After the course the student is able to
- Explain the working principle of turbomachines
- Determine the suitability of a turbomachine for a specific duty in relation to its specific speed
- Perform scaling analyses for hydrodynamic machines and for turbomachines where the fluid compressibility is important
- Perform cascade analyses, where relations between flow properties and lift and drag coefficients are established
- Analyse the flow field, in terms of both absolute and relative velocity vectors, using the one-dimensional flow field
- Analyse the energy transfer using the Euler pump/turbine equation
- Analyse specific types of turbomachines, using the general techniques described above:
• Centrifugal pumps (radial and axial types)
• Hydraulic turbines (radial and axial types)
• Axial gasturbines
• Compressors (radial and axial types)
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Course description/ contents:
An introduction is given to the subject of turbomachines. Similarity considerations are explained for scaling the performance of hydrodynamic turbomachines, as well as for turbomachines in which the fluid compressibility plays a role. The specific speed of a turbomachine is defined. It is shown how it is directly related to the duty at which the turbomachine works optimally. The phenomenon of cavitation and its relevance to centrifugal pump and hydraulic turbines is explained. The one-dimensional flow model is developed as a simple way of describing the flow field in turbomachines. The velocity triangles are established that connect the absolute velocity vector, the relative velocity vector and the blade speed. The Euler pump/turbine equation is derived as the central equation for understanding and analyzing the energy transfer in turbomachines. Rothalpy as a convenient, conserved quantity in rotating systems is derived. The two-dimensional cascade technique for expressing the flow field, and hence the performance, in terms of lift and drag coefficients is given.
The general principles for turbomachines that have been outlined are applied systematically to the most important classes of turbomachines:
· Centrifugal pumps and fans
o axial type
o radial type
· Hydraulic turbines
o Pelton wheels
o Kaplan turbines
o Francis turbines
· Axial gasturbines.
· Centrifugal compressors
o axial type
o radial type
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