Fan Diameter Research Articles

CONTROL OF SHROUD LEAKAGE LOSS AND WINDAGE TORQUE IN A LOW-PRESSURE TURBINE STAGE

Abstract As new aeroengine architectures move to larger diameter fans and rotors, the associated increase in weight will need to be counterbalanced by lighter, more compact, and more efficient low-pressure turbines (LPT). Efficiency gains in LPTs can be achieved by reducing the losses associated with the shroud leakage flows. Flow control studies on the topic have traditionally focused on reducing the mixing loss, which constitutes a considerable proportion of the total loss. Nonetheless, increasing engine speeds are driving additional gains obtained by also targeting the reduction of windage losses. Developing a flow control solution with the dual objective of reducing over-tip cavity mixing and windage losses has not previously been attempted. This is a challenge due to conflicting flow control requirements and geometric constraints. Reducing windage loss generally requires increasing the swirl-ratio of the leakage flow, while reducing mixing loss requires reducing this ratio to match that of the main gas path. The current work proposes a novel flow control solution to successfully achieve this purpose through the emerging technology of additive manufacturing. The successful flow control concept was developed through numerical simulation, printed using an additive manufacturing process, and validated in a purpose-built rig. Experiments and computations were consistent with a cumulative reduction in cavity windage of 16%. The FCC is estimated to increase the mechanical efficiency of the turbine stage in isolation by 1%.

A model-based design approach for low-pressure axial fan blades considering the air flow system characteristics

The paper puts forward a computer methodology for designing low-pressure axial fan blades for small-capacity refrigeration applications. Based on the blade element theory (BET), the airfoil efficiency of the airfoil, the principles of mass and momentum conservation together with empirical correlations for the flow irreversibilities, a mathematical model was devised for screening the blade geometric parameters (e.g., radial chord and pitch variation, and hub radius) by varying the induction coefficient distribution for a given fan diameter, motor speed, and airflow system characteristic curve. The best blade configuration is selected by means of a tailor-made optimization algorithm and undergoes a series of linear transformations for translating the fan parametrization into a CAD drawing. Two new fan blades were designed, one for maximum blade efficiency (MBE) and another for maximum airflow rate (MAR). In comparison with the free-swirl design approach, a standard procedure adopted in the open literature, the proposed blades showed an efficiency and an airflow by 20 % (MBE) and 14 % (MAR) higher than the reference. The airflow characteristics of the new designs were also assessed by means of wind-tunnel testing, which confirmed an increase of 11 % in the case of MBE design, while an enhancement of 10 % was observed in the case of MAR design.

Assessment of a body force modeling approach to examine the aerodynamics of high bypass ratio fan stages

The primary focus of modern civil jet engine intake design is to enhance propulsive efficiency through an increase in the bypass ratio of the turbofan engine, which requires an enlargement in fan diameter. However, this enlargement results in increased weight and drag due to the need for a larger nacelle to surround the fan. To mitigate these issues, efforts are being made to shorten the axial length of the aircraft engine intakes. Nonetheless, this reduction leads to more vulnerable fan aerodynamics since the diffusion within the intake must occur over a shorter distance, causing a higher possibility of flow separation. Common intake design methods employ throughflow nacelle models that do not consider the aerodynamic effects of the fan, including blockage, mass flow redistribution, and suction. The utilization of a full annulus domain numerical setup, which is necessary to capture inlet distortions, demands excessive computational resources particularly during the design phase. As a result, reduced order models, such as the body force model, can be utilized to simulate fan intake aerodynamics. This paper will assess the body force model and its abilities by comparing conventional bladed single passage simulations with the body force approach.

Study on the Influence of High-Altitude Helical Tunnel Curvature on Jet Fan Spatial Layout

