小型制冷压缩机研究-----毕业设计外文翻译

Small COMPRESSOR

Compressor refrigeration system is the core and heart of its decision to the refrigeration system capabilities and features. This paper not only energy efficient, noise and vibration and refrigeration agent analyzed small refrigeration compressor technical performance, Analysis also have appeared in recent years, the new, special small compressor main feature for us small refrigeration compressor future development trend of laying a technological foundation.

As we all know, the compressor refrigeration system is the core and heart. Compressor and decided that the cooling system capacity and features. In a sense, the cooling system design and matching of the compressor is the ability demonstrated. Therefore, countries in the world are all in the refrigeration industry refrigeration compressor research invested a tremendous amount of energy, new research direction, and research results continue to emerge. Compressor technology and performance level with each passing day.

1.A compressor Efficiency Study

Compressor refrigeration system is the core energy components, improve the efficiency of refrigeration systems of the most direct and effective means is to increase the efficiency of the compressor, It will bring the energy consumption decreased significantly. Moreover, can only avoid the system take measures (such as simply increasing heat exchanger area, etc.) caused by the consumption of materials increased. In recent years, as world energy shortage situation worsens day by day, more and more attention to various energy-saving work the energy efficiency of products made by the ever-increasing demands. Due to losses such as friction, leakage, harmful heat, the electrical loss, flow resistance, noise vibration of existence, Compressor work far below the actual efficiency of theoretical efficiency. Therefore, from a theoretical point of view, any reduction in a loss of arbitrary measures to

improve the efficiency of the compressor. The objective facts have led to the energy saving compressor scope, direction, width, research topics and results varied.

On the current international energy-efficient compressors research concentrated mainly in a few areas : research lubrication properties Compressor parts of the friction bearings to reduce friction characteristics of power, improve the efficiency of the compressor; reduce leakage losses to improve the efficiency of the compressor; using frequency modulation technology or refrigeration system through the effort with the user load to match the best energy saving In this regard the particular frequency technology has been relatively mature well known and not repeat them here. Valve Research is an old topic but it is also an eternal topic, Improvement of the valve designed to improve the efficiency of the compressor also Nagamochi endless harvest. Research in this area many times, from the valve material, sports law, optimizing the structure of the applicable theory, exhaustive testing methods. In short, energy-saving compressors on the research in recent years has become one of the refrigeration industry first hot issues.

In recent years, domestic refrigeration compressor industry to study

energy-saving products are also giving great concern. Progress larger products mainly refrigerator compressor industry. In China efficient refrigerators GEF projects to promote and support, both the enterprises for energy-efficient products is the understanding of the performance of refrigerator compressors have a qualitative leap. At present, domestic enterprises refrigerator compressor products of the highest energy efficiency has reached 1.95%. Refrigerator compressor domestic enterprises to take a lot of technical measures such as high efficiency motors or synchronous motor, concave valves, Plane thrust bearing, low viscosity lubricants, the new Getter muffler, reducing friction losses, and achieved great results. The main problem is the lack of domestic enterprises currently free technology, the technology has to imitate the line mainly, Most of the enterprises to build their own technology infrastructure also

unconscious, nor the interest, and this restricts the development of technological capacity.

Relative to the refrigerator compressor industry, domestic energy-efficient

air-conditioning compressor study it was not perturbed, Over the years the efficiency of the compressor is no substantive change, greater market demand makes most of the air-conditioning compressor enterprises will concentrate on expanding production on. With the nation on the air conditioner energy efficiency standards set for the further improvement of China's air conditioner exports various perils of showing, domestic air-conditioning compressor of this short-sighted enterprises will be unable to adapt to the energy-saving development of the situation. Enterprise also on the follow-up is weak.

