Axial Fan Blade Research Articles

The Effect of Tilt Angle of Axial Fan Blades on Air Flow Distribution in the Cabinet Dryer: Simulation Study Using Computational Fluid Dynamics

The application of tray dryer is widely used for various commodity dryers due to its simple construction. However, one of the drawbacks of tray dryer is the uneven airflow distribution in the drying chamber which results in the drying rate in the tray position being unequal. As a result, the degree of dryness of the product also varies. This study investigated the effect of fan blade angle on airflow distribution in the dryer cabin through numerical simulations. The axial fan diameter was 350 mm with a thickness of 20 mm. The variations of axial fan blades used were 10o, 20o, 30o and 45o. The number of blades used was 4, and the allowable airflow limit was 2 m x 1 m x 1 m, with an axial fan rotation of 500rpm. Based on the simulation results, the 45o fan angle had good air distribution results compared to the 10o, 20o, and 30o fan angles. Likewise, the distribution of air produced by the fan was evenly distributed, because the greater the angle of the fan used for the dryer, the better the results would be obtained.

Experiment-Based Preliminary Design Guidelines for Consideration of Profile Vortex Shedding From Low-Speed Axial Fan Blades

Abstract This paper presents hot-wire measurements in a wind tunnel, close downstream of basic models of blade sections being representative for low-speed, low-Reynolds number axial fans, in order to explore the signatures of vortex shedding (VS) from the blade profiles. Using the Rankine-type vortex approach, an analytical model was developed on the velocity fluctuation represented by the vortex streets, as an aid in evaluating the experimental data. The signatures of profile VS were distinguished from blunt trailing-edge VS based on Strouhal numbers obtained from the measurements in a case-specific manner. Utilizing the experimental results, the semi-empirical model available in the literature for predicting the frequency of profile VS was extended to low-speed axial fan applications. On this basis, quantitative guidelines were developed for the consideration of profile VS in preliminary design of axial fans in the moderation of VS-induced blade vibration and noise emission.

Effect of Characteristic Phenomena and Temperature on Super-Cooled Large Droplet Icing on NACA0012 Airfoil and Axial Fan Blade

Icing simulations involving super-cooled large droplets (SLDs) on a NACA0012 airfoil and a commercial axial fan were performed considering the characteristic behavior of SLD icing (i.e., splash-bounce, deformation, and breakup). The simulations were performed considering weak coupling between flow field and droplet motion. The flow field was computed using the Eulerian method, wherein the droplet motion was simulated via the Lagrangian method. To represent the ice shape, an extended Messinger model was used for thermodynamic computation. The ice shape and collection efficiency of the NACA0012 airfoil derived using the icing simulation exhibited a reasonable agreement with the existing experimental data. The icing simulation results for the axial fan, in terms of distribution of ice on the blade and its influence on the flow field, indicated that flow separation occurred, and the mass flow rate of the flow passage decreased. Moreover, the splash and bounce phenomena considerably influenced the icing process; however, the effect of the deformation and breakup phenomena was negligibly small. In terms of the effect of the SLDs on the icing phenomena, it was noted that, with the decrease in the SLD temperature (from −5 °C to −15 °C), the number of adhering SLDs increased, whereas the number of splashing and bouncing SLDs decreased.

Investigation on Unstable Pressure Distribution of an Axial Fan Blade with Difference of Setting Angle and Chord Length

Investigation on Unstable Pressure Distribution of an Axial Fan Blade with Difference of Setting Angle and Chord Length

