Air compressor

Résumé

An air compressor is a machine that takes ambient air from the surroundings and discharges it at a higher pressure. It is an application of a gas compressor and a pneumatic device that converts mechanical power (from an electric motor, diesel or gasoline engine, etc.) into potential energy stored in compressed air, which has many uses. A common application is to compress air into a storage tank, for immediate or later use. When the delivery pressure reaches its set upper limit, the compressor is shut off, or the excess air is released through an overpressure valve. The compressed air is stored in the tank until it is needed. The pressure energy provided by the compressed air can be used for a variety of applications such as pneumatic tools as it is released. When tank pressure reaches its lower limit, the air compressor turns on again and re-pressurizes the tank. A compressor is different from a pump because it works on a gas, while pumps work on a liquid. Classification Co

Source officielle

https://en.wikipedia.org/wiki/Air_compressor

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Highly Loaded Compressor With Boundary Layer Suction

Klaus Hubrich

2005

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Impact of large tip clearance ratios on the performance of a centrifugal compressor

Markus Diehl, Jürg Alexander Schiffmann

Ultra-compact and fast spinning turbomachinery is a key technology to increase performance of domestic heating applications and to address decentralization of power and heat as a consequence of the rise of renewable energy sources. Recently, a heat pump using a reduced-scale centrifugal compressor with an impeller diameter of 20 mm supported on gas bearings was tested successfully and higher system performance compared to commonly used positive displacement compressors was achieved. Nonetheless, due to the small feature size as well as manufacturing tolerances, the performance of such compressor systems is deteriorated compared to large-scale systems. The tip gap necessary to ensure a free spinning of the rotor on gas bearings is relatively large compared to industrial compressors. Unfortunately, limited experience about centrifugal compressors running on relative large clearance exists. This paper investigates the impact of tip leakage on the performance of centrifugal compressor systems for relative clearance ratios, ranging from 3 up to 15 %. The tip leakage analysis is conducted numerically on an experimentally validated centrifugal compressor system operating with refrigerant R134a. In order to investigate the behavior of the compressor by altering its clearance ratio, impellers with different blade heights are used to adjust the tip gap. The change in efficiency is investigated and empirical correlations available in literature are assessed. A new method to predict change in efficiency as function of relative clearance ratio is provided, thus extending current correlations to much higher relative clearance ratios.

2019

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Externally Pressurised and Hybrid Bearings Lubricated with R134A for Oil- Free Compressors

Adam Molyneaux

This paper discusses the choice and implementation of bearings for oil-free compressors where the system refrigerant is used as the lubricant in externally pressurised and hybrid bearings. The problems of oil contamination in heat pump application is described followed by methods to produce genuine oil-free hermetic systems. Alternative bearing choices are described for high and low speed applications. Theoretical and experimental results are presented showing the effects of turbulence in the bearing clearence and pockets of externally pressurised thrust and journal bearings for a co-rotating scroll compressor operating with r134a. The paper concludes that design methods are now available to enable the incorporation refrigerant lubricated bearing in hermetic oil-free compressors.

1996

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