The cavitation is very common in a centrifugal pump,especially when the speed is very high,and it seriously influences the centrifugal pump performance.In this investigation,the RNG k-ε turbulence model and the cavit...The cavitation is very common in a centrifugal pump,especially when the speed is very high,and it seriously influences the centrifugal pump performance.In this investigation,the RNG k-ε turbulence model and the cavitation model with consideration of the mass transferring are first used to simulate the cavitation performance of the high-speed centrifugal pump without taking any measure for improving the pump cavitation performance.The calculation results reveal that a number of bubbles appear in the centrifugal pump flow channel,and the head as well as the flow rate of the high-speed centrifugal pump are far from its design condition.The cavitation performance can be improved effectively by arranging a variable pitch inducer and adopting an annular nozzle scheme.The flow field analysis of the pump is conducted to obtain the suitable working temperature distribution at different void fractions.On one hand,with the same void fraction,the head of the centrifugal pump drops slowly with the increase of temperature.However,when the temperature exceeds 90°C,the head of the pump drops rapidly.On the other hand,at the constant temperature,the higher the void fraction,the worse the cavitation performance.This research conducted under different temperatures and void fractions provides some guidance for designing an effective high-speed centrifugal pump.展开更多
As the width-thickness ratio of the discrete nozzle atomizer’s discrete hole greatly influences the loss of atomizing gas flow rate,the discrete nozzle atomizer was transformed into an annular slit atomizer with the ...As the width-thickness ratio of the discrete nozzle atomizer’s discrete hole greatly influences the loss of atomizing gas flow rate,the discrete nozzle atomizer was transformed into an annular slit atomizer with the same total nozzle outlet area.A numerical simulation study on the effect of various parameters on the atomization in the annular slit atomizer was carried out by coupling both the large eddy simulation(LES)and volume of fluid(VOF)model,which is based on the applicability of LES in capturing the breakup behavior of transient liquid droplets and the advantage of VOF method in directly capturing the phase interface.The simulation results showed that the increase in the atomization pressure makes the gas gain higher momentum,while the increase in the nozzle intersection angle decreases the distance between the nozzle exit and the computational domain axis.The increase in these two variables results in enhancing the gas-liquid interaction in the primary atomization zone and the formation of more aluminum droplets simultaneously.It is considered that the atomization effect becomes better when atomization pressure is 2.5 MPa,and the nozzle intersection angle is 60°.Industrial tests showed that the aluminum powder prepared by the optimized annular slit atomizer has a finer mean particle size and a higher yield of fine powder.The numerical simulation results agree well with the industrial test data of the powder particle size.展开更多
Recently,by combining a swirl flow with non-equilibrium condensation phenomena of condensate gas generated in a supersonic flow,a separating and extracting techniques of condensate gas have been developed.This techniq...Recently,by combining a swirl flow with non-equilibrium condensation phenomena of condensate gas generated in a supersonic flow,a separating and extracting techniques of condensate gas have been developed.This technique can reduce the size of the device and don't use chemicals.In the present study,by using a non-equilibrium condensation phenomenon of moist air occurred in the supersonic flow in the annular nozzle composed of an inher body and an outer nozzle with a swirl,the possibility of separation of the condensable gas and the effect of shape of nozzle inlet on the flow field were examined numerically.展开更多
Acoustic characteristics of the detonation sound wave generated by a pulse detonation engine with an annular nozzle,including peak sound pressure, directivity, and A duration, are experimentally investigated while uti...Acoustic characteristics of the detonation sound wave generated by a pulse detonation engine with an annular nozzle,including peak sound pressure, directivity, and A duration, are experimentally investigated while utilizing gasoline as fuel and oxygen-enriched air as oxidizer. Three annular nozzle geometries are evaluated by varying the ratio of inner cone diameter to detonation tube exit diameter from 0.36 to 0.68. The experimental results show that the annular nozzles have a significant effect on the acoustic characteristics of the detonation sound wave. The annular nozzles can amplify the peak sound pressure of the detonation sound wave at 90° while reducing it at 0° and 30°. The directivity angle of the detonation sound wave is changed by annular nozzles from 30° to 90°. The A duration of the detonation sound wave at 90° is also increased by the annular nozzles. These changes indicate that the annular nozzles have an important influence on the acoustic energy distribution of the detonation sound wave, which amplify the acoustic energy in a direction perpendicular to the tube axis and weaken it along the direction of the tube axis.展开更多
