Characteristics Of Fan Research Articles

Numeryczna analiza charakterystyk wentylatora osiowego

The paper presents an analysis and comparison of basic characteristics of axial fans, both analytically and numerically. Such characteristics are: the characteristics of the total pressure, power and total efficiency as a function of the volumetric flow rate. The presented results showed significant quantitative and qualitative differences in the characteristics obtained by two methods. The usefulness of numerical methods in relation to the results of the initial analytical project was confirmed.

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.

Sedimentary characteristics of turbidite fan and its implication for hydrocarbon exploration in Lower Congo Basin

The turbidite is favorable for accumulation of oil and gas and it is the most important reservoir in the deepwater area of West Africa. Currently, some commercial discoveries in such the deepwater area generally belong to turbidite sandstone reservoirs. Based on comprehensive analysis of lithology, lithofacies and configuration of the turbidite, and combined with changes of seismic attributes and sedimentary cycle, the turbidite in the deepwater area of West Africa can be classified into by-pass channel (including the constructive by-pass channel and the erosive by-pass channel), confined channel complex, weakly confined channel complex, and lobe. Different types of turbidite reservoirs have different physical property, so there are differences in hydrocarbon exploration potential; the sandstone in the weakly confined channel complex is the key exploration target in the deepwater area of the Angola Sea.

Flow and Vibration Characteristics of Axial-flow Fan with a Blockage Disk

Flow and Vibration Characteristics of Axial-flow Fan with a Blockage Disk

Numerical Study on the Acoustic Characteristics of an Axial Fan under Rotating Stall Condition

Axial fan is an important piece of equipment in the thermal power plant that provides enough air for combustion of coal. This paper focuses on the aerodynamic noise characteristics of an axial fan in the development from stall inception to stall cells. The aerodynamic noise characteristic of monitoring region in time and frequency domains was simulated employing the large-eddy simulation (LES), with the addition of throttle setting and the Ffowcs Williams-Hawkings (FW-H) noise model. The numerical results show that, under the design condition, the acoustic pressure presents regular periodicity along with the time. The noise energy is concentrated with high energy of the fundamental frequency and high order harmonics. During the stall inception stage, the acoustic pressure amplitude starts fluctuating and discrete frequencies are increased significantly in the low frequency; among them, there are three obvious discrete frequencies: 27.66 Hz, 46.10 Hz and 64.55 Hz. On the rotating stall condition, the fluctuation of the acoustic pressure level and amplitude are more serious than that mentioned above. During the whole evolution process, the acoustic pressure peak is difficult to keep stable all the time, and a sudden increase of the peak value at the 34.5th revolution corresponds to the relative velocity’s first sudden increase at the time when the valve coefficient is 0.780.

Numerical and Experimental Research on Aerodynamic Noise Characteristics of a Multi-Blade Centrifugal Fan

The aerodynamic noise characteristic of a multi-blade centrifugal fan was studied by using numerical analysis and experimental test methods respectively. The unsteady flow dynamics analysis method and aeroacoustics based on finite element method were used to predict the spectral characteristics of noise of the fan. And then the spectral characteristic of noise of the centrifugal fan was measured in a semianechoic room. A good match was obtained respectively by using the numerical analysis and the experimental test. Based on this work, for now, the numerical analysis method of aerodynamic noise can be used to judge qualitatively the noise level of multi-blade centrifugal fans by adjusting the unsteady flow analysis model.

Effect of inlet guide vanes on the performance of small axial flow fan

Effects of the inlet guide vanes on the static characteristics, aerodynamic noise and internal flow characteristics of a small axial flow fan are studied in this work. The inlet guide vanes with different outlet angle are designed, which are mounted on the casing and located at the upstream of the impeller of the prototype fan. Both steady and unsteady flow simulations are performed. The steady flow is simulated by the calculations of Navier-Stokes equations coupled with RNG k-epsilon turbulence model, while the unsteady flow is computed with large eddy simulation. According to the theoretical analysis, the inlet guide vanes with outlet angle of 60° are regarded as the optimal inlet guide vanes. The static characteristic experiment is carried out in a standard test rig and the aerodynamic noise is tested in a semi-anechoic room. Then, performances of the fan with optimal inlet guide vanes are compared with those of the prototype fan. The results show that there is reasonable agreement between the simulation results and the experimental data. It is found that the static characteristics of small axial flow fan is improved obviously after installing the optimal inlet guide vanes. Meanwhile, the optimal inlet guide vanes have effect on reducing noise at the near field, but have little effect on the noise at the far field.

