空调室内机内部流场特性及气动声学模型研究

发布时间：2019-05-16 09:30

【摘要】：空调室内机主要包括横流风机和换热器,其气动性能和气动声学问题被广泛关注。横流风机由于其独一无二的几何结构,其内部存在稳定的偏心涡结构,降低了横流风机系统的效率,因此研究横流风机的内部流动机理,特别是偏心涡的起源及发展规律具有重要的科学意义。气流经过空调室内机时随机产生的尖啸噪声对人体的舒适性有直接影响,因此有必要针对噪声产生的特性及发生机理展开详细研究,进而为空调室内机的设计提供可靠的理论基础。本文以横流风机为研究对象,通过实验和数值模拟手段详细研究了横流风机内部偏心涡启动、发展的规律,提出了控制偏心涡系统能量损失的方法,即在靠近蜗舌附近位置加装可调节角度的进口导叶,从而有效地减小了偏心涡的区域,增大了通流区域,提高了横流风机的气动性能。同时,本文以换热器作为研究对象,通过气动声学实验详细测量了气流经过换热器时产生随机噪声的环境,并通过热线实验和数值模拟手段分析了噪声产生的机理,建立了适用于空调室内机换热器噪声的声学模型。本文首先采用流动可视化实验方法对横流风机启动和稳定工况时偏心涡的产生及发展进行测量,精确捕捉到了偏心涡产生及稳定发展的流动图像。同时,使用商业软件FLUENT对稳定发展阶段的横流风机内部流动细节进行非稳态数值模拟,并与流动可视化实验结果相结合,从质量和能量两方面分析了横流风机偏心涡稳定存在的原因,并采用正交分解法和涡动力学原理分析了气流二次回流进入横流风机时叶片流动分离产生的脱落涡对偏心涡的影响,较为完整地提出了偏心涡产生及发展的机理。在明确了偏心涡产生及发展机理的基础上,提出并设计了在蜗舌附近加装进口可调导叶的改进措施。通过数值模拟手段对进口可调导叶的安装角度进行分析,结合总压、相对总压、扭矩系数等参数确定了能够有效提高横流风机性能的进口导叶角度,从而能够有效地减小二次回流进入叶片时的流动分离,减小偏心涡的区域,增大通流区域的区域,提高横流风机的气动性能。然后通过气动性能实验对数值模拟结果进行验证。结果表明,在流量不变的条件下,其功耗较不加进口导叶的原型机而言降低约3%。本文还针对气流经过换热器时会随机产生的尖啸噪声展开研究。首先通过气动声学实验研究了噪声发生的特性,通过气流大小、方向、换热器表面层数及换热器空腔数目等参数确定了噪声的特性,通过流速与频率之间的关系确定这种噪声是一种气动声学噪声,然后通过热线测速仪和数值模拟手段详细研究了随机噪声产生的机理,在此基础上,提出了适用于换热器噪声的Hill-hill noise声学模型,通过大量的实验数据建立了Hill-hill noise噪声的空腔剪切层自激振荡频率预测公式,并明确了噪声的特性及产生机理。
[Abstract]:The indoor air conditioning unit mainly includes crossflow fan and heat exchanger, and its pneumatic performance and pneumatic acoustics are widely concerned. Because of its unique geometric structure, there is a stable eccentric vortex structure in the crossflow fan, which reduces the efficiency of the crossflow fan system. Therefore, the internal flow mechanism of the crossflow fan is studied. In particular, the origin and development of eccentric vortexes are of great scientific significance. The random screeching noise produced by air flow through the indoor unit of air conditioning has a direct impact on the comfort of human body, so it is necessary to study the characteristics and mechanism of noise in detail. Furthermore, it provides a reliable theoretical basis for the design of indoor air conditioning unit. In this paper, taking crossflow fan as the research object, the law of starting and developing eccentric vortex in crossflow fan is studied in detail by means of experiment and numerical simulation, and the method of controlling the energy loss of eccentric vortex system is put forward. That is to say, the inlet guide vane with adjustable angle is installed near the worm tongue, so that the eccentric vortex area is effectively reduced, the flow area is increased, and the pneumatic performance of the crossflow fan is improved. At the same time, taking the heat exchanger as the research object, the environment of random noise produced by air flow passing through the heat exchanger is measured in detail by Aeroacoustics experiment, and the mechanism of noise generation is analyzed by hot wire experiment and numerical simulation. An acoustic model suitable for the noise of heat exchanger in air conditioning room is established. In this paper, the flow visualization experiment method is used to measure the generation and development of eccentric vortex in the starting and stable working conditions of crossflow fan, and the flow image of eccentric vortex generation and stable development is accurately captured. At the same time, the commercial software FLUENT is used to simulate the flow details of the crossflow fan in the stable development stage, which is combined with the experimental results of flow visualization. The causes of eccentric vortex stability of crossflow fan are analyzed from two aspects of mass and energy. The influence of shedding vortex produced by blade flow separation on eccentric vortex is analyzed by orthogonal decomposition method and vortex dynamics principle, and the mechanism of eccentric vortex generation and development is put forward completely. On the basis of defining the generation and development mechanism of eccentric vortex, the improvement measures of installing inlet adjustable guide vane near worm tongue are put forward and designed. The installation angle of the inlet adjustable guide vane is analyzed by numerical simulation, and the angle of the inlet guide vane which can effectively improve the performance of the crossflow fan is determined by combining the total pressure, relative total pressure, torque coefficient and other parameters. Thus, the flow separation when the secondary reflux enters the blade can be effectively reduced, the area of eccentric vortex can be reduced, the area of the flow region can be increased, and the pneumatic performance of the crossflow fan can be improved. Then the numerical simulation results are verified by the pneumatic performance experiment. The results show that the power consumption of the prototype without inlet guide vane is about 3% lower than that of the prototype without imported guide vane under the condition of constant flow rate. In this paper, the screeching noise which will be randomly generated when the air flow passes through the heat exchanger is also studied. Firstly, the characteristics of noise are studied by Aeroacoustics experiment, and the noise characteristics are determined by the parameters such as the size of air flow, the direction, the number of layers on the surface of heat exchanger and the number of cavities of heat exchanger. It is determined that the noise is a kind of pneumatic acoustic noise by the relationship between velocity and frequency, and then the mechanism of random noise is studied in detail by hot wire velocimeter and numerical simulation. A Hill-hill noise acoustic model for heat exchanger noise is proposed. The prediction formula of self-excited oscillation frequency of cavity shear layer for Hill-hill noise is established through a large number of experimental data, and the characteristics and generation mechanism of noise are clarified.
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB657.2

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