In this study, an orthogonal array experiment is conducted by using a transparent fracture network replica. Image processing and theoretical analysis are performed to investigate the model sealing efficiency(SE), fact...In this study, an orthogonal array experiment is conducted by using a transparent fracture network replica. Image processing and theoretical analysis are performed to investigate the model sealing efficiency(SE), factors influencing SE, and the effect of flowing water on propagation. The results show that grout propagation can be classified into three patterns in the fracture network: sealing off, partial sealing,and major erosion. The factors controlling the SE in a descending order of the amount of influence are the initial water flow speed, fracture aperture, grout take, and gel time. An optimal value for the combination of the gel time and grout take(artificial factors) can result in a good SE. The grouting and seepage pressures are measured, and the results reveal that their variations can indicate the SE to some extent. The SE is good when the seepage pressure at each point increases overall;the frequent fluctuations in the seepage pressure indicate a moderately poor SE, and an overall decline in the seepage pressure indicates a major erosion type. The deflection effect of grouting shows an approximately elliptical propagation with the long axis expanding along the wider fracture opening, demonstrating further application in grouting design.展开更多
Precipitation or dissolution due to geochemical reactions has been observed in the caprocks for CO_(2)geosequestration.Geochemical reactions modify the caprock sealing efficiency with self-limiting or self-enhancement...Precipitation or dissolution due to geochemical reactions has been observed in the caprocks for CO_(2)geosequestration.Geochemical reactions modify the caprock sealing efficiency with self-limiting or self-enhancement.However,the effect of this modification on the caprock sealing efficiency has not been fully investigated through multiphysical-geochemical coupling analysis.In this study,a multiphysical-geochemical coupling model was proposed to analyze caprock sealing efficiency.This coupling model considered the full couplings of caprock deformation,two-phase flow,CO_(2)concentration diffusion,geochemical reaction,and CO_(2)sorption.The two-phase flow only occurs in the fracture network and the CO_(2)may partially dissolve into water and diffuse through the concentration difference.The dissolved CO_(2)has geochemical reactions with some critical minerals,thus altering flow channels.The CO_(2)in the fracture network diffuses into matrix,causing the matrix swelling.This fully coupling model was validated with a penetration experiment on a cement cube and compared with two other models for CO_(2)storage plumes.Finally,the effects of geochemical reactions on penetration depth and pore pressure were studied through parametric study.The numerical simulations reveal that the coupling of geochemical reactions and matrix diffusion significantly affect the caprock sealing efficiency.Geochemical reactions occur at a short time after the arrival of CO_(2)concentration and modify the fracture porosity.The CO_(2)diffusion into the matrix requires a much longer time and mainly induces matrix swelling.These effects may produce selfenhancement or self-limiting depending on the flow rate in the fracture network,thus significantly modifying caprock sealing efficiency.展开更多
In modern aero-engine,the turbine rim seals whose purpose is to reduce the ingress are located in a complex flow region between the mainstream and secondary air flows.The sealing air discharged from the compressor of ...In modern aero-engine,the turbine rim seals whose purpose is to reduce the ingress are located in a complex flow region between the mainstream and secondary air flows.The sealing air discharged from the compressor of engine is used to purge turbine cavity.In order to examine the effects of ingress through four distinct rim seals,a one-stage test rig was used in the experiments presented in this work.At a Reynolds number of 5.16×10^(5) in the mainstream and(0.85-2.13)×10^(6) in the rotational,the radial pressure distribution on the stator was determined.To assess flow characteristics and sealing efficacy,measurements of the swirl ratio and CO_(2) concentration were made.The reliability of turbine rim-seals is determined by the locations of the hook and teeth,as well as their effect on hot gas ingestion.To evaluate the performance of four types of seals:a datum double-rim seal and three derivatives with different clearances,the data are employed.Due to the inlet air position,the swirl ratio exhibited a pronounced inflection for all the rim seals.The sealing efficiency can be decreased by putting the hook closer to the rim or by taking the teeth out.Static pressure measurements in the turbine cavity indicate that the seal position has a significant impact.The analysis results revealed that the existence of slot vortex is beneficial to improving efficiency.展开更多
The windage loss caused by protrusion in a rotor–stator cavity has been studied in detail,and there are abundant fitting formulas that have been summarized to calculate the moment coefficients.Some other theorists ha...The windage loss caused by protrusion in a rotor–stator cavity has been studied in detail,and there are abundant fitting formulas that have been summarized to calculate the moment coefficients.Some other theorists have emphasized its effect on the sealing efficiency,proposing that installation of protrusion could alleviate gas ingestion.However,the protrusion shape which is an influential factor on the sealing efficiency has not been focused in previous research.Using the experimental method of measuring CO2 volume fraction,cavity pressure,and power consumption,we investigated the effects of several typical protrusion shapes on various parameters for two sealing structures,in order to obtain the optimal shape.Results showed that a variation of the protrusion shape had little impact on the static pressure,but the total pressure and the sealing efficiency increased in different degrees.Furthermore,even though the hexagon shape resulted in the highest sealing efficiency,we observed that the drop shape had the best overall performance in all of the eight models,which could result in higher efficiency of the turbine cavity.The combination of a radial seal structure and protrusion could improve sealing efficiency better.展开更多
