Dynamic characteristics of threshold value and extension field selections for vacuum-blowing cleaning system

2021 ◽  
Author(s):  
Yuan Xi ◽  
Yan Dai ◽  
Xi-long Zhang ◽  
Gaohong He
Keyword(s):  
Average Velocity ◽  
Structural Parameters ◽  
Threshold Value ◽  
Structural Parameter ◽  
Extension Field ◽  
Cleaning System ◽  
Simulation Calculation ◽  
Computational Fluid Dynamics Cfd ◽  
Computational Resources ◽  
Grid Computation

To provide theoretical guidelines for threshold value selections on performance characteristics of extension field, the flow characteristic in the vacuum-blowing cleaning system was simulated using the average velocity and pressure of the front inlet surface, and the average velocity of the outlet surface, as indices to evaluate the effect of the extension field’s structural parameters. It is found that the extension field parameters have implications for the simulation calculation, and that each parameter has a corresponding threshold. If the structural parameter is greater than the corresponding threshold, the calculation result is not affected, and the threshold values are analyzed by using computational fluid dynamics (CFD). The dimensions of the front, back, left, and right extension fields are recommended as follows: lf=lb=ll=lr=210 mm and θf =θb =θl =θr =55 degree. The flow field distribution characteristic does not have a distinct difference with or without the extension field corner. The extension field with a corner can be used if high accuracy is required. However, to reduce the amount of grid computation and shorten the calculation time, the corner extension field model is not recommended. Finally, the simulation results are verified experimentally and can be used to improve the calculation accuracy and reduce the required computational resources.

Influence of Key Structural Parameters of Combustion Chamber on the Performance of Diesel Engine

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Xinhai Li ◽  
Yong Cheng ◽  
Shaobo Ji ◽  
Xin Lan
Keyword(s):  
Diesel Engine ◽  
Combustion Chamber ◽  
Dynamic Characteristics ◽  
Peak Pressure ◽  
Structural Parameters ◽  
Structural Parameter ◽  
Engine Combustion ◽  
Computational Fluid Dynamics Cfd ◽  
Soot Emissions ◽  
No Emissions

The structural parameters of combustion chamber have great impacts on the process of air–fuel mixing, combustion, and emissions of diesel engine. The dynamic characteristics and emission performances could be improved by means of optimizing the parameters of the combustion chamber. In this paper, the key structure of a diesel engine combustion chamber is parameterized, and the influence of individual structural parameter on dynamic characteristics and emissions of the engine is simulated and analyzed by computational fluid dynamics (CFD) software avl-fire. The results show that under constant compression ratio, the in-cylinder peak pressure decreases with increasing inclination angle of the combustion chamber (α), while the height (Tm) and bowl radius (R) have little influence on the in-cylinder peak pressure. With increasing α, NO emissions decrease, and soot emissions first increase and then decrease. With increasing R, both NO and soot emissions decrease first and then increase. Therefore, the combustion chamber parameters could be optimized by comprehensive consideration of cylinder pressure, NO and soot emissions.

Research on CFD Simulation of the Cement Slurry Mixer

2012 ◽  
Vol 621 ◽  
pp. 196-199
Author(s):  
Shui Ping LI ◽  
Ya Li Yuan ◽  
Lu Gang Shi
Keyword(s):  
Flow Field ◽  
High Performance ◽  
Cfd Simulation ◽  
Structural Parameters ◽  
Internal Flow ◽  
Simulation Method ◽  
Cement Slurry ◽  
Fluid Machinery ◽  
Computational Fluid Dynamics Cfd ◽  
Machinery Design

Numerical simulation method of the internal flow field of fluid machinery has become an important technology in the study of fluid machinery design. In order to obtain a high-performance cement slurry mixer, computational fluid dynamics (CFD) techniques are used to simulate the flow field in the mixer, and the simulation results are studied. According to the analysis results, the structural parameters of the mixer are modified. The results show the mixer under the revised parameters meet the design requirements well. So CFD analysis method can shorten design period and provide valuable theoretical guidance for the design of fluid machinery.

