Understanding which structural parameters govern flow stability and particle separation is essential for turbo air classifier design. In this study, the Y160L-6 turbo air classifier was used to examine whether different categories of spatial structural parameters influence classification performance through the same flow mechanism or play distinct roles in regulating the internal flow field. Two representative parameters, namely the spacing between the secondary air inlet and the rotor cage and the spacing between the secondary air inlet and the feed inlet, were analyzed using computational fluid dynamics (CFD) coupled with the RNG k–ε turbulence model and the discrete phase model (DPM). The results show that the two parameters affect the classifier through different mechanisms. Increasing the secondary air inlet–rotor cage spacing causes a non-monotonic variation in wall pressure and tangential velocity, indicating a strong influence on the global swirling structure. At a spacing of 1490 mm, the pressure distribution in the classification zone becomes more uniform, the tangential velocity reaches a relatively high level, and the intensity of the precessing vortex core (PVC) is reduced. Under this condition, the cumulative proportion of 2–5 μm particles at the fine powder outlet increases by 34.1% compared with the initial configuration. In contrast, variations in the secondary air inlet–feed inlet spacing exert only a limited influence on the overall flow structure and classification characteristics under relatively low feed inlet velocity conditions, indicating that this parameter mainly affects local flow disturbance rather than global flow stability. These findings demonstrate that structural parameters associated with the coupling between secondary airflow and rotor rotation dominate classifier performance, whereas parameters related to feed–air interaction exert only a secondary effect under low feed momentum conditions. These findings provide design guidance for the investigated Y160L-6 turbo air classifier and may serve as a reference for similar classifier structures under comparable operating conditions.
In air-assisted orchard spraying, airflow characteristics strongly determine spray performance. This study designed a tower-shaped fan for grape canopies and investigated its aerodynamic behaviour. A three-dimensional computational fluid dynamics (CFD) model of the internal flow field was established to quantify the effects of shroud taper, upper and lower guide-vane angles, inlet diameter, and inlet position on outlet air-velocity uniformity. Single-factor simulations confirmed that all selected structural parameters significantly affect the outlet air velocity’s coefficient of variation (CV). Based on these results, central composite design was applied for multi-parameter optimisation. A second-order regression model was developed to describe the relationship between guide-vane angles, shroud taper, inlet position, inlet diameter, and air-velocity CV response. Analysis of variance showed that the influence of the factors decreased in the following order: guide-vane angle > inlet position > inlet diameter > shroud taper. Numerical optimisation identified the optimal configuration as a guide-vane angle of 118.37°, shroud taper of 23.84°, inlet position of 29.35 mm, and inlet diameter of 493.92 mm. Under these conditions, the predicted air-velocity CV decreased to 12.07%. A field validation experiment was conducted using representative measurement points selected from the simulated velocity distribution. The maximum relative error between measured and simulated values was below 6%, indicating strong agreement. These results confirm the reliability of the CFD model and demonstrate its effectiveness for structural optimisation of orchard air-assisted spraying equipment.
P. Zhan, Z. Y. Sun, Q. Meng et al.· Journal of Applied Fluid Mec...· 0 citations
The staggered rotor system is a potential power system layout for compact multi-rotor aircraft designed for urban air mobility. Deeply revealing the aerodynamic interaction mechanism between rotors under the influence of key configuration parameters is crucial for the refined aerodynamic design of such aircraft. Therefore, this study experimentally measured the effects of parameters such as rotor speed, rotation direction, axial spacing (H/R), and radial spacing (L/R) on hover performance. Furthermore, by integrating smoke flow visualization technology, the transient flow field structures under different rotation directions and radial spacings were captured, with a focus on exploring their correlation mechanisms with hover performance. The results indicate that, within the experimental parameter range, radial spacing is the dominant parameter affecting the degree of aerodynamic interaction between rotors. The influence of rotation direction and axial spacing is secondary and exhibits a coupling effect with radial spacing, while the influence of rotor speed is minimal. A high correlation exists between the transient flow field structure and hover performance. At small radial spacings, the high immersion of the lower rotor in the downwash of the upper rotor causes a thrust loss of ∼50% for co-rotating and 30% for counter-rotating configurations. As L/R increases, the flow field structure stabilizes, and thrust recovers. In addition, by comparing rotation directions, it was found that the wake contraction rate shows a proportional relationship with rotor thrust loss. This study can provide a reference basis for the aerodynamic layout design and optimization of compact multi-rotor aircraft.