Groundwater inrush is a hazard that always occurs during underground mining.Grouting is one of the most effective processes to seal underground water inflow for hazard prevention.In this study,grouting experiments are...Groundwater inrush is a hazard that always occurs during underground mining.Grouting is one of the most effective processes to seal underground water inflow for hazard prevention.In this study,grouting experiments are conducted by using a visualized transparent single-fracture replica with plane roughness.Image processing and analysis are performed to investigate the thermo–hydro–mechanical coupling effect on the grouting diffusion under coal mine flowing water conditions.The results show that higher ambient temperature leads to shorter initial gel time of chemical grout and leads to a better relative sealing efficiency in the case of a lower flow rate.However,with a higher water flow rate,the relative sealing efficiency is gradually reduced under higher temperature conditions.The grouting pressure,the seepage pressure,and the temperature are measured.The results reveal that the seepage pressure shows a positive correlation with the grouting pressure,while the temperature change shows a negative correlation with the seepage pressure and the grouting pressure.The“equivalent grouting point offset”effect of grouting shows an eccentric elliptical diffusion with larger grouting distance and width under lower temperature conditions.展开更多
The rim seal is used to prevent mainstream ingestion to the gap between the vane of a turbine and its blade. In this article, the dolphin lip with a hook configuration and a large seal cavity with hook structures are ...The rim seal is used to prevent mainstream ingestion to the gap between the vane of a turbine and its blade. In this article, the dolphin lip with a hook configuration and a large seal cavity with hook structures are designed based on the high-pressure turbine datum single shark lip rim seal configuration. The sealing effect and parameters of the flow field are measured by an experiment method and a numerical simulation is used to explain the mechanism. For three configurations,the effect of the leakage slot vortex on the efficiency of the seal and the influence of leakage vortex,generated by the interaction between purge flow and mainstream flow, are discussed in depth. The result shows that the reverse vortex formed by the dolphin lip rim seal with hook structure will increase the sealing efficiency. The seal configuration with a large cavity improves sealing efficiency to a greater extent than the datum structure. At different purge flow rates and with unequal seal structures, the purge flow produces three types of leakage vortices in the passage. Besides, the seal configuration with dolphin lip produces a Kelvin-Helmholtz instability at the interface of the purge and the mainstream flows at a low purge flow rate to induce new leakage vortex branches in the passage of the blade.展开更多
In this paper, the effect of different amount of protrusion on various parameters in rotor–stator system was experimentally studied by measuring CO_2 concentration and pressure, in order to obtain the optimal protrus...In this paper, the effect of different amount of protrusion on various parameters in rotor–stator system was experimentally studied by measuring CO_2 concentration and pressure, in order to obtain the optimal protrusion amount.The parameters of different dimensionless sealing flow were measured under the condition that the annulus Reynolds number was 4.39 × 10~5 and the rotating Reynolds number was 1.05 × 10~6.The results show that the change of the amount of protrusions has little effect on the static pressure in the cavity, and the static pressure change near the sealing ring is almost negligible.But the total pressure and sealing efficiency increase first and then decrease with the increase of the amount of protrusion.The variation of power consumption is the same.A complex vortex structure will appear at the high radius region when the protrusion is installed.On the other hand, the protrusion can effectively reduce the minimum sealing flow of the rotor–stator cavity.Furthermore, considering the sealing efficiency and power consumption,the best range of the protrusion amount is about 36.The ratio near this range can optimally balance the alleviation of the gas ingestion and the reduction of the power consumption.展开更多
