Both the academic society and the industry are hunting for new energy forms for the future.However,the world should not forget the conventional technologies that contribute to the sustainable society by technical inno...Both the academic society and the industry are hunting for new energy forms for the future.However,the world should not forget the conventional technologies that contribute to the sustainable society by technical innovations.Among them,lubrication plays a significant role in energy saving and in low CO2emission by increasing the fuel efficiency and by prolonging the service life of machines.With the advance of novel synthetic approaches,and nanoscience and technologies,novel lubrication oils and additives and their formulations are being developed to reduce friction and wear,and novel surface treatment routes and surface coatings are invented and provide more efficient lubrication.These technologies create tremendous chances for machines to work more efficiently with low energy consumption.Here we review the recent progresses and challenges associated with some novel lubrication techniques that include novel surface treatment(such as texturing,high-performance nanocomposite coatings,adapting coating),tribology design(solid and liquid lubrication),energy-conserving engine oil and novel lubricants and formula(such as ionic liquids,low S,P content additives)which are to be adopted to enhance the fuel efficiency to achieve energy saving and low carbon emission.There is increased demand to replace fossil lubricants by degradable green lubricants.Specially designed coatings can reduce drag significantly during navigation of both airplanes and ships.All these aspects will be also reviewed in the paper.展开更多
The aim of this paper is to predict the phenomenon of laminar separation, transition and reattachment in a low-pressure turbine （LPT）. Self-developed large eddy simulation program of compressible N-S equations was u...The aim of this paper is to predict the phenomenon of laminar separation, transition and reattachment in a low-pressure turbine （LPT）. Self-developed large eddy simulation program of compressible N-S equations was used to describe the flow structures of T 106A LPT blade profile at Reynolds number of 1.1×10^5 based on the exit isentropic velocity and chord length. The com- putational results show the distributions of time-averaged wall-static pressure coefficient and mean skin-friction coefficient on the blade surface. The locations of laminar separation and reattachment points occur around 87% and 98% axial chord, which agree well with experiment data. The two-dimensional shear layer is gradually unstable along the downstream half of the suc- tion side as a result of the spanwise fluctuation and the roll up of shear layer via Kelvin-Helmholtz （KH） instability. Three-dimensional motions appear near 84% axial chord which later triggers spanwise vortexes and streamwise vortexes, leading to transition to turbulence in the separation bubble. Through introducing the concept of dissipation function, the high loss mainly comes from the places where strong shear layer and intense fluctuation exist. Furthermore, the separation region is only an accumulation center of the low-energy fluid rather than an area of loss source.展开更多
A description and results of tests of a new small-scale gage for direct measurement of skin friction force are presented in the paper.The gage design provides separated measurement of longitudinal and transversal comp...A description and results of tests of a new small-scale gage for direct measurement of skin friction force are presented in the paper.The gage design provides separated measurement of longitudinal and transversal component of friction force.Application of this scheme provides high sensitivity and necessary high-frequency response of the gage.The tests of the gage were carried out in a blow down wind tunnel at Mach numbers of 2 and 4 within the range of Reynolds numbers Rex from 0.8 to 5 million and in the hot-shot wind tunnel at Mach number 6 and Reynolds numbers Rex=2.5-10 million.The measurements of skin friction were carried out on a flat plate and on a ramp beyond the shock wave.Simultaneously with the direct measurement of friction in the blow down wind tunnel,the measurements of profiles of average velocities and mass flow rate pulsations were realised.Analysis of measurement errors has shown that the friction gage permits to measure skin friction coefficient on a flat plate with mistake not more than 10%.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.21125316,50935008,51305428) the"Hundred Talents Program"of CAS
文摘Both the academic society and the industry are hunting for new energy forms for the future.However,the world should not forget the conventional technologies that contribute to the sustainable society by technical innovations.Among them,lubrication plays a significant role in energy saving and in low CO2emission by increasing the fuel efficiency and by prolonging the service life of machines.With the advance of novel synthetic approaches,and nanoscience and technologies,novel lubrication oils and additives and their formulations are being developed to reduce friction and wear,and novel surface treatment routes and surface coatings are invented and provide more efficient lubrication.These technologies create tremendous chances for machines to work more efficiently with low energy consumption.Here we review the recent progresses and challenges associated with some novel lubrication techniques that include novel surface treatment(such as texturing,high-performance nanocomposite coatings,adapting coating),tribology design(solid and liquid lubrication),energy-conserving engine oil and novel lubricants and formula(such as ionic liquids,low S,P content additives)which are to be adopted to enhance the fuel efficiency to achieve energy saving and low carbon emission.There is increased demand to replace fossil lubricants by degradable green lubricants.Specially designed coatings can reduce drag significantly during navigation of both airplanes and ships.All these aspects will be also reviewed in the paper.
基金supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.51121004)the National Natural Science Foundation of China(Grant No.50976026)
文摘The aim of this paper is to predict the phenomenon of laminar separation, transition and reattachment in a low-pressure turbine （LPT）. Self-developed large eddy simulation program of compressible N-S equations was used to describe the flow structures of T 106A LPT blade profile at Reynolds number of 1.1×10^5 based on the exit isentropic velocity and chord length. The com- putational results show the distributions of time-averaged wall-static pressure coefficient and mean skin-friction coefficient on the blade surface. The locations of laminar separation and reattachment points occur around 87% and 98% axial chord, which agree well with experiment data. The two-dimensional shear layer is gradually unstable along the downstream half of the suc- tion side as a result of the spanwise fluctuation and the roll up of shear layer via Kelvin-Helmholtz （KH） instability. Three-dimensional motions appear near 84% axial chord which later triggers spanwise vortexes and streamwise vortexes, leading to transition to turbulence in the separation bubble. Through introducing the concept of dissipation function, the high loss mainly comes from the places where strong shear layer and intense fluctuation exist. Furthermore, the separation region is only an accumulation center of the low-energy fluid rather than an area of loss source.
文摘A description and results of tests of a new small-scale gage for direct measurement of skin friction force are presented in the paper.The gage design provides separated measurement of longitudinal and transversal component of friction force.Application of this scheme provides high sensitivity and necessary high-frequency response of the gage.The tests of the gage were carried out in a blow down wind tunnel at Mach numbers of 2 and 4 within the range of Reynolds numbers Rex from 0.8 to 5 million and in the hot-shot wind tunnel at Mach number 6 and Reynolds numbers Rex=2.5-10 million.The measurements of skin friction were carried out on a flat plate and on a ramp beyond the shock wave.Simultaneously with the direct measurement of friction in the blow down wind tunnel,the measurements of profiles of average velocities and mass flow rate pulsations were realised.Analysis of measurement errors has shown that the friction gage permits to measure skin friction coefficient on a flat plate with mistake not more than 10%.