During the operational ventilation process of high-altitude helical tunnels, the installation method of jet fans is a key factor in determining the ventilation efficiency of the tunnel. In this study, the CFD numerical simulation method is adopted to establish three-dimensional ventilation models of helical tunnels with different curvature radii. Through orthogonal experiments, the effects of tunnel curvature radius on the characteristics of the air jet flow field, under the coupled influences of factors such as lateral spacing of jet fans, vertical height of fans, longitudinal spacing, and lateral offset, are investigated. The results show that when R = 500 m, 600 m, 700 m, and 800 m, the longitudinal spacing has the most significant impact on ventilation efficiency, followed by vertical height, with lateral offset and fan spacing having the least impact. The optimal spacing and vertical height of the fan groups remain consistent under different curvature radii, at 1.25D (fan diameter) and 15 cm, respectively. The optimal longitudinal spacing of the fan groups is 90 m, 90 m, 135 m, and 90 m, respectively. Shifting the fan groups 0.25 to 0.75 m towards the inner side of the tunnel helix (for R < 700 m) can optimize the flow field distribution within the tunnel. Finally, expressions for the relationship between the helical radius and the lateral offset and longitudinal spacing of the fan groups are established for the optimal installation parameters of fan spatial positions under different helical tunnel radii.

Evaluation of the effects of various fan parameters on the cooking process in commercial cooking ovens

Commercial kitchen ovens are utilized in various capacities and models within commercial enterprises, operating on either electric or gas power. Numerous parameters affect the cooking process. Particularly, for effective cooking in an oven, it’s crucial to evenly distribute airflow over the food. Correct airflow significantly impacts the cooking process. Considering the differences in processing requirements based on the characteristics and quantity of the food (such as temperature, humidity, fan speed, duration, etc.), the method of heat transfer should be primarily assessed. Non-uniform distribution of hot air during the cooking process leads to varied cooking qualities among trays within the oven. Therefore, in achieving effective cooking, factors like oven cavity, number of trays, fan geometry, fan rotation speed, direction, movement intervals, and the turbulent airflow generated by the fan in the cooking chamber need thorough examination. This study analyzed simulation data evaluating the effects of different fan geometries, fan rotation directions, and timing on heat transfer in a prototype electric commercial cooking oven using gastronomic GN-1/1 sized with 10 trays. Additionally, comparison of test and design validation data in the specially developed prototype cooking oven was conducted. Assessments were made with different fan movements (fan diameters, rotation direction, speed etc.) and a fan protection plate in front of the oven to achieve more efficient heat distribution on the food. Depending on various fan parameters, this study contributed to reducing energy consumption in the prototype commercial cooking oven.

Flight analysis and optimization design of vectored thrust eVTOL based on cooperative flight/propulsion control

The rise of electric vertical take-off and landing (eVTOL) aircraft has sparked research interest, but attention to modeling and evaluation methods, particularly for vectored thrust eVTOL, lags behind. The intricate flight/propulsion coupling and structure/control complexity contribute to the gap. Moreover, integrated modeling and evaluation processes for vectored thrust eVTOL should fully account for the tilting characteristics of the fan/propeller. This paper proposes a flight/propulsion cooperative control modeling and evaluation method for vectored thrust eVTOL. The methodology uses the Gaussian pseudospectral trajectory optimization method to obtain the overall characteristics and cooperative control strategy of flight/propulsion under strict take-off and landing trajectory constraints. Besides, this paper yielded the parameterized analysis and matching optimization design of the propulsion system. Results indicated that for an aircraft with a take-off weight of 1.8 tons, equipped with four 1.6 m diameter tilting ducted fans and a single discharge rate 5C battery, its cruising range is 135.1 km based on the selected technical parameters. The power consumption accounts for merely 12.6% of the total battery capacity during the take-off phase with high-power demand but short duration. By employing a pack of high-power-density and high-energy-density batteries to drive the ducted fans jointly, the aircraft's cruising range, fan size, and payload can be optimized. The 20C+2C battery scheme can either increase the cruising range by 27.3% without changing the fan diameter or increase the cruising range by 6.1% when the fan diameter is reduced to 1.1 m. Wherein without changing the fan diameter, the battery mass can be reduced from 720 kg to 571 kg while satisfying the takeoff and cruising requirements. The results demonstrated the effectiveness of improving the cruising range and optimizing the fan size and payload.