Caprock is a water-saturated formation with a sufficient entry capillary pressure to prevent the upward migration of a buoyant fluid. When the entry capillary pressure of caprock is smaller than the pressure exerted b...Caprock is a water-saturated formation with a sufficient entry capillary pressure to prevent the upward migration of a buoyant fluid. When the entry capillary pressure of caprock is smaller than the pressure exerted by the buoyant CO2plume, CO2gradually penetrates into the caprock. The CO2penetration depth into a caprock layer can be used to measure the caprock sealing efficiency and becomes the key issue to the assessment of caprock sealing efficiency. On the other hand, our numerical simulations on a caprock layer have revealed that a square root law for time and pore pressure exists for the CO2penetration into the caprock layer. Based on this finding, this study proposes a simple approach to estimate the CO2penetration depth into a caprock layer. This simple approach is initially developed to consider the speed of CO2invading front. It explicitly expresses the penetration depth with pressuring time, pressure difference and pressure magnitude. This simple approach is then used to fit three sets of experimental data and good fittings are observed regardless of pressures, strengths of porous media, and pore fluids(water,hydrochloric acid, and carbonic acid). Finally, theoretical analyses are conducted to explore those factors affecting CO2penetration depth. The effects of capillary pressure, gas sorption induced swelling, and fluid property are then included in this simple approach. These results show that this simple approach can predict the penetration depth into a caprock layer with sufficient accuracy, even if complicated interactions in penetration process are not explicitly expressed in this simple formula.展开更多
Purge flow is of great importance in cooling turbine disks and sealing rotor-stator disc cavity to reduce hot gas ingestion in gas turbines.The amount of cooling air extracted from the compressor is crucial to engine ...Purge flow is of great importance in cooling turbine disks and sealing rotor-stator disc cavity to reduce hot gas ingestion in gas turbines.The amount of cooling air extracted from the compressor is crucial to engine efficiency.Excessive sealing air will cause not only a reduction in work transfer but also an increase in aerodynamic losses caused by the mixing of main and sealing flow.In order to simplify rim seal structure while ensuring high sealing efficiency,the current paper optimizes the flow path of the secondary air system and presents a new rim seal structure with auxiliary sealing holes transporting a certain amount of secondary sealing flow.The new structure was compared with the conventional counterpart using validated CFD methods,showing that the additional secondary sealing flow is possible to improve sealing efficiency in disk cavity.The current paper investigates the secondary sealing flow with and without swirl(the angle of auxiliary sealing hole inclination is 0°and 45°respectively),while maintaining the total amount of the sealing flow,flowrate ratio of sealing air(main sealing flow rate versus secondary sealing flow rate=1:1,2:1,3:1,4:1),found that both two parameters have essential impacts on sealing efficiency.The relationship between these two parameters and sealing efficiency was obtained,and it provides a new philosophy for the design of rim seal in gas turbines.展开更多
基金supported by the Natural Science Foundation of China under (Nos. 42172293, 4190020747, and 41472268)。
文摘In this study, an orthogonal array experiment is conducted by using a transparent fracture network replica. Image processing and theoretical analysis are performed to investigate the model sealing efficiency(SE), factors influencing SE, and the effect of flowing water on propagation. The results show that grout propagation can be classified into three patterns in the fracture network: sealing off, partial sealing,and major erosion. The factors controlling the SE in a descending order of the amount of influence are the initial water flow speed, fracture aperture, grout take, and gel time. An optimal value for the combination of the gel time and grout take(artificial factors) can result in a good SE. The grouting and seepage pressures are measured, and the results reveal that their variations can indicate the SE to some extent. The SE is good when the seepage pressure at each point increases overall;the frequent fluctuations in the seepage pressure indicate a moderately poor SE, and an overall decline in the seepage pressure indicates a major erosion type. The deflection effect of grouting shows an approximately elliptical propagation with the long axis expanding along the wider fracture opening, demonstrating further application in grouting design.
基金National Natural Science Foundation of China,Grant/Award Number:51674246Creative Research and Development Group Program of Jiangsu Province,Grant/Award Number:2014-27。
文摘Precipitation or dissolution due to geochemical reactions has been observed in the caprocks for CO_(2)geosequestration.Geochemical reactions modify the caprock sealing efficiency with self-limiting or self-enhancement.However,the effect of this modification on the caprock sealing efficiency has not been fully investigated through multiphysical-geochemical coupling analysis.In this study,a multiphysical-geochemical coupling model was proposed to analyze caprock sealing efficiency.This coupling model considered the full couplings of caprock deformation,two-phase flow,CO_(2)concentration diffusion,geochemical reaction,and CO_(2)sorption.The two-phase flow only occurs in the fracture network and the CO_(2)may partially dissolve into water and diffuse through the concentration difference.The dissolved CO_(2)has geochemical reactions with some critical minerals,thus altering flow channels.The CO_(2)in the fracture network diffuses into matrix,causing the matrix swelling.This fully coupling model was validated with a penetration experiment on a cement cube and compared with two other models for CO_(2)storage plumes.Finally,the effects of geochemical reactions on penetration depth and pore pressure were studied through parametric study.The numerical simulations reveal that the coupling of geochemical reactions and matrix diffusion significantly affect the caprock sealing efficiency.Geochemical reactions occur at a short time after the arrival of CO_(2)concentration and modify the fracture porosity.The CO_(2)diffusion into the matrix requires a much longer time and mainly induces matrix swelling.These effects may produce selfenhancement or self-limiting depending on the flow rate in the fracture network,thus significantly modifying caprock sealing efficiency.