Calculation of sound power level of tandem axial fan

A numerical simulation of the flow in axial fans with single and tandem geometrically equivalent blade rows was carried out. During the research, the sound power level of the fans was calculated. The acoustic characteristics of the single fan obtained in the numerical experiment were compared with the results of the physical experiment. The divergence between the results of the physical and numerical experiments on the sound power level for the first harmonic is 0.08 %, for the second harmonic – 0.35 %. In order to reduce the acoustic emission, a 3D model of the axial fan with the geometrically equivalent tandem row was constructed. The results showed that at the fan rotation frequency of 900 rpm, the sound power level on the first two harmonics is reduced by more than 7 dB. Also, the change in the total sound power level for axial single and tandem fans in the rotation frequency range of 900 to 1,500 rpm was investigated. The fan with the geometrically equivalent tandem blade row has the total sound power level by 6.9...7.4 dB lower than the single fan. The use of the tandem axial fan allows improving acoustic characteristics

Source‐to‐sink analysis in an active extensional setting: Holocene erosion and deposition in the Sperchios rift, central Greece

AbstractWe present a source‐to‐sink analysis to explain sediment supply variations and depositional patterns over the Holocene within an active rift setting. We integrate a range of modelling approaches and data types with field observations from the Sperchios rift basin, Central Greece that allow us to analyse and quantify (1) the size and characteristics of sediment source areas, (2) the dynamics of the sediment routing system from upstream fluvial processes to downstream deposition at the coastline, and (3) the depositional architecture and volumes of the Holocene basin fill. We demonstrate that the Sperchios rift comprises a ‘closed’ system over the Holocene and that erosional and depositional volumes are thus balanced. Furthermore, we evaluate key controls in the development of this source‐to‐sink system, including the role of pre‐existing topography, bedrock erodibility and lateral variations in the rate of tectonic uplift/subsidence. We show that tectonic subsidence alone can explain the observed grain size fining along the rift axis resulting in the downstream transition from a braided channel to an extensive meander belt (>15 km long) that feeds the fine‐grained Sperchios delta. Additionally, we quantify the ratios of sediment storage to bypass for the two main footwall‐sourced alluvial fan systems and relate the fan characteristics to the pattern and rates of fault slip. Finally, we show that ≥40% of the sediment that builds the Sperchios delta is supplied by ≤22% of the entire source area and that this can be primarily attributed to a longer‐term (~106 years) transient landscape response to fault segment linkage. Our multidisciplinary approach allows us to quantify the relative importance of multiple factors that control a complex source‐to‐sink system and thus improve our understanding of landscape evolution and stratigraphic development in active extensional tectonic settings.

Experimental study of a ducted contra-rotating lift fan for vertical/short takeoff and landing unmanned aerial vehicle application

This study explores the aerodynamic characteristics of a ducted contra-rotating lift fan for vertical/short takeoff and landing application by means of force, pressure, and flow field measurements. The effect of rotating frequency and contra-locomotion on the force generation was examined using a miniature six-component force sensor. Additionally, for the sake of considering the ground effect, the flow field at the exit was investigated using high-response pressure measurement. Results revealed that the lift shows a quadratic generation trend on increasing the r/min where the inherent unsteady flow contradicts the conventional quasi-steady model of propeller. The contra-rotating mechanism can significantly augment the lift while still being lower than double single rotors. The unsteadiness of the contra-rotating rotors is quite obvious where two high-pressure regions are revealed and rotate. When the lift fan approaches the ground, the lift will be augmented significantly due to the surplus of the wake jet.

