scholarly journals Numerical Analysis of Blade Geometry Generation Techniques for Centrifugal Compressors

2006 ◽  
Author(s):  
Florin Iancu ◽  
John Trevino ◽  
Steven Sommer
Keyword(s):  
Tool Path ◽  
Fluid Dynamic ◽  
Experimental Investigations ◽  
Blade Surface ◽  
Blade Profile ◽  
Dynamic Simulations ◽  
3D Design ◽  
Design Intent ◽  
Performance Improvements ◽  
Compressor Performance

It is a known fact that machined impellers result in improved compressor performance compared to cast impellers of the same design. The performance improvements can be attributed to better surface finish, more accurate geometric definition (tighter dimensional tolerances), well defined edges, and the lack of blade tip fillet on shrouded impellers. In addition, it has been observed through experimental investigations that the construction method of the impellers has an impact on performance. For flank-milled machined impellers, a hub and shroud blade profile is connected by pre-determined straight-line-elements (SLE) - which would correspond to a tool path - to generate the blade surface according to the design intent of the compressor engineer. For cast impellers, the method of connecting hub and shroud blade profile points leads to an arbitrary surface definition and is dependent upon a designer's interpretation of blade profile data and/or the solid model, as well as the CAD software. Although the shape of the hub and shroud profiles are preserved, the resulting blade surface defined by connecting these two profiles may not correspond to the design intent of the compressor engineer. Because the blade surface deviates from the design intent, the compressor performance can deteriorate. Foundries rely on a full 3D design model to create tooling for cast impellers, as opposed to hub and shroud profiles typically required of a 5-axis machining program. Therefore, these construction differences become significant for cast impellers. This paper presents computational fluid dynamic investigations of two types of impellers - with blade surfaces generated using SLE and using CAD arbitrary definitions. Because there are many different mathematical definitions that CAD tools employ for curves, the resulting arbitrary blade surface is not unique. The numerical results will help understand the causes of the performance difference as well as the effects of SLE blades to the flow through the impeller. Input conditions for computational dynamic simulations are based on experimental results. All references to experimental data in the present paper are for cast impellers. Therefore the differences in performance are attributed to blade definition (SLE vs. other) and not to differences resulting from manufacturing methods.

scholarly journals Numerical Analysis of Blade Geometry Generation Techniques for Centrifugal Compressors

2007 ◽  
Vol 2007 ◽  
pp. 1-7 ◽  
Author(s):  
Florin Iancu ◽  
John Trevino ◽  
Steven Sommer
Keyword(s):  
Fluid Dynamic ◽  
Experimental Investigations ◽  
Dynamic Simulations ◽  
Performance Improvements ◽  
Straight Line ◽  
Blade Tip ◽  
Flow Through ◽  
Compressor Performance ◽  
Mathematical Definitions ◽  
Line Elements

It is a known fact that machined impellers result in improved compressor performance compared to cast impellers of the same design. The performance improvements can be attributed to better surface finish, more accurate geometric definition (tighter dimensional tolerances), well-defined edges, and the lack of blade tip fillet on shrouded impellers. In addition, it has been observed through experimental investigations that the construction method of the impellers has an impact on performance. This paper presents computational fluid dynamic investigations of two types of impellers, with blade surfaces generated using straight-line elements (SLEs) and CAD arbitrary definitions. Because there are many different mathematical definitions that CAD tools employ for curves, the resulting arbitrary blade surface is not unique. The numerical results will help understand the causes of the performance differences as well as the effects of SLE blades on the flow through the impeller. Input conditions for computational dynamic simulations are based on experimental results. All references to experimental data in the present paper are for cast impellers. Therefore, the differences in performance are attributed to blade definition (SLE versus other) and not to differences resulting from manufacturing methods.

Towards real-time fire data synthesis using numerical simulations

2021 ◽  
pp. 073490412199344
Author(s):  
Wolfram Jahn ◽  
Frane Sazunic ◽  
Carlos Sing-Long
Keyword(s):  
Real Time ◽  
Computational Fluid Dynamic ◽  
Dynamic Models ◽  
Fluid Dynamic ◽  
Near Field ◽  
Computing Time ◽  
Temperature Correction ◽  
Dynamic Simulations ◽  
Conservation Of Energy ◽  
Fire Scenarios

