The characteristics of unsteady flow in a dual-flowpath inlet,which was designed for a Turbine Based Combined Cycle(TBCC)propulsion system,and the control methods of unsteady flow were investigated experimentally and ...The characteristics of unsteady flow in a dual-flowpath inlet,which was designed for a Turbine Based Combined Cycle(TBCC)propulsion system,and the control methods of unsteady flow were investigated experimentally and numerically.It was characterized by large-amplitude pressure oscillations and traveling shock waves.As the inlet operated in supercritical condition,namely the terminal shock located in the throat,the shock oscillated,and the period of oscillation was about 50 ms,while the amplitude was 6 mm.The shock oscillation was caused by separation in the diffuser.This shock oscillation can be controlled by extending the length of diffuser which reduces pressure gradient along the flowpath.As the inlet operated in critical condition,namely the terminal shock located at the shoulder of the third compression ramp,the shock oscillated,and the period of oscillation was about 7.5 ms,while the amplitude was 12 mm.At this condition,the shock oscillation was caused by an incompatible backpressure in the bleed region.It can be controlled by increasing the backpressure of the bleed region.展开更多
A series of numerical simulations were conducted in both a 1.5stage axial compressor model and a simplified planar cascade model.The cases with different blade sweep schemes in the cascade model were simulated with fr...A series of numerical simulations were conducted in both a 1.5stage axial compressor model and a simplified planar cascade model.The cases with different blade sweep schemes in the cascade model were simulated with free-slip endwalls to minimize the influence of endwall 3-D(three-dimensional)flows.The results obtained in the cascade model were discussed at first for getting a clear insight into the effects of blade sweep without other influences.And then the simulation results of the 1.5stage compressor model were discussed accordingly.The discussions focused on the influences of different meridional flowpath designs,i.e.constant mid radius(CMR)design,constant outer radius(COR)design and constant inner radius(CIR)design,on the performance of the swept blade.The results showed that the most critical effect produced by blade sweep was attributed to the redistribution of local mass-flow-rate in blade spanwise direction.The change of meridional flowpath did not change the mass-flow-rate redistribution behaviors.However,the trends for local mass-flow-rate redistribution in compressor stage model showed some discrepancies compared with the results shown in the planar cascade model.展开更多
Pathways for acid rock drainage from an abandoned mining site (sulphidic ore) were investigated by analysing ground, seepage and surface waters. It was found that in affected ground and seepage waters pH was lower (av...Pathways for acid rock drainage from an abandoned mining site (sulphidic ore) were investigated by analysing ground, seepage and surface waters. It was found that in affected ground and seepage waters pH was lower (average pH 5.0);sulphate higher (average 350 mg/L) and trace element concentrations were significantly increased (4330 μg/L copper and 7700 μg/L zinc) compared to surrounding waters. Multivariate statistics (principal component analysis) were used on the data set. Obtained loading plot showed a clear negative correlation between pH and parameters found at high concentrations, indicating that these parameters are found at the source term (acid rock drainage). Lead was also found in close proximity to iron and turbidity indicating that lead might be associated with particles. The score plot presented almost all samples from high concentrations to low concentrations along the first principal component (explaining 63% of the variation in the data set) indicating that dilution was an important mechanism for the decrease in concentrations as opposed to immobilisation on surfaces along the flowpath. Decrease in fluoride and sulphate along one of the suspected flowpath coincided with an increase in calcium. Through geochemical calculations it was concluded that calcite (CaCO<sub>3</sub>) dissolved along the flowpath and thus induced precipitation of gypsum (CaSO<sub>4</sub>) and fluorite (CaF<sub>2<sub>). Through a combination of PCA and geochemical calculations the most likely flowpaths for contaminated water from the abandoned mining site were presented, making it possible to prevent further negative effects on the surface water.</sub></sub>展开更多
基金supported by the Funding for Outstanding Doctoral Dissertation in NUAA of China(No.BCXJ16-01)Funding of Jiangsu Innovation Program for Graduate Education(No.KYLX16_0393)+2 种基金Foundation of Graduate Innovation Center in NUAA of China(No.KFJJ20160204)the Fundamental Research Funds for the Central Universities and the Aerospace ScienceTechnology Innovation Fund of China Aerospace Science and Technology Corporation
文摘The characteristics of unsteady flow in a dual-flowpath inlet,which was designed for a Turbine Based Combined Cycle(TBCC)propulsion system,and the control methods of unsteady flow were investigated experimentally and numerically.It was characterized by large-amplitude pressure oscillations and traveling shock waves.As the inlet operated in supercritical condition,namely the terminal shock located in the throat,the shock oscillated,and the period of oscillation was about 50 ms,while the amplitude was 6 mm.The shock oscillation was caused by separation in the diffuser.This shock oscillation can be controlled by extending the length of diffuser which reduces pressure gradient along the flowpath.As the inlet operated in critical condition,namely the terminal shock located at the shoulder of the third compression ramp,the shock oscillated,and the period of oscillation was about 7.5 ms,while the amplitude was 12 mm.At this condition,the shock oscillation was caused by an incompatible backpressure in the bleed region.It can be controlled by increasing the backpressure of the bleed region.
基金National Science Foundation of China(51006007,51136003,50976009)
文摘A series of numerical simulations were conducted in both a 1.5stage axial compressor model and a simplified planar cascade model.The cases with different blade sweep schemes in the cascade model were simulated with free-slip endwalls to minimize the influence of endwall 3-D(three-dimensional)flows.The results obtained in the cascade model were discussed at first for getting a clear insight into the effects of blade sweep without other influences.And then the simulation results of the 1.5stage compressor model were discussed accordingly.The discussions focused on the influences of different meridional flowpath designs,i.e.constant mid radius(CMR)design,constant outer radius(COR)design and constant inner radius(CIR)design,on the performance of the swept blade.The results showed that the most critical effect produced by blade sweep was attributed to the redistribution of local mass-flow-rate in blade spanwise direction.The change of meridional flowpath did not change the mass-flow-rate redistribution behaviors.However,the trends for local mass-flow-rate redistribution in compressor stage model showed some discrepancies compared with the results shown in the planar cascade model.
文摘Pathways for acid rock drainage from an abandoned mining site (sulphidic ore) were investigated by analysing ground, seepage and surface waters. It was found that in affected ground and seepage waters pH was lower (average pH 5.0);sulphate higher (average 350 mg/L) and trace element concentrations were significantly increased (4330 μg/L copper and 7700 μg/L zinc) compared to surrounding waters. Multivariate statistics (principal component analysis) were used on the data set. Obtained loading plot showed a clear negative correlation between pH and parameters found at high concentrations, indicating that these parameters are found at the source term (acid rock drainage). Lead was also found in close proximity to iron and turbidity indicating that lead might be associated with particles. The score plot presented almost all samples from high concentrations to low concentrations along the first principal component (explaining 63% of the variation in the data set) indicating that dilution was an important mechanism for the decrease in concentrations as opposed to immobilisation on surfaces along the flowpath. Decrease in fluoride and sulphate along one of the suspected flowpath coincided with an increase in calcium. Through geochemical calculations it was concluded that calcite (CaCO<sub>3</sub>) dissolved along the flowpath and thus induced precipitation of gypsum (CaSO<sub>4</sub>) and fluorite (CaF<sub>2<sub>). Through a combination of PCA and geochemical calculations the most likely flowpaths for contaminated water from the abandoned mining site were presented, making it possible to prevent further negative effects on the surface water.</sub></sub>
