Original Fan Research Articles

Research on Performance Optimization of Multi-Stage Centrifugal Fan

The optimization of fan performance under changed conditions has important significance for the practical application of the fan. In view of the low efficiency of the original fan, the stable working flow span of the flow pressure curve is narrow, and it is difficult to meet the performance requirement after the working point change. Without changing the radial and axial dimensions of the fan, the performance of the original fan is optimized so that it increases from the total pressure 16153pa to 17271pa when operating flow 1900m3/h, meets the optimized target of total pressure 17000pa, the performance increases by 6.9%, and makes the stable working range of its pressure curve widen.

Simulation and Optimization of Fan System for Road Sweeper

A QC/T51-2006 standard country five-series road-sweeping vehicle is used as research object to improve the mechanization and work efficiency of a road sweeper and reduce the degree of environmental pollution. This study examines the flow of the fluid in an air duct of the sweeper during the working process and identifies the limitations of the original fan structure design. The sweeping air duct and structure are of optimized design. In accordance with considerable analyses and research, fluid simulation of the original air duct was conducted using the finite element analysis software NX Nastran. A turbulence model is used to simulate the gas field inside the duct, ignoring the influence of temperature on the gas and wind pressure loss caused by a high-speed rotation of the fan. The entire duct was divided into two parts, namely, entrance and exhausted air ducts. In the model transfer process, the original assembly hole and welding plate were removed, and the unnecessary fillet and protruding structure were optimized. This approach was conducted to obtain the accurate value of wind speed in the suction port and outlet, which was compared with the starting velocity of dust particles and suspension speed. The flow field and streamline, velocity vector, and static pressure distribution of the original sweeper were obtained. Results show that through the data simulation analysis, the original sweater fan duct structure was optimized and its design was enhanced. This result increases the air duct speed by 50%. The fan power is reduced by 20 kW, thereby enhancing its efficiency. The energy saving is approximately 36.6%. The results provide data support and theoretical basis for the optimal design of the duct and structure. Furthermore, the results present theoretical and methodological support for the development of a new road sweeper.

Volute characteristics of centrifugal fan based on dynamic moment correction method

The multi-blade centrifugal fan features an abundance of vanes (>48) and a spiral volute. The flowability and noise characteristics of the centrifugal fan are dependent on the type-line of volute and tongue geometries at the volute exit. The aim of this research was to find a better volute type-line for fan noise reduction without compromising on the performance. First, the viscosity factors of gas were used to modify the type-line shape of the volute by introducing a dynamic moment correction coefficient; a modified volute was then obtained to match the new fan system. Next, the performance of the original fan and retrofit fan were tested. The optimization scheme was verified and the feasibility of the proposed numerical calculation technique was confirmed.

Remains of the 19th Century: Deep storage of contaminated hydraulic mining sediment along the Lower Yuba River, California

Since the onset of hydraulic gold mining in California’s Sierra Nevada foothills in 1852, the environmental damage caused by displacement and storage of hydraulic mining sediment (HMS) has been a significant ecological problem downstream. Large volumes of mercury-laden HMS from the Yuba River watershed were deposited within the river corridor, creating the anthropogenic Yuba Fan. However, there are outstanding uncertainties about how much HMS is still contained within this fan. To quantify the deep storage of HMS in the Yuba Fan, we analyzed mercury concentrations of sediment samples collected from borings and outcrops at multiple depths. The mercury concentrations served as chemostratigraphic markers to identify the contacts between the HMS and underlying pre-mining deposits. The HMS had mercury concentrations at least ten-fold higher than pre-mining deposits. Analysis of the lower Yuba Fan’s volume suggests that approximately 8.1 × 107 m3 of HMS was deposited within the study area between 1852 and 1999, representing ~32% of the original Yuba Fan delivered by 19th Century hydraulic gold mining. Our estimate of the mercury mass contained within this region is 6.7 × 103 kg, which is several orders of magnitude smaller than what was estimated to have been lost to the mining process. We suggest that this discrepancy is likely due to a combination of missing (yet to be found) mercury masses stored upstream, overestimated losses during mining, and high delivery of mercury to the lowland Sacramento Valley and to the San Francisco Bay-Delta system, where it poses a great risk to sensitive ecosystems.

