Gas compressor

A compressor (compressor ) is a fluid energy machine, which are used for compressing gases.

• 2.3.1 Transonic Compressor

Basics

Decreasing the volume of a gas, it is called compacting or compressing. Such devices are called compressor or compressors. At discharge processes an existing suction volume V1 is compressed to the operating pressure P1 to a smaller volume V2. In the smaller volume V2, there is an increased pressure p2, and the gas heats up.

As the volume decreases during compression, it is critical to provide the respective pressurized state to the volumetric flow. Typical specifications are the suction rate (based on suction pressure p1), outlet flow rate (based on the final pressure p2 ) and the standard volume flow (relative to the standard state p = 101.3 kPa, T = 273.15 K = 0 ° C).

For compaction operations, shall remaining constant temperature, the Boyle's law. In the application of this law is to make sure that p1 and p2 are absolute pressures. However, all pressure data in pneumatic systems related to the excess pressure Pe with respect to the atmospheric pressure. Otherwise, pressure data are particularly indicated.

• Pressure specifications in pneumatics refer to overpressure
• Pressure gauges in pneumatics are set to overprint

Designs

Basically, there are two modes of operation. For one, the turbo compressor for large volume flows with small compressor discharge pressures, on the other displacement compressor with a small throughput and large compressor discharge pressures. The various types of compressors are divided into oil-lubricated and oil-free compressors.

• Liquid ring pump
• Reciprocating Compressors
• Ionic compressor ( ionic compressor )
• Compressor blades
• Rotary compressor
• Swash plate compressor ( Wobble Plate)
• Labyrinth -piston compressors
• Screw compressor
• Roots blower
• Swash plate compressor ( Swash Plate)
• Scroll Compressor ( "VW G-Lader " )
• Junkers free-piston compressor, see also free-piston engine
• Diaphragm compressor
• Side Channel Blowers

Piston compressor

In reciprocating compressors, which operate on the displacement principle, the gas is enclosed in a volume, compressed and discharged again. These compressors operate cyclically, have low flow rates and high pressure conditions.

Screw compressor

The screw compressor is one of the rotating, twin-screw displacement compressors with internal compression. It is simple structure, small size, low mass, smooth, low pulsation and a smooth running, because it lacks oscillating masses and control organs. Reaching up to 30 bar overpressure.

Screw compressor belonging to the group of the rotary compressor.

History

The idea to build a screw compressor was already in 1878, but the geometry of the surfaces could not be established due to technical difficulties. About half a century later, in 1930, it then had the technical production prerequisites to manufacture the complex coil geometry. A Swedish engineer named Alfred Lysholm succeeded in 1955 to produce the first screw compressor in the world and successfully use. Initially, however, the compressor could not prevail against the common piston compressor. The internal losses of the screws were too large to speak of an effective compressor, and especially of an alternative to the piston compressor. Once again had to pass until finally the crucial point was found in the improvement of the efficiency of 40 years. An oil injection into the compressor stage reduces the loss rate significantly and is the compressor block at the same time as cooling. In addition, then rolling bearings could be used, rather than the usual plain bearings. Overall, this finding led to very simply constructed, yet robust compressors. Screw compressors have proven themselves now - about half of all compressors currently in use are screw compressors.

Operation

Two arranged in parallel, mechanically positively coupled shafts with intermeshing helical gearing in a housing are at the heart of this system. At the pitch line ( the point at which touch the two helical waves ) between the two waves is the passage for the fluid to be pumped mechanically locked ( by the necessarily precise manufacturing of the teeth ). The medium is located in the tooth gears and held by the housing therein. It is supported in the axial direction. Are located at the two ends of the axles in the housing slots for control input ( suction ) and outlet ( pressure side). The length of the waves, the slope of the spirals and the control slots must be adjusted so that there is no direct passage from the pressure to the suction side, so it can not return result. The funded amount of the medium, apart from the losses, depending on the speed.

The medium (eg air) fills on the suction side of a tooth gear per shaft, the suction side closes the rolling-off during further rotation. It now forms around the shaft spirally an air hose. Upon further rotation, he is transported towards the discharge side. Transported to the discharge side end, opens the mechanics of the hose, air is promoted by the continued rotation of the machine.

