基于控制速度分布的离心叶轮优化设计系统的研究

发布时间：2018-03-21 08:20

本文选题：离心叶轮　切入点：流动效应　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：离心风机作为一种输送气体的通用机械设备,在水泥、电力、化工、钢铁等工业领域广泛应用,并且这些领域使用的离心风机存在数量大、单机功率高的特点,所以能耗巨大。因此建立针对于大型工业用离心风机叶轮优化设计系统具有重要经济效益。本文建立了包含叶轮总体参数和结构型线优化的离心风机叶轮优化设计系统,实现了离心叶轮的整体优化设计。首先,本文研究了离心叶轮流道内造成流动损失的流动效应(边界层增长与分离、二次流、分层效应等)的形成机理以及基本特征,分析了这些复杂流动效应与流动参数以及流道内速度分布间的相互关系,提出了进口加速系数、当量扩张角、载荷系数、进口减速比、最大减速比等控制参数。其次通过控制参数作为桥梁,建立了叶轮结构总体参数与内部流动特征间的关系,确立了既能控制流动损失又能保证设计要求的优化准则和目标函数,实现了总体参数的优化设计。通过理论分析得到了实现子午面二次流效应最小化的设计准则,通过给定合理的子午速度沿流线的分布,实现了前盘型线的优化设计。以速度分布作为桥梁,建立了叶片型线与速度分布控制参数间的关系,总结提炼出了与叶轮内部流动特征直接相关的最大载荷系数及其位置、进口减速比、最大减速比、吸力边相对速度进口斜率等速度分布控制参数。并在此基础上,通过研究分析建立了合理可靠的速度分布数学模型,并确定了流道内的速度分布,获得了叶片型线。其次,采用了考虑旋转与曲率的二维湍流边界层动量积分方程,实现了边界层厚度的准确计算。据此建立了基于控制速度分布优化设计系统,并编写了 C语言程序软件。最后,运用所编写的优化设计系统软件对两个不同型号的高效离心风机进行优化,运用数值模拟的方法对风机优化前后性能和流场进行对比分析,结果表明优化设计后的离心风机在设计流量下,1#和2#风机优化后全压均高于原型风机,效率分别提高了 5.12%和4.05%,并且全工况效率均得到了提升,说明本文所建立的设计系统是可行的。
[Abstract]:Centrifugal fan is widely used in cement, electric power, chemical industry, iron and steel industry as a general mechanical equipment for conveying gas, and the centrifugal fan used in these fields has the characteristics of large quantity and high power of single machine. Therefore, it has important economic benefits to set up an optimal design system for centrifugal fan impellers for large industrial use. In this paper, an optimal design system for centrifugal fan impellers is established, which includes the optimization of the overall parameters and the structural profile of the impeller. The overall optimum design of centrifugal impeller is realized. Firstly, the formation mechanism and basic characteristics of flow loss in centrifugal impeller passage (boundary layer growth and separation, secondary flow, stratification effect, etc.) are studied. The relationship between these complex flow effects and the flow parameters and velocity distribution in the channel is analyzed. The inlet acceleration coefficient, equivalent expansion angle, load coefficient and inlet deceleration ratio are proposed. Secondly, the relationship between the overall parameters of impeller structure and internal flow characteristics is established by using the control parameters as a bridge, and the optimization criteria and objective functions which can not only control the flow loss but also guarantee the design requirements are established. Through theoretical analysis, the design criteria for minimizing the secondary flow effect on the meridian plane are obtained, and the distribution of the meridian velocity along the streamline is given. The optimal design of the front disc profile is realized. The relationship between the blade profile and the control parameters of the velocity distribution is established by using the velocity distribution as a bridge, and the maximum load coefficient and its position directly related to the internal flow characteristics of the impeller are summarized and refined. The velocity distribution control parameters such as inlet deceleration ratio, maximum deceleration ratio and relative velocity slope of suction edge are obtained. On the basis of this, a reasonable and reliable mathematical model of velocity distribution is established through research and analysis, and the velocity distribution in the channel is determined. The blade profile is obtained. Secondly, the momentum integral equation of two-dimensional turbulent boundary layer considering rotation and curvature is adopted to realize the accurate calculation of the boundary layer thickness. Based on this, the optimal design system based on the control velocity distribution is established. Finally, two different types of high efficiency centrifugal fan are optimized by using the software of optimization design system, and the performance and flow field of the fan before and after optimization are compared and analyzed by numerical simulation method. The results show that the total pressure of the centrifugal fan after optimization is higher than that of the prototype fan at the design flow rate, and the efficiency is increased by 5.12% and 4.05 respectively, and the efficiency of the whole working condition is improved. It shows that the design system established in this paper is feasible.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH432

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