17385 - Energy Systems

Course contents

-        Thermodynamic basics. Compression and expansion thermodynamic transforms. Internal and polytropic efficiency for compression and expansion transforms. Iso-entropic efficiency as a function of pressure ratio and polytropic efficiency.

-        Gas turbine and Brayton cycle. Plant layout. Thermodynamic optimization of the plant performance considering air as ideal gas. Specific work and efficiency as a function of pressure ratio, polytropic efficiency and TIT. Gas turbine performance equations in case of real gas.

-        Two-shaft gas turbine. Layout and operation description.

-        Influence of ambient temperature on GT performance. Load variation at constant TIT and constant TOT.

-        Heat-exchangers. Heat-transfer global coefficient. Wall temperature. Equi- and counter-current heat-exchangers. Temperature diagram, thermal power efficiency. Thermal capacity. Heat-exchanger effectiveness evaluation via T,Q diagram.. Mean logarithmic DT and e,NTU method.

-        Steam turbine cycle power plants. Basic layout. T,s and h,s diagrams. Analysis of cycle parameters effects on efficiency (dh/ds<h/s). Max pressure effect on Rankine cycle efficiency and optimization. Hirn cycle max pressure and max temperature optimization. Influence of condenser pressure. Re-Heating pressure influence. Thermodynamic optimization of steam extraction pressure levels (regeneration). Power plant with three feed-water heaters . T,s and h,s diagram.. Part-load of a steam turbine power plant.

-        Condenser. Scheme with single and multiple passage. Cooling water speed inside tubes and influence on internal heat transfer coefficient. Design features to increase heat-transfer global coefficient.

-        Steam boiler. Scheme and description. Water and gas path. DNB phenomenon. Ljungstrom. heat-exchanger. Thermal load. Combustion temperature and steam generator efficiency. Radiation effects and size effect.

-        Combined-Cycle power plants. Two-pressure level plant layout. T, s diagram. Efficiency. Effect on the plant efficiency of the ratio between the low pressure mass flow and the condenser mass flow. Effect on the plant efficiency of the steam re-heating. Effect on the plant efficiency of the steam turbine extraction. Combined cycle with post-combustion: analytical expression of the efficiency; gas turbine maximum specific work and maximum efficiency with post-combustion.

-        Compressible-fluid Turbomachines. Total and static variables. Equation of motion in the moving vanes. Sound speed. Compressible flow efflux and Chocking. Vanes area section change for subsonic and supersonic conditions: Hugoniot's equation. Euler's equation for a stationary blade row and kinetic energy equation. Impulse stage: velocity triangles, max specific work h,s diagram. Reaction stage of axial turbines velocity triangles, degree of reaction, max specific work., h,s diagram. De Laval turbine. Curtis turbine. Efficiency with multiple Curtis stages. Multiple impulse stage turbine. Reaction stages turbine. Volume flow limit at inlet and outlet. Mixed and double flow turbines. Centrifugal and axial flow compressor: velocity triangles and performance curve. H,s diagram for a Centrifugal compressor stage.

- Incompressible-fluid Turbomachines. Pelton turbine, velocity triangles and maximum work condition. Characteristic index, specific velocity and specific diameter; Balje diagram. Francis turbine: inlet and outlet velocity triangles. Diffuser in Francis turbine and kinetic energy and geodetic energy recovery. The Thomà cavitation number. Kaplan turbine: hub and tip velocity triangles. The helical turbine and efficiency as a function of  power.

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