Search Results (324)

This paper presents a concise modeling and simulation study of a turboelectric distributed propulsion (TeDP) system for a hybrid wing body (HWB) aircraft. A whole-system 0D model has been implemented in PROOSIS that includes the thermodynamic model of the turboshaft and fan array, as well as an electrical subsystem model addressing generators, motors, and cryogenic cooling for high-temperature superconducting (HTS) machines. Boundary layer ingestion (BLI) was explicitly modeled in the inlet–fan interaction. Parametric studies explored control strategies that minimized fuel consumption across the flight envelope. The design and off-design analyses demonstrated that coupling BLI with distributed fans can deliver significant aerodynamic benefits, while the integrated mission simulation highlighted the system-level implications of electrical conversion and control and quantified potential fuel savings. Full article

This paper presents the design of shock control bumps on a double-fuselage aircraft with a natural laminar flow (NLF) wing section. Both two-dimensional (2D) and three-dimensional (3D) bumps were investigated to identify the high-impact factors on both shock control and natural laminar flow for the aircraft, and to understand the associated flow physics. Firstly, two key geometric parameters, namely the bump crest location and the bump height, were optimized to trade off shock control and laminar flow. The optimized 2D bump results in 8.19% total drag reduction in the wing section, specifically, 8.61% pressure drag reduction and 6.23% viscous drag reduction. The total drag coefficient of the aircraft reduces by 8.12 counts while the lift slightly increases. Then, the robustness of the bump at off-design conditions was verified as well. Finally, the 2D bump was converted to 3D bumps according to the transonic area rule to explore more alternative designs, and it was found that the two have similar performances, confirming the effectiveness of the transonic area rule applied in the shock-control-bump design. Full article

Reversible pump turbines (RPTs) play a key role in pumped hydro energy storage systems, where increasing grid flexibility requires frequent operation under off-design conditions. In turbine mode, deep partial load and no-load operation are often associated with severe flow instabilities, rotating stall, and strong rotor–stator interactions, which can limit operational flexibility and increase mechanical stress. Previous studies have shown that blade lean can influence hydrodynamic stability; however, its effect under no-load conditions remains insufficiently understood. In this work, the influence of runner blade lean on flow instabilities and rotor–stator interaction in a reversible pump turbine is numerically investigated. Two runner configurations, featuring a 0° and a $-15°$ blade lean angle, are analyzed through unsteady CFD simulations during the transition from deep partial load to no-load operation. The analysis focuses on flow field characteristics, blade loading, and the spectral content of pressure, torque, and radial forces. The results show that the negatively leaned runner significantly mitigates flow recirculation near the hub, reduces pressure and torque fluctuations, and strongly suppresses higher-order harmonic components associated with rotor–stator interaction. In particular, radial force amplitudes at blade-passing harmonics are substantially reduced under no-load conditions. These findings demonstrate that a negative blade lean improves hydrodynamic stability and reduces vibratory loads, contributing to the enhanced operational reliability of reversible pump turbines. Full article

Main engine load varies continuously, whereas onboard carbon capture columns are installed with fixed capacities. For liquefied natural gas (LNG)-fueled ships, this mismatch between design and operation makes off-design robustness, rather than nominal-point performance, the governing sizing criterion. This study developed a variable-load design window for onboard monoethanolamine CO₂ capture and evaluated a dual-loop organic Rankine cycle (ORC) as a secondary thermal integration option. A verified process model was applied to a 5 × 5 design–operating matrix (D50–D90/O50–O90). The mismatch was strongly asymmetric. When operating load did not exceed design load, capture rate remained near 90%; under overload, absorber treated only the design-point-equivalent exhaust-gas flow, causing capture performance to deteriorate rapidly. The mean CO₂ avoided rate increased from 57.4% at D50 to 70.4% at D90, while absorber diameter increased from 3.23 to 4.06 m. D70 emerged as the balanced option for low- to medium-load services, D80 marked the transition before full robustness, and D90 was robustness-oriented for frequent high-load operation. The ORC recovered 104–185 kW net power and supplied 231–410 kW LNG-side heating. Results support capacity selection before ORC application; CO₂ liquefaction and storage, voyage-weighted validation, and shipboard ORC feasibility remain outside the present scope. Full article