Design of volute shape of centrifugal fans

This work addresses the issues of decreased efficiency and static pressures of a centrifugal fan under variable working conditions (VWCs). A design method for the volute radius with flow-correcting coefficients and an area factor was proposed. The model of the design method was solved using genetic algorithms in MATLAB. The volute was designed for two cases: with area constraints and without area constraints. Computational fluid dynamics was used in the numerical simulations of the original fan and the two others with modified volute under VWCs, and corresponding performance curves were obtained. The internal flow fields of the three types of fan volutes were analysed for the cases under 40%, 100%, and 130% loads. The results indicate that the efficiency and static pressure of the two designed fans were improved under VWCs. The backwash at the outlet tongue, volute outlet static pressure fluctuation, and the swirl effects inside the volute were all reduced. The volute fan with area constraints exhibited the best performance under VWCs.

Determination of relative positions and phase angle of dual piezoelectric fans for maximum heat dissipation of fin surface

A three-dimensional computational model for dual piezoelectric fans on the bounded plane has been built using the commercial code CFD-ACE+, and the Levenberg–Marquardt Method (LMM) was used to estimate the optimal relative positions and phase angle of fans for minimizing the average temperature of the fin surface. The dual piezoelectric fans are originally placed in seven different positions (cases 1–7), and the LMM is then utilized to estimate the optimal relative positions and phase angle for increasing the thermal performance of dual piezoelectric fans. The simulations of numerical computations show that for each of the seven original fan arrangements, the optimal relative positions and phase angle of the dual fan are achieved using a singular arrangement in which both fans are located 0.95mm below the center line of the fin and the in-phase operational condition is used. Finally, the temperature distributions of the fin for the original designs of cases 1 and 2 and for the optimal design of case 1 are measured using a thermal camera and are compared with the numerical solutions. The results indicate that the relative errors between numerical and experimental average fin temperatures at 600s for original case 1, original case 2 and optimal case 1 are 0.68%, 0.52% and 0.68%, respectively, thereby validating the estimation method used herein to determine the optimal relative positions and phase angle of dual piezoelectric fans.

An optimal volute spiral case design for centrifugal fan: theoretical and experimental studies

An inverse design problem in determining the optimal shape of volute spiral case for a centrifugal-flow fan is examined in the present study using the Levenberg–Marquardt method and a general purpose commercial code CFD-ACE+, and based on a desired airflow rate. The desired volume airflow rate can be obtained by multiplying the airflow rate of an existing fan by a constant number which is >1. The shape of the redesigned volute case is generated using the equation of the trajectory of fluid particles in the volute, which enables the shape of the fan volute be constructed completely. Finally, prototypes of the original and optimized fan volutes as well as fan impellers are fabricated, thereafter the fan performance is tested based on the AMCA-210-85 standard to verify the validity of the design. The experimental results demonstrate that by utilizing the fabricated centrifugal optimal fan and operating at the design condition, the airflow rate can be increased by 6.5 % and the pressure drop, noise and input power of fan can be reduced by 1.6, 5.3 and 11.4 %, respectively, when compared with the original fan. As a result, the performance of optimal fan can be improved greatly.

Investigation of Double Grooved Blade Tip Structure on Aerodynamic Performance and Vibration Characteristic of an Axial Flow Fan

Adopting double grooved blade tip structure is one of the measures to improve the impeller performance by blocking the tip clearance leakage flow effectively. Basing on a variable pitch axial flow fan of OB-84 type, the performance of the fan with original blade tip and three double grooved blade tips with different groove depth are simulated by using numerical software FLUENT. Both the leakage flow field and loss distribution in and near the tip clearance are discussed. The vibration characteristics of original blade and double grooved blade tips are also checked with ANSYS finite element dynamic analysis module. The results reveal that double-grooved blade tip structure improves the distribution of leakage flow which hinders the development of leakage flow and thus impairs the mixing of the leakage flow and passage flow. The performance of the fan with double grooved blade tips varies significantly with a decrease in total pressure and an increase of efficiency to some extent under the designed operating condition. The impact of groove depth on fan performance is prominent in the vicinity of design flow rate while little influence in large flow rate. The double groove blade tip with a depth of 3mm obtains the optimal performance with an improvement of efficiency by 1.05 percent greater than the original fan at design condition and an improvement of surge margin. The characteristics of blade vibration show that each order natural frequency of double grooved blade is increased compared with the original blade and is out of step with the blade passing frequency, so the resonance will not occur by adopting double grooved blade tip.

