Prediction of Flow Behavior and Performance of Squirrel-Cage Centrifugal Fans Operating at Medium and High Flow Rates

1997 ◽  
Vol 119 (3) ◽  
pp. 639-646 ◽  
Author(s):  
R. J. Kind
Keyword(s):  
Reverse Flow ◽  
Flow Behavior ◽  
Design Flow ◽  
Flow Rates ◽  
Factors Affecting ◽  
Squirrel Cage ◽  
Centrifugal Fans ◽  
Flow Phenomena ◽  
And Performance ◽  
Inlet Zone

This paper describes a method for predicting flow behavior and performance for centrifugal fans of the squirrel-cage type. The work is directed at improving under standing of the factors affecting performance of these fans. A simulation approach has been adopted. That is, the fan is subdivided into a number of zones (inlet zone, blading zone, volute zone) and the zones are divided into elements. Flow behavior in the zones and elements and interactions between them are modeled using appropriate equations and correlations. The blading correlations make use of new experimental data for high-solidity cascades of bent sheet metal blades, typical of squirrel-cage fans. Predicted fan performance characteristics are in reasonable agreement with experimental results for flow rates at and above the best-efficiency operating point. Although relatively simple, the method recognizes the main flow phenomena and interactions that occur in squirrel-cage fans and it thus represents a substantial advance over what is currently available in the literature. Together with earlier experimental work, development of the method has provided considerable insight into the relative importance of various aspects of flow behavior. The ability to deal with extensive reverse flow through the rotor blading has not yet been incorporated and it is evident that this ability is essential for realistic prediction of flow behavior and performance at below-design flow rates.

Prediction of Flow Behaviour and Performance of Squirrel-Cage Centrifugal Fans Operating at Medium and High Flow Rates

1996 ◽  
Author(s):  
R. J. Kind
Keyword(s):  
Reverse Flow ◽  
Flow Behaviour ◽  
Design Flow ◽  
Flow Rates ◽  
Factors Affecting ◽  
Squirrel Cage ◽  
Centrifugal Fans ◽  
Flow Phenomena ◽  
And Performance ◽  
Inlet Zone

This paper describes a method for predicting flow behaviour and performance for centrifugal fans of the squirrel-cage type. The work is directed at improving understanding of the factors affecting performance of these fans. A simulation approach has been adopted. That is, the fan is sub-divided into a number of zones (inlet zone, blading zone, volute zone) and the zones are divided into elements. Flow behaviour in the zones and elements and interactions between them are modelled using appropriate equations and correlations. The blading correlations make use of new experimental data for high-solidity cascades of bent sheet metal blades, typical of squirrel-cage fans. Predicted fan performance characteristics are in reasonable agreement with experimental results for flow rates at and above the best-efficiency operating point. Although relatively simple, the method recognizes the main flow phenomena and interactions that occur in squirrel-cage fans and it thus represents a substantial advance over what is currently available in the literature. Together with earlier experimental work, development of the method has provided considerable insight into the relative importance of various aspects of flow behaviour. The ability to deal with extensive reverse flow through the rotor blading has not yet been incorporated and it is evident that this ability is essential for realistic prediction of flow behaviour and performance at below-design flow rates.

scholarly journals Laser-Doppler Velocimetry Measurements Inside a Backward Curved Centrifugal Fan

2001 ◽  
Vol 7 (3) ◽  
pp. 173-181
Author(s):  
Tong-Miin Liou ◽  
Meng-Yu Chen
Keyword(s):  
Flow Rate ◽  
Turbulence Intensity ◽  
Laser Doppler Velocimetry ◽  
Reverse Flow ◽  
Flow Region ◽  
Design Flow ◽  
Laser Doppler ◽  
Centrifugal Fan ◽  
Doppler Velocimetry ◽  
Flow Rates

Laser-Doppler velocimetry (LDV) measurements are presented of relative mean velocity and turbulence intensity components inside the impeller passage of a centrifugal fan with twelve backward curved blades at design, under-design, and over-design flow rates. Additional LDV measurements were also performed at the volute outlet to examine the uniformity of the outlet flow for the three selected flow rates. Complementary flow visualization results in the tongue region are further presented. It is found that the number of characteristic flow regions and the average turbulence level increase with decreasing air flow rate. For the case of under-design flow rate, there are a through-flow region on the suction side, a reverse flow region on the pressure side, and a shear layer region in between. The corresponding average turbulence intensity is as high as 9.1% of blade tip velocity.