2. Compressor noise and vibration study

Currently, the noise has been regarded as one of the serious pollution. Household refrigeration equipment as the source of power and heart, refrigeration compressor noise, to be a measure of its performance as an important indicator. In fact, to a compressor speaking, Most of the noise is due to shell by some noise from the source excitation (such as springs, refrigerant pressure pulsation, exhaust pipe, lubricants etc. excited). But compressor noise sources and pathways complex and diverse, which gives the compressor noise silencer brought great difficulties.

On the compressor noise, vibration and foreign scholars have conducted a large number of long-term research. Here in this regard to the main research results are summarized below :

The main refrigeration compressor noise Exaggerative inlet, exhaust radiation aerodynamic noise, mechanical moving parts of machinery noise and noise-driven motor three components :

2.1 Aerodynamic noise

Compressor inlet airflow noise is due to the intake manifold pressure pulsation in the elections. Inlet-frequency noise and the intake manifold gas Lane same frequency pulsating with the speed of the compressor. Compressor exhaust noise is due to air in the exhaust pipe caused by fluctuating pressures. Exhaust noise than the inlet noise weak, so the compressor aerodynamic noise generally Inlet mainly noise

2.2 Mechanical Noise

Compressor mechanical noise, including members of the general impact and friction, the piston vibration, noise impact of the valve, These noise with randomness, was https://www.360docs.net/doc/0714444514.html,puted.

2.3Electromagnetic noise

Compressor electromagnetic noise is generated by the motor. Motor noise and aerodynamic noise and mechanical noise is weaker compared. Noise source compressor inlet, exhaust, aerodynamic noise, the strongest, followed by mechanical noise and electromagnetic noise. Through in-depth studies, we can further that the main compressor noise from the vibration (from the Department of spring, Refrigeration medium pressure pulsation and smoke exhaust pipe and lubricants have incentive) to the ambient medium spread formation noise. On the effort to reduce compressor noise, much of the literature (abbreviated) proposed a series of measures and the Noise and Vibration Reduction program :

① increase rigid shell structure to improve the overall resonance frequency reduces vibration amplitude;

② curvature of the shell to avoid mutation, the surface, and the natural frequency is inversely proportional to the radius of curvature. shell shape it should be the smallest curvature radius;

③ spring bearing flags will be moved to higher rigid position;

④ shell should be used as little as possible of the plane; bending stress and the stress coupling membrane (just on the surface) will shell itself is fairly rigid. Therefore compressor shell to be used as little as possible planar structure;

⑤ avoid the exhaust pipe and condenser incentive, optimizing exhaust flow pulsation, Exhaust pipe used in the introduction of additional volume to the elimination of pressure fluctuation spectrum of high-order harmonics;

⑥ non-symmetric shell shape; Symmetrical three-dimensional structure means that the axis, along the main axis biggest stress of least resistance. Therefore it is asymmetrical shell structure means that the compressor can be greatly reduced along the axis direction of a force while the probability;

⑦ set inlet, exhaust muffler, the closed Compressor Muffler generally muffler. It uses Cross Section, resonant cavity caused acoustic impedance changes in reflectivity or sound energy consumption. or use acoustic-acoustic send phase difference of 180 degrees to offset the muffler of noise. Shell compressor in the lateral closed Unicom a Helmholtz resonator, namely : Helmholtz resonator from the chamber through the neck hole and shell compressor connected into the internal cavity, to reduce compressor cavity stimulated acoustic modal amplitude. The results showed : resonator resonance frequency modulation of the actual compressor cavity stimulated the greatest vibration modes, will be substantially reduced resonance peak response spectrum and lead to significant change. However, it will affect the appearance and

the compressor refrigerator settings, the research results are not yet applied to products.

Lubricants and residual volume-coil motor windings will lead to the same types of bulk compressor levels between different (from levels average). By changing the shell external support to increase torsional stiffness and reduce vibration surface; Noise study the complex requirements of researchers has strong theory, the enterprise has good skills base and the need for greater investment and a longer timeframe. This is domestic enterprises compressor one of the weak links, which is now basically in the qualitative phase of experimental research, Along with a great chance and randomness.