Simulation of air jets for controlling stall in a centrifugal fan

The main goal of the present work is to analyze the three-dimensional unsteady flow field of a centrifugal fan by solving Navier–Stokes equations, coupled with the throttle condition. The results show that rotating stall occurs in the original fan when the flow rate is 4.30 m3/s, and the stall inception first appears at three impeller passages near the volute tongue and front disc. An active control method is proposed to inhibit the stall inception, which involves blowing air at the inlets of the three impeller passages. This blowing control method cannot inhibit the stall inception when the blowing speed is lower than 50 m/s. The stability margin of the centrifugal fan is extended when the blowing speed is increased from 50 to 110 m/s, while no further effect is obvious with a further increase in the blowing speed. At a blowing speed of 110 m/s, rotating stall occurs again when the fan flow reaches 3.46 m3/s. After the application of the nozzle blowing, the safety margin of the centrifugal fan is extended by 13%, and an obvious stability enhancement effect is achieved. From an engineering standpoint, this new active control method for rotating stall offers a valuable means to ensure the safe operation of a centrifugal fan.

The Effect of an Eroded Leading Edge on the Aerodynamic Performance of a Transonic Fan Blade Cascade

Especially at transonic flow conditions the leading edge shape influences the performance of a fan profile. At the same time the leading edge of a fan profile is highly affected by erosion during operation. This erosion leads to a deformation of the leading edge shape and a reduction of the chord length. In the present experimental and numerical study, the aerodynamic performance of an original fan profile geometry is compared to an eroded fan profile with a blunt leading edge (BLE) and a chord length reduced by about 1%. The experiments are performed at a linear fan blade cascade in the Transonic Cascade Wind Tunnel of DLR in Cologne. The inflow Mach number during the tests is 1.25 and the Reynolds number 1.5 × 106. All tests are carried out at a low inflow turbulence level of 0.8%. The results of the investigation show that losses are increased over the whole operating range of the cascade. At the aerodynamic design point (ADP) the losses raise by 25%. This significant loss increase can be traced back to the increase of the shock losses at the leading edge. The change in shock structure is investigated and described in detail by means of particle image velocimetry (PIV) measurements and Schlieren imaging. Additionally, the unsteady fluctuation of the shock position is measured by a high-speed shadowgraphy. Then the frequency range of the fluctuation is obtained by a Fourier analysis of the time resolved shock position. Furthermore, liquid crystal measurements are performed in order to analyze the influence of the leading edge shape on the development of the suction side boundary layer. The results show that for the original fan blade the transition occurs at the shock position on the blade suction side by a separation bubble whereas the transition onset is shifted upstream for the fan blade with the BLE.

Optimization Design of the Spinning Multistage Centrifugal

This paper analyses the structure of the original spinning multistage centrifugal fan. Because of low pressure and low efficiency, optimization design was carried out for the original fan. Based on the aerodynamic calculations theory, the structure and pneumatic of single stage was studied. The influence factors are Inlet-flow loss, equivalent divergent angle, pre-swirl, Resonant frequency etc. Pneumatic recalculation and experiment are carried out for the multistage fan. Results show that after modification pressure of the multistage fan has increased raises 15.3 %.

Investigation acoustic effect of the convexity-preserving axial flow fan based on Bezier function

The axial flow fan is the major component of air-conditioning outside units, and the noise reduction has always been the main object of the fan researches in the past decades. Many previous researches have concentrated on the noise reduction of the axial flow fan by changing the tip clearance and blade shape of the trailing edge (TE). In this article, a local convexity-preserving structure at leading edge (LE) has been proposed, which is implemented through retrofit design of the original fan blade based on Bezier function method. The effect on the aerodynamic noise of the convexity-preserving of the improved fan B is investigated. To this purpose, the unsteady flow field in the fan is predicted by solving the incompressible Reynolds-averaged Navier–Stokes (RANS) equations with the SST-SAS turbulence model. The result shows that the convexity-preserving structure is beneficial for the noise reduction without decreasing the axial fan performance. Moreover, the noise frequency spectrograms in the far field and sound pressure of 1/3 octave are given by experiment. The noise-reduction effect of improved fan B is verified by comparing the sound pressure lever (SPL) at different frequency bands.

