In order to more accurately predict the contact fatigue life of rolling bearing, a prediction method of fatigue life of rolling bearing is proposed based on elastohydrodynamic lubrication （EHL）, the 3-paameter Weibu...In order to more accurately predict the contact fatigue life of rolling bearing, a prediction method of fatigue life of rolling bearing is proposed based on elastohydrodynamic lubrication （EHL）, the 3-paameter Weibull distribution ad fatigue strength. First,the contact stress considering elliptical EHL is obtained by mapping film pressure onto the Hertz zone. Then,the basic strength model of rolling bearing based on the 3-parameter Weibull distribution is deduced by the series connection reliability theory. Considering the effect of the type of stress, variation of shape and fuctuation of load, the mathematical models of the 尸 -tS-TV curve of the minimum life and the characteristic life for rolling bearing are established, respectively, and thus the prediction model of fatigue life of rolling bearing based on the 3-paameter Weibull distribution and fatigue strength is further deduced. Finally, the contact fatigue life obtained by the proposed method ad the latest international standard （IS0281： 2007） about the fatigue life prediction of rolling bearing are compared with those obtained by the statistical method. Results show that the proposed prediction method is effective and its relative error is smaier than that of the latest international standard （IS0281： 2007） with reliability R 〉 0. 93.展开更多
In order to research how the size of the ink flow channel is affected by the interaction of adjacent ink areas,according to the method of fluid-solid interaction,this paper analyzes the size of the ink flow channel of...In order to research how the size of the ink flow channel is affected by the interaction of adjacent ink areas,according to the method of fluid-solid interaction,this paper analyzes the size of the ink flow channel of two ink rollers' rotation.Firstly,this paper simulates the situation of only one ink area.Secondly,this paper simulates the situation of five adjacent ink areas.Then,through comparing the simulation results of two above situations,it' s obvious that the interaction of adjacent ink areas has big effects on the ink pressure and the size of ink flow channel.At last,this paper gets the main factor that affects the size of ink flow channel in the different situations.展开更多
Circulating leukocytes in trafficking to the inflammatory sites, will be first tether to, and then roll on the vascular surface. This event is mediated through specific interaction of P-selectin and P-selectin glycopr...Circulating leukocytes in trafficking to the inflammatory sites, will be first tether to, and then roll on the vascular surface. This event is mediated through specific interaction of P-selectin and P-selectin glycoprotein ligand-1 （PSGL-1）, and regulated by hemodynamics. Poor data were reported in understanding P-selectin-mediated rolling. With the flow chamber technique, we herein observed HL-60 cell rolling on P-selectin with or without 3% Ficoll at various wall shear stresses from 0.05 to 0.4 dyn/cm：. The results demonstrated that force rather than transport regulated the rolling, similar to rolling on L- and E-selectin. The rolling was accelerated quickly by an increasing force below the optimal shear threshold of 0.15 dyn/cm2 first and then followed by a slowly decelerating phase starting at the optimum, showing a catch-slip transition and serving as a mechanism for the rolling. The catch-slip transition was completely reflected to the tether lifetime and other rolling parameters, such as the mean and fractional stop time. The narrow catch bond regime stabilized the rolling quickly, through steeply increasing frac- tional stop time to a plateau of about 0.85. Data presented here suggest that the low shear stress threshold serves as a mecha- nism for most cell rolling events through P-selectin.展开更多
The leakage research on supercritical carbon dioxide fluid in rolling piston expander was investigated experimentally.Using expander instead of throttle valve is an important way to improve the efficiency of carbon di...The leakage research on supercritical carbon dioxide fluid in rolling piston expander was investigated experimentally.Using expander instead of throttle valve is an important way to improve the efficiency of carbon dioxide refrigeration system.However,the supercritical fluid leakage in expander is serious and is the main factor affecting the expander's efficiency.This paper presented and compared four classic leakage models.The analysis indicated that laminar leakage model is suitable in leakage simulation of expander.A leakage test system,including the leakage test part which has two types of leakage specimens with different gaps ranging from 5 to 15 m,was established.The experimental results indicated that lubricant film played an important role.When the leakage clearance of cylindrical specimen was 5 m,the mass flow rate of leakage was about 0.88 g s-1.The data was 3.638 g s-1 with leakage clearance being 10 m and 7.11g s-1 with leakage clearance being 15 m.A modified leakage model was developed,whose average deviation was within 10% compared with the experimental data.At last,this paper simulated the leakage in rolling piston expander presented by Tian et al.(2010).The leakage between rolling piston and cylinder was the most serious part with the value up to 0.04 kg s-1.展开更多