基金the financial support of the Science Center for Gas Turbine Project,China(No.P2022-A-Ⅱ-007-001).
文摘In modern aero-engine,the turbine rim seals whose purpose is to reduce the ingress are located in a complex flow region between the mainstream and secondary air flows.The sealing air discharged from the compressor of engine is used to purge turbine cavity.In order to examine the effects of ingress through four distinct rim seals,a one-stage test rig was used in the experiments presented in this work.At a Reynolds number of 5.16×10^(5) in the mainstream and(0.85-2.13)×10^(6) in the rotational,the radial pressure distribution on the stator was determined.To assess flow characteristics and sealing efficacy,measurements of the swirl ratio and CO_(2) concentration were made.The reliability of turbine rim-seals is determined by the locations of the hook and teeth,as well as their effect on hot gas ingestion.To evaluate the performance of four types of seals:a datum double-rim seal and three derivatives with different clearances,the data are employed.Due to the inlet air position,the swirl ratio exhibited a pronounced inflection for all the rim seals.The sealing efficiency can be decreased by putting the hook closer to the rim or by taking the teeth out.Static pressure measurements in the turbine cavity indicate that the seal position has a significant impact.The analysis results revealed that the existence of slot vortex is beneficial to improving efficiency.
文摘The windage loss caused by protrusion in a rotor–stator cavity has been studied in detail,and there are abundant fitting formulas that have been summarized to calculate the moment coefficients.Some other theorists have emphasized its effect on the sealing efficiency,proposing that installation of protrusion could alleviate gas ingestion.However,the protrusion shape which is an influential factor on the sealing efficiency has not been focused in previous research.Using the experimental method of measuring CO2 volume fraction,cavity pressure,and power consumption,we investigated the effects of several typical protrusion shapes on various parameters for two sealing structures,in order to obtain the optimal shape.Results showed that a variation of the protrusion shape had little impact on the static pressure,but the total pressure and the sealing efficiency increased in different degrees.Furthermore,even though the hexagon shape resulted in the highest sealing efficiency,we observed that the drop shape had the best overall performance in all of the eight models,which could result in higher efficiency of the turbine cavity.The combination of a radial seal structure and protrusion could improve sealing efficiency better.
基金National Natural Science Foundation of China,Grant/Award Number:41902292。
文摘Groundwater inrush is a hazard that always occurs during underground mining.Grouting is one of the most effective processes to seal underground water inflow for hazard prevention.In this study,grouting experiments are conducted by using a visualized transparent single-fracture replica with plane roughness.Image processing and analysis are performed to investigate the thermo–hydro–mechanical coupling effect on the grouting diffusion under coal mine flowing water conditions.The results show that higher ambient temperature leads to shorter initial gel time of chemical grout and leads to a better relative sealing efficiency in the case of a lower flow rate.However,with a higher water flow rate,the relative sealing efficiency is gradually reduced under higher temperature conditions.The grouting pressure,the seepage pressure,and the temperature are measured.The results reveal that the seepage pressure shows a positive correlation with the grouting pressure,while the temperature change shows a negative correlation with the seepage pressure and the grouting pressure.The“equivalent grouting point offset”effect of grouting shows an eccentric elliptical diffusion with larger grouting distance and width under lower temperature conditions.