Aerodynamic Analysis of Low-Pressure Axial Fans Installed in Parallel

Abstract Ducted rotor-only low-pressure axial fans play an integral role in automotive thermal management. The tightly packed under-hood region and down-stream heat-exchanger shape limit the fan diameter. In order to circumvent this limitation, multiple cooling fans of small diameters are tightly packaged and placed in parallel. Currently, there is limited scientific work, that study the aerodynamics of low-pressure axial fans when installed in parallel. This work aims to quantify the aerodynamic performance and the flow-field as a result of installing low-pressure axial fans in parallel through computational fluid dynamics (CFD). Publicly available experimental data from Friedrich-Alexander University is used for the validation of the numerical setup. Three-dimensional, full-annulus, unsteady Reynolds-averaged Navier-Stokes (URANS) analysis has been performed for both a single-fan and two-fans installed in parallel and their respective aerodynamic performance has been compared for the operation condition identified as the best efficiency point in experiments. Only small differences are observed in the overall aerodynamic performance of the two-fans in parallel compared to a single-fan. A circumferential nonuniformity in the form of a local high-pressure zone at the inlet of the fan is observed when the two-fans are placed in parallel. The resulting circumferential nonuniformity is quantified, both in space and time. A strong correlation is found between the pressure fields of the two-fans installed in parallel.

Effect of Unsteady Fan-Intake Interaction on Short Intake Design

Abstract The next generation of ultrahigh bypass ratio civil aero-engines promises notable engine cycle benefits. However, these benefits can be significantly eroded by a possible increase in nacelle weight and drag due to the typical larger fan diameters. More compact nacelles, with shorter intakes, may be required to enable a net reduction in aero-engine fuel burn. The aim of this paper is to assess the influence of the design style of short intakes on the unsteady interaction under crosswind conditions between fan and intake, with a focus on the separation onset and characteristics of the boundary layer within the intake. Three intake designs were assessed, and a hierarchical computational fluid dynamics (CFD) approach was used to determine and quantify primary aerodynamic interactions between the fan and the intake design. Similar to previous findings for a specific intake configuration, both intake flow unsteadiness and the unsteady upstream perturbations from the fan have a detrimental effect on the separation onset for the range of intake designs. The separation of the boundary layer within the intake was shock driven for the three different design styles. The simulations also quantified the unsteady intake flows with an emphasis on the spectral characteristics and engine-order signatures of the flow distortion. Overall, this work showed that is beneficial for the intake boundary layer to delay the diffusion closer to the fan and reduce the preshock Mach number to mitigate the adverse unsteady interaction between the fan and the shock.

Design optimisation of non-axisymmetric exhausts for installed civil aero-engines

Future civil aero-engines are likely to operate with higher bypass-ratios (BPR) than current power-plants to improve propulsive efficiency and reduce specific thrust. This will probably be accompanied by an increase of fan diameter and size of the power plant. Consequently, future configurations are likely to require more close-coupled installations with the airframe due to structural and ground clearance requirements. This tendency may lead to an increase in the adverse installation effects which could be mitigated with non-axisymmetric exhausts. However, due to the prohibitive computational cost, limited regions of the design space have been studied. For this reason, a relatively low-cost design approach for the integrated system is required. The aim of this work is to establish a method to map the non-axisymmetric exhaust design space where the effects of the propulsion system installation are taken into account. The methodology relies on the generation of a design database using inviscid computational fluid dynamics (CFD) methods. This is used to characterise the design space, identify the dominant design parameters and build response surface models for optimisation. The candidate designs that arise from the optimisation are assessed with viscous CFD simulations to assess the aerodynamic mechanisms and performance characteristics. The result is a set of design recommendations for installed configurations with non-axisymmetric exhausts. The method is an enabler for the optimisation of installed propulsion systems and has provided an exhaust design with a 0.7% improvement on net vehicle force relative to an axisymmetric exhaust, for a close coupled configuration where the fan cowl is overlapped with the wing. A reduction in net vehicle force is expected to lead to a similar reduction in cruise fuel burn.

Performance Assessment of a Higher Bypass Ratio Engine Installation on a Rear-mounted Regional Aircraft

The unceasing growth of the bypass ratio of civil aircraft engines reduces the specific fuel consumption while simultaneously complicating engine installation. This paper assesses the cumulative advantages of employing engines with superior bypass ratios in rear-mounted regional aircraft. The aerodynamic analysis of the engine intake and exhaust ramifications is based on the RANS CFD methodology, validated by the NASA CRM model and AIAA DSFRN model. An engine cycle model was developed to supply the engine inlet and outlet conditions for CFD calculations. In the case of the rear-mounted regional aircraft scrutinized herein, the fan diameter expanded from 53 inches to 60 inches, with the bypass ratio escalating from 5.3 to 11. This resulted in a roughly 9.33% reduction in specific fuel consumption. Nonetheless, the adverse impact of engine dimensions counteracts the cycle advantages, culminating in a 4.23% decrease in the aircraft’s lift-to-drag ratio and an aggregate benefit of 5.62%.

