The double casing warhead with sandwiched charge is a novel fragmentation warhead that can produce two groups of fragments with different velocity,and the previous work has presented a calculation formula to determine...The double casing warhead with sandwiched charge is a novel fragmentation warhead that can produce two groups of fragments with different velocity,and the previous work has presented a calculation formula to determine the maximum fragment velocity.The current work builds on the published formula to further develop a formula for calculating the axial distribution characteristics of the fragment velocity.For this type of warhead,the simulation of the dispersion characteristics of the detonation products at different positions shows that the detonation products at the ends have a much larger axial velocity than those in the middle,and the detonation products have a greater axial dispersion velocity when they are closer to the central axis.The loading process and the fragment velocity vary with the axial position for both casing layers,and the total velocity of the fragments is the vector sum of the radial velocity and the axial velocity.At the same axial position,the acceleration time of the inner casing is greater than that of the outer casing.For the same casing,the fragments generated at the ends have a longer acceleration time than the fragments from the middle.The proposed formula is validated with the X-ray radiography results of the four warheads previously tested experimentally and the 3D smoothedparticle hydrodynamics numerical simulation results of several series of new warheads with different configurations.The formula can accurately and reliably calculate the fragment velocity when the lengthto-diameter ratio of the charge is greater than 1.5 and the thickness of the casing is less than 20%its inner radius.This work thus provides a key reference for the theoretical analysis and the design of warheads with multiple casings.展开更多
In heavy oil production,the loss of energy to ambient surroundings decreases the temperature of the heavy oil flowing upwards in a vertical wellbore,which increases the oil viscosity and the oil may not flow normally ...In heavy oil production,the loss of energy to ambient surroundings decreases the temperature of the heavy oil flowing upwards in a vertical wellbore,which increases the oil viscosity and the oil may not flow normally in the wellbore.Therefore,it is necessary to lower the heavy oil viscosity by heating methods to allow it to be lifted easily.Heating of heavy oil in an oil well is achieved by circulating hot water in annuli in the well（tubing-casing annulus,casing-casing annulus）.In this paper,based on heat transfer principles and fluid flow theory,a model is developed for produced fluids and hot water flowing in a vertical wellbore.The temperature and pressure of produced fluids and hot water in the wellbore are calculated and the effect of hot water on heavy oil temperature is analyzed.Calculated results show that the hot water circulating in the annuli may effectively heat the heavy oil in the tubing,so as to significantly reduce both oil viscosity and resistance to oil flow.展开更多
At present,the aeration-assisted cutting-carrying technology is faced with complexities in the drilling of CBM multi-branch horizontal wells.For example,the aerating pressure is hardly maintained,and the borehole inst...At present,the aeration-assisted cutting-carrying technology is faced with complexities in the drilling of CBM multi-branch horizontal wells.For example,the aerating pressure is hardly maintained,and the borehole instability may happen.In view of these prominent problems,the technology of double casing tubes&a binary cycle system suitable for CBM multi-branch horizontal wells was developed according to the Venturi principle by means of parasitic tube insufflation which is used for well control simulation system.Then,a multiphase flow finite element model was established for the fluid-cutting particle system in this drilling condition.This technology was tested in field.Double-casing tubes cementing is adopted in this technology and a jet generator is installed at the bottom of the inner casing.In the process of drilling,the drilling fluid injected through double intermediate casing annulus is converted by the jet generator into a high-efficiency steering water jet,which,together with the water jet generated by the bit nozzle,increases the fluid returning rate in the inner annulus space.It is indicated from simulation results that the cutting-carrying effect is the best when the included angle between the nozzle of the jet generator and the vertical direction is 30°.Besides,the influential laws of cutting size,primary cycle volume,accessory cycle volume and drilling velocity on hole cleaning are figured out.It is concluded that this technology increases the flow rate of drilling fluid in annulus space,the returning rate of drilling fluid significantly and the cutting-carrying capacity.It is currently one of the effective hole cleaning technologies for CBM multi-branch horizontal wells where fresh water is taken as the drilling fluid.展开更多
