![]() With the opposed design, impeller direction is reversed in adjacent stages. With the in-line design, all impellers face in the same direction. There are two impeller configurations: in-line and back-to-back, or opposed. The impeller configuration has a major impact on stability and the operating envelope. Figure 10-1 Cantilever centrifugal compressor is susceptible to instability (Gibbs 1971). Two factors are critical to the operation of these compressors: impeller configuration and laminar flow, which must be maintained through all of the stages. This process can be continued by adding additional stages until the desired final discharge pressure is achieved. The partially compressed air is routed to the second stage, where the velocity and pressure are increased further. Inlet air enters the first stage of the compressor, where pressure and velocity increases occur. Figure 10-2 illustrates the normal airflow pattern through a horizontal split-case compressor. CenterlineĬenterline designs (i.e., horizontal and vertical split case) are more stable over a wider operating range but should not be operated in a variable-demand system. As a result, the mode shape of the shaft must be monitored closely. Any variation in laminar flow, volume, or load of the inlet or discharge gas forces the shaft to bend or deflect from its true centerline. The overhung design of the rotor (i.e., no outboard bearing) increases the potential for radical shaft deflection. Figure 10-1 illustrates a typical cantilever design. The cantilever design is more susceptible to process instability than centerline centrifugal compressors. Common designs are overhung or cantilever, centerline, and bullgear. The actual dynamics of centrifugal compressors are determined by their design. In these multistage units, a progressively higher pressure is produced by each stage of compression. The pressure of the gas increases as it is pushed through the reduced free space within the volute.Īs in centrifugal pumps, there may be several stages to a centrifugal air compressor. The gas is compressed as more gas is forced into the volute by the impeller blades. ![]() As the impeller rotates, the gas is accelerated by the rotating element within the confined space created by the volute of the compressor's casing. In a centrifugal compressor, air or gas at atmospheric pressure enters the eye of the impeller. The force utilized by the centrifugal compressor is the same as that utilized by centrifugal pumps. In general, the centrifugal designation is used when the gas flow is radial and the energy transfer is predominantly due to a change in the centrifugal forces acting on the gas. ![]() This chapter provides a general discussion of these types of compressors. Compressors can be grouped into two major classifications: centrifugal and positive displacement. A compressor is a machine used to increase the pressure of a gas or vapor. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |