[edit]Compressor Overview
1. Compressor (compressor), conveying gases and increase the gas pressure of a slave fluid machinery. Is the heart of the refrigeration system, it is from the suction tube inhalation of low-temperature low-pressure refrigerant gas, through the operation of the motor to drive the piston compression, to the exhaust pipe discharge of high temperature and high pressure refrigerant gas, to provide power for the refrigeration cycle, so as to realize the compression → condensation → expansion → evaporation ( heat absorption ) of the refrigeration cycle. Compressor generally consists of shell, motor, cylinder, piston, control equipment (starter and thermal protector) and cooling system. Cooling methods include oil cooling and natural cooling.
General household refrigerator and air conditioner compressor is a single-phase alternating current as a power source, their structure is basically the same principle. The two use different refrigerant.
2. Manufacturing methods
Compressors are produced in an assembly line manner. In the machining shop (including casting) to manufacture the cylinder, piston (rotor), valve plate, connecting rod, crankshaft, end cap and other parts; in the motor shop to assemble the rotor, stator; in the stamping shop to manufacture the shell and so on. Then in the assembly workshop assembly, welding, cleaning and drying, and finally passed the inspection and packaging factory. Most compressor manufacturers do not produce starters and thermal protectors, but according to the need to purchase from the market.
3. Types
Currently, household refrigerator and air conditioner compressors are volumetric, which can be divided into reciprocating and rotary. Reciprocating compressors use a piston, crank, connecting rod mechanism or piston, crank, slide tube mechanism, and rotary use a rotary crankshaft mechanism.
According to the scope of application can be divided into low back pressure type, medium back pressure type, high back pressure type. Low back pressure ( evaporation temperature -35 ~ -15 ℃ ), generally used in household refrigerators, food freezers, etc.. Medium back pressure ( evaporation temperature -20 ~ 0 ℃ ), generally used for cold drinks cabinet, milk refrigerator, etc.. High back pressure ( evaporation temperature -5 ~ 15 ℃ ), generally used for room air conditioners, dehumidifiers, heat pumps and so on.
4. Specifications, quality
Compressor specifications are divided by input power. Generally, the difference between each specification is about 50W. In addition, there are also divided by cylinder volume.
The main performance indicators of the compressor are: input and output power, coefficient of performance, refrigeration capacity, starting current, operating current, rated voltage, frequency, cylinder volume, noise and so on. Measure the performance of a compressor, mainly from the weight, efficiency and noise of the three aspects of the comparison.
In accordance with China's standards, its safety performance test is based on the GB4706.17-2004 project. Among the main items are electrical strength, leakage current, plugging, and overload operation test.
The performance test of air-conditioner compressor is based on GB5773-2004.
In addition, in the product finalization and production of major changes that may affect product performance, continuous production for one year or more than one year between production, as well as factory test results and type test has a big difference, must be type test.
5. Packaging, storage and transportation
Packaging and transportation of compressors can be handled in accordance with the contract. Large quantities of imported compressors, generally in cartons and then shipped in containers. Compressor in the box should be fixed firmly, and moisture-proof and shock-proof measures. Storage and transportation is not allowed to be inverted, and stored in a well-ventilated warehouse, the relative humidity can not exceed 80%, there can not be corrosive gases.
6. Precautions
The compressor is allowed to pull out the sealing rubber plug only when it is in use. If the plug is found to be dislodged or loose during storage and transportation, it should be inspected and treated in time before storage.
Refrigerator compressor and air conditioner compressor must be CCC certification before sales. [3]?
Pictures of compressors
[edit]What are the requirements for compressors to run under load?
The first load run of the compressor is performed after the empty run and blowdown are completed. The compressor should be loaded according to the following requirements:
1, after driving gradually close the venting logging or oil and water blowdown logging, in the compressor's 1/4 rated pressure running for 1 hour; in the 1/2 rated pressure running 4-8 hours.
2, the compressor running at minimum pressure, no abnormalities, before the pressure gradually increased;
3, for large high-pressure compressor, the nominal pressure of the running time shall not be less than 24 hours;
4, the operation of the process, check the following items:
(1) lubricating oil pressure, temperature and oil supply. Oil pressure shall not be less than 1 kg/cm2 before being sent to the distribution pipe system. crankcase or body lubricant oil moisture should be: compressor with a crosshead shall not exceed 60 ℃. Those without crossheads shall not exceed 70°C.
(2) compressor running smoothly, the sound of moving parts should be normal.
(3) measure the inlet and outlet water temperature and check the cooling water supply, cooling water is not allowed to intermittent flow and bubbles and blockage and other phenomena. Cooling water drainage temperature shall not exceed 40 ℃.