Latent heat storage technology plays a critical role in storing and utilizing geothermal energy.By combining cascaded phase change materials(PCM)with mine filling technologies,mine geothermal energy can be stored ther...Latent heat storage technology plays a critical role in storing and utilizing geothermal energy.By combining cascaded phase change materials(PCM)with mine filling technologies,mine geothermal energy can be stored thermally more effectively.Therefore,this paper designed a physical model of double casing cascaded latent heat storage(CLHS)system in mine.Paraffin RT28 and RT35 were encapsulated in annular gap 1 and annular gap 2,respectively,and this backfill mode was defined as Case 1.The scheme whose backfill sequences of the two PCM were exchanged is defined as Case 2.The heat transfer process of backfill body and PCM was simulated and analyzed by using FLUENT software,and compared with the single stage latent heat storage process.The temperature,liquid fraction(LF),heat transfer capacity,and heat transfer rate were used to evaluate the thermal properties of the CLHS process.It was necessary to study the effect of the filling sequence of PCMs on the heat storage and release process of the backfill body using these results as a starting point.The results show that the main factor affecting latent heat storage in cascaded system is the heat transfer of surrounding rock.Compared with the single-stage heat storage process,the heat storage time of cascaded heat storage process is reduced by 73 min,which is significantly decreased by 20.9%.Moreover,the whole liquid phase fraction(β)of the single-stage has little change during the heat release,while the PCM of the cascaded heat release process can fully release the latent heat.In terms of layout order of PCM,compared with Case 1,the latent heat storage time of Case 2 is increased by about 40 min,and the heat release rate(ε_(s))is significantly lower than that of Case 1.In the initial heat release stage,the heat release rate of Case 2 reaches 95.6 W,which is 30.6%lower than that of Case 1.In comparison,the heat storage and release effect of Case 1 is better than that of Case 2.This paper provides a reference for the improvement of heat storage and release rate of the backfill coupled cascaded latent heat storage system(BCCLHS).展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11872121)。
文摘The double casing warhead with sandwiched charge is a novel fragmentation warhead that can produce two groups of fragments with different velocity,and the previous work has presented a calculation formula to determine the maximum fragment velocity.The current work builds on the published formula to further develop a formula for calculating the axial distribution characteristics of the fragment velocity.For this type of warhead,the simulation of the dispersion characteristics of the detonation products at different positions shows that the detonation products at the ends have a much larger axial velocity than those in the middle,and the detonation products have a greater axial dispersion velocity when they are closer to the central axis.The loading process and the fragment velocity vary with the axial position for both casing layers,and the total velocity of the fragments is the vector sum of the radial velocity and the axial velocity.At the same axial position,the acceleration time of the inner casing is greater than that of the outer casing.For the same casing,the fragments generated at the ends have a longer acceleration time than the fragments from the middle.The proposed formula is validated with the X-ray radiography results of the four warheads previously tested experimentally and the 3D smoothedparticle hydrodynamics numerical simulation results of several series of new warheads with different configurations.The formula can accurately and reliably calculate the fragment velocity when the lengthto-diameter ratio of the charge is greater than 1.5 and the thickness of the casing is less than 20%its inner radius.This work thus provides a key reference for the theoretical analysis and the design of warheads with multiple casings.
基金supported by the Fundamental Research Funds for the Central Universities (No. 27R1015025A)the Natural Science Foundation of Shandong Province,China(Grant No. 05J10150300)
文摘In heavy oil production,the loss of energy to ambient surroundings decreases the temperature of the heavy oil flowing upwards in a vertical wellbore,which increases the oil viscosity and the oil may not flow normally in the wellbore.Therefore,it is necessary to lower the heavy oil viscosity by heating methods to allow it to be lifted easily.Heating of heavy oil in an oil well is achieved by circulating hot water in annuli in the well（tubing-casing annulus,casing-casing annulus）.In this paper,based on heat transfer principles and fluid flow theory,a model is developed for produced fluids and hot water flowing in a vertical wellbore.The temperature and pressure of produced fluids and hot water in the wellbore are calculated and the effect of hot water on heavy oil temperature is analyzed.Calculated results show that the hot water circulating in the annuli may effectively heat the heavy oil in the tubing,so as to significantly reduce both oil viscosity and resistance to oil flow.
