Model for the prediction of drag torque characteristics in wet clutch with radial grooves

2018 ◽  
Vol 233 (12) ◽  
pp. 3043-3056 ◽  
Author(s):  
Lin Zhang ◽  
Chao Wei ◽  
Ji Bin Hu
Keyword(s):  
Flow Rate ◽  
Rotational Speed ◽  
Heat Dissipation ◽  
Maximum Speed ◽  
Drag Torque ◽  
Cross Sectional ◽  
Oil Film ◽  
Oil Supply ◽  
Wet Clutch ◽  
Film Lubrication

Drag torque can cut down the efficiency of the vehicle transmission system. So it should be reduced on the premise of normal vehicle lubrication and heat dissipation. The purpose of this paper is to analyze the variation rule of drag torque in single-plate wet clutch from the perspective of flow rate, density, and viscosity. In the theoretical model of drag torque, the flow field is divided into oil film area and cavitation zone. Based on the mass flow conservation and viscosity–pressure equation, the equivalent density and viscosity of each node in each region are obtained. Then the total drag torque is calculated through the sum of each node’s torque. Finally, the curves of drag torque with rotational speed under different working conditions are obtained by numerical calculation, and they have been tested and verified. Through this research, the following conclusions can be reached: the rotational speed of the peak of drag torque is near the maximum speed where full oil film lubrication is realized. While temperature declines, it will lead to higher viscosity, then the speed of the lubricant along the radial direction will decrease, resulting in the increase in maximum speed of full oil film lubrication under the same oil supply; accordingly, the peak of drag torque will rise. If the flow rate of oil supply is increased, the maximum speed where full oil film lubrication is realized will be higher; consequently, the maximum drag torque will be improved. When clearance becomes wider, the cross-sectional area of the radial flow will be larger, then the maximum speed of full oil film lubrication under the same oil supply will be decreased, thus the peak of drag torque will decline.

Simulation and experimental study on the influence of oil groove structure on the drag torque of the wet clutch

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Chengjun Wang ◽  
Wujian Ding ◽  
Xudong Zheng ◽  
Haiqiang Zhu ◽  
Zuzhi Tian ◽  
...  
Keyword(s):  
Heat Dissipation ◽  
Simulation Analysis ◽  
Three Dimensional ◽  
Reference Object ◽  
Drag Torque ◽  
Content Type ◽  
Oil Film ◽  
Wet Clutch ◽  
Groove Structure ◽  
Dimensional Simulation

Purpose This paper aims to design a single and double throat oil groove structure, which can reduce the drag torque of the wet clutch. Design/methodology/approach A three-dimensional simulation model was established herein using the computational fluid dynamics method. The influence of oil groove structure on the oil film flow field and the drag torque is obtained by a simulation. Findings Compared with the traditional radial oil groove, the results show that the single throat oil groove structure reduces the drag torque by about 24.59%; the double throat oil groove reduces the drag torque by about 47.27%. As the speed difference increases, the average temperature rise of the oil film of the double throat oil groove is 4°C lower than that of the single throat oil groove, indicating that it has good heat dissipation performance. The analysis results were verified by experimental results. Originality/value In this paper, the radial oil groove is taken as the reference object, and the structure of the oil groove is designed and improved. The simulation analysis and experiment verify the rule of the influence of the oil groove structure on the drag torque, which provides a new design idea for reducing the drag torque of wet clutch.

scholarly journals Ligament and Droplet Generation by Oil Film on a Rotating Disk

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Hengchao Sun ◽  
Guoding Chen ◽  
Li’na Wang ◽  
Fei Wang
Keyword(s):  
Film Thickness ◽  
Flow Rate ◽  
Rotational Speed ◽  
Two Phase Flow ◽  
Rotating Disk ◽  
Droplet Generation ◽  
Phase Flow ◽  
Two Phase ◽  
Disk Radius ◽  
Oil Film

The lubrication and heat transfer designs of bearing chamber depend on an understanding of oil/air two-phase flow. As initial and boundary conditions, the characteristics of ligament and droplet generation by oil film on rotating parts have significant influence on the feasibility of oil/air two-phase flow analysis. An integrated model to predict the oil film flow, ligament number, and droplet Sauter mean diameter (SMD) of a rotating disk, which is an abstraction of the droplet generation sources in a bearing chamber, is developed based on the oil film force balance analysis and wave theory. The oil film thickness and velocity, ligaments number, and droplet SMD are calculated as functions of the rotating disk radius, rotational speed and oil volume flow rate and oil properties. The theoretical results show that the oil film thickness and SMD are decreased with an increasing rotational speed, while the radial, transverse velocities, and ligament number are increased. The oil film thickness, radial velocity, and SMD are increased with an increasing oil flow rate, but the transverse velocity and ligament number are decreased. A test facility is built for the investigation into the ligament number of a rotating disk, and the measurement of ligament number is carried out by means of a high speed photography.