(4) Each NMSA connects the flange part, shaft seal, inlet and exhaust felling, cylinder head and water jacket, etc., and shall not leak air, oil or water.
(5) The work of the intake and exhaust felling should be normal, and the safety felling is sensitive.
(6) There shall be no loosening of the connecting parts.
(7) Measurement of exhaust temperature and pressure at all levels should be in line with the provisions of the technical conditions.
(8) The motor heating condition and current value shall be in accordance with the regulations.
5, operation is completed, disassembly and inspection of the following items:
(1) disassembly of all levels of gas logging, all levels of cylinder front cover, check the cylinder mirror friction, such as traces of friction should be to find out the cause.
(2) Check the piston rod surface friction, there should be no abrasion marks and the phenomenon of pull road.
(3) dismantle all levels of gas logging, check the logging piece and logging body fit, logging piece if cracked, with spare parts for.
(4) Check the friction between the cross slide, and the friction surface of the body guide.
(5) Disassemble the connecting rod big head tile, cross head pin, check the friction of the friction surface.
6, replace the lubricating oil in the body. Compressor after the initial operation; due to the machine parts of the various parts of the decapitation, and lubricating oil cleaning effect, there are a large number of fine metal powder into the lubricating oil, therefore, the machine after 24 hours of work that should be replaced after all the lubricating oil. After running for 200 hours, change the new oil again. Replacement of two times, according to the regular maintenance requirements for oil change.
In order to make the exhaustion of the uniform, the initial operation must make all parts of the adequate lubricating oil.
Common compressor failure and its causes and measures to solve
Failure of the first - insufficient exhaust
Insufficient exhaust is the compressor is one of the most likely to appear one of the faults, which occurs mainly due to the following reasons:
1, the intake filter failure: clogging of dirt, so that the exhaust volume is reduced; suction, the suction filter, the exhaust volume is reduced, the exhaust volume is reduced.
2, compressor speed to reduce the exhaust volume: improper use of air compressors, air compressor exhaust volume is designed according to a certain altitude, suction temperature and humidity, when it is used in more than the above standard plateau, suction pressure, etc., the exhaust volume is bound to decrease.
3, cylinder, piston, piston ring wear serious, super poor, so that the gap increases, the leakage increases, affecting the exhaust volume. Belong to the normal wear and tear, need to replace wear parts, such as piston rings. Belongs to the installation is not correct, the gap left inappropriate, should be given according to the drawings to correct, such as no drawings, can take the empirical information, for the piston and the cylinder along the circumference of the gap, such as cast iron piston, the gap value of the cylinder diameter of 0.06 / 100 ~ 0.09 / 100; for aluminum alloy piston, the gap for the diameter of the gas diameter of the 0.12 / 100 ~ 0.18 / 100; steel pistons can take the Aluminum alloy piston can take the smaller value.
4, stuffing box is not strict, resulting in air leakage to reduce the amount of gas. The reason is first of all, the packing box itself is not required when manufacturing; secondly, it may be due to the installation, the piston rod and packing box center is not good, resulting in wear and tear, such as strain caused by air leakage; generally in the packing box at the injection of lubricating oil, which can play a role in lubrication, sealing, cooling.
5, the compressor suction and discharge valve failure on the impact of exhaust. Valve seat and valve piece of the valve fall into the metal fragments or other debris, resulting in poor closure, the formation of air leakage. This not only affects the amount of exhaust, but also affects the interstage pressure and temperature changes; the emergence of this problem may be due to a manufacturing quality problems, such as valve warping, etc., the second is due to the valve seat and valve wear and tear and the formation of air leakage.
6, the valve spring force and gas force matching is not good. The elastic force is too strong so that the valve is slow to open, the elastic force is too weak, the valve is not closed in time, these not only affect the gas volume, but also affects the increase in power, as well as the valve valve, the spring's life. At the same time, it will also affect the gas pressure and temperature changes.
7, the pressure of the gas valve compression force is not appropriate. Compression force is small, then to leakage, of course, too tight is not good, will make the valve cover deformation, damage, general compression force can be calculated using the following formula: p = kπ/4 D2P2, D is the diameter of the valve cavity, P2 is the maximum gas pressure, K is greater than the value of 1, generally take 1.5 ~ 2.5, low-pressure K = 1.5 ~ 2.0, high-pressure K = 1.5 ~ 2.5. so take K, practice has proved to be good. With a faulty valve, the bonnet is bound to heat up, and at the same time the pressure is not normal.
