Weak current College】 【how to effectively control the air conditioning compressor noise?.

<br> <br> I. preface <br> Split-type air conditioner outdoor side of noise sources from three components: the compressor and blower fan and its connected parts are excited resonance excitation. The compressor for the entire system to account for the .main sections. Due to the air conditioner compressor uses the occasion is special, noise and vibration requirements are higher, but due to a lack of experimental analysis of means, you cannot perform a thorough noise and vibration. This article can only be combined with relevant .literature and experience our experiment, noise source identification from the compressor, compressor, noise and vibration transmission channels, compressor noise radiation, etc. of compressor noise control method. <br> II. compressor noise and control <br> 1. compressor noise source .identification <br> As refrigerant compressors for all closed, the sound source can be divided into motor noise and mechanical noise. <br> 1.1 motor noise <br> Motor noise consists of electromagnetic noise, mechanical noise and aerodynamic noise. These electromagnetic noise generation .mechanism has the following three: <br> 1.1.1 hysteresis telescopic <br> Hysteresis expansion refers to the material in the volume of magnetization at scale. In General, this change is very small, and acoustic coupling of radiation, noise, noise generated .in frequency and in general the Harmonic frequencies, such as 50Hz, 100Hz Department. <br> 1.1.2 magnetic hysteresis <br> Hysteresis is the hysteresis material in the magnetic field of nonlinear effects, low hysteresis material despite lower hysteresis expansion properties, but .it is easier than the usual materials. When the material is saturated, power input will produce a series of motors harmonic, these harmonics in wide frequency vibrational excitation in the results. <br> 1.1.3 magnetic attraction <br> Magnetic attraction is the .motor structure of different polarity of mutual attraction, due to the gravitation of displacement than the hysteresis expansion resulting displacement of many attractive effects deform the motor air gap changes, easily produce oscillating magnetic field. Experimental discovery: when rotating piston or compressor rotation eccentricity increases by .10% to 20%, the motor electromagnetic noise will increase by 3-4dB. Of course, if the motor rotation of natural frequencies from the power supply frequency and motor electromagnetic noise drastically reduced. <br> In addition, the motor shaft and the .bearing to the interaction between form motor mechanical noise. You can view in plain bearing in the role of sliding sticky, sticky role will inspire other parts compressor produces high-frequency vibration. <br> 1.2 compressor machinery noise <br> Compressor valve plate movement .effects, gas pressure pulsation and various moving parts may become noise vibration excitation source. At the same time, since the overall motor and compressor block, the electrical connection is also a source of motivation compressor block. <br> Through the valve plate system modifications ., can significantly reduce compressor noise. Experimental discovery: with refrigeration system traffic increases, valve plate movement noise will increase as the main sound source. Typically, the moment of opening of the compressor, the compressor valve plate is the main noise excitation source, if .you can effectively eliminate the flutter valve, can greatly reduce the valve noise. <br> Compressor valve plate impingement seat can cause body vibration and noise. Through the study of the seat surface characteristics, on the valve and valve seat dynamic response, and other .factors, found through the following methods to reduce seat of impulse response: reducing valve plate on the seat of impact velocity, reducing valve lift limiter height, choose a tough soft seat materials to rupture valve seat of impedance matching. <br> In short, .the valve noise mainly by gas pressure pulsation, valve plate lifting noise and impact noise caused by the valve seat. To solve this kind of noise in the main measures are as follows: <br> A £ ® adopt suction and exhaust muffler <br> .B £ ® the right valve port shapes <br> C £ ® the right valve lift limiter and height <br> D £ ® increased valve spring dampers <br> As for the gas pressure pulsation on compressor noise impact, through experiment found that the .following phenomena: <br> Compressor overall noise as inspiratory pressure increases, noise reduction, with exhaust pressure increase noise increase. On the interpretation of this phenomenon is: suction pressure difference is reduced, lower rotary compressor imbalance moment, thus reducing noise. <br .