Simulation of the Deposit Evolution on a Fan Blade for Tunnel Ventilation

Abstract Fans used in tunnel ventilation operate for decades in an atmosphere that carries dust, soot, and other solid particles. The formation of deposit on the rotor blades, considering a so long time of exposition to this particle-laden flow, is highly probable. A not negligible quantity of deposited material can produce damages on the performance of the fan, but also mass unbalancing, which is potentially dangerous for the structural integrity of the fan components. We applied our simulation tool to study a case of deposition on a large axial fan blade, used for tunnel ventilation. The outcome of the study is a parametric map of fouled blade geometries, obtained by simulating the deposition process over the increasing quantity of ingested particles mixture. The final map correlates the level and shape of deposit to the overall amount of particle ingested by the fan in its operating life. The same map can be easily used to predict the time needed in a specific application to reach any specific deposit thickness. The evolution algorithm and simulation tools developed in the past years by the authors were applied to predict the modified geometry of eroded rotor blades. Here, the same framework is updated to simulate the deposit problem. We use an integrated multiphase solver, coupled with a geometry update method. The solver can iteratively simulate the flow field, compute the particle tracking, dispersion, and deposit processes, and modify the geometry (and mesh) according to the predicted deposit shape and rate.

Characterization of Glass/Jute Hybrid Fibre Reinforced Epoxy Composite for Axial Flow Fan Blade

Traditionally axial flow fan blades were manufactured by using metal alloys, but with the increase in blade size the blades grew heavier resulting in more vibrations during its working. It is impossible to manufacture the metallic blades to close tolerances making it uneconomical. Due to this dimensional instability, the metallic impeller fan blades are instead fabricated with glass fiber reinforced plastics (GFRP). To reduce the after effects of GFRP blades on the environment necessitates the partial reinforcement of natural fibre. This paper deals with the characterization of GFRP blade material with partial Jute reinforcements i.e., glass to jute (95:5) weight percentage and estimating the properties like tensile strength, bending strength, shear strength, fracture toughness. The conventional GFRP blade material has 14 layers of glass fibers in various forms. By placing jute layer at various positions in GFRP blade material the mechanical strengths were estimated and compared with conventional one.

Axial Air-cooled Road Wheel Design

Aiming at the problem of improving the reliability and thermal stealth of the road wheel on the tracked vehicle, an axial air-cooled road wheel structure scheme is proposed. The spokes of the road wheel are designed as the shape of the axial fan blade, and the kinematics analysis is carried out. The CAE software is used to simulate the flow field. The velocity field, pressure field, and axial flow at the maximum speed of the road wheel are obtained, and the result is compared with the wheel of the plane spoke.

A stabilized ALE method for computational fluid–structure interaction analysis of passive morphing in turbomachinery

Computational fluid–structure interaction (FSI) and flow analysis now have a significant role in design and performance evaluation of turbomachinery systems, such as wind turbines, fans, and turbochargers. With increasing scope and fidelity, computational analysis can help improve the design and performance. For example, it can help add a passive morphing attachment (MA) to the blades of an axial fan for the purpose of controlling the blade load and section stall. We present a stabilized Arbitrary Lagrangian–Eulerian (ALE) method for computational FSI analysis of passive morphing in turbomachinery. The main components of the method are the Streamline-Upwind/Petrov–Galerkin (SUPG) and Pressure-Stabilizing/Petrov–Galerkin (PSPG) stabilizations in the ALE framework, mesh moving with Jacobian-based stiffening, and block-iterative FSI coupling. The turbulent-flow nature of the analysis is handled with a Reynolds-Averaged Navier–Stokes (RANS) model and SUPG/PSPG stabilization, supplemented with the “DRDJ” stabilization. As the structure moves, the fluid mechanics mesh moves with the Jacobian-based stiffening method, which reduces the deformation of the smaller elements placed near the solid surfaces. The FSI coupling between the blocks of the fully-discretized equation system representing the fluid mechanics, structural mechanics, and mesh moving equations is handled with the block-iterative coupling method. We present two-dimensional (2D) and three-dimensional (3D) computational FSI studies for an MA added to an axial-fan blade. The results from the 2D study are used in determining the spanwise length of the MA in the 3D study.

