AIMS AND CONTENT

LEARNING OUTCOMES

The course provides to the students the basic knowledge on turbomachines. The following topics will be developed: operating principles of turbomachines, power conversion physics, energy exchange between fluid and machine;  fluid-dynamics of turbines and compressors; gas turbine architecture for power generation and aeronautical propulsion; general criteria for design and analysis of gas turbines.

TEACHING METHODS

Theoretical and applied lectures

SYLLABUS/CONTENT

Introduction:

• Elements of gas turbine technology.
• Heavy duty gas turbines and aero engine  architecture and technology.
• Basic equations of Turbomachinery.

Axial compressors and Axial turbines:

• Axial turbomachinery geometrical definition and coordinates
• Velocity triangles.
• Main fluid dynamic phenomena in axial compressors and turbines:
• Flow in the blade to blade surface, flow in the meridional plane.
• Viscous flows and energy losses in turbomachines (boundary layers, blade wakes and
• secondary flows).
• Unsteady flows in turbomachines (rotor-stator aerodynamic interaction).

Boundary layer theory:

• Boundary layer concepts. Prandtl approximation
• von Karman momentum integral equation.
• Boundary layer correlations for transition and separation.
• Basics of physics of turbulent boundary layers.
• Effect of turbulence on loss production and momentum transfer.

Axial Compressors:

• Symmetric and repetitive stages, inlet guide vane. Degree of reaction.
• Rotor and stator pressure rise.
• Compression transformation in the h-S thermodynamic plane.
• Aerodynamic forces on profiles. Global aerodynamic loading.
• Local aerodynamic loading. Pressure distribution along the profiles.
• Pressure and velocity coefficient distribution.

Limitation to aerodynamic loading:

• Howell correlation. Effect of flow deflection and cascade solidity.
• Liblein correlations. Diffusion factor.
• Effect of off –design conditions on aerodynamic loading in axial compressors.

Axial Turbines:

• Turbine stage geometry.
• Turbine expansion in the h-S thermodynamic plane.
• Degree of reaction of turbine stages.
• Turbine aerodynamic loading. Zwifel coefficient for cascade  aerodynamic loading.
• Loading distribution: front and aft loaded profiles.
• Low Reynolds number profile performance.
• Wake- boundary layer interaction.
• Secondary flows in axial turbines.

Force balance in axial compressor and turbine rotors:

• Streamwise equilibrium: leads to mechanical energy equations in rotors.
• Cross-stream equilibrium: explains the origin of the profile aerodynamic loading.
• Radial equilibrium: determines the spanwise distribution.

Meridional flow distribution in axial stages:

• Radial equilibrium equation downstream of stator and rotors of axial stages.
• NISRE and ISRE equations.
• Application of NISRE to the design of an axial turbine stage.
• Spanwise distribution of bladed angles and degree of reaction.

Centrifugal Compressors:

• Flow in centrifugal compressors. Velocity triangles.
• Relative total pressure and relative total enthalpy. Transformations  in the h-S thermodynamic plane.
• Impeller aerodynamic loading. Eckart experiments on centrifugal impellers.
• Johnston and Rothe correlation for rotating diffusers.
• Force balance in a centrifugal rotor.
• Moore theory and experiment.
• Jet and wake rotor flow structure.
• Secondary flows in centrifugal rotors.
• Boundary layer stability in rotating diffusers.

RECOMMENDED READING/BIBLIOGRAPHY

S.L.Dixon, FluidMechanics and Thermodynamics of Turbomachinery, Elsevier.

B. Lakshminarayana, Fluid Dynamics and Heat Transfer of Turbomachinery, Wiley.

N. A. Cumpsty, Compressor Aerodynamics, Longman.

H. Cohen, G. Roger, H. Saravanamuttoo, Gas Turbine Theory, Wiley.

TEACHERS AND EXAM BOARD

Exam Board

MASSIMO CAPOBIANCO (President)

DARIO BARSI

MATTEO DELLACASAGRANDE

MATTEO LUZZI

SILVIA MARELLI

FRANCESCA SATTA

DANIELE SIMONI

VITTORIO USAI

GIORGIO ZAMBONI

DAVIDE LENGANI (President Substitute)

PIETRO ZUNINO (President Substitute)

LESSONS

Class schedule

TURBOMACHINERY

EXAMS

EXAM DESCRIPTION

Oral examination

ASSESSMENT METHODS

Discussion on at least two subjects explained in the lectures. The student should demonstrate knowledge and applicative capabilities.

Exam schedule