subject: Air-compressor Performance [print this page] Technology to Upgrade the Performance of Air Compressor by Reducing the Piston-Cylinder Clearance, The technology is applicable to all kinds of reciprocating compressors used by vehicles and air conditioners, as well as those used in chemical, medical, and food and construction industries. For these compressors, pressure is developed by moving a piston in a cylinder.
It is well known that the friction resulted from the motion of an actuating piston in the cylinder, together with the high pressure sustained at the piston's head, will lead to an increase in temperature of between 120 - 220 , and cause the piston to expand. Most of the pistons used in air compressors are made of aluminum alloy while the cylinders,
Cast iron. The coefficient of expansion of aluminum is 2.5 times that of cast iron.
Providing adequate allowance for expansion, and (2) allowing a coating of lubricant to form in between. These engineering designs are to ensure that no overheating will take place and the metal surfaces are protected, thus safeguard against any serious material wear and destructive mechanical fault.
Generally, most designers, after going through repeated calculations and experiments, will try to keep the clearance between the piston and the cylinder as minute as possible. For the TA-80 type air-compressor, the clearance between the piston and the cylinder is in the range of 0.07mm to 0.12mm. Nevertheless, however small the clearance is, apart from reduction in air-tightness, the overflow of lubrication oil into the compressed air chamber is a common phenomenon.
As the reciprocating motion of piston goes on, the friction will cause the clearance to become wider, followed by excessive overflow. And up to a certain point, the straight-line motion will run out of alignment and produce greater noise caused by the knocking of piston against cylinder wall. At this stage, the air-compressor requires an overhaul, or worse, to be discarded.
The invention aims at increasing the air-tightness of the air compressor housing by narrowing down the clearance between the piston and the cylinder. Besides, the invention will greatly reduce the friction of motion, thus increasing the compressor's mechanical efficiency, preventing the overflow of lubrication oil, reducing energy consumption, eliminating the vibrational noise and prolonging its life span.
Buses and trucks are all equipped with air compressors and the compressed air is the power source for the operations of the automatic opening and closing of doors, and the brakes. The durability, efficiency and reliability of an air compressor are of utmost importance not only to the air compressor itself, but also to the related pneumatic devices, such as door pump and brake pump, in which rubber sealers are found. If overflow of lubrication oil takes place in the air compressor, the oil molecules will permeate into the compressed air reservoir. The sustained action of the "contaminated" compressed air exerts upon those devices are bound to speed up the process of wear and corrosion of the rubber sealers, hence shortened their life span of the whole system. On the contrary.
