The possibility of applying a high-pressure hydro-jet for renewal of the grinding wheel cutting ability was presented.This work was conducted in the internal cylindrical grinding process of the Titanium Grade 2 alloy,...The possibility of applying a high-pressure hydro-jet for renewal of the grinding wheel cutting ability was presented.This work was conducted in the internal cylindrical grinding process of the Titanium Grade 2 alloy,which belongs to the group of hard-to-cut materials.The analysis shows that the impact on the erosion effectiveness of the grinding wheel active surface(GWAS)depends upon the hydro-jet inclination angle and working pressure.Experimental results reveal that application of hydro-jet working pressure of 25 MPa allows for effective cleansing of the grinding wheel surface.Depending on the initial GWAS condition and the level of its smearing with chips of machined material,it is possible to increase the number of grinding wheel unevenness apexes by as much as 4.5 times.展开更多
Effects of operating conditions and device's geometrical sizes on geometrical properties of wall-attaching transonic jet between two parallel plat plates are numerically simulated. Conclusions are as follows: 1) U...Effects of operating conditions and device's geometrical sizes on geometrical properties of wall-attaching transonic jet between two parallel plat plates are numerically simulated. Conclusions are as follows: 1) Upriver part of the wall-attaching jet's center streamline is in good accordance with parabola; 2) When both gas inlet pressure and outlet pressure as well as their ratio are not too high ( the outlet pressure is less than 10 MPa and the pressure ratio is less than 3), the center streamlines of the wall-attaching jet with the same pressure ratio coincide with each other very well, and the deflection degree of the center streamline decreases with rise of the pressure ratio; 3) The deflection degree of the jet's center streamline decreases with either broadening of nozzle's throat or rise of wall offset; 4) With rise of the pressure ratio, attachment distance of the jet increases, but the increase rate descends; 5) The attachment distance ascends with rise of either the nozzle's throat or the wall offset.展开更多
The pressure matching and recovery performances of the second-throat supersonic-supersonic ejector have been performed experimentally and numerically in the current study.Schlieren pictures of flow structure in former...The pressure matching and recovery performances of the second-throat supersonic-supersonic ejector have been performed experimentally and numerically in the current study.Schlieren pictures of flow structure in former part of the mixing chamber with varied stagnation pressure ratio of the primary and secondary flows have been taken,and the maximum compression ratios have been obtained.Additionally,the relevant numerical simulations have been performed.The obtained results show that the pressure matching performance of the second-throat supersonic-supersonic ejector is weaker than that of the constant area one,and the pressure recovery performance of the former is better than that of the latter.For the ejectors tested in this paper,the stagnation pressure ratios of the second-throat supersonic-supersonic ejector at the limiting condition are approximately 10% lower than those of the constant area one when the contraction angle of the mixing chamber is 4°,and the maximum compression ratio is 12%-30% higher.When the contraction angle of the mixing chamber is 6°,the pressure matching performance of the second-throat supersonic-supersonic ejector declines sharply,and the pressure recovery performance remains almost the same.When the contraction angle of the mixing chamber is 8°,the supersonic-supersonic ejection phenomenon does not take place any longer.展开更多
The Coanda effect has long been employed in the aerospace applications to improve the performances of various devices. This effect is the ability of a flow to follow a curved contour without separation and has well be...The Coanda effect has long been employed in the aerospace applications to improve the performances of various devices. This effect is the ability of a flow to follow a curved contour without separation and has well been utilized in ejectors where a high speed jet of fluid emerges from a nozzle in the ejector body, follows a curved surface and drags the secondary flow into the ejector. In Coanda ejectors, the secondary flow is dragged in the ejector due to the primary flow momentum. The transfer of momentum from the primary flow to the secondary flow takes place through turbulent mixing and viscous effects. The secondary flow is then dragged by turbulent shear force of the ejector while being mixed with the primary flow by the persistence of a large turbulent intensity throughout the ejector. The performance of a Coanda ejector is studied mainly based on how well it drags the secondary flow and the amount of mixing between the two flows at the ejector exit. The aim of the present study is to investigate the influence of various geometric parameters and pressure ratios on the Coanda ejector performance. The effect of various factors, such as, the pressure ratio, primary nozzle and ejector configurations on the system performance has been evaluated based on a performance parameter defined elsewhere. The performance of the Coanda ejector strongly depends on the primary nozzle configuration and the pressure ratio. The mixing layer growth plays a major role in optimizing the performance of the Coanda ejector as it decides the ratio of secondary mass flow rate to primary mass flow rate and the mixing length.展开更多
文摘The possibility of applying a high-pressure hydro-jet for renewal of the grinding wheel cutting ability was presented.This work was conducted in the internal cylindrical grinding process of the Titanium Grade 2 alloy,which belongs to the group of hard-to-cut materials.The analysis shows that the impact on the erosion effectiveness of the grinding wheel active surface(GWAS)depends upon the hydro-jet inclination angle and working pressure.Experimental results reveal that application of hydro-jet working pressure of 25 MPa allows for effective cleansing of the grinding wheel surface.Depending on the initial GWAS condition and the level of its smearing with chips of machined material,it is possible to increase the number of grinding wheel unevenness apexes by as much as 4.5 times.