Particle Image Velocimetry As Applied to Inlet Flow Field of a Turbocharger Compressor at Varying Rotational Speeds With Emphasis on Surge

2020 ◽  
Author(s):  
Deb Banerjee ◽  
Rick Dehner ◽  
Ahmet Selamet ◽  
Keith Miazgowicz
Keyword(s):  
Flow Field ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
Particle Image ◽  
Reversed Flow ◽  
Cross Sectional ◽  
Image Velocimetry ◽  
Compressor Map ◽  
Cross Sectional Average

Abstract Turbocharger surge remains an area of concern for the automotive industry as it limits the permissible operating range on the compressor map, while also adversely impacting the compressor’s pressure rise, efficiency, and acoustics. The present study uses Stereoscopic Particle Image Velocimetry (SPIV) to investigate the flow field at the inlet of an automotive turbocharger compressor without a recirculating channel. Experiments were carried out at four different speeds, including 80, 100, 120, and 140 krpm, which represent a substantial portion of the compressor map. The mass flow rates investigated ranged from choke to deep surge, thus spanning the entire mass flow regime at each rotational speed. The current work aims to characterize how the compressor inlet velocity field varies with rotational speed, with a specific emphasis on surge. The qualitative nature of the flow field (radial dependence of axial and tangential velocity profiles), over the choke to mild surge range, was observed to be nearly independent of rotational speed for comparable operating conditions (for example, comparison of mild surge at different rotational speeds). A quantitative comparison of the velocity profiles at the choke or mild surge operating points showed an increase in the velocity magnitudes with increasing rotational speed. The flow field at deep surge, however, was observed to change substantially from 80 krpm to 140 krpm. At 80 krpm, the character of the flow field at different times (at different points on the surge cycle) was observed to be similar: the core flow near the center of the duct was always directed into the impeller, whereas the reversed flow occupied an annular region near the periphery in nearly all time instances. However, as the rotational speed was increased to 140 krpm, the variation in the flow field at different instances within a deep surge cycle increased. At 140 krpm, the negative flow rate (where the cross-sectional average flow is directed out of the inducer back into the inlet duct) portion of the surge cycle was still similar to the overall surge flow field at 80 krpm, but over a substantial part of the positive flow rate (cross-sectional average flow is directed into the impeller) portion of the surge cycle, there was no sign of reversed flow within the visualization domain. As the rotational speed was increased, the surge loop (obtained by combining the PIV and pressure transducer data) extended over a wider portion of the compressor map with higher maximum (positive) and minimum (negative) flow rates, along with higher amplitude pressure fluctuations. The mean amplitude of mass flow rate and pressure ratio fluctuations at deep surge increased in nearly a quadratic fashion with rotational speed. The deep surge frequency did not change substantially over the range of rotational speeds examined in this study.

Impact of Rotational Speed on Turbocharger Compressor Surge Through Particle Image Velocimetry1

2021 ◽  
Vol 143 (6) ◽  
Author(s):  
Deb Banerjee ◽  
Rick Dehner ◽  
Ahmet Selamet ◽  
Keith Miazgowicz
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Flow Rate ◽  
Rotational Speed ◽  
Particle Image ◽  
Reversed Flow ◽  
Cross Sectional ◽  
Average Flow ◽  
Image Velocimetry ◽  
Cross Sectional Average

