TYPES OF COMPRESSORS

As shown in Figure 4, there are two basic compressor types: positive- displacemen t and dynamic.

In the positive- displacement type, a given quantity of air or gas is trapped in a compression

chamber and the volume it occupies is mechanically reduced, causing a corresponding rise in

pressure prior to discharge. At constant speed, the ai r flow remains essentially constant with

variations in discharge pressure.

Dynamic compressors impart velocity energy to continuously flowing air or gas by means of

impellers rotating at very high speeds. The velocity energy is changed into pressure ener gy both

by the impellers and the discharge volutes or diffusers. In the centrifugal - type dynamitage

lubricating oil to ensure that it would stick to the cylinder

bore, piston rings, and piston rod packing. The additive also caused

the oil to stick to the moving parts of the valve. Sticktion

is defined

as the TYPES OF COMPRESSORS

As shown in Figure 4, there are two basic compressor types: positive- displacemen t and dynamic.

In the positive- displacement type, a given quantity of air or gas is trapped in a compression

chamber and the volume it occupies is mechanically reduced, causing a corresponding rise in

pressure prior to discharge. At constant speed, the ai r flow remains essentially constant with

variations in discharge pressure.

Dynamic compressors impart velocity energy to continuously flowing air or gas by means of

impellers rotating at very high speeds. The velocity energy is changed into pressure ener gy both

by the impellers and the discharge volutes or diffusers. In the centrifugal - type dynami viscous

adhesion of oil between the moving and stationary

parts of a valve, and is detrimental to valve reliability in

two ways.

First, sticktion inhibits plate opening, causing the plate to slam open

when the pressure force exceeds the sticktion force, which can cause

damage not only to the plate but to the underlying springs. Second,

sticktion delays plate closing, which elevates the plates closing impact

velocity. If the plate closes so late that there is

backflow through

the valve, then there is not only a greater potential for plate

damage

but there is also an actual loss of cylinder capacity. In this

case study,

the high oil viscosity and increased lubrication rate contributed

to

the sticktion effects.