Friction Loss and Wear in a Meso Scale Wankel Compressor

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Yilin Zhang ◽  
Wen Wang
Keyword(s):  
Relative Error ◽  
Volume Ratio ◽  
Internal Surface ◽  
Friction Loss ◽  
Motor Speed ◽  
Eccentric Shaft ◽  
The Common ◽  
Contact Surfaces ◽  
Meso Scale ◽  
Eccentric Distance

In a meso scale Wankel compressor, the surface-to-volume ratio and the contact surfaces with friction are larger compared with conventional scale Wankel compressor. The analysis of friction loss is highly important for the design of a meso scale Wankel compressor. In this paper, we comprehensively analyze seven kinds of friction losses of a meso scale Wankel compressor. The rationality of the friction losses equations is verified by the friction loss and wear experiments that are based on a Wankel compressor prototype (the dimension of prototype is about 40 × 50 × 24 mm). The two greatest contribution of total friction loss are from the friction loss between the seal apex and internal surface of the cylinder and that among the end face of the eccentric shaft, end faces of the rotor, and endplates to total friction loss. The most sensitive parameter is eccentric distance. The relative error between the simulation and experimental results is relatively small when motor speed lies within the common range of the compressor.

Alveolar size as a determinant of pulmonary distensibility in mammalian lungs

1983 ◽  
Vol 54 (3) ◽  
pp. 837-845 ◽  
Author(s):  
P. S. Haber ◽  
H. J. Colebatch ◽  
C. K. Ng ◽  
I. A. Greaves
Keyword(s):  
Static Pressure ◽  
Volume Ratio ◽  
Relative Contribution ◽  
Human Lungs ◽  
Elastic Forces ◽  
Mean Size ◽  
Mean Linear Intercept ◽  
The Common ◽  
The Mean ◽  
Alveolar Surface

Pulmonary distensibility depends on surface tension and tissue elastic forces, but the relative contribution of each to total lung recoil remains incompletely defined. By applying an exponential analysis to static pressure-volume curves obtained from the excised lungs of cats, dogs, and rats with air and saline filling, the exponential constant K (an index of lung distensibility) was related to the mean linear intercept Lm (a morphometric estimate of the mean size of peripheral air spaces at maximal inflation). K for air filling (Ka) was unrelated to K for saline filling (Ks), and Ks was unrelated to Lm, but similar highly significant regressions of Ka on Lm were found in each species, and the common regression was similar to that described previously for human lungs. Approximately 86% of the variance in lung distensibility (Ka) within and between species was explained by Lm. Because Lm determines the size of air spaces, and therefore the alveolar surface-to-volume ratio, the findings indicate that the density of surface forces is the major determinant of lung distensibility in the air-filled state.

Effect of common dead space on VA/Q distribution in the dog

1990 ◽  
Vol 68 (6) ◽  
pp. 2488-2493 ◽  
Author(s):  
K. Tsukimoto ◽  
J. P. Arcos ◽  
W. Schaffartzik ◽  
P. D. Wagner ◽  
J. B. West
Keyword(s):  
Blood Flow ◽  
Tidal Volume ◽  
Dead Space ◽  
Volume Ratio ◽  
Inert Gas ◽  
Base Line ◽  
Heavy Exercise ◽  
The Common ◽  
Technique Comparison ◽  
Condition B