Estimating cooling capacities from aerial images using convolutional neural networks

In recent decades, the global cooling demand has significantly increased and is expected to grow even further in the future. However, knowledge regarding the spatial distribution of cooling demand is sparse. Most existing studies are based on statistical modelling, which lack in small-scale details and cannot accurately identify individual large cooling producers. In this study, we implement and apply a novel method to identify, map and estimate nominal cooling capacities of chillers using deep learning. Chillers typically use air-cooled condensers and cooling towers to release excess heat, and produce most of the cooling needs in the commercial and industrial sectors. In this study, these units are identified from aerial images using specifically trained object detection models. The corresponding nominal cooling capacity is then estimated based on the number of fans of air-cooled condensers and the fan diameters of the cooling towers, respectively. Both detection and capacity estimations are first evaluated on test data sets and subsequently applied to an industrial area (Brühl) and the city center in Freiburg, Germany. In Brühl, aerial images show chillers with an estimated nominal cooling capacity of 205 MW, of which the model detected 88%, while 88% of all detections are correct. In the city center, a nominal capacity of 18.6 MW is estimated, of which the model detected 87% with 77% of all detections being correct. Hence, the developed approach facilitates a reliable analysis of the installed nominal cooling capacity of individual buildings at large scales, such as districts and cities. This information could be further used to locate areas for investments and support planning of eco-friendly, centralized supply of cooling energy, for example district heating and cooling systems or shallow geothermal energy systems such as aquifer thermal energy storage (ATES).

Experimental noise reduction (aeroacoustical enhancement) of a large diameter axial flow cooling fan through a reduction in blade tip clearance

Aerodynamic and aeroacoustic performance experiments were carried out on four- and eight bladed, 1.542 m diameter, axial flow cooling fans, with constant solidity and hub-to-tip ratio. Tests were conducted in an ISO5801, Type A Fan Test facility. The tip gap (TG) was reduced from 4 mm (0.26% fan diameter) to 2 mm (0.13% fan diameter), to 0 mm, for both fan configurations. The noise profile of each fan configuration at the same TG over the whole volumetric flow rate spectrum was compared to each other. The 4 mm (0.26%) TG is used as a baseline to measure the nett increase or decrease in sound levels. Noise emissions decreased as the TG was reduced. It is discovered that the four bladed fan configuration had lower noise emissions than the eight bladed fan configuration at all blade tip clearances at design flow rate. It is concluded that reducing the TG and number of blades, at constant solidity, reduces sound emissions. The 0 mm TG for the four bladed fan produced the greatest reduction in noise emissions. An increase in fan total-to-static performance is observed when reducing the TG for both fan configurations.

Acoustic Dissipation and Modal Coupling in Server Computers

Interest in the interior acoustics of server computers is growing as noise generated by air movers (fans) is increasingly observed to impact the performance of hard disk drives (HDD) inside these computers. In a typical server, a backplane cavity is located between an array of air movers and an array of HDD such that the HDD may be within a fan diameter of the air movers. The possibility of functional degradation requires careful management of air mover noise with respect to HDD susceptibility to acoustic noise disturbances and motivates understanding the physical phenomena underlying the acoustics. A previous investigation demonstrated the importance of coherence between acoustic standing wave modes in the backplane cavity. In this paper server interior airborne acoustics are further investigated by focusing on acoustic dissipation and inter-modal coupling in the backplane cavity. Various dissipation models are developed and used in conjunction with a previously formulated modal cavity acoustic model to generate cavity transfer factors. The transfer factor predictions are compared to measured transfer factors to draw further insights into the physical phenomena governing the interior cavity acoustics.

