Pure nitrogen gas was heated with direct current arc, at input powers from several hundred Watt to over 5 kW, and then injected through a nozzle into a chamber at 1 or 10 Pa pressure, with the purpose of accelerating ...Pure nitrogen gas was heated with direct current arc, at input powers from several hundred Watt to over 5 kW, and then injected through a nozzle into a chamber at 1 or 10 Pa pressure, with the purpose of accelerating the gas to very high speed around 7 km/s. Various structures of the arc generator and gas expansion nozzle were examined. Results show that bypass exhausting of the boundary layer before it enters the nozzle divergent section can greatly increase flow speed of the jet, thus it might be possible to use nitrogen as a working gas in high speed gas dynamic test facilities.展开更多
The current article presents conceptual,preliminary and detailed aero-thermal redesign of a typical high pressure turbine nozzle guide vane.Design targets are lower coolant consumption,reduced manufacturing costs an...The current article presents conceptual,preliminary and detailed aero-thermal redesign of a typical high pressure turbine nozzle guide vane.Design targets are lower coolant consumption,reduced manufacturing costs and improved durability.These goals are sought by 25%reduction in vane count number and lower number of airfoils per segment.Design challenges such as higher airfoil loading,associate aerodynamic losses and higher thermal loads are discussed.In order to maximize coolant flow reduction and avoid higher aerodynamic losses,airfoil Mach distribution is carefully controlled.There has been an effort to limit design changes so that the proven design features of the original vane are used as much as possible.Accordingly,the same cooling concept is used with minor modifications of the internal structures in order to achieve desired coolant flow and internal heat transfer distribution.Platforms of the new design are quite similar to the original one except for cooling holes and application of thermal barrier coating(TBC).Detailed aerodynamics/heat transfer simulations reveals that the reduced trailing edge(T.E.)blockage and skin friction dominated the negative effect of increased secondary losses.As a result the reduced design performs acceptable in terms of total pressure loss and improving stage efficiency for a wide range of varying pressure ratio.Moreover,more than 20%cooling mass flow can be saved;while maximum and average metal temperatures as well as cross sectional temperature gradients have not been changed much.展开更多
In this paper, the effects of polymer additives and nozzle shape on the proper- ties of high pressure water jet discharging into the air are investigated by theory and experiments. Criteria of judging the jet quality ...In this paper, the effects of polymer additives and nozzle shape on the proper- ties of high pressure water jet discharging into the air are investigated by theory and experiments. Criteria of judging the jet quality are put forward. And, a method that can be used in analysing the fluid flow within the nozzle is developed. Then, the calculated results are compared with the experiments that we carried out; it is shown that the degree of agreement between the two is good. At last, the mechanism to improve on the jet quality with polymer additives is discussed.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11575273 and 11475239)
文摘Pure nitrogen gas was heated with direct current arc, at input powers from several hundred Watt to over 5 kW, and then injected through a nozzle into a chamber at 1 or 10 Pa pressure, with the purpose of accelerating the gas to very high speed around 7 km/s. Various structures of the arc generator and gas expansion nozzle were examined. Results show that bypass exhausting of the boundary layer before it enters the nozzle divergent section can greatly increase flow speed of the jet, thus it might be possible to use nitrogen as a working gas in high speed gas dynamic test facilities.
文摘The current article presents conceptual,preliminary and detailed aero-thermal redesign of a typical high pressure turbine nozzle guide vane.Design targets are lower coolant consumption,reduced manufacturing costs and improved durability.These goals are sought by 25%reduction in vane count number and lower number of airfoils per segment.Design challenges such as higher airfoil loading,associate aerodynamic losses and higher thermal loads are discussed.In order to maximize coolant flow reduction and avoid higher aerodynamic losses,airfoil Mach distribution is carefully controlled.There has been an effort to limit design changes so that the proven design features of the original vane are used as much as possible.Accordingly,the same cooling concept is used with minor modifications of the internal structures in order to achieve desired coolant flow and internal heat transfer distribution.Platforms of the new design are quite similar to the original one except for cooling holes and application of thermal barrier coating(TBC).Detailed aerodynamics/heat transfer simulations reveals that the reduced trailing edge(T.E.)blockage and skin friction dominated the negative effect of increased secondary losses.As a result the reduced design performs acceptable in terms of total pressure loss and improving stage efficiency for a wide range of varying pressure ratio.Moreover,more than 20%cooling mass flow can be saved;while maximum and average metal temperatures as well as cross sectional temperature gradients have not been changed much.
文摘In this paper, the effects of polymer additives and nozzle shape on the proper- ties of high pressure water jet discharging into the air are investigated by theory and experiments. Criteria of judging the jet quality are put forward. And, a method that can be used in analysing the fluid flow within the nozzle is developed. Then, the calculated results are compared with the experiments that we carried out; it is shown that the degree of agreement between the two is good. At last, the mechanism to improve on the jet quality with polymer additives is discussed.
