Axial Turbines

Turbines may be defined as turbomachines that extract energy from the fluid and convert it into mechanical/electrical energy. Axial gas flow turbines constitute the primary power-producing components of modern aircraft engines and industrial gas turbines, operating under extreme aerodynamic and thermal conditions that demand high efficiency, durability, and reliability. Axial gas turbines may be either reaction or impulse. Also, they may be subsonic or supersonic turbines. This chapter presents a comprehensive treatment of axial gas turbine technology, encompassing one-dimensional (mean-line) and three-dimensional aerodynamic design by considering the variation of flow from the blade hub to its tip in addition to considering the loss mechanisms and the thermal and structural constraints that govern blade cooling strategies. Internal and external cooling techniques—including convection, impingement, film cooling, and transpiration—are discussed in relation to their impact on aerodynamic performance, mixing losses, and life-limiting metal temperatures. The chapter further examines the emerging role of artificial intelligence and data-driven methods in turbine design and operation, highlighting applications in aerodynamic optimization, cooling effectiveness prediction, performance monitoring, and digital twins. A second-law framework based on exergy analysis is employed to quantify irreversibility and to attribute losses systematically between stator and rotor blade rows, cooled and uncooled regions, and aerodynamic and thermal processes. By integrating classical turbine theory with advanced cooling concepts, exergy-based performance assessment, and AI-enabled design methodologies, the chapter provides a unified perspective on the analysis and optimization of axial-flow turbines for next-generation propulsion and power-generation systems.