The Ford Rolling Road Wind Tunnel Facility

<div class="section abstract"><div class="htmlview paragraph">The Ford Motor Company Rolling Road Wind Tunnel (RRWT) is a state-of-the-art aerodynamic wind tunnel test facility in Allen Park, Michigan. The RRWT has operated since January 2022 and is designed for passenger and motorsport vehicle development. The test facility includes an office area, three secure customer vehicle preparation bays, a garage area, a vehicle frontal area measurement system, and a full-scale ¾ open jet wind tunnel. The wind tunnel features an interchangeable single belt and 5-belt Moving Ground Plane (MGP) system with an integrated 6-component balance, a two-position nozzle, boundary layer removal systems, and two independent flow traverse systems. Each flow traverse has a large horizontal box beam and vertical Z-strut that can position the flow traverse accurately within the test volume. The individual traverse systems can also operate in tandem and have the capability to perform stereo PIV measurements and scale model vehicle testing, including vehicle passing or drafting simulations. The MGP can be quickly changed between single belt and 5-belt operations, requiring only a single eight-hour shift to transition between the two configurations. The efficient wind tunnel airline is capable of airspeeds up to 250 km/h in the large 26.4 m<sup>2</sup> nozzle configuration and 322 km/h in the small 18.6 m<sup>2</sup> nozzle configuration using a 12-blade, 8 m diameter fan with a 5.4 MW motor. The wind tunnel’s flow quality and aerodynamic performance compare well with similar facilities in the automotive industry. Ford Motor Company is currently correlating aerodynamic measurement data from the RRWT with other similar facilities, using 60 vehicles across multiple product lines.</div></div>

Noise Control in Air Mechanical Ventilation Systems with Three-Dimensional Metamaterials

The diffusion of mechanical ventilation systems increased rapidly due to the climate changes in all parts of the world. The mechanical ventilation systems are mainly used in the summer for many difficulties to face very hot temperatures. One of the biggest problems considered if every residential unit is equipped with a mechanical ventilation system is the generation of noise by the rotating blades of the fan for refrigeration. This paper discusses the applications of metamaterials to create attenuation filters to be installed inside the encases of the mechanical ventilation systems in order to obtain sound attenuation. A three-dimensional reticular structure made with spheres has been studied in different configurations related to the numbers of layers employed. The sound attenuations were measured at some specific octaves, depending on the particular configurations. In general, the sound attenuation peaks have been measured between 4 kHz and 8 kHz; this is expected to mitigate the tonal noise component typical of fans based on different variables that compose the whole system (e.g., fan diameter, number of blades, fan speed). However, the outcomes shall be considered in terms of laboratory conditions since material properties of the enclosure and potential polarization effects due to reflection of sound waves at the boundaries may occur.

Design optimization of bladeless ceiling fan using design of experiments

— The design technology in the world of fans has been revolutionized by the invention of bladeless fans in recent years. Bladeless fans are unique in shape and highly efficient in performance. At present, a bladeless ceiling fan on the concept of bladeless Air-Multiplier is not available. The present study intends to find an optimized geometry for the bladeless ceiling fan which is comparable to a conventional fan. Design of Experiments analysis was followed in the present study and found that a fan diameter of 1.4 m, jet width of 2.55 mm, jet orientation of 91.21o, and jet velocity of 3 m/s are the optimized parameter for a bladeless fan within the applied constraints. An average velocity of 1.32 m/s and a velocity spread of 76% were calculated during CFD simulations. The results were compared with the experimental data of conventional ceiling fans and a 60% enhancement in air delivery values were recorded for the bladeless fan. It is concluded that the answer to the future economical ceiling fan lies in the application of bladeless technologies.

Combining Deep Neural Network with Genetic Algorithm for Axial Flow Fan Design and Development

Axial flow fans are commonly used for a system or machinery cooling process. It also used for ventilating warehouses, factories, and garages. In the fan manufacturing industry, the demand for varying fan operating points makes design parameters complicated because many design parameters affect the fan performance. This study combines the deep neural network (DNN) with a genetic algorithm (GA) for axial flow design and development. The characteristic fan curve (P-Q Curve) can be generated when the relevant fan parameters are imported into this system. The system parameters can be adjusted to achieve the required characteristic curve. After the wind tunnel test is performed for verification, the data are integrated and corrected to reduce manufacturing costs and design time. This study discusses a small axial flow fan NACA and analyzes fan features, such as the blade root chord length, blade tip chord length, pitch angle, twist angle, fan diameter, and blade number. Afterwards, the wind tunnel performance test was performed and the fan performance curve obtained. The feature and performance test data were discussed using deep learning. The Python programming language was used for programming and the data were trained repeatedly. The greater the number of parameter data, the more accurate the prediction. Whether the performance condition is met could be learnt from the training result. All parameters were calculated using a genetic algorithm. The optimized fan features and performance were screened out to implement the intelligent fan design. This method can solve many fan suppliers’ fan design problems.