基金supported by the National Science and Technology Major Project(No.2011ZX05061).
文摘At present,the aeration-assisted cutting-carrying technology is faced with complexities in the drilling of CBM multi-branch horizontal wells.For example,the aerating pressure is hardly maintained,and the borehole instability may happen.In view of these prominent problems,the technology of double casing tubes&a binary cycle system suitable for CBM multi-branch horizontal wells was developed according to the Venturi principle by means of parasitic tube insufflation which is used for well control simulation system.Then,a multiphase flow finite element model was established for the fluid-cutting particle system in this drilling condition.This technology was tested in field.Double-casing tubes cementing is adopted in this technology and a jet generator is installed at the bottom of the inner casing.In the process of drilling,the drilling fluid injected through double intermediate casing annulus is converted by the jet generator into a high-efficiency steering water jet,which,together with the water jet generated by the bit nozzle,increases the fluid returning rate in the inner annulus space.It is indicated from simulation results that the cutting-carrying effect is the best when the included angle between the nozzle of the jet generator and the vertical direction is 30°.Besides,the influential laws of cutting size,primary cycle volume,accessory cycle volume and drilling velocity on hole cleaning are figured out.It is concluded that this technology increases the flow rate of drilling fluid in annulus space,the returning rate of drilling fluid significantly and the cutting-carrying capacity.It is currently one of the effective hole cleaning technologies for CBM multi-branch horizontal wells where fresh water is taken as the drilling fluid.
基金supported by the National Natural Science Foundation of China(Nos.52104148,52274063)the China Postdoctoral Science Foundation(No.2021M692593)Natural resources comprehensive utilization of coal resources exploration and key laboratory open topic,KF2024-168。
文摘Latent heat storage technology plays a critical role in storing and utilizing geothermal energy.By combining cascaded phase change materials(PCM)with mine filling technologies,mine geothermal energy can be stored thermally more effectively.Therefore,this paper designed a physical model of double casing cascaded latent heat storage(CLHS)system in mine.Paraffin RT28 and RT35 were encapsulated in annular gap 1 and annular gap 2,respectively,and this backfill mode was defined as Case 1.The scheme whose backfill sequences of the two PCM were exchanged is defined as Case 2.The heat transfer process of backfill body and PCM was simulated and analyzed by using FLUENT software,and compared with the single stage latent heat storage process.The temperature,liquid fraction(LF),heat transfer capacity,and heat transfer rate were used to evaluate the thermal properties of the CLHS process.It was necessary to study the effect of the filling sequence of PCMs on the heat storage and release process of the backfill body using these results as a starting point.The results show that the main factor affecting latent heat storage in cascaded system is the heat transfer of surrounding rock.Compared with the single-stage heat storage process,the heat storage time of cascaded heat storage process is reduced by 73 min,which is significantly decreased by 20.9%.Moreover,the whole liquid phase fraction(β)of the single-stage has little change during the heat release,while the PCM of the cascaded heat release process can fully release the latent heat.In terms of layout order of PCM,compared with Case 1,the latent heat storage time of Case 2 is increased by about 40 min,and the heat release rate(ε_(s))is significantly lower than that of Case 1.In the initial heat release stage,the heat release rate of Case 2 reaches 95.6 W,which is 30.6%lower than that of Case 1.In comparison,the heat storage and release effect of Case 1 is better than that of Case 2.This paper provides a reference for the improvement of heat storage and release rate of the backfill coupled cascaded latent heat storage system(BCCLHS).
