Scroll compressor is a kind of positive displacement compressor that compress flow by a spiral scroll eccentrically orbiting in the air end instead rotating like the screw compressor. This special scroll compression has a variety of benefits such as the highest energy and volume efficiency, lowest noise, 100% oil-free compressed air, maintenance-free and long service life. This article will introduce what is scroll compressor and how does it work.
What is a scroll compressor?
Scroll compressor history
The scroll compressor was first invented in 1905 by French engineer Leon Creux, but due to the limitations of processing technology, it was not mass-produced until the early 1980s. Since the 1970s, the intensification of the energy crisis and the emergence of high-precision CNC milling machines have brought opportunities for the development of scroll machinery.
In 1973, the American ADL company first proposed a research report on scroll nitrogen compressors, and proved that scroll compressors have advantages that other compressors cannot match, so the large-scale engineering development and research of scroll compressors have embarked on a rapid development path. In 1982, Japan’s Sanden Company kicked off the mass production of automotive air-conditioning scroll compressors.
In 1983, Hitachi launched the world’s first air conditioner using a fully enclosed scroll compressor. After that, Mitsubishi Electric, Daikin, Panasonic, Ingersoll Rand, Sullair and Gardner Denver in the United States also began mass production of scroll compressors.
Scroll compressor definition
The scroll compressor is an efficient and reliable fluid compression equipment, also known as a vortex air compressor. It is a special positive displacement compressor that introduces the Archimedean spiral line design.
The biggest difference between a scroll air compressor and other compressors is its unique compression component, the scroll compressor consists of two Archimedean spiral scrolls, one of which is fixed and the other is driven by the motor to move in a circular motion, the moving scroll orbits eccentrically but does not rotate.
Scroll compressors may be easily confused with centrifugal compressors, but they are not the same thing. Centrifugal air compressors belong to speed-type air compressors, which are essentially different from the positive displacement air compressor family.
Positive displacement compressors compress air by reducing its capacity, essentially reducing the volume of air, such as scroll compressors, reciprocating piston compressors, and rotary screw compressors; while speed compressors increase the flow rate of air and then convert the kinetic energy of air into air pressure through a diffuser, such as centrifugal compressors and axial flow compressors.
How do scroll compressors work?
Scroll compressor parts
The scroll compressor is mainly composed of two scrolls, spindle, compression chamber, motor and cooling system.
Scrolls: A scroll is a vane with an involute, Archimedean spiral, or hybrid curves. There are two scrolls in a scroll compressor, one of which is fixed and the other is connected to the spindle through an Oldham-type coupling.
Spindle: The spindle is a transmission element with a helical gear, and the spindle is driven to rotate by an motor.
Oldham-type coupling: A gear used in conjunction with the spindle. When the spindle rotates, the Oldham-type coupling meshes with the moving scroll to convert the rotational motion of the spindle into the circular motion of the moving scroll.
Compression chamber: The gap between the two scrolls in the scroll compressor, where air is sucked into the chamber through the air inlet.
Scroll compressor working principle
(Scroll compressor working principle)
(Geometry of Archimedean spiral scrolls)
The working principle of the scroll air compressor is based on the hermetic compressor principle. The motor drives the spindle to rotate. Through the combination of the Oldham-type coupling between the moving scroll and the spindle, the rotational motion of the spindle is converted into the eccentric circular motion of the moving scroll.
When the moving scroll eccentrically orbits, the gap enclosed by air between the moving scroll and the static scroll also moves eccentrically toward the center of the scrolls and its capacity decreases. The air volume decreases, the temperature rises, and the pressure increases, thereby the air is compressed.
Because there is no mechanical friction between the two scrolls, only mutual meshing, the oil-free scroll air compressor does not require lubricating oil in the air end for lubrication and cooling like other positive displacement compressors, thus achieving completely oil-free compressed air.
The design of the scroll provides radial and axial stability for the scroll air compressor, preventing leakage during the compression process, making the scroll air compressor have a high compression efficiency.
The scroll compression is continuous and the torque fluctuation is only 50%, which ensures the constant and pulsation-free air flow, this is one of the reasons why the scroll oil-free air compressor runs very quietly.