3. new refrigerants Application

Based on the new environmental requirements of refrigerant compressor refrigeration industry is a hot issue. As for the refrigerator product R22 refrigerant substitutes the end of the work, new refrigerant compressor in the past few years mainly concentrated in the air conditioning industry. Apart from the now relatively mature R410A, R407C the study, The largest is the hot issue of CO2 compressor. This is the only issue for a briefing.

CO2 currently on the research and application of concentrated mainly in three aspects : one is the most urgent need of alternative refrigerants applications, such as automotive air conditioning, as refrigerant emissions, environmental harm, must be adopted as soon as possible without endangering the environment refrigerants; the other is to consider the characteristics of CO2 cycle, the most favorable to the use of this cycle of occasions, If heat pump water heater is to supercritical CO2 in hot conditions decentralization there is a significant temperature slip will help heat Water heated to a higher temperature characteristics of the focus of public attention; another one is CO2 into account the nature of heat transfer properties and characteristics of using CO2 as a refrigerant, taking into account CO2 good cold flow properties and

heat transfer characteristics, use it as a cascade refrigeration cycle cryogenic stage refrigerants.

Compressor transcritical carbon dioxide as an air conditioning system efficiency and reliability of the most affected parts, It should be fully integrated supercritical carbon dioxide cycle specific characteristics of a new design. Like ammonia and CO2, the adiabatic exponent K value higher, up 1.30, it may result in the compressor discharge temperature high, However, as the needs of CO2 compressor pressure ratio small, there is no need for cooling the compressor itself. Adiabatic index is high pressure over the small, I can reduce the gap compressor further expansion of the volume losses to the higher volume efficiency compressors. After experimental and theoretical research, Jurgen Horst SUB and found Kruse, reciprocating compressor is a good film sliding seal as the preferred CO2 system. 8:3 its carbon dioxide compressor exhaust valve for improved Exhaust improved compressor efficiency of carbon dioxide increased by 7%.

As the carbon dioxide pressure is far greater than the traditional critical circulatory pressure, compressor shaft seal design requirements than the original compressor is much higher, compressor shaft seal leakage over a period of time is still hampered Actually, the main reason.

Danfoss, Denso, ZEXEL such as carbon dioxide compressor has entered the stage of small batch production.

The IEA in March 1999, the Joint Japan, Norway, Sweden, Britain and the United States to activate the "Selected Issue on CO2 as working fluid Compression Systems in the "three-year project.

Beginning in 1994, BMW, DAIMLERBENZ VOL O, Germany's Volkswagen and Danfoss. Péchiney and other European companies launched the famous "RACE"

to the joint project, the Joint European well-known universities, automotive air conditioning manufacturers and other developed CO2 automotive air-conditioning system. Subregion Motor Company has production equipment CO2 car

air-conditioning systems of cars, Germany KONVECTA production to the quality of CO2 in the air-conditioned Buses run from 1996 to date. DANFOSS, the Obrist Austria, the United Kingdom have developed a carbon dioxide compressor motor. Japan DENSO, ZEXEL CO2 compressor has entered the stage of mass production.

With major manufacturers inputs, the type of CO2 compressor with ordinary motor compressor trend line major swing to determine the displacement swashplate, scroll and the main variable displacement.

4. New principle of refrigeration compressors

In recent years, the new structure and working principle of refrigeration compressor made a more progress, mainly linear compressor, Elliptic compressors, compressor rotor Swing, spiral vane compressor, in the past, the author has been described in the article, here will not repeat it.

Linear compressor which is the domestic refrigerator compressor industry the focus of attention. In 2004 the International Compressor Engineering Conference has five linear compressor on the article. LG and researchers still Sunpower two main companies. The past two years, several domestic enterprises in the refrigerator compressor to the development of the linear compressor, However, enterprises have the technical foundation for the domestic financial strength and the limitations of scientific research institutions, believe in a short period of time can not enter the stage of industrialization.