He Zhu, Zhiyang Xin, Hong Nie et al.· AIP Advances· 0 citations
To suppress the flow-induced vibration of a single-stage single-suction centrifugal pump (rated head 5 m, flow rate 30 m
3
/h, rotational speed 1000 r/min), the key impeller parameters were taken as design variables and screened via the parameter sensitivity analysis method in this study. The internal flow field was solved using the Reynolds-Averaged Navier–Stokes (RANS) approach with the SST k–ω turbulence model, implemented in the commercial CFD code ANSYS Fluent. With pump efficiency and the sample standard deviation of circumferential tangential velocity uniformity at all nodes of the impeller outlet set as the optimization objectives, and pump head as the constraint condition, the Kriging surrogate model combined with the Non-dominated Sorting Genetic Algorithm II (NSGA-II) was adopted to conduct the optimal design of the impeller structure. The results show that the head and efficiency of the optimized pump are increased by 10.8% and 2.7%, respectively. The pressure pulsation amplitudes associated with the blade-passing frequency (BPF) at the volute tongue are significantly reduced, with a 36.1% decrease at the volute tongue and a 22% decrease inside the volute, which effectively mitigates the rotor-stator interaction (RSI). Comparisons of the internal flow fields confirm the suppressed secondary flows, reduced turbulent kinetic energy, weakened jet-wake effects, and improved unsteady performance of the optimized pump, thus verifying the feasibility and effectiveness of the proposed optimization strategy.
Jiafu Guo, Xinxiang He, Abdul Mutalib bin Leman et al.· Proceedings of the Instituti...· 0 citations
The performance of briquette drying systems is strongly influenced by airflow distribution and thermal uniformity within the drying chamber, which are governed by outlet configuration and internal flow patterns. However, limited studies have systematically quantified the effect of exhaust outlet arrangements on the coupled heat transfer and fluid flow behavior in industrial-scale briquette ovens. This study aims to numerically investigate the influence of single-, double-, and four-outlet configurations on airflow characteristics, temperature distribution, and overall thermal performance of a briquette drying oven. A three-dimensional geometric model representing the combustion chamber, drying chamber, and briquette racks was developed and analyzed using Computational Fluid Dynamics (CFD). Steady-state simulations were performed in ANSYS Fluent employing the standard k–ε turbulence model, with air properties, inlet velocity (9.97 m/s), and thermal boundary conditions defined based on operational data. The results reveal that outlet configuration significantly affects flow recirculation intensity and temperature uniformity across the briquette racks. The four-outlet configuration produced the most homogeneous airflow distribution and reduced thermal gradients, thereby enhancing convective heat transfer effectiveness compared to single- and double-outlet designs. Conversely, the single-outlet case exhibited pronounced recirculation zones and localized temperature variations, potentially leading to uneven drying. These findings demonstrate that optimizing outlet arrangement is a critical design parameter for improving drying efficiency and energy utilization in briquette oven systems, providing a validated numerical framework for future thermal system optimization.
The dual-layer staggered multirotor aircraft represents a promising solution for operations in confined spaces. To address the aerodynamic interaction phenomena between rotors on different layers, this study conducts performance experiments and numerical simulations based on a Three-Rotor System Model (TRSM). By analyzing hovering rotor performance and wake structures under various configuration parameters, the aerodynamic characteristics of a single rotor simultaneously influenced by two adjacent rotors on the opposite layer are specifically investigated. The results show that radial spacing (L/R) is the dominant parameter governing the intensity of aerodynamic interaction between rotors, while rotational speed, axial spacing(H/R), rotation direction, and arm angle all exhibit weak correlations. Rotor performance exhibits unsteady periodic fluctuations, with thrust loss at the trough attributed to the deterioration of inflow conditions and reduction in blade pressure differential. The thrust loss and fluctuation amplitude of the lower rotor are significantly greater than those of the upper rotor. Furthermore, due to the combined slipstream and induced effects of the two adjacent rotors, the thrust loss of the TRSM is approximately three times that of the staggered counter-rotating rotor system. Partial rotor disk overlap leads to high distortion of the wake structure and the emergence of numerous irregular secondary vortices. Evaluations based on a non-dimensional configuration factor reveal that quadrotor, hexacopter, and octocopter systems achieve a favorable balance between overall vehicle size and aerodynamic efficiency at L/R = 1.6, 1.4, and 1.8R, respectively. This study provides a reference for the aerodynamic layout design and performance prediction of compact multirotor aircraft.
He Zhu, Zhiyang Xin, Hong Nie et al.· The Physics of Fluids· 0 citations
Vortex separators have become indispensable small units for the treatment of multiphase streams and particle-laden flows in wastewater, stormwater management and environmental protection industries. Despite the vast application, there is not yet a unified understanding of the joint control of separation performance and similarity scaling by structural configuration, operational parameters, and characteristics of particles. This review synthesizes new developments based on inlet-outlet configurations, internal baffling and vortex-forming elements, along with key hydraulic variables including surface loading rate, hydraulic retention time and inflow velocity over wide ranges of particle sizes, densities and concentrations. The analysis uncovers mechanistic relationships of the flow structure, turbulence and particle trajectories. Principal dimensionless parameters particularly Peclet number (Pe), Reynolds number (Re), and Froude number (Fr) are identified for enabling performance transfer from laboratory models to full-scale systems. The research establishes that meaningful optimization involves simultaneous consideration of the structural, hydraulic and particle domains. Future directions in theoretical development and structural innovation are provided to guide vortex separator design for the next generation.