Study of unsteady flow simulation of backward impeller with non-uniform casing

The flow characteristics of the centrifugal fans with different blade outlet angles are basically discussed on steady and unsteady simulations for a rectangular casing fan. The blade outlet angles of the impellers are 35° and 25° respectively. The unsteady flow behavior in the passage of the impeller 35° is quite different from that in the steady flow behavior. The large flow separation occurs in the steady flow field and unsteady flow field of the impeller 35°, the flow distribution in the circumferential direction varies remarkably and the flow separation on the blade occurs only at the back region of the fan; but the steady flow behavior in the impeller 25° is almost consistent with the unsteady flow behavior, the flow distribution of the circumferential direction doesn’t vary much and the flow separation on the blade hardly occurs. When the circumferential variation of the flow in the impeller is large, the steady flow simulation is not coincident to the unsteady flow simulation.

Γεωμορφολογικά και μορφοτεκτονικά χαρακτηριστικά των αλλουβιακών ριπιδίων του βόρειου τμήματος της λεκάνης του Αγγίτη ποταμού

The catchment area of Aggitis River, which forms a part of the wider catchment area of the Strymon River, constitutes a tectonic graben. In the north of the graben, landforms of complex alluvial fans (bajadas) are found. In the present study, the impact of tectonics on the deposition process and on the geomorphological relief of the northern basin of Aggitis. For this purpose, a quantitative analysis of morphological characteristics of the alluvial fans is carried out. Moreover, the geologic and stratigraphic characteristics of the fans were studied and components of the tectonic movements that took place in the study area identified. Through the geomorphological survey an uplift of 24m with a twisting towards the northeast for the Menikio Mountain was determined that took place in the Upper Pleistocene. While, for the Falakro Mountain, an uplift movement and a minimum torsion of approximately 9m towards the S – SE was calculated. The mountains at the East and at the West of Aggitis River were uplifted with different rates. This result is in agreement with the argument for the existence of a tectonic system of horsts and grabens that formed the Aggitis River basin and influenced its later development.

Fan characteristics of the self-support components of rotor ends and its performance matching

In order to perform a comprehensive study on the ventilation characteristics of an induction motor rotor end’s self-support components, and specify the relationship among its size, structure, motor loss and cooling performance, in this paper a 3D physical model of the rotor, stator and motor shell was established according to the characteristics of the total enclosed fan-cooled (TEFC) induction motor. Then the fluid field and temperature field of the TEFC induction motor was solved by combining finite volume method (FVM) and the basic principles of electric machine. By taking the rotor air friction loss and stator end windings temperature rise into consideration and comparing various solutions, the optimum solution to the length of the self-support components was determined, which provided a reference for the optimization of the motor rotor physical construction.

Influence of tip end-plate on noise of small axial fan

In this work, tip end-plate is used to improve the noise performance of small axial fans. Both numerical simulations and experimental methods were adopted to study the fluid flow and noise level of axial fans. Four modified models and the prototype are simulated. Influences of tip end-plate on static characteristics, internal flow field and noise of small axial fans are analyzed. The results show that on basis of the prototype, the model with the tip end-plate of 2 mm width and changed length achieved best noise performance. The overall sound pressure level of the model with the tip end-plate of 2 mm width and changed length is 2.4 dB less than that of the prototype at the monitoring point in specified far field. It is found that the mechanism of noise reduction is due to the decrease of vorticity variation on the surface of blades caused by the tip end-plate. Compared with the prototype, the static pressure of the model with the tip end-plate of 2 mm width and changed length at design flow rate decreases by 2 Pa and the efficiency decreases by 0.8%. It is concluded that the method of adding tip end-plate to impeller blades has a positive influence on reducing noise, but it may diminish the static characteristics of small axial fan to some extent.