The patterns of wing rock motion at 52.5° angle of attack have already been investigated in detail （Rong, 2009; Wang, 2010）. These patterns are completely different from those at other angles of attack. This ph...The patterns of wing rock motion at 52.5° angle of attack have already been investigated in detail （Rong, 2009; Wang, 2010）. These patterns are completely different from those at other angles of attack. This phenomenon indicates that angle of attack affects wing rock motion. The present study alms to examine the different patterns of wing rock motion at different angles of attack. The flow mechanisms of the motion patterns are also revealed, especially the uncommanded lateral motions, including wing rock and lateral deflection, induced by regular asymmetric separated flow from wings at low angles of attack and fore- body asymmetric vortices at angles of attack of 27.5°〈 α 〈 70°. The test conditions, including the testing Reynolds number, wind tunnel, experimental techniques, and test model, are all the same as those used in a previous study at a = 52.5°. Finally, the experimental technique of rotating nose of the model to suppress the wing rock or lateral deflection, which is induced by forebody asymmetric vortex flow, is applied. The uncommanded lateral motions are successfully suppressed by this technique.展开更多
Wide validation of self-developed program of natural circulation under oceanic conditions has been conducted compared with experimental data of inclination,zero-power condition and hot-state condition.Experiments were...Wide validation of self-developed program of natural circulation under oceanic conditions has been conducted compared with experimental data of inclination,zero-power condition and hot-state condition.Experiments were performed on a full-scale,whole parameterization natural circulation loop designed with reference to 5 MW experimental low temperature nuclear heating reactor(NHR)of Tsinghua University.Investigation of natural circulation and parameter effect under heaving motion was carried out using the program and comparison of heaving,inclination and rolling on natural circulation respectively to reveal the influence mechanism.Results indicate that:(1)significant influence of heaving motion on natural circulation was observed,and heaving motion with high level of strength and long cycle would lead to severe flow fluctuation;(2)slight effect was caused by short cycle heaving motion which was completely different from long cycle heaving motion;(3)comprehensive action of alternating force and flow density distribution would result in natural circulation under heaving motion;(4)most severe accidents maybe result from the long cycle heaving motion rather than inclination and rolling motion.Investigation of influence of heaving motion on natural circulation could have important reference significance in the optimization design of nuclear reactors.展开更多
The static rolling aerodynamics of a finned slender body is numerically studied in this paper.Simulation results show a nonlinear uprising of the rolling moment when the angle of attack is greater than 20°in subs...The static rolling aerodynamics of a finned slender body is numerically studied in this paper.Simulation results show a nonlinear uprising of the rolling moment when the angle of attack is greater than 20°in subsonic flows.Asymmetric vortex break down phenomenon on the"horizontal"rudders is found to be responsible for this phenomenon.By introducing the geometric-equivalent angle of attack and geometric-equivalent sweep angle,the cause of the nonlinear rolling moment characteristics can be explained by the delta wing vortex breakdown analysis.展开更多
基金The National Defense Advance Research Program(No.81302XXX)
文摘In order to more accurately predict the contact fatigue life of rolling bearing, a prediction method of fatigue life of rolling bearing is proposed based on elastohydrodynamic lubrication （EHL）, the 3-paameter Weibull distribution ad fatigue strength. First,the contact stress considering elliptical EHL is obtained by mapping film pressure onto the Hertz zone. Then,the basic strength model of rolling bearing based on the 3-parameter Weibull distribution is deduced by the series connection reliability theory. Considering the effect of the type of stress, variation of shape and fuctuation of load, the mathematical models of the 尸 -tS-TV curve of the minimum life and the characteristic life for rolling bearing are established, respectively, and thus the prediction model of fatigue life of rolling bearing based on the 3-paameter Weibull distribution and fatigue strength is further deduced. Finally, the contact fatigue life obtained by the proposed method ad the latest international standard （IS0281： 2007） about the fatigue life prediction of rolling bearing are compared with those obtained by the statistical method. Results show that the proposed prediction method is effective and its relative error is smaier than that of the latest international standard （IS0281： 2007） with reliability R 〉 0. 93.
基金Supported by the National Natural Science Foundation of China(No.51105009)the National Science and Technology Support Program(No.2012BAF13B05)
文摘In order to research how the size of the ink flow channel is affected by the interaction of adjacent ink areas,according to the method of fluid-solid interaction,this paper analyzes the size of the ink flow channel of two ink rollers' rotation.Firstly,this paper simulates the situation of only one ink area.Secondly,this paper simulates the situation of five adjacent ink areas.Then,through comparing the simulation results of two above situations,it' s obvious that the interaction of adjacent ink areas has big effects on the ink pressure and the size of ink flow channel.At last,this paper gets the main factor that affects the size of ink flow channel in the different situations.