Synthesising data from fire scenarios using fire simulations requires iterative running of these simulations. For real-time synthesising, faster-than-real-time simulations are thus necessary. In this article, different model types are assessed according to their complexity to determine the trade-off between the accuracy of the output and the required computing time. A threshold grid size for real-time computational fluid dynamic simulations is identified, and the implications of simplifying existing field fire models by turning off sub-models are assessed. In addition, a temperature correction for two zone models based on the conservation of energy of the hot layer is introduced, to account for spatial variations of temperature in the near field of the fire. The main conclusions are that real-time fire simulations with spatial resolution are possible and that it is not necessary to solve all fine-scale physics to reproduce temperature measurements accurately. There remains, however, a gap in performance between computational fluid dynamic models and zone models that must be explored to achieve faster-than-real-time fire simulations.

scholarly journals Analysis of Radial Inflow Turbine Losses Operating with Supercritical Carbon Dioxide

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3561
Author(s):  
Antti Uusitalo ◽  
Aki Grönman
Keyword(s):  
Fluid Dynamic ◽  
Dynamic Simulations ◽  
Average Deviation ◽  
Loss Analysis ◽  
Specific Speed ◽  
Loss Models ◽  
Rotor Losses ◽  
Radial Turbines ◽  
Design Power ◽  
Good Agreement

The losses of supercritical CO2 radial turbines with design power scales of about 1 MW were investigated by using computational fluid dynamic simulations. The simulation results were compared with loss predictions from enthalpy loss correlations. The aim of the study was to investigate how the expansion losses are divided between the stator and rotor as well as to compare the loss predictions obtained with the different methods for turbine designs with varying specific speeds. It was observed that a reasonably good agreement between the 1D loss correlations and computational fluid dynamics results can be obtained by using a suitable set of loss correlations. The use of different passage loss models led to high deviations in the predicted rotor losses, especially with turbine designs having the highest or lowest specific speeds. The best agreement in respect to CFD results with the average deviation of less than 10% was found when using the CETI passage loss model. In addition, the other investigated passage loss models provided relatively good agreement for some of the analyzed turbine designs, but the deviations were higher when considering the full specific speed range that was investigated. The stator loss analysis revealed that despite some differences in the predicted losses between the methods, a similar trend in the development of the losses was observed as the turbine specific speed was changed.

Computational fluid dynamic simulations of coal-fired utility boilers: An engineering tool

Fuel ◽  
2009 ◽  
Vol 88 (1) ◽  
pp. 9-18 ◽  
Author(s):  
Efim Korytnyi ◽  
Roman Saveliev ◽  
Miron Perelman ◽  
Boris Chudnovsky ◽  
Ezra Bar-Ziv
Keyword(s):  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Dynamic Simulations ◽  
Utility Boilers

scholarly journals Performance of Vehicular Visible Light Communications under the Effects of Atmospheric Turbulence with Aperture Averaging

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2751
Author(s):  
Elizabeth Eso ◽  
Zabih Ghassemlooy ◽  
Stanislav Zvanovec ◽  
Juna Sathian ◽  
Mojtaba Mansour Abadi ◽  
...  
Keyword(s):  
Visible Light ◽  
Atmospheric Turbulence ◽  
Signal To Noise Ratio ◽  
Light Emitting Diode ◽  
Experimental Investigations ◽  
Visible Light Communications ◽  
Incoherent Light ◽  
Performance Improvements ◽  
Aperture Averaging ◽  
Induced Signal

In this paper, we investigate the performance of a vehicular visible light communications (VVLC) link with a non-collimated and incoherent light source (a light-emitting diode) as the transmitter (Tx), and two different optical receiver (Rx) types (a camera and photodiode (PD)) under atmospheric turbulence (AT) conditions with aperture averaging (AA). First, we present simulation results indicating performance improvements in the signal-to-noise ratio (SNR) under AT with AA with increasing size of the optical concentrator. Experimental investigations demonstrate the potency of AA in mitigating the induced signal fading due to the weak to moderate AT regimes in a VVLC system. The experimental results obtained with AA show that the link’s performance was stable in terms of the average SNR and the peak SNR for the PD and camera-based Rx links, respectively with <1 dB SNR penalty for both Rxs, as the strength of AT increases compared with the link with no AT.