5 the classification of the refrigeration compressor

5.1 reciprocating compressor

Reciprocating compressor is a kind of traditional refrigeration compressor, the biggest characteristic is to achieve the capacity and pressure than any of the design. Although it is widely applied, but the market share is gradually reduced.

So far, the fridge (including small freezing and cold storage device) host compound compressor is ever to give priority to. Through the optimal design of valve structure, friction pair, reciprocating refrigerator compressor refrigeration coefficient of power refrigerating capacity (units) by 1.0 (w/w) of the early ninety s to today's 1.8 or so; In addition to the energy saving technology progress, and environmental protection is closely related to the refrigerant alternative technology has also made gratifying progress, refrigerator system in our country has a large number of using R600 hydrocarbons, such as small refrigeration device is also used the new working substance such as everything. To further improve the efficiency of the reciprocating compressor refrigerator, to reduce the system noise is still the development direction of it.

5.2 linear compressor

Still make reciprocating linear compressor, due to the linear motion of the motor can be directly drives the piston reciprocating motion, so as to avoid the complexity of the crank connecting rod mechanism and the resulting mechanical power consumption. Linear compressor assembly as the refrigerator system has appeared, the refrigeration coefficient of linear refrigerator compressor has more than 2.0 (w/w), market prospects look good. The main problem is the design of the compressor oil system and the effective control of linear motor displacement limit point and the corresponding anti-collision cylinder technology.

5.3 the swash plate compressor

Swash plate compressor is also a kind of variant structure of reciprocating compressor, is mainly used in automotive air conditioning system at present. After decades of development, the swash plate compressor has become a very mature model, in possession of more than 70 of the automotive air conditioning compressor market. In spite of this, because it still belongs to the series of reciprocating structure, so in the

car air conditioning system can effect comparing (refrigeration coefficient) and only around 1.5, weight and volume is big, big. Because of the mature of swashplate automobile air conditioning compressor technology, combined with technology, further improvement in the foreseeable future, will continue to maintain a certain market share, but in a certain displacement range by substituting is inevitable.

5.4 rotor compressor

Rotor compressor in the 1970 s by the attention of domestic, it represents the structure including the rolling piston type, sliding-vane, etc. On the rolling piston type is widely used in household air conditioner at present, there are also some applications on the refrigerator. This kind of compressor don't need air suction valve, make it suitable for variable speed operation, which can improve system performance by frequency conversion control. In order to ensure high power (3 p) of the motor output power in the performance of the rolling piston compressor, the domestic research and development and the end of last century, double rotor rolling piston compressor, is now on the market. Double rotor on the rolling piston compressor structure has two advantages: (1) force of the rotating system be improved, the machine vibration and noise is reduced; (2) increase the standalone swept volume and improve the output power of the motor.

Below 3 p air conditioning unit, temporarily can not replace a good model of the rolling piston compressor. So improve the efficiency of the compression process, reduce noise and motor speed control and the R410A and other related technical issues after new refrigerating agent, etc., is a research direction of the rolling piston compressor.

Sliding vane compressor is a kind of rotor compressor, mainly used to provide compressed air, displacement is in commonly 0.3-3 m3 / min, the market share is low. Rotary vane compressor sliding vane compressor is a kind of transition structure, because of its better starting performance, the compression process torque change is not big, at present is mainly used for miniature cars and some smaller displacement

plumbing vehicle air conditioning system. The dynamic characteristics under high speed is the main technology of this compressor research direction.