基金Chinese 863 National Program Foundation(No.2006AA05Z216)
文摘Effects of operating conditions and device's geometrical sizes on geometrical properties of wall-attaching transonic jet between two parallel plat plates are numerically simulated. Conclusions are as follows: 1) Upriver part of the wall-attaching jet's center streamline is in good accordance with parabola; 2) When both gas inlet pressure and outlet pressure as well as their ratio are not too high ( the outlet pressure is less than 10 MPa and the pressure ratio is less than 3), the center streamlines of the wall-attaching jet with the same pressure ratio coincide with each other very well, and the deflection degree of the center streamline decreases with rise of the pressure ratio; 3) The deflection degree of the jet's center streamline decreases with either broadening of nozzle's throat or rise of wall offset; 4) With rise of the pressure ratio, attachment distance of the jet increases, but the increase rate descends; 5) The attachment distance ascends with rise of either the nozzle's throat or the wall offset.
基金supported by the National Natural Science Foundation of China (Grant No. 11172324)
文摘The pressure matching and recovery performances of the second-throat supersonic-supersonic ejector have been performed experimentally and numerically in the current study.Schlieren pictures of flow structure in former part of the mixing chamber with varied stagnation pressure ratio of the primary and secondary flows have been taken,and the maximum compression ratios have been obtained.Additionally,the relevant numerical simulations have been performed.The obtained results show that the pressure matching performance of the second-throat supersonic-supersonic ejector is weaker than that of the constant area one,and the pressure recovery performance of the former is better than that of the latter.For the ejectors tested in this paper,the stagnation pressure ratios of the second-throat supersonic-supersonic ejector at the limiting condition are approximately 10% lower than those of the constant area one when the contraction angle of the mixing chamber is 4°,and the maximum compression ratio is 12%-30% higher.When the contraction angle of the mixing chamber is 6°,the pressure matching performance of the second-throat supersonic-supersonic ejector declines sharply,and the pressure recovery performance remains almost the same.When the contraction angle of the mixing chamber is 8°,the supersonic-supersonic ejection phenomenon does not take place any longer.
文摘The Coanda effect has long been employed in the aerospace applications to improve the performances of various devices. This effect is the ability of a flow to follow a curved contour without separation and has well been utilized in ejectors where a high speed jet of fluid emerges from a nozzle in the ejector body, follows a curved surface and drags the secondary flow into the ejector. In Coanda ejectors, the secondary flow is dragged in the ejector due to the primary flow momentum. The transfer of momentum from the primary flow to the secondary flow takes place through turbulent mixing and viscous effects. The secondary flow is then dragged by turbulent shear force of the ejector while being mixed with the primary flow by the persistence of a large turbulent intensity throughout the ejector. The performance of a Coanda ejector is studied mainly based on how well it drags the secondary flow and the amount of mixing between the two flows at the ejector exit. The aim of the present study is to investigate the influence of various geometric parameters and pressure ratios on the Coanda ejector performance. The effect of various factors, such as, the pressure ratio, primary nozzle and ejector configurations on the system performance has been evaluated based on a performance parameter defined elsewhere. The performance of the Coanda ejector strongly depends on the primary nozzle configuration and the pressure ratio. The mixing layer growth plays a major role in optimizing the performance of the Coanda ejector as it decides the ratio of secondary mass flow rate to primary mass flow rate and the mixing length.
