Piston refrigeration compressor
The structure of the piston refrigeration compressor
Piston refrigeration compressor is mainly composed of three parts: working chamber part, machine base part and auxiliary system lubrication, cooling, etc.
The structure of the piston refrigeration compressor: the compressor is mainly composed of body, crankshaft, connecting rod, piston group, valve (valve), shaft seal, oil pump, energy regulating device, oil circulation system and other components.
cBody:
Including two parts, cylinder block and crankcase, generally made of high-strength gray cast iron as a whole.
cylinder:
The cylinder is the main part of the working parts of the piston refrigeration compressor. According to the compressor's different pressure, displacement, gas properties and other needs, different materials and structural types should be selected. The basic requirements are: it should have sufficient strength and rigidity; it should have good cooling, lubrication and wear resistance.
Installation method of cylinder head:
1. From the middle to both sides; 2. Diagonally; 3. Divide two to three times; 4. Tighten according to the specified torque.
Crankshaft:
The crankshaft is one of the main components of the piston refrigeration compressor, which transmits the full power of the compressor. Its main function is to change the rotary motion of the motor into the reciprocating linear motion of the piston through the connecting rod.
link:
The connecting rod is the connecting piece between the crankshaft and the piston, which converts the rotary motion of the crankshaft into the reciprocating motion of the piston, and transmits the power to the piston to perform work on the gas. The connecting rod includes a connecting rod body, a connecting rod small end bushing, a connecting rod big end bearing bush and a connecting rod bolt.
Piston group:
Piston group is the general term for piston, piston pin and piston ring. Driven by the connecting rod, the piston assembly makes a reciprocating linear motion in the cylinder, thereby forming a variable working volume with the cylinder to realize the processes of suction, compression, and exhaust.
Pistons---Pistons can be divided into two categories: cylindrical and disc. The material of the piston is generally aluminum alloy or cast iron.
Piston pin---Piston pin is a part used to connect the piston and the small end of the connecting rod, and bears complex alternating loads during work.
Piston ring --- is a circular ring with an incision on the circumference of the ring. The incision is in the form of straight, oblique, and overlapping. The slope of the bevel is 45 degrees.
The piston ring includes a gas ring and an oil ring. The main function of the steam ring is to form a seal between the piston and the cylinder wall to prevent the compressed air from leaking from the gap between the piston and the cylinder wall; the function of the oil ring is to distribute oil and scrape excess lubricating oil on the cylinder wall.
Shaft seal---The function of the shaft seal is to prevent the compressed gas from leaking out along the extension end of the crankshaft, or to prevent the leakage of outside air when the pressure in the crankcase is lower than the atmospheric pressure.
Crankcase heater:
Separate the refrigerant in the crankcase to ensure the normal lubrication of the compressor. Any environment needs to install a crankcase heater. The crankcase temperature is higher than the ambient temperature by more than 20°C. The compressor is running, the crankshaft heater is powered off, the compressor is stopped, and the heater is powered on.
Protection device of compressor motor:
To prevent the compressor from overloading or overheating, the motor has 6 built-in PTC thermistors. Generally speaking, L and N are power supplies, and 11 and 14 are connected to the control circuit. 12 is an alarm indicator.
Oil pressure safety protection device:
Monitor the pressure difference between the inlet and outlet of the oil pump to ensure compressor lubrication. Generally it is less than 0.7bar, with a delay of 90±10 seconds. The oil pressure difference of the compressor is 2.5~3kg/cm.
The oil pressure difference of a single-stage compressor is: ΔP = oil pump outlet pressure-suction pressure
The oil pressure difference of the two-stage compressor is: ΔP = oil pump outlet pressure-intermediate pressure
Six systems:
(1) Motion system: crankshaft, piston connecting rod assembly, coupling, etc.;
(2) Air distribution system: valve plate, valve spring, etc.;
(3) Sealing system: piston ring, oil seal, gasket, packing, etc.;
(4) Body system: crankcase, cylinder block, cylinder liner, cover plate, etc.;
(5) Lubrication system: lubricating oil pump, oil filter, pressure regulating valve, etc.;
(6) Safety and energy regulation systems: safety valves, energy regulation devices, etc.
Other refrigeration components---oil separator:
Function: Separate the refrigerating oil in the refrigerant on the exhaust pipe to directly enter the crankcase of the compressor, reducing the amount of oil entering the refrigeration system.
Application: refrigeration systems with medium and low temperature ranges and long pipelines (liquid supply pipe, suction pipe).
Note: If the oil return of the system is not good, the refueling separator can only extend the operating time of the compressor and cannot solve the oil return problem of the system.,,,,
If the air-cooled condenser is higher than the compressor, (split unit, the air-cooled condenser is higher than> 1m), a check valve must be installed at the oil separator outlet to prevent the refrigerant from entering the oil separator when the system is shut down. Damage to the compressor.
Other refrigeration components---gas-liquid separator:
Function: Separate the non-evaporated refrigerant liquid in the refrigeration system before the compressor suctions to prevent the compressor from generating wet stroke (liquid hammer).
Application: medium and low temperature conditions.
Other refrigeration components---filter drier:
Function: Absorb and filter the moisture in the liquid refrigerant and filter the dirt and impurities in the refrigerant. It is generally installed at the refrigerant outlet of the accumulator and water-cooled condenser.
Other refrigeration components---solenoid valve:
Function: When the compressor stops running, the solenoid valve is closed to prevent the high pressure refrigerant from entering the low and low pressure system. Prevent liquid shock when the compressor restarts.
Installation position: 100mm～200mm away from the thermal expansion valve
Other refrigeration components---thermal expansion valve:
Function: throttling, reducing pressure. Installation location: The closer to the evaporator, the better.
The main features of piston refrigeration compressors:
advantage:
1) The applicable pressure range is wide, and the required pressure can be reached regardless of the flow rate;
2) High thermal efficiency and low unit power consumption;
3) Strong adaptability, that is, a wide exhaust range, which can adapt to a wide pressure range and cooling capacity requirements;
4) Strong maintainability;
5) Low material requirements, easier processing, and lower cost;
6) The technology is relatively mature and rich experience in production and use has been accumulated;
7) The installation system is relatively simple;
Disadvantages:
1) The speed is not high, the machine is big and heavy;
2) There are many wearing parts and a large amount of maintenance;
3) The exhaust is not continuous, causing air flow pulsation;
4) There is greater vibration during operation. Piston compressors have become the most widely used type and the largest production batch of refrigerators in various applications, especially in the small and medium refrigeration range.