Heat exchanger integration is a key design consideration for engines adapted to run on hydrogen and requiring liquid hydrogen to be preheated prior to combustion. For a typical small turboshaft, a comparison is made of fuel heating via an intercooler, a recuperator, or both in combination. This steady-state, zero-dimensional thermodynamic assessment examines the overall performance effects of the heat exchanger installations, heat loads and setpoint temperatures. It shows that exhaust gas recuperation provides up to 15% SFC reduction relative to an engine using power offtake for fuel preconditioning, with an average reduction of 14% across the evaluated operating points. Fuel heating via an intercooler is constrained by off-design and low-temperature thermal management requirements, so it only gives modest SFC benefits and will reduce specific power unless the engine is substantially redesigned. Within the evaluated design space, the combined intercooled and recuperated arrangement does not provide the lowest SFC, but it offers a balanced heat load distribution that may help to mitigate the risk of local air-side icing in the heat exchangers. Unlike previous works that considered turbofan engine architectures, this study focuses on turboshaft and turbogenerator installations where shaft power objectives and operating constraints determine the relative merits of alternative heat exchanger integration strategies. It includes an assessment of potential effects on NOx emissions as well as SFC. The study provides guidance for preliminary design and sizing of heat exchangers for fuel thermal management, but analysis of transients in the cryogenic systems and detailed assessments of aircraft-level integration penalties will be specific to particular engine applications and are beyond the scope of the present study. Full article

As thermal power units in China shift toward serving as flexible regulation sources in new-type power systems, accurately assessing the axial thrust of steam turbine regulating stages under off-design conditions has become critical. This paper employs numerical methods to investigate the axial thrust characteristics and nozzle structural optimization of the regulating stage under off-design conditions (VWO, THA, 75% THA, 50% THA). Steady-state results reveal significant deviations in the interstage hub forces predicted by 3D simulations compared with those from the conventional 1D formula under partial admission, prompting a correction. Unsteady results show that reducing the partial admission degree intensifies flow unsteadiness, increasing rotor blade axial force fluctuation from 1175 N (VWO) to 2057 N (50% THA). In terms of structural optimization, compared with not increasing the nozzle angle, increasing the nozzle angle by 2° reduces the total axial force on the regulating stage by 7.3%; compared with not extending the inlet guide arc segment, extending its length by 40 mm increases the axial force on the rotor blade by 1.6%, but decreases the maximum amplitude from 323.9 to 249.9. Based on these findings, the optimization direction for the nozzle structure is proposed. Full article

