Principles and structures of vortex machines, piston machines, screw machines, and centrifuges

     Principles and structures of vortex machines, piston machines, screw machines, and centrifuges

1、 Vortex compressor

Principle: The vortex lines of the moving and stationary disks are the same, but they mesh with a phase difference of 180 degrees, forming a series of enclosed spaces; The stationary disk remains stationary, while the moving disk revolves around the center of the stationary disk and rotates around an eccentric radius. When the moving disk rotates, it meshes sequentially, causing the crescent shaped area to continuously compress and decrease, thereby continuously compressing the gas and finally discharging it from the center hole of the stationary disk. It consists of a moving disc (vortex rotor), a stationary disc (vortex stator), a bracket, a cross coupling ring, a back pressure chamber, an eccentric shaft, etc.

Advantages of vortex compressors:

1. The eccentric shaft that drives the motion of the vortex plate can rotate at high speed, and the vortex compressor has a small volume and light weight;

2. The force variation of moving components such as the vortex disc and spindle is small, resulting in low overall vibration of the machine;

3. Adapted to variable speed motion and variable frequency speed regulation technology;

4. The overall noise of the vortex compressor is very low;

5. The vortex compressor has reliable and effective sealing performance, and its cooling coefficient does not decrease with increasing operating time, but slightly increases;

6. The vortex compressor has good working characteristics. In heat pump air conditioning systems, it is particularly characterized by high heating performance, good stability, and high safety;

7. The scroll compressor has no clearance volume and can maintain high volumetric efficiency operation;

8. Small torque variation, high balance, low vibration, smooth operation, making operation simple and easy to achieve automation;

2、 Screw compressor

Principle: Through the mutual immersion of the yin and yang rotors, as well as the continuous movement of the spatial contact line from the suction end face to the exhaust end face, the basic volume undergoes periodic changes, thus completing the continuous suction pressure transmission and exhaust process. Composed of casing, screw (or rotor), bearings, energy regulating device, etc.

Advantages of screw compressors:

1. Few components, fewer vulnerable parts, and high reliability;

2. Easy operation and maintenance;

3. There is no unbalanced inertial force. Smooth and safe operation with low vibration;

4. It has the characteristic of forced gas transmission, and the exhaust volume is almost not affected by exhaust pressure, with strong adaptability to working conditions;

5. The rotor tooth surface of a screw compressor actually has gaps. Therefore, it is not sensitive to wet stroke and can withstand liquid impact;

6. The exhaust temperature is low and can operate under higher pressure ratios;

7. It can achieve stepless adjustment of refrigeration conditions by using a slide valve mechanism, allowing for stepless adjustment of refrigeration capacity from 15% to 100%, saving operating costs;

8. Easy to achieve automation and enable remote communication.

3、 Piston compressor

Principle: Relying on the reciprocating motion of the piston to compress the gas inside the cylinder. Usually, the rotational motion of the prime mover is transformed into the reciprocating motion of the piston through a crank connecting rod mechanism. The work completed by each revolution of the crankshaft can be divided into the suction process and the compression exhaust process. Including the body, crankshaft, connecting rod components, piston components, air valve cylinder liner components, etc.

Advantages of piston compressors:

1. Within the general pressure range, the material requirements are low, and ordinary steel materials are often used, making processing easier and the cost lower;

2. The thermal efficiency is relatively high, and the insulation efficiency of large and medium-sized units can generally reach around 0.7~0.85;

3. The density and characteristics of gases have little impact on the working performance of compressors, and the same compressor can be used for different gases;

4. The piston compressor technology is relatively mature and has accumulated rich experience in production and use;

5. When adjusting the gas volume, it has strong adaptability, that is, it has a wide exhaust range and is not affected by high or low pressure, and can adapt to a wide pressure range and refrigeration capacity requirements;

4、 Centrifugal compressor

Principle: When the compressor impeller rotates, refrigerant vapor enters the impeller passage through the inlet guide vanes from the suction chamber, and the gas rotates with the impeller under the push of the vanes. Due to the centrifugal force, gas flows radially along the impeller channel and leaves the impeller. A single-stage compressor mainly consists of an suction chamber, impeller (working wheel), pressure regulator, volute chamber (volute), and seal. For multi-stage compression, there are also components such as bends and reflux devices.

Advantages of centrifugal compressors:

1. Centrifugal compressors have a large air volume, simple and compact structure, light weight, small unit size, and small footprint. Compared to piston compressors, they are 5-8 times lighter in weight when the refrigeration capacity is the same.

2. Due to the lack of vulnerable components such as steam valves and piston rings, as well as the absence of crank and connecting rod mechanisms, it operates in a balanced and reliable manner, with a high operating rate and fewer friction parts. As a result, it requires fewer spare parts, maintenance costs, and personnel.

3. There is no friction between the working wheel and the casing, and no lubrication is required. In chemical processes, centrifugal compressors can achieve an absolutely oil-free compression process for chemical media.

4. A centrifugal compressor is a rotating machine that is suitable for direct driving of industrial or gas turbines. For general large chemical plants, by-product steam is commonly used to drive industrial steam turbines as power, providing the possibility for comprehensive utilization of thermal energy.