scholarly journals Wavelet multi-resolution approximation of time-varying frame structure

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879559 ◽  
Author(s):  
Min Xiang ◽  
Feng Xiong ◽  
Yuanfeng Shi ◽  
Kaoshan Dai ◽  
Zhibin Ding
Keyword(s):  
Parameter Estimation ◽  
Degrees Of Freedom ◽  
Structural Parameters ◽  
Identification Problem ◽  
Frame Structure ◽  
Structural Parameter ◽  
Time Varying ◽  
Engineering Structures ◽  
Time Frequency ◽  
Non Parametric

Engineering structures usually exhibit time-varying behavior when subjected to strong excitation or due to material deterioration. This behavior is one of the key properties affecting the structural performance. Hence, reasonable description and timely tracking of time-varying characteristics of engineering structures are necessary for their safety assessment and life-cycle management. Due to its powerful ability of approximating functions in the time–frequency domain, wavelet multi-resolution approximation has been widely applied in the field of parameter estimation. Considering that the damage levels of beams and columns are usually different, identification of time-varying structural parameters of frame structure under seismic excitation using wavelet multi-resolution approximation is studied in this article. A time-varying dynamical model including both the translational and rotational degrees of freedom is established so as to estimate the stiffness coefficients of beams and columns separately. By decomposing each time-varying structural parameter using one wavelet multi-resolution approximation, the time-varying parametric identification problem is transformed into a time-invariant non-parametric one. In solving the high number of regressors in the non-parametric regression program, the modified orthogonal forward regression algorithm is proposed for significant term selection and parameter estimation. This work is demonstrated through numerical examples which consider both gradual variation and abrupt changes in the structural parameters.

Studies of molecular structure parameters of 20-piperidin-2-yl-5α-pregnan-3β,20-diol and its N-methyl derivative: two inhibitors of Δ24(25) sterol methyl transferase and Δ24(24′) sterol methyl reductase of Trypanosoma cruzi

2001 ◽  
Vol 57 (5) ◽  
pp. 714-721 ◽  
Author(s):  
Reinaldo Atencio ◽  
Gonzalo Visbal ◽  
Sara Pekerar ◽  
Jham Papale ◽  
Julio A. Urbina
Keyword(s):  
Trypanosoma Cruzi ◽  
Structural Parameters ◽  
Spectroscopic Characterization ◽  
Structural Parameter ◽  
Torsion Angles ◽  
Methyl Transferase ◽  
X Ray ◽  
The Family ◽  
Fused Ring ◽  
The Mean

Molecular structural parameters of two potential drugs against Trypanosoma cruzi epimastigotes, 20-piperidin-2-yl-5α-pregnan-3β,20-diol (1) and 20-N-methylpiperidin-2-yl-5α-pregnan-3β, 20-diol (2) were studied using a combination of a stereoselective synthetic route, spectroscopic characterization and single-crystal X-ray analysis. Both compounds were synthesized with an R configuration at C20. This chirality is a consequence of the stereoselectivity observed during the formation of the intermediate 20-pyridin-2-yl-5α-pregnan-3β,20R-diol (4). NMR data indicated that the six-membered aza ring of (2) is conformationally more restrained, in CDCl3 solution, than (1). X-ray studies showed that maximum deviations among structural molecular parameters of (1) and (2) correspond to torsion angles along the C20—C22 bonds, leading to a different relative orientation of the N atom; a critical structural parameter for the binding properties of aza-sterols to Δ24(25) sterol methyl transferase. Cremer–Pople parameters of the five-membered rings of (1) and (2) lie in the observed range for a family of tetracyclic fused ring systems retrieved from the CSD. The φ2 parameter of (1) lies just on the mean of the family, while φ2 of (2) deviates significantly towards the lower limit.

