Accurate Calculation of the Slip Factor of Axial Cascades and Impellers for Arbitrary Blade Shapes

2011 ◽  
Author(s):  
Henrik Smith ◽  
Matthias Semel ◽  
Philipp Epple ◽  
Mihai Miclea-Bleiziffer ◽  
Antonio Delgado
Keyword(s):  
Design Process ◽  
Accurate Calculation ◽  
Axial Fan ◽  
One Dimensional ◽  
Slip Factor ◽  
Angle Correction ◽  
Line Theory ◽  
Axial Fans ◽  
The One ◽  
Real Flow

Nowadays, design, redraft and optimisation strategies of axial fans often still rely on the one dimensional mean line theory. However, as it is well known, it is based on a number of assumptions that do not apply to real flow behaviour so that various deviations can be observed. In the present paper, the plane potential theory is used to examine and calculate these deviations. The behaviour of axial cascades is analysed in general and a slip factor is computed. On this basis a quasi-3D calculation method is developed. It is applied to an exemplary impeller and the results are compared with 3D CFD computations. The main characteristic figures are presented and different angle correction and angle exaggeration methods are investigated and compared. Finally, the applicability of the presented method to a precise axial fan design process is illustrated.

Exact Solution of the Plane Flow and Slip Factor in Arbitrary Radial Blade Channels and Extended Design Method for Radial Impellers

2010 ◽  
Author(s):  
Tobias Hetzer ◽  
Philipp Epple ◽  
Antonio Delgado
Keyword(s):  
Exact Solution ◽  
Potential Theory ◽  
Design Method ◽  
Characteristic Curves ◽  
Plane Flow ◽  
One Dimensional ◽  
Slip Factor ◽  
Line Theory ◽  
The One

Since the one dimensional mean line theory, sometimes complemented with calculations of slip factors and used for design of impellers usually leads to considerable deviations from reality the plane potential theory is used to get a better insight on the flow inside the impeller and to predict characteristic curves. Investigations presented here show that it is possible to calculate the exact solution of the plane flow and slip factor in arbitrary radial blade channels. This can be used in an extended design method for radial impellers which is suggested by the authors.

Axial Fan Blade Tone Cancellation Using Optimally Tuned Quarter Wavelength Resonators

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Lee Gorny ◽  
Gary H. Koopmann
Keyword(s):  
Sound Field ◽  
Test Facility ◽  
Secondary Source ◽  
Axial Fan ◽  
Ducted Fan ◽  
Quarter Wavelength ◽  
Centrifugal Fans ◽  
Line Theory ◽  
Axial Fans ◽  
Fan Blade

Fan noise challenges noise control engineers in developing products ranging in scale from small ventilation systems to large turbomachines. The dominant noise source in many axial fans is the tonal noise due to rotor/stator interactions at the fundamental blade passing frequency. Flow-excited resonators have been used in the past for minimizing blade tone sound pressure levels (SPLs) generated by centrifugal fans through means of secondary source cancellation. The focus of this research is to extend that cancellation method to axial fans by attaching flow-driven quarter wavelength resonators fitted with optimal mouth perforations around the perimeter of the fan’s shroud. A ducted-fan test facility was developed to measure upstream and downstream noise radiated from a test fan. Resonators were mounted at specific locations around the fan’s shroud to obtain reductions in blade tone SPLs in both flow directions. They were driven into resonance via the unsteady pressure from the passing blades. An analytical model using transmission line theory was developed and validated experimentally to characterize the resonator’s behavior under various flow conditions and mouth geometries. This model was used to predict the resonator’s potential for reducing in-duct blade tones for specific flows and mouth perforation patterns. In a series of experiments to obtain the optimal resonator mouth perforations, it was observed that upstream and downstream SPL attenuations require different placement of the resonator mouth relative to the blade of the fan. With a single tuned resonator it was demonstrated that the fundamental blade tone SPLs can be reduced by as much as 20 dB in either the upstream or the downstream duct but not in both directions simultaneously. This behavior results when combining the resonator’s monopolelike sound field with the dipolelike sound field of the fan’s blades. Further studies are underway to extend the above method to higher pressure fans operating at speeds that generate higher order duct modes.

Exploring the Multidimensional Facets of Authoritarianism: Authoritarian Aggression and Social Dominance Orientation

2008 ◽  
Vol 67 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Stefano Passini
Keyword(s):  
Social Dominance ◽  
Factor Model ◽  
Three Dimensional ◽  
Social Dominance Orientation ◽  
Model Fit ◽  
Regression Analyses ◽  
One Dimensional ◽  
Confirmatory Factor ◽  
The One ◽  
Better Than

The relation between authoritarianism and social dominance orientation was analyzed, with authoritarianism measured using a three-dimensional scale. The implicit multidimensional structure (authoritarian submission, conventionalism, authoritarian aggression) of Altemeyer’s (1981, 1988) conceptualization of authoritarianism is inconsistent with its one-dimensional methodological operationalization. The dimensionality of authoritarianism was investigated using confirmatory factor analysis in a sample of 713 university students. As hypothesized, the three-factor model fit the data significantly better than the one-factor model. Regression analyses revealed that only authoritarian aggression was related to social dominance orientation. That is, only intolerance of deviance was related to high social dominance, whereas submissiveness was not.

