Axial flow fans,

This paper presents a new single empirical equation for calculating fan air velocity at any given distance away from the fan at any point on the fan’s face. The results are valid for standard axial fan sizes used in the electronics industry ranging from 15x15 mm to 140x140 mm. Additionally, velocity profile curves are presented so engineers can easily decide the best position of the target being cooled relative to the fan’s cross-sectional area.

The paper presents a historical overview of the developments of aerodynamic design methods for low-speed axial-flow fans. This historical overview starts from the first fan applications, dating back to the 16th century, and arrives to the modern times of computer-based design techniques, passing through the pioneering times of aerodynamic theories and the times of designing before computers. The overview shows that the major achievements in the axial fan design discipline have actually been related to other technological fields, such as marine and aeronautical propulsion, as well as to the development of wind tunnels. At the end of the paper, the reader will have acquired a complete panorama of how the historical developments of the discipline have brought us to the current state of the art.

Axial fans are used in almost all forms of built environment where life exists. The selection of axial fan is based on several factors such as pressure, airflow and efficiency. The environment of the location of the axial fans play a major role in the efficiency and the life period of the fan. Some the external factors such as increase in pressure and pollution cannot be eliminated in the environment which might lead to stalling condition. Although stalling condition cannot be eliminated in axial fans, it can be detected in early stages and external sources or change in designs could reduce the probability of fan getting induced to stall condition. This paper explains the method calculation the performance of the fan and analyzing its operating condition and solutions to overcome the stalling the fan might accidentally get into which reduces the efficiency or sometimes the fan itself.

An axial flow fan, which is applied for ventilation in underground spaces such as tunnels, features a medium-large size, and most of the blades go through the casting process in consideration of mass production and cost. In the casting process, post-work related to roughness treatment is essential, and this is a final operation to determine the thickness profile of an airfoil which is designed from the empirical equation. In this study, the effect of the thickness profile of an airfoil on the performance and aerodynamic characteristics of the axial fan was examined through numerical analysis with the commercial code, ANSYS CFX. In order to conduct the sensitivity analysis on the effect of the maximum thickness position for each span on the performance at the design flow rate, the design of experiments (DOE) method was applied with a full factorial design as an additional attempt. The energy loss near the shroud span was confirmed with a quantified value for the tip leakage flow (TLF) rate through the tip clearance, and the trajectory of the TLF was observed on the two-dimensional (2D) coordinates system. The trajectory of the TLF matched well with the tendency of the calculated angle and correlated with the intensity of the turbulence kinetic energy (TKE) distribution. However, a correlation between the TLF rate and TKE could not be established. Meanwhile, the Q-criterion method was applied to specifically initiate the distribution of flow separation and inlet recirculation. The location accompanying the energy loss was mutually confirmed with the axial coordinates. Additionally, the nonuniform blade loading distribution, which was more severe as the maximum thickness position moved toward the leading edge (LE), could be improved significantly as the thickness near the trailing edge (TE) became thinner. The validation for the numerical analysis results was performed through a model-sized experimental test.

Every supersonic fan or compressor blade row has a streamtube, the 'sonic streamtube', which operates with a blade relative inlet Mach number of one. A key parameter in the design of the 'sonic streamtube' is the area ratio between the blade throat area and upstream passage area, Athroat/Ainlet. In this paper, it is shown that one unique value exists for this area ratio. If the area ratio differs, even slightly, from this unique value then the blade either chokes or has its suction surface boundary layer separated due to a strong shock. It is therefore surprising that in practice designers have relatively little problem designing blade sections with an inlet relative Mach number close to unity. This paper shows that this occurs due to a physical mechanism known as 'transonic relief'. If a designer makes a mistake, and designs a blade with a 'sonic streamtube' which has the wrong area ratio, then 'transonic relief', will self-adjust the spanwise streamtube height automatically moving it towards the unique optimal area ratio, correcting for the designer's error. Furthermore, as the blade incidence changes, the spanwise streamtube height self-adjusts, moving the area ratio towards its unique optimal value. Without 'transonic relief', supersonic and transonic fan and compressor design would be impossible. The paper develops a simple model which allows 'transonic relief' to be decoupled from other mechanisms, and to be systematically studied. The physical mechanism on which it is based is thus determined and its implications for blade design and manufacturing discussed.

