Piston Compressor Basics – Structure, Functional Foundation, Benefits and Problems

As both manufacturers and end consumers know, in the refrigerator or cooling system, the compressor is the backbone of the machine for continuous ******* back and forward refrigeration When the compressor breaks or stops working, the entire cooling system will be disrupted.

The piston compressor is widely used for high and medium cold storage. Here we will explain in detail the structure, operating principle, good and bad as well as the common error detection of piston compressors.

Structure of Piston Compressor
The following is a detailed description of the main parts of a piston compressor.

1.1 Body

The body of the compressor includes a cylinder block and a crankcase. Generally, it is made of high strength of iron gray.

1.2 Cylinder

The cylinder is a key feature of the piston compressor. Depending on the different pressure, discharge power and gas compressor properties, users should choose cylinders made of different materials and suitable structures.

The basic requirements of the cylinders are: durability and durability, good cooling, flexibility and durability of the coating.

1.3 Crankshaft

By altering the rotational motion of the motor to reverse the direct movement of the piston with the connecting rod, the crankshaft transmits the full power of the compressor. It is one of the most important components of a compressor movement system.

1.4 Connect the rod

The connecting rod is a connecting piece between the crankshaft and the piston, which converts the movement of the crankshaft into a repetitive motion of the piston, and transfers power to the piston for gas processing.

The connecting rod consists of a connecting rod, a small end tree, a large end bearing the tree and a bolt.

1.5 Piston Group

Piston Group is the common name for a piston, including piston pin and piston ring. Driven by the connecting rod, the piston group performs the repetition of the corresponding movements in the cylinder, in order to create a flexible working volume and cylinder, thus completing the suction, compression and extraction process.

1.6 Piston

The piston can be divided into cylinder and disc. Piston materials are usually aluminum alloy or cast iron.

1.7 Piston Deputy

The piston pin is used to connect the small end of the piston to the connecting rod. It carries a complex exchange load when operating.

1.8 Piston ring

It is a circular ring on which to cut, and the cut may be straight, sloping or straight. The angle of inclination is 45 degrees.

The piston ring is made up of a gas ring and an oil ring. The gas ring acts as a signal between the piston and the cylinder wall to prevent compressed air from leaking into the space between the piston and the cylinder wall. The oil ring distributes the oil and removes excess oil from the wall of the cylinder.

1.9 Shaft Seal

The shaft seal is for preventing compressed gas from escaping the extended edges of the crankshaft, as well as for preventing outside air from entering when the pressure on the head credit is lower than atmospheric pressure.

1.10 Crankcase Heater

The crankcase heater ensures the normal cooling of the refrigerator heater on the crankcase by separating the refrigerator from the crankcase.

Users should install a crankcase heater anywhere. When the compressor operates at a crankcase temperature of 20 case higher than the ambient temperature, the crankshaft heater will be turned off. When the compressor stops, the heater will turn on.

1.11 Vehicle Protection Converter

To prevent overheating or overheating of the compressor, the car is built-in with 6 PTC thermistors. Generally, L, N is the power supply, 11, 14 are connected to the control circuit, and 12 is the alarm indicator.

1.12 Oil Pressure Safety Device

The oil pressure protection device monitors the pressure difference between the inlet and out of the oil pump to ensure compression of the compressor. The frequency is below the 0.7 bar and is delayed by 90 ± 10 seconds. The oil pressure difference of the compressor is 2.5 ~ 3 kg / cm.

The oil pressure difference of a single phase compressor is calculated as:

= P = Oil Outflow Pressure – Suck Pressure.

The oil pressure difference of a two-phase compressor is calculated as:

= P = Oil Outflow Pressure – Medium Pressure.

Piston Compressor operating system
The function of the piston compressor is completed by the continuous change of the active volume made of the cylinder, the air valve and the recurring cylinder piston.

If the volume loss and power loss in the actual function of the piston compressor are not considered (i.e., during the proper operation process), the work completed by the crankshaft of the piston compressor can be divided into four processes: compression, extraction, expansion and drag.

2.1 Concentration Process

When the piston is at the lowest point (called the inner center dead or the lower dead center), the cylinder is filled with low-level refrigerator smoke inhaled from the evaporator, and the suction process ends.

Driven by a crankshaft and connecting rod, the piston begins to rise to the top. During this time, the suction valve is closed, the operating volume of the cylinder gradually decreases, the gas in the cylinder is compressed, and the temperature and pressure are gradually increased. The process of gas rising from low suction pressure to exhaust pressure on the cylinder is called the compression process.

The compaction process is generally considered an isentropic process.

2.2 Release Process

The piston continues to rise when the gas pressure in the cylinder rises slightly above the gas pressure in the discharge chamber.

When the discharge valve is opened, high pressure steam in the cylinder is released outside the cylinder under constant pressure until the piston reaches

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