Development trend and exploration of new type of closed compressor
In order to adapt to the new market changes and situation requirements, the research on compressors is also deepening and broad, and some new research directions have emerged. Compressor technology is complex and manufacturing requirements are high, which means that in order to meet the needs of the market, we will have to work harder, pay close attention to changes in the situation, and stay ahead of market demand. 1 Policy requirements for fully enclosed refrigeration compressors 1. 1 Environmental protection Environmental protection requirements for refrigeration equipment are multifaceted, such as ozone layer damage, green design issues covering the entire life cycle of products, emissions of toxic and hazardous substances in raw and auxiliary materials and production processes, and recycling and recycling issues. The author only analyzes the problem of ozone layer damage. The ODS destruction of the ozone layer has been widely recognized internationally. As other ODS substances are gradually phased out, hydrochlorofluorocarbons (HCFCs), which can be used as refrigerants, blowing agents and cleaning agents in the refrigeration and air-conditioning industry, have become The largest remaining group of ODS is currently available. China, as the largest producer and consumer of HCFCs in Article 5 countries, is facing the huge challenge of freezing in 2013 and phasing out HCFCs consumption by 2030. The phase-out of H CFCs has entered a substantive implementation phase, and China's refrigeration and air-conditioning industry will face major challenges in eliminating HCFC 22 refrigerants. Article 5 National HCFCs phase-out requirements require that the experience of previous CFCs phase-out indicates that the supply of new refrigerant compressors will be the key to the industrialization of new refrigerant refrigeration and air-conditioning equipment. Therefore, the development and production of zero OD P and low GWP refrigerant compressors will be a major development direction for fully enclosed refrigeration compressors in the coming period. International research on alternatives to HCFC 22 refrigerants is underway and there are no clear conclusions yet, and the phase-out is not to be delayed. Judging from the current situation analysis, the future period will be a state in which a variety of alternative refrigerants coexist, and the investment and workload of refrigeration compressor development will double. 1. 2 energy saving Compressor is the main energy-consuming component of refrigeration and air-conditioning equipment. The improvement of compressor energy efficiency will directly bring energy saving to the whole machine. Moreover, the improvement of compressor energy efficiency does not depend on increasing material consumption, which is an ideal energy-saving way. Although energy conservation is an old topic, with the continuous improvement of energy efficiency, new demands have been made for energy-saving requirements for refrigeration and air-conditioning products. These changes will place new demands on the energy efficiency of the compressor. First, the national energy efficiency standards have continuously improved the energy efficiency requirements for refrigeration and air conditioning products. Taking the room air conditioner as an example, the new energy efficiency standard has greatly improved the energy efficiency limit value of the product. For products with a cooling capacity below 4 500 W, the energy efficiency limit value is increased from EER=2.6 to EER=3.2. It requires a more efficient compressor. Obviously, the improvement of energy efficiency under this kind of thinking is not unlimited. The 2010 and 2004 version of room air conditioner energy efficiency standards are second to none, and the energy saving requirements will be mainly reflected in the changes in product energy efficiency evaluation methods. This change is manifested in two aspects: On the one hand, the energy efficiency evaluation of many refrigeration and air-conditioning products is limited to a single evaluation price under a fixed working condition. Obviously, this evaluation method can not accurately reflect the energy efficiency of the product in use, and there will be false energy-saving phenomena. Taking a household refrigerator as an example, the power consumption of the refrigerator is tested at a fixed ambient temperature. During the test, the refrigerator has neither load nor door opening, which is far from the state of use, and the test is performed under such conditions. Power consumption does not represent the actual power consumption of the refrigerator. Taking the room air conditioner as an example, the energy efficiency of the current test speed air conditioner is only carried out under a fixed working condition, and the ambient temperature change during the actual use of the air conditioner is not considered, and the heating performance is not evaluated. Obviously it is also out of touch with reality. Changes in energy efficiency evaluation methods will be inevitable, such as during the process of testing the power consumption of the refrigerator, periodically opening the door and periodically adding new loads or even further changing the ambient temperature during the test to simulate the kitchen temperature changes in the four seasons; room air