Several previous studies have shown worsening ventilation-perfusion (VA/Q) relationships in humans during heavy exercise at sea level. However, the mechanism of this deterioration remains unclear because of the correlation with ventilatory and circulatory variables. Our hypothesis was that the decrease in the series dead space-to-tidal volume ratio during exercise might be partly responsible because mixing in the common dead space can reduce apparent inequality. We tested this notion in 10 resting anesthetized normocapnic dogs passively hyperventilated by increase tidal volume and a) inspired CO2 or b) external dead space. We predicted less apparent VA/Q inequality in condition b because of mixing in the added dead space. After base-line measurements, conditions a and b were randomly assigned, and after a second set of base-line measurements they were repeated in the reverse order in each dog. VA/Q inequality was measured by the multiple inert gas elimination technique. Comparison of conditions a and b demonstrated that additional external dead space improved (P less than 0.001) the blood flow distributions as hypothesized [log standard deviation of perfusion = 0.49 +/- 0.02 (SE) in condition b and 0.61 +/- 0.03 in condition a with respect to 0.52 +/- 0.03 at base line]. This study suggests that the increased tidal volume during exercise could uncover VA/Q inequality not evident at rest because of the higher ratio of common dead space to tidal volume at rest.

scholarly journals Materials Matter in Microfluidic Devices

MRS Bulletin ◽  
2006 ◽  
Vol 31 (2) ◽  
pp. 95-99 ◽  
Author(s):  
Xunli Zhang ◽  
Stephen J. Haswell
Keyword(s):  
High Surface ◽  
Volume Ratio ◽  
Microfluidic Devices ◽  
Surface Characteristics ◽  
Microfluidic System ◽  
Substrate Material ◽  
Material Choice ◽  
Overall Performance ◽  
The Common ◽  
Selection Of

AbstractAs more micro- and nanofluidic methodologies are developed for a growing number of diverse applications, it becomes increasingly apparent that the choice of substrate material can have a profound effect on the eventual performance of a device. This is due mostly to the high surface-to-volume ratio that exists within such small structures. In addition to the obvious limitations related to the choice of solvent, operating temperatures, and pressure, the method of fluidic pumping—in particular, an electrokinetics-based methodology using a combination of electro-osmotic and electrophoresis flows—can further complicate material choice. These factors, however, are only part of the problem; once chemicals or biological materials (e.g., proteins or cells) are introduced into a microfluidic system, surface characteristics will have a profound influence on the activity of such components, which will subsequently influence their performance. This article reviews the common types of materials that are currently used to fabricate microfluidic devices and considers how these materials may influence the overall performance associated with chemical and biological processing. Consideration will also be given to the selection of materials and surface modifications that can aid in exploiting the high surface properties to enhance process performance.

scholarly journals The effect of the distribution of variable characteristics determining the asymmetry of the sealing rings sliding surfaces on the values of friction loss coefficients and other selected parameters of oil film

2017 ◽  
Vol 171 (4) ◽  
pp. 107-116
Author(s):  
Piotr WRÓBLEWSKI
Keyword(s):  
Friction Loss ◽  
Common Vertex ◽  
Cylinder Wall ◽  
Bearing Surface ◽  
Oil Film ◽  
Sliding Surfaces ◽  
Asymmetric Shape ◽  
Loss Coefficients ◽  
The Common ◽  
Mathematical Relationships

The article presents the results of research on the effect of the change in coordinates that determine the location of the common vertex of the parabolas and ellipses demonstrating the asymmetric shape of the rings sliding surfaces on the change in the thickness of oil film, the amount of scraped oil, and the oil left on the cylinder wall, once a set of selected sealing rings has passed, as well as the results concerning friction losses. Mathematical relationships of the asymmetric shapes of the rings sliding surfaces were presented, and the values of coefficients characterizing selected parameters of oil film and friction losses were determined. It was confirmed that there is a large dependence of the coordinate values of the vertices determining the asymmetric shapes of these surfaces on the condition and cooperation between piston rings and the cylinder bearing surface, and mainly on the amount of the oil scraped in the selected engine strokes.