基金supported by the National Natural Science Foundation of China(Grant Nos.11272125,11072080,31170887 and 31200705)Guangdong Natural Science Foundation(Grant No.S2011010005451)Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20110172110030)
文摘Circulating leukocytes in trafficking to the inflammatory sites, will be first tether to, and then roll on the vascular surface. This event is mediated through specific interaction of P-selectin and P-selectin glycoprotein ligand-1 （PSGL-1）, and regulated by hemodynamics. Poor data were reported in understanding P-selectin-mediated rolling. With the flow chamber technique, we herein observed HL-60 cell rolling on P-selectin with or without 3% Ficoll at various wall shear stresses from 0.05 to 0.4 dyn/cm：. The results demonstrated that force rather than transport regulated the rolling, similar to rolling on L- and E-selectin. The rolling was accelerated quickly by an increasing force below the optimal shear threshold of 0.15 dyn/cm2 first and then followed by a slowly decelerating phase starting at the optimum, showing a catch-slip transition and serving as a mechanism for the rolling. The catch-slip transition was completely reflected to the tether lifetime and other rolling parameters, such as the mean and fractional stop time. The narrow catch bond regime stabilized the rolling quickly, through steeply increasing frac- tional stop time to a plateau of about 0.85. Data presented here suggest that the low shear stress threshold serves as a mecha- nism for most cell rolling events through P-selectin.
基金supported by the National Natural Science Foundation of China (Grant No. 50676064)
文摘The leakage research on supercritical carbon dioxide fluid in rolling piston expander was investigated experimentally.Using expander instead of throttle valve is an important way to improve the efficiency of carbon dioxide refrigeration system.However,the supercritical fluid leakage in expander is serious and is the main factor affecting the expander's efficiency.This paper presented and compared four classic leakage models.The analysis indicated that laminar leakage model is suitable in leakage simulation of expander.A leakage test system,including the leakage test part which has two types of leakage specimens with different gaps ranging from 5 to 15 m,was established.The experimental results indicated that lubricant film played an important role.When the leakage clearance of cylindrical specimen was 5 m,the mass flow rate of leakage was about 0.88 g s-1.The data was 3.638 g s-1 with leakage clearance being 10 m and 7.11g s-1 with leakage clearance being 15 m.A modified leakage model was developed,whose average deviation was within 10% compared with the experimental data.At last,this paper simulated the leakage in rolling piston expander presented by Tian et al.(2010).The leakage between rolling piston and cylinder was the most serious part with the value up to 0.04 kg s-1.
基金supported by the National Natural Science Foundation of China(Grant Nos.11172030 and 11102012)
文摘The patterns of wing rock motion at 52.5° angle of attack have already been investigated in detail （Rong, 2009; Wang, 2010）. These patterns are completely different from those at other angles of attack. This phenomenon indicates that angle of attack affects wing rock motion. The present study alms to examine the different patterns of wing rock motion at different angles of attack. The flow mechanisms of the motion patterns are also revealed, especially the uncommanded lateral motions, including wing rock and lateral deflection, induced by regular asymmetric separated flow from wings at low angles of attack and fore- body asymmetric vortices at angles of attack of 27.5°〈 α 〈 70°. The test conditions, including the testing Reynolds number, wind tunnel, experimental techniques, and test model, are all the same as those used in a previous study at a = 52.5°. Finally, the experimental technique of rotating nose of the model to suppress the wing rock or lateral deflection, which is induced by forebody asymmetric vortex flow, is applied. The uncommanded lateral motions are successfully suppressed by this technique.
基金supported by the National Science and Technology Major Project(Grant No.ZX06901)the National Natural Science Foundation of China(Grant No.11072131)
文摘Wide validation of self-developed program of natural circulation under oceanic conditions has been conducted compared with experimental data of inclination,zero-power condition and hot-state condition.Experiments were performed on a full-scale,whole parameterization natural circulation loop designed with reference to 5 MW experimental low temperature nuclear heating reactor(NHR)of Tsinghua University.Investigation of natural circulation and parameter effect under heaving motion was carried out using the program and comparison of heaving,inclination and rolling on natural circulation respectively to reveal the influence mechanism.Results indicate that:(1)significant influence of heaving motion on natural circulation was observed,and heaving motion with high level of strength and long cycle would lead to severe flow fluctuation;(2)slight effect was caused by short cycle heaving motion which was completely different from long cycle heaving motion;(3)comprehensive action of alternating force and flow density distribution would result in natural circulation under heaving motion;(4)most severe accidents maybe result from the long cycle heaving motion rather than inclination and rolling motion.Investigation of influence of heaving motion on natural circulation could have important reference significance in the optimization design of nuclear reactors.
基金supported by the National Key Basic Research Program of China(Grant No.2014CB744801)the National Natural Science Foundation of China(Grant Nos.11102098 and 11372160)
文摘The static rolling aerodynamics of a finned slender body is numerically studied in this paper.Simulation results show a nonlinear uprising of the rolling moment when the angle of attack is greater than 20°in subsonic flows.Asymmetric vortex break down phenomenon on the"horizontal"rudders is found to be responsible for this phenomenon.By introducing the geometric-equivalent angle of attack and geometric-equivalent sweep angle,the cause of the nonlinear rolling moment characteristics can be explained by the delta wing vortex breakdown analysis.