conditioner test At the same time, the test conditions were changed, and the cooling and heating were evaluated at the same time, and then the energy efficiency of the air conditioner was comprehensively evaluated by A PF. Another aspect of change will likely be manifested in the systematicization of energy efficiency evaluation. In many cases, the refrigeration equipment is only one component of a large system. Obviously, the efficiency of the refrigeration equipment as a component does not mean that the system is efficient. It is energy-saving to assess the energy efficiency at the level of the entire system energy process. A trend. In short, with the deepening of energy conservation work, the evaluation of product energy efficiency will be developed from point to line and from line to surface. The requirements for energy efficiency of refrigeration compressors will also be diversified, deep and systematic, and changes in compressor design. It will also be inevitable. 2 Market requirements for fully enclosed refrigeration compressors Efficient, low noise, high reliability and low price are the general requirements of the market for refrigeration compressors. All research on refrigeration compressors is carried out around this ultimate goal. In recent years, new demands for refrigeration compressors outside of these conventional requirements have emerged on the market. These requirements are mainly reflected in the expansion of refrigeration and air conditioning equipment applications. For example, compressors for heat pump water heaters, heat pump compressors for energy saving in industrial heating processes, heat pump compressors for energy recovery or renewable energy use, low temperature compressors for condensation recovery of gaseous materials, compressors for air conditioning water heaters, etc. The research of these compressors is different from the technical improvement of compressors in the existing application fields, but the expansion of the application field has put forward new requirements for the working condition range, design requirements and reliability of the compressors. 3 Main research directions of compressors In order to meet the overall requirements for energy saving, environmental protection, low noise, high reliability and low price of refrigeration compressors, research on compressors has never stopped. Research content includes mathematical simulation of refrigeration compressors, thermodynamic processes, dynamic processes, heat and mass transfer processes, flow, noise, vibration and gas flow pulsation, friction lubrication, gas valves, electric motors, development tools, testing techniques, capacity control, processes Processes, materials, refrigerant applications, and other aspects, including reciprocating compressors, rotor compressors, scroll compressors, speed compressors, screw compressors, and other traditional models, as well as oscillating compressors, linear New models or structures such as compressors. These research contents have been, are, and will be the main research direction of refrigeration compressors. The ultimate goal is to meet the general requirements of the above market for refrigeration compressors. Only a few research directions are illustrated here. 3. 1 Mathematical simulation Yasutaka Ito et al. established a mathematical model of the rotor compressor and analyzed the influencing factors of the rotational motion characteristics of the rolling piston through theoretical calculations. The results show that the friction between the rolling piston and the top of the sliding vane is the biggest influencing factor. The rotational motion is also affected by the inertia of the rolling piston. The relative sliding speed between the piston and the sliding plate can be reduced by reducing the mass of the rolling piston. . Joan L PEZ1 and others used the CFD HT method to establish a thermodynamic and hydrodynamic mathematical model of the reciprocating compressor, and calculated the temperature field, mass flow rate and pressure variation in the cylinder of the compressor. Mathematical simulation combines the knowledge of mathematical models and numerical calculations. It is a long-established tool for compressor research and can be used in all aspects of compressor research. The problem is that the various basic theories used in mathematical models are often not sufficient to describe the complex thermal, dynamic, and heat and mass transfer processes inside the compressor. They must be combined with the necessary special tests, otherwise they become pure digital games. 3. 2 friction lubrication Friction and lubrication of refrigeration compressors are key issues affecting compressor energy efficiency, life, reliability and noise. A lot of research has been done on it for a long time. The Reynolds equation describing the lubricant film thickness and the lubricant film pressure distribution is zh 3 P z + 1 R 2 h 3 P = - 6 U z hz - 6 U zz + 12 ht( 1) Bilgin Hac l oglu et al (1) For the boundary lubrication and hydrodynamic lubrication, the effects of different surface structures (surface roughness) in the longitudinal and transverse directions on the lubrication of the compressor piston were studied under the assumption of rigid surface. The results show that the surface structure has little effect on lubrication during hydrodynamic lubrication, but the influence of surface structure is very significant in the case of boundary lubrication. 