A Trade-Off between Mechanical Strength and Erosive Wear Resistance in AlSi12CuMgNi Alloy Used to Manufacture Fan Blades for Underground Mines

The axial fan blades used in underground mines are usually manufactured in AlSi12CuMgNi alloy (EN AC 48000). They must have a high mechanical strength to withstand the stresses resulting from the rotation speed of the rotor and a high resistance to erosive wear caused by suspended particles from underground mining and transport operations. The aim of this paper is to determine the most suitable thermal treatment to simultaneously improve their mechanical strength and erosive wear resistance. To this end, two solution treatments at 525 °C with cooling in water were analysed, as well as several ageing times at 170 °C. The crystalline phases present in the as-cast state were quantified by X-ray diffraction following quenching and different ageing processes. Furthermore, erosion wear resistance was measured by means of compressed air blasting with corundum particles according to ASTM G76 (2004). The highest wear resistance was obtained in the as-cast state using gravity die casting, with the presence of Al4Cu2Mg8Si7 and Al3CuNi. This wear resistance was higher than that obtained after the ageing treatment. However, a trade-off between mechanical strength and wear resistance was observed after 12 h ageing, where the hardness obtained exceeded 160 HV and the wear resistance became similar to that obtained in the as-cast state.

Модификация математической модели напряженного состояния лопаток быстроходных осевых вентиляторов для горной промышленности

Модификация математической модели напряженного состояния лопаток быстроходных осевых вентиляторов для горной промышленности

Strength Analysis of a Ducted Axial Fan Blade

This paper presents a numerical strength analysis of a ducted axial fan blade. Ducted axial fans are a large group of fluid-flow machines. The analysis was designed to determine the causes of cyclic failures of a ventilation unit. The paper presents a reverse engineering approach to the mapping of the fan blade’s geometrical features. The geometrical features were mapped by triangulation from the scanning images produced by a 3D optical scanner. These were followed by simplifying assumptions on which the numerical calculations were based. The numerical calculations were carried out at the operating rotational speeds of the ducted axial fan’s rotor. The course of the numerical calculations is described, and their results are also presented herein. The results are represented on colour maps of stress distribution for selected structural elements of the fan blade. The stress distribution at a blade cross-section was compared to CT scans of the fractures of failed rotor blade airfoils. Final conclusions were developed which show that the design engineering process of fans should feature optimisation of the fan’s efficiency, including the strength and performance parameters, which should include the service life of the fan.

Design and performance of low-pressure reversible axial fan with doubly curved profiles of blades

Reversible axial fans are used to achieve air (gas) flow in both directions. An axial fan only has an impeller that can achieve the reverse flow by changing the direction of the impeller rotation. In order to obtain the same performance for both directions, the profiles of the impeller blades should be completely symmetrical, in the shape of the ellipse. This paper presents the design and performance for a reversible axial fan with blades that have a slightly doubly curved profile. The shape of the profile, whose design is shown here, was previously obtained on the basis of the numerical simulation in the profile cascade. For the experimental tests, an axial reversible fan model with double curved profiles of the blades was made. Fan performance was obtained by testing a fan for three blade positions on a standard test installation. The performance curves were compared with the performance of the reversible axial fan blades with straight profiles. The fan with doubly curved profile blades achieved a greater increase in pressure and flow than the fan with straight profiles, with approximately the same efficiency. Low pressure axial reversible fans are used in drying chambers for wood and such a design can achieve higher drying efficiency.

Lift and drag force measurements on basic models of low-speed axial fan blade sections

This paper presents comparative data on the aerodynamic lift and drag of basic model representations of low-speed axial fan blade sections. Three main types of blades are investigated: flat plate, cambered plate and RAF6-E profiled airfoil. Lift and drag force are measured at three different Reynolds numbers (0.6 × 105, 105 and 1.4 × 105) around the threshold value of 105. The measurement data are compared to literature data. The aerodynamic force measurements reveal that, for Reynolds numbers below 105, cambered plate blade sections can be superior to airfoil profiles in terms of aerodynamic efficiency, especially in the high-load range. The effect of leading edge bluntness is also investigated. Leaving the leading edge of cambered plates blunt, tends to be uncritical for low Reynolds numbers at angles of attack between 4° and 10° but is critical at angles between 0° and 4°.

