Search Results (28)

As global mineral resources at shallow depths continue to deplete, thermal hazards have emerged as a critical challenge in deep mining operations. Conventional localized cooling systems suffer from a fundamental inefficiency where their cooling capacity is rapidly dissipated by the main ventilation airstream. This study introduces the innovative concept of a “microclimatic circulation zone” implemented through a convection–radiation cooling system. The design incorporates a synergistic arrangement of dual fans and flow-guiding baffles that creates a semi-enclosed air circulation field surrounding the modular convection–radiation cooling apparatus, effectively preventing cooling capacity loss to the primary ventilation flow. The research develops comprehensive theoretical models characterizing both internal and external heat transfer mechanisms of the modular convection–radiation cooling system. Using Fluent computational fluid dynamics software, we constructed an integrated heat–moisture–flow coupled numerical model that identified optimal operating parameters: refrigerant velocity of 0.2 m/s, inlet airflow velocity of 0.45 m/s, and outlet aperture height of 70 mm. Performance evaluation conducted at a mining operation in Yunnan Province utilized the Wet Bulb Globe Temperature (WBGT) index as the assessment criterion. Results demonstrate that the enhanced microclimatic circulation system exhibits superior cooling retention capabilities, with a 19.83% increase in refrigeration power and merely 3% cooling capacity dissipation at a 7 m distance, compared to 19.23% in the conventional system. Thermal field analysis confirms that the improved configuration successfully establishes a stable microclimatic circulation zone with significantly more concentrated low-temperature regions. This effectively addresses the principal limitation of conventional systems where conditioned air is readily dispersed by the main ventilation current. The approach presented offers a novel technological pathway for localized thermal environment management in deep mining operations affected by heat stress conditions. Full article

Based on the Daozhen–Wulong Zimuyan tunnel, the distance from the outlet of the air duct to the tunnel face and the diameter of the air duct are studied through an orthogonal experimental design. Aiming at the influence of the position of the air duct of the axial flow fan in the tunnel on the ventilation flow field, the improved TOPSIS theory is adopted for detailed data analysis, and the flow field characteristics are thoroughly checked to identify the optimal working condition configuration. The results show that with the increase in the distance between the air duct and the tunnel face, the local CO concentration will first decrease and then increase, indicating that too large or too small a distance will weaken the effective CO emission ability of the tunnel face, and the distance between the air duct outlet and the tunnel face is the best scheme; by combining the TOPSIS theory, entropy weight method, and analytic hierarchy process, the optimization scheme is obtained. When the distance between the outlet of the air duct and the working face is 15 m, the side wall of the air duct is 4 m away from the air, the diameter of the air duct is 1.8 m, the flow field in the tunnel shows a high degree of stability, the wind speed is significantly increased, and the vortex area that may hinder the air flow is effectively eliminated. The ventilation efficiency is greatly improved and the overall stability of the tunnel is enhanced. Full article

This study proposes a flow field modeling analysis of kitchen environments with air-conditioning range hoods. The substructure approach is applied to resolve the challenges of low computational efficiency and convergence difficulties associated with the simultaneous consideration of the range hood and the cooling air-conditioning fan impeller rotation models. The presented approach effectively enhances computational efficiency while ensuring accuracy. A flow field analysis of the air-conditioning substructure was performed in Fluent to obtain the velocity contour plot at the air-conditioning outlet monitoring surface. The data were then mapped to the full kitchen hood model to enable a comprehensive flow field analysis of the kitchen setup. The results show that the proposed substructure-based method to analyze the flow field in kitchens with air-conditioning hoods is computationally efficient, achieving an alignment accuracy above 95% across four measurement points. These findings establish a strong foundation for future comfort assessments and the optimization of kitchens with air-conditioning hoods. Full article

As one of the most widely used appliances in home and office scenarios over recent decades, electrical fans and their use in built environments have garnered considerable research interest. However, current methods are insufficient to reflect the overall characteristics of different types of fan equipment. This study conducted airflow field tests for six typical electrical fans and human comfort experiments across background temperature conditions of 26 °C, 28 °C, and 30 °C. The airflow test results showed the following: (1) for the mechanical airflow generated by fans, the mean airflow speed (MAS) had a strong negative correlation with turbulence intensity (Tu) and the power spectral index (β), which made Tu and β have a complementary distribution with airflow speed, meaning that areas with a higher airflow speed had lower dynamic characteristics; and (2) the form of the fan mainly affected the flow field distribution in the near-fan area (within 2 m), where tower fans and vaneless fans with elongated outlets had a mainstream airflow area that spread to about 0.2 m in width but 0.6 m in height at a distance of 0.25 m from the fan. The airflow speed distribution shape of axial-flow fans with circular outlets was circular on the test surface at the same position, with a radius of about 0.1–0.2 m. The human comfort experiment revealed that, at 28 °C, in the low-airflow-speed area (v < 1.5 m/s), the increased Tu and power spectral β of the airflow near the head and chest could reduce the thermal sensation vote (TSV). Additionally, this improvement slightly increased as the room temperature rose. When the airflow speed was high, the dynamic characteristics were generally low, and at this time, airflow speed played a leading role in reducing thermal sensation. The results of this paper have certain reference value for the improvement of comfortable dynamic characteristics and functional flow field design in subsequent fan product development. Full article