5.5 screw compressor

Screw compressor with small size, light weight, easy to maintenance etc., is a model of the fast development in refrigeration compressor. On the one hand, the screw type line, structural design has made considerable progress, on the other hand, the introduction of special screw rotor milling especially grinding, improve the machining precision and machining efficiency of key parts, makes the performance of screw compressor has been effectively improved, industrialization production of the necessary hardware also has the safeguard. At present, the screw compressor is given priority to with compressed air, in medium ReBengShi air conditioning has successful application in the system. Due to increasing the reliability of the screw compressor work within the scope of the medium refrigerating capacity has gradually replace of reciprocating compressor and occupied most of the centrifugal compressor market. 5.6 scroll compressor

Scroll compressor has been rapid development in the past ten years, the structure of the basic theory, research and development to achieve large-scale industrial production, industrial prototype constitutes the compressor technology development new luminescent spot. The development of numerical control processing technology to realize the mass production, the vortex compressor incomparable performance advantage is the precondition of its vast in the market. A few short years, has been in the field of cabinet air conditioning holds an absolute advantage. In cabinet air conditioning system, scroll compressor refrigeration coefficient has amounted to 3.4 (w/w); In the field of automotive air conditioning, the refrigeration coefficient of scroll compressor has amounted to 2.0 (w/w), and shows strong competition potential. The development of the vortex compressor is to enlarge its range of refrigerating capacity, further improve the efficiency, using alternative working medium and lower the manufacturing cost, etc.

Since there is no valve, compression force and torque and small changes in the structure make it more suitable for the advantages of frequency control of motor speed operation, it also become the main direction of scroll compressor technology development. Development of scroll compressor of variable displacement mechanism is the key point of the development of the technology. At present, the use of axial sealing technology, "flexible" theory can realize cooling/heating capacity of 10% to 100% within the scope of the regulation.

Due to the vortex compressor suction exhaust characteristic of almost continuous, low starting torque and liquid impact resistance, created the condition for parallel use of vortex compressor. In parallel with the vortex compressor can greatly increase the cooling capacity of the unit, can increase from the current single 25 horsepower to single unit 100 horsepower (4 sets of single parallel), and makes the cold quantity adjustment is more reasonable, give full play to the single machine with the highest efficiency. But single in parallel, one of the biggest problems is the oil return is not the average of the unit when using single machine burning phenomenon.

3.1.5 centrifugal compressor

At present in large quantity of cold (greater than 1500 kw) remain within the scope of advantage, this is mainly benefited from the cold quantity range, it has incomparable system overall efficiency. The movement of the centrifugal compressor parts little and simple, and its manufacturing precision is much lower than the screw compressor, these are the characteristics of the manufacturing cost is relatively low, and reliable. Relatively speaking, the development of centrifugal compressor is slow, due to the challenges of the screw compressor and absorption chiller. Centrifuge market capacity is around 700 ~ between 1200, because under the premise that the current technology, the machine is mainly used for air conditioning of large buildings, demand is limited. In recent years because of the large infrastructure projects are built, the centrifugal refrigeration and air conditioning compressor is becoming a hot spot of attention again. Solve surge phenomenon, improve the volume adjustment and the

adaptability to change with working condition, miniaturization technology is the main development direction of the centrifugal compressor technology.

3.1.6 other structure forms

Single tooth of the compressor, some structures, such as cross slider compressor unique positive displacement compressor also has a certain degree of development, but has not been formed in the domestic production capacity.

5. Special refrigeration compressors

Although domestic enterprises household refrigeration compressors long accustomed to large-scale production mode, we are accustomed to the number of effectiveness. However, the fierce price competition situation, as products become increasingly lower profit margins, When the production of millions of compressors can only make a few million dollars of profit, some on special refrigeration compressors can be regarded as a way out. Special refrigeration compressor exhaustive, it is impossible in this enumeration. But their common feature is their production scale is small, a single high-profit products faster transition, In most cases the need for the user's requirements designed. These products lead to more and more domestic enterprises to the compressor. If the number of domestic enterprises are developing or already have production capacity of the refrigerator compressor truck

