THE IMPACT OF REDUCED BLADE COUNT AND TIP CLEARANCE VARIATION ON THE FLOW FIELD OF AXIAL COMPRESSOR BLADE ROWS

Independent Effects of Blade Number and Solidity on Cyclorotor Hover Performance: A Parametric CFD Study for Design Optimization

The influence of blade number and rotor solidity on cyclorotor hover performance remains insufficiently understood because previous studies have generally varied these parameters simultaneously or investigated them through separate one-factor analyses. This work examines their independent effects using a two-dimensional unsteady Reynolds–Averaged Navier–Stokes model in which blade number (2–8) and rotor solidity (0.24–0.60) are varied independently across 26 geometrically feasible design points, at constant rotor radius and rotational speed. The model is validated against published experimental data for the same rotor before the parametric analysis is performed. At fixed rotational speed, increasing solidity raises both the thrust and power coefficients and lowers power loading. Because power loading is disk-loading-dependent even for an ideal rotor, however, this apparent penalty largely reflects a change in operating point rather than a loss of aerodynamic efficiency: compared at matched disk loading, efficiency varies only weakly with solidity except in the corner of the design space that combines high solidity with a long blade chord, and an interior efficiency optimum emerges near σ≈0.36 for blade counts N=4–8, reconciling the present results with the chord-to-radius optimum reported in the literature. Blade number has only a secondary influence on mean performance at constant solidity, consistent with classical rotor theory; azimuthally resolved loads, however, show peak-to-mean thrust ratios of 3–4 for two- and three-bladed rotors, a design constraint invisible in cycle-averaged metrics.

Investigation of lift and drag performance of a flap assisted wind turbine blade at different pitch angles

Effects of Blades Rows Clocking on Aerodynamics of a Gas Turbine Low Pressure Axial Turbine

Detailed numerical simulations have been carried out to investigate effects of blades rows clocking on aerodynamic performance of a low-pressure turbine unit of an axial multistage turbine. Clocking mechanism is imposed on the fixed blades row of the second stage, and results of numerical flow simulations are presented and discussed in this paper. Frozen rotor and transient rotor-stator approaches have been undertaken through the numerical analyses. Three dimensional results of the flow fields, in terms of distributions of vorticity strength, entropy and total pressure are presented and discussed in detail for different clocking positions of the blades rows. Steady results illustrated that under the optimum position of clocking the aerodynamic efficiency and output power of the second stage increases by 0.39% and by 0.33%, respectively, in comparison to the worst position of clocking. The optimum clocking case is convoyed with upstream wake impingement on the second stator leading edge region. In addition, regarding with time-averaged results, flow enters the second rotor blades row with a higher total pressure; something about 0.32% more than that for the worst case. Furthermore, according to both the steady and time-resolved results, it is shown that higher pressure at stator outlet under optimum clocking is strongly accompanied by higher dynamic pressure at the stator exit.

Aerodynamic Performance and Wake Characteristics of a Four-Rotor Wind Turbine

The continuous upscaling of offshore wind turbines exacerbates challenges such as blade flutter, stability degradation, and logistical difficulties. To address these issues, this study proposes a parallel multi-rotor wind turbine and systematically investigates its aerodynamic performance and wake characteristics. Based on a 5 MW reference turbine, validated Unsteady Reynolds-Averaged Navier–Stokes (URANS) simulations incorporating the sliding mesh technique and Shear Stress Transport (SST) k-ω turbulence model are conducted to evaluate twin- and four-rotor configurations under various geometric and rotational layouts. Crucially, this study reveals for the first time that asymmetric rotational configurations induce wind field skewness and modify rotor-edge bypass flow, leading to power imbalance among rotors. Additionally, the twin-rotor configuration enhances total power output with negligible thrust variation. For the four-rotor system, power is highly spacing-dependent: at 1.1 rotor diameter spacing, power increases by approximately 3.0% compared to a single rotor. As spacing increases, rotor coupling weakens, which reduces wake non-uniformity but simultaneously slows wake recovery and decreases power generation.

Synergistic Tip Clearance Optimization for Fuel Cell Centrifugal Compressors: Integrating Blade Deformation and Rotordynamics

Tip clearance is a critical determinant of aerodynamic performance in fuel cell centrifugal compressors supported by gas foil bearings. Traditional designs typically employ overly conservative clearances to mitigate rubbing risks, which induces substantial leakage losses and compromises efficiency. This study proposes a synergistic optimization methodology that integrates multi-physics blade deformation with comprehensive rotor dynamics. First, fluid-structure interaction (FSI) simulations were conducted to quantify blade deformations under coupled aerodynamic, thermal, and centrifugal loads. Second, the rotor's radial and axial displacements were characterized across the full operational speed range, accounting for the non-linear stiffness of foil bearings. Quantitative analysis reveals that rotor dynamics are the predominant driver of clearance variations, contributing 44.31% of the total deviation. Based on these insights, the tip clearances were optimized from a uniform 0.3 mm to 0.28 mm for the first stage and 0.25 mm for the second stage. Experimental validation demonstrates that the optimized compressor operates safely without interference, achieving a 1.2% enhancement in isentropic efficiency (from 69% to 70.2%) and a 2.4% increase in peak pressure ratio. This integrated approach provides a robust framework for high-efficiency compressor design in hydrogen fuel cell applications.

Effect of Straight and Compound Blade Lean on the Aerodynamic Performance of a High-Pressure Turbine Nozzle Guide Vane under Residual Swirl

The exhaust flow at the outlet of modern lean-burn combustors, which offer reduced NOx emissions for gas turbines, is characterized by hot streaks (HS) and residual swirl that affect the aerothermal performance of downstream high-pressure (HP) turbine nozzle guide vanes (NGVs). Although leaned blades are widely employed in turbomachinery design to mitigate secondary flow losses and improve aerodynamic efficiency, the combined influence of straight and compound lean configurations under residual swirl conditions remains comparatively less investigated. The objective of this study is therefore to numerically investigate the effect of blade lean on secondary flows and aerodynamic losses in axial turbine NGVs operating under simplified combustor-exit swirl conditions. The investigations are conducted on the NGV annular cascade developed at the NASA Lewis Research Center. Steady compressible flow simulations are performed by solving the Reynolds-Averaged Navier–Stokes equations using the Shear Stress Transport turbulence model. Three-dimensional vane geometries are generated by stacking the 2D blade profile along linear positive and negative lean axes with respect to the radial direction, with lean angles ranging from α = −8° to +8°. A total of sixteen configurations are first analyzed under axial inflow conditions to evaluate the influence of blade lean on aerodynamic performance. Based on the obtained performance trends, the baseline configuration together with the optimum straight-lean and compound-lean cases are subsequently investigated under two inlet swirl orientations (positive and negative) applied at the leading edge, with a swirl intensity of |Sn| = 0.4.The results show that the negative straight lean configuration NSL02 reduces the total pressure loss coefficient by approximately 3% under axial inflow conditions and by about 14% under negative swirl compared with the baseline case. Under positive swirl conditions, the negative compound lean configuration NCL08 achieves the best performance, reducing the loss coefficient from 2.274 to 1.914, corresponding to an improvement of approximately 16%.