Pressure gain combustion is a promising alternative to conventional gas turbine technologies and within this class the Rotating Detonation Engine has the greatest potential. The Fickett–Jacobs cycle can theoretically increase the efficiency by 15% for medium pressure ratios, but the combustion chamber delivers a strongly non-uniform flow; in these conditions, conventionally designed turbines are inadequate with an efficiency below 30%. In this paper, an original mean-line code was developed to perform an advanced preliminary design of a supersonic turbine; self-starting capability of the supersonic channel has been verified through Kantrowitz and Donaldson theory; the design of the supersonic profile was carried out employing the Method of Characteristics; an accurate evaluation of the aerodynamic losses has been achieved by considering shock waves, profile, and mixing losses. Afterwards, an automated Computational Fluid Dynamics (CFD) based optimization process was developed to find the optimal loading condition that minimizes losses while delivering a sufficiently uniform flow at outlet. Finally, a novel parametric analysis was performed considering the effect of inlet angle, Mach number, reaction degree, peripheral velocity, and blade height ratio on the turbine stage performance. This analysis has revealed for the first time, in authors knowledge, that this type of machines can achieve efficiencies over 70%.

The renewed interest in supersonic turbomachinery research was driven by its potential applications in emerging fields. However, the design of supersonic inlet cascades faces significant challenges due to the inherent limitations of supersonic flows. While several studies have been published on the unstarting of supersonic intakes, there exists a major knowledge gap in the unstarting of supersonic blade rows. This paper presents the research on a novel unstarting mechanism for supersonic inlet cascades induced by the formation of a collective shock. Tailored simulations were carried out to study the coalescence of the leading-edge bow shock waves and to investigate the stability and the hysteresis of this phenomenon. Then, a reduced order model was developed and verified to estimate the limit induced by this additional unstarting mechanism. Since the accuracy of the unstarting condition relies heavily on the predicted bow shock shape, novel strategies were proposed to improve the estimate of the asymptotic slope of the bow shock and to account for large incidence angles. Furthermore, the well-known Kantrowitz criterion for the self-starting of a supersonic channel was reviewed and adapted to supersonic blade rows by considering both weak and strong oblique shock waves in the calculation of the maximum contract ratio. Then, it was demonstrated the importance of accounting for shock-induced boundary layer separation in the starting process of a supersonic machine. Finally, computational fluid dynamics simulations reveal the high sensitivity of the self-starting limit to the cascade solidity and profile shape.

A rotating detonation combustor (RDC) is an innovative technology with the potential to improve the efficiency of modern gas turbines. However, the highly unsteady and transonic flows generated by RDCs require advanced turbine designs, such as supersonic inlet turbines, to fully realize their benefits. This paper presents the first large eddy simulation of a complete supersonic turbine stage operating with RDC-representative inlet conditions. The investigation begins by evaluating the accuracy of Reynolds-averaged Navier–Stokes (RANS) simulations, widely employed for designing and optimizing supersonic inlet turbines. The strengths and limitations of RANS in capturing the complex flow physics of such systems are revealed. Aerodynamic losses within the turbine are quantified and compared with predictions from established mean-line design loss models. An entropy decomposition framework is then applied to uncover the dominant physical mechanisms of entropy generation and to identify regions of peak entropy production. The impact of RDC wave propagation through the stator and rotor blade rows is analyzed through phase–phase diagrams of phase-locked-averaged quantities, revealing key unsteady flow interactions. Additionally, the dominant modes characterizing the flow separation on the stator's suction side are detected with dynamic mode decomposition, and an accurate reduced-order model is developed with the state-of-the-art shallow recurrent decoder neural network. This work provides critical insights into the aerodynamic performance, loss mechanisms, and unsteady flow phenomena of supersonic inlet turbines in a rotating detonation engine (RDE). These findings pave the way for the practical implementation and continued advancement of RDE-integrated turbine technologies.