Numerical analysis was carried out to investigate the influence of the setting angle and chord length on the pressure distribution especially for the shroud span of an axial fan. The setting angle was referred to as AOA (angle of attack). The aerodynamic performance of an axial fan with the change of setting angle and chord length was presented, and the unstable pressure distribution was discussed in detail. The airfoil of an axial fan was based on the NACA 3512. The influence of the setting angle was observed with the designed sets which were rotated based on the center of gravity for the blade. The chord length was adjusted while maintaining the setting angle. For each design parameter, 5 sets were designed to conduct the single-factor analysis, respectively. The setting angle had a sensitive effect on the aerodynamic performance of an axial fan. The pressure distribution became unstable related to the setting angle of the shroud span. On the other hand, the chord length was only proportional to the pressure rise and had a little effect on efficiency.

This paper deals with the prediction of the particle dynamic and erosion characteristics due to dust ingestion in an axial flow fan, installed in a high bypass-ratio turbofan engine that operates in a dusty environment. Dynamic behavior comprises the particle trajectory and its impact velocity and location. While the erosion characteristics are resembled by the impact frequency, erosion rate, erosion parameter and the penetration rate. The study was carried out in two flight regimes, namely, takeoff, where the sand particles are prevailing, and cruise, where the fly ashes are dominated. In both cases, the effect of the particle size on its trajectory, impact location, and the erosion characteristics was studied. To simulate the problem in a more realistic manner, a Rosin Rambler particle diameter distribution was assumed at takeoff and cruise conditions. At takeoff, this distribution varies from 50 to 300 µm with a mean diameter of 150 µm sand particles. While at cruise, this distribution varies from 5 to 30 µm with a mean diameter of 15 µm fly ash particles. The computational domain employed was a periodic sector through both the fan and its intake bounding an angle of (360/38) where the number of fan blades is (38). The intake is a stationary domain while the fan is a rotating one and the FLUENT solver is used to solve this problem. Firstly, the flow field was solved in the computational domain using the Navier-Stokes finite-volume supported by the Spalart-Allmaras turbulence model. The governing equations, representing the particle motion through the moving stream of a compressible flow are introduced herein to calculate the particle trajectory. The solution of these equations is carried out based on the Lagrangian approach. Next, empirical equations representing the particle impact characteristics with the walls are introduced to calculate the rebound velocity, the erosion rate, erosion parameter, impact frequency and penetration rate. Moreover, a method to smoothen the irregularity in the calculated scattered data was discussed as well. During takeoff flight regime, the pressure side of fan blade experienced higher particle impact and erosion damage. The highest erosion rate was found at the corner formed by blade tip and trailing edge of pressure side. During cruise conditions, less erosion rates resulted. Maximum erosion rates are found at the leading edge of the pressure side.

The Missouri University of Science and Technology’s (Missouri S&T) Experimental Mine is a teaching and research facility which has been excavated in limestone by mining engineering students over almost 100 years. The mine is currently being extended to a second level. Available fans for ventilation are two surface fans of 24 kW and two underground booster fans of 12 kW. The design of a ventilation network in conjunction with multi surface fans and booster fans entails a complex procedure. Ventsim Visual software modeling has been used for network analysis to determine the optimum surface and booster fans locations, blade settings, and speeds. Both natural and mechanical induced ventilation pressures have been taken into account. Three working faces on each level have been designated as target points that minimum air quantities are required. The model has been calibrated against a pressure and quantity survey. Design of ductwork, door/stopping positions and different fans characteristics have been examined. The optimum flow rate at identified working faces, efficiency and minimum energy losses and annual network power cost determine the best scenario. The optimum design has been determined for the ventilation network for the next 100 years. The optimum flow rate across working faces is the key criterion selected.

This dissertation treats the aerodynamic design of low-speed axial fans for industrial applications, considering dimensional and/or rotor-speed constraints as eventual additional design requirements.