Preliminary evaluation of guava selections for guava wilt disease resistance in South Africa

Guava wilt disease (GWD), caused by Nalanthamala psidii, is a serious disease occurring in the guava-producing areas of the Mpumalanga and Limpopo provinces of South Africa. Two resistant guava rootstocks, TS-G1 and ‘TS-G2’, were developed by the ARC-ITSC in 1995. In 2009, a renewed outbreak of GWD was reported, which also affected the resistant ‘TS-G2’ cultivar, placing the guava industry under threat again. The aim of this study was to seek resistant guava selections by means of in vitro screening of guava seedlings and subsequently testing the most promising selections in inoculation studies with N. psidii. A culture filtrate of N. psidii was used to screen guava seedlings in vitro. Promising selections were multiplied in tissue culture, hardened-off and planted in bags before inoculation with the GWD fungus in a shadehouse trial. The number of plants surviving nine months after inoculation was recorded. Although none of the selections showed complete resistance, selection MS44 showed some tolerance against the G2 isolate of the pathogen obtained from diseased ‘TS-G2’ trees, whilst selection MS70 showed some tolerance against the G1 isolate obtained from diseased TS-G1 trees. These selections were also resistant to the original Fan Retief isolate of the pathogen.

OPTIMIZATION OF LOW NOISE BIONIC FAN USING GRAY RELATIONAL ANALYSIS COUPLED WITH ENTROPY MEASUREMENT

This research presents a hybrid optimization method for the determination of the optimal geometry parameters which can minimize the A-weighted sound pressure level of bionic fan on condition that the mass flow rate of the bionic fan is as high as possible. A hybrid approach of gray relational analysis (GRA), Taguchi method, and entropy measurement has been used to obtain better acoustic performances with three basic geometry parameters, which are blade number, boss ratio, and blade stagger angle. A L9(34) orthogonal array has been used for conducting the experiment for optimization of flow and acoustic performances. The problem of multiple performance indices is simplified into single performance index by using gray relational grade. The designed experimental results are utilized in GRA, and the weights of the flow and acoustic performances are determined by using the entropy measurement method. Meanwhile, the optimal combination of bionic fan parameters is determined by using GRA method. Moreover, the validation tests show that the overall sound pressure level (SPL) reduces by 15.50% at the cost of mass flow rate reducing by 3.00%. The comparison of the A-weighted SPL for acoustic tests between original fan and optimized bionic fan demonstrates that the acoustic performance obviously improve from 20 Hz to 6300 Hz. Therefore, it is clearly shown that the proposed approach in this paper can be an useful tool to improve acoustic performance of bionic fan.

Performance Enhancement of the In-Line Fan Equipped with the Guiding Vane and the Tail Body

This integrated numerical and experimental study intends to enhance the performance of an in-line fan with the implement of the guiding vane and the tail body. At first the flow flied associated with the original in-line fan is simulated and analyzed within the framework of CFD code Fluent, in which the finite volume method is applied. Next, the guiding vane is constructed based on the calculated flow characteristics, and attached in the downstream of rotor to smoothen the flow pattern. An appropriate guiding vane with high-performance and low-noise features can be achieved after several design iterations. In addition, the tail body connected to the motor is introduced for further enhancing the fan performance by reducing the sizes of wake and reversed flow behind the hub. Thereafter, to manufacture the mockup for experimental verification, the modified fan with guiding vane is plotted in the CAD/CAM format for mockup fabrication via the rapid-prototype technique. Moreover, a set of relations correlating the performance and noise of this fan prototype are executed inside AMCA test chamber and semianechoic chamber, respectively. Consequently, the feasibility of design scheme and numerical system can be verified according to these experimental results. In summary, this work provides a systematic scheme for designing and analyzing the in-line fan.

Mediation of fandom in Karin Giphart's "Maak me blij"

The plot of the Dutch novel Maak me blij (Make me happy) (2005) by Karin Giphart draws from the culture of online fan communities. It describes the life of a lesbian in her late 20s, Ziggy, who has a terminally ill mother. Ziggy is an active fan who writes and reads femmeslash fan fiction—that is, lesbian interpretations of characters from mainstream series such as Star Trek: Voyager (1995–2001). By providing through Ziggy a personal view of fan communities and the genres that flourish there, Maak me blij connects the romantic motives of original lesbian fiction with its underground sister, fan fiction. The novel draws from various source texts and illustrates how fans interpret texts within a wider literary landscape. I use the concept of intermediality to analyze how Maak me blij mediates different types of original fiction (lesbian romances, science fiction) and fan fiction (femmeslash, Star Trek fan fiction) to establish new views on fandom and its construction of gender and intimacy. These motives are not only apparent within the text itself but also within the character of Ziggy as a fan writer with her own original alien characters.

