In this study,calibrations of non-point source(NPS)pollution models are performed based on Black River basin historical real-time runoff data,sedimentation record data,and NPS sources survey information.The concept of...In this study,calibrations of non-point source(NPS)pollution models are performed based on Black River basin historical real-time runoff data,sedimentation record data,and NPS sources survey information.The concept of NPS loss coefficient for the watershed or the loss coefficients(LC)for simplicity is brought up by examining NPS build-up and migration processes along riverbanks in natural river systems.The historical data is used for determining the nitrogenous NPS loss coefficient for five land use types including farmland,urban land,grassland,shrub land,and forest under different precipitation conditions.The comparison of outputs from Soil and Water Assessment Tool(SWAT)model and coefficient export method showed that both methods could obtain reasonable LC.The high Pearson correlation coefficient(0.94722)between those two sets of calculation results justified the consistency of those two models.Another result in the study is that different combinations of precipitation condition and land use types could significantly affect the calculated loss coefficient.As for the adsorptive nitrogen,the order of impact on LC for different land use types can be sorted as:farm land.urban land.grassland.shrub land.forest while the order was farmland.grass land.shrub land.forest.urban land for soluble nitrogen.展开更多
In this paper,we studied theoretically and numerically heated losses of a flat solar collector to model the solar water heating system for the Kazakhstan climate condition.For different climatic zones with a growing c...In this paper,we studied theoretically and numerically heated losses of a flat solar collector to model the solar water heating system for the Kazakhstan climate condition.For different climatic zones with a growing cost for energy or lack of central heating systems,promising is to find ways to improve the energy efficiency of the solar system.The mathematical model(based on ordinary differential equation)simulated the solar system work process under different conditions.To bridge the modeling and real values results,we studied the important physical parameters such as loss coefficient,Nu,Ra,and Pr values.They impacted the efficiency of flat solar collectors and heat losses of the system.The developed mathematical models,the design and composition of the software and hardware complex,and automated control and monitoring systems allow solar hot water heating systems to increase the energy efficiency of life support systems and heat supply of buildings by reducing energy consumption for heat supply.The simulation result showed that during the daytime,the temperature of water in the collector is 70°C;the storage of heated water since heated water is cooled at night.We defined that a work period of the system can be extended with high efficiency(April-October)for Almaty region.展开更多
This paper presents an analysis of the operation of a stage of an aircraft engine gas turbine in terms of generation of flow losses. The energy loss coefficient, the entropy loss coefficient and an additional pressure...This paper presents an analysis of the operation of a stage of an aircraft engine gas turbine in terms of generation of flow losses. The energy loss coefficient, the entropy loss coefficient and an additional pressure loss coefficient were adopted to describe the losses quantitatively. Distributions of loss coefficients were presented along the height of the blade channel. All coefficients were determined based on the data from the unsteady flow field and analyzed for different mutual positioning of the stator and rotor blades. The flow calculations were performed using the Ansys CFX commercial software package. The analyses presented in this paper were carried out using the URANS (Unsteady Reynolds-Averaged Navier-Stokes) method and two different turbulence models: the common Shear Stress Transport (SST) model and the Adaptive-Scale Simulation (SAS) turbulence model, which belongs to the group of hybrid models.展开更多
At present,the leakage rate of the water distribution network in China is still high,and the waste of water resources caused by water distribution network leakage is quite serious every year.Therefore,the location of ...At present,the leakage rate of the water distribution network in China is still high,and the waste of water resources caused by water distribution network leakage is quite serious every year.Therefore,the location of pipeline leakage is of great significance for saving water resources and reducing economic losses.Acoustic emission technology is the most widely used pipeline leak location technology.The traditional non-stationary random signal de-noising method mainly relies on the estimation of noise parameters,ignoring periodic noise and components unrelated to pipeline leakage.Aiming at the above problems,this paper proposes a leak location method for water supply pipelines based on a multivariate variational mode decomposition algorithm.This method combines the two parameters of the energy loss coefficient and the correlation coefficient between adjacent modes,and adaptively determines the decomposition mode number K according to the characteristics of the signal itself.According to the correlation coefficient,the effective component is selected to reconstruct the signal and the cross-correlation time delay is estimated to determine the location of the pipeline leakage point.The experimental results show that this method has higher accuracy than the cross-correlation method based on VMD and the cross-correlation method based on EMD,and the average relative positioning error is less than 2.2%.展开更多