The Simplified Flow Field Analysis Method of Multi-Layers Parallel Plates Perfusion Bioreactor

2013 ◽  
Vol 477-478 ◽  
pp. 191-196
Author(s):  
Yu Bao Gao ◽  
Wei Hong Zhou ◽  
Lu Shan Cen ◽  
Yu Cong Xu ◽  
Jiu Xing Liang ◽  
...  
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Structural Parameters ◽  
Field Analysis ◽  
Perfusion Bioreactor ◽  
Parallel Plates ◽  
Established Relationship ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Field Analysis ◽  
Flow Shear Stress

Multi-layers parallel plates perfusion bioreactor has the potential advantage in cells cultivation of tissue engineering and good scalability for cells cultivation on a large scale. It is necessary to analyze the distribution of flow shear stress (FSS) of bioreactors which has strong influence on the growth of cells. The result of meshing was not satisfactory because of the complexity of multi-layers parallel plates when using computational fluid dynamics (CFD) to analyze the FSS, and the amount of calculation was great and complex especially under the process of influence on FSS caused by analyzing the different structure. The new method of simplified flow field analysis was presented in this paper, which was based on relation between FSS and flow and made the process simpler by analyzing distribution of rate instead of FSS. The simulation result showed that this method can satisfy the requirement of precision and provide reference for the analysis of the flow field which had the established relationship between structural parameters and laminar flow within it.

Review of Cardiac Pacemaker Lead Designs for Computational Models in a VR Environment

2017 ◽  
Author(s):  
Bethany Tourek ◽  
Dan Orban ◽  
Lingyu Meng ◽  
Hakizumwami Birali Runesha ◽  
Dan Keefe ◽  
...  
Keyword(s):  
Computational Models ◽  
Cardiac Pacemaker ◽  
Model Complexity ◽  
Element Analysis ◽  
Parameterized Design ◽  
Pacemaker Leads ◽  
Computational Fluid Dynamics Cfd ◽  
The Right ◽  
Implantable Cardiac Pacemaker ◽  
Computational Resources

An implantable cardiac pacemaker is used to modify and treat irregular heartbeats [1] and invented in 1958 [2]. Devices have no fixation or fixed to the heart wall. No fixation leads lay in the bottom of heart cavities, while fixed leads have tines (passive) or a helix screw (active) to attach to the heart. Lead geometries and material properties vary between companies, with geometric sizing based primarily on the internal mechanics of the lead. Finite element analysis (FEA), computational fluid dynamics (CFD) and bench-top simulations are used to evaluate cardiac leads. These simulations analyze only one lead and struggle to compare and test variations in lead designs. Advanced computational resources can run many computer simulations of anatomical environments, however model complexity increases the time to run each simulation. To address this issue, we present a simplified parameterized design space for cardiac pacemaker leads in the right atrium. This information will be used to run multiple simulations of leads in blood flow, for visualization in a single virtual reality (VR) environment and allow the designer to iterate through many design variations (See Figure 1).

Derivatives and Parameter Designs of Arbitrary Cross-Section Inhomogenous Beams’ Modes

2013 ◽  
Author(s):  
J. W. Xing ◽  
G. T. Zheng
Keyword(s):  
Cantilever Beam ◽  
Cross Section ◽  
Analytical Solutions ◽  
Structural Parameters ◽  
Arbitrary Cross Section ◽  
Mode Shapes ◽  
Design Parameters ◽  
Structural Parameter ◽  
Highly Sensitive ◽  
Sensitivity Analysis Method

As highly sensitive to structural parameter variations, it is necessary to study relations between derivatives of displacement modes and structural design parameters. This paper proposes an integral technique for obtaining the analytical solutions of slope and curvature modes of arbitrary cross-section inhomogeneous cantilever beam. The method is validated by comparing the computation results of modal frequencies and shapes with both numerical and analytical solutions. Furthermore, based on the presented method, we have established explicit expressions for the structural parameters sensitivity of the slope/curvature mode shapes. An example of parameter design is also presented for a cantilever beam with the proposed sensitivity analysis method.