In the last years, the complexity of the design task and the number of
related tools have increased exponentially in turbomachinery, with industrial axial-flow fans making no exception. Recent automated design softwares and optimization routines provide highly efficient fan designs. Regardless of the effectiveness of these computer-based methods however, the variables that mostly affect fan performance and efficiency are still related to the basic primary design choices, as the selection of the axial fan configuration, for instance.

In spite of a long history of axial fans, some basic questions on the aerodynamic design of these machines still do not have a clear and definitive answer in the technical literature. In particular, two major design issues have been identified:

a) the lack of quantitative indications that guide the designer into the selection of the axial fan configuration, among rotor-only, rotor-straightener, preswirler-rotor, and multistage machine;

b) the lack of quantitative information that guide the fan designer into the choice of the suitable span-wise aerodynamic loading distribution (i.e., the design vortex criterion) for the required operation in case of rotor-only axial fans.

According to these needs, a research has been conducted into several aspects of the aerodynamic design of low-speed axial fans. A data-base of fan performance and efficiencies has been collected to provide maps that can guide fan designers into the primary design choices reported at items a) and b). The construction of this data-base required the collection of fan data from the available literature and from a dedicated experimental campaign. Most of the fans that have been tested on two ISO 5801 inlet-chamber test rigs are specifically-designed rotor-only prototypes. Therefore, an effective aerodynamic design method has been developed for this widely used type of machine (i.e., for rotor-only axial fans). The method is based on the
information resulting from the fan data-base, as well as on a preliminary mean-line performance and efficiency estimation procedure. The local (i.e., the velocity field) and global (i.e., performance and efficiency) behavior of the resulting geometries have been verified by means of a CFD (Computational Fluid Dynamic) model, before the manufacturing of the prototypes.
CFD simulations are run on a simplified model that is particularly appropriate for the industrial requirements of rapidity and accuracy of results. All the necessary information to perform satisfactorily the aerodynamic design of a rotor-only fan are provided. Most of these indications can be directly extended to design also machines with fixed bladings.

The main results of the investigation are graphs that summarize axial fan performance around the well-known Cordier curve, identifying: i) suitable operating areas for each fan configuration, and ii) suitable vortex-criteria operating areas in case of rotor-only fans. Theoretical explanations are provided at support of the observed trends. Such information represent simple and quantitative aids to guide fan designers into the primary design choices.

In particular, the data show that vane-axial and contra-rotating fans operate at lower specific speeds and diameters with respect to rotor-only ones. Thus, a Cordier-line diagram specific for Rotor-only axial fans relies at higher specific diameters with respect to vane-axial machines. Whether the rotor-only configuration is the only one permitted (for instance due to dimensional constraints), Forced-vortex rotors (i.e., with aerodynamic loading distributions that increase towards the blade tip) represent a suitable solution for operations at low specific speeds, relatively large flow-rates and pressure rises. However, the fan efficiency of forced-vortex rotor-only fans is lower than that of rotor-straightener machines operating at the same pressure-rise, making the forced-vortex design solution appropriate in presence of constraints on both the fan axial length, the fan diameter and the rotor speed (for instance, the fans installed on air-conditioner external units).

The scope of the work is providing an aerodynamic design methodology for industrial axial fans. The information reported in this work can be useful for fan designers and manufacturers, as well as for anyone interested in the field of mechanical ventilation.