Comparison of the Friction-Loss Coefficient for the Gap of Two Contact Surfaces and a Crack

2011 ◽  
Vol 35 (10) ◽  
pp. 1075-1081
Author(s):  
Ho-Yun Nam ◽  
Byoung-Hae Choi ◽  
Jong-Bum Kim ◽  
Young-Bum Lee
Keyword(s):  
Loss Coefficient ◽  
Friction Loss ◽  
Contact Surfaces

scholarly journals Hydroxyapatite and bFGF Coating of Detachable Coils for Endovascular Occlusion of Experimental Aneurysm

2003 ◽  
Vol 9 (1_suppl) ◽  
pp. 29-33 ◽  
Author(s):  
T. Shimozuru ◽  
T. Kamezawa ◽  
J. Kuratsu ◽  
N. Sakai ◽  
I. Nagata ◽  
...  
Keyword(s):  
Volume Ratio ◽  
Guglielmi Detachable Coils ◽  
Experimental Aneurysm ◽  
Significant Difference ◽  
Detachable Coils ◽  
The Common ◽  
Fibroblast Growth Factor Basic ◽  
Common Carotid Arteries ◽  
Aneurysm Model ◽  
Made In

The purpose of this study was to evaluate the effect of hydroxyapatite (HAp) and fibroblast growth factor-basic (bFGF) coating on Guglielmi detachable coils (GDCs) in an experimental aneurysm model. A total of 18 aneurysms were experimentally made in the common carotid arteries of swine. Embolization was done on these aneurysms using standard GDCs and coated GDCs with HAp (GDC-HAp) and with bFGF (GDC-HAp-bFGF). The animals were then killed 14 days after embolization. The development of tissue scarring and coverage the aneurysm's orifice were evaluated macroscopically. No significant difference of volume ratio of the coils exited in each groups. Macroscopically, covering ratio of fibrous membrane at the neck of aneurysms were 88.3 ± 14.7% in a group with GDC-HAp-bFGF, while it were 26.7 ± 15.3% in a group with standard GDC and it was 41.7 ± 31.7% in a group with GDC-HAp. These results indicated that coating by hydroxyapatite and bFGF might facilitate a wound healing in an experimental aneurysm model.

Research on Combustion Characteristics of a Jet Flame With Penetration of Side Micro-Jets

2011 ◽  
Author(s):  
Yu-chun Cao ◽  
Zheng-wei Wang
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Flame Structure ◽  
Volume Ratio ◽  
Clean Energy ◽  
Flame Length ◽  
Air Flow Rate ◽  
Jet Flame ◽  
Air Volume ◽  
The Common

Nowadays as clean energy gas is being got more widely utilization in the industrial fields, such as the industrial boilers and kilns. How to improve the combustion performance, including the high efficiency and low pollution emission of the gas flame, is becoming the hot topic for the combustion researchers. In this paper, an innovative jet flame with side micro-jets has been proposed and its effects on the flame structure and its performance have also been investigated. Due to the changes of the initial combustion conditions, mixing and aerodynamics which results from the perturbation of the side micro-jets, such a lifted jet flame have different flame structure compared with the common premixed flame. Results show that use of the micro-jets can control, to a certain extent, the flame structure, including the flame length, lift-off distance and blow-off limit. With the same fuel and air flow rate, the flame length with the side micro-jets will decrease about 5%–40% as the air volume ratio a increases from 58%–76%. Compared with the common diffusion flame, such a jet flame demonstrates to be easier to be momentum-dominated flame. The flame length with 2 micro-jets is about 5% less than with 6 micro-jets under the same fuel and air flow rate. With the same α, the fewer number of the controlled jets lead to the flame with relatively shorter length, not easier to be blown off and higher NOx emission. With certain fuel flow rate, the critical air volume ratio is largest for the flame with 3 micro-jets, which is more difficult to be blown off than the cases with 2, 4 or 6 micro-jets.

