基于三维数值模拟的离心式通风机叶轮设计方法研究

发布时间：2018-03-11 11:01

本文选题：离心式通风机　切入点：优化设计　出处：《浙江大学》2011年硕士论文　论文类型：学位论文

【摘要】：前向离心式通风机,如9-19、9-26系列,由于其具有较高的输出压力,因而广泛应用于物料输送、锻冶炉及高压强制通风。相比于后向风机,前向风机有效率较低、噪声较高、工作范围偏窄的缺点。本文主要针对前向离心式通风机且以9-19风机为设计实例,通过提出合理的气动设计方法将前向叶片重新设计成后向叶片,并采用数值模拟方法进行分析和优化,从而在保证满足流量、压力等条件下,提高风机的效率。本文的设计思想是基于离心风机叶轮流道内的流动特点,从叶轮流道内的速度分布出发,控制边界层的增长、吸力边边界层分离、分层效应及二次流,从而达到减弱尾流区、减小流动损失的目的。这使得本文的设计方法比传统方法更符合实际流动状况。气动设计的主要步骤是：通过控制叶轮内平均相对速度的分布,设计叶轮的几何形状,并采用一系列目标函数和设计准则,筛选气动结构；对合理的气动结构进行成型,通过三维数值模拟分析其整体性能和流动状况,并作进一步优化。本文采用三维时均Navier-Stokes方程,并结合RNG k-ε湍流模型,对离心风机内部流场进行了数值模拟。数值模拟的计算结果和实验数据十分吻合,并很好的预测了离心风机的全压和效率曲线。通过数值模拟,本文比较了不同设计模型和原始机型的性能和流动特征。相比于原始机型,最优设计模型的效率平均提升5%左右,风机流场内的分离流动、二次流、射流-尾流均有减弱。本文详细的分析了风机各部分的流动以及不同工况条件下叶轮流道内速度和压力的分布情况,并捕捉到了风机流场内的分离流动、二次流、射流-尾流等流动特征。叶轮损失是整个风机的损失的最主要来源,约占总损失的1/2,而蜗壳部分的损失则占据了剩余损失的绝大部分。叶轮子午平面初始段,前盘表面聚集了低速流体,从而引起了整个流道内流动的不稳定,随着流量的增加,这种不稳定性越来越强烈。同时,由于叶轮和蜗壳的相互作用,在蜗壳内形成了二次流和环流。在几乎所有的叶轮流道出口附近,都存在典型的射流—尾流结构。由于旋转和曲率的影响,叶轮流道内的二次流较为显著。最后,本文还分析了风机进风口和叶轮之间的间隙流动,该流动对风机的整体性能有着显著的影响。
[Abstract]:Because of its high output pressure, the forward centrifugal fan, such as 9-1999-26 series, is widely used in material transportation, forging furnace and high pressure forced ventilation. Compared with the backward fan, the forward fan has lower efficiency and higher noise. In this paper, aiming at the forward centrifugal fan and taking the 9-19 fan as the design example, the forward blade is redesigned into the backward blade by a reasonable aerodynamic design method. The numerical simulation method is used to analyze and optimize the fan so as to improve the efficiency of the fan under the condition of satisfying the flow rate and pressure. The design idea of this paper is based on the flow characteristics in the impeller passage of centrifugal fan, starting from the velocity distribution in the impeller passage, controlling the growth of the boundary layer, separating the boundary layer of suction edge, delaminating effect and secondary flow, so as to weaken the wake zone. The purpose of reducing the flow loss is to make the design method in this paper more suitable for the actual flow condition than the traditional method. The main step of aerodynamic design is to design the geometric shape of the impeller by controlling the distribution of the average relative velocity in the impeller. A series of objective functions and design criteria are adopted to screen the pneumatic structure, and the reasonable aerodynamic structure is formed, and its overall performance and flow state are analyzed by three-dimensional numerical simulation, and further optimized. In this paper, the three-dimensional time-averaged Navier-Stokes equation and the RNG k- 蔚 turbulence model are used to simulate the flow field in the centrifugal fan. The results of the numerical simulation are in good agreement with the experimental data. Through numerical simulation, the performance and flow characteristics of different design models and original models are compared. Compared with the original model, the efficiency of the optimal design model is increased by about 5% on average. The separation flow, secondary flow and jet-wake flow in the fan flow field are all weakened. This paper analyzes in detail the flow in various parts of the fan and the distribution of velocity and pressure in the impeller passage under different working conditions. The separation flow, secondary flow, jet-wake flow and other flow characteristics in the fan flow field are captured. The impeller loss is the main source of the loss of the whole fan. About 1 / 2 of the total loss, while the volute part of the loss accounts for the majority of the remaining loss. In the initial section of the impeller meridian plane, a low velocity fluid accumulates on the front surface of the impeller, thus causing instability of the flow in the entire channel, and with the increase of the flow rate, At the same time, because of the interaction between the impeller and the volute, secondary flow and circulation are formed in the volute. Because of the influence of rotation and curvature, the secondary flow in the impeller passage is obvious. Finally, the gap flow between the fan inlet and the impeller is analyzed. The flow has a significant impact on the overall performance of the fan.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH432

【参考文献】