This study investigates a dual-stage axial-flow fan within a specific power plant context. Numerical simulations encompassing both steady-state and stall conditions were conducted utilizing the Reynolds-averaged Navier–Stokes (RANS) equations coupled with the Realizable k–ε turbulence model. The findings reveal that, under normal operating conditions, there exists a positive correlation between the mass flow rate and outlet pressure with gas density while displaying a negative correlation with dynamic viscosity. Regardless of the changes in air density, the volumetric flow rate at the maximum outlet pressure of the fan remains essentially the same. When a stall occurs, the volumetric flow rate rapidly decreases to a specific value and then decreases slowly. The analysis of the three-dimensional flow field within the first-stage rotor was performed before and after the rotational stall occurrence. Notably, stall inception predominantly manifests at the blade tip. As the flow rate diminishes, the leakage area at the blade tip within a passage expands, directing the trajectory of the leakage vortex toward the leading edge of the blade. Upon reaching a critical flow rate, the backflow induced by the blade tip leakage vortex obstructs the entire passage at the blade tip, progressively evolving into a stall cell, thereby affecting flow within both passages concurrently. Full article

In order to study the influence of various parts of the structure of a wet dust removal fan for mining (including the number of driving impeller blades, the airfoil of the driving impeller blades, the number of driven impeller blades, the rear guide vane, the swirl guide vane, and the length of the outlet section) on dust removal performance, a wet dust removal fan for mining was modeled according to different structural parameters. The internal flow field and dust removal of the fan were then numerically simulated using the Computational Fluid Dynamics (CFD) method. The results show that after the airflow passes through the swirl guide vane of the dust removal fan, there is an obvious swirl flow in the exit section of the dust removal fan. Under the action of centrifugal force, a large amount of dust is collected on the side wall of the exit section. With the increase in the number of driving impeller blades, the total pressure efficiency, static pressure efficiency, and dust removal efficiency of the dust removal fan decrease. When the driving impeller blade adopts the C-4 airfoil, the total pressure efficiency and static pressure efficiency of the dust removal fan are higher but the dust removal efficiency is lower than that of the same thickness circular plate airfoil. With the increase in the number of driven impeller blades, the power of the driving impeller shaft of the dust removal fan gradually increases; the total pressure and static pressure values first increase and then decrease; and the driven impeller speed, total pressure efficiency, static pressure efficiency, and dust removal efficiency gradually decrease. Adding the rear guide vane structure can improve the total pressure efficiency and static pressure efficiency of the dust removal fan but will reduce the dust removal efficiency of the dust removal fan. The increase in the swirl guide vane structure will reduce the total pressure efficiency and static pressure efficiency of the dust removal fan but the dust removal efficiency will be significantly improved. The extension of the outlet section of the dust removal fan will reduce the total pressure efficiency and static pressure efficiency of the dust removal fan, but the dust removal efficiency will increase. In this paper, by changing the structural parameters of the dust removal fan and establishing different models for numerical simulation and analysis, the influence law of the structural parameters of the dust removal fan on the dust removal performance is obtained, providing a way to improve the performance of the dust removal fan. Full article

As the core power element of a centrifugal fan, the impeller’s structural parameters are important factors affecting the aerodynamic performance of the fan. Therefore, to improve the aerodynamic performance of centrifugal fans, in this study, we take the Powered Air-Purifying Respirator (PAPR) power system as the object of research and use a combination of computational fluid dynamics (CFD) and experimental validation to investigate the effects of the number of blades, blade inlet angle, blade outlet angle, blade height, and blade thickness on the aerodynamic performance of the fan. A five-factor, four-level orthogonal test table L₁₆ (4⁵) was selected to obtain the optimal combination of structural parameters for the impeller. In addition, in order to identify and visualize the features of the vortex, Q Criterion Normalized is applied to the simulation on the basis that the minimum pressure appears in the vortex core. In this study, Q Criterion Normalized is used to compare the internal vorticity of the prototype with that of the optimized prototype. The results show that (i) the order of influence of each parameter on the aerodynamic performance of the centrifugal fan is blade height > blade outlet angle > blade inlet angle > number of blades > blade thickness; (ii) the optimal combination of the structural parameters is number of blades 48, blade inlet angle 80°, blade outlet angle 120°, blade thickness 0.6 mm, and blade height 23 mm; the optimized prototype has an increase in air pressure of about 10%, an increase in air volume of about 31%, and an increase in efficiency from 49.61% to 53.57%; (iii) the intensity of internal vortices in the optimized prototype is weakened, the size of vortices and the number of vortices are reduced, and the homogeneity of the flow field is also improved. Full article

