Compressor two stage compression is divided into low level compression and high grade compression

When the single compression can not reach the required temperature, then two-stage compression or multi-stage compression is required, which avoids the harm caused by excessive compression ratio and high exhaust temperature,—— which may worsen the operating conditions of the compressor and endanger the life of the compressor. Therefore, when the temperature requirement is too low, you can choose two-stage compression or multi-stage compression, and two-stage compression is common.

This is also known as segmented compression, primary compression, and secondary compression.

The so-called two-stage compression refrigeration cycle is the process of increasing the refrigerant gas from evaporation pressure to condensing pressure in two stages:

The gas at the intermediate pressure is first compressed from the low-pressure stage to the intermediate pressure, and then the gas at the intermediate pressure is further compressed to the high-pressure stage after intermediate cooling.

Refrigeration cycle of condensing pressure.

The reason for the use of two-stage compression is that the condensing temperature of the vapor compression refrigeration cycle is limited by the environmental conditions and is cooled at room temperature.

, the low temperature that can be obtained with a single-stage compression refrigeration cycle is limited. The constraints are the compression ratio and exhaust gas of the unit.

Temperature. If the system is operated at a hypercompression ratio in order to obtain lower temperatures, the actual compression process will deviate more from isentropy.

During the compression process, the discharge temperature of the compressor rises, the efficiency decreases, and the power consumption increases. and even refrigerants and lubricants in the system.

Decomposition, deterioration of operating conditions and endangering the normal operation of the compressor. Therefore, hierarchical compression is implemented to avoid excessive compression ratios.

The harm caused by the excessively high exhaust temperature, to obtain a lower evaporation temperature.

At present, there are two kinds of single-stage compression and two-stage compression in the oil-injected screw air compressor with an exhaust pressure of less than 13bar on the market. In this paper, we will analyze and compare the compression efficiency and energy saving of the two.

According to the theory of engineering thermodynamics, the air compressor is the most energy-saving in the compression process at constant temperature, the area 0-1-2t-3-0 is the work required for constant temperature compression, and the area 0-1-2m-3-0 is the work required for variable compression (the actual compression process). The work required for constant temperature compression is less than the work required for variable compression. Therefore, from the point of view of work consumption, constant temperature compression is the most advantageous.

It can not only reduce the work consumed, but also reduce the temperature of the compressed gas, so that the use of air compressor materials is wider and more economical, and the operation of the air compressor is more reliable.

However, for constant temperature compression, it is impossible to make the gas heat exchange with the outside world at any time, and the gas temperature is equal to the outside world in practical work. This is just the direction that manufacturers strive to work in product design and production. In order to reduce the compressed gas temperature and improve the efficiency of the air compressor, as close as possible to the constant temperature compression process (or reduce the variable index m value), the manufacturer has taken a variety of measures in the air compressor design process.

Among them, staged compression plus intermediate cooling and oil injection cooling into the compression chamber are the two most commonly used methods.

1. Graded compression plus intermediate cooling.

Staged compression plus intercoolant is an effective method to reduce the exhaust temperature in air compressors. Moreover, after graded compression, it must be cooled intercooling, so that the inlet temperature of the compressed air entering the second stage is equal to or close to the inlet temperature of the first stage, so as to reduce the exhaust temperature and power consumption. As shown in Figure 2, since the secondary inlet air temperature is cooled to the primary inlet air temperature, the area of the shaded part of the diagram is the power consumption saved.

The more stages and intercooling processes there are, the closer you are to the constant temperature process. However, too much grading will increase the flow resistance of the gas, and the manufacturing cost will also increase significantly. Therefore, the grading must be reasonable.

2. Inject oil into the compression chamber for cooling.

A small amount of circulating cooling oil is sprayed into a mist and enters the compression chamber with gas, and the injected oil mist absorbs a large amount of heat generated by the compressed air during the compression process, and then discharges the air compressor shell together with the air, and is recycled after being separated by the oil-gas separator. The oil-injected screw air compressor is the most typical application example of this method. It is very effective in reducing the exhaust temperature and the variable index m-value.

This is also the most effective way to reduce the exhaust temperature and variable index m of the air compressor, which can generally reduce the m to the following. The degree of reduction depends on the amount of fuel injected and the injection temperature.

Primary compression generally refers to a compressor with a lower pressure level, and secondary compression is generally a compressor with a relatively high pressure, and the air of secondary compression is better than that of primary compressed gas.

There is a two-stage compression composed of a low-pressure stage and a high-pressure stage in the machine. According to the displacement of the compressor, the low pressure stage accounts for about 70% and the high pressure stage accounts for about 30%, forming a 3:1 or 2:1 exhaust ratio.

First, the low-pressure stage is sucked and compressed from the evaporator to the intermediate pressure and discharged into the intercooler (intercooler), which is cooled by the throttled liquid fluorine, and then the high-pressure stage is sucked from the intercooler and compressed to the condensing pressure (high-pressure pressure) and discharged into the condenser for cooling. This is its compression principle (process), CCTV advertising animation can be clearly seen, there is a small cylinder on both sides of the compressor, and the large one on the left is a low-pressure suction separation cylinder; The small one on the right is the high-pressure intercooler (cylinder), which feeds air into the compressor on both sides during operation.

The biggest feature (advantage) is that it overcomes the disadvantages of the traditional one-virtual pure compression compression that the compression ratio is too large, and the operation in hot and cold temperatures does not respect normal, or even cannot operate. Two-stage compression can both overcome and change this shortcoming.

Because the two-stage compression gas production pressure is high, the two-stage compression has a long service life under the same pressure as the first-stage compression; The energy consumption of two-stage compression is higher at the same pressure and the same gas production, but the wear is small. The two-stage stage is suitable for high pressure production, and the first stage is suitable for large gas production.

