电子膨胀阀节流噪声数值模拟
发布时间：2018-08-02 17:58
【摘要】：变频空调利用变频压缩技术有效节省了空调用电，电子膨胀阀是其中重要组成部件之一。它不仅用于调节制冷剂的流量，而且能够影响空调的能效比。在空调性能逐渐提升的同时，电子膨胀阀的噪声问题也受到越来越多的重视。本文在变频空调额定制冷工况下，对电子膨胀阀的流体噪声进行了测量；同时建立电子膨胀阀三维模型，以HFC-410A作为工质，对其内部的两相流动及噪声特性进行了数值模拟。计算结果对电子膨胀阀的流道模型设计及改进具有重要的参考价值。 本文对电子膨胀阀流场的数值模拟采用Reliable k ε湍流模型，两相流模型选用Mixture模型，采用蒸发和沸腾模型来描述并计算在闪蒸过程中阀口及其下游气液两相之间的质量转换；采用宽频噪声模型对流场噪声进行了计算；控制方程使用有限差分法进行离散；使用Coupled算法求解压力-速度耦合流场。 首先，建立电子膨胀阀不同开度下的三维流道模型，对其进行网格划分并进行网格无关性分析；通过对电子膨胀阀的流场进行时均化处理，得到不同开度下电子膨胀阀的流量，并与实验值进行对比，发现模拟结果与实验所测数值变化趋势相同且在误差允许范围内吻合较好。另外，对比不同开度下流场的压力云图和速度云图发现其分布均极为相似，选取0.625mm开度（即100脉冲）的流场单独进行分析。发现在阀口入口拐角及阀针下端面处存在压力极小值，从流线图中发现阀针下端面存在两处漩涡，它们相互扰动，形成了该区域无规律的压力分布，并在下游不远处引起一处高压区。另外通过提取对称平面上压力、速度以及湍流动能主流区域线上的数值，分析得到电子膨胀阀内噪声产生的位置在阀口靠近壁面处及其下游z=-0.138m（即4倍管道直径）处。 接着，对电子膨胀阀噪声问题进行了成因分析，电子膨胀阀的主要噪声来源于四极子噪声，即阀内流体无规则运动产生了较大的湍流动能，主要分布在阀口壁面、阀针下端面以及下游管道的特定区域。 然后，对电子膨胀阀进行了噪声实验研究，，在电子膨胀阀同一水平面30cm处布置测点，通过焓差实验室制造额定工况下室内/外环境室温度，调节空调器的风速，得到电子膨胀阀开度与声压级之间的关系曲线，发现不同风速条件下声压级随开度的变化趋势一致，表明流道形态对噪声有重要的影响。 最后，根据前文分析的结果，改变入口压力、上/下游扩口角度以及阀口长度的大小，建立不同流道结构模型并进行数值模拟。改变压力项模拟结果显示，随着压差的增大，电子膨胀阀质量流量及湍流动能逐渐增大，代表声功率级逐渐增大。改变扩口角度的数值模拟结果显示，上游扩口角度对噪声的影响很大，且在所选角度研究范围内，入口角度为60°-70°范围时声功率级最小；下游扩口角度的存在可以有效降低管道内的声功率，而扩口角度的大小对噪声的影响不大。改变阀口长度的数值模拟结果显示，噪声强度随着阀口长度的改变呈周期性改变。
[Abstract]:Frequency conversion air conditioning is one of the most important components of air conditioning using frequency conversion compression technology. The electronic expansion valve is one of the important components. It is not only used to regulate the flow of refrigerant, but also affects the energy efficiency ratio of air conditioning. While the performance of air conditioning is gradually improved, the noise of the electronic expansion valve has been paid more and more attention. The fluid noise of the electronic expansion valve is measured under the rated refrigerating condition of the variable frequency air conditioning. At the same time, the three-dimensional model of the electronic expansion valve is set up, and the two phase flow and noise characteristics are simulated with HFC-410A as the working medium. The calculation results have important reference price for the design and improvement of the channel model of the electronic expansion valve. Value.
In this paper, the Reliable K E turbulence model is used for the numerical simulation of the flow field of the electronic expansion valve. The two-phase flow model is selected by the Mixture model. The evaporation and boiling model is used to describe and calculate the mass conversion between the valve mouth and the gas-liquid two phase in the downstream of the flash evaporation process. The convection field noise of the wide-band noise model is calculated and the control equation is used. The finite difference method is used to discretize, and the Coupled algorithm is used to solve the pressure velocity coupling flow field.
First, the three-dimensional flow model of the electronic expansion valve under different open degrees is set up, and the grid is divided and the grid independent analysis is carried out. Through the time homogenization of the flow field of the electronic expansion valve, the flow of the electronic expansion valve under different open degrees is obtained, and the ratio of the experimental value is compared with the experimental values, and the changes of the simulated results and the experimental values are found. In addition, the distribution of pressure and velocity in the flow field under different open degrees is very similar, and the flow field of the 0.625mm opening (100 pulse) is analyzed separately. It is found that there is a pressure minimum at the inlet corner of the valve entrance and the lower end of the valve needle, and the valve is found in the flow chart. There are two whirlpools on the bottom end of the needle, which disturb each other and form a irregular pressure distribution in the region and cause a high pressure area not far downstream. In addition, by extracting the pressure, velocity and the main stream of the turbulent kinetic energy on the symmetrical plane, the position of the noise in the valve opening near the wall of the valve is analyzed. The surface and its downstream z=-0.138m (i.e. 4 times the diameter of the pipe).