3. 3 gas valve The gas valve is the weak link of the compressor, which directly affects the life and reliability of the compressor. At the same time, the correctness of the valve movement will also significantly affect the energy efficiency of the compressor. Therefore, although the research on compressor valves has been going on for decades, it is still in the ascendant and will continue. To some extent, the theory used in the gas valve research has been basically fixed. The problem is how to theoretically describe the movement of the valve more accurately, how to conveniently measure the movement of the valve and how to move the valve with the compressor. The performance is linked. Marcelo Alexandre REAL installed fiber displacement sensors and pressure sensors in the cylinders of reciprocating compressors, measured the motion of the compressor suction and exhaust valves, and the pressure inside the cylinders, and analyzed the effect of pressure changes on the valve movement. The valve is delayed or delayed. Shuhei NAGATA and the like used a strain gauge method to do a similar work, measuring the movement law of the valve. Obviously, the motion of the suction valve of the compressor under test is not normal: the chattering phenomenon caused by the excessive spring force will greatly increase the noise and vibration and reduce the efficiency of the compressor. This is the purpose of studying gas valves. This can also be done by mathematical simulation, but only if the calculation is accurate. The research of fully enclosed refrigeration compressors at home and abroad covers all the research directions mentioned above, and is only illustrated here, not enumerated. 4 New structure of new compressors and compressors In order to improve the quality of the compressor or to adapt to the expansion of the application field, new refrigeration compressor models are constantly emerging, either a new motion principle or a structural change of the existing motion principle. The author introduces several new structures for new compressors and compressors. 4. 1 linear compressor Linear compressors have been developed on the basis of reciprocating compressors. The drive motor of the conventional reciprocating compressor outputs a rotary motion, and the piston movement of the compressor requires reciprocation, so that the crank linkage mechanism must be used to convert the rotary motion of the motor into the reciprocating motion of the piston. Such motion conversion is indispensable, but it increases the number of moving parts and inevitable energy loss, which increases the vibration and noise of the compressor and reduces energy efficiency. If the motor outputs a reciprocating motion, the above problem can be completely avoided. Based on this idea, the concept of a linear compressor was formed. It adopts a linear motor that directly outputs reciprocating motion. The movement of the piston in one direction is driven by the motor, and the movement in the opposite direction is driven by a spring to form an electromechanical oscillation system to realize the reciprocating motion of the piston. Although it still relies on the reciprocating motion of the piston to compress the gas, it is fundamentally different from the conventional reciprocating compressor and can be regarded as a brand new compressor. The working principle of linear compressors has long existed. It has the inherent advantages of high energy efficiency and is a more promising compressor. However, it has high technical difficulty, and there is still a lot of work to be done in terms of extensive industrialization. At present, there are only small batch trials abroad. Some compressor manufacturers in China have also tried to develop such compressors, but no successful reports have been reported so far. 4. 2 Spiral Vane Compressor The working principle of the spiral vane compressor is as shown in the figure. The eccentricity is placed on the rotor in the cylindrical cylinder, and the variable pitch spiral groove is opened, and the variable pitch spiral blade is embedded in the groove. The helical blades are driven by the main shaft together with the rotor and rotate at the same speed, while at the same time there is a radial relative movement between the helical blades and the rotor. As the main shaft rotates, the enclosed volume composed of the spiral vanes, the cylinder and the rotor moves toward the exhaust end and gradually reduces the volume to achieve compression of the gas. The compressor has a simple and compact structure, and the stator of the motor can be placed outside the cylinder (using the spindle rotor as the rotor of the motor), and the motor and the pump body are overlapped, the axial dimension can be greatly reduced, and the performance is small. Noise and vibration, no air valve, forced exhaust. The prospect of widespread industrialization of such compressors is still unclear. 4. 3 swing compressor The oscillating compressor is a compressor developed on the basis of a rotor compressor. The rotor and vane of a conventional rotor compressor are two separate parts, and the slide is pressed against the rotor by the spring force of its back and reciprocates as the rotor moves. The rotor of the oscillating compressor is formed integrally with the slider, which is called a oscillating rotor. The working principle of the oscillating compressor is shown. The oscillating compressor eliminates the friction between the slider and the rotor and is suitable for applications with high pressure difference. Although it has not yet been mass-produced, it has certain development potential. Hiroki KAM IISHIDA et al. introduced a highly efficient oscillating compressor using a permanent magnet synchronous motor. 