Failure two - exhaust temperature is not normal
Exhaust temperature is not normal means that it is higher than the design value. Theoretically, the factors affecting the exhaust temperature increase are: intake temperature, pressure ratio, and compression index (for air compression index K = 1.4). The actual situation affects the suction temperature high factors such as: intermediate cooling efficiency is low, or the intercooler scale junction affects the heat transfer, then the suction temperature of the back stage is bound to be high, the exhaust temperature will also be high. In addition, valve leakage, piston ring leakage, not only affects the exhaust temperature rise, but also will make the interstage pressure changes, as long as the pressure ratio is higher than normal will make the exhaust temperature rise. In addition, water-cooled machines, lack of water or insufficient water will make the exhaust temperature rise.
Failure three - pressure is not normal as well as the exhaust pressure reduction
Compressor discharged under the rated pressure can not meet the user's flow requirements, the exhaust pressure is bound to reduce. At this point, had to change another exhaust pressure is the same, but the exhaust volume of the machine. The main reason affecting the interstage pressure is not normal is the valve leakage or piston ring wear leakage, so should be from these aspects to find the reasons and take measures.
Failure four - abnormal sound
Compressor if some parts of the failure, there will be an abnormal sound, in general, the operator can identify the abnormal sound. Piston and cylinder head clearance is too small, direct impact; piston rod and piston connecting nut loose or debuckle; piston end of the silk plug juniper, the piston upward string collision cylinder head; cylinder into the metal fragments as well as the cylinder in the accumulation of water, etc. can be in the cylinder to send out a knocking sound. Crankcase crankshaft tile bolts, nuts, connecting rod bolts, crosshead bolts loose, buckle, broken, etc., serious wear and tear of the axle diameter clearance increases, crosshead pin and bushing clearance is too large or wear and tear, etc. can be issued in the crankcase knocking sound. Exhaust valve broken, the valve spring is loose or damaged, load regulator is not adjusted properly, etc. can be issued in the valve chamber knocking sound. From this to find the fault and take measures.
Failure five - overheating failure
In the crankshaft and bearings, crosshead and slide, packing and piston rod friction, the temperature exceeds the specified value called overheating. Consequences of overheating: one is to accelerate the wear and tear between the friction vice, the second is the overheating of the heat energy accumulates until the friction surface burned and cause major accidents. Causes of overheating bearings are: bearings and journal fit unevenly or contact area is too small; bearing skewed crankshaft bending, lubricant viscosity is too small, oil blockage, oil pump failure caused by the oil; installation is not leveled, do not find a good gap, the spindle and the motor shaft is not correct, the two shafts are tilted, and so on.
[Edit] Environmental protection on the compressor requirements
[2] With the development of industry accompanied by the generation of pollution of the earth is becoming more and more serious, environmental protection has become an important issue of global concern, and the prevention of atmospheric ozone layer depletion and global warming, but also to cause the world's countries to pay attention to the general, and make the international government to reach a **** knowledge, signed the relevant agreements. Agreement.
And in the field of refrigeration and air-conditioning CFCS and HCFCS on the destruction of the atmospheric ozone layer as well as energy consumption caused by global warming, are compressors in the design of the problem should be highly valued.
It is well known that the choice of refrigerant is one of the many factors affecting the design of compressors that should be given high priority.
In order to develop new compressors using alternative refrigerants, the designer first encountered two problems: first, the compressor must be re-sized its working volume to adapt to the requirements of the pressure of different flow rates; second, the compressor in contact with the refrigerant between the compatibility of various materials, such as synthetic rubber and lubricating oils, must be given to solve.
More than fifty substances have been used as refrigerants in the past. After World War II, except for ammonia in the large cooling capacity range, almost all refrigeration and air-conditioning field is dominated by halogenated hydrocarbons CFCS and HCFCS, the 1974 Montreal Protocol stipulated in the replacement of CFCS has been achieved in the industrialized countries, and the replacement plan of HCFCS will be completed in 2020; and for developing countries, will be 2010 and 2040, respectively, will be discontinued. In the case of developing countries, it will be discontinued in 2010 and 2040, respectively. However, in some developed countries it is intended to be realized earlier. Figure 6 shows the application areas for CFC-11, CFC-12, HCFC-22 and R502, which were formerly used in Europe, and their possible replacement agents (under the arrowed horizontal line).
CFC-11 is a low-pressure refrigerant mainly used in centrifugal chillers, and its transitional replacement is HCFC-123. In addition, HFC-245ca or HFC-245fa is also a low-pressure refrigerant, but it is flammable, so its flame reduction methods and toxicity have yet to be investigated, and it is not as efficiently used as CFC-11 and HCFC-123. It is not as efficient as CFC-11 and HCFC-123. As a result, many enterprises have switched to using HFC-134a in centrifugal chillers.