翻译

小型制冷压缩机研究

压缩机是制冷系统的核心和心脏,它决定了制冷系统的能力和特征。本文不仅从高效节能、噪声和振动以及制冷剂等方面分析了小型制冷压缩机的技术性能,还解析了近年出现的新型、特种小型压缩机的主要特点,为我们掌握小型制冷压缩机未来发展趋势奠定了技术基础。

众所周知,压缩机是制冷系统的核心和心脏。压缩机的能力和特征决定了制冷系统的能力和特征。某种意义上,制冷系统的设计与匹配就是将压缩机的能力体现出来。因此,世界各国制冷行业无不在制冷压缩机的研究上投入了大量的精力,新的研究方向和研究成果不断出现。压缩机的技术和性能水平日新月异。

本文将就近年来小型制冷压缩机的技术研究与发展作一综述性的探讨。

1 压缩机的高效节能研究

压缩机是制冷系统的核心耗能部件,提高制冷系统效率的最直接有效手段是提高压缩机的效率,它将带来系统能耗的显著降低。同时这样还能避免仅在系统上采取措施(如一味加大换热器面积等)所造成的材料消耗的大量增加。近年来,随着世界上能源紧缺形势的日益严重,各个国家越来越重视节能工作、对耗能产品的效率提出了越来越高的要求。由于各种损失诸如摩擦、泄漏、有害传热、电机损失、流动阻力、噪声振动等的存在,压缩机工作时实际效率远低于理论效率。因此,从理论上讲,任何能够降低任意一种损失的措施都能够提高压缩机的效率。这一客观事实导致了对压缩机的节能研究范围广、方向宽,研究课题与研究成果多种多样。

目前国际上对压缩机的节能研究工作主要集中在几个方面:研究润滑特性、压缩机轴承部位的摩擦特性以降低摩擦功耗、提高压缩机效率;降低泄漏损失以提高压缩机的效率;采用变频或变容技术通过制冷系统的出力与用户负荷的最佳匹配来实现节能,有关这方面的内容特别是变频技术目前已相对较为成熟且广为人知,在此不予赘述;气阀的研究是一个古老的课题但也是一个永恒的课题,改进气阀的设计以提高压缩机效率的研究永无止境也永有收获。这方面的研究非常之多,从气阀材料、运动规律、结构优化到适用理论、测试方法等包罗万象。总之,关于压缩机节能方面的研究已成为近年来制冷行业的一个首要热点问题。限于篇幅,本文在此不作具体的专题讨论。

近年来国内的制冷压缩机行业对产品的节能研究也给予了极大的关注。进展较大的产品主要是冰箱压缩机行业。在UNDP/GEF中国节能冰箱项目的推动和支持下,无论是企业对节能产品的认识还是冰箱压缩机的性能都产生了质的飞跃。目前国内企业冰箱压缩机产品的最高能效已达到1.95 左右。国内的冰箱压缩机企业采取了大量的技术措施诸如高效电机甚至同步电机、凹形气阀、平面止推轴承、低粘度润滑油、新型吸气消音器、降低摩擦损失等,取得了巨大的效果。主要的问题在于目前国内企业缺乏自由技术、所采取的技术路线还以模仿为主,多数的企业对建立自己的技术基础还无意识、也无兴趣,制约了企业的技术发展能力。

相对于冰箱压缩机行业,国内空调压缩机的节能研究还显得波澜不惊、多年来压缩机的效率没有质的变化,较大的市场需求使得大多数的空调压缩机企业将精力集中在扩大产能上。随着国家对空调器能效水平要求的进一步提高以及我国空调器出口各种隐患的逐步呈现,国内空调压缩机企业的这种短视将无法适应节能形势发展的要求,也使企业的后续发展乏力。