> The compressor flow and noise has a strong correlation. Noise in the medium flow you reached the maximum value, as the traffic increases, the rapid decline of noise. Relationship of low frequency noise and traffic, the more noise in 4000Hz inspiratory pressure gradually reduced .to vacuum, a sharp decline. Therefore believes that the high-frequency noise and gas flow. <br> For rotary vane compressor, gas pressure pulsation of the compressor rotor and the cylinder is the maximum compressor noise excitation source. Experimentation found vent and turn .the tank pressure exists between a standing wave. By amplifying exhaust cavity and the creation of a drag chute eliminate standing wave, can in several bands and noise reduction. For the scroll compressor, the compression chamber pressure shock pulse is the most important noise source, .through the creation of conversion grooves can reduce pressure pulsation, adopt this idea in rolling piston compressor outlet at the creation of a muffler, modified, found on the high-frequency noise reduction is valid. <br> Compressor does not balance and unbalance torque on .the noise also has a large impact. In General, for single-cylinder reciprocating compressor, balanced block can only eliminate the base frequency of unbalanced force, which cannot be eliminated because the piston non-sinusoidal movements caused by the imbalance of power harmonics. < .br> Refrigerants and refrigeration oil also has the potential to become the vibration and noise of the excitation source. Freon in low temperature conditions arising when Flash cavitation can produce noise. <br> In addition, crankshaft compressor vibration is also produces high-frequency noise .. <br> 2. compressor noise vibration transmission channels <br> According to the structure of the hermetic compressor, we can put the delivery path can be divided into three categories: <br> 1. solid path (spring, pipe, block Assembly .) <br> 2. liquid way (frozen oil) <br> 3. gas channel ie refrigeration gas <br> 2.1 solid channel <br> Due to the size of the acoustic transmission and medium density characteristic impedance (And the product of sound .velocity). You can think of solid channel is the most important transport compressor. Noise reduction of the main measures are as follows: the natural frequency of vibration isolation selection as low spring, spring and body joints as possible selection of low impedance materials. < .br> In addition to the spring, the suction pipe is equally important for the delivery channel: compression ratio increases stiffness increase pipeline, thus increasing the natural frequency; when mass flow increases, the pipeline vibration frequency decreases, of course, but also enable the .pipe stiffness degradation, thereby avoiding compressor rotation frequency and harmonic. In addition if you are able to use an automobile air conditioner hose replacement existing copper tubes, also achieved good results. <br> 2.2 gas channel <br> Hermetic compressor cavity is filled with .the refrigerant gas, when the airframe vibration, the refrigerant is encouraging, on the one hand, the vibration transmission, on the other hand may have resonance, the zoom of vibration, allowing the shell to generate more noise. In addition, with the exception .of gas pulsations, the body's own vibration may also become resonance excitation source. <br> 3. compressor noise radiation <br> No matter how the mechanism inside the compressor, the compressor eventually to closed shell vibration to radiation in the form of noise. .Generally speaking, the compressor circumferential stiffness curvature RADIUS, gas pressure, gas density also on Shell's natural frequency. In the case of all the arguments, the capacity of its radiation factors having the greatest effect is its natural frequency. Typically, by increasing the rigidity .of the shell, improve compressor shell natural frequency, escape the incentive traffic higher-frequency range, can effectively reduce compressor vibration. Therefore, a reasonable shell shape should be small as far as possible the curvature RADIUS, try to avoid drastic changes curvature RADIUS. .<br> III. conclusions <br> Compressor noise control is an extremely complex issue, at present, we have just carried out a preliminary study. Next you need and the compressor manufacturers meet, through a number of experiments, analysis of various noise may .affect compressors, effectively reducing outdoor machine noise. <br> <br> About outdoor compressor noise peak and pipeline vibration method of thinking <br> Outdoor machine noise came mainly from the following sections: <br> Compressors, fan motors, connected to the .pipeline and the flow of refrigerant inside the tube. <br> Compressor noise and vibration from rotor rotation, mechanical pump body movement and refrigerant ripple shock vibration and gas-liquid separator and shell, corners of vibration, etc. <br> Specifically, the .compressor noise mainly in the following sections: <br> 1. motor noise: including electromagnetic noise, mechanical noise and aerodynamic noise <br> 2. mechanical noise: valve plate movement effects, gas pressure pulsation, various moving parts, motor and refrigerant flow .is compressor noise vibration excitation source. <br> Compressor noise vibration transmission channels: <br> 1. solid channel (spring, tube, compressor shell, etc.). <br> 2. the liquid channel (compressor oil). <br .> 3. gas channel (Refrigerant gas). <br> Solutions: <br> 1. be familiar with the internal structure of the compressor, analysis of compressor noise source, and delivery. (Outside help) <br> 2. understand the .pipeline of material properties. (Mechanical) <br> In the compressor and perfusion in determining, for the outdoor unit pipeline analysis, find unreasonable pipeline and find solutions. (Fluid mechanics, mechanics) <br> <br> <br> <br .> <br> <br>.