Hypersonic and high-enthalpy wind tunnels and their measurement techniques are the cornerstone of the hypersonic flight era that is a dream for human beings to fly faster,higher and further.The great progress has been...Hypersonic and high-enthalpy wind tunnels and their measurement techniques are the cornerstone of the hypersonic flight era that is a dream for human beings to fly faster,higher and further.The great progress has been achieved during the recent years and their critical technologies are still in an urgent need for further development.There are at least four kinds of hypersonic and high-enthalpy wind tunnels that are widely applied over the world and can be classified according to their operation modes.These wind tunnels are named as air-directly-heated hypersonic wind tunnel,light-gas-heated shock tunnel,free-piston-driven shock tunnel and detonation-driven shock tunnel,respectively.The critical technologies for developing the wind tunnels are introduced in this paper,and their merits and weakness are discussed based on wind tunnel performance evaluation.Measurement techniques especially developed for high-enthalpy flows are a part of the hypersonic wind tunnel technology because the flow is a chemically reacting gas motion and its diagnosis needs specially designed instruments.Three kinds of the measurement techniques considered to be of primary importance are introduced here,including the heat flux sensor,the aerodynamic balance,and optical diagnosis techniques.The techniques are developed usually for conventional wind tunnels,but further improved for hypersonic and high-enthalpy tunnels.The hypersonic ground test facilities have provided us with most of valuable experimental data on high-enthalpy flows and will play a more important role in hypersonic research area in the future.Therefore,several prospects for developing hypersonic and high-enthalpy wind tunnels are presented from our point of view.展开更多
For the purpose of improving turbine efficiency,a detailed investigation of flow field near rim seal region in the main annulus is absolutely essential.Purge flow egressed from the seal gap penetrates the hub boundary...For the purpose of improving turbine efficiency,a detailed investigation of flow field near rim seal region in the main annulus is absolutely essential.Purge flow egressed from the seal gap penetrates the hub boundary layer and travels along with the secondary flow in the main path.The propagation of the purge flow and its influence on the turbine performance are crucial and cannot be neglected in the aerodynamic and thermal design.In addition,the interaction of vane wake and blade potential field also has a significant impact on the turbine stage performance.In this study,flow field between inlet guide vanes(IGV)and rotor blades was experimentally investigated at specific positions with the help of a two-dimensional particle image velocimetry(2-D PIV).A phase-locking technique was also employed to capture the images of flow field at different rotor blade positions.Data acquired characterizes the impact of emergent purge flow on the flow structures within the main annulus.The impacts of vane wake and blade potential field on the flow fields were analyzed through characterizations provided by the time-averaged field results.Finally,flow fields at different main flow rates and under different seal gap widths were also presented and assessed.展开更多
The characteristics of a flow in spinning devices are one of the fundamental problems innew-type spinning.In this paper the vortex flow in interior of the shell-case was studied by usingexperimental methods,which incl...The characteristics of a flow in spinning devices are one of the fundamental problems innew-type spinning.In this paper the vortex flow in interior of the shell-case was studied by usingexperimental methods,which include flow visualization and laser doppler techniques.The flow sur-vey by measurement has been compared with that photographed by flow visualization method,andshows a fairly good conformity.The results of experiments are similar to those by numericalevaluation.展开更多
Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error...Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error due to the effect of bending waves. In a two-dimensional quasi-longitudinal wave held, the intensity vector is the sum of the effective intensity vector and the intensity variation vector. Its axial component is proportional to two imaginary parts of cross spectral densities and in the measurement, it is measured by a pair of two-transducer arrays. In a one-dimensional quasi-longitudinal wave field, the intensity variation is zero, the intensity is proportional to only one imaginary part of a cross spectral density and it can be measured using a two-transducer array. If bending and quasi-longitudinal waves coexist and the contribution from bending waves cannot be eliminated or reduced to a certain extent, the measured quasi-longitudinal wave intensity will contain a large error. The results measured on the three-beam structure show that quasi-longitudinal wave intensity can be accurately measured using the intensity technique when bending waves are negligible in comparison with quasi-longitudinal waves.展开更多
High resolution temperature measurement technique is one of the key techniques for measuring marine heat flow. Basing on Pt1000 platinum resistance which has the characteristics of high accuracy and good stability, we...High resolution temperature measurement technique is one of the key techniques for measuring marine heat flow. Basing on Pt1000 platinum resistance which has the characteristics of high accuracy and good stability, we designed a bridge reversal excitation circuit for high resolution temperature measurement. And the deep ocean floor in-situ test results show that: (1) temperature deviation and peak-to-peak resolution of the first version circuit board (V1) are 1.960-1.990 mK and 0.980-0.995 m Kat 1.2-2.7°C, respectively; and temperature deviation and peak-to-peak resolution of the second circuit board (V2) are 2.260mK and 1.130 mK at 1.2-1.3°C, respectively; (2) During the 2012NSFC-IndOcean cruise, seafloor geothermal gradient at Ind2012HF03,-07 and-12 stations (water depth ranges from 3841 to 4541 m) were successfully measured, the values are 59.1,75.1 and 71.6°C/km, respectively. And the measurement errors of geothermal gradient at these three stations are less than 3.0% in terms of the peak-to-peak resolution. These indicate that the high resolution temperature measurement technique based on Pt1000 platinum resistance in this paper can be applied to marine heat flow measurement to obtain high precision geothermal parameters.展开更多
基金the support of the National Natural Science Foundation of China(Nos.11532014,11727901,11672308 and 11672357)the National Key Research and Development Program of China(No.2019YFA0405204)。
文摘Hypersonic and high-enthalpy wind tunnels and their measurement techniques are the cornerstone of the hypersonic flight era that is a dream for human beings to fly faster,higher and further.The great progress has been achieved during the recent years and their critical technologies are still in an urgent need for further development.There are at least four kinds of hypersonic and high-enthalpy wind tunnels that are widely applied over the world and can be classified according to their operation modes.These wind tunnels are named as air-directly-heated hypersonic wind tunnel,light-gas-heated shock tunnel,free-piston-driven shock tunnel and detonation-driven shock tunnel,respectively.The critical technologies for developing the wind tunnels are introduced in this paper,and their merits and weakness are discussed based on wind tunnel performance evaluation.Measurement techniques especially developed for high-enthalpy flows are a part of the hypersonic wind tunnel technology because the flow is a chemically reacting gas motion and its diagnosis needs specially designed instruments.Three kinds of the measurement techniques considered to be of primary importance are introduced here,including the heat flux sensor,the aerodynamic balance,and optical diagnosis techniques.The techniques are developed usually for conventional wind tunnels,but further improved for hypersonic and high-enthalpy tunnels.The hypersonic ground test facilities have provided us with most of valuable experimental data on high-enthalpy flows and will play a more important role in hypersonic research area in the future.Therefore,several prospects for developing hypersonic and high-enthalpy wind tunnels are presented from our point of view.
