The oblique detonation chamber has an extreme high and uneven thermal load due to the fast exothermic combustion process induced by oblique shock wave.The active cooling technology of over-pressure water is an effecti...The oblique detonation chamber has an extreme high and uneven thermal load due to the fast exothermic combustion process induced by oblique shock wave.The active cooling technology of over-pressure water is an effective thermal protection method with the development of additive manufacturing technology.The realizable κ-ε model coupling with Volume Fraction(VOF) model is applied to solve the boiling flow of cooling water in the mini-channels.The phase transition and heat transfer characteristics are systematically investigated under different pressures.The phase transition process is first observed in the position of oblique detonation wave,and the bubbly flow,the slug flow,the annular flow and the churn flow are captured in the characteristic cooling channel when boiling flow reaching steady stage.In the rear section of the channel,the uneven heat flux distribution of combustion chamber brings to the churn flow,which enhances the heat transfer compared to the annular flow.Compared to the atmospheric water,the appearances of churn flow and annular flow are significantly decreased with the increasing pressure,and they would disappear when the pressure is exceeding 0.5 MPa.The bubbly flow and slug flow play a dominant role when the pressure is higher than 1 MPa,showing that the over-pressure water can significantly enhance the cooling efficiency of the oblique detonation chamber.With the rise of water pressure,the time point of the appearance of phase transition is obviously lagged because of the increasing latent heat of vaporization,and the cooling efficiency is significantly increased due to the simpler phase transition in higher pressure,which means the over-pressure water could withstand longer heat load of oblique detonation engine.展开更多
Ballistic impact and sealed chamber tests were performed on the steel-encased reactive material projectile(SERMP)to understand its behind-plate overpressure effect when impacting the thin aluminum plates.The reactive ...Ballistic impact and sealed chamber tests were performed on the steel-encased reactive material projectile(SERMP)to understand its behind-plate overpressure effect when impacting the thin aluminum plates.The reactive material encased with a 1.5 mm thick 30CrMnSiNi2A steel shell was launched onto the initially sealed test chamber with a 3 mm thick 2024-T3 thin aluminum cover plate.Moreover,the overpressure signals in the test chamber were recorded by pressure sensors.The experimental results indicate an unusual behind-plate overpressure effect:as the density of the projectile increases from 6.43 g/cm^(3) to 7.58 g/cm^(3) by increasing the content of tungsten powder,although its total chemical energy decreases,it produces a higher behind-target overpressure at a lower impact velocity.A theoretical model is proposed to predict the reaction length of reactive material inside the projectile based on one-dimensional shock wave theory to understand this unexpected result.In addition,the deviation between the actual energy release and the theoretical calculation results,also the variation of overpressure rise time are analyzed and discussed.As the analyses show,when the SERMP successfully penetrates the cover plate,an increasing density of the reactive material inside the projectile always means that the delaying rarefaction wave effect,an increase of its internal pressure and strain rate levels.These factors lead to the increase of the overpressure limit velocity and reaction extent of the reactive material,while the overpressure rise time decreases.展开更多
Facing the contradiction of water scarcity and water wastage in most cities of China, this study aims at probing into the factors influencing water-use efficiency and assessing water-saving potential by adopting press...Facing the contradiction of water scarcity and water wastage in most cities of China, this study aims at probing into the factors influencing water-use efficiency and assessing water-saving potential by adopting pressure control measures based on field survey conducted in 23 high-rise buildings in Suqian, China and laboratory tests. Results showed that per capita water consumption (PCWC) exceeding water consumption norms is common in these buildings. The hourly water consumption variation law is quite different among different types of buildings. These differences should be considered in designing building water supply systems to lower water and energy consumption. On the basis of correlation analysis, the order of factors influencing the PCWC follows average tap water pressure, percapita building area, and building age, suggesting pressure management in high-rise buildings is a key water-saving measure. Field tests of outflow characteristics under different water pressures indicated that over-pressure outflow (OPO) is a common cause of water wastage in buildings, however, no branch pipe pressure control measures were found in all the surveyed buildings. Laboratory tests showed that branch pipe pressure-reducing measures can lower water consumption and improve the comfortability of use as well. Therefore, in addition to applying high efficiency water-saving devices, we strongly recommend that branch pipe pressure-reducing measures should be strictly implemented in designing new building water supply systems and reconstruction of existing old building water supply systems, thereby, promoting water, energy saving and development of green building.展开更多
The structural phase transitions of bismuth under rapid compression has been investigated in a dynamic diamond anvil cell using time-resolved synchrotron x-ray diffraction. As the pressure increases, the transformatio...The structural phase transitions of bismuth under rapid compression has been investigated in a dynamic diamond anvil cell using time-resolved synchrotron x-ray diffraction. As the pressure increases, the transformations from phase I,to phase II, to phase III, and then to phase V have been observed under different compression rates at 300 K. Compared with static compression results, no new phase transition sequence appears under rapid compression at compression rate from 0.20 GPa/s to 183.8 GPa/s. However, during the process across the transition from phase III to phase V, the volume fraction of product phase as a function of pressure can be well fitted by a compression-rate-dependent sigmoidal curve.The resulting parameters indicate that the activation energy related to this phase transition, as well as the onset transition pressure, shows a compression-rate-dependent performance. A strong dependence of over-pressurization on compression rate occurs under rapid compression. A formula for over-pressure has been proposed, which can be used to quantify the over-pressurization.展开更多
基金supports provided by Science Center for Gas Turbine Project (P2022-B-Ⅱ-028-001).
