Effects of slide-to-roll ratio and varying velocity on the lubrication performance of grease at low speed

2021 ◽  
pp. 135065012199336
Author(s):  
Yiming Han ◽  
Jing Wang ◽  
Xuyang Jin ◽  
Shanshan Wang ◽  
Rui Zhang
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Industrial Applications ◽  
Transient Effects ◽  
Disintegration Time ◽  
Low Speed ◽  
Existence Time ◽  
Pure Rolling ◽  
Lubrication Performance ◽  
Long Time

Under steady-state pure rolling conditions with low speed, the thickener fiber agglomerations can be maintained for a long time, generating a beneficial thicker film thickness. However, in industrial applications, motions with sliding or transient effects are very common for gears, rolling-element bearings or even chain drives, evaluation of the grease performance under such conditions is vital for determining the lubrication mechanism and designing new greases. In this project, optical interferometry experiments were carried out on a ball-disk test rig to study the disintegration time of the grease thickener agglomerations with the increase of the slide-to-roll ratio under steady-state and reciprocation motions. Under steady-state conditions, the thickener fiber agglomeration can exist for a while and the time becomes shorter with the increase of the slide-to-roll ratio above the critical speed. Below the critical speed, the thickener fiber can exist in the contact in the form of a quite thick film for a very long time under pure rolling conditions but that time is decreased with the increase of the slide-to-roll ratio. The introduction of the transient effect can further reduce the existence time of the thickener.

Prediction and Comparison of Critical Speeds and Potential Excitation Using In-House Developed Software for an Integrally Geared Centrifugal Air Compressor

2014 ◽  
Author(s):  
Mathew P. James ◽  
Pavan Kumar Reddy Pandillapalli ◽  
Swaminathan Gopalakrishnan
Keyword(s):  
Steady State ◽  
Computer Program ◽  
Critical Speed ◽  
Maximum Amplitude ◽  
Sound Intensity ◽  
Industrial Applications ◽  
Lateral Direction ◽  
Critical Speeds ◽  
Vibration Data ◽  
Unbalance Response

Integrally Geared Centrifugal Air Compressors (IGCAC) are becoming popular in many industrial applications. Development of such compressors requires in depth Rotordynamic Design and Analysis. To facilitate this, an in-house computer program based on transfer matrix method was developed using MATLAB® software. This computer program is capable of computing rotordynamic parameters such as static deflection, critical speed and interference diagram, and can output critical speed map, mode shape, unbalance response, orbit, for lateral direction. This software was used to analyze a two stage IGCAC with two impellers on a simply supported rotor running above second critical speed, driven by a two pole induction motor through a step-up gearbox. Undamped critical speed map, an output from the program was used to predict intended bearing stiffness for design. Using the above data and commercially available software DyRoBeS© a suitable bearing was designed. The speed dependent bearing characteristics, an output from DyRoBeS©, were used to determine damped unbalance response plot for a given residual unbalance. Corresponding to a maximum peak in unbalance response the damped critical speed and amplification factors (AF) were found out. The results from the newly developed software were compared with prediction from DyRoBeS©. It was found that critical speed was within 5% and AF was of the same order. Results from in-house software were comparable to that from DyRoBeS©. Based on the guidelines from API 684, the AF and separation margins were determined. A prototype IGCAC compressor as described above was built and tested. The testing included the collection of steady state, coast-up and coast-down data. Using the coast-up, coast-down data, a Bode plot was created. From this the critical speeds and AF’s were determined and compared with results from in-house software. It was found there was an error of less than 5% for the critical speed and around 5% for AF from the predicted results. For the same compressor a study on the potential excitation frequencies due to unbalance, impeller-diffuser and impeller-scroll tongue interactions were calculated. FFT of the steady state vibration data was deduced. It was found that the calculated frequency and measured frequency at maximum amplitude were aligning. Further noise measurements were recorded based on sound intensity as per guidelines in ISO 9614. The impeller-tongue interaction frequencies for stages were seen in the processed noise data. It was found that the predictions were in good agreement with the test results.

scholarly journals Steady-state $$\dot{V}{\text{O}}_{2}$$ above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners

