![]() ![]() Different positions of the cylinders are possible (vertical, horizontal, angular, V- or W-shaped, etc.). There can be single- and double-acting designs (in the latter, both sides of the piston are acting). Reciprocating compressors can be one-stage and multistage. The volume between the top and the piston at its nearest point to the top position is a waste space. The extreme positions of the piston are called the top and bottom of the stroke. This process takes place during one revolution of the shaft or double stroke of the piston. When gas pressure exceeds the discharge pressure, valve 2 is opened and gas flows from the cylinder into the discharge line until the piston has reached the end of its stroke. When the piston moves back, the cylinder volume is decreased, the gas pressure is increased, and the gas is compressed. When the piston reaches its extreme position, valve 3 is closed. When the piston moves from the top, the cylinder is being filled with the gas at the suction pressure through valve 3. The discharge cavity is hermetically separated from the suction cavity. The piston (5) moves reciprocatingly inside the cylinder with the help of the piston rod (6), crank (9), connecting rod (8) and cross-head (7). The reciprocating compressor, ( Figure 1a), consists of a working cylinder (4) with two valves-a suction valve (3) and a discharge valve (2) in corresponding cavities in the cylinder head (1). Shear force radial compressors and magnetohydrodynamic pumps for plasma transportation by a moving electromagnetic field can also be classified as dynamic machines. Multicasing designs are used to achieve higher values of PR.ĭisplacement machines may be divided into reciprocating and rotary compressors and adsorptive units, while dynamic machines are divided into axial and radial flow compressors and jet units. For high PD units, the PR is equal to 6 to 10 and more. For medium PD units, the PR is usually equal to 1.3 to 4.0. Low PD compressors are termed blowers the PR for them is equal to 1.05 to 1.15. The inlet pressure may vary from 10 −10 Pa to several Pa. If absolute pressure at the compressor inlet is significantly lower than atmospheric pressure, this unit is referred to a vacuum pump or turbomolecular pump. There are also heat (thermosorptive) compressors in which pressure is increased after heating the matrix which absorbed the gas at lower temperature.Īccording to the developed pressure difference (PD), there are three types of compressors: low PD, medium PD and high PD units. The stator cascade transforms this angular momentum of the gas into static pressure. The dynamic machine develops pressure when power supplied to the rotor increases the angular momentum of the gas flowing through the rotor cascade. The pressure ratio (PR) for the displacement machine is the result of decreasing the volume that the trapped gas occupies. There are two main principles of compressor action-the displacement principle with a cyclic process and the dynamic principle with a continuous process of gas compression. Compressors are driven by different types of prime movers (electric motors, steam and gas turbines, diesel engines, etc). They are widely-used as separate units and as important parts of different types of heat engines. Compressors are devices for compression and delivery of gases. ![]()
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