CFC-12 is the first to be considered for replacement due to its wide range of applications and leakage problems in automobile air conditioning. HFC-134a can be used to replace it in domestic refrigerators and automobile air conditioners. HFC-134a is used in medium and high temperature ranges and has similar cooling capacity and efficiency to CFC-12. However, at operating conditions below -23°C, it loses its attractiveness because its refrigerating capacity and efficiency are lower than those of CFC-12. Although HFC-134a has an ozone depletion potential ODP of zero, it has a global warming potential GWP of up to 1300 (a comparative value based on the GWP of CO2), which also affects its developmental use in the long term.
HCFC-22, which is already widely used in commercial refrigeration and in commercial and residential air conditioning and heat pumps, has an ODP much smaller than that of CFC-11 and CFC-12, at 0.055. But its GWP is quite high, at about 1,700. it is for these reasons that it is already being rapidly phased out in a number of countries in Europe, such as Germany. Several refrigerant blends are already available as alternatives to HCFC-22. The American Refrigeration Association has recommended four kinds of refrigerant substitutes in its Assessment of Refrigerant Substitutes Program (AREP): HFC-134a, R407C, R410A, and R410B. However, HFC-134a is smaller than the other three kinds of refrigerant, its cooling capacity and pressure, and it needs to be redesigned to make the system bigger, so it seems that the possibility of replacing HFCF-22 is minimized, but it is used in the larger cold rooms, and it is not possible to replace HFCF-22. Minimum, but the possibility of using in a larger chiller still exists. Non-***boiling agent R407C is likely to be a "usable" on the existing machine (drop in) alternative agent, because it is most similar to HCFC-22, replacement of the system equipment only need to make minimal changes, and the use of acid lubricants to replace mineral oil, should also pay attention to the adaptability of the agent's larger temperature slip (up to 5 to 7 ℃). ~ 7 ℃). Nearly **** boiling agent R410A and R410B is a mixture of the two same HFCS, the difference is only the mixing ratio only. R410A is suitable for split small air conditioners, but its evaporating pressure is about 1.5 times that of HCFC-22, so the system with this agent needs to be completely redesigned, and therefore is only used in new refrigeration and air conditioning systems. Optimized design of such systems can improve their efficiency by up to 5 percent.
R502 was widely used in low-temperature refrigeration systems, AREP recommended two possible alternatives: R404A and R507. R404A has a similar refrigeration capacity and efficiency to R502, but in the adoption of the system, especially the need for more testing of the components, especially the compressor. It is similar to R502, but toxicity tests continue in the United States; however, in Europe, it has been used in supermarket refrigeration equipment.
There are a large number of "natural refrigerants" in nature, such as ammonia, hydrocarbons, carbon dioxide, etc. Ammonia has been used for more than 100 years. Ammonia has been used for more than a hundred years, and is still used in many countries in large-scale industrial refrigeration, food refrigeration and freezing. However, its flammable, explosive, toxic and has a strong irritating flavor and so on to limit its scope of application.
Hydrocarbons have very good thermal properties and heat transfer characteristics, it and all mechanical materials and oils are fully compatible. And in fact, this kind of work material has long been used in large-scale refrigeration systems in the petrochemical industry. The resistance to the widespread use of this type of refrigerant comes from its flammability. In Europe, this refrigerant has begun to enter the domestic refrigeration equipment market, such as Germany has 90% coverage in the product. China's refrigerator industry has also used isobutane R600a products.
Flammable refrigerant application range and prospects is a very important issue, its universal solution is still need to have a more unified understanding of the international community, because it affects the international trade in refrigeration and air-conditioning equipment. However, to achieve this step is still waiting for more experimental research and policy adopted by countries on this issue, it seems to take quite some time to see the end.
Because of the traditional mineral oils and synthetic oils suitable for CFC-12 and other CFCS substances and new substances such as R134a HFCS poor compatibility, people then research and development of a new type of polar lubricants, the lubricant matrix is a polyester POE (known as ester oils), and there are polyethylene glycol PAG (known as glycol oils), which have a good compatibility with the new HFCS substances, so as to avoid the HFCS new substances have a good compatibility, so that they can be used in the refrigeration and air-conditioning equipment. Good solubility, so as to avoid gathering lubricant in the heat exchanger as well as to ensure that the oil can flow back to the compressor smoothly.