2021 ◽  
Author(s):  
Rebekah J. Nixon ◽  
Sascha H. Kranen ◽  
Anni Vanhatalo ◽  
Andrew M. Jones
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Lactate Concentration ◽  
Practical Interest ◽  
Blood Lactate Concentration ◽  
Distance Runners ◽  
Severe Intensity ◽  
The Stability ◽  
Trained Runners ◽  
Over Time

AbstractThe metabolic boundary separating the heavy-intensity and severe-intensity exercise domains is of scientific and practical interest but there is controversy concerning whether the maximal lactate steady state (MLSS) or critical power (synonymous with critical speed, CS) better represents this boundary. We measured the running speeds at MLSS and CS and investigated their ability to discriminate speeds at which $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 was stable over time from speeds at which a steady-state $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 could not be established. Ten well-trained male distance runners completed 9–12 constant-speed treadmill tests, including 3–5 runs of up to 30-min duration for the assessment of MLSS and at least 4 runs performed to the limit of tolerance for assessment of CS. The running speeds at CS and MLSS were significantly different (16.4 ± 1.3 vs. 15.2 ± 0.9 km/h, respectively; P < 0.001). Blood lactate concentration was higher and increased with time at a speed 0.5 km/h higher than MLSS compared to MLSS (P < 0.01); however, pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 did not change significantly between 10 and 30 min at either MLSS or MLSS + 0.5 km/h. In contrast, $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 increased significantly over time and reached $$\dot{V}{\text{O}}_{2\,\,\max }$$ V ˙ O 2 max at end-exercise at a speed ~ 0.4 km/h above CS (P < 0.05) but remained stable at a speed ~ 0.5 km/h below CS. The stability of $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 at a speed exceeding MLSS suggests that MLSS underestimates the maximal metabolic steady state. These results indicate that CS more closely represents the maximal metabolic steady state when the latter is appropriately defined according to the ability to stabilise pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 .

Development of a Microdevice for Sorting Motile Bacteria

2011 ◽  
Author(s):  
T. Shioiri ◽  
T. Ishikawa ◽  
K. Numayama-Tsuruta ◽  
Y. Imai ◽  
H. Ueno ◽  
...  
Keyword(s):  
Food Production ◽  
Sewage Treatment ◽  
Food Poisoning ◽  
Culture Method ◽  
Industrial Applications ◽  
Colony Count ◽  
Human Intestine ◽  
Count Method ◽  
Long Time ◽  
Time Of Operation

Bacteria are distributed in various places in nature and in industries, examples include human intestine, sewage treatment, food production and even food poisoning. Thus, the separation of bacteria from various samples is an important technique for medical and industrial applications. In recent years, separation of bacteria was commonly performed by a colony count method. This method, however, takes long time of operation and cannot be applied to bacteria for which culture method has not been established.

Initial Investigations Into the Dynamics of Cutting Brushes for Sweeping

2002 ◽  
Vol 124 (4) ◽  
pp. 675-681 ◽  
Author(s):  
G. M. Peel ◽  
G. A. Parker
Keyword(s):  
Steady State ◽  
Centrifugal Force ◽  
Transient Effects ◽  
Test Rig ◽  
Low Speeds ◽  
Discretized Model

Cutting brushes are used at relatively low speeds by various municipal vehicles and in particular road sweeping units. As the name suggests such brushes are designed to “cut” through debris, especially compacted sand or similar matter. The main deflection plane of a bristle (or tine) is along the mount radius, making the tines very stiff in the direction of rotation, hence the cutting action when the brush is rotated. Exploring the literature shows that very little is known, or understood, about the operation of brushes for mechanical sweeping. In this paper a pseudo-static discretized model is developed to investigate the deformations and forces acting on brushes during ideal operation of a horizontal brush on a flat plane. Due to the numerous different sweeper brushes on the market, one common configuration is used as the basis of the model and the paper will detail only the characteristics of this brush. The brush to be investigated is a “cutting brush,” introduced above, where the tines can only deflect along the mount radius. Having developed a model it is used to predict the forces and torques generated within a horizontally rotating brush. The influence of centrifugal force is analyzed although transient effects are neglected and steady state conditions assumed. The predictions of the model are compared to practical results taken from a test rig and the validity of the model is discussed. Agreement between the model and the practical results will be shown to be good, considering the complexities and practical realities involved in analyzing any system which is friction dependent.

