Analysis of Compressors P M V Subbarao Professor Mechanical Engineering Department Active Devices for Infusion of Life into Fluid….

Classification of Compressors Rotodynamic Compressors Positive Displacement of Compressors Centrifugal Compressors Mixed Compressors Axial Compressors Reciprocating Compressors Rotory Compressors

Centrifugal Vs Axial : Flow Area

Centrifugal Vs Axial : Level of interaction

In search of Time scale in Requirement Primary characteristics of a requirement. The effect:  p The Capacity: Flow Rate Q (m 3 /s). Density of fluid:  (kg/m 3 ).

Machine-Fluid Matching Parameter: For compressible fluid machines

Take j = -3/2

Take i = 1/2 & j = -3/4

Time Scale of a Machine to Resource Speed: N (rpm) or n (rps) This is named as Specific Speed, N s

Centrifugal Axial Mixed

Role of specific Speed on Design of A Compressor

Centrifugal Compressors The centrifugal compressor consists essentially of a stationary casing containing a rotating impeller which imparts a high velocity to the air, and A number of diverging passages (Diffuser) in which the air is decelerated with a consequent rise in static pressure. Air is sucked into the impeller eye and whirled round at high speed by the vanes on the impeller disc. Centripetal acceleration leads to increase in rise of some amount of static pressure. The remaining increase in rise of pressure occurs in diffuser.

Multi Stage Compressors

Impeller–Diffuser :Rotor-Stator

Anatomy of A Centrifugal Compressors

V r1 V w2 = U tip V f2 =V r2 V a2 b1b1 Gas Dynamics of A Perfect Impeller V f1 =V a1 U eye V w1 =0

V r1 V f1 =V a1 V w2 V r2 V a2 V f2 b1b1 Reality of Fluid Mechanics b2b2