The impacts of the cavity leakage flow on the shrouded stator aerodynamic performance were investigated by modelling the annular cascade mainstream with the seal cavity flow path based on the validated numerical metho...The impacts of the cavity leakage flow on the shrouded stator aerodynamic performance were investigated by modelling the annular cascade mainstream with the seal cavity flow path based on the validated numerical method.Meanwhile,the interactions between the cavity leakage and the mainstream were also determined in the current study.The development of hub corner separation under the action of leakage was discussed and the total pressure loss coefficient as well as the entropy-based loss coefficient was employed to evaluate the performance changes at different seal clearances and cavity rotational speeds.The results show that the cavity leakage flow induces a new vortex near the blade leading edge and plays an important role in the development of passage vortex and the size of concentrated shedding vortex.By increasing the seal clearance with more cavity leakage flow rate,an increase in the pitchwise extent of the separation region under 15%span is significant and the total pressure loss in the separation core increases.In addition,with the increase of cavity rotating speed,the starting point of corner separation moves backward,reducing the size and depth of the hub corner separation.The mainstream loss reduction in combination with the entropy increase in the seal cavity causes the entropy-based loss coefficient to perform a trend of decreasing first and then increasing with the cavity speed.展开更多
Orifice plate energy dissipater as well as plug energy dissipater, as a kind of effective energy dissipater with characteristics of simple structure, convenient construction and high energy dissipation ratio, has beco...Orifice plate energy dissipater as well as plug energy dissipater, as a kind of effective energy dissipater with characteristics of simple structure, convenient construction and high energy dissipation ratio, has become welcomed more and more by hydraulics researchers. The two kinds of energy dissipaters with sudden reduction and sudden enlargement forms are similar in energy dissipation mechanism, but there are differences in energy dissipation characteristics and cavitation characteristics. In the present paper, the differences between orifice plate and plug in energy loss coefficient, relating to their energy dissipation ratio, in the backflow region length, relating to their energy loss coefficient, and in the lowest wall pressure coefficient, relating to their cavitations risk, were analyzed by numerical simulations and physical experiment, and their features in above three aspects were also revealed. The results of research in the present paper demonstrate that the backflow region length of orifice plate is longer than that of plug at the same contraction ratio, the lowest wall pressure coefficient of plug is smaller than that of orifice plate at the same contraction ratio, and the energy loss coefficient of orifice plate is bigger than that of plug, which illustrates that plug is superior to orifice plate in resistance cavitation damage at the same contraction ratio.展开更多
Due to the large degree of freedom in terms of design and installation, flexible ventilation ducts are commonly used in ventilation systems. However, excessive use of flexible ducts may lead to greater pressure drop a...Due to the large degree of freedom in terms of design and installation, flexible ventilation ducts are commonly used in ventilation systems. However, excessive use of flexible ducts may lead to greater pressure drop and higher energy consumption. This study conducted experimental measurements to characterize the pressure drop in flexible ventilation ducts with different compression ratios and bending angles. This investigation first measured the pressure drop in straight flexible ducts with four compression ratios under various airflow rates. The calculated friction factor for the straight flexible ducts was negatively associated with the compression ratio. Next, the pressure drops in single-bend flexible ducts with various bending angles from 30° to 150° were measured under various airflow rates. The calculated loss coefficient of the bend increased with the bending angle for single-bend flexible ducts. Finally, the influence of the intermediate duct length on the pressure drop across two bends was experimentally investigated. When the length of the intermediate duct was greater than eight times the inner diameter, the pressure drop across a double-bend flexible duct could be calculated from the friction factors and loss coefficients with a relative error less than 1%. The data obtained in this study can be used to calculate the total pressure loss in flexible ventilation ducting systems in buildings.展开更多
Jet engine manufacturers and designers are seeking for lighter and smaller type of axial compressors.Improving the aerodynamic characteristics of blades is carried out by controlling the boundary layer.One way to cont...Jet engine manufacturers and designers are seeking for lighter and smaller type of axial compressors.Improving the aerodynamic characteristics of blades is carried out by controlling the boundary layer.One way to control the boundary layer is using tandem blades.Tandem-blade cascades are capable of using highly loaded stages for axial compressors because they provide more works than single-blade cascades.In other words,tandem blades help to achieve a specified total pressure ratio with less number of stages.Therefore,one of the most important problems for researchers is to optimize the aerodynamic parameters of tandem blades.Changing the geometrical parameters of blades is a method to achieve this purpose.In this work,the stagger and camber angle of each blade are first changed while the other geometrical parameters such as overall camber,total stagger angle,the axial overlap,percent pitch and chord ratio are fixed.Secondly,the overall camber angle of tandem blade is changed by increasing the difference between the stagger angle of the first and second blade while the type of two airfoils,axial overlap and percent pitch,overall chord length and overall stagger angle are fixed.The aerodynamic performances of the generated tandem-blade cascades are obtained using two-dimensional numerical solution of flow.For this,a viscous turbulent flow solver is used for solving the Navier-Stokes equations.In these simulations,inlet Mach number is fixed to 0.6.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No.40771191).