If a largely pulse -less compression required by the subsequently arranged plants, must be pre-compressed in the compressor already. For this purpose, the gas is not released just downstream of the compressor. The opening tooth gear on the pressure side is opposed, therefore, a wall. Upon further rotation of the shaft, the volume of the air hose reduced, since it is almost pressed against the wall, it is compressed. Now depending on verlangtem pressure may sooner or later these compressed air hose to be released by a control slot.

Turbo compressor

When turbo compressor is added to the flowing fluid through a rotating rotor according to the laws of fluid mechanics energy. This design operates continuously and is characterized by small pressure increase per stage and high volume throughput. Radial and axial compressor are the two main types of centrifugal compressors. Axial-flow compressor in the gas to be compressed flows in a direction parallel to the axis through the compressor. The centrifugal compressor, the gas flows axially into the impeller of the compressor stage, and is then deflected outwardly ( radially ). In multistage centrifugal compressors so that a flow deflection is necessary after each stage.

These are used in the turbocharger compressor around (mostly as a radial compressor ) or in jet engines (usually as axial compressor ). Here, the pressure does not increase by the tapered channel cross-section, but rather the fact that the space between the blades of a compressor, such takes the form of a diffuser. Here the pressure and temperature increase as the speed decreases. The rotating portion of a compressor stage ( rotor, rotor ) of the air is supplied to the time needed for the further pressure build-up kinetic energy.

Transonic Compressor

At a transonic compressor is defined as a turbo compressor the axial or radial type in which the flow rate in the relative system ( the observers ' sitting on the rotating rotor blade " ) is at least locally greater than the speed of sound. The front steps of modern compressor in aircraft engines and gas turbines are usually designed transonic, as here, the temperatures are still low and you get a higher Mach number at the same flow rate. The Mach number is the ratio of the flow rate to the speed of sound, the latter is a function of the temperature and the chemical composition of the gas.

The advantage of transonic compressor are the high power densities, which is particularly important for aircraft engine compressors, since the system is very compact. These compressors are characterized by complex systems of compression shocks, which greatly complicate the interpretation and the stable operation of the compressor. Another disadvantage is the high losses associated with the shock waves and which can be addressed only through complex three-dimensional blading and sophisticated profiles. Usually, the first stage of the low pressure compressor of engines are designed transonic because of the large diameter of the rotors and the speed equality for all points on the wave aggregates.

Open and hermetic compressor

In refrigeration technology additionally differs more:

• Fully hermetic compressor - engine and compressor are located in an enclosed case and in direct contact with the refrigerant
• Semi-hermetic compressors - the motor is flange-mounted on the compressor housing
• Open compressor - the compressor is driven by belts, gears or cogs

Delivery quantity and operating pressure

Stationary compressors are usually driven by electric motors. For mobile and portable equipment is often used to drive internal combustion engines ( construction site compressors). To identify a compressor of the achievable pressure and the delivery quantity used. The delivery quantity is the volume of air per unit time by; it is otherwise indicated for small plants in liters / min in m3/min. Unfortunately, often common - but misleading - is to specify the ( theoretical ) Suction as the product of speed and displacement. She says nothing about the actual delivery, since it is the volumetric filling ratio is neglected. Pneumatic systems typically operate at a pressure of 6 bar; as a lower limit can be given 3 bar and 15 bar as the upper.

Parameters

• FAD - volume of fluid delivered per unit time.
• Operating pressure - pressure attainable.
• Pressure ratio = final pressure / suction
• Delivery rate - Refers to the ratio of pumped, the theoretically (due to geometry) potential flow.

In order to better compare compressors of various designs and operating points, the standard volume flow is often considered. This is the flow rate of the compressor, converted to standard conditions. ( Temperature, pressure, humidity)

Applications

• Respiratory protection compressor
• Compressed air system
• Air compressor
• Air pump
• Engine charging, as a means for "forced filling" of the engine with additional air or gas mixtures, to increase performance