This study numerically investigates the application of conical film cooling holes on turbine blades. Four rows of conical holes are strategically placed at critical cooling-weak regions (mid-chord/trailing edge of pressure side and leading edge of suction side) of an impingement-slot cooled blade. The effects of blowing ratio (Br), exit area ratio ( A ₁ / A ₂ ), and tapered section length ratio ( L _E / L ) are systematically analyzed. Results demonstrate that increasing the exit area ratio enhances the film cooling effectiveness (>150 % improvement at A ₁ / A ₂ = 2) by reducing the jet momentum and promoting wall attachment. Optimal cooling performance is achieved at L _E / L = 1/3, where vortex suppression improves coolant coverage, particularly at higher blowing ratios. Conversely, excessive expansion ( L _E / L > 2/3) induces the flow separation, degrading the cooling performance. The study reveals that conical holes with moderate expansion ( A ₁ / A ₂ = 2 , L _E / L = 1/3) achieve superior cooling effectiveness while maintaining manufacturing feasibility, providing practical insights for turbine blade cooling design.

Air-breathing electric propulsion enables sustained operation in very low Earth orbit by using in situ atmospheric gases as propellants. Radio-frequency ion thrusters operated with nitrogen–oxygen mixtures generate multiple ionization products, making single-species thrust calculations inadequate. In this study, an RIT-13 thruster was experimentally investigated under different nitrogen-to-oxygen flow ratios and RF powers to characterize ion beam behavior and ionization-product composition. Residual gas analysis was used to identify the discharge products. To resolve the overlap of N₂ and CO related signals at m/z = 28, a composition reconstruction method based on Dalton’s law of partial pressures and nitrogen/oxygen atom conservation was developed. The reconstructed composition was incorporated into a multi-component thrust model by summing the contributions of individual ion species. Results show that the nitrogen-to-oxygen ratio strongly affects the ion beam composition, while RF power mainly adjusts the relative species fractions. Increasing oxygen fraction shifts the beam from N₂⁺ dominance toward multi-component coexistence involving O₂⁺, O⁺, and NO⁺. Calculated thrust agrees with direct measurements, with relative errors below 5% under all tested conditions. The method provides a practical basis for thrust prediction of air-breathing radio-frequency ion thrusters.

Conventional turbine blade cooling technologies are approaching their performance limits and may become insufficient to provide adequate thermal protection under increasingly demanding operating conditions. As a novel and highly efficient cooling technology, transpiration cooling of ceramic matrix composites (CMC) still lacks a systematic understanding of its film coverage characteristics in naturally non-uniform porous structures. To address this issue, pressure sensitive paint (PSP) measurements are performed to characterize the transpiration cooling performance on a SiCf/SiC 2.5D woven CMC flat plate. The effects of pore structure, injection ratio, and mainstream direction on film coverage are analyzed, and an evaluation is conducted on the correlation between film and overall cooling effectiveness. Experimental results show that pore structure largely determines how film cooling effectiveness distributes on the surface, with inter-bundle pores serving as preferential transport pathways for the coolant. The mainstream direction shows a strong coupling relationship with transpiration cooling, and the film cooling effectiveness varies between 21% and 32% in different flow directions. An increase in the injection ratio leads to higher film cooling effectiveness, yet the growth tendency slows down progressively. Such increment in film cooling effectiveness yields a local improvement in overall cooling effectiveness. However, the enhancement of overall cooling effectiveness mainly relies on the convective heat transfer within the porous medium. This understanding helps improve the design and engineering application of CMCs.

Systematic experimental characterization of the electron extraction characteristics of a radio-frequency plasma bridge neutralizer (RPN) in the actual ion-plume environment of a radio-frequency ion thruster (RIT) remains limited, particularly regarding the effects of ion-beam conditions and the relative configuration between the RIT and RPN. In this study, an experiment consisting of an RIT-13 and an RPN-2.5 was established, in which the RIT-13 operated with an Xe + N₂ + O₂ mixed propellant and the RPN-2.5 operated with Xe. Experimental investigations were conducted to systematically examine the effects of collector bias voltage, ion beam current, screen-grid voltage, RPN installation angle, and spatial position on electron extraction. The results show that the collector bias voltage is the primary parameter governing the electron extraction state, and two distinct jumps occur as the magnitude of the negative collector bias voltage increases, while the ion beam current mainly modulates the electron extraction state near the threshold of the first jump. The 60° and 90° configurations generally exhibit stronger electron extraction capability than the 0° and 30° configurations and require smaller magnitudes of negative collector bias voltage to reach the high-current electron extraction state. A pronounced spatial dependence is also observed. At an ion beam current of approximately 440 mA and a screen-grid voltage of 1200 V, the region of X = −10 mm and Y = 20–40 mm exhibits favorable electron extraction characteristics. Among the investigated configurations, the 90° configuration at (−10, 40) mm requires the smallest magnitude of collector bias voltage, approximately 13.5–14 V, for the RPN electron extraction current to match the RIT ion beam current. This current-matching bias is defined in the present study as the equivalent floating potential U_eq. These results provide an experimental basis for the matching design and spatial configuration of RITs and RPNs in an air-breathing electric propulsion system.