In this study, the local generated entropy and exergy destroyed in the axial transonic fan of a high bypass ratio tur-bofan engine (CF6) are investigated numerically and analytically. The flow field is solved in the fan and its intake using the Navier-Stokes finite volume technique. The case examined is at the flight condition (0.85 Mach number and 11000 meters altitude). The fan in concern is a highly twisted blade, large in diameter, and installed in the CF6-50 high bypass ratio turbofan engine. The flow field is considered compress-ible, turbulent, and three dimensional. The computational domain employed here is a periodic sector through both the fan and its intake bounding an angle of (360/38) where the number of fan blades is (38). The intake is a stationary domain while the fan is a rotating one. The flow field solution shows a captured normal shock wave propagating from the blade trailing edge of the suction surface crossing the passage towards the first third of the blade pressure side. Moreover, a subsonic bubble is formed at the leading edge and a wake region is formed at the trailing edge. The local entropy generated (thermal and viscous) is computed in terms of the velocity and temperature gradients. The regions of entropy production appear at the bound-* Corresponding author. aries as well as throughout some regions across the passage. A remarkable generation of entropy is found at the wake region near the trailing edge, at the supersonic bubble attached to the leading edge, and across the passage shock wave. The exergy destruction calculated computationally through the fan and the intake show a good agreement with that calculated analytically. The calculated Bejan number is found to be law (0.022). This indicates that the thermal entropy generation is of negligible contribution compared with the vis-cous one. It is also found that, under the cruise condition, the fan contributes by 1.95 MW of losses in useful work potential while this value for the intake is found to be neglected comparing with the fan (4.6 KW). Nomenclature C p Specific heat at constant pressure,[j/kg.k]. EX Exergy,[W]. h Specific enthalpy, [J/kg]. K Thermal conductivity, [W/m.k]. ˙ m Mass flow rate,[kg/m 3 ]. P Static pressure,[pa]. R Gas constant,[J/kg.k]. ˙ S Entropy generation rate,[W/k]. T Absolute temperature,[k]. V Velocity, [m/s]. ∀ Volume, [m 3 ]. µ Dynamic viscosity,[pa.s]. ρ Density,[kg/m 3 ]. 1 Introduction Entropy generation minimization, exergy analysis, and thermoeconomics are powerful tools in the design, and performance judgement of any energy system. Production of entropy is the key parameter in determining the maximum theoretical limits of energy efficiency of engineering devices. The most important issue is to identify the components of a system that are responsible for thermodynamic losses and try to minimize these losses and the associated costs of this system. Exergy, or availability, has been used for several years for the analysis of ground-based power producing systems and other many cogeneration systems. However, its application to the aerospace vehicles and other propulsion systems has to some extent been limited in the literature. Energy systems for modern aircrafts are important industrial sector that is an ideal candidate for the application of exergy analysis and thermodynamic optimization, Bejan and Siems [1]. According to the International Energy Agency, aviation oil consumption rises on average by 2.5% per year and it is projected to reach 454 Mtoe in 2030. This represents about 2.6% of the global energy consumption in 2030. Today there are more than 16800 commercial aircraft in operation. This number is expected to grow by 3.8% per year reaching more than 44 000 by year 2030, IEA [2]. Therefore , aircraft engines are very important study area for the exergetic assessments. Aircrafts are very complex systems that are composed of a large number of components which are exposed to changeable and unsteady environmental conditions. Different studies involving commercial aircraft systems have been developed to apply exergy analysis. One of these works related to exergy analysis for aircraft engines was done by Turgut et. al. [3]. They investigated the exergy destroyed for the components of a general electric turbofan engine (CF6-80) at sea level. According to the results it is found that the most exergy destructive unit in the propulsion system is the combustion chamber which contributed by about 35.76 MW of useful work lost. Moreover, the fan is the second high irreversible unit after the combustor which contributed by about 3.61 MW of exergy destruction. In another study, Turgut et, al. [4] performed an availability computations of a turbofan kerosene-fired engine with an afterburner at sea level and at an altitude of 11000 meters. Exergy destructions in each of the engine components are determined and the exergy efficiency values for both altitudes are calculated. The exergy destruction in the fan was found to be 2.52 MW (total engine is 198.68 MW) with an exergetic efficiency of 80.6% at sea level. This corresponds to 0.78 MW (total engine is 67.48 MW) and 86.9% at 11 km altitude respectively. The total ex-ergy efficiency of the engine was found to be 66.1% at sea level and 54.2% at 11 km altitude.

The Fin-fan is a very common machine used in different manufacturing units, factories and devices. An essential part of the heat exchanger, or air-cooled heat exchanger, the fanplays a crucial role in its functioning and has been in place for quite a long period of time. The heat exchanger or the cooling agent is used to remove heat from a process that generates it but does not know how to get rid of it. The heat exchanger transfers heat from one fluid to another and in order to transfer the heat, uses the fan to produce air that cools the liquid.

Impact Cooling Solutions has 27 years of experience in the energy efficient axial flow fan business and has supplied over 35,000 fans to 35 countries. ICS installed FRP fans are currently saving energy at the combined rate of over 125 MW all over the world.