Air compressor (referred to as air compressor).

Air compressor is the basic product of industrial modernization, and it is often said that electrical and automation has the meaning of full pneumatic; The air compressor is to provide air source power, is the core equipment of the pneumatic system electromechanical air source device in the main body, it is the original mover (usually the motor) of the mechanical energy into gas pressure energy of the device, is the compressed air pressure generation device.

Power saving: multi-stage compression, through the method of setting an intercooler between stages, the compressed gas is first isobarically cooled after the first stage compression, so as to reduce the temperature, and then enter the next stage cylinder. The temperature decreases and the density increases, which makes it easy to compress further, which can greatly save power consumption compared to primary compression.

Therefore, under the same pressure, the area of work done by multi-stage compression is less than that of single-stage compression, and the more stages there are, the more power consumption is saved, and the closer it is to isothermal compression.

Improve volume utilization.

Reduce the exhaust temperature.

Reduces the gas forces acting on the piston rod.

The two stages are suitable for high pressure, and the first stage is suitable for atmospheric volume.

Single-stage compressor means that the refrigerant enters the compressor cylinder and the compressor is discharged into a high-temperature and high-pressure gas;

The multi-stage compressor is that the refrigerant enters the first cylinder of the compressor for a compressor, and then enters the second cylinder for secondary compression. Multi-stage is to enter multiple cylinders for compression.

It can be simply understood as the difference between a single compressor and multiple compression. Multi-stage compression is better than single-stage compression refrigeration.

Single-stage compression is a compression, and double-stage compression is when the gas of the first stage of compression enters the second stage of pressurization.

Single-stage compression is a pair of rotors, and two-stage is two pairs of rotors.

In the two-stage compression refrigeration cycle, the compression process of the refrigerant is carried out in two stages, that is, the low-pressure refrigerant vapor (pressure p0) from the evaporator first enters the low-pressure compressor, where it is compressed to the intermediate pressure pm, and then enters the high-pressure compressor after intermediate cooling, compresses it to the condensing pressure pk, and discharges it into the condenser. In this way, the pressure ratio of all levels can be moderate, and the power consumption of the compressor can be reduced due to the intercooling, and the reliability and economy have been improved.

When the evaporation temperature is low, the two-stage compression refrigeration cycle can achieve the following purposes:

Reduce the pressure ratio to avoid and reduce the loss caused by the high pressure ratio.

For example, reducing the discharge temperature of the compressor, increasing the actual gas transmission capacity, and improving the balance of the refrigerator operation.

The traditional air conditioner can only achieve heating in the environment of minus 7 degrees Celsius, while the two-stage inverter air conditioner using the two-stage inverter compressor can achieve strong heating under the extreme working conditions of minus 30, rapid cooling in the high-temperature environment of 54, the heating capacity in winter is increased by more than 40%, and the cooling capacity in summer is increased by more than 35%, and the minimum power is only 15 watts, which solves the problem of low temperature heating and poor high temperature refrigeration effect, expands the new blue ocean of air conditioning use area, and refreshes the new record of air conditioning use temperature.

Two-stage inverter, as the name suggests, means that the refrigerant vapor from the evaporator is compressed twice by a low-pressure and high-pressure compressor (or cylinder) before entering the condenser. The main difference between it and the single-stage compression refrigeration cycle process is that most of the refrigerant must be compressed in two cylinders, the high and low pressure stages, and generally an intercooler and expansion valve are added.

The schematic diagram of two-stage variable frequency compression refrigeration is as follows:

It is equivalent to two first-stage compressors in series, but the interstage needs to be cooled.

The low barrel or ammonia is divided into the first stage of inhalation, the first stage of exhaust into intercooling, the outlet of intercoolant into the second stage of inhalation, and the second stage of exhaust into the oil fraction

Two-stage compression is to divide the compression process into two phases, the system will compress the low-pressure refrigerant vapor from the evaporator pressure PE to the intermediate pressure of PM with a low-pressure compressor first, and then compress it with a high-pressure compressor to the condensation temperature of PC. The use of two-stage compressor can reduce the discharge temperature of the compressor, reduce the pressure ratio, reduce the loss of superheat and the total power consumption of the compressor.

The reasons why the air compressor needs two-stage compression are as follows:

1. The two-stage compression gas production pressure is high, and the two-stage compression has a long service life under the same spring pressure as the first-stage compression.

2. The energy consumption of two-stage compression under the same pressure and the same gas production is high, but the wear is small.

3. The two-stage stage is suitable for high pressure production, and the first stage is suitable for large gas production.

Air compressor is the basic product of industrial modernization, Chang Pei Nai said that Li Qing's electrical and automation has the meaning of full pneumatic, and the air compressor is to provide air source power, is the core equipment of the pneumatic system in the electromechanical air source device, it is the original mechanical energy into gas pressure energy of the device, is the compressed air pressure generation device.

The reason why the air compressor needs two-stage compression is as follows:

1. The two-stage compression gas production pressure is high, and the two-stage compression has a long service life under the same pressure compared with the first-stage compression.

2. The energy consumption of two-stage compression under the same pressure and the same production capacity is high, but the wear is small.

3. The two-stage stage is suitable for high pressure production, and the first stage is suitable for large gas production.

Air compressor is the basic product of the modernization of Gongxiang shed industry, often said that electrical and automation has the meaning of full pneumatic, and air compressor is to provide air source power, is the core equipment of the pneumatic system in the electromechanical air source device, it is the original mechanical energy into gas pressure energy of the device, is the compressed air pressure generation device.