2 压缩机的噪音与振动研究

目前,噪声已被视为严重污染之一。作为家用制冷设备的动力源和心脏,制冷压缩机的噪声问题,以成为衡量其综合性能的一个重要指标。实际上对于一台压缩机来讲,大部分噪声都是由于壳体被某些噪声源激发所产生的(例如被弹簧、制冷剂压力脉动、排气管、润滑油量等激发)。但压缩机的噪声源和传递途径复杂多样,这就给压缩机的消声降噪带来了很大困难。

关于压缩机的噪声、振动,各国学者已经进行了大量且长期的研究。这里将这方面的主要研究工作成果概括如下:

制冷压缩机的主要噪声源由进、排气辐射的空气动力噪声、机械运动部件产生的机械噪声和驱动电机噪声三部分组成:

2.1 空气动力噪声

压缩机的进气噪声是由于气流在进气管内的压力脉动而产生的。进气噪声的基频与进气管里的气体脉动频率相同,与压缩机的转速有关。压缩机的排气噪声是由于气流在排气管内产生压力脉动所致。排气噪声比进气噪声弱,所以,压缩机的空气动力性噪声一般以进气噪声为主。

2.2 机械噪声

压缩机的机械性噪声,一般包括构件的撞击、摩擦、活塞的振动、气阀的冲击噪声等,这些噪声带有随机性,呈宽频带特性。

2.3 电磁噪声

压缩机的电磁噪声是由电动机产生的。电机噪声与空气动力性噪声和机械性噪声相比是较弱的。压缩机噪声源中进、排气空气动力性噪声最强,其次为机械性噪声和电磁噪声。通过深入研究,可以进一步认为压缩机噪声主要来自壳体振动(系由弹簧、制冷介质压力脉动和吸、排气管以及润滑油激励产生)并向周围空气介质传播而形成噪声。围绕降低压缩机辐射噪声,众多文献(略)提出了一系列的降噪减振措施和方案:

①增加壳体结构整体刚性以提高共振频率且降低振动幅值;

②避免壳体曲率的突变,对于曲面而言,固有频率与曲率半径成反比,因此壳体形状应采用最小的曲率半径;

③将悬挂弹簧支承移至具有较高刚性的位置;

④壳体应采用尽可能少的平面;弯曲应力与膜应力的耦合(只出现在曲面上)会使壳体本身具有较大的刚性,因此压缩机壳体应尽可能少地采用平面结构;

⑤避免排气管路和冷凝器的激励,优化排气气流脉动,采用在排气管路中引入附加容积的方法来消除压力脉动谱中的高阶谐波量;

⑥采用非对称的壳体形状;具有对称结构意味着具有三维主轴,沿主轴应力最大且阻力最小。因此具有不对称压缩机壳体结构意味着能够大大减小沿某一主轴方向作用力同时出现的几率;

⑦设置进、排气消声器,封闭式压缩机中的消声器一般为抗性消声器,它利用管道截面变化、共振腔引起声阻抗改变来反射或消耗声能,或利用声程差使声波相位相差180度来抵消消声器内的噪声。在压缩机壳体外侧封闭联通一个Helmholtz共鸣器,即:由Helmholtz共鸣器的腔室通过孔颈与压缩机壳体内部空腔相连成,以降低压缩机腔内受激声学模态的幅值。实验结果表明:将共鸣器共振频率调制到实际压缩机空腔的最大受激振动模式上,会大幅降低共振峰值和导致响应频谱的显著改变。但是这样会影响压缩机外观和在冰箱中的布置,其研究结果尚未应用于产品中。

剩余润滑油量和电机端线圈绕组也会导致同种型号成批压缩机声级之间存在差异(偏离声级平均值)。通过改变壳体外部支承来增加扭转刚度,且减小振动面;噪声研究的复杂性要求研究者具有较强的理论素质、要求企业具有较好的技术基础、并且需要较大的投资和较长的时间。这方面是国内压缩机企业的薄弱环节之一,目前基本上处于定性的实验研究阶段,伴随着很大的随意性和偶然性。