Due to its unique working principle, the scroll compressor can produce pure oil-free compressed air. There is no friction between the moving components, so less energy is lost in the process of compressing the gas, so the efficiency is higher. Scroll compressors are also widely used in industry, medical care, pneumatics and other fields because of their high efficiency, reliability, low noise, low vibration, low energy consumption, energy saving and stability.
Scroll compressor working steps
(Scroll compressor working steps)
The working process of the scroll compressor is mainly to make the gas pass through a narrow space under pressure through the eccentric orbiting motion of the scroll, thereby obtaining high pressure. In this process, the gas is compressed.
Inhalation: the moving scroll starts eccentrically orbiting and the air is introduced into the air end compression chamber through the air inlet.
Compression: the scroll continues to orbit and makes the compression chamber go along the spiral line toward the center of the scroll, where compressed air is exhausted. The volume of the compression chamber decreases, the pressure and temperature of the air increase, thereby the air is compressed.
Continuous circulation: the scroll continues to orbit and the outside air is continuously sucked in and transported to the center of the scroll, and the pressure continues to increase.
Exhaust: after the air pressure at the center of the scroll reaches the desired pressure, the exhaust port is opened, and the compressed air is released from the exhaust port, enters the after-cooler and after-treatment equipment for further processing, and is supplied to various applications.
This kind of working procedures enables the scroll air compressor to efficiently generate oil-free compressed air, makes it is particularly suitable for applications with high gas purity requirements.
Scroll compressors advantages
Scroll compressors characteristics
Structure characteristics of scroll compressor
There is only one moving part (the linear speed of the moving scroll is less than 2M/S), and the other parts do not move, so the whole drive vibration is extremely small, and the moving and static scrolls do not contact each other.
Scroll air compressors can achieve very high compression ratios and have high energy conversion efficiency, thereby reducing energy waste.
Scroll air compressors can be divided into two types: high-speed scrolls and low-speed scrolls. High-speed scrolls are suitable for large flow and small pressure ratio occasions, while low-speed scrolls are suitable for small flow and large pressure ratio occasions.
Scroll air compressors can achieve smooth compression and can adapt to a wider range of working variables. It is one of the types of air compressors widely used in industry.
Scroll air compressors can usually provide higher outlet pressures and are suitable for applications that require high-pressure air, such as industrial production, manufacturing, and energy fields.
Benefits of scroll compressors
Oil-free design: Compared with oil-containing air compressors, the oil-free design eliminates the possibility of oil contamination and is suitable for industries with strict requirements on air purity, such as medical and food processing.
Scroll design: The scroll design of the oil-free scroll air compressor enables it to have efficient gas compression capacity, achieve smooth compression, and can adapt to a wider range of working variables, providing stable high-pressure air output.
Low maintenance cost: Since there is no need to use lubricating oil, there is no friction between moving components, which greatly reduces mechanical wear and maintenance costs. This reduces the operating cost of the equipment and reduces the frequency of maintenance work.
Wide application: Oil-free scroll air compressors are widely used in many industries such as manufacturing, medical, and electronics industries to meet the needs of high-quality compressed air for different applications.
Large capacity: scroll air compressors usually have a large capacity and can provide a wide SCFM and CFM range of compressed air. This makes it suitable for applications that require high flow, such as large industrial systems and energy stations.
Low energy consumption: scroll air compressors have lower energy consumption and can provide a large amount of compressed air with less energy. Its design optimizes the internal airflow path, reduces air leakage, pressure loss, and improves energy utilization.
Continuous operation: scroll air compressors are usually designed for continuous operation and can meet the demand for continuous and stable air supply in industrial production.
Ultra-low noise: The noise is lower than any other type of air compressor. Compared with other types of air compressors, scroll air compressors run smoothly, with little vibration and friction-free moving components. They have extremely low noise levels.
If air compressor manufacturers deliberately use sound insulation materials and vibration reduction measures to manufacture scroll air compressors, their noise will be even more negligible, greatly reducing interference with the working environment and operators.