Vertical axis wind turbines (VAWTs) have regained attention for distributed, urban, and floating offshore applications, yet the literature remains fragmented across competing rotor concepts and modelling traditions. This review consolidates the principal archetypes—Savonius, H-Darrieus, troposkein Darrieus, helical Darrieus, and Savonius–Darrieus hybrids—through five governing parameters: drag-versus-lift-driven operating principle, tip speed ratio $\mathsf{\lambda }=\mathsf{\omega }\mathrm{R}/{\mathrm{V}}_{\infty }$ (0.6–1.2 for Savonius; 2.5–5.0 for Darrieus), solidity $\mathsf{\sigma }=\mathrm{N}\mathrm{c}/\mathrm{R}$ (0.1–0.4), chord-based Reynolds number ${\mathrm{R}}_{\mathrm{e}\_\mathrm{c}}$ (${10}^5–{10}^6$), and peak power coefficient ${\mathrm{C}}_{\mathrm{p}\_\mathrm{m}\mathrm{a}\mathrm{x}}$ (0.15–0.25 for Savonius; 0.35–0.45 for optimized H-Darrieus). Off-design performance is dominated by unsteady mechanisms that quasi-steady streamtube models cannot resolve—leading edge vortex shedding, dynamic stall hysteresis, blade–wake interaction, and flow-curvature-induced virtual camber—each examined for its contribution to the instantaneous torque ${\mathrm{C}}_{\mathrm{T}}\left(\mathsf{\theta }\right)$ and the cycle-averaged ${\mathrm{C}}_{\mathrm{p}}$. Turbulence closures are benchmarked against phase-locked PIV and torque measurements: $\mathrm{k}–\mathsf{\omega }\mathrm{S}\mathrm{S}\mathrm{T}$ URANS captures peak-region ${\mathrm{C}}_{\mathrm{p}}$ to within $\pm 5–10\%$ but over-predicts torque below ${\mathsf{\lambda }}_{\mathrm{o}\mathrm{p}\mathrm{t}}$; the $\mathsf{\gamma }–{\mathrm{R}}_{\mathrm{e}\_\mathsf{\theta }}$ transition SST model reduces this error to $\pm 3–5\%$; DES, DDES, and LES reach $\pm 2–3\%$ at one to two orders of magnitude higher cost. Best practice computational fluid dynamics (CFD) guidelines are consolidated: domain extents of 15D upstream, 10D downstream, and 20D lateral; rotating sub-domain ${\mathrm{D}}_{\mathrm{r}\mathrm{o}\mathrm{t}}$ $\approx 1.5\mathrm{D}$; ${\mathrm{y}}^{+}\le 1$; $\Delta \mathsf{\theta }\le 0.1°$; and 20–30 revolutions before sampling. Performance enhancement strategies (variable pitch, guide vanes, helical twist, and hybridization) are reviewed quantitatively, with reported ${\mathrm{C}}_{\mathrm{p}}$ gains of $5–30\%$. Four research priorities are identified: (i) transition-sensitive turbulence closures validated below ${\mathrm{R}}_{\mathrm{e}\_\mathrm{c}}$ = $5\times {10}^5$; (ii) coupled aero-hydro-servo-elastic models for floating offshore VAWTs; (iii) machine-learning-augmented turbulence modelling—including physics-informed neural networks (PINNs) and neural-network-corrected RANS closures—to improve unsteady flow prediction at sub-LES cost; and (iv) integrated aeroacoustic–aeroelastic frameworks for urban and building-integrated deployment. Full article

The aviation sector is accelerating the transition toward low-carbon propulsion, and Sustainable Aviation Fuels (SAFs) represent a key leverage to reduce lifecycle emissions without modifying existing turbine architectures. Microturbines offer an effective and low-cost platform for assessing SAF behaviour under engine-representative conditions. In this work, a zero-dimensional performance and emission model of the GTM-140 microturbine was developed in GSP and validated against experimental data at 70,000–112,000 rpm for Jet A-1 and HEFA paraffinic blends. The model reproduces thrust and fuel-flow trends with good fidelity, with deviations typically below 6% across all operating points. Introducing 50% HEFA consistently reduces fuel consumption, leading to a TSFC decrease of 3–6%, with the strongest effect at high rotational speed, where compressor efficiency is highest. CO emission indices decrease by 6–9% at mid-load and converge at full power due to enhanced oxidation, while NO_x increases by 6–15%, driven by the higher adiabatic flame temperature associated with HEFA’s increased H/C ratio and heating value. These results confirm that simplified 0D modelling can reliably capture performance and emission trends of SAF-fuelled microturbines and demonstrate the dual effect of HEFA: improved combustion efficiency and CO reduction, at the expense of moderately higher NO_x formation. Full article

Aviation demand is projected to surpass 8 billion passengers per year by 2040, increasing the climate burden of kerosene-fueled propulsion. Conventional engines emit CO₂ and non-CO₂ species such as nitrogen oxides and soot, which significantly contribute to global warming. Hydrogen-based propulsion combining Solid Oxide Fuel Cells (SOFCs) with a Gas Turbine (SOFC–GT) can offer a carbon-neutral alternative with the potential for higher efficiencies than current turbofan and turboprop systems. In an SOFC–GT concept, waste heat from the SOFC is recovered in the turbine cycle, while the electrical output drives an electric motor, forming a hybrid turbomachinery–electric powertrain. Achieving SOFC operating temperatures of 650–800 °C at cruise conditions represents a key thermodynamic challenge, as compressor outlet conditions are insufficient. Two architectures are analyzed: direct coupling, where SOFC requirements define turbomachinery operation, and indirect coupling, which introduces air bypasses to increase flexibility. The results show that direct coupling enables higher cycle efficiency, whereas indirect coupling improves off-design operability at the expense of performance. Cross-validation of independent simulation frameworks strengthens the reliability of the findings and provides a foundation for evaluating SOFC–GT propulsion feasibility. Full article

