INFORMAZIONI SU

Design of Turbomachinery (the English translation of "Progetto di macchine")

Design of Turbomachinery (traduzione in inglese del programma di Progetto di macchine) - cdl magistrale in Ingegneria Meccanica

Teacher

prof. Pietro GIANNATTASIO

Credits

6 CFU

Language

Italian

Objectives

This course is aimed at promoting a deeper knowledge of the fluid dynamics and thermodynamics of turbomachinery, starting from the basic principles stated in the course of Macchine I. In particular, the introduction to two- and three-dimensional theories of axial turbomachines is aimed at providing high level tools for the optimum design of such an important class of fluid machines.

Acquired skills

- Deeper knowledge of the thermodynamics and fluid dynamics of turbomachinery.
- Greater understanding of the operating features of the different kinds of turbomachines.
- Prediction of the performance of a given turbomachine in any operating condition.
- Two-dimensional design of axial turbomachines on the basis of the cascade flow theory.
- Three-dimensional design of axial turbomachines by means of the radial equilibrium theory.
- Design of centrifugal pumps, fans and compressors.
- Optimum design of critical components of the turbomachines.

Lectures and exercises (topics and specific content)

Review of thermodynamics and fluid dynamics: mass, momentum and moment of momentum conservation equations; energy conservation equations in lagrangian and eulerian form; the second law of thermodynamics; reversible processes, friction losses and heat transfer in fluid machines; definitions of fluid machine efficiencies (10 hours).
Analysis and design of nozzles and diffusers: one-dimensional isentropic flow model; subsonic and supersonic nozzles; computation of the mass flow rate through nozzles and multi-stage turbines; boundary layer development and total pressure losses in nozzles and diffusers; optimum design of diffusers for maximum efficiency or pressure coefficient (8 hours).
Two-dimensional blade cascades: analysis of cascade forces; lift, drag and relative coefficients; performance of turbine and compressor cascades; Lieblein and Howell correlations for compressor cascades; Ainley correlation and Zweifel criterion for turbine cascades (10 hours).
Two-dimensional theory of axial-flow turbines: thermodynamics and fluid dynamics of the turbine stage; total-to-static and total-to-total efficiencies; Soderberg correlation; types of axial turbine design; choice of the stage reaction; maximum total-to-static efficiency of a reversible turbine stage; application of the cascade flow theory to the design of axial turbines (6 hours).
Two-dimensional theory of axial-flow compressors:  thermodynamics and fluid dynamics of the compressor stage;  stage loss relationships and efficiency; choice of reaction and stage loading factor; off-design performance; work-done factor; application of the cascade flow theory to the design of axial compressors, pumps and fans; unstable operation of compressors (surge and rotating stall) (6 hours).
Three-dimensional flows in axial turbomachines: theory of radial equilibrium and its application to both direct and indirect (design) problems: free-vortex flow, forced vortex, general whirl distribution, constant alfa vortex, constant specific mass flow vortex; application of the radial equilibrium theory to the design of axial turbomachines; secondary flows and secondary losses in axial turbomachines (8 hours).
Centrifugal pumps, fans and compressors: thermodynamics and fluid dynamics of the stage; optimum design of a pump inlet and a compressor inlet; computation of the slip factor and design of the impeller; Mach number at compressor impeller exit; design of vaneless and vaned diffusers; choking in a compressor stage (8 hours).
Radial flow turbines: types of Inward Flow Radial (IFR) turbines; the 90 degree IFR turbine, thermodynamics and fluid dynamics of the stage, design point efficiency, design criteria (4 hours).
Exercises (12 hours).

References

- Teacher's notes 
- S.L. Dixon - Fluid Mechanics, Thermodynamics of Turbomachinery - Pergamon Press, Oxford (UK)

Type of exam

Written and oral