Numerical Testing of a Trailing Edge Passive Morphing Control for Large Axial Fan Blades

The concept of morphing geometry to control and stabilize the flow has been proposed and applied in several aeronautic and wind turbine applications. We studied the effect of a similar passive system applied on an axial fan blade, analyzing potential benefits and disadvantages associated to the passive coupling between fluid and structure dynamics. The present work completes a previous study made at the section level, giving a view also on the three-dimensional (3D) effects. We use the numerical computation to simulate the system, which defines a complex fluid–structure interaction (FSI) problem. In order to do that, an in-house finite element (FE) solver, already used in the previous study, is applied to solve the coupled dynamics.

Establishment of a Beamforming Dataset on Basic Models of Low-Speed Axial Fan Blade Sections

The paper presents wind tunnel experiments, supplemented with phased array microphone measurements, on 2D basic models of low-speed axial fan blade sections: a flat plate, a cambered plate, and a RAF6-E airfoil. It aims at documenting the establishment of an acoustic beamforming dataset for the three profiles. The phased array microphone measurements offer spatially resolved information on the generated noise. The measurement setup enables the correlation of the streamwise evolution of the blade boundary layer with the associated noise characteristics. The dataset incorporates a wide range of incidence and Reynolds-numbers investigated. The present paper is confined to reporting on experimental results for arbitrarily selected representative incidences, Reynolds numbers, frequency bands, and profiles. The paper outlines a methodology for the evaluation and representation of the beamforming data in the following forms: source strength level based third-octave spectra obtained using background noise subtraction; maps presenting the loci of source strength level maxima; noise source maps for frequency bands of anticipated vortex shedding noise.

Antenna geometry effect on the reconstruction of the unsteady rotating forces of axial fan blade

The aim of this paper is to investigate the influence of the geometrical arrangement of acoustic pressure measurement sensors on the reconstruction of the unsteady rotating forces acting on the fluid by the fan’s blade. A development based on the tonal noise generated by an axial fan and validated with a directivity experience is used to derive a discretized form of the direct problem and to simulate acoustic pressures at known spatial positions in the radiated field. The inverse problem is usually ill-posed and requires optimization technique to stabilize the solution for small perturbations in the measured acoustic input data. The reconstruction shows that the inverse problem conditioning depends on the aeroacoustic source and the far-field sensor number and geometrical distribution as well as on the studied frequency. Tikhonov regularization can provide an appropriate regularization parameter leading to a satisfactory reconstruction of imposed unsteady rotating forces even in the presence of measurement noise. Simulations are conducted for three geometrical arrangements of microphones: line, arc of a circle and square.

Design of Mixed flow Fan with Rapid Prototyping Method for Acoustics Performance

Objectives: In this work Rapid prototype model is used to reduce the noise of an axial cooling fan. Methods/Analysis: Reverse engineering is considered for modeling the fan and computational fluid dynamics methods are applied to the existing fan to evaluate the noise levels. Changed the existed axial fan blade profile with NACA 63-006 airfoil to decrease noise levels. The local flow field of the fan was computed with rapid prototype model. The flow patterns throughout the fan are visualized using numerical techniques. Findings: By decreasing the no. of blades with airfoil cross section, noise is reduced and also increased fan performance. The overall sound intensity levels are observed for modified fan a series of NACA Airfoil and it has been observed that the minimum noise level of NACA 63-006 RPT fan is 60.5 dB. Novelty/ Improvement: Large broadband noise reduction is obtained due to RPT fan a NACA 63-006 airfoil profile of blade geometry.

A Shape Memory Alloy-based Morphing Axial Fan Blade: Functional Characterization and Perspectives

