28658 - Energy Machines and Systems T-1

Learning outcomes

Providing students with knowledge regarding constructive, functional and management aspects of fluid machines and  of energy conversion systems, with a focus on generating stationary systems of electricity and heat used in industrial processes and in the tertiary and residential sectors.

Course contents

Requirements/Prior knowledge

A prior knowledge and understanding of physics, thermodynamics and chemistry is required to attend with profit this course.

In addition, students should know how to use mathematical tools useful for analyzing and modeling fluid machines and energy systems.

Fluent spoken and written Italian is a necessary pre-requisite: all lectures and tutorials, and all study material will be in Italian.

Course Contents

Primary energy sources

Potentiality, conversion systems and applications of solar, geothermic, hydroelectric, wind, wave tidal and nuclear energy.

Thermodynamic basics

Ideal gas compression and expansion: isentropic and polytropic work and efficiency, total enthalpy and temperature, speed of sound, polytropic transformations and thermodynamics diagrams.

Heat exchanger

Counter-flow, parallel-flow and cross-flow heat exchangers. main design aspects.

Averaged mean logarithmic and effectiveness-NTU methods.

Boiler and steam generator

Combustion: stoichiometric oxidation reactions, heating values, energy density, CO2 emission, adiabatic temperature.

Typologies and applications, steam generator efficiency and water circulations.

Gas Turbine

Layout of a Brayton cycle gas turbine plant. Operating principle of compressor, turbine and combustion chamber. Work and efficiency trend as a function of compression ratio, polytropic efficiency and TIT (c_p=constant). T,s diagram.

Thermodynamic optimization of gas turbine performance under hypothesis of ideal fluid. Equations governing the operation of a gas turbine in case of real gas.

Comparison between ideal and real performances of a Brayton cycle gas turbine plant. Influence of TIT, polytropic efficiency and compression ratio on real performance.

Steam power plant

Basic layout an operating principle. Heat exchange diagram for the condenser and criticisms related to the decrease in condenser pressure. Acid dewpoint. T-s and h-s diagrams. Compression work of a liquid. Analytical evaluation of the convenience of changing thermodynamic parameters of a steam plant (dh/ds <h/s).

Hypercritical steam cycles. Effect of the condenser pressure decrease on the thermodynamic efficiency.

Layout of a steam plant with reheat, T-s diagram. Optimization of the reheating pressure of a steam group. Quality trend at the outlet of the steam turbine as function of the reheating pressure.

Layout of a steam plant with one regeneration level, operating principle and T-s diagram. Thermodynamic optimization following the adoption of one regeneration level in a steam group (degree of regeneration). Mixing and surface heat exchangers: architectural and performance differences.

Layout of a steam plant with three regeneration levels. T-s diagram. Energy balances at the regenerative heat exchangers. Produced power and efficiency.

Combined cycle power plant

Thermodynamic analysis of combined cycles with one or more pressure levels

Component description: heat recovery steam generator, condenser, steam turbine, cooling systems, etc.

Environmental impact

Cogeneration: Combined heat and power

Thermodynamics of combined heat and power plants (CHP), performance, comparison with separate production.

Cogeneration framework, historical evolution and current situation.

Gas turbines in cogeneration applications: layout, thermodynamics aspects, performance and operation.

Steam turbines in cogeneration applications: back pressure steam turbine and condensing steam turbine layout, thermodynamics aspects, performance and operation.

Combined heat and power in cogeneration applications: layout, thermodynamics aspects, performance and operation.

Volumetric Pumps

Architecture, performance curves, volumetric and hydro-mechanical efficiencies.

Alternating, Rotating and Vane Rotary Pumps.

Centrifugal Pumps.

Architecture and operating principle. Ideal and real performance curve.

Operating point determination and off-design behavior.

Cavitation: phenomenon explanation, NPSH parameter definition, cavitation conditions, NPSH trend as function of the flow rate, determination procedure. Series and parallel connected pumps.

Internal Combustion Engines

Architecture and main concepts definition. Ideal thermodynamic cycles: Otto, Diesel and Sabathé (cycle and efficiency).

Ideal indicated cycle diagrams (Otto, Diesel and Sabathè), limit and real cycles.

Efficiency influence on the engine: combustion, thermodynamic, indicating, volumetric and mechanical efficiency.

Net power evaluation via conversion efficiency analysis

Indicated mean pressure, real mean pressure. Power and torque shaft expression.

Average exhaust gas temperature determination.

Displacement fractioning with constant power and constant displacement, fractioning limits. Cylinder number effects and multi-cylinder architecture.

Pollutant emissions: formation, control and post treatments.

Internal combustion engines in steady-state applications. Configurations layout, performance, co/tri-generation applications, comparison with other technologies.

 

Readings/Bibliography

"Sistemi Energetici e macchine a fluido" G: Negri di Montenegro, M. Bianchi A. Peretto, III Edizione – Pitagora Editore

"Gas Turbine Theory" H. Cohen, G.F.C. Rogers, H.I.H. Saravanamuttoo, Longman scientific & technical

Motori Endotermici Alternativi, Giorgio Minelli, Pitagora Editrice.

Internal Combustion Engine Fundamentals, J.B. Heywood, McGraw-Hill.

Teaching methods

The course consists of 9 credits (CFU) divided into two modules in series: the first one (6 CFU) taught by prof. Michele Bianchi and the second one (3 CFU) by prof. Francesco Melino.
Both modules provide some lessons presenting numerical examples.

Assessment methods

The examination at the end of the course aims to assess the achievement of learning objectives, verifying the knowledge that the students have acquired about design aspects, structural, functional and management of fluid machines and energy systems.
The final grade is defined by a single oral exam, testing the student's knowledge in all topics covered in the 9 CFU.

Teaching tools

Teaching materials: teaching material presented in class will be made available to the student in electronic format via internet.

This material should be printed and brought to class. To download the teaching material: http://campus.unibo.it/ Username and password are reserved for students enrolled at the University of Bologna

 

Office hours

See the website of Michele Bianchi

See the website of Francesco Melino