Rolls-Royce (United Kingdom)

Sm2TM17 sintered magnets, (where TM = Co, Fe, Cu, Zr), are typically utilised in high temperature magnetic applications due to their magnetic properties being very stable at 200-350 °C. Sm and Co are critical materials and need to be recycled to reduce reliance on virgin material supply chains. This work explored HD processing of Sm2TM17 sintered magnet production scrap as a potential recycling technique. Sintered magnet scrap was initially analysed compositionally, microstructurally and magnetically to determine issues with magnet quality. Scrap material was then HD processed at 18 bar and 2 bar at temperatures between 25-300 °C. The resultant material was characterised in terms of hydrogen content, particle size, degassing behaviour and unit cell expansion. Production scrap magnets exhibited irregular demagnetisation traces with poor domain wall pinning behaviour. Non-magnetic ZrC inclusions likely prevented cell structure formation locally and hence were poor domain wall pinning sites. Scrap material processed at 18 bar and 2 bar required temperatures of 100 °C to allow for the greatest extent of HD reaction, reaching 0.299 Wt.% and 0.323 Wt.% hydrogen respectively. The HD behaviour of production scrap material was comparable to commercial grade magnets. Therefore, HD is a potentially viable technique for recycling Sm2TM17 sintered magnet production scrap.

Abstract A novel co-rotating, synchronous, reverse flow (RF) turbine mode operation in a centrifugal compressor (CC) is investigated, and methods to enable this mode, its working principles, flow field features, and key performance characteristics are described. This is done by using three-dimensional (3D) Reynolds–averaged Navier–Stokes (RANS) flow field simulations on a simplified variant of the NASA High Efficiency Centrifugal Compressor (HECC) geometry, which represents a typical state-of-the-art design practice. The novel co-rotating turbine mode is elucidated by first considering the baseline contra-rotating, reverse flow turbine mode as would be expected from the conventional four-quadrant CC operation map. This baseline contra-rotating turbine mode is also hitherto undescribed in the literature for CC. Therefore, the flow field and performance metrics in the baseline contra-rotating mode are utilized to provide insights into the possibility of engineering design elements that can enable the novel co-rotating turbine mode. The novel co-rotating, turbine mode is found to be enabled by the introduction of a suitable swirl generation mechanism that will direct the flow onto the impeller wheel suction side to give it a rotational impulse to spin from the suction to the pressure side as in nominal operation. The flow expansion through the reversed impeller wheel flow path with radius reduction enables power production. In the novel co-rotating, turbine mode, the flow leaves the impeller wheel in the same direction as it enters because of the direction of rotation and impeller inlet flow angle. However, this does not significantly impact power production because of the reduced radius weighting of the absolute swirl at the impeller inlet. An exemplary co-rotating turbine mode enabling configuration with 45 deg rotated diffuser vanes is found to handle up to 46% higher reverse flow and yield 6.25% higher peak power output even with a 16% lower absolute swirl velocity change as compared to the baseline contra-rotating mode. Additionally, the novel mode indicates better low speed power profile and wheel terminal speed as well. Alternative embodiments to enable the co-rotating mode like drilled feed ports and guide vane arrangements are discussed in the work. The hitherto undescribed co-rotating turbine mode operation is unique in its ability to produce and absorb power in the same shaft for bladed turbomachinery. Therefore, purposeful utilization of this mode could enable the design of better, robust, optimized systems for aerospace and energy applications.

Abstract This work investigates the effect of alloying elements Mn, Si, and Fe on the corrosion resistance of polycrystalline Ni-based superalloys, at $$700\,^{\circ }{\hbox {C}}$$ 700 ∘ C in air and 300 vpm $${\hbox {SO}}_{2}$$ SO 2 under 5 $${\mu {\hbox {g}}}\,{{\textrm{cm}}^{2}\,h}$$ μ g cm 2 h salt coating. Oxide scale morphology and composition was investigated using SEM–EDX and APT, revealing Mn–Fe-enriched $${\hbox {Co}}_{3}{\hbox {O}}_{4}$$ Co 3 O 4 particles in the upper outward growing scale as well as Si-Fe-enriched clusters in NiO. Along the NiO– $$ {\hbox {Co}}_{3}{\hbox {O}}_{4} $$ Co 3 O 4 phase boundary, a tight network of Fe-decorated dislocations relieving stress between the lattices was identified through APT. In the inward growing scale, Si enrichment was observed in the form of oxides and sulfides, while no Mn was detected. Graphical Abstract

