In this chapter, the flow-governing equations (conservation laws) are reviewed, with applications that are purposely turbomachinery related. Particular emphasis is placed on the total (or stagnation) flow properties. A turbomachinery-adapted Mach number definition is also introduced as a compressibility measure of the flow field. A considerable part of the chapter is devoted to the total-relative properties, which, together with the relative velocity, define a legitimate thermophysical state. Different means of gauging the performance of a turbomachine, and the wisdom behind each of them, are discussed. Also explored is the entropy-production principle, as a way of assessing the performance of turbomachinery components. The point is stressed that the calculation of entropy production may indeed be desirable, for it is the only meaningful performance measure that is accumulative (or addable) by its mere definition.

This chapter lists the acronyms used in the text, the heat and mass balance software used for numerical examples, and key concepts to evaluate the technical and commercial viability of novel technologies.

This chapter explains the background behind the book concept, e.g., the meaning of sustainability within the electric power generation context, energy transition, and decarbonization. Technologies that are covered in the book are described in brief. The concept of operability and how it pertains to the main theme of the book is addressed.

From a historical viewpoint, the centrifugal compressor configuration was developed and used, even in the propulsion field, well before axial-flow compressors were. Due to their large envelope and weight (Figure 11.1), the common belief that such a “bulky” compressor type has no place except in aerospace applications is not exactly accurate. For example, with a typical total-to-total pressure ratio of, for example, 5:1, it would take up to three axial-compressor stages to absorb similar amounts of shaft work that a single centrifugal compressor stage would. In fact, the added engine length, with so many axial stages, would increase the skin friction drag on the engine exterior, almost as much as the profile drag, which is a function of the frontal area.

While coal seems to be out of the picture in the energy transition, there are technologies that make sustainable use of this abundant resource. This chapter covers several technologies, i.e., gasification, magnetohydrodynamics, and coal slurry, which, when combined with carbon capture, can make this a reality.

This chapter covers the basics of energy storage, i.e., why it is needed, when it is used, how it is used, its benefits, and the types of energy storage technologies. Special attention is given to thermal energy storage due to its usage in a variety of guises in renewable power applications.

Sometime around 2010 and thereafter, trade publications and archival journals were inundated with articles and papers filled with hyperbole and lofty claims about the closed cycle sCO2 turbines and their merits. In particular, sCO2 cycle/turbine was/is touted as a technology that can replace Rankine (steam) cycle and steam turbine in conventional fossil fuel-fired power generation, as a stand-alone or as the bottoming cycle of a gas turbine combined cycle. In this chapter, performance of sCO2 in power generation applications (including the Allam cycle) is rigorously assessed with in-depth thermodynamic analysis and cycle data. Furthermore, we will also look at the operability challenges presented by the unique structure of the sCO2 powertrain and heat exchangers.

A brief introduction to gas turbine engines was presented in Chapter 1. Review of the different engines included in this chapter reveals that most of these engine components are composed of “lifting” bodies, termed airfoil “cascades,” some of which are rotating, while others are stationary. These are all, by necessity, bound by the hub surface and the engine casing (or housing), as shown in Figures 2.1–2.5. As a result, the problem becomes one of the internal-aerodynamics type, as opposed to such traditional external-aerodynamics topics as “wing theory” and others. Referring, in particular, to the turbofan engines in Chapter 1 (e.g., Figure 1.3), these components may come in the form of ducted fans. These, as well as compressors and turbines, can be categorically summed up under the term “turbomachines.” Being unbound, however, the propeller of a turboprop engine (Figure 1.2) does not belong to the turbomachinery category.

This chapter focuses on compressed air energy storage (CAES) technology, which is one of the two commercially proven long-duration, large scale energy storage technologies (the other one is pumped hydro). The chapter covers the basic theory, economics, operability, and other aspects of CAES with numerical examples derived from the two existing plants, Huntorf in Germany and McIntosh in the USA.

Historically, the first axial turbine utilizing a compressible fluid was a steam turbine. Gas turbines were later developed for engineering applications where compactness is as important as performance. However, the successful use of this turbine type had to wait for advances in the area of compressor performance. The viability of gas turbines was demonstrated upon developing special alloys that possess high strength capabilities at exceedingly high turbine inlet temperatures.

Figure 4.1 shows a general-type mixed-flow compressor rotor. The thermophysical states 1 and 2 represent average conditions over the entire inlet and exit stations, respectively. The rotor-blade-to-blade hub-to-casing passage is the control volume, and other than the continuity and energy equations (Chapter 3), we are now left with the momentum-conservation principle to implement.

This chapter outlines the basic knowledge required from the reader in order for them to follow the narrative in the book. Key terms and concepts are introduced with brief descriptions. The chapter also lists books, articles, and papers by the author, which deal with the subject matter covered in the book in a more detailed fashion.

Well-known intermittency and low capacity factors of solar and wind resources prevent these technologies from fulfilling the demands of the energy transition on their own – at least in the near future. They require backup in the form of dispatchable resources, e.g., fossil-fired power plants and energy storage systems. Such systems must be nimble enough to address short-term fluctuations and maintain grid stability in addition to taking over the base load generation when renewable resources are not available. Aeroderivative gas turbines, small industrial gas turbines, gas-fired recip engines, and energy storage systems such as CAES, LAES, pumped hydro (PHS), and electric batteries are readily available technologies that can accomplish these tasks. Large-scale, long-duration systems such as CAES and PHS are discussed elsewhere in the book. Herein, the focus is on BESS and its integration with gas turbines and solar PV.

Over more than three decades now, radial-inflow turbines have been established as a viable alternative to its axial-flow counterpart, specifically in power-system applications. Despite its relatively primitive means of fabrication, radial turbines are capable of extracting a large per-stage shaft work in small mass-flow rate situations. This turbine category also offers little sensitivity to tip clearances, in contrast to axial-flow turbines. Nevertheless, the turbine large envelope, bulkiness, and heavy weight (Figure 10.1) virtually prohibits its use in propulsion devices.

Constant volume combustion (CVC) is the most promising gas turbine cycle option (as opposed to constant pressure combustion in a conventional Brayton cycle) to improve cycle thermal efficiency beyond the present limitations. This chapter covers the underlying thermodynamics and practical methods to achieve CVC (approximately) in field applications, i.e., detonation combustion.