基金Financial support for the work presented is provided by the National Natural Science Foundation of China (Nos.51876202 and 51836008)。
文摘The rim seal is used to prevent mainstream ingestion to the gap between the vane of a turbine and its blade. In this article, the dolphin lip with a hook configuration and a large seal cavity with hook structures are designed based on the high-pressure turbine datum single shark lip rim seal configuration. The sealing effect and parameters of the flow field are measured by an experiment method and a numerical simulation is used to explain the mechanism. For three configurations,the effect of the leakage slot vortex on the efficiency of the seal and the influence of leakage vortex,generated by the interaction between purge flow and mainstream flow, are discussed in depth. The result shows that the reverse vortex formed by the dolphin lip rim seal with hook structure will increase the sealing efficiency. The seal configuration with a large cavity improves sealing efficiency to a greater extent than the datum structure. At different purge flow rates and with unequal seal structures, the purge flow produces three types of leakage vortices in the passage. Besides, the seal configuration with dolphin lip produces a Kelvin-Helmholtz instability at the interface of the purge and the mainstream flows at a low purge flow rate to induce new leakage vortex branches in the passage of the blade.
文摘In this paper, the effect of different amount of protrusion on various parameters in rotor–stator system was experimentally studied by measuring CO_2 concentration and pressure, in order to obtain the optimal protrusion amount.The parameters of different dimensionless sealing flow were measured under the condition that the annulus Reynolds number was 4.39 × 10~5 and the rotating Reynolds number was 1.05 × 10~6.The results show that the change of the amount of protrusions has little effect on the static pressure in the cavity, and the static pressure change near the sealing ring is almost negligible.But the total pressure and sealing efficiency increase first and then decrease with the increase of the amount of protrusion.The variation of power consumption is the same.A complex vortex structure will appear at the high radius region when the protrusion is installed.On the other hand, the protrusion can effectively reduce the minimum sealing flow of the rotor–stator cavity.Furthermore, considering the sealing efficiency and power consumption,the best range of the protrusion amount is about 36.The ratio near this range can optimally balance the alleviation of the gas ingestion and the reduction of the power consumption.
基金the financial support from the Creative Research and Development Group Program of Jiangsu Province(2014-27)the National Science Fund for Distinguished Young Scholars(Grant No.51125017)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD2014)
文摘Caprock is a water-saturated formation with a sufficient entry capillary pressure to prevent the upward migration of a buoyant fluid. When the entry capillary pressure of caprock is smaller than the pressure exerted by the buoyant CO2plume, CO2gradually penetrates into the caprock. The CO2penetration depth into a caprock layer can be used to measure the caprock sealing efficiency and becomes the key issue to the assessment of caprock sealing efficiency. On the other hand, our numerical simulations on a caprock layer have revealed that a square root law for time and pore pressure exists for the CO2penetration into the caprock layer. Based on this finding, this study proposes a simple approach to estimate the CO2penetration depth into a caprock layer. This simple approach is initially developed to consider the speed of CO2invading front. It explicitly expresses the penetration depth with pressuring time, pressure difference and pressure magnitude. This simple approach is then used to fit three sets of experimental data and good fittings are observed regardless of pressures, strengths of porous media, and pore fluids(water,hydrochloric acid, and carbonic acid). Finally, theoretical analyses are conducted to explore those factors affecting CO2penetration depth. The effects of capillary pressure, gas sorption induced swelling, and fluid property are then included in this simple approach. These results show that this simple approach can predict the penetration depth into a caprock layer with sufficient accuracy, even if complicated interactions in penetration process are not explicitly expressed in this simple formula.
基金National Natural Science Foundation of China for their financial support(Grant No.51776200)The Innovation Promotion Association,Chinese Academy of Sciences is also thanked for the support and help。
文摘Purge flow is of great importance in cooling turbine disks and sealing rotor-stator disc cavity to reduce hot gas ingestion in gas turbines.The amount of cooling air extracted from the compressor is crucial to engine efficiency.Excessive sealing air will cause not only a reduction in work transfer but also an increase in aerodynamic losses caused by the mixing of main and sealing flow.In order to simplify rim seal structure while ensuring high sealing efficiency,the current paper optimizes the flow path of the secondary air system and presents a new rim seal structure with auxiliary sealing holes transporting a certain amount of secondary sealing flow.The new structure was compared with the conventional counterpart using validated CFD methods,showing that the additional secondary sealing flow is possible to improve sealing efficiency in disk cavity.The current paper investigates the secondary sealing flow with and without swirl(the angle of auxiliary sealing hole inclination is 0°and 45°respectively),while maintaining the total amount of the sealing flow,flowrate ratio of sealing air(main sealing flow rate versus secondary sealing flow rate=1:1,2:1,3:1,4:1),found that both two parameters have essential impacts on sealing efficiency.The relationship between these two parameters and sealing efficiency was obtained,and it provides a new philosophy for the design of rim seal in gas turbines.
