Jun. 23, 2025
Automobiles & Motorcycles
A scroll compressor (also called spiral compressor, scroll pump and scroll vacuum pump) is a device for compressing air or refrigerant.[1] It is used in air conditioning equipment, as an automobile supercharger (where it is known as a scroll-type supercharger) and as a vacuum pump. Many residential central heat pump and air conditioning systems and a few automotive air conditioning systems employ a scroll compressor instead of the more traditional rotary, reciprocating, and wobble-plate compressors.
A scroll compressor operating in reverse is a scroll expander, and can generate mechanical work.
Léon Creux first patented a scroll compressor in in France and the US.[2] Creux invented the compressor as a rotary steam engine concept, but the metal casting technology of the period was not sufficiently advanced to construct a working prototype, since a scroll compressor demands very tight tolerances to function effectively. In the patent, Creux defines a co-orbiting or spinning reversible steam expander driven by a fixed radius crank on a single shaft.[3] However, the scroll expander engine could not overcome the machining hurdles of radial compliance inherent to achieving efficiency in scroll operation that would not be adequately addressed until the works of Niels Young in .[4] The first practical scroll compressors did not appear on the market until after World War II, when higher-precision machine tools enabled their construction. In , Sanden began manufacturing the first commercially available scroll compressors for automobile air conditioners.[1][5] They were not commercially produced for room air conditioning until when Hitachi launched the world's first air conditioner with a hermetic scroll compressor.[6][7]
A scroll compressor uses two interleaving scrolls to pump, compress or pressurize fluids such as liquids and gases. The vane geometry may be involute, Archimedean spiral, or hybrid curves.[8][9][10][11][12]
Often, one of the scrolls is fixed, while the other orbits eccentrically without rotating, thereby trapping and pumping or compressing pockets of fluid between the scrolls. An eccentric shaft can provide the orbital motion but the scroll must be prevented from rotating, typically with an Oldham-type coupling, additional eccentric idler shafts, or a bellows joint (particularly for high-purity applications). Another method for producing the compression motion is co-rotating the scrolls, in synchronous motion, but with offset centers of rotation. The relative motion is the same as if one were orbiting.
Leaks from axial gaps are prevented by the use of spiral-shaped tip seals, placed into grooves on the tips of both spirals.[13] These tip seals also help lower the friction and can be replaced when worn down. Some compressors use the pressurized discharge gas to push both scrolls together, eliminating the need for tip seals and improving sealing with use; these compressors are said to wear-in instead of wear-out.[14][15][16][17]
These devices are known for operating more smoothly, quietly, and reliably than conventional compressors in some applications.[18]
The compression process occurs over approximately 2 to 2½ rotations of the crankshaft, compared to one rotation for rotary compressors, and one-half rotation for reciprocating compressors. The scroll discharge and suction processes occur for a full rotation, compared to less than a half-rotation for the reciprocating suction process, and less than a quarter-rotation for the reciprocating discharge process. Reciprocating compressors have multiple cylinders (typically, anywhere from two to six), while scroll compressors only have one compression element. The presence of multiple cylinders in reciprocating compressors reduces suction and discharge pulsations. Therefore, it is difficult to state whether scroll compressors have lower pulsation levels than reciprocating compressors as has often been claimed by some suppliers of scroll compressors. The more steady flow yields lower gas pulsations, lower sound and lower vibration of attached piping, while having no influence on the compressor operating efficiency.
Scroll compressors never have a suction valve, but depending on the application may or may not have a discharge valve. The use of a dynamic discharge valve is more prominent in high pressure ratio applications, typical of refrigeration. Typically, an air-conditioning scroll does not have a dynamic discharge valve. The use of a dynamic discharge valve improves scroll compressor efficiency over a wide range of operating conditions, when the operating pressure ratio is well above the built-in pressure ratio of the compressors. If the compressor is designed to operate near a single operating point, then the scroll compressor can actually gain efficiency around this point if there is no dynamic discharge valve present (since there are additional discharge flow losses associated with the presence of the discharge valve as well as discharge ports tend to be smaller when the discharge is present).[19][20]
The isentropic efficiency of scroll compressors is slightly higher than that of a typical reciprocating compressor when the compressor is designed to operate near one selected rating point.[21] The scroll compressors are more efficient in this case because they do not have a dynamic discharge valve that introduces additional throttling losses. However, the efficiency of a scroll compressor that does not have a discharge valve begins to decrease as compared to the reciprocating compressor at higher pressure ratio operation. This is a result of under-compression losses that occur at high pressure ratio operation of the positive displacement compressors that do not have a dynamic discharge valve.
The scroll compression process is nearly 100% volumetrically efficient in pumping the trapped fluid. The suction process creates its own volume, separate from the compression and discharge processes further inside. By comparison, reciprocating compressors leave a small amount of compressed gas in the cylinder, because it is not practical for the piston to touch the head or valve plate. That remnant gas from the last cycle then occupies space intended for suction gas. The reduction in capacity (i.e. volumetric efficiency) depends on the suction and discharge pressures with greater reductions occurring at higher ratios of discharge to suction pressures.
Scroll compressors tend to be very compact and smooth running and so do not require spring suspension. This allows them to have very small shell enclosures which reduces overall cost but also results in smaller free volume.[22]
Scroll compressors have fewer moving parts than reciprocating compressors which, theoretically, should improve reliability. According to Emerson Climate Technologies, manufacturer of Copeland scroll compressors, scroll compressors have 70 percent fewer moving parts than conventional reciprocating compressors.[23]
At least one manufacturer found through testing that the scroll compressor design delivered better reliability and efficiency in operation than reciprocating compressors.[24]
The scroll expander is a work-producing device used mostly in low-pressure heat recovery applications. It is essentially a scroll compressor working in reverse; high enthalpy working fluid or gas enters the discharge side of the compressor and rotates the eccentric scroll before discharging from the compressor inlet. The basic modification required to convert the scroll compressor to a scroll expander is to remove the non-return valve from the compressor discharge.[25]
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.
The scroll compressor was first invented in by French engineer Leon Creux, but due to the limitations of processing technology, it was not mass-produced until the early s. Since the s, 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 , 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 , Japan’s Sanden Company kicked off the mass production of automotive air-conditioning scroll compressors.
In , 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.
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.
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)
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.
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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.
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.
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.
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.
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.
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.
The above is a brief introduction to what is scroll compressor and how does it work, as well as its advantages and applications. If you want to know more about oil-free scroll air compressors, you can click the consultation button by the right side. Kotech is the first choice for all your air compressor needs.
Our experts team is experienced and professional, and can help you solve any problem you may have on air compressors. From selection to installation to maintenance, we can provide a complete guide including optimal advice and solutions for your project.
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