The cooling fan is one of the important noise sources for new energy vehicles, and the research on its aerodynamic and aeroacoustic characteristics is of great help to improve the noise, vibration and harshness performance of new energy vehicles. However, most of these studies focus on the impeller, and little consideration has been given to the study of the shroud. Based on the coupling calculation method of large eddy simulation and the Ffowcs-Williams and Hawkings acoustics model, the aerodynamic and aeroacoustic characteristics in a cooling fan with the shroud are investigated at flow rates from 0.623 kg/s to 1.019 kg/s (where 0.865 kg/s is the flow rate corresponding to the best efficiency point). The accuracy of numerical simulation results is verified by the grid independence verification and the comparison of experimental data. Research shows that several large-scale vortex structures are observed in the clearance between the impeller and the shroud. The maximum peak-to-peak values of pressure fluctuation at different flow rates occur in the intermediate section or outlet section of the shroud. Although the shroud contributes relatively less to the far field noise, its different distribution may change the position of the maximum sound pressure level. The dominant frequency of pressure fluctuation equals the blade passage frequency (BPF) and the maximum SPL is around the BPF, both of which are independent of flow rates. The maximum SPL and the amplitude of the dominant frequency decrease as the flow rate increases. Full article

In this study the flow field of a centrifugal electronic cooling fan operating at an off-design point of 0 Pa static fan pressure is investigated by means of Computational Fluid Dynamics. The results obtained by four different turbulence models, the realizable k-$ϵ$ model, the SST k-$\omega$ model, a Reynolds Stress Model, and Scale-Adaptive Simulation are analyzed and compared. The focus lies on describing how the flow through impeller and volute influences the fan outlet flow field, and velocity profiles and velocity fluctuations at the outlet are compared to previously published measurements. All models tend to underpredict the measured outlet flow rate, but are capable of producing the characteristic C-shaped profile of high velocities, previously determined in Constant Temperature Anemometry measurements. However, the realizable k-$ϵ$ model is significantly too diffusive, leading to blurred velocity contours. The other models exhibit reasonable agreement with the measured flow field, but show differences in a number of aspects. The SST k-$\omega$ model, for instance, even produces local inflow in a confined area. The SAS approach overpredicts the length of the lower lobe of the C-shape. The research is relevant to improve simulation results of impingement cooling and heat sink optimization using centrifugal fans. Full article

In response to the issues of high cost, limited detection accuracy, and significant measurement errors inherent in conventional manual techniques used to measure straw cover weight under the conservation tillage method, a dedicated straw cover weight detection machine was developed in the current study. This machine included a critical straw suction device that utilizes negative pressure to collect straw within a defined area. The efficiency of straw collection is affected by suction chamber structural parameters and transport pressure. With crushed corn straw as the research subject, the theoretical calculation of straw suspension velocity was used to determine the wind duct diameter, perform the initial design of the suction chamber structure, and select the appropriate fan. After conducting preliminary experiments, single-factor optimization tests, and orthogonal rotation experiments, we analyzed the flow field distribution patterns and identified the critical parameters for the straw cover weight suction unit. We found that the fan should operate at a speed of 2900 r/min, the diameter of the straw outlet should be 200 mm, the vertical height of the suction chamber should be 536 mm, and the bottom diameter of the suction chamber should be 800 mm. The optimization results were validated through simulation tests and bench tests, yielding an average near-ground airflow velocity of v_j = 9.03 m/s and an average outlet airflow velocity of v_o = 34.27 m/s, meeting the basic requirements of the suction unit. This study could provide a new approach and technical support for the automated detection of straw cover weight in conservation tillage areas. Full article

To enhance the working efficiency and aerodynamic performance of the centrifugal fan in the air system of a cotton picker, a new type of centrifugal fan blade was designed by extracting the mid-arc section from the prototype blade and integrating an airfoil, which was transplanted and coupled to the mid-arc section. The design aimed to improve the airflow characteristics and performance of the centrifugal fan. By combining experimental data from centrifugal fans used in existing cotton-picker air systems and employing computational fluid dynamics (CFD) methods, the internal flow field structure of the centrifugal fan was simulated. This study focused on investigating the aerodynamic performance of the new centrifugal fan blade and its impact on improving the internal flow patterns within the centrifugal fan. The results of the flow field visualization analysis indicate that the new blade design exhibits excellent aerodynamic performance, improving the flow distribution within the centrifugal fan. It enhances the uniformity of the outlet airflow, reduces the occurrence of localized “jet-wake” phenomena at the impeller’s outlet, suppresses the generation and development of vortices in the flow channel, and reduces local energy losses within the impeller. These improvements contribute to an increase in the fan’s efficiency. Under rated operating conditions, the efficiency of the prototype fan was measured at 60.3%, while the optimized fan achieved an efficiency of 64.8%. This signifies a significant improvement in the efficiency of the centrifugal fan. Full article