文摘In this study,calibrations of non-point source(NPS)pollution models are performed based on Black River basin historical real-time runoff data,sedimentation record data,and NPS sources survey information.The concept of NPS loss coefficient for the watershed or the loss coefficients(LC)for simplicity is brought up by examining NPS build-up and migration processes along riverbanks in natural river systems.The historical data is used for determining the nitrogenous NPS loss coefficient for five land use types including farmland,urban land,grassland,shrub land,and forest under different precipitation conditions.The comparison of outputs from Soil and Water Assessment Tool(SWAT)model and coefficient export method showed that both methods could obtain reasonable LC.The high Pearson correlation coefficient(0.94722)between those two sets of calculation results justified the consistency of those two models.Another result in the study is that different combinations of precipitation condition and land use types could significantly affect the calculated loss coefficient.As for the adsorptive nitrogen,the order of impact on LC for different land use types can be sorted as:farm land.urban land.grassland.shrub land.forest while the order was farmland.grass land.shrub land.forest.urban land for soluble nitrogen.
基金Thisworkwas supported by the Ministry of Education and Science of theRepublic of Kazakhstan BR10965172。
文摘In this paper,we studied theoretically and numerically heated losses of a flat solar collector to model the solar water heating system for the Kazakhstan climate condition.For different climatic zones with a growing cost for energy or lack of central heating systems,promising is to find ways to improve the energy efficiency of the solar system.The mathematical model(based on ordinary differential equation)simulated the solar system work process under different conditions.To bridge the modeling and real values results,we studied the important physical parameters such as loss coefficient,Nu,Ra,and Pr values.They impacted the efficiency of flat solar collectors and heat losses of the system.The developed mathematical models,the design and composition of the software and hardware complex,and automated control and monitoring systems allow solar hot water heating systems to increase the energy efficiency of life support systems and heat supply of buildings by reducing energy consumption for heat supply.The simulation result showed that during the daytime,the temperature of water in the collector is 70°C;the storage of heated water since heated water is cooled at night.We defined that a work period of the system can be extended with high efficiency(April-October)for Almaty region.
基金the Polish Ministry of Science and Higher Education for the financial support for the research project UMO-2011/01/B/ST8/03488.
文摘This paper presents an analysis of the operation of a stage of an aircraft engine gas turbine in terms of generation of flow losses. The energy loss coefficient, the entropy loss coefficient and an additional pressure loss coefficient were adopted to describe the losses quantitatively. Distributions of loss coefficients were presented along the height of the blade channel. All coefficients were determined based on the data from the unsteady flow field and analyzed for different mutual positioning of the stator and rotor blades. The flow calculations were performed using the Ansys CFX commercial software package. The analyses presented in this paper were carried out using the URANS (Unsteady Reynolds-Averaged Navier-Stokes) method and two different turbulence models: the common Shear Stress Transport (SST) model and the Adaptive-Scale Simulation (SAS) turbulence model, which belongs to the group of hybrid models.
基金supported by the three funds:Industry-University-research Project of Anhui Jianzhu University HYB20210116National Key Research and Development Project of China No.2017YFC0704100(entitled New Generation Intelligent Building Platform Techniques)Research Project of Anhui Jianzhu University jy2021-c-017(Project Name:Research and Application ofWater Distribution Network Leakage Detection System Based on DMA Partition).
文摘At present,the leakage rate of the water distribution network in China is still high,and the waste of water resources caused by water distribution network leakage is quite serious every year.Therefore,the location of pipeline leakage is of great significance for saving water resources and reducing economic losses.Acoustic emission technology is the most widely used pipeline leak location technology.The traditional non-stationary random signal de-noising method mainly relies on the estimation of noise parameters,ignoring periodic noise and components unrelated to pipeline leakage.Aiming at the above problems,this paper proposes a leak location method for water supply pipelines based on a multivariate variational mode decomposition algorithm.This method combines the two parameters of the energy loss coefficient and the correlation coefficient between adjacent modes,and adaptively determines the decomposition mode number K according to the characteristics of the signal itself.According to the correlation coefficient,the effective component is selected to reconstruct the signal and the cross-correlation time delay is estimated to determine the location of the pipeline leakage point.The experimental results show that this method has higher accuracy than the cross-correlation method based on VMD and the cross-correlation method based on EMD,and the average relative positioning error is less than 2.2%.
