable for lean oil combustion. As a result, the flow field interaction of LDI combustion chamber with lower no emission of 45 掳and 9 掳is weaker. The results lay a solid foundation for further research on low emission combustion technology of lean oil direct injection LDI. It provides theoretical basis and technical support for the design and engineering application of LDI combustion chamber.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：V231.2

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