A Starved Mixed Elastohydrodynamic Lubrication Model for the Prediction of Lubrication Performance, Friction and Flash Temperature With Arbitrary Entrainment Angle

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Wei Pu ◽  
Dong Zhu ◽  
Jiaxu Wang
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Flash Temperature ◽  
Machined Surface ◽  
Lubrication Performance ◽  
Wide Range ◽  
Starved Lubrication

In this study, a modified mixed lubrication model is developed with consideration of machined surface roughness, arbitrary entraining velocity angle, starvation, and cavitation. Model validation is executed by means of comparison between the obtained numerical results and the available starved elastohydrodynamic lubrication (EHL) data found from some previous studies. A comprehensive analysis for the effect of inlet oil supply condition on starvation and cavitation, mixed EHL characteristics, friction and flash temperature in elliptical contacts is conducted in a wide range of operating conditions. In addition, the influence of roughness orientation on film thickness and friction is discussed under different starved lubrication conditions. Obtained results reveal that inlet starvation leads to an obvious reduction of average film thickness and an increase in interasperity cavitation area due to surface roughness, which results in significant increment of asperity contacts, friction, and flash temperature. Besides, the effect of entrainment angle on film thickness will be weakened if the two surfaces operate under starved lubrication condition. Furthermore, the results show that the transverse roughness may yield thicker EHL films and lower friction than the isotropic and longitudinal if starvation is taken into account. Therefore, the starved mixed EHL model can be considered as a useful engineering tool for industrial applications.

Super-Fine Structure in the Critical Flow-Rate of Critical Flow Venturi Nozzles

2002 ◽  
Author(s):  
Masahiro Ishibashi
Keyword(s):  
Fine Structure ◽  
Steady State ◽  
Discharge Coefficient ◽  
Constant Pressure ◽  
Pressure Ratio ◽  
Critical Flow ◽  
Time Intervals ◽  
Critical Flow Rate ◽  
A Value ◽  
Long Time

It is shown that critical flow Venturi nozzles need time intervals, i.e., more than five hours, to achieve steady state conditions. During these intervals, the discharge coefficient varies gradually to reach a value inherent to the pressure ratio applied. When a nozzle is suddenly put in the critical condition, its discharge coefficient is trapped at a certain value then afterwards approaches gradually to the inherent value. Primary calibrations are considered to have measured the trapped discharge coefficient, whereas nozzles in applications, where a constant pressure ratio is applied for a long time, have a discharge coefficient inherent to the pressure ratio; inherent and trapped coefficients can differ by 0.03–0.04%.

Steady State Engine Test Demonstration of Performance Improvement With an Advanced Turbocharger

2013 ◽  
Author(s):  
Harold Sun ◽  
Dave Hanna ◽  
Liangjun Hu ◽  
Eric Curtis ◽  
James Yi ◽  
...  
Keyword(s):  
Steady State ◽  
Performance Improvement ◽  
High Efficiency ◽  
Combustion Engine ◽  
Load Condition ◽  
Department Of Energy ◽  
Speed Ratio ◽  
Mixed Flow ◽  
Turbine Wheel ◽  
Low Speed

Heavy EGR required on diesel engines for future emission regulation compliance has posed a big challenge to conventional turbocharger technology for high efficiency and wide operation range. This study, as part of the U.S. Department of Energy sponsored research program, is focused on advanced turbocharger technologies that can improve turbocharger efficiency on customer driving cycles while extending the operation range significantly, compared to a production turbocharger. The production turbocharger for a medium-duty truck application was selected as a donor turbo. Design optimizations were focused on the compressor impeller and turbine wheel. On the compressor side, advanced impeller design with arbitrary surface can improve the efficiency and surge margin at low end while extending the flow capacity, while a so-called active casing treatment can provide additional operation range extension without compromising compressor efficiency. On the turbine side, mixed flow turbine technology was revisited with renewed interest due to its performance characteristics, i.e. high efficiency at low-speed ratio, relative to the base conventional radial flow turbine, which is relevant to heavy EGR operation for future diesel applications. The engine dynamometer test shows that the advanced turbocharger technology enables over 3% BSFC improvement at part-load as well as full-load condition, in addition to an increase in rated power. The performance improvement demonstrated on engine dynamometer seems to be more than what would typically be translated from the turbocharger flow bench data, indicating that mixed flow turbine may provide additional performance benefits under pulsed exhaust flow on an internal combustion engine and in the low-speed ratio areas that are typically not covered by steady state flow bench tests.