文摘The oblique detonation chamber has an extreme high and uneven thermal load due to the fast exothermic combustion process induced by oblique shock wave.The active cooling technology of over-pressure water is an effective thermal protection method with the development of additive manufacturing technology.The realizable κ-ε model coupling with Volume Fraction(VOF) model is applied to solve the boiling flow of cooling water in the mini-channels.The phase transition and heat transfer characteristics are systematically investigated under different pressures.The phase transition process is first observed in the position of oblique detonation wave,and the bubbly flow,the slug flow,the annular flow and the churn flow are captured in the characteristic cooling channel when boiling flow reaching steady stage.In the rear section of the channel,the uneven heat flux distribution of combustion chamber brings to the churn flow,which enhances the heat transfer compared to the annular flow.Compared to the atmospheric water,the appearances of churn flow and annular flow are significantly decreased with the increasing pressure,and they would disappear when the pressure is exceeding 0.5 MPa.The bubbly flow and slug flow play a dominant role when the pressure is higher than 1 MPa,showing that the over-pressure water can significantly enhance the cooling efficiency of the oblique detonation chamber.With the rise of water pressure,the time point of the appearance of phase transition is obviously lagged because of the increasing latent heat of vaporization,and the cooling efficiency is significantly increased due to the simpler phase transition in higher pressure,which means the over-pressure water could withstand longer heat load of oblique detonation engine.
基金supported by National Natural Science Founda-tion of China,grant number U1730112.
文摘Ballistic impact and sealed chamber tests were performed on the steel-encased reactive material projectile(SERMP)to understand its behind-plate overpressure effect when impacting the thin aluminum plates.The reactive material encased with a 1.5 mm thick 30CrMnSiNi2A steel shell was launched onto the initially sealed test chamber with a 3 mm thick 2024-T3 thin aluminum cover plate.Moreover,the overpressure signals in the test chamber were recorded by pressure sensors.The experimental results indicate an unusual behind-plate overpressure effect:as the density of the projectile increases from 6.43 g/cm^(3) to 7.58 g/cm^(3) by increasing the content of tungsten powder,although its total chemical energy decreases,it produces a higher behind-target overpressure at a lower impact velocity.A theoretical model is proposed to predict the reaction length of reactive material inside the projectile based on one-dimensional shock wave theory to understand this unexpected result.In addition,the deviation between the actual energy release and the theoretical calculation results,also the variation of overpressure rise time are analyzed and discussed.As the analyses show,when the SERMP successfully penetrates the cover plate,an increasing density of the reactive material inside the projectile always means that the delaying rarefaction wave effect,an increase of its internal pressure and strain rate levels.These factors lead to the increase of the overpressure limit velocity and reaction extent of the reactive material,while the overpressure rise time decreases.
文摘Facing the contradiction of water scarcity and water wastage in most cities of China, this study aims at probing into the factors influencing water-use efficiency and assessing water-saving potential by adopting pressure control measures based on field survey conducted in 23 high-rise buildings in Suqian, China and laboratory tests. Results showed that per capita water consumption (PCWC) exceeding water consumption norms is common in these buildings. The hourly water consumption variation law is quite different among different types of buildings. These differences should be considered in designing building water supply systems to lower water and energy consumption. On the basis of correlation analysis, the order of factors influencing the PCWC follows average tap water pressure, percapita building area, and building age, suggesting pressure management in high-rise buildings is a key water-saving measure. Field tests of outflow characteristics under different water pressures indicated that over-pressure outflow (OPO) is a common cause of water wastage in buildings, however, no branch pipe pressure control measures were found in all the surveyed buildings. Laboratory tests showed that branch pipe pressure-reducing measures can lower water consumption and improve the comfortability of use as well. Therefore, in addition to applying high efficiency water-saving devices, we strongly recommend that branch pipe pressure-reducing measures should be strictly implemented in designing new building water supply systems and reconstruction of existing old building water supply systems, thereby, promoting water, energy saving and development of green building.
基金supported by the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics(NSAF)(Grant No.U1530134)the Foundation of National Key Laboratory of Shock Wave and Detonation Physics,China(Grant No.6142A0306010817)the Chinese Academy of Sciences(Grant Nos.KJCX2-SW-N20 and KJCX2-SW-N03)
文摘The structural phase transitions of bismuth under rapid compression has been investigated in a dynamic diamond anvil cell using time-resolved synchrotron x-ray diffraction. As the pressure increases, the transformations from phase I,to phase II, to phase III, and then to phase V have been observed under different compression rates at 300 K. Compared with static compression results, no new phase transition sequence appears under rapid compression at compression rate from 0.20 GPa/s to 183.8 GPa/s. However, during the process across the transition from phase III to phase V, the volume fraction of product phase as a function of pressure can be well fitted by a compression-rate-dependent sigmoidal curve.The resulting parameters indicate that the activation energy related to this phase transition, as well as the onset transition pressure, shows a compression-rate-dependent performance. A strong dependence of over-pressurization on compression rate occurs under rapid compression. A formula for over-pressure has been proposed, which can be used to quantify the over-pressurization.