Effect of Axial Gap between Diffuser Inlet and Impeller on Efficiency and Flow Pattern of Centrifugal Fans

2013 ◽  
Vol 446-447 ◽  
pp. 621-625
Author(s):  
Mojtaba Gholamian ◽  
Gurram Krishna Mohan Rao ◽  
Bhramara Panitapu
Keyword(s):  
Numerical Simulations ◽  
Flow Pattern ◽  
Squirrel Cage ◽  
Centrifugal Fans ◽  
And Performance

Inlet is one of the basic elements of squirrel cage fan that can have great effect on performance and losses, especially between inlet exit and first section of impeller width. In this paper the effect of axial gap between inlet diffuser and impeller on performance and flow pattern is considered. Three diffuser inlet sizes with respect to impeller size (smaller, nearly same and bigger than inner impeller diameter) and three axial gaps within the available dimensions of the casing and impeller were chosen. Numerical simulations were performed to find the effect of this axial gap on flow pattern, performance and efficiency. From the simulation of each case study, flow pattern and its mechanism and the causes that affecting the efficiency and performance due to axial gap are analyzed and presented.

Asymmetric Flow in Vaneless Diffusers of Centrifugal Blowers

1977 ◽  
Vol 99 (1) ◽  
pp. 104-111 ◽  
Author(s):  
Yasutoshi Senoo ◽  
Yoshifumi Kinoshita ◽  
Masahiro Ishida
Keyword(s):  
Reverse Flow ◽  
Flow Behavior ◽  
Maximum Velocity ◽  
Flow Rates ◽  
Velocity Flow ◽  
Special Relations ◽  
Small Flow ◽  
Vaneless Diffusers ◽  
Momentum Integral ◽  
Large Flow

An analytical method is proposed to evaluate the flow behavior in vaneless diffusers assuming that the flow is not symmetric between the walls. In the analysis momentum integral equations are used together with some special relations for the main flow or for the maximum velocity flow. According to the authors’ experiment, for the case of a small flow rate a reverse flow is observed on one wall near the inlet of the diffuser but at a larger radius the reverse flow disappears and another reverse flow is observed on the other wall. The predictions quantitatively agree well with experiments not only in the case of large flow rates but also in the case of small flow rates where the flow pattern is very complicated.

Flow in a Centrifugal Fan of the Squirrel-Cage Type

1990 ◽  
Vol 112 (1) ◽  
pp. 84-90 ◽  
Author(s):  
R. J. Kind ◽  
M. G. Tobin
Keyword(s):  
Flow Field ◽  
Reverse Flow ◽  
Flow Behavior ◽  
Field Measurements ◽  
Centrifugal Fan ◽  
Performance Measurements ◽  
Mean Flow ◽  
Squirrel Cage ◽  
Flow Through ◽  
The Mean

This paper presents the results of performance measurements and detailed measurements of the mean flow field at rotor inlet and rotor exit in three squirrel-cage fan configurations. The flow-field measurements were taken with a five-hole probe and yield total pressure, static pressure, and the three components of velocity. Measurements were taken for two casing throat areas and for two different rotors. For each configuration the flow field was measured for flow rates below, near, and above the best-efficiency point. Flow patterns are complex and there is reverse flow through the rotor blading even at the best-efficiency operating condition. Although complex, the main features of flow behavior can be understood. They were common to all three fan configurations.

Design and Numerical Flow Analysis of a LNG Power Recovery Turbine

2013 ◽  
Author(s):  
Kaiqiang Li ◽  
Jinju Sun ◽  
Juntao Fu ◽  
Peng Song
Keyword(s):  
High Pressure ◽  
Flow Rate ◽  
Flow Behavior ◽  
Leading Edge ◽  
Cavitating Flow ◽  
Design Flow ◽  
Technical Requirement ◽  
Edge Region ◽  
Flow Rates ◽  
Overall Efficiency

The liquefaction process of natural gas often operates at high pressure level, thus the LNG product is of very high pressure and must be reduced to satisfy the technical requirement for storage and transportation. Traditionally, the high-pressure LNG is expanded isenthalpically by means of J-T valves but this introduces an unexpected temperature rise, leading to vaporization of LNG product and subsequently a reduced delivery. An efficient alternative is using the LNG expanders to replace the J-T valves and achieve a near-isentropic expansion and subsequently suppress the cavitation. In the present study, a single stage LNG turbine expander is developed as a replacement of J-T valve for the purpose of cavitation suppression. The cavitating flow behavior is investigated by using a multiphase cavitation model. The effect of impeller geometric parameters on the turbine flow and performance has been identified through sensitivity studies. The following are demonstrated: (1) The predicted turbine overall efficiency is 91.34%, shaft power delivery is 81.16kW, temperature drop is 0.84 K; and the overall vaporization rate is less than a percentage. (2) Cavitation is encountered in the impeller leading edge region and half stream-wise region, resulting respectively from the viscous dissipation and flow separation. (3) At larger than design flow rates, the predicted turbine overall efficiency decreases nonlinearly with the flow rate due to cavitation zone growth in the leading edge region; at lower than design flow rates, the overall efficiency increases with the flow rate, due to cavitation zone decrease in the half streamwise region. (4) Cavitating flow behavior is sensitive to impeller geometry tuning. Variation of the impeller inducer twist angle reduces the trialing edge cavitation and subsequently improves the turbine overall performance. (5) Cavitation flow behavior is also sensitive to the radial gap size of the nozzle and impeller.

