One article to understand what is a piston compressor Piston compressor is a compressor that relies on live cold reciprocating motion to pressurize gas and deliver gas. It belongs to positive displacement compressor, also known as "reciprocating piston compressor" or "reciprocating compressor". It is mainly composed of working cavity, transmission parts, fuselage and auxiliary parts. The working chamber is directly used to compress gas, and is composed of cylinder, cylinder liner, gas valve, packing, piston and piston rod. The piston is driven by the piston rod to reciprocate in the cylinder. The volume of the working chamber on both sides of the piston changes in turn. The gas on the side with reduced volume is discharged through the gas valve due to the increased pressure, and the side with increased volume is passed through the gas due to the decrease in air pressure. The valve sucks in gas, and the transmission parts are used to realize reciprocating motion. There are crank sleeve connecting rod, eccentric slider, swash plate, etc. Among them, the crankshaft connecting rod mechanism is most commonly used. It consists of a crosshead, connecting rod and crankshaft. The work of the piston compressor is completed by the working volume composed of the cylinder, the air valve and the piston reciprocating in the cylinder. If the volume loss and energy loss of the actual operation of the piston compressor are not considered (ie the ideal working process), the work completed by the piston compressor crankshaft every revolution can be divided into suction, compression and exhaust processes Composition structure Piston compressor is mainly composed of body, crankshaft, connecting rod, piston group, valve, shaft seal, oil pump, energy adjustment device, oil circulation system and other components.
1. Body: It includes two parts, the cylinder body and the crankcase, which are generally cast into a whole with high-strength gray cast iron. It is the body that supports the weight of the cylinder liner, crankshaft connecting rod mechanism and all other components and ensures the correct relative position between the components. The cylinder adopts the cylinder liner structure and is installed in the cylinder sleeve seat hole on the cylinder block, which is convenient for maintenance or replacement when the cylinder liner is worn. Therefore, the structure is simple and maintenance is convenient. 2. Crankshaft: The crankshaft is one of the main components of the piston refrigeration compressor, which transfers the full power of the compressor. Its main function is to change the rotary motion of the motor to the reciprocating linear motion of the piston through the connecting rod. When the crankshaft is in motion, it bears an alternating composite load of tension, compression, shear, bending and torsion. The working conditions are harsh, requiring sufficient strength and rigidity, and the wear resistance of the main journal and the crankpin. Therefore, the crankshaft is generally forged with high-quality carbon steel No. 40, 45 or 50, but it has been widely cast using nodular cast iron. 3. Connecting rod: The connecting rod is the connecting piece between the crankshaft and the piston. It converts the rotary motion of the crankshaft into the reciprocating motion of the piston, and transmits power to the piston to do work on the steam. The connecting rod includes a connecting rod body, a small connecting rod bushing, a large connecting rod bearing bush and a connecting rod bolt. 4. Connecting rod: The connecting rod is the connecting piece between the crankshaft and the piston. It converts the rotary motion of the crankshaft into the reciprocating motion of the piston, and transmits power to the piston to do work on the steam. The connecting rod includes a connecting rod body, a small connecting rod bushing, a large connecting rod bearing bush and a connecting rod bolt. 5. Steam valve: The steam valve is an important component of the compressor and is a wearing part. Its quality and the quality of its work directly affect the compressor's steam delivery, power loss and operational reliability. The steam valve includes an intake valve and an exhaust valve. The piston reciprocates up and down once, and the intake and exhaust valves are opened and closed once to control the compressor and complete the four working processes of intake, compression, and exhaust. 6. Shaft seal: The role of the shaft seal is to prevent refrigerant vapor from leaking out along the extended end of the crankshaft, or to prevent outside air from leaking when the pressure in the crankcase is lower than atmospheric pressure. Therefore, the shaft seal should have good sealing, safety and reliability, simple structure, easy assembly and disassembly, and have a certain service life. 7.Energy adjustment device: In the refrigeration system, as the heat load of the cold room changes, its cooling consumption also changes, so the cooling capacity of the compressor should also be adjusted as necessary. The adjustment of the cooling capacity of the compressor is realized by an energy adjustment device. The so-called energy adjustment device of the compressor is actually an exhaust gas adjustment device. It has two functions, one is to realize the no-load start of the compressor or start under a small load state, and the other is to adjust the cooling capacity of the compressor. working principle
Compression process: The piston moves upward from the bottom dead center, the suction and exhaust valves are closed, and the gas is compressed in the closed cylinder. As the cylinder volume gradually decreases, the pressure and temperature gradually increase until the gas pressure and exhaust in the cylinder The pressure is equal. The compression process is generally regarded as an isentropic process. Exhaust process: The piston continues to move upwards, so that the gas pressure in the cylinder is greater than the exhaust pressure, the exhaust valve opens, and the gas in the cylinder is pushed out of the cylinder by the piston to enter the exhaust pipe at equal pressure until the piston moves to the top stop point. At this time, due to the spring force of the exhaust valve and the gravity of the valve disc itself, the exhaust valve is closed and the exhaust is ended.