基金supported by the National Natural Science Foundation of China(No.52006021,No.52106040)China Postdoctoral Science Foundation(No.2021M690498,No.2021M700648)+3 种基金Natural Science Foundation of Liaoning Province(No.2020-BS-069)Dalian Science and Technology Innovation Fund(No.2021JJ12GX030)the Fundamental Research Funds for the Central Universities(No.3132022210)National Research Center for International Subsea and Engineering Technology and Equipment(No.3132022349)。
文摘The impacts of the cavity leakage flow on the shrouded stator aerodynamic performance were investigated by modelling the annular cascade mainstream with the seal cavity flow path based on the validated numerical method.Meanwhile,the interactions between the cavity leakage and the mainstream were also determined in the current study.The development of hub corner separation under the action of leakage was discussed and the total pressure loss coefficient as well as the entropy-based loss coefficient was employed to evaluate the performance changes at different seal clearances and cavity rotational speeds.The results show that the cavity leakage flow induces a new vortex near the blade leading edge and plays an important role in the development of passage vortex and the size of concentrated shedding vortex.By increasing the seal clearance with more cavity leakage flow rate,an increase in the pitchwise extent of the separation region under 15%span is significant and the total pressure loss in the separation core increases.In addition,with the increase of cavity rotating speed,the starting point of corner separation moves backward,reducing the size and depth of the hub corner separation.The mainstream loss reduction in combination with the entropy increase in the seal cavity causes the entropy-based loss coefficient to perform a trend of decreasing first and then increasing with the cavity speed.
文摘Orifice plate energy dissipater as well as plug energy dissipater, as a kind of effective energy dissipater with characteristics of simple structure, convenient construction and high energy dissipation ratio, has become welcomed more and more by hydraulics researchers. The two kinds of energy dissipaters with sudden reduction and sudden enlargement forms are similar in energy dissipation mechanism, but there are differences in energy dissipation characteristics and cavitation characteristics. In the present paper, the differences between orifice plate and plug in energy loss coefficient, relating to their energy dissipation ratio, in the backflow region length, relating to their energy loss coefficient, and in the lowest wall pressure coefficient, relating to their cavitations risk, were analyzed by numerical simulations and physical experiment, and their features in above three aspects were also revealed. The results of research in the present paper demonstrate that the backflow region length of orifice plate is longer than that of plug at the same contraction ratio, the lowest wall pressure coefficient of plug is smaller than that of orifice plate at the same contraction ratio, and the energy loss coefficient of orifice plate is bigger than that of plug, which illustrates that plug is superior to orifice plate in resistance cavitation damage at the same contraction ratio.
基金This work was partially supported by the Early Career Scheme of Research Grants Council of Hong Kong,China(No.24208518,No.25210419)and the National Natural Science Foundation of China(No.51708474).
文摘Due to the large degree of freedom in terms of design and installation, flexible ventilation ducts are commonly used in ventilation systems. However, excessive use of flexible ducts may lead to greater pressure drop and higher energy consumption. This study conducted experimental measurements to characterize the pressure drop in flexible ventilation ducts with different compression ratios and bending angles. This investigation first measured the pressure drop in straight flexible ducts with four compression ratios under various airflow rates. The calculated friction factor for the straight flexible ducts was negatively associated with the compression ratio. Next, the pressure drops in single-bend flexible ducts with various bending angles from 30° to 150° were measured under various airflow rates. The calculated loss coefficient of the bend increased with the bending angle for single-bend flexible ducts. Finally, the influence of the intermediate duct length on the pressure drop across two bends was experimentally investigated. When the length of the intermediate duct was greater than eight times the inner diameter, the pressure drop across a double-bend flexible duct could be calculated from the friction factors and loss coefficients with a relative error less than 1%. The data obtained in this study can be used to calculate the total pressure loss in flexible ventilation ducting systems in buildings.
文摘Jet engine manufacturers and designers are seeking for lighter and smaller type of axial compressors.Improving the aerodynamic characteristics of blades is carried out by controlling the boundary layer.One way to control the boundary layer is using tandem blades.Tandem-blade cascades are capable of using highly loaded stages for axial compressors because they provide more works than single-blade cascades.In other words,tandem blades help to achieve a specified total pressure ratio with less number of stages.Therefore,one of the most important problems for researchers is to optimize the aerodynamic parameters of tandem blades.Changing the geometrical parameters of blades is a method to achieve this purpose.In this work,the stagger and camber angle of each blade are first changed while the other geometrical parameters such as overall camber,total stagger angle,the axial overlap,percent pitch and chord ratio are fixed.Secondly,the overall camber angle of tandem blade is changed by increasing the difference between the stagger angle of the first and second blade while the type of two airfoils,axial overlap and percent pitch,overall chord length and overall stagger angle are fixed.The aerodynamic performances of the generated tandem-blade cascades are obtained using two-dimensional numerical solution of flow.For this,a viscous turbulent flow solver is used for solving the Navier-Stokes equations.In these simulations,inlet Mach number is fixed to 0.6.
