Visualization methods have always been used to inspect flows that are invisible to the naked eye. Seedless velocimetry has been regarded as an alternative to other intrusive quantitative methods and adapted to fit many applications in the industrial or scientific field. Schlieren image velocimetry (SIV) uses the general working principle of a schlieren system to acquire flow images, while relying on a particle image velocimetry (PIV)-like algorithm to obtain quantitative data related to the studied flow. The test case of this study consists of a turbulent round exhaust jet generated by a micro-thruster that uses ${\mathrm{H}}_2-{\mathrm{O}}_2$ as a propellent. Mapping the local velocities of the flow is achieved by initially performing a lagrangian tracking method which makes use of a direct image correlation algorithm. These results are then compared to the velocity map obtained from a kymograph applied to a series of images. The velocity profiles obtained through SIV will be compared to the velocity profile of the jet provided by the CFD simulation. The schlieren investigation of the jet’s local velocity map is set to determine the thruster’s capabilities, and conclude if the thruster reaches the desired Mach for which it has been designed.

This paper describes the effort of designing an unconventional exhaust manifold for a marine gas turbine engine, with an integrated passive ventilation port for cooling the engine housing. The study is part of a larger program to substitute the propulsion gas turbines for the T22R defense frigate and make the proper aerodynamic adaptations. The system in question is unique, in the sense that it uses the exhaust gas momentum to entrain outside air and ventilate the engine enclosure. In achieving this, RANS computation was used to test various concepts and dimensions for the ventilation system. Based on these analyses, the design that provided adequate air circulation with minimum pressure losses was chosen and the parts were integrated in the overall assembly. The experimental campaign performed on the entire aero-package showed good synergies of the ventilation system with the other adaptations and the engine itself. Performance was evaluated with pressure and temperature probes distributed around the aero-package and were found to be within 3.5% of the data predicted by CFD. This brings further studies closer to a technology readiness level vital for insitu testing on board the ship itself.

During service, a turbine engine undergoes frequently dynamic operations. Because of the changes in mass flow, temperature, pressure, as well as the different reaction of the components of turbine to these changes, the turbine performances may vary significantly. It is critical to understand and quantify these variations to design and integrate the turbine to the engine. This paper presents a study of the performances and the variation of the performances for an axial gas turbine across its operating envelope. Numerical simulations are used to describe the flow across the turbine and to estimate the turbine maps. Using theoretical charts for typical turbine thermal expansion, the variation of tip clearance across the working line is approximated. Because of the changes of the tip clearance, using a single geometry may not supply relevant information during real dynamic operations. In order to eliminate these additional errors in the numerical study, a number of turbines maps are recalculated for different tip clearances, respectively to engine regimes. With the resulting data, the working line is recalculated across multiple maps. The comparison between the two working lines is presented as well as the study of performance variation of the turbine across the operation envelope and the influence of tip clearance at different regimes.

A Type 22 Broadsword class of frigate uses a combined gas or gas (COGOG) propulsion system that utilizes four different gas turbines, depending on the mode of operation. Its twin ST40M cruise gas turbines are operational most frequently, and an increase in their efficiency would significantly impact fuel usage and ship range. This study evaluates the option to upgrade the cruise gas turbines to a combined gas turbine–electric and steam (COGES) system, which utilizes a steam Rankine cycle to recover energy from the exhaust gases of the gas turbine. An alternative system using hot air is also analyzed for performance comparison. The analysis contains calculations for the energy extraction and dimensions of heat exchangers, for the power extracted from the additional steam or air turbine and for pressure losses of the exhaust gas. Different configurations for the heat exchangers were investigated, as well as various parameters for the steam and hot air. The size and mass of the system were an important aspect of the analysis. It was concluded that an auxiliary system operating at a maximum steam pressure of 20 bar could generate an additional 771 kW of power while adding a mass of 7.4 tons to the frigate. These findings suggest that upgrading to a COGES system could cover the electricity needs of the entire ship and thus reduce the overall fuel consumption, resulting in lower operational costs and less emissions.

The paper presents the thermodynamic analysis for changing the fuel of an aviation gas turbine from kerosene to alternative gaseous fuels. Theoretical results are obtained using the CEA program and the numerical ones using a commercial CFD code. The gas turbine used for the application is a helicopter turboshaft for which the geometry of the combustor was carefully reproduced in a CAD environment. The paper details each necessary step to obtain the numerical results, as well as some comparison with experimental data. The conclusions are related to the similarities and the differences between the presented numerical results, considering the complexity of the entire gas turbine. A series of development perspectives are presented.

Building on the previous theoretical parametrisation of oblique detonation wave (ODW) stability limits for hydrogen–oxygen mixtures, the present work advances the investigation by combining CFD analysis with the complete mechanical design of a planar ODW test bench. While the earlier study established feasible inflow conditions and wedge-angle ranges through detonation theory and oblique shock relations, the current work focuses on the numerical characterisation of ODW-relevant flow fields and the constructive development of the experimental facility. CFD simulations were performed for seven wedge deflection angles to assess shock formation. A key finding is the identification and systematic characterisation of a recirculation-induced secondary deflection mechanism, which emerges for wedge angles above ~20°. The recirculation zone forms an effective secondary wedge whose boundary angles remain nearly constant, thereby altering the resulting shock angle and explaining the deviation from classical oblique-shock predictions. This behaviour was quantified through velocity-component sampling and shown to be consistent across multiple geometries. Based on the numerically optimised configuration, the full 3D design of the test bench is developed, including diagnostics integration, sealing solutions, and a modular wedge system enabling rapid geometry replacement. By linking theoretical analysis, numerical validation, and experimental design, the study establishes a robust foundation for forthcoming ODW experiments and contributes to the development of pressure-gain combustion concepts for rocket-type propulsion.