發(fā)布時(shí)間：2018-08-02 17:58

【摘要】：變頻空調(diào)利用變頻壓縮技術(shù)有效節(jié)省了空調(diào)用電，電子膨脹閥是其中重要組成部件之一。它不僅用于調(diào)節(jié)制冷劑的流量，而且能夠影響空調(diào)的能效比。在空調(diào)性能逐漸提升的同時(shí)，電子膨脹閥的噪聲問題也受到越來越多的重視。本文在變頻空調(diào)額定制冷工況下，對(duì)電子膨脹閥的流體噪聲進(jìn)行了測量；同時(shí)建立電子膨脹閥三維模型，以HFC-410A作為工質(zhì)，對(duì)其內(nèi)部的兩相流動(dòng)及噪聲特性進(jìn)行了數(shù)值模擬。計(jì)算結(jié)果對(duì)電子膨脹閥的流道模型設(shè)計(jì)及改進(jìn)具有重要的參考價(jià)值。 本文對(duì)電子膨脹閥流場的數(shù)值模擬采用Reliable k ε湍流模型，兩相流模型選用Mixture模型，采用蒸發(fā)和沸騰模型來描述并計(jì)算在閃蒸過程中閥口及其下游氣液兩相之間的質(zhì)量轉(zhuǎn)換；采用寬頻噪聲模型對(duì)流場噪聲進(jìn)行了計(jì)算；控制方程使用有限差分法進(jìn)行離散；使用Coupled算法求解壓力-速度耦合流場。 首先，建立電子膨脹閥不同開度下的三維流道模型，對(duì)其進(jìn)行網(wǎng)格劃分并進(jìn)行網(wǎng)格無關(guān)性分析；通過對(duì)電子膨脹閥的流場進(jìn)行時(shí)均化處理，得到不同開度下電子膨脹閥的流量，并與實(shí)驗(yàn)值進(jìn)行對(duì)比，發(fā)現(xiàn)模擬結(jié)果與實(shí)驗(yàn)所測數(shù)值變化趨勢相同且在誤差允許范圍內(nèi)吻合較好。另外，對(duì)比不同開度下流場的壓力云圖和速度云圖發(fā)現(xiàn)其分布均極為相似，選取0.625mm開度（即100脈沖）的流場單獨(dú)進(jìn)行分析。發(fā)現(xiàn)在閥口入口拐角及閥針下端面處存在壓力極小值，從流線圖中發(fā)現(xiàn)閥針下端面存在兩處漩渦，它們相互擾動(dòng)，形成了該區(qū)域無規(guī)律的壓力分布，并在下游不遠(yuǎn)處引起一處高壓區(qū)。另外通過提取對(duì)稱平面上壓力、速度以及湍流動(dòng)能主流區(qū)域線上的數(shù)值，分析得到電子膨脹閥內(nèi)噪聲產(chǎn)生的位置在閥口靠近壁面處及其下游z=-0.138m（即4倍管道直徑）處。 接著，對(duì)電子膨脹閥噪聲問題進(jìn)行了成因分析，電子膨脹閥的主要噪聲來源于四極子噪聲，即閥內(nèi)流體無規(guī)則運(yùn)動(dòng)產(chǎn)生了較大的湍流動(dòng)能，主要分布在閥口壁面、閥針下端面以及下游管道的特定區(qū)域。 然后，對(duì)電子膨脹閥進(jìn)行了噪聲實(shí)驗(yàn)研究，，在電子膨脹閥同一水平面30cm處布置測點(diǎn)，通過焓差實(shí)驗(yàn)室制造額定工況下室內(nèi)/外環(huán)境室溫度，調(diào)節(jié)空調(diào)器的風(fēng)速，得到電子膨脹閥開度與聲壓級(jí)之間的關(guān)系曲線，發(fā)現(xiàn)不同風(fēng)速條件下聲壓級(jí)隨開度的變化趨勢一致，表明流道形態(tài)對(duì)噪聲有重要的影響。 最后，根據(jù)前文分析的結(jié)果，改變?nèi)肟趬毫Α⑸?下游擴(kuò)口角度以及閥口長度的大小，建立不同流道結(jié)構(gòu)模型并進(jìn)行數(shù)值模擬。改變壓力項(xiàng)模擬結(jié)果顯示，隨著壓差的增大，電子膨脹閥質(zhì)量流量及湍流動(dòng)能逐漸增大，代表聲功率級(jí)逐漸增大。改變擴(kuò)口角度的數(shù)值模擬結(jié)果顯示，上游擴(kuò)口角度對(duì)噪聲的影響很大，且在所選角度研究范圍內(nèi)，入口角度為60°-70°范圍時(shí)聲功率級(jí)最��；下游擴(kuò)口角度的存在可以有效降低管道內(nèi)的聲功率，而擴(kuò)口角度的大小對(duì)噪聲的影響不大。改變閥口長度的數(shù)值模擬結(jié)果顯示，噪聲強(qiáng)度隨著閥口長度的改變呈周期性改變。
[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.
【學(xué)位授予單位】：浙江理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB657

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