THE EFFECTS OF EXTENSIONAL STRESS ON RED BLOOD CELL HEMOLYSIS

2015 ◽  
Vol 27 (05) ◽  
pp. 1550042 ◽  
Author(s):  
Jen-Hong Yen ◽  
Sheng-Fu Chen ◽  
Ming-Kai Chern ◽  
Po-Chien Lu
Keyword(s):  
Shear Stress ◽  
Blood Cell ◽  
Prediction Models ◽  
Cell Damage ◽  
Threshold Value ◽  
Shear Stresses ◽  
Flow Conditions ◽  
Extensional Stress ◽  
Computational Fluid Dynamics Cfd ◽  
Stress Flow

Artificial prostheses create non-physiologic flow conditions with stress forces that may induce blood cell damage, particularly hemolysis. Earlier computational fluid dynamics (CFD) prediction models based on a quantified power model showed significant discrepancies with actual hemolysis experiments. These models used the premise that shear stresses act as the primary force behind hemolysis. However, additional studies have suggested that extensional stresses play a more substantial role than previously thought and should be taken into account in hemolysis models. We compared extensional and shear stress flow fields within the contraction of a short capillary with sharp versus tapered entrances. The flow field was calculated with CFD to determine stress values, and hemolysis experiments with porcine red blood cells were performed to correlate the effects of extensional and shear stress on hemolysis. Our results support extensional stress as the primary mechanical force involved in hemolysis, with a threshold value of 1000 Pa under exposure time less than 0.060 ms.

Blood Pressure Parameters as Determinants of Small Artery Structure in Human Essential Hypertension

1997 ◽  
Vol 92 (6) ◽  
pp. 551-557 ◽  
Author(s):  
Anne Cooper ◽  
Anthony M. Heagerty
Keyword(s):  
Blood Pressure ◽  
Essential Hypertension ◽  
Pulse Pressure ◽  
Structural Parameters ◽  
Structural Parameter ◽  
Pressure Measurements ◽  
Significant Determinant ◽  
Small Artery ◽  
Small Arteries ◽  
Blood Pressures

1. Adaptive changes in small arteries may be more closely correlated with pulse pressure than with systolic, diastolic or mean blood pressures in human essential hypertension. 2. An analysis was performed on the structure of small arteries, age and blood pressure measurements obtained from 56 patients with untreated essential hypertension and 56 matched normotensive volunteers to examine the association between age, blood pressure and small artery structural parameters. 3. Essential hypertension was associated with an increase in media thickness and a decrease in lumen diameter, resulting in an increase in media/lumen ratio. 4. There was a significant correlation between age and media/lumen ratio in normotensive volunteers but not in patients with essential hypertension. 5. There was no correlation between any blood pressure and structural parameter in normotensive volunteers. 6. Both diastolic and mean blood pressures in essential hypertension correlated with media/lumen ratio (P < 0.01); systolic blood pressure correlated less well (P < 0.02). However, pulse pressure did not correlate with media/lumen ratio, suggesting that it is not a significant determinant of small artery structure in untreated essential hypertension.

Study on Relationship between Structural Parameter and Performance of Gas-Solid Separator

2011 ◽  
Vol 415-417 ◽  
pp. 1516-1520
Author(s):  
Xue Ping Wang ◽  
Zhen Wei Zhang
Keyword(s):  
Numerical Simulation ◽  
Gas Flow ◽  
Separation Efficiency ◽  
Structural Parameters ◽  
Structural Parameter ◽  
Exhaust Pipe ◽  
Cyclone Separator ◽  
Structure Parameter ◽  
Gas Field ◽  
And Performance

This paper mainly focuses on the numerical simulation of the gas flow field of cyclone separator. The authors took advanced of RSM turbulence model of software Fluent to simulate the gas field. The regulations among structure parameter of exhaust pipe, pressure lose and separation efficiency can be obtained according to the numerical simulation results under the situation of changing the structural parameters. The conclusion of this paper can put forward the theoretical reference for the structure optimization of cyclone separation.

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