Downhole boosting technology breaks the physical limitations of conventional surface boosting by enhancing pressure at the wellbore bottom, with micro-axial compressors serving as its core compression module. However, traditional axial compressors, when miniaturized, suffer from severe end losses and easy instability, failing to adapt to downhole space constraints and the efficient pressurization demands of low-permeability, low-pressure, and small-flow reservoirs. To address this, this study designed a compact micro-axial compressor. CFturbo was used for parametric blade design and optimization, while ANSYS CFX 2025 (with the SST turbulence model) conducted numerical simulations. A “simulation–diagnosis–optimization–validation” closed-loop strategy was adopted to adjust the blade’s leading-edge shape, camber line, and thickness distribution, combined with grid independence verification and inter-stage matching optimization. The results show that at the design speed (60,000 rpm), the compressor achieves a pressure ratio of 1.57 and an isentropic efficiency of 83.6%. It also maintains stable performance at 55,000 rpm (off-design speed), with excellent inter-stage aerodynamic matching and controllable leakage losses. This compressor meets downhole operational needs, providing technical support for developing low-permeability, low-pressure, small-flow reservoirs. Full article

The Variable Cycle Engine (VCE) is a key enabling technology for addressing the economic and environmental challenges of next-generation supersonic civil aircraft. This paper presents a multidisciplinary design analysis and optimization (MDAO) approach to quantitatively assess the potential benefits of Variable Cycle Engines (VCE) in the conceptual design of supersonic civil aircraft. In this approach, component-level models of a conventional Mixed-Flow Turbofan (MFTF) and a double-bypass VCE with a Core Driven Fan Stage (CDFS) are integrated into the MDAO process. Employing a multi-point optimization strategy, the engine design parameters and off-design control schedules are first determined. Subsequently, for each given engine design (MFTF and CDFS VCE), the airframe geometry parameters are optimized to minimize the aircraft Maximum Take-off Weight (MTOW). The application of this approach is illustrated through a case study of a medium-sized supersonic civil transport. The results indicate that, under the assumption of identical weights for the VCE and the MFTF, the design with the VCE reduces the MTOW by 2.8%, block fuel consumption by 5.7%, and total mission Nitrogen Oxides (NOx) emissions by 24.2% compared to the design with the MFTF. Additionally, lateral noise and flyover noise during the take-off phase are decreased by 2.2 EPNdB and 1.9 EPNdB, respectively. To account for the potential weight increase caused by the structural complexity of the VCE, a parametric weight sensitivity analysis is conducted. Results show that the VCE retains its advantages in MTOW, fuel efficiency, noise, and emissions for weight penalty factors up to 1.15. Full article

A major challenge for aircraft fuel cell propulsion systems is to ensure that the air properties on the cathode side remain within a narrow, suitable envelope throughout the flight. The components must maintain almost constant temperature, pressure and humidity levels under widely varying ambient conditions. The choice of components must take into account the aviation-specific requirements for weight and waste heat. In this numerical study, we investigate a novel cathode air supply system for a hydrogen fuel cell propulsion system which replaces the state-of-the-art electrical components used to drive the compressor in the cathode air supply system with a hydrogen-fuelled micro gas turbine. Previous studies have shown the potential of waste heat and overall cathode gas path size reduction but the off-design performance of such system is yet to be investigated. Hence, based on realistic regional aircraft flight missions and realistic atmospheric conditions, we investigate the off-design performance of the propulsion system. Therefore, a constant mass flow algorithm along cathode and gas turbine gas paths is developed and presented. Next, earth observation data are used to determine realistic boundary conditions and air contamination. Based on these data, the possible contaminant ingestion of the fuel cell is evaluated to allow for future sizing of filters for robust operation. Furthermore, the effects of realistic ambient conditions on the thermodynamic cycle yield important information about necessary revisions of the cycle design point. Full article

