Turbomachinery. Fundamentals, Selection and Preliminary Design

The book is divided into eight chapters. Chapter 1 is an introductory chapter and is a synthesis of the book titled Lecture notes on Fluid Machines—M. Gambini, M. Vellini (in Italian), 2007, adopted for the Turbomachinery and Energy Systems courses for students of the bachelor’s Degree in Mechanical and Energy Engineering of the University of Rome Tor Vergata. This chapter intends to provide a summary of the basic principles of thermodynamics and fluid-dynamics applied to turbomachinery necessary to define all the performance parameters (work transfer, isentropic and polytropic efficiency, nozzles and diffusers efficiency, degree of reaction and so on) used in the proposed procedures of turbomachinery selection and design. Chapter 2 concerns the selection process of the turbomachine configuration (radial, mixed flow, axial) to be used in a specific application defined by the operating conditions (type of fluid, mass flow rate, pressure and inlet temperature, outlet pressure). This selection process is based on the application of the similitude theory, which allows to “capitalize” all previous experience in the turbomachinery sector by transferring the results obtained for an existing machine, considered as a model, to another machine, to be designed, which is “similar” to the model one, used as a reference. The following chapters, from Chaps. 3 to 7, explain the preliminary design procedures of the five turbomachinery configurations here considered: axial turbines (Chap. 3), axial compressors (Chap. 4), radial turbines (Chap. 5), centrifugal compressors (Chap. 6) and centrifugal pumps (Chap. 7). The book ends with a chapter (Chap. 8) entirely dedicated to numerical applications of the proposed procedures for the selection and preliminary design of turbomachines. In particular, the concentrating solar power (CSP) sector has been chosen as a case study, for which several unconventional conversion cycles are proposed: closed Brayton cycles operated with helium, argon, supercritical CO2 (sCO2), also in combined arrangements with bottoming cycles operated with organic fluids (ORC). When defining the thermodynamic cycle of each power block, preliminary hypotheses on the turbomachinery efficiencies must be made. These hypotheses must necessarily be verified through the calculation of the turbomachine losses, which, in turn, requires assessing of the kinematics, thermodynamics and geometry of the turbomachine (Chaps. 3–7). In fact, only if these hypotheses are validated, the reliability of the calculation of the cycles’ performance is ensured.