In the present study,hydraulic and thermal behavior of an automatic transmission nano-fluid(ATNF) inside a tube with a twisted tape has been investigated.The heat transfer improvement and pressure drop of transmission...In the present study,hydraulic and thermal behavior of an automatic transmission nano-fluid(ATNF) inside a tube with a twisted tape has been investigated.The heat transfer improvement and pressure drop of transmission oil for each of case of using twisted tape and nano-particles were also examined separately and compared with each other.The Cu O nano-particles were used to prepare the ATNF.The effects of different Reynolds numbers and different mass fractions of nano-particle were investigated.The results showed that applying nano-particles and twisted tape simultaneously increases both the pressure drop and Nusselt number,on average by about 53% and 76%,respectively.By using a parameter,namely thermal performance index η,the effect of increasing heat transfer and pressure drop was studied simultaneously.The heat transfer improvement predominates the pressure drop increment in all cases.It was observed that the highest thermal performance of 1.9 was obtained at Re=634 and Φ=2%.Furthermore,regarding the increment of the Nu number,it was shown that the use of twisted tapes individually could increase the average Nu number by 41%,while the max increment arising from individual use of 2% nano-particles is 13%,so using twisted tape is a more effective-technique for this case study.展开更多
In this paper,the blade is assumed to be a rotating variable thickness cantilever twisted plate structure,and the natural vibrations of variable thickness cantilever twisted plate made of metal porous material are stu...In this paper,the blade is assumed to be a rotating variable thickness cantilever twisted plate structure,and the natural vibrations of variable thickness cantilever twisted plate made of metal porous material are studied.It is assumed that the thickness of the plate changes along spanwise direction and chordwise direction,respectively,and it changes in both directions.The classical thin shell theory,the first and second fundamental forms of surface and von Karman geometric relationship are employed to derive the total potential energy and kinetic energy of the cantilever twisted plate,in which the centrifugal force potential due to high rotational speed is included.Then,according to the Rayleigh-Ritz procedure and applying the polynomial functions which satisfy the cantilever boundary conditions,the dynamic system expressed by equations of motion is reduced to an eigenvalue problem.By numerical simulation,the frequency curves and the mode shapes of the twisted plate can be obtained to reveal the internal connection between natural vibration and the parameters.A series of comparison studies are performed to verify the accuracy of the present formulation and calculations,in which compared data come from experimental,finite element method and theoretical calculation,respectively.The influence of pre-twist angle,three different forms of thickness taper ratio and rotational speed on natural vibration,mode exchange and frequency veering phenomenon of the system is discussed in detail.In addition,the approach proposed here can efficiently extract analytical expressions of mode functions for rotating variable thickness cantilever twisted plate structures.展开更多
文摘In the present study,hydraulic and thermal behavior of an automatic transmission nano-fluid(ATNF) inside a tube with a twisted tape has been investigated.The heat transfer improvement and pressure drop of transmission oil for each of case of using twisted tape and nano-particles were also examined separately and compared with each other.The Cu O nano-particles were used to prepare the ATNF.The effects of different Reynolds numbers and different mass fractions of nano-particle were investigated.The results showed that applying nano-particles and twisted tape simultaneously increases both the pressure drop and Nusselt number,on average by about 53% and 76%,respectively.By using a parameter,namely thermal performance index η,the effect of increasing heat transfer and pressure drop was studied simultaneously.The heat transfer improvement predominates the pressure drop increment in all cases.It was observed that the highest thermal performance of 1.9 was obtained at Re=634 and Φ=2%.Furthermore,regarding the increment of the Nu number,it was shown that the use of twisted tapes individually could increase the average Nu number by 41%,while the max increment arising from individual use of 2% nano-particles is 13%,so using twisted tape is a more effective-technique for this case study.
基金the financial support of National Natural Science Foundation of China through grant nos.11872127,11832002,11732005Qin Xin Talents Cultivation ProgramBeijing Information Science&Technology University QXTCP A201901。
文摘In this paper,the blade is assumed to be a rotating variable thickness cantilever twisted plate structure,and the natural vibrations of variable thickness cantilever twisted plate made of metal porous material are studied.It is assumed that the thickness of the plate changes along spanwise direction and chordwise direction,respectively,and it changes in both directions.The classical thin shell theory,the first and second fundamental forms of surface and von Karman geometric relationship are employed to derive the total potential energy and kinetic energy of the cantilever twisted plate,in which the centrifugal force potential due to high rotational speed is included.Then,according to the Rayleigh-Ritz procedure and applying the polynomial functions which satisfy the cantilever boundary conditions,the dynamic system expressed by equations of motion is reduced to an eigenvalue problem.By numerical simulation,the frequency curves and the mode shapes of the twisted plate can be obtained to reveal the internal connection between natural vibration and the parameters.A series of comparison studies are performed to verify the accuracy of the present formulation and calculations,in which compared data come from experimental,finite element method and theoretical calculation,respectively.The influence of pre-twist angle,three different forms of thickness taper ratio and rotational speed on natural vibration,mode exchange and frequency veering phenomenon of the system is discussed in detail.In addition,the approach proposed here can efficiently extract analytical expressions of mode functions for rotating variable thickness cantilever twisted plate structures.
