08081 - Turbomachinery

Learning outcomes

The objective is to give to students the information required to understand the behavior of all the turbomachineries employed in the aeronautical and aerospace field.

Course contents

Basic knowledge

Classification of machinery.
Water as a potential fluid: characteristics and Ts and hs diagrams.
Conservation of mass. Energy conservation: first principle for a closed system and for an open system (mechanical and thermal). Entropy and enthalpy.
Ideal gas and ideal fluid: definition, major transformations and their representation on the Ts, hs diagrams. Work and efficiency, polytropic and isentropic efficiency for a compression and an expansion.
Combustion: definition of stoichiometric air, excess air, lower heating value.

Centrifugal pumps

Scheme of the pump and calculation of the characteristic diagrams.

Problems related to the installation/operating conditions of the pumps.

Dimensional analysis and similitude.

Series and parallel circuits

Gas turbine thermodynamic cycle

Generality, Brayton cycle, simple plant configuration and cycle representation on the diagram Ts. Conditions for the representability of the cycle in the Ts diagram. Thermodynamic analysis of gas turbine self-sustaining condition. Assessment of performance. Condition of maximum useful work and maximum efficiency.
Regenerative cycle, thermodynamic diagrams, problems and limitations in employment.
Cycle with separated compression phases (inter-cooling): Schematic diagram and thermodynamic conditions. Complete inter-cooling, condition of maximum useful work, problems and limitations in employment.
Post-combustion cycle: Schematic diagram and thermodynamic process.
Turbine blades cooling: techniques and evaluation of the needed cooling mass flow rate, typical blades materials.
Centrifugal compressor: specific work and efficiency. Compressors and turbines performance representation.
Axial compressor: velocity triangles, specific work and efficiency. Surge, chocking. Inducer. Starting problems for axial compressors.

Volumetric machines

Volumetric pumps and volumetric compressors

Compression refrigeration cycle

Definition of COP. Cycle at saturated vapor compression cycle (biphasic with intercooler, dual-separator, dual-separator with bubbler), biphasic compression cycle with two temperatures of vaporization. Characteristics of fluids for refrigeration equipment and their classification.

Applications of refrigeration cycles to liquefaction of hydrogen and oxygen.

Readings/Bibliography

Sistemi energetici e loro componenti, 2a ed., G. Negri di Montenegro, M. Bianchi, A. Peretto, Pitagora Editrice Bologna

Teaching methods

Teaching is organized in class lectures and numerical exercises.

Attendance is strongly recommended for an improved learning of concepts and notions, but does not affect the final evaluation process.

Assessment methods

The assessment methods consist of an oral part lasting about 1 hour, during which the student must answer three questions covering the entire program.

The evaluation, expressed in thirtieths, will be higher if the student is:

• autonomous in articulating responses to the three questions;
• exhaustive in explaining the arguments;
• precise in representing the functionality of the free-hand sketches.

The module of Turbomachinery T (6 CFU) is one of the two that, together with Propulsione aeronautica e spaziale T (6 CFU), constitutes the integrated course of Propulsione Aerospaziale T (12 CFU). The vote that will be recorded will be calculated with the arithmetic average of the single votes that the student will have obtained in the two modules. If the result of the average presents the decimal number 0.5, the vote will be rounded in excess.

In order to obtain the "30 cum laude" final evaluation, the student must be in one of the following two cases:

• receiving "30 cum laude" in both modules
• ·obtaining "30 cum laude" in one module and 30 in the other.

The exam dates are comunicated in advance through the AlmaEsami web platform of the University of Bologna.

At the time of the exam the student must carry an identification document.

Teaching tools

The slides used by the teacher are available on the VirtuaLe platform.
Practical examples and engines are shown in the lab facilities.

Office hours

See the website of Vittorio Ravaglioli

See the website of Fabrizio Ponti