3 新制冷剂的应用

基于环保要求的新制冷剂的应用也是制冷压缩机行业的一个热点问题,随着用于冰箱产品的R22制冷剂替代工作的结束,新制冷剂压缩机的研究近年来主要集中在空调行业。除了目前已比较成熟的R410A、R407C方面的研究外,近年来最大的热点问题是二氧化碳压缩机的研究。本文仅对这方面的问题作一介绍。

目前关于CO2的研究和应用主要集中于三个方面:一方面是最急需替代制冷剂的应用场合,如汽车空调,由于制冷剂排放量大,对环境的危害也大,必须尽早采用对环境无危害的制冷剂;另一方面是考虑到CO2循环的特点,最利于采用这种循环的应用场合,如热泵热水器则是考虑到CO2在超临界条件下放热存在一个相当大的温度滑移有利于将热水加热到一个更高的温度的特点而倍受关注;再一方面是考虑到CO2的热物理性质和迁移性质特点,采用CO2作为制冷剂,如考虑到CO2良好的低温流动性能和换热特性,采用它作为复叠制冷循环低温级制冷剂。

压缩机作为跨临界二氧化碳空调系统效率及可靠性影响最大的部件,应当充分结合二氧化碳超临界循环具体特点重新进行设计。CO2和氨一样,其绝热指数K 值较高,达1.30,这可能会使压缩机排气温度偏高,但由于CO2需要的压缩机的压比小,因此不需要对压缩机本身进行冷却。正因为绝热指数高,压比小,可减小压缩机余隙容积的再膨胀损失,使压缩机容积效率较高。经过实验和理论研究,Jurgen SUB和Horst Kruse发现,往复式压缩机有良好的油膜滑动密封,成为CO2系统的首选。BOCK对其二氧化碳压缩机排气阀进行了改进,排气改良后的二氧化碳压缩机效率提高了7%。

由于二氧化碳系统压力远远大于传统的压临界循环系统,压缩机的轴封设计要求比原有压缩机高得多,压缩机的轴封泄漏在一段时间内仍将是目前阻碍其实用化的主要原因。

Danfoss、Denso、ZEXEL等已进入二氧化碳压缩机小批量生产阶段。

IEA在1999年3月,联合日本、挪威、瑞典、英国和美国启动“Selected Issue on CO2 as working Fluid in Compression Systems”的三年计划项目。

1994年起,BMW、DAIMLERBENZ、VOL O、德国大众、Danfoss、Valeo

等欧洲著名公司发起了名为“RACE”的联合项目,联合欧洲著名高校、汽车空调制造商等研制CO2汽车空调系统。BENZ 汽车公司现已生产装备CO2汽车空调系统的轿车,德国KONVECTA 生产的以CO2为工质的空调公交客车从1996年运行至今。DANFOSS、奥地利的Obrist、英国均已研制出二氧化碳车用压缩机。日本的DENSO、ZEXEL的二氧化碳压缩机已进入批量生产阶段。

随着各大生产厂商的投入,CO2压缩机的型式也与普通车用压缩机的发展趋势相一致,主要以定排量摇摆斜盘式、涡旋式和变排量为主。

4 新型工作原理的制冷压缩机

近年来在全新工作原理和结构的制冷压缩机方面未见有更多的进展,主要有线形压缩机、椭圆压缩机、摆动式转子压缩机、螺旋叶片式压缩机等,作者在以往的文章中已有叙述,这里不予重复。

其中线形压缩机仍是国内冰箱压缩机行业关注的热点。在2004年国际压缩机工程会议中有5篇关于线形压缩机的文章。研究者仍以LG 和Sunpower 两家公司为主。最近两年,国内有数家冰箱压缩机企业在尝试线形压缩机的开发,但就企业所具有的技术基础、资金实力和国内科研机构的局限性而言,相信在短时间内不可能进入产业化阶段。

5 制冷压缩机的分类

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