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.

In Chapters 3 and 4, we studied major changes in the flow thermophysical properties as it traverses a turbine or compressor stage. The analysis, then, was one-dimensional, with the underlying assumption that average flow properties will prevail midway between the endwalls. Categorized as a pitch-line flow model, this “bulk-flow” analysis proceeds along the “master” streamline (or pitch line), with no attention given to any lateral flow property gradients.

The primary assumptions and formulations for single-phase flow regimes are reviewed in this chapter. This includes the governing partial differential equations for general fluid dynamics (mass, momentum, energy, and species), equations of state and associated flow regimes, rotational effects and the stream function for incompressible flow, and viscous effects with the Reynolds number, including flow instability mechanisms.

This chapter develops the point-force Equations of Motion for a single spherical particle moving in an unbounded fluid. This includes the particle Equations of Motion, which are considered as a sum of pointwise forces. The drag force is described for solid and fluid particles for Reynolds numbers ranging from creeping flow to turbulent flow. The three acceleration forces of added-mass, fluid-stress, and history forces are explained, and all the forces are combined to provide various Equations of Motion. Finally, heat and mass transfer effects on the particle are discussed.

This chapter provides an overview of the key elements of turbulent flow. First, the basic averaging approach and examples of turbulent flow decompositions are discussed. Using these techniques, the average transport equations for mass, momentum, and species with closure models are given, followed by advanced numerical techniques for turbulent flows. Turbulent time and length scales as well as the kinetic energy cascade are overviewed, and theoretical turbulent species diffusion is treated.

This chapter considers the drag force for velocity gradients in the surrounding fluid, particle Mach number and Knudsen number, temperature gradients in the surrounding fluid, particle spin and fluid vorticity, flow turbulence and particle roughness, shape for a solid particle, surface contamination and internal recirculation for a spherical fluid particle, and deformation and drag for a fluid particle. This includes theory, experimental results, and numerical prediction of the drag coefficient for point-force models.

This chapter identifies systems where dispersed multiphase flow is important as well as the key fluid physics via important engineered and natural systems. This includes energy systems and propulsion systems, manufacturing, processing and transport systems, as well as environmental and biological systems. In addition, this chapter sets forth key terminology and assumptions for dispersed multiphase flow, the key velocity reference frames used for multiphase flow, and the assumption of continuum conditions.