The crankshaft drives the connecting rod, the connecting rod drives the piston, and the piston moves up and down. Piston movement changes the volume in the cylinder. When the piston moves downward, the cylinder volume increases. The inlet valve opens, the exhaust valve closes, and the air is sucked in to complete the intake process. When the piston moves upward, the cylinder volume decreases, the outlet valve opens, the inlet valve closes, and the compression process is completed. The piston usually has a piston ring to seal the gap between the cylinder and the piston.
A volumetric compressor in which the internal volume of a compression chamber is changed by one or more reciprocating pistons.
At present, reciprocating compressor is mainly piston type air compressor, chemical process compressor, petroleum, natural gas compressor, mainly, and piston type air compressor is mainly to the medium pressure and high pressure direction, this is the screw machine, centrifuge can not reach a height.
Reciprocating gas compressor of characteristics
First, because of the design principle of the relationship, decided the piston compressor many characteristics. For example, there are many moving parts, such as inlet valve, exhaust valve, piston, piston ring, connecting rod, crankshaft, bearing bush; For example, the force is not balanced, there is no way to control the reciprocating inertial force; For example, multi-stage compression is required, and the structure is complex; Another example is due to reciprocating motion, compressed air is not continuous discharge, pulsation, etc.
1. High thermal efficiency and low power consumption per unit
2, convenient processing of low material requirements, low cost
3. The device system is relatively simple
4. Early design, early production and mature manufacturing technology
5. Wide application
1. Many moving parts, complicated structure, large maintenance workload and high maintenance cost
2. Speed is limited
3. The wear of piston ring, cylinder and belt make the efficiency decrease rapidly
4. Loud noise
5, the control system is backward, do not adapt to the need for interlocking control and unattended, so although the price of the piston machine is very low, but also often can not be accepted by the user.
The working process of reciprocating gas compressor
Reciprocating gas compressors have cylinders, pistons and valves. The working process of compressed gas can be divided into expansion, inhalation, compression and exhaust.
Example: the cylinder of a single-suction compressor, in which there is only an suction valve and an exhaust valve in one section of the cylinder, and the piston only sucks in and exhausts once for each reciprocation.
(1) expansion: when the piston moves to the left, the cylinder volume increases, the pressure drops, and the residual air in the cylinder expands continuously.
(2) inhalation: when the pressure drops to a little less than the gas pressure in the inlet pipe, the gas in the inlet pipe pushes the suction valve and enters the cylinder. As the piston moves to the left, the gas continues to enter the cylinder until the piston moves to the left end (also known as the left dead center).
(3) compression: when the piston turns to move to the right, the cylinder volume gradually shrinks, thus beginning the process of compression of the gas. Because the suction valve has a reverse effect, the gas in the cylinder cannot be reversed back into the inlet pipe, and the gas pressure in the outlet pipe is higher than the gas pressure in the cylinder, and the gas in the cylinder cannot run from the exhaust valve to the outside of the cylinder. The gas in the outlet pipe can not flow into the cylinder because of the reverse effect of the discharge valve. Therefore, the amount of gas in the cylinder remains constant because the piston continues to move to the right, reducing the volume of gas in the cylinder and increasing the pressure of the gas.
(4) discharge: as the piston moves to the right, the pressure of compressed gas increases to a little more than the gas pressure in the outlet tube, the gas in the cylinder will be pushed out of the valve spring into the outlet tube, and continue to discharge, until the piston moves to the right end (also known as the right dead center). Then the piston moves to the left again, repeating the motion. Piston in the cylinder constantly reciprocating movement, so that the cylinder reciprocating cycle of inhalation and exhaust gas. Each return of the piston becomes a working cycle, and the distance traveled by each return or return of the piston is called a stroke.