Then, the cause of the noise of the electronic expansion valve is analyzed. The main noise of the electronic expansion valve is derived from the quadrupole noise, that is, the irregular motion of the fluid in the valve produces a larger turbulent kinetic energy, which is mainly distributed in the wall of the valve mouth, the end face of the valve needle and the specific area of the downstream pipeline.
Then, the experimental study of the electronic expansion valve is carried out. The measurement points are arranged at the same horizontal plane 30cm of the electronic expansion valve. The temperature of the indoor / outer ambient chamber under the rated condition is manufactured by the enthalpy difference laboratory, the wind speed of the air conditioner is adjusted, the relation curve between the opening of the electronic expansion valve and the sound pressure level is obtained, and the sound pressure level under the different wind speed conditions is found to follow. The change trend of opening degree is the same, which indicates that the flow pattern has important influence on noise.
Finally, according to the results of the previous analysis, changing the inlet pressure, the upstream / downstream expansion angle and the size of the valve mouth length, different flow channel structure models are set up and numerical simulation is set up. The result of the pressure difference simulation shows that the mass flow and turbulent kinetic energy of the electronic expansion valve increase gradually with the increase of pressure difference, and the representative sound power level is gradually increased. The numerical simulation results show that the upstream expansion angle has a great influence on the noise, and the sound power level is minimum in the range of 60 degree -70 degrees in the range of selected angles, and the presence of the downstream expansion angle can effectively reduce the sound power in the pipeline, and the size of the expansion angle has little effect on the noise. The numerical simulation results of valve port length show that the noise intensity changes periodically with the change of valve port length.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB657
本文编号：2160225
[Abstract]:Frequency conversion air conditioning is one of the most important components of air conditioning using frequency conversion compression technology. The electronic expansion valve is one of the important components. It is not only used to regulate the flow of refrigerant, but also affects the energy efficiency ratio of air conditioning. While the performance of air conditioning is gradually improved, the noise of the electronic expansion valve has been paid more and more attention. The fluid noise of the electronic expansion valve is measured under the rated refrigerating condition of the variable frequency air conditioning. At the same time, the three-dimensional model of the electronic expansion valve is set up, and the two phase flow and noise characteristics are simulated with HFC-410A as the working medium. The calculation results have important reference price for the design and improvement of the channel model of the electronic expansion valve. Value.
In this paper, the Reliable K E turbulence model is used for the numerical simulation of the flow field of the electronic expansion valve. The two-phase flow model is selected by the Mixture model. The evaporation and boiling model is used to describe and calculate the mass conversion between the valve mouth and the gas-liquid two phase in the downstream of the flash evaporation process. The convection field noise of the wide-band noise model is calculated and the control equation is used. The finite difference method is used to discretize, and the Coupled algorithm is used to solve the pressure velocity coupling flow field.
First, the three-dimensional flow model of the electronic expansion valve under different open degrees is set up, and the grid is divided and the grid independent analysis is carried out. Through the time homogenization of the flow field of the electronic expansion valve, the flow of the electronic expansion valve under different open degrees is obtained, and the ratio of the experimental value is compared with the experimental values, and the changes of the simulated results and the experimental values are found. In addition, the distribution of pressure and velocity in the flow field under different open degrees is very similar, and the flow field of the 0.625mm opening (100 pulse) is analyzed separately. It is found that there is a pressure minimum at the inlet corner of the valve entrance and the lower end of the valve needle, and the valve is found in the flow chart. There are two whirlpools on the bottom end of the needle, which disturb each other and form a irregular pressure distribution in the region and cause a high pressure area not far downstream. In addition, by extracting the pressure, velocity and the main stream of the turbulent kinetic energy on the symmetrical plane, the position of the noise in the valve opening near the wall of the valve is analyzed. The surface and its downstream z=-0.138m (i.e. 4 times the diameter of the pipe).
Then, the cause of the noise of the electronic expansion valve is analyzed. The main noise of the electronic expansion valve is derived from the quadrupole noise, that is, the irregular motion of the fluid in the valve produces a larger turbulent kinetic energy, which is mainly distributed in the wall of the valve mouth, the end face of the valve needle and the specific area of the downstream pipeline.
Then, the experimental study of the electronic expansion valve is carried out. The measurement points are arranged at the same horizontal plane 30cm of the electronic expansion valve. The temperature of the indoor / outer ambient chamber under the rated condition is manufactured by the enthalpy difference laboratory, the wind speed of the air conditioner is adjusted, the relation curve between the opening of the electronic expansion valve and the sound pressure level is obtained, and the sound pressure level under the different wind speed conditions is found to follow. The change trend of opening degree is the same, which indicates that the flow pattern has important influence on noise.
Finally, according to the results of the previous analysis, changing the inlet pressure, the upstream / downstream expansion angle and the size of the valve mouth length, different flow channel structure models are set up and numerical simulation is set up. The result of the pressure difference simulation shows that the mass flow and turbulent kinetic energy of the electronic expansion valve increase gradually with the increase of pressure difference, and the representative sound power level is gradually increased. The numerical simulation results show that the upstream expansion angle has a great influence on the noise, and the sound power level is minimum in the range of 60 degree -70 degrees in the range of selected angles, and the presence of the downstream expansion angle can effectively reduce the sound power in the pipeline, and the size of the expansion angle has little effect on the noise. The numerical simulation results of valve port length show that the noise intensity changes periodically with the change of valve port length.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB657
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