An inverse problem in determining the optimal position for piezoelectric fan with experimental verification

The objective of this work is to utilize the commercial package CFD-ACE+ to build a three-dimensional computational model for piezoelectric fans, then apply the technique of Levenberg–Marquardt Method (LMM) to estimate the optimal location of the piezoelectric fan to minimize the maximum fin temperature. The piezoelectric fan is originally placed in four different positions, namely, cases A, B, C and D, respectively; the LMM is then utilized to estimate the optimal location of the piezoelectric fan to increase its thermal performance. The simulations of numerical experiments show that for all of these four different original fan positions, the optimal fan position occurs at one position, at about 3.5mm below the center point of the fin. Finally, temperature distributions of the fin with the original and optimal fan positions are measured using a thermal camera and are compared with the numerical solutions to justify the validity of the present estimation of the optimal fan position problem.

SU-F-BRCD-01: A Novel Dual Source Array Tetrahedron Beam Computed Tomography (TBCT) System for Image Guided Radiotherapy.

To design and test the feasibility of a novel dual source array, dual detector array TBCT system which is capable of both volumetric CT imaging as well as real-time stereoscopic x-ray imaging for image guided radiotherapy (IGRT). Besides producing improved image quality, the geometry of TBCT is also more compact and flexible. It is possible to mount two x-ray source arrays and two detector arrays on a LINAC gantry. Each pair of source/detector arrays generates real-time fluoroscopy images at four different view angles, which can be used in real-time target/marker tracking. FDK and iterative CT image reconstruction algorithms were developed for this new geometry. Stereoscopic imaging was simulated using CT images of prostate patients with implanted radiopaque markers. Although the cone angles to the central slice of the reconstructed image are nonzero due to the shifting of the detector arrays, reconstructed patient CT images are visually identical to the original fan beam images. Anatomical structures and implanted radiopaque markers are visible in at least two of the radiography images. The 3-D spatial coordinates of the implanted markers can be determined from the stereoscopic images. TBCT with dual source and dual detector arrays can produce high quality CT images as well as real-time stereoscopic imaging for target tracking. High quality online CT images and stereoscopic imaging in MV beam-eye-view direction can be very useful for advanced treatment techniques. Tiezhi Zhang and Joshua Kim have financial interest in TetraImaging Inc.

A Review on Performance of Industrial Induced Draft Centrifugal Fan Using Ansys Cfx

Fans are one of the types of turbo machinery which are used to move air continuously with slight increase in static pressure. Fans are widely used in industrial and commercial applications from shop ventilation to material handling, boiler applications, transporting gas or materials and most use in the HVAC industry today. In this paper it describes the different techniques which may help to increase the pressure of air. Flow in centrifugal impeller is simulated by Navier-stokes eq. and performance curved is obtained. The experimental data has been collected from Industry. Now the parameter considered is number of blade, inlet and outlet angle, diameter ratio Performance analysis has been carried out by experimental and ANSYS CFX software. It observed that number of blade increase, so that reduce in flow passage and more enlarged flow developed. Finally, the result of this total pressure and efficiency increase compared with original centrifugal fan.

Study of Tonal Fan Noise Reduction by Modification of the Volute Cutoff

Blade-passing frequency (BPF) tonal noise is usually the main contributor to centrifugal fan noise as opposed to broad-band noise; therefore, abating its strength can reduce fan noise significantly. The predominant BPF noise source is the surface acoustic dipole over the cutoff due to the flow interactions between the impeller and the volute. In this study, a modified cutoff with an inclined edge and enlarged cutoff clearance was successfully employed to reduce the BPF noise; the measured noise spectra at three different flow rates of the inclined-cutoff fan and the original fan were compared, and noticeable noise reduction was found. The cause of this tonal noise reduction was numerically studied, using computational fluid dynamics (CFD) technology and acoustic analogy theory to calculate the flow fields inside the fan and sound radiation respectively. Results showed that the cutoff, including the geometric configuration and it's clearance with the impeller, was crucial to impeller-volute flow interactions. As a consequence, this inclined cutoff with enlarged cutoff clearance could eliminate the BPF pressure fluctuation, i.e. BPF dipole source, at the design point effectively; although the BPF pressure fluctuation was still notable at large flow rates, the radiated sound power decreased drastically attributed to the phase cancellation of the dipole sources. This study shows that CFD combined with acoustic analogy can provide a reliable access to noise prediction, thus it will be employed in aeroacoustic optimization of centrifugal fans.