Structural optimization of engine nacelle fan cowl door hinge

To increase propulsive efficiency, future nacelle engines are projected to run at low specific thrust with large bypass ratios. Typically, this entails a larger fan diameter and nacelle, as well as increased drag and weight penalties. As a result, there is a need to construct more compact, nacelles’ components in comparison to present designs in order to minimize drag and weight. These designs are naturally more difficult, necessitating the use of a system to explore and identify the design area that is possible. Designing a nacelle is difficult due to the wide range of operational circumstances. This paper provides a multi-objective optimization technique for fan cowl door component of nacelle design utilizing an evolving genetic algorithm. A collection of geometry definitions utilizing Class Shape Transformations, automated simulation and analysis, a generic algorithm, assessments at various nacelle operating circumstances, and the addition of extra aerodynamic restrictions are all part of the unique framework. This framework was used to look into the nacelle design space for nacelle components. For the new nacelle component design challenge, multi-objective optimization was successfully shown, and the entire system was proved to allow the discovery of the feasible nacelle design space. Moreover, in this paper a series of fan cowl door hinge is designed from the scratch and optimized step by step for reducing the weight of the component without compromising for the stress capacity and load transformations within the allowable limit.

Local and overall convective heat transfer coefficients for human body with air ventilation clothing: Parametric study and correlations

Convective heat transfer coefficient associated with various human body parts plays an important role in the prediction of physiological responses with the help of human thermoregulation models. The primary goal of this work is to develop correlations for the convective heat transfer coefficients associated with various segments and whole torso of the human body in sleeve opening (SO), collar opening (CO), and both sleeve and collar opening (SCO) scenarios of air ventilation clothing. For this, a 3D CFD model of the air ventilation clothing is developed and validated with experimental data. Detailed parametric study is performed to analyze effect of openings in the air ventilation clothing, air flow rate, fan diameter and inlet (ambient) air temperature on the local and overall convective heat transfer coefficients. Results indicate that the area-weighted average convective heat transfer coefficient associated with whole torso is 36% and 5% higher in the case of CO and SCO, respectively, as compared to the SO case. The convective heat transfer coefficient is highest in the lower-back segment and lowest in the upper-chest segment of the body for SO and SCO scenarios. Whereas in CO scenario, the upper-chest segment has the highest and stomach segment has the lowest convective heat transfer coefficients. Effects of fan diameter and inlet air temperature are found to be least significant on the convective heat transfer coefficients as compared to the effect of opening and air flow rate. Further, correlations for segment-wise and whole torso convective heat transfer coefficients are proposed in the present work.

Aerodynamics of a short intake in crosswind

The next generation of turbofan aero-engines are likely to have an increase in fan diameter to reduce the specific thrust and increase the overall propulsive efficiency. More compact nacelles with possibly shorter intakes may be used to reduce weight and drag and achieve a net reduction of fuel consumption. For these compact nacelles a key consideration is the design of the short intake at the off-design conditions such as crosswind and high incidence operations. The close coupled interaction between a short intake and the fan at these off-design conditions is one of the key challenges. Previous work focused on the impact of short intake aerodynamics on the fan but there is a similar requirement to understand the impact of the fan on the viable short intake design space. This paper addresses the influence of the fan on the separation onset of the flow within a short intake under crosswind conditions. The effect of the fan on the separation characteristics of the intake boundary layer was considered both from a steady and an unsteady point of view. A hierarchy of fan computational models was used to separately assess the different aerodynamic contributions and to evaluate a net effect of the fan on the intake critical condition. Steady computational fluid dynamics analyses showed a notable positive effect of the fan on total pressure loss at post-separation conditions relative to a configuration without the fan. However, unsteady analyses revealed that fan unsteadiness has an adverse impact on the intake separation characteristics which reduces the intake critical conditions by about 15%. The main mechanisms behind the unsteady interaction were identified. Overall this work addresses, for the first time, the role of fan unsteadiness on the separation characteristics of the boundary layer within a short intake in crosswind.