Università Roma Tre

The similitude theory applied to turbomachines

- Criteria and limits;
- Dimensional analysis and performance laws;
- Relevant applications to design and analysis of turbomachines;

Hydraulic machines

1) Centrifugal and axial pumps

- Basic principles and performance
- Influence of cavitation on pump selection and design;
- Preliminary design of the main components (radial and axial impellers, unvaned and vaned diffusers, volutes)
- Main parameters which affect pump performance;
- Operation and control: basic principles.

2) Hydraulic turbines

- Basic principles and performance
- Preliminary design of Pelton turbines;
- Preliminary design of reaction turbines (Francis and Kaplan);
- Draft tube and cavitation in reaction turbines;
- Performance characteristics;
- Operation: basic principles.

Compressible flow turbomachines

3) Fluid-dynamics in ducted flows

- Review of applied thermodynamics and gas-dynamics;
- Steady one-dimensional and two-dimensional flows, vorticity, Crocco’s theorem, shock waves. Shock and expansion waves on complex aerofoils.
- Two-dimensional cascades;
- Boundary layers on complex aerofoils, effect of pressure gradients on stall in cascades, thermal boundary layers.
- Shock wave/ boundary layer interaction;
- Three-dimensional effects: secondary flows.

4) Axial compressors

- Basic principles, application of dimensional analysis, performance characteristics;
- Preliminary design: elementary theory, factors affecting stage pressure ratio, blockage in the compressor annulus, degree of reaction, design process;
- Mean-line analysis: efficiency optimization.
- Three-dimensional flow: free-vortex law, constant degree of reaction law, constant rotor absolute inlet angle law;
- Stage efficiency: three-dimensional optimization.
- Correlations for the evaluation of losses and deviation.

5) Steam Turbine

- Basic principles and performance characteristics.
- Analysis of: impulse stage, velocity-compounded impulse stage, reaction stage. Comparison and discussion.
- Total-to-total and total-to-static blade efficiency, windage losses, partial admission losses, humidity losses.
- Preliminary design: principles for selecting the path of multistage turbines, rough estimation of the process of steam flow in the path, estimation of stage diameter, number of stages and distribution of enthalpy drops. Calculation of the steam path.

6) Axial gas turbines

- Basic principles, application of dimensional analysis, performance characteristics;
- Preliminary design: elementary theory, vortex theory (free-vortex design, constant nozzle angle design);
- Stage performance limitations;
- Cooling methods: basic principles.


Students will apply design methodologies and procedures on several case studies.

• T. Wright e P.M. Gerhart, "Fluid Machinery: Application, Selection and Design", CRC Press ISBN978-1-4200-8294-4
• Documents available on Moodle