Hygienic assessment of learning environment conditions (by the example of higher educational institutions of the city of Ufa)

2020 ◽  
Vol 99 (4) ◽  
pp. 405-411
Author(s):  
Elena Ju. Gorbatkova
Keyword(s):  
Ionizing Radiation ◽  
Educational Institutions ◽  
Higher Educational Institutions ◽  
Factors Affecting ◽  
Republic Of Bashkortostan ◽  
Average Relative Humidity ◽  
Higher Educational ◽  
The Republic ◽  
And Performance ◽  
The City

Introduction. The important factors affecting health and performance of young people are the conditions of education, in particular, a comfortable microclimate in the classrooms of higher educational institutions. Materials and methods. In view of the urgency of this problem, an analysis was made of the microclimate parameters of educational organizations of different profiles (Ufa city, the Republic of Bashkortostan). 294 classrooms were studied in 22 buildings of 4 leading universities in Ufa. A total of 3,822 measurements were taken to determine the parameters of the microclimate. The analysis of ionizing radiation in the aerial environment of classrooms. There was performed determination of radon and its affiliated products content. In order to assess the conditions and lifestyle of students of 4 higher educational institutions of the city of Ufa, we conducted an anonymous survey of 1,820 students of I and IV years of education. Results. The average temperature in the classrooms of all universities studied was 23.9±0.09 C. The average relative humidity in all classrooms was 34.2 ± 0.42%. Analysis of ionizing radiation (radon and its daughter products decay) in the aerial environment of the classrooms and sports halls located in the basement determined that the average annual equivalent equilibrium volumetric activity of the radon daughter products (EROA ± Δ222Rn) ranged from 28 ± 14 to 69 ± 34.5 meter, which meets the requirements established by SanPiN. Conclusion. The hygienic assessment of the microclimate parameters of educational institutions of various profile revealed a number of deviations from the regulated norms. The results indicate the need to control the parameters of the microclimate, both from the administration of universities, and from the professors. According to the results of the study, recommendations were prepared for the management of higher educational institutions in Ufa.

Thermodynamics of Flowing Systems: with Internal Microstructure

1994 ◽  
Author(s):  
Antony N. Beris ◽  
Brian J. Edwards
Keyword(s):  
Free Energy ◽  
Theoretical Study ◽  
Flow Behavior ◽  
Irreversible Thermodynamics ◽  
Hamiltonian Mechanics ◽  
Complex Interplay ◽  
Microscopic Models ◽  
Flow Phenomena ◽  
The Subject ◽  
The Continuum

This much-needed monograph presents a systematic, step-by-step approach to the continuum modeling of flow phenomena exhibited within materials endowed with a complex internal microstructure, such as polymers and liquid crystals. By combining the principles of Hamiltonian mechanics with those of irreversible thermodynamics, Antony N. Beris and Brian J. Edwards, renowned authorities on the subject, expertly describe the complex interplay between conservative and dissipative processes. Throughout the book, the authors emphasize the evaluation of the free energy--largely based on ideas from statistical mechanics--and how to fit the values of the phenomenological parameters against those of microscopic models. With Thermodynamics of Flowing Systems in hand, mathematicians, engineers, and physicists involved with the theoretical study of flow behavior in structurally complex media now have a superb, self-contained theoretical framework on which to base their modeling efforts.

scholarly journals Investigation of Separation Phenomena in a Radial Pump at Reduced Flow Rate by Large-Eddy Simulation

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Antonio Posa ◽  
Antonio Lippolis ◽  
Elias Balaras
Keyword(s):  
Reverse Flow ◽  
Leading Edge ◽  
Suction Side ◽  
Secondary Flows ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Turbulent Statistics ◽  
Large Eddy ◽  
Radial Pump ◽  
Reduced Flow

Turbopumps operating at reduced flow rates experience significant separation and backflow phenomena. Although Reynolds-Averaged Navier–Stokes (RANS) approaches proved to be usually able to capture the main flow features at design working conditions, previous numerical studies in the literature verified that eddy-resolving techniques are required in order to simulate the strong secondary flows generated at reduced loads. Here, highly resolved large-eddy simulations (LES) of a radial pump with a vaned diffuser are reported. The results are compared to particle image velocimetry (PIV) experiments in the literature. The main focus of the present work is to investigate the separation and backflow phenomena occurring at reduced flow rates. Our results indicate that the effect of these phenomena extends up to the impeller inflow: they involve the outer radii of the impeller vanes, influencing significantly the turbulent statistics of the flow. Also in the diffuser vanes, a strong spanwise evolution of the flow has been observed at the reduced load, with reverse flow, located mainly on the shroud side and on the suction side (SS) of the stationary channels, especially near the leading edge of the diffuser blades.

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