Adiabatic large polarons in anisotropic molecular crystals

2011 ◽  
Vol 35 (1) ◽  
pp. 15-27
Author(s):  
Zoran Ivić ◽  
Željko Pržulj
Keyword(s):  
Energy Transfer ◽  
Effective Mass ◽  
Molecular Crystals ◽  
Single Chain ◽  
Proper Understanding ◽  
One Dimensional ◽  
Interchain Coupling ◽  
Large Polaron ◽  
The One

Adiabatic large polarons in anisotropic molecular crystals We study the large polaron whose motion is confined to a single chain in a system composed of the collection of parallel molecular chains embedded in threedimensional lattice. It is found that the interchain coupling has a significant impact on the large polaron characteristics. In particular, its radius is quite larger while its effective mass is considerably lighter than that estimated within the one-dimensional models. We believe that our findings should be taken into account for the proper understanding of the possible role of large polarons in the charge and energy transfer in quasi-one-dimensional substances.

Modelling Techniques in Applied Glaciology: Numerical Modelling of Avalanches

1983 ◽  
Vol 4 ◽  
pp. 297-297
Author(s):  
G. Brugnot
Keyword(s):  
Finite Difference Method ◽  
Transverse Velocity ◽  
Longitudinal Velocity ◽  
Momentum Conservation ◽  
Dimensional Model ◽  
One Dimensional ◽  
Modelling Techniques ◽  
Reference Grid ◽  
The One ◽  
Near Future

We consider the paper by Brugnot and Pochat (1981), which describes a one-dimensional model applied to a snow avalanche. The main advance made here is the introduction of the second dimension in the runout zone. Indeed, in the channelled course, we still use the one-dimensional model, but, when the avalanche spreads before stopping, we apply a (x, y) grid on the ground and six equations have to be solved: (1) for the avalanche body, one equation for continuity and two equations for momentum conservation, and (2) at the front, one equation for continuity and two equations for momentum conservation. We suppose the front to be a mobile jump, with longitudinal velocity varying more rapidly than transverse velocity.We solve these equations by a finite difference method. This involves many topological problems, due to the actual position of the front, which is defined by its intersection with the reference grid (SI, YJ). In the near future our two directions of research will be testing the code on actual avalanches and improving it by trying to make it cheaper without impairing its accuracy.

Effect of leakage and blockage on the acoustic behavior of particle filters

2019 ◽  
Vol 67 (6) ◽  
pp. 483-492
Author(s):  
Seonghyeon Baek ◽  
Iljae Lee
Keyword(s):  
Transfer Matrix ◽  
Particle Filters ◽  
Acoustic Analysis ◽  
Transmission Loss ◽  
One Dimensional ◽  
Filter System ◽  
The Difference ◽  
The One ◽  
Analytical Approaches ◽  
Good Agreement

The effects of leakage and blockage on the acoustic performance of particle filters have been examined by using one-dimensional acoustic analysis and experimental methods. First, the transfer matrix of a filter system connected to inlet and outlet pipes with conical sections is measured using a two-load method. Then, the transfer matrix of a particle filter only is extracted from the experiments by applying inverse matrices of the conical sections. In the analytical approaches, the one-dimensional acoustic model for the leakage between the filter and the housing is developed. The predicted transmission loss shows a good agreement with the experimental results. Compared to the baseline, the leakage between the filter and housing increases transmission loss at a certain frequency and its harmonics. In addition, the transmission loss for the system with a partially blocked filter is measured. The blockage of the filter also increases the transmission loss at higher frequencies. For the simplicity of experiments to identify the leakage and blockage, the reflection coefficients at the inlet of the filter system have been measured using two different downstream conditions: open pipe and highly absorptive terminations. The experiments show that with highly absorptive terminations, it is easier to see the difference between the baseline and the defects.

The One-dimensional Range Imaging of Linear Target Based on Compressive Sensing

2014 ◽  
Vol 35 (3) ◽  
pp. 568-574 ◽  
Author(s):  
Zhi-zhen Zhu ◽  
Zhi-da Zhang ◽  
Fa-lin Liu ◽  
Bin-bing Li ◽  
Chong-bin Zhou
Keyword(s):  
Compressive Sensing ◽  
Range Imaging ◽  
One Dimensional ◽  
The One ◽  
Dimensional Range
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