Class and shape transformation functions are proposed to carry out the parametric design of the blade profiles because fan efficiency is closely related to the shape of blade profiles. An optimization with the objectives of fan efficiency and static pressure based on the Kriging models was established, and numerical simulation data were applied to construct the Kriging models. The dissipation function was used to analyze the fan energy loss. The prediction results show that the maximum accuracy error between the Kriging model and the experimental data is approximately 0.81%. Compared with the prototype fan, the optimized fan was able to ameliorate the distribution of the flow field pressure and velocity; the outlet static pressure increased by 9.03%, and the efficiency increased by 2.35%. The dissipation function is advantageous because it can intuitively indicate the location and amount of energy loss in the fan, while effectively obtaining the total energy loss as well. The situation of energy loss was mutually validated with the density of the static pressure contours and the streamline distribution. The flow fields at the leading edge of the optimized fans were improved by analysis of the dissipation function, and the leading edges of the three impellers selected from the Pareto front were narrower and flatter than those of the prototype fan. Full article

Particulate matter in Computer Numerical Control (CNC) machining workshop is harmful to workers’ health. This paper studies particulate matter transfer and the performance of various ventilation strategies in a CNC machining workshop. To obtain the boundary condition of the particle field, instruments were installed to obtain the particle size attenuation characteristics and source strength, respectively. The results show that the 99% cumulative mass concentration of particles is distributed within 1.5 μm, and the release rate of particles from the full enclosure. Next, the indoor flow field and particle field were simulated by numerical simulation with the measured boundary conditions. The working area’s age of air, particle concentration, and ventilation efficiency were compared between four displacement ventilation methods and one mixed ventilation method. The results show that the working area’s mean particle concentration and ventilation efficiency under longitudinal displacement ventilation is better than other methods. At the same time, the mean age of air is slightly worse. In addition, mixed ventilation can obtain lower mean age of air, but the particle concentration is higher in the working area. The bilateral longitudinal ventilation can be improved by placing axial circulation fans with vertical upward outlets in the center of the workshop. Full article

Three-dimensional throughflow models represent a turbomachinery cascade via a force distribution without the need for detailed geometric modelling in the numerical solution, saving consistent computational resources. In this paper, we present the application of a body force method on an axial transonic fan implemented into an in-house tool for axisymmetric throughflow simulations. By a systematic comparison of local and integral quantities with a validated numerical solution, the capabilities and limitations of the model are discussed for different operating regimes. The implementation is first validated at the peak efficiency calibration point, providing a good duplication of blade flow variables and radial profiles. The design total pressure is matched with a 0.6% absolute difference and a slightly higher slope of the characteristic towards the stall. The isentropic efficiency curve is penalised after the choking mass flow rate calibration, presenting an absolute difference close to 2%, although with a consistent off-design trend. In general, the model provides a satisfactory representation of the flow field and the outflow spanwise distributions, with locally larger discrepancies near the endwalls. Finally, the method is applied to simulate the fan and outlet guide vanes installed into an isolated turbofan nacelle. The onset of intake stall at a high angle of attack is compared between the body force and a boundary conditions-based approaches, highlighting the importance of adopting fully coupled solution methods to study fan/airframe interaction problems. Full article

Flutter was encountered at part speeds in a scaled wide chord fan blisk designed for a civil aeroengine during a rig test when the fan bypass flow was throttled toward its stall boundary. Analysis of the blade tip timing measurement data revealed that the fan blades vibrated at the first flap (1F) mode with nodal diameters of two and three. To facilitate a further rig test and ultimately eliminate the flutter problem, a numerical campaign was launched to help understand the root causes of the flutter. Both the influence coefficient method (ICM) and the traveling wave method (TWM) were employed in the numerical investigation to analyze unsteady flows due to blade vibration, with the intention to corroborate different numerical results and take advantage of each method. To eliminate nonphysical reflections, a sponge layer with an inflated mesh size was used for the extended inlet and outlet regions. Steady flow field and unsteady flow field were examined to relate them to the blade flutter. The influences of vibration frequency, mass flow rate, shock, boundary layer separation and acoustic mode propagation behaviors on the fan flutter stability were also investigated. Particular attention was paid to the acoustic mode propagation behaviors. Full article