Combination of the optical analyzer technique and multiply photon doppler velocimetry to measure the sound velocities in shock-compressed metals

It is proposed to combine the optical analyzer technique (OAT) and multiply photon Doppler velocimetry (MPDV) in every explosive experiment in order to overcome the reported discrepancies in the sound velocities measured in shock-compressed metals using different techniques. Such a combination is demonstrated to be efficient in explosive experiments with stepped samples of 12Kh18N10Т austenitic stainless steel and high-purity Mg95 magnesium under their shock-wave loading in ranges of 60–120 and 20–30 GPa, respectively. The OAT ensures classical recording of the longitudinal and bulk sound velocities. Depending on the loading intensity, the MPDV technique recorded temporal changes in the velocity of the “sample–indicator” interface or temporal changes in the shock-front velocity in the indicator. These data were used to monitor the parameters of the shock-compressed sample and to determine the instant when the first characteristic of the rarefaction-wave fan overtakes the shock-wave front in the indicator. Within the range of relatively low loads where the indicating fluid remains transparent and acts as a window material, the MPDV registers temporal variations in the velocity of the “sample–indicator material” interface. The OAT ensures reliable registration in the range of high-intensity loads, while the MPDV ensures time-resolved registration of the steady-shock-wave front velocity in the indicator up to the instant of its overtaking by a rarefaction wave. Both techniques are observed to work well in the intermediate range of loads. Combining these techniques enhanced the reliability of the obtained consistent data on the sound velocities in shock-compressed structural materials and also allowed a decreased number of explosive experiments with samples of toxic materials.

APPLICATION OF INFORMATION TECHNOLOGY FOR PROMOTION AND SUSTAINABLE MANAGEMENT IN MARINE ECOTOURISM: A CASE STUDY IN BANGSRING, BANYUWANGI

Ecotourism is a form of tourism management by promoting the unique tourist attraction such as natural destination, conservation, education and local wisdom. Banyuwangi is a region that makes ecotourism as a n important pillar of the economy in coastal areas. Communities in the coastal village of Bangsring District , Banyuwangi, generally have a chance to earn more revenue from ecotourism sector. The existence of coral reefs and beautiful island s are natural potential that can be developed into high-value marine ecotourism, especially with the increase in ecotourism trend. It is also in line with the direction of Government policy in Banyuwangi to advance marine ecotourism sector. Based on information obtained from the chairman of Pokwasmas Samudera Bhakti and KNIH Bangsring, the problem faced by partners related to the development of ecotourism was that Bangsring ecotourism requires more promotion s. I nformation about ecotourism so far has not fully use information technology, whereas characteristics of ecotourism fans who belong to a niche market requires their websites and other social media as an effective media campaign. Bunder (Underwater Bangsring) is one of the marketing strategies and promotion of village tourism potential in Bangsring using mobile application based on android. By using information technology (IT) , “Bunder” is able to generate information s based on android platform that can be accesed from anywhere and by everyone. A downloadable app lication named Bunder is regarding the potential of tourism and natural resources in Bangsring and its surrounding. This application is expected to support effective promotion towards sustainable management of marine ecotourism in Bangsring, Banyuwangi.

The influence of booster design features on aicraft engine fan tonal noise

Fan and booster tonal noise makes significant contribution to the overall noise level of an aero engine, particularly in subsonic modes of operation. This noise is caused by the interaction not only of the fan rotor and stator, but also by the interaction of elements of the fan and booster. Tonal components at these frequencies are caused by nonlinear interaction of rotating and stationary blade rows. Therefore, fan noise spectra contain not only common fan tonal components at the blade passing frequency and its harmonics, but sum and difference tones of interaction between the fan and booster elements. In testing acoustic characteristics of a bypass wide-chord fan it was revealed that the sum and difference components of the fan and booster interaction noise appeared in subsonic operating modes and propagated basically in the forward hemisphere. Labyrinth seal is one of the features of the actual fan design. These seals are opened and let some airflow pass in low operating modes of the fan. As a result the flow pattern upstream the fan rotor is distorted. It was experimentally determined that the seal significantly affects the generation of the fan tonal noise in subsonic modes. So far, the impact of this fan design feature is not taken into account in fan noise prediction methods. However, we experimentally determined strong influence of labyrinth seals on the noise of the aero engine simulator. Experimental assessment of the influence of the labyrinth seal operating in off-design modes on UPS noise spectra is the purpose of this work.

