velocitytriangles

velocitytriangles - UNSTEADY PROCESS IS REQUIRED TO CHANGE...

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Unformatted text preview: UNSTEADY PROCESS IS REQUIRED TO CHANGE TOTAL ENTHALPY OF THE FLOW EULER TURBINE EQUATION Torque ~ Axial flux of ang. mom. Power = wT Power = mass flow (DhT) T=m(rcvc-rbvb) Cp (TTc - TTb) = w (rcvc - rbvb) MULTI-STAGE AXIAL COMPRESSOR Reproduced with the kind permission of Rolls-Royce plc. Copyright Rolls-Royce plc. Used with permission. MULTISTAGE AXIAL COMPRESSOR Reproduced with the kind permission of Rolls-Royce plc. Copyright Rolls-Royce plc. Used with permission. CONCEPTUALLY • Rotor (rotating part) adds or removes energy – changes swirling component of kinetic energy, leaves axial component about the same 1 PT = p + r(u2 + v 2 + w 2 ) 2 Internal energy Radial k.e. (small) Tangential k.e. (swirl) Axial k.e. • † Stator (stationary part) does not add or remove energy (there is a torque but no w) – Changes swirl component of kinetic energy into internal energy, leaves axial component about the same A STATOR IS A NOZZLE (ACCELERATES OR DECELERATES FLOW) VELOCITY TRIANGLES RULES 1) Always consider blade in reference frame attached to the blade 2) For now (Unified) assume axial velocity and radius are constant throughout the blade rows 3) Flow always leaves blades at the trailing edge angle 4) Check inlet flow angle to next row to make sure flow is roughly aligned with blade (in blade reference frame) 5) Can only have work done across moving blade rows 6) Check change in stationary reference frame tangential velocity across moving stages to assess work input or extraction An increase in stationary frame tangential velocity in the direction of rotor motion means work added to flow A decrease in stationary frame tangential velocity in the direction of rotor motion means work added to flow ...
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