A Highly Accurate Beam Finite Element for Curved and Twisted Helicopter Blades

2011 ◽  
Author(s):  
Yan Skladanek ◽  
Paul Cranga ◽  
Guy Ferraris ◽  
Georges Jacquet ◽  
Re´gis Dufour
Keyword(s):  
Finite Element ◽  
Twist Angle ◽  
Experimental Investigations ◽  
Rotating Frame ◽  
Blade Design ◽  
Helicopter Blades ◽  
Performance Improvements ◽  
Blade Optimization ◽  
Model Reliability ◽  
Numerical Tools

Blade optimization is more than ever a crucial activity for helicopter manufacturers, always looking for performance improvements, noise reduction and vibratory comfort increase. Latest studies have led to design new blade concepts including a double swept plan shape, an evolutionary and increased twist angle at the tip and a new layout for internal components like roving spars. Such blades exhibit a highly coupled behavior between torsion, longitudinal and bending motions that should be accurately modeled for predictive numerical tools. In this research a highly accurate beam finite element is formulated in the rotating frame to improve the static deformation calculation under aerodynamic and centrifugal loads and thus enhance dynamic and stability analysis usually performed for a helicopter development. Numerical and experimental investigations are performed to demonstrate the model reliability both for academic beams with extreme shape and for actual blade design.

Improving a one-dimensional centrifugal compressor performance prediction method

2005 ◽  
Vol 219 (8) ◽  
pp. 653-659 ◽  
Author(s):  
E Swain
Keyword(s):  
Centrifugal Compressor ◽  
Performance Prediction ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Prediction Method ◽  
Compressor Cascade ◽  
One Dimensional ◽  
Compressor Performance ◽  
Cfd Analyses

A one-dimensional centrifugal compressor performance prediction technique that has been available for some time is updated as a result of extracting the component performance from three-dimensional computational fluid dynamic (CFD) analyses. Confidence in the CFD results is provided by comparison of overall performance for one of the compressor examples. The extracted impeller characteristic is compared with the original impeller loss model, and this indicated that some improvement was desirable. The position of least impeller loss was determined using a traditional axial compressor cascade method, and suitable algebraic expressions were derived to match the CFD data. The merit of the approach lies with the relative ease that CFD component performance currently can be achieved and adjusting one-dimensional methods to agree with the CFD-derived models.

scholarly journals Tests of the sorption and olfactory “fovea” hypotheses in the mouse

2017 ◽  
Vol 118 (5) ◽  
pp. 2770-2788 ◽  
Author(s):  
David M. Coppola ◽  
Brittaney E. Ritchie ◽  
Brent A. Craven
Keyword(s):  
Olfactory Epithelium ◽  
Water Solubility ◽  
Fluid Dynamic ◽  
Water Soluble ◽  
Quiet Breathing ◽  
Cfd Simulations ◽  
Dynamic Simulations ◽  
Consistent Finding ◽  
Sensory Epithelia ◽  
Tactile Stimuli

The spatial distribution of receptors within sensory epithelia (e.g., retina and skin) is often markedly nonuniform to gain efficiency in information capture and neural processing. By contrast, odors, unlike visual and tactile stimuli, have no obvious spatial dimension. What need then could there be for either nearest-neighbor relationships or nonuniform distributions of receptor cells in the olfactory epithelium (OE)? Adrian (Adrian ED. J Physiol 100: 459–473, 1942; Adrian ED. Br Med Bull 6: 330–332, 1950) provided the only widely debated answer to this question when he posited that the physical properties of odors, such as volatility and water solubility, determine a spatial pattern of stimulation across the OE that could aid odor discrimination. Unfortunately, despite its longevity, few critical tests of the “sorption hypothesis” exist. Here we test the predictions of this hypothesis by mapping mouse OE responses using the electroolfactogram (EOG) and comparing these response “maps” to computational fluid dynamics (CFD) simulations of airflow and odorant sorption patterns in the nasal cavity. CFD simulations were performed for airflow rates corresponding to quiet breathing and sniffing. Consistent with predictions of the sorption hypothesis, water-soluble odorants tended to evoke larger EOG responses in the central portion of the OE than the peripheral portion. However, sorption simulation patterns along individual nasal turbinates for particular odorants did not correlate with their EOG response gradients. Indeed, the most consistent finding was a rostral-greater to caudal-lesser response gradient for all the odorants tested that is unexplained by sorption patterns. The viability of the sorption and related olfactory “fovea” hypotheses are discussed in light of these findings. NEW & NOTEWORTHY Two classical ideas concerning olfaction’s receptor-surface two-dimensional organization—the sorption and olfactory fovea hypotheses—were found wanting in this study that afforded unprecedented comparisons between electrophysiological recordings in the mouse olfactory epithelium and computational fluid dynamic simulations of nasal airflow. Alternatively, it is proposed that the olfactory receptor layouts in macrosmatic mammals may be an evolutionary contingent state devoid of the functional significance found in other sensory epithelia like the cochlea and retina.

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