A Study on the Ventilation Efficiency Improved by Airflow Characteristics of the Axial Fan Installed in Parallel at the Side Wall of the Narrow Exhaust Tower

A numerical study has been conducted to simulate airflow and ventilation characteristics in the exhaust tower installed to ventilation of the multi-story underground parking lot. It is the objective of the present study to identify ventilation problems and to suggest the flow direction modifications of the ventilation system with the axial fan to improve ventilation efficiency in the low-rise section of the exhaust tower. Numerical results on SVE4 (scale of ventilation efficiency NO.4) and local mean age of exhaust ports are presented along with the location of axial fan on the direction of swirl flow and the dimension of exhaust tower. Ventilation system modifications on the direction of swirl flow have been suggested from the numerical results in order to prevent the flow interference by airflow discharged from the adjacent stories. The overall ventilation efficiency according to the rotational condition of the axial fans are compared quantitatively using the concept of SVE4 calculated by means of tracer gas pulse method to investigate distribution characteristics of the air discharged from each story among the exhausted air to the two exhaust ports in the narrow exhaust tower.

Experimental study on f-ω regulation model under abnormal methane emission

In view of the difficulty of automatic adjustment, the recovery lag and the major accident potential of the mine ventilation system, an experimental model of the pipe net was established according to the typical one mine and one working face ventilation system of Daliuta coal mine. Using the best uniform approximation method of Chebyshev interpolation to fit the fan performance curve, we experimentally determined fan characteristics with different frequencies and establish the data base for the curves. Based on ventilation network monitoring theory, we designed a monitoring system for ventilation network parameter monitoring and fan operating frequency automatic control. Using the absolute methane emission quantity to predict the air quantity requirement of branch and fan frequency, we established a f-ω regulation model based on fan frequency and absolute methane emission quantity. After analysing methane emission and distribution characteristics, using CO2 to simulate the methane emission characteristics from a working face, we verified the correctness and rationality of the f-ω regulation model. The fan operation frequency is adjusted by the method of air adjustment change with methane emission quantity and the curve searching method after determining air quantity requirements. The results show that the air quantity in a branch strictly changes according to the f-ω regulation model, in the air-increasing dilution by fan frequency regulation, the CO2 concentration is limited to the set threshold value. The paper verifies the practicability of a frequency regulation system and the feasibility of the frequency adjustment scheme and provides guidance for the construction of automatic frequency conversion control system in coal mine ventilation networks.

Aircraft Measurements and Numerical Simulations of an Expansion Fan off the California Coast

AbstractMountains along the California coastline play a critical role in the dynamics of marine atmospheric boundary layer (MBL) airflow in the vicinity of the shoreline. Large changes in the MBL topology have been known to occur downwind of points and capes along the western coast of the United States. Large spatial gradients in wind and temperature become established that can cause anomalous electromagnetic wave propagation. Detailed airborne measurements using the University of Wyoming King Air were conducted to study the adjustment of the MBL to the Point Arguello and Point Conception headlands. Pronounced thinning of the MBL consistent with an expansion fan occurred to the south of Point Conception on 13 June 2012. A sharp cloud edge was collocated with the near collapse of the MBL. D-value cross sections derived from differential GPS altitude measurements allow assessment of the vertical profile of the horizontal pressure gradient force and hence thermal wind forcing in response to the near collapse of the MBL. The Weather Research and Forecasting Model was run with a 1-km grid spacing to examine the atmospheric adjustment around Point Conception during this period. Results from the simulations including the vertical cross sections of the horizontal pressure gradient force were consistent with the aircraft observations. Model results suggest that divergence occurs as the flow rounds Point Conception, characteristic of an expansion fan. Wind speeds in the MBL increase coincident with the decrease in MBL thickness, and subsiding flow associated with the near collapse of the MBL is responsible for the sharp cloud edge.