Abstract Stereoscopic particle image velocimetry is used to characterize the variation of the turbocharger compressor inlet velocity field as a function of rotational speed, with an emphasis on surge. While the velocity magnitudes at choke or mild surge increased with rotational speed, the velocity profiles remained qualitatively similar. The variation in deep surge flow field with shaft speed, however, was more substantial. At 80 krpm, the overall flow field was comparable at different time instances (at different points on the surge cycle): the core flow near the duct center was always directed into the impeller, whereas reversed flow occupied an annular region near the periphery in nearly all time instances. However, at 140 krpm, while the negative flow rate (cross-sectional average flow is directed out of the inducer back into the inlet duct) portion of the surge cycle was still similar to the overall surge flow field at 80 krpm, over a substantial part of the positive flow rate (cross-sectional average flow is directed into the impeller) portion of the surge cycle, there was no sign of reversed flow within the visualization domain. As the rotational speed was increased, the surge loop (obtained by combining the particle image velocimetry (PIV) and pressure transducer data) extended over a wider portion of the compressor map with higher maximum (positive) and minimum (negative) flow rates, along with higher amplitude pressure fluctuations. The mean amplitude of mass flow rate and pressure ratio fluctuations at deep surge increased in nearly a quadratic fashion with rotational speed.

scholarly journals Correlation between peak expiratory flow rate and pectoralis muscle length

2020 ◽  
Vol 8 (10) ◽  
pp. 3643
Author(s):  
Visalakshi H. Subramanian ◽  
Aruna Chennakeshawaran ◽  
Vijay Krishna Kumar
Keyword(s):  
Peak Expiratory Flow ◽  
Flow Rate ◽  
Peak Expiratory Flow Rate ◽  
Muscle Length ◽  
Pectoralis Major ◽  
Maximum Speed ◽  
Pectoralis Muscle ◽  
Cross Sectional ◽  
Expiratory Flow ◽  
Major General

Background: Peak expiratory flow rate (PEFR) is a measure of the maximum speed of exhalation after a deep inspiration. The peak expiratory flow is measured by a device named peak flow meter. This study concentrates on the correlation of the PEFR with the pectoral muscle length.Methods: It is a cross sectional study of 30 convenient samples based on gender distribution where the PEFR and pectoralis muscle length were measured in the subjects.Results: Statistical analysis shows that there is a significant correlation between right pectoralis major general muscle length and PEFR (p=0.030), left pectoralis major general muscle length and PEFR (p=0.014), right pectoralis major clavicular end muscle length with PEFR (p=0.010).Conclusions: There is a significant correlation between peak expiratory flow and pectoralis muscle length. 

Numerical Simulation of Lubrication System in a Hermetic Reciprocating Compressor

2014 ◽  
Author(s):  
Mustafa Ozsipahi ◽  
Sertac Cadirci ◽  
Hasan Gunes ◽  
Kemal Sarioglu ◽  
Husnu Kerpicci
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
Numerical Study ◽  
Lubrication System ◽  
Reciprocating Compressor ◽  
Oil Viscosity ◽  
Two Phase ◽  
Oil Film

The aim of this numerical study is to investigate the lubrication system of a household hermetic reciprocating compressor. The effects of the rotational speed, oil viscosity and crankshaft-to-oil sump bottom distance on the oil-air two phase flows are investigated in detail. Necessary oil to lubricate the components of the compressor is sucked from the oil sump through an asymmetrically opened suction hole of the crankshaft by its rotational movement and climbs as an oil film on the helical channel carved on the shaft wall. This oil film is directed to crankshaft outlet. The oil forms an immiscible mixture with air, thus a two phase flow model should be analyzed using Volume of Fluid (VoF) method in the flow solver. Main findings related to the oil mass flow rate released from the crankshaft outlet reveal that with increasing rotational speed, the mass flow rate from the crankshaft outlet also increases, but with increasing viscosity and decreasing crankshaft-to-oil sump bottom distance, the oil mass flow rate decreases.

scholarly journals A Numerical Study of Sub-Millisecond Integrated Mix-and-Inject Microfluidic Devices for Sample Delivery at Synchrotron and XFELs

2021 ◽  
Vol 11 (8) ◽  
pp. 3404
Author(s):  
Majid Hejazian ◽  
Eugeniu Balaur ◽  
Brian Abbey
Keyword(s):  
Molecular Dynamics ◽  
Flow Rate ◽  
Numerical Study ◽  
Three Dimensional ◽  
Microfluidic Devices ◽  
Liquid Jets ◽  
Mixing Efficiency ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Time Required

