supermarket refrigerated showcase » article > commercial refrigeration > Commercial refrigeration reciprocating piston compressor, refrigerated showcase commercial refrigeration tells you
Commercial refrigeration reciprocating piston compressor, refrigerated showcase commercial refrigeration tells you
author: supermarket refrigerated showcase category: commercial refrigeration Views: 597Time: 2016-08-22
commercial refrigeration reciprocating piston compressor is through a certain transmission mechanism, the rotation of the motor into the reciprocating motion of the compressor piston, relying on the piston in the cylinder The variable working volume formed by linear reciprocating motion back and forth is used to complete the compression and delivery of gas. The reciprocating motion mechanism of a reciprocating piston compressor has three common structures: crankshaft connecting rod piston type, crank connecting rod piston type and crank sliding tube type.
(1) commercial refrigeration The working process of a reciprocating piston compressor is through the four processes of compression, exhaust, expansion and suction, completing a suction and exhaust cycle. The working process of a reciprocating piston compressor.
a. Compression process
When the cylinder is filled with low-compression steam, the piston starts to move up from bottom dead center. The cylinder volume gradually decreases, the vapor in the cylinder is scooped to compression, and the pressure and temperature rise accordingly. The suction valve plate is closed due to the higher vapor pressure, while the exhaust valve plate does not exceed the vapor pressure at this time. The exhaust chamber pressure continues to maintain its closed state, so that the vapor compression process will continue until the piston rises until the vapor pressure in the cylinder begins to equal the exhaust chamber pressure.
b. Exhaust process
The piston continues to move upwards, and the compressed vapor pressure will be higher than the exhaust chamber pressure. When the vapor pressure is slightly higher than the gravity and spring force of the exhaust valve plate, the exhaust valve plate is pushed open. As a result, the high-temperature and high-pressure steam in the cylinder begins to be pushed out by the upper selection piston and enters the exhaust chamber. The exhaust process does not end until the piston moves up to the top dead center. When the piston is at the dead center position, in order to prevent the piston from colliding with the valve plate,There must be a certain gap between the top surface of the plug and the surface of the valve plate, and the linear distance is called the linear clearance. The space contained between the top surface of the piston and the bottom surface of the valve plate (including the volume of the exhaust valve hole, etc.) is called the clearance volume. The clearance volume is unavoidable.
At the end of the exhaust process, there is still a small amount of vapor remaining in the clearance volume that cannot be discharged, and its pressure and exhaust chamber pressure are still left in the clearance volume at the end of the exhaust process. The pressure in the air cavity of the forced-pressure blade number is equal. At this time, the exhaust valve plate falls again under the action of its own gravity and spring force, the valve port is covered, and the exhaust valve plate is closed.
c. Expansion process
The piston starts to move down from the top dead center, the cylinder volume gradually increases, and the vapor remaining in the clearance volume will expand. Its pressure and temperature also drop, until the vapor pressure is reduced to equal to the pressure of the suction chamber, the expansion process is considered to be over. During this period, the suction and exhaust valves are closed.
d. Inspiration process
The piston continues to move down, and the vapor pressure in the cylinder begins to be lower than the pressure in the suction chamber. When the pressure difference is sufficient to push the suction valve, the suction process starts until the piston moves to the bottom stop The inhalation process ends when you click.
It can be seen from the above that every time the piston reciprocates in the middle of the cylinder, it is equivalent to each revolution of the crankshaft, a compression, exhaust, expansion and suction process must be performed in sequence. The compressor runs continuously under the drive of the electric motor, and the piston constantly reciprocates in the cylinder. Therefore, the compressor continuously performs the above-mentioned four processes in a cycle to achieve the purpose of continuous compression, discharge, expansion, and suction, and complete the work of gas compression and delivery.
(2) Crankshaft connecting rod piston type fully enclosed compressor. The movement of the piston is driven by the crankshaft and the connecting rod. The connecting rod is the connection between the piston and the crankshaft, which converts the rotational movement of the crankshaft into the reciprocating movement of the piston. The crankshaft is an important part of the compressor, and the compressor's power is input by it, so it requires sufficient strength, rigidity and wear resistance. In this structure, the piston face is uniformly stressed, so the wear is small and the life is long. However, the processing accuracy is high and the process is complicated. This structure is suitable for compressor units with various output powers.
(3) Crank connecting rod piston type hermetic compressor. The structure of the crank connecting rod piston type fully enclosed compressor is basically the same as that of the crank connecting rod type, except that the main shaft is in the shape of an inner handle and the e-axis is supported by a single arm, so the bearing capacity is relatively small. It is only suitable for compressor units with an output power below 300W.
nDue to the reasonable structure of the crank connecting rod piston compressor, the main moving parts are uniformly stressed, and the wear, vibration and noise are small, and the service life is long. It is currently widely used in refrigerators. Beijing and Guangzhou imported from abroad commercial refrigeration compressor manufacturing technology is the production of connecting rod compressors.
(4) Crank sliding tube type hermetic compressor. Crank sliding tube compressor is a compressor of about 100W widely used in commercial refrigeration, which will be introduced here. I have a relatively systematic understanding of sliding tube compressors, and I can also understand connecting rod compressors. The structure of the crank sliding tube compressor in commercial refrigeration.
The sliding tube compressor in commercial refrigeration is mainly composed of a motor, a frame, a slider, a crankshaft, a cylinder block, a valve seat, a valve plate, and a sliding tube piston integrated with a sliding tube. Use sliding pipes and sliders to replace traditional connecting rod assemblies. The slider in the piston slide tube is moved by the crankshaft. When the crankshaft rotates, the slider rotates around the center of the main shaft. At the same time, it reciprocates in the slide tube and drives the piston to reciprocate in the vertical direction. Repeated cycles to complete the gas compression and delivery.
commercial refrigeration crank sliding tube compressors are characterized by simple structure, few parts, less strict requirements on shape and position deviation, simple process, and the cylinder block and frame are not integrated, and the clearance volume can be adjusted freely. However, there is only one supporting bearing, the crankshaft is not stressed, the power performance is poor, the lateral partial pressure of the piston against the cylinder wall is large during operation, and the dynamic balance is poor. For this reason, the center of the spindle must be offset from the center of the cylinder by an appropriate distance. The greater the piston stroke, the greater the lateral partial pressure, which is prone to unilateral wear. Therefore, compressors with a power exceeding 250W do not adopt a sliding tube structure. Sliding tube compressors are all single-phase.
is now unilateral wear. Therefore, compressors with a power exceeding 250W do not adopt a sliding tube structure. The sliding tube compressors in commercial refrigeration all use a single-phase two-stage motor, which is installed under the compression mechanism. The compressor and the motor are supported in the casing with 3 springs, which are integral internal suspension (support) type, reducing The vibration effect is better, and the vibration and noise are small.
The above information is edited by refrigerated showcase commercial refrigeration. For more information, please visit www.ihdjx.com
keywords：