Abstract The characterization and quantification of runway foreign object ingestion (FOI) at the end of the landing run with a variable pitch fan (VPF) in reverse thrust mode are described in this work. This is achieved by developing a novel, fully coupled computational fluid dynamics—discrete phase model (CFD-DPM) methodology that allows the tracking of individual debris, which is placed on the runway. The flow field solutions are computed by the three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) equations, and the particulate phase is tracked in a Lagrangian way. A modern 300-seater aircraft is considered to feature a high bypass ratio geared turbofan engine architecture on a conventional twin-engine airframe in landing configuration that rolls on the runway at low speeds and a typical high engine power mode. The aerodynamic reverse thrust flow field at such low aircraft speeds is characterized by the development of a “horseshoe” vortex formed in front of the engine that significantly affects the debris trajectories. Based on this, two FOI mechanisms are identified and discussed in detail in the paper. The effect of key debris properties on FOI percentage, such as size, material density, and shape, are investigated and reported. Nonlinear, nonintuitive trends are obtained due to the two-way interaction of flow features and particles. Moreover, a nondimensional analysis that accounts for the changes in debris variables of interest is presented and provides general trends for aircraft with a VPF as the main thrust reversal unit. Generally, debris ingestion increases with lower aircraft speed and debris material density. The benefits of having a VPF are highlighted since it acts as an additional “protective layer” to the engine core and stops and redirects incoming debris from the nominal intake. The assessment of ingestion of foreign objects in realistic end-of-landing-run conditions as described in this study is important to examine the feasibility of reverse thrust-capable VPF engines for future sustainable aircraft.

Intermetallics are a key material class toward high-temperature applications, as monolithic materials such as B2 NiAl, or when used as a precipitate reinforcing phase within Ni fcc-superalloys or nascent bcc-superalloys and refractory high entropy superalloys. There is large variability across B2 ordered-bcc intermetallic compounds in terms of strength and ductility, which is underpinned by variability in their dominant slip systems. Here we have developed an automated indentation-based slip trace analysis method, designed to accelerate the assessment and quantification of favoured slip systems. The methodology uses microhardness indentation and imaging of the resultant surface slip traces, paired with local crystal orientations determined by Electron Backscatter Diffraction (EBSD). Our newly developed code for automated detection of slip trace orientations then uses image segmentation, Hough transform line detection, and a scoring procedure that evaluates how likely detected lines are to be aligned with real slip traces. This simply applied methodology is validated on fcc nickel, and then used to determine the slip behaviours of four bcc/B2 materials, finding unambiguous evidence of ½<111> {112} and/or {123} type slip in bcc Fe and B2 Ti 2 AlNb, compared to slip predominantly on {110} in B2 TiFe and Ti 2 AlMo, which correlates to their respective apparent ductile/brittle behaviours. The methodology can readily be adapted to other testing techniques (e.g. nanoindentation, tensile), and to gain deformation behaviour insights for other crystal structures (e.g. hcp and complex intermetallics). • New ‘Rapid Analysis of Slip Traces’ (RAST) code developed. • Code applied to indentation slip behaviour of fcc Ni, bcc Fe & intermetallics. • Code validated for <110> {111} Nickel. • Code confirms <111> type slip in Fe & Ti 2 AlNb & {110} dominant slip in TiFe & Ti 2 AlMo.

Abstract This paper aims to establish the cycle design implications for turbofan engines that will be powered by hydrogen and ammonia. Appropriate methodologies are employed to address the identified research questions. A comprehensive turbofan design space exploration is performed for hydrogen and ammonia. An evaluation of engine size and weight is carried out for both hydrogen and ammonia, with the support of three distinct turbofan design strategies. The impact of fan size (specific thrust) on the cycle design of turbofan engines powered by hydrogen and ammonia is assessed. The turbofan design opportunities when powered by hydrogen across aircraft category is explored. The impact of fan size and the cryogenic tank technology on a hydrogen aircraft is investigated. It is identified that hydrogen and ammonia offered three main turbofan design opportunities. Hydrogen and ammonia significantly affects the engine size, weight, and operating temperatures based on the design strategy selected. With similar ESFC breakpoints for very low specific thrust values, hydrogen and ammonia showcases significant departure in bypass ratios (BPRs) from kerosene for all ranges of fan sizes. Hydrogen offers significant turbofan redesign opportunities across aircraft category (short medium range (SMR) and long range (LR)). Cryogenic tank technology is a major design driver for both hydrogen turbofan and aircraft mission energy burn.

There exists numerous techniques for connecting an aircraft’s power plant to its supporting structure, the pylon, and for connecting the pylon to the wing. This paper investigates how two connection strategies employed in wide body commercial aircraft with fan mounted and core mounted power plants affect the sizing of the wing and pylon for the same loading. Sizing of the pylon in isolation is investigated and compared to results for when sized with the wing. Eighty-eight load cases, including flight, landing and those generated by the power plant are selected for the sizing studies. Static aeroelastic analysis of a reduced order aircraft model provides the flight loads. Free sizing the thickness of components is then performed. Results show that the sized pylon and wing with connections for a fan mounted power plant system are 1.7% lighter than that for a core mounted system. Pylons sized with the wing for fan and core mounted power plants are found to be 10.3% and 12.7% heavier than those sized in isolation. These investigations contribute towards wider work to develop whole aircraft models for static and dynamic aeroelastic analysis, to support combined aircraft and engine design.