Microfluidic devices which integrate both rapid mixing and liquid jetting for sample delivery are an emerging solution for studying molecular dynamics via X-ray diffraction. Here we use finite element modelling to investigate the efficiency and time-resolution achievable using microfluidic mixers within the parameter range required for producing stable liquid jets. Three-dimensional simulations, validated by experimental data, are used to determine the velocity and concentration distribution within these devices. The results show that by adopting a serpentine geometry, it is possible to induce chaotic mixing, which effectively reduces the time required to achieve a homogeneous mixture for sample delivery. Further, we investigate the effect of flow rate and the mixer microchannel size on the mixing efficiency and minimum time required for complete mixing of the two solutions whilst maintaining a stable jet. In general, we find that the smaller the cross-sectional area of the mixer microchannel, the shorter the time needed to achieve homogeneous mixing for a given flow rate. The results of these simulations will form the basis for optimised designs enabling the study of molecular dynamics occurring on millisecond timescales using integrated mix-and-inject microfluidic devices.

scholarly journals Study of Injection Method for Maximizing Oil-Cooling Performance of Electric Vehicle Motor with Hairpin Winding

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 747
Author(s):  
Taewook Ha ◽  
Dong Kyu Kim
Keyword(s):  
Electric Vehicle ◽  
Flow Rate ◽  
Film Formation ◽  
Formation Rate ◽  
Cooling Performance ◽  
Oil Film ◽  
Injection Method ◽  
Cooling Method ◽  
Oil Flow ◽  
Oil Injection

The oil injection method was studied to maximize the cooling performance of an electric vehicle motor with a hairpin winding. The cooling performance of the motor using the oil cooling method is proportional to the contact area of the oil and the coil. A numerical analysis was conducted to examine the effect of the spray nozzle type on the oil flow. The dripping nozzle forms the thickest oil film on the coil, making it the most effective for cooling of hairpin-type motors. Subsequently, an experimental study was conducted to optimize the nozzle diameter and number of nozzles. When the inlet diameter and number was 6.35 mm and 6, the oil film formation rate was 53%, yielding the most uniform oil film. Next, an experiment was performed to investigate the effects of the oil temperature and flow rate on the oil flow. The oil film formation rate was the highest (83%) when the oil temperature was 40 °C and the flow rate was 6 LPM.

scholarly journals Salivary flow rate and the risk of cognitive impairment among Korean elders: a cross-sectional study

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Minh-Tung Do ◽  
Huong Vu ◽  
Jong-Koo Lee ◽  
Sang-Min Park ◽  
Joung-Sik Son ◽  
...  
Keyword(s):  
Cognitive Impairment ◽  
Flow Rate ◽  
Salivary Flow ◽  
Cross Sectional Study ◽  
Community Dwelling ◽  
Salivary Flow Rate ◽  
Multivariable Logistic Regression Analysis ◽  
Sectional Study ◽  
Cross Sectional ◽  
Denture Status

Abstract Background Salivary function has been suggested to be associated with cognitive impairment. However, the effect of salivary flow rate (SFR) on cognitive impairment remains unclear. This study aimed to investigate whether SFR is associated with cognitive impairment among Korean elders. Methods This cross-sectional study included 649 elders aged 65 and older in the Korean community-dwelling population. Cognitive impairment was assessed using the Mini-Mental Status Examination. Unstimulated SFR was measured and dichotomized. Denture status, age, sex, education level, smoking, drinking, diabetes, hypertension, and obesity were considered confounders. Multivariable logistic regression analysis was applied to assess the adjusted association. Stratified analysis by sex and denture status was performed to clarify the effect modification. Results Participants without cognitive impairment showed a higher SFR level than those with cognitive impairment (0.81 mL/min for non-cognitive impairment versus 0.52 mL/min for cognitive impairment, p < 0.001). After controlling for confounders, participants with low SFR (< 0.3 mL/min) were more likely to have cognitive impairment by 1.5 times than participants with normal SFR (odds ratio [OR] = 1.5, confidence interval [CI] = 1.05–2.10). The association of low SFR with cognitive impairment was higher in women and dentate participants: about 10% higher in women (OR = 1.63, CI = 1.07–2.50) and about 22% higher in dentate participants (OR = 1.82, CI = 1.41–2.90). Conclusions Salivary flow rate is independently associated with cognitive impairment among Korean elders. The association was modified in females and dentate elders. Physicians and dentists should consider low SFR and cognitive impairment as a risk factor between them in clinics.

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