Scroll compressor and screw compressor comparison
| Project | Scroll compressor | Screw compressor |
|---|---|---|
| Noise level | Ultra-quiet, with only one moving part, operating noise can be as low as 53dB(A), no friction in moving parts and little vibration. | Loud noise, many moving parts, severe mechanical friction between the male and female rotors, strong vibration |
| Lubricating method | No need for oil or other lubricants to lubricate the air end, no need to replace lubricating oil and oil filter, no waste liquid drainage problem. | Lubricating oil is necessary for lubricating and cooling the air end. Lubricating oil and oil filter need to be replaced on time. |
| Air purity | 100% oil-free compressed air, eliminating the threat of oil pollution from the source. | Oil particles cannot be completely removed, there is a risk of air and product contamination. |
| Operation stability | Designed for continuous operation, suitable for 0-100% duty cycle. | Has a duty cycle and cannot run continuously for long time work. |
| Service life | Few moving parts and wearing parts, stable operation, slow aging and long service life. | The rotors in the air end are prone to wear and aging, and has many vulnerable parts, which greatly limits its service life. |
| Valve and piping system | No intake valve or exhaust valve, which reduces the resistance of air intake and exhaust and the pressure loss. The piping system is simple and the risk of leakage is reduced. | There are multiple valves in the air piping system, which increases air resistance and pressure loss, and is more prone to air leakage risks. |
| Volumetric efficiency | No clearance volume, nearly 100% volume efficient. | There is gap between the male and female rotors, volumetric efficiency is low. |
| Maintenance | Maintenance-free, just to clean the radiator fan regularly, keep the surrounding environment clean, less component wear, long maintenance cycle, only need 1.5 hours of preventive maintenance per year, including overhaul. | Requires daily cleaning, drainage, inspection and replacement of lubricating oil, oil filters and oil separator elements, may need to remove oil sludge and carbon deposits. |
| Application | Oil-free, compact and relatively quiet, suitable for sensitive working environments (such as dental clinics, etc.) or industrial. | Bulky and noisy, suitable for manufacturing workshops where the compressed air quality is not sensitive. |
| Energy efficiency | The motor only needs to drive the crankshaft and the orbiting scroll, consuming less energy and having high energy efficiency. | It needs to operate two screw rotors, lubricating oil system, and fan system at the same time, with high load and energy consumption, and low energy efficiency. |
| Work efficiency | Archimedean spiral scroll design for dynamic and static scrolls, high working efficiency, can produce more compressed air with less energy consumption. | Archimedean spiral scroll design for dynamic and static scrolls, high working efficiency, can produce more compressed air with less energy consumption. |
| Failure rate | Few moving components, simple and stable operation, less prone to failure. | There are many moving components, and are prone to failure, any problem in any part can easily cause failures or downtime. |
| Running costs | Scroll compressors have low energy consumption, high efficiency, can greatly help saving energy and maintenance costs. | High energy consumption, low efficiency, many wearing parts, easy to fail, high operating and maintenance costs. |
Scroll compressor applications
The applications for oil-free scroll air compressors are very wide. Due to its variety of characteristics, it is ideal for many manufacturing processes where clean, oil-free compressed air is a prerequisite, such as hospitals, laboratories, breweries, bakeries, dairy farms, electronic manufacturing, and even the production of lenses.
Scroll compressors are widely used in various industrial fields, such as compressed natural gas, energy, manufacturing, petrochemicals, electricity, medical, pharmaceuticals, electronic semiconductors, spraying and others.
They are used to provide high-pressure gas to drive pneumatic machinery and equipment, supply factory production lines and other applications that require high-quality compressed air. In the medical field, it can be used as a driving gas supply system for medical equipment such as ventilators, anesthesia machines, and dentists’ air drills.
(Scroll compressor in air conditioning)
Scroll compressor maintenance
The maintenance and care of scroll compressors is very easy. During its entire life cycle, it generally takes only 1.5 hours per year for preventive maintenance, including overhaul.
Daily maintenance mainly includes checking whether components such as filters, radiators and fans are blocked, and their pressure difference; keeping the environment around the scroll compressor clean and ventilated; checking whether there are abnormal sounds during the operation of the machine; checking the intake and exhaust temperature and pressure, etc.
(KUW Series Silent Oil Free Scroll Air Compressor)
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