Refrigeration machine Refrigeration machine (refrigeration machine)
A machine that transfers heat from a cooled object with a lower temperature to an ambient medium in order to obtain cold. The heat transferred from the lower temperature object is customarily referred to as cold. Refrigeration machine involved in thermal process changes (energy conversion and heat transfer) of the mass is called refrigerant. The temperature range of refrigeration is usually above 120K, and below 120K is the range of deep cryogenic technology. Refrigerators are widely used in industrial and agricultural production and daily life.
In 1834, the United States of America J. Perkins tried to make a successful human turn with ether as a working material can work continuously refrigerator. 1844, the United States of America J. Gorey tried to use the air as a working material of the refrigeration machine, used in hospitals in the production of ice and cooling air. 1872 ~ 1874, D. Bell and C. von Linde were invented in the United States and Germany ammonia compressor and made the ammonia vapor compression refrigeration. The ammonia vapor compression refrigeration machine, which is the beginning of the modern compression refrigeration machine. 1850s, France's Carré brothers successively developed the sulfuric acid and water as the mass of the absorption refrigeration machine and ammonia absorption refrigeration machine. 1910 appeared in the steam injection refrigeration machine. 1930 appeared in the freon refrigerant, which promotes the rapid development of compression refrigeration. 1945, the United States of America, the successful development of silver bromide absorption refrigeration. developed a successful silver bromide absorption refrigerator.
Based on the principle of operation of the refrigerator can be divided into: ① compression refrigerator. Relying on the role of the compressor to increase the pressure of the refrigerant to achieve the refrigeration cycle, according to the type of refrigerant can be divided into vapor compression refrigeration (based on hydraulic evaporation refrigeration, the refrigerant should be periodic gas - liquid phase change) and gas compression refrigeration (based on high-pressure gas expansion refrigeration, the refrigerant is always in the state of the gas) two kinds. ② Absorption refrigerator. Relying on the absorber - generator group (thermochemical compressor) to complete the refrigeration cycle, can be divided into ammonia absorption, lithium bromide absorption and absorption diffusion of three kinds. (iii) Steam injection refrigerator. Rely on the role of the steam injector (jet compressor) to complete the refrigeration cycle. (iv) Semiconductor cooler. Utilizes the thermal-electrical effect of semiconductors to produce cold.
The main performance indicators of the refrigerator working temperature (for vapor compression refrigerator for the evaporation temperature and condensing temperature, for gas compression refrigerator and semiconductor refrigerator for the temperature of the cold object and the temperature of the cooling medium), refrigeration (refrigerator unit of time from the cooled object to remove the heat), the power or heat consumption, the refrigeration coefficient (measure of the compression refrigeration machine economy of the index, refers to), the cooling capacity (the consumption of unit of work can be obtained by the cooling capacity), power or heat, cooling coefficient (measure of compression refrigeration machine economic indicators, refers to). Consumption of a unit of work can be obtained by the amount of cold) and thermal coefficient (a measure of the economy of absorption and vapor injection refrigeration machine indicators, refers to the consumption of a unit of heat can be obtained by the amount of cold) and so on. Modern refrigerators to vapor compression refrigerators are most widely used.
Refrigeration energy-saving methods
Centrifugal refrigeration energy-saving methods 1. Refrigeration energy-saving principle 1: hair temperature, reduce condensing temperature in order to meet the safety of the equipment and the premise of production demand, try to increase the evaporation temperature and reduce the condensing temperature. To this end, the cooling tower has been increased to ensure the transformation of cooling water efficiency.
2. Prevent and reduce pipeline scaling to improve the heat transfer efficiency of the condenser and evaporator supplemental water if the water treatment is not done properly, calcium bicarbonate and magnesium bicarbonate heat generated by calcium carbonate and magnesium carbonate will be deposited on the pipeline. Make the thermal conductivity decline, affecting the condenser and evaporator heat transfer efficiency, and make the equipment operation electricity costs rise substantially. At this time, in addition to the use of water treatment technology, you can also use the pipeline regular automatic cleaning equipment for pipeline cleaning.
3. Adjustment of refrigeration equipment reasonable operating load
In the case of ensuring the safe operation of equipment, refrigeration host running at 70% -80% load than running at 100% load, the unit of cold power consumption is smaller. The use of this method of power-on should be combined with the operation of the water pump, cooling tower comprehensive consideration.
4. The use of refrigeration machine frequency conversion device, adjust the speed of the centrifugal refrigeration machine compressor low-pressure refrigerant through the centrifuge, the pressure increases. The greater the speed of the centrifuge, the higher the pressure rise. In actual operation, the equipment is mostly running at less than full load. Fixed speed centrifuges cause energy waste when the equipment is running at small loads. The inverter centrifugal refrigeration machine can automatically adjust the compressor speed according to the change of load, energy saving space is relatively large.