scholarly journals Noncontacting Torquemeters Utilizing Magneto-Elastic Properties of Steel Shafts

1969 ◽  
Author(s):  
Egil Angeid
Keyword(s):  
Elastic Property ◽  
Gas Turbine ◽  
Elastic Properties ◽  
Industrial Applications ◽  
Low Speed

The magneto-elastic property of steel shafts makes noncontacting torquementers possible. Early magneto-elastic torquemeters suffered from excessive sensitivity to variations in airgap and shaft temperature. These drawbacks have been eliminated in the Torductor® torquemeter, which has been very successful in low-speed industrial applications. In gas turbine applications, some special problems are encountered. These problems, and ways to minimize them, are discussed.

scholarly journals A theoretical verification of the integral fluctuation theorem for accelerated colloidal systems in the long-time limit

2021 ◽  
Author(s):  
Yash Lokare
Keyword(s):  
Steady State ◽  
Time Scales ◽  
Numerical Study ◽  
Quantitative Description ◽  
Experimental Studies ◽  
Fluctuation Theorem ◽  
Nonequilibrium Steady States ◽  
Small Scale ◽  
Colloidal Systems ◽  
Long Time

A quantitative description of the violation of the second law of thermodynamics in relatively small classical systems and over short time scales comes from the fluctuation-dissipation theorem. It has been well established both theoretically and experimentally, the validity of the fluctuation theorem to small scale systems that are disturbed from their initial equilibrium states. Some experimental studies in the past have also explored the validity of the fluctuation theorem to nonequilibrium steady states at long time scales in the asymptotic limit. To this end, a theoretical and/or purely numerical model of the integral fluctuation theorem has been presented. An approximate general expression for the dissipation function has been derived for accelerated colloidal systems trapped/confined in power-law traps. Thereafter, a colloidal particle trapped in a harmonic potential (generated by an accelerating one-dimensional optical trap) and undergoing Brownian motion has been considered for the numerical study. A toy model of a quartic potential trap in addition to the harmonic trap has also been considered for the numerical study. The results presented herein show that the integral fluctuation theorem applies not only to equilibrium steady state distributions but also to nonequilibrium steady state distributions of colloidal systems in accelerated frames of reference over long time scales.

TRANSMITTING BIPARTITE AND MULTIPARTITE CORRELATIONS VIA SPIN CHAINS UNDER PHASE DECOHERENCE

2012 ◽  
Vol 10 (06) ◽  
pp. 1250073
Author(s):  
JIAN-FENG AI ◽  
JIAN-SONG ZHANG ◽  
AI-XI CHEN
Keyword(s):  
Steady State ◽  
Anisotropy Parameter ◽  
Quantum Correlations ◽  
Spin Chains ◽  
The Other ◽  
Bipartite Entanglement ◽  
Other Hand ◽  
Long Time ◽  
Phase Decoherence ◽  
The One

We investigate the transfer of bipartite (measured by cocurrence) and multipartite (measured by global discord) quantum correlations though spin chains under phase decoherence. The influence of phase decoherence and anisotropy parameter upon quantum correlations transfer is investigated. On the one hand, in the case of no phase decoherence, there is no steady state quantum correlations between spins. On the other hand, if the phase decoherence is larger than zero, the bipartite quantum correlations can be transferred through a Heisenberg XXX chain for a long time and there is steady state bipartite entanglement. For a Heisenberg XX chain, bipartite entanglement between two spins is destroyed completely after a long time. Multipartite quantum correlations of all spins are more robust than bipartite quantum correlations. Thus, one can store multipartite quantum correlations in spin chains for a long time under phase decoherence.

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