基金funded by the National Natural Science Foundation of China(Grant No.51776011)National Science and Technology Major Project(2017-V-0016-0068)。
文摘For the purpose of improving turbine efficiency,a detailed investigation of flow field near rim seal region in the main annulus is absolutely essential.Purge flow egressed from the seal gap penetrates the hub boundary layer and travels along with the secondary flow in the main path.The propagation of the purge flow and its influence on the turbine performance are crucial and cannot be neglected in the aerodynamic and thermal design.In addition,the interaction of vane wake and blade potential field also has a significant impact on the turbine stage performance.In this study,flow field between inlet guide vanes(IGV)and rotor blades was experimentally investigated at specific positions with the help of a two-dimensional particle image velocimetry(2-D PIV).A phase-locking technique was also employed to capture the images of flow field at different rotor blade positions.Data acquired characterizes the impact of emergent purge flow on the flow structures within the main annulus.The impacts of vane wake and blade potential field on the flow fields were analyzed through characterizations provided by the time-averaged field results.Finally,flow fields at different main flow rates and under different seal gap widths were also presented and assessed.
文摘The characteristics of a flow in spinning devices are one of the fundamental problems innew-type spinning.In this paper the vortex flow in interior of the shell-case was studied by usingexperimental methods,which include flow visualization and laser doppler techniques.The flow sur-vey by measurement has been compared with that photographed by flow visualization method,andshows a fairly good conformity.The results of experiments are similar to those by numericalevaluation.
文摘Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error due to the effect of bending waves. In a two-dimensional quasi-longitudinal wave held, the intensity vector is the sum of the effective intensity vector and the intensity variation vector. Its axial component is proportional to two imaginary parts of cross spectral densities and in the measurement, it is measured by a pair of two-transducer arrays. In a one-dimensional quasi-longitudinal wave field, the intensity variation is zero, the intensity is proportional to only one imaginary part of a cross spectral density and it can be measured using a two-transducer array. If bending and quasi-longitudinal waves coexist and the contribution from bending waves cannot be eliminated or reduced to a certain extent, the measured quasi-longitudinal wave intensity will contain a large error. The results measured on the three-beam structure show that quasi-longitudinal wave intensity can be accurately measured using the intensity technique when bending waves are negligible in comparison with quasi-longitudinal waves.
基金supported jointly by the Instrument Developing Project of the Chinese Academy of Sciences(Grant No.YZ201136)the National Natural Science Foundation of China(Grant No.41106086)+1 种基金the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.SQ201007) the Key Laboratory of Marginal Sea Geology,Chinese Academy of Sciences(Grant No.MSGL09-08)
文摘High resolution temperature measurement technique is one of the key techniques for measuring marine heat flow. Basing on Pt1000 platinum resistance which has the characteristics of high accuracy and good stability, we designed a bridge reversal excitation circuit for high resolution temperature measurement. And the deep ocean floor in-situ test results show that: (1) temperature deviation and peak-to-peak resolution of the first version circuit board (V1) are 1.960-1.990 mK and 0.980-0.995 m Kat 1.2-2.7°C, respectively; and temperature deviation and peak-to-peak resolution of the second circuit board (V2) are 2.260mK and 1.130 mK at 1.2-1.3°C, respectively; (2) During the 2012NSFC-IndOcean cruise, seafloor geothermal gradient at Ind2012HF03,-07 and-12 stations (water depth ranges from 3841 to 4541 m) were successfully measured, the values are 59.1,75.1 and 71.6°C/km, respectively. And the measurement errors of geothermal gradient at these three stations are less than 3.0% in terms of the peak-to-peak resolution. These indicate that the high resolution temperature measurement technique based on Pt1000 platinum resistance in this paper can be applied to marine heat flow measurement to obtain high precision geothermal parameters.