4. 4 3D scroll compressor As the research on conventional refrigeration compressors continues to deepen, the structure and function may undergo major changes, thereby forming a new structure of the compressor, which is the case with both the linear compressor and the oscillating compressor described above. H ajime SAT O et al. introduced a 3D scroll compressor based on a scroll compressor. The 3D scroll compressor is based on the radial compression of a conventional scroll compressor. The change in the height of the turn (lower center and constant height of the conventional scroll compressor) increases the axial compression of the gas. Compared with the traditional scroll compressor, it has the characteristics of high efficiency, low noise, compact structure and high reliability. 4. 5 CO 2 compressor and heat pump water heater CO 2 is a purely natural substance with a low GWP and is an environmentally friendly refrigerant. At the same time, its characteristics of the transcritical cycle also make it uniquely energy-saving in the application of heat pump water heaters. Strictly speaking, CO 2 compressors are new refrigerant compressors. Most of the existing compressor models such as reciprocating, rotor, scroll, and screw can be developed with this refrigerant. compressor. The problems to be solved are the strength problems caused by the high pressure and large pressure difference of the transcritical cycle and the lubrication and friction problems caused by the use of synthetic lubricating oil under high pressure. Considering the huge market development space of heat pump water heaters, CO2 compressors have good development potential and have become a major development direction of refrigeration compressors. At present, the development and industrial application of CO2 compressors for domestic heat pump water heaters have been waiting for a long time, and the development of CO2 heat pump water heaters still has certain difficulties. Heat pump water heaters use ordinary HCFC 22 compressors, which forms the market demand for HCFC 22 compressors for heat pump water heaters, and has become a development direction for refrigeration compressors in a short period of time. The problems that need to be addressed are the reliability caused by higher condensing temperatures, energy efficiency issues, and the large differences in operating conditions between winter and summer. 4. 6 new refrigerant compressor and CO2 Similar to the compressor, the new refrigerant compressor is not a new model. All existing compressor models such as reciprocating, rotor, scroll, and screw can be developed with various new refrigerants. compressor. At present, it is possible to replace H CFC 22 as a refrigerant in several categories: natural substances such as NH 3, H 2 O, R290 and CO 2 and mixtures of these substances; artificially synthesized elemental or mixed refrigerants such as R410A, R134a, R32 and R407C, etc.; and some mixed refrigerants still in development. Some of these refrigerant compressor technologies are mature and have the ability to be supplied in volume. The main development directions for the future are NH 3, R290, R32 and CO 2 and future refrigerants. The development of new refrigerant compressors is relatively simple. The main problem lies in the R&D investment and workload caused by the uncertainty of long-term replacement of refrigerants, as well as the transformation of manufacturing equipment and manufacturing processes. There are safety issues in the use of flammable and explosive refrigerants. 4. 7 other In addition, there are other new compressors or new compressor structures, such as rotary vane compressors, elliptical compressors developed using the principle of rotary guides, rotary cylinder driven rotor vane compressors and designed to improve heating. The performance of the gas-enhanced scroll compressor, etc., will not be repeated here. 5 Conclusion In summary, the development of the fully enclosed refrigeration compressor is characterized by the fact that the realization of thermodynamics, dynamics, heat and mass transfer, and lubrication friction must be based on grid information. Residential users in most areas of China have not even implemented the peak-to-valley time-based billing system. Some regions have to spend high investment to build pumped storage power stations. As the scale of renewable energy generation expands rapidly in the next few years, the problem of efficient and reliable operation of the grid is becoming increasingly prominent. The construction of intelligent power grid with the basic goal of building a strong power grid has been included in the agenda of China's power sector. The grid information construction for residential users will create conditions for the application of demand-responsive household appliances. China's related home appliance manufacturers are actively considering Demand response technology applications have made a difference.
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