This study numerically investigates the influence of different fluid temperatures on the cavitation characteristics of a space-use micropump under microgravity conditions. A homogeneous multiphase model coupled with a thermal modified Zwart–Gerber–Belamri cavitation model is employed, and the SST turbulence model is applied to resolve the cavitating flow under rated and off-design flow rates. Results indicate that cavitation behavior is strongly dependent on both temperature and flow rate. At low temperatures, cavitation intensity increases, leading to reductions in head and efficiency and a slight increase in shaft power. In contrast, elevated temperatures suppress cavitation development, resulting in milder performance degradation and, in some cases, slight improvements in head and shaft power. Internal flow analysis reveals that lower temperatures promote more extensive vapor fraction distributions and greater flow distortion, while entropy production analysis shows that cavitation contributes limited additional loss overall, though entropy generation rises markedly under combined low temperature and high flow rate conditions. The findings highlight that cavitation effects are more pronounced at low temperatures and are further amplified at higher flow rates, providing insights for the design and reliable operation of space micropumps in on-orbit thermal management systems. Full article

The Composite Cycle Engine (CCE) enhances the conventional Joule/Brayton cycle by replacing the high-pressure compressor with a high-quality piston-based gas generator that enables extremely high compression, combustion, and expansion of the working fluid before entering the classic Joule burner. This piston-based topping cycle unlocks much more efficient fuel utilization. This paper studies a CCE concept featuring a system of free double piston (FDP) units for a potential long-range (LR) application in 2045, benchmarked against an advanced turbofan engine representative of the same time frame. In-house-developed simulation tools for the piston system and the overall power plant, as well as aircraft non-linear trade factor analysis, are used for different levels of conceptual assessment. First, the cooling demand inside the FDP system is determined. An engine cycle parametric study is then performed for the design point top-of-climb (ToC). Off-design performance is further studied, demonstrating a 9.3% improvement in thrust-specific fuel consumption (TSFC) in cruise relative to the baseline engine. After incorporating the engine weight and nacelle geometry effects, the engine reaches a total mission fuel burn reduction of around 14.7% compared to the baseline engine. The concept evaluation shows the fuel burn potential of the CCE in the future LR aviation sector and lays the foundation for further climate impact analysis. Full article

To improve the aerodynamic design efficiency of nacelle intake systems for wing-mounted civil aero-engines under multiple operating conditions, an integrated multi-objective optimization method was developed to address the limited optimization efficiency and robustness encountered in conventional approaches. The proposed method employed parametric techniques to construct three-dimensional non-axisymmetric nacelle geometries and integrated flow-field simulations with performance evaluation modules, forming a hybrid optimization framework based on a Kriging surrogate model coupled with the NSGA-II genetic algorithm. Two-dimensional numerical analyses were employed to rapidly evaluate inlet profiles and constrain the three-dimensional design space. Following the reduction in the design space, the three-dimensional optimization simultaneously accounted for multiple performance objectives, including nacelle drag and block fuel consumption during cruise conditions, as well as inlet distortion and flow separation under off-design conditions. A set of Pareto-optimal solutions was obtained through surrogate-based prediction and validated using high-fidelity CFD simulations. The results indicate that the optimized nacelle configuration achieves a 0.933% reduction in drag coefficient and a 0.628% decrease in block fuel consumption under cruise conditions. Under crosswind conditions, the inlet total pressure recovery coefficient is increased by 2.76%, accompanied by a pronounced reduction in flow separation, while under maximum-lift coefficient conditions, the total pressure recovery remains above 99%. These results demonstrate that the proposed optimization approach enables coordinated aerodynamic performance improvements across multiple operating conditions while simultaneously enhancing overall aircraft fuel efficiency, providing an effective strategy for advanced nacelle aerodynamic shape design. Full article