Study on the Control Strategy of Slope Starting for Pure Electric Vehicle

2014 ◽  
Vol 721 ◽  
pp. 317-321
Author(s):  
Liang Chu ◽  
Chong Guo ◽  
Pei Zhi Zhang ◽  
Zi Cheng Fu ◽  
Yuan Jian Zhang
Keyword(s):  
Electric Vehicle ◽  
Control Strategy ◽  
Motor Speed ◽  
Low Speed ◽  
The Road ◽  
Prediction Module ◽  
Road Grade ◽  
The Common ◽  
Simulation Results ◽  
Good Feeling

In order to ensure that pure electric vehicle can accurately identify the road grade, and has a high safety and good feeling, this article proposes a control strategy for slope starting of pure electric vehicle. Slope prediction module can accurately calculate and predict the road grade based on motor speed and vehicle-related parameters. Slope starting strategy allows the vehicle to stop on a small slope, and keep a low speed on a large slope, and can make the feeling of slope starting consistent with the common road. This article completed the offline simulation under MATLAB/Simulink, and simulation results showed that the control strategy not only can accurately identify the road grade, but also has a high safety and good feeling.

scholarly journals Accurate and Efficient Explicit Approximations of the Colebrook Flow Friction Equation Based on Wright-Omega Function

2018 ◽  
Author(s):  
Dejan Brkić ◽  
Pavel Praks
Keyword(s):  
Friction Factor ◽  
Relative Error ◽  
Efficient Solution ◽  
Friction Loss ◽  
Series Expansions ◽  
Wright Function ◽  
Lambert Function ◽  
Computationally Efficient ◽  
Flow Friction ◽  
Loss Coefficients

The Colebrook equation is a popular model for estimating friction loss coefficients in water and gas pipes. The model is implicit in the unknown flow friction factor . To date, the captured flow friction factor  can be extracted from the logarithmic form analytically only in the term of the Lambert -function. The purpose of this study is to find an accurate and computationally efficient solution based on the shifted Lambert -function also known as the Wright -function. The Wright -function is more suitable because it overcomes the problem with the overflow error by switching the fast growing term  of the Lambert -function to the series expansions that further can be easily evaluated in computers without causing overflow run-time errors. Although the Colebrook equation transformed through the Lambert -function is identical to the original expression in term of accuracy, a further evaluation of the Lambert -function can be only approximate. Very accurate explicit approximations of the Colebrook equation that contains only one or two logarithms are shown. The final result is an accurate explicit approximation of the Colebrook equation with the relative error of no more than 0.0096%. The presented approximations are in the form suitable for everyday engineering use, they are both accurate and computationally efficient.

scholarly journals Accurate and Efficient Explicit Approximations of the Colebrook Flow Friction Equation Based on the Wright ω-Function

Mathematics ◽  
2018 ◽  
Vol 7 (1) ◽  
pp. 34 ◽  
Author(s):  
Dejan Brkić ◽  
Pavel Praks
Keyword(s):  
Friction Factor ◽  
Relative Error ◽  
Efficient Solution ◽  
Friction Loss ◽  
Lambert W Function ◽  
Series Expansions ◽  
Computationally Efficient ◽  
Flow Friction ◽  
Fast Growing ◽  
Loss Coefficients

The Colebrook equation is a popular model for estimating friction loss coefficients in water and gas pipes. The model is implicit in the unknown flow friction factor, f. To date, the captured flow friction factor, f, can be extracted from the logarithmic form analytically only in the term of the Lambert W-function. The purpose of this study is to find an accurate and computationally efficient solution based on the shifted Lambert W-function also known as the Wright ω-function. The Wright ω-function is more suitable because it overcomes the problem with the overflow error by switching the fast growing term, y=W(ex), of the Lambert W-function to series expansions that further can be easily evaluated in computers without causing overflow run-time errors. Although the Colebrook equation transformed through the Lambert W-function is identical to the original expression in terms of accuracy, a further evaluation of the Lambert W-function can be only approximate. Very accurate explicit approximations of the Colebrook equation that contain only one or two logarithms are shown. The final result is an accurate explicit approximation of the Colebrook equation with a relative error of no more than 0.0096%. The presented approximations are in a form suitable for everyday engineering use, and are both accurate and computationally efficient.

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