In a traditional automotive cooling system, energy optimization could be achieved by controlling the engine temperature by means of several sensors placed inside the cooling circuit. Nevertheless, in some cases the increasing use of a great number of sensor devices makes the control system too bulky, expensive and not sufficiently robust for the intended application. This paper presents the development of a heavy-duty automotive cooling axial fan with morphing blades activated by Shape Memory Alloy (SMA) strips that work as actuator elements in the polymeric blade structure. The blade was designed to achieve the activation of the strips (thermo-mechanically treated on purpose) by means of an air stream flow. With the aimof studying the morphing capability of the adaptive structure together with the recovery behavior of the NiTi strips, four different polymeric compounds have been compared in a specifically-designed wind tunnel. As the airstream flow increases its temperature, the strips recover the memorized bent shape, leading to a camber variation. To study the possibility of employing SMA strips as actuator elements, a comparison with common viscous clutchbehavior is proposed. The time range actuator response indicates that the SMA strips provide a lower frequency control that fits well with the engine coolant thermal requirement. The experimental results demonstrate the capability of SMA materials to accommodate the lower power actuators in the automotive field. This innovative passive control system results from the selection of (i) the memorized shape of the SMA strips and (ii) the polymeric compound used for the blade structure.

A Shape Memory Alloy-Based Morphing Axial Fan Blade—Part II: Blade Shape and Computational Fluid Dynamics Analyses

The ability of a morphing blade to change its geometry according to the different operating conditions represents a challenging approach for the optimization of turbomachinery performance. In this paper, experimental and computational fluid dynamics (CFD) numerical analyses on a morphing blade for a heavy-duty automotive cooling axial fan are proposed. Starting from the experimental results proposed in the first part of this work, a morphing blade, made of shape memory alloy (SMA) strips embedded in a polymeric structure, was thoroughly tested. In order to assess the ability of the strips to reach a progressive and smooth shape changing evolution, several experiments were performed in a purpose-built wind tunnel. The morphing blade changed its shape as the strips were thermally activated by means of air stream flow. The bending deformation evolution with the increasing number of thermal cycles was evaluated by digital image analysis techniques. After the analyses in the wind tunnel, CFD numerical simulations of a partially shrouded fan composed of five morphing blades were performed in order to highlight the evolution of the fan performance according to air temperature conditions. In particular, the capability of the blade activation was evaluated by the comparison between the fan performance with nonactivated blades and with activated blades. The results show a progressive stabilization of the shape memory behavior after the first cycle. The blade deformation led to a significant improvement in the fan performance at a constant rotational velocity. The CFD numerical simulation points out the differences in the overall performance and of three-dimensional fluid dynamic behavior of the fan. This innovative concept is aimed at realizing a sensorless smart fan control, permitting (i) an energy saving that leads to fuel saving in the automotive application fields and (ii) an increase in engine life, thanks to a strong relationship between the engine thermal request and the cooling fan performance.

A Shape Memory Alloy-Based Morphing Axial Fan Blade—Part I: Blade Structure Design and Functional Characterization

The possibility to realize adaptive structures is of great interest in turbomachinery design, owing to the benefits related to enhanced performance and efficiency. To accomplish this, a challenging approach is the employment of shape memory alloys (SMAs), which can recover seemingly permanent strains by solid phase transformations whereby the so-called shape memory effect (SME) takes place. This paper presents the development of a heavy-duty automotive cooling axial fan with morphing blades activated by SMA strips that works as actuator elements in the polymeric blade structure. Concerning the fan performance, this new concept differs from a conventional viscous fan clutch solution especially during the nonstationary operating conditions. The blade design was performed in order to achieve the thermal activation of the strips by means of air stream flow. Two polymeric matrices were chosen to be tested in conjunction with a commercially available NiTi binary alloy, whose phase transformation temperatures (TTRs) were experimentally evaluated by imposing the actual operating thermal gradient. The SMA strips were then thermomechanically treated to memorize a bent shape and embedded in the polymeric blade. In a specifically designed wind tunnel, the different polymeric matrices equipped with the SMA strips were tested to assess the fluid temperature and surface pattern behavior of the blade. Upon heating, they tend to recover the memorized shape and the blade is forced to bend, leading to a camber variation and a trailing edge displacement. The recovery behavior of each composite structure (polymeric matrix with the SMA strips) was evaluated through digital image analysis techniques. The differences between the blade shape at the initial condition and at the maximum bending deformation were considered. According to these results, the best coupling of SMA strips and polymeric structure is assessed and its timewise behavior is compared to the traditional timewise behavior of a viscous fan clutch.