The selection of angle 2 is a compromise An increase in 2 increases the value

The selection of angle 2 is a compromise an increase

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The selection of angle 2 is a compromise. An increase in 2 , increases the value of useful component (Absolute circumferential Component). This is also called Inlet Whirl Velocity, V w2 = V a2 sin ( 2 ). An increase in 2 , decreases the value of axial component, also called as flow component. This is responsible for definite mass flow rate between to successive blades. Flow component V f2 = V a2 cos( 2 ) = V r2 cos( 2 ). The absolute inlet velocity can be considered as a resultant of blade velocity and inlet relative velocity. The two points of interest are those at the inlet and exit of the blade.
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p v a The reaction effect is an addition to impulse effect. The degree of reaction stage in the drop enthalpy The blades moving in the drop enthalpy The v r A Physical Linking of Momentum and Energy transactions Impulse-Reaction Stage of ATurbine V r2 V a2 V r3 V a3 V f V w
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First law for fixed blades: 1 2 3 2 2 1 2 2 1 2 a V V h h a First law for moving blades: 2 2 2 2 3 2 3 r V V h h r 2 2 2 2 2 3 2 1 2 2 3 1 r r a a V V V V h h Total enthalpy drop in a stage:
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If the gas is to enter and leave the blades without shock or much losses, then relative velocity should be tangential to the blade inlet tip. V r2 should enter at an angle 2 , the inlet blade angle.
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