In recent years,separating and extracting technologies of condensate gas have been developed by combining a swirl flow with non-equilibrium condensation phenomena of condensate gas generated in a supersonic flow.The t...In recent years,separating and extracting technologies of condensate gas have been developed by combining a swirl flow with non-equilibrium condensation phenomena of condensate gas generated in a supersonic flow.The technology can reduce the size of the device and does not use chemicals.However,there are many unresolved problems for performance of the separation,extraction and operating principle.Therefore it is necessary to research further in order to improve the performance of the equipment.In the present study,the numerical study was carried out to clarify the effect of the heterogeneous condensation on the characteristics of the swirling flow field in a supersonic annular nozzle,and the differences between homogeneous condensation and heterogeneous condensation in the flow field.As the results,it is found that the condensation flow with a swirl affects the position of sonic line,the generating position of condensate and the radial distribution ratio of liquid phase.展开更多
基金the National Natural Science Foundation of China (Grant No.51279145).
文摘The cavitation is very common in a centrifugal pump,especially when the speed is very high,and it seriously influences the centrifugal pump performance.In this investigation,the RNG k-ε turbulence model and the cavitation model with consideration of the mass transferring are first used to simulate the cavitation performance of the high-speed centrifugal pump without taking any measure for improving the pump cavitation performance.The calculation results reveal that a number of bubbles appear in the centrifugal pump flow channel,and the head as well as the flow rate of the high-speed centrifugal pump are far from its design condition.The cavitation performance can be improved effectively by arranging a variable pitch inducer and adopting an annular nozzle scheme.The flow field analysis of the pump is conducted to obtain the suitable working temperature distribution at different void fractions.On one hand,with the same void fraction,the head of the centrifugal pump drops slowly with the increase of temperature.However,when the temperature exceeds 90°C,the head of the pump drops rapidly.On the other hand,at the constant temperature,the higher the void fraction,the worse the cavitation performance.This research conducted under different temperatures and void fractions provides some guidance for designing an effective high-speed centrifugal pump.
基金the financial support provided by the National Natural Science Foundation of China(U21A20317)supported by High-Performance Computing Center of Wuhan University of Science and Technology.
文摘As the width-thickness ratio of the discrete nozzle atomizer’s discrete hole greatly influences the loss of atomizing gas flow rate,the discrete nozzle atomizer was transformed into an annular slit atomizer with the same total nozzle outlet area.A numerical simulation study on the effect of various parameters on the atomization in the annular slit atomizer was carried out by coupling both the large eddy simulation(LES)and volume of fluid(VOF)model,which is based on the applicability of LES in capturing the breakup behavior of transient liquid droplets and the advantage of VOF method in directly capturing the phase interface.The simulation results showed that the increase in the atomization pressure makes the gas gain higher momentum,while the increase in the nozzle intersection angle decreases the distance between the nozzle exit and the computational domain axis.The increase in these two variables results in enhancing the gas-liquid interaction in the primary atomization zone and the formation of more aluminum droplets simultaneously.It is considered that the atomization effect becomes better when atomization pressure is 2.5 MPa,and the nozzle intersection angle is 60°.Industrial tests showed that the aluminum powder prepared by the optimized annular slit atomizer has a finer mean particle size and a higher yield of fine powder.The numerical simulation results agree well with the industrial test data of the powder particle size.
文摘Recently,by combining a swirl flow with non-equilibrium condensation phenomena of condensate gas generated in a supersonic flow,a separating and extracting techniques of condensate gas have been developed.This technique can reduce the size of the device and don't use chemicals.In the present study,by using a non-equilibrium condensation phenomenon of moist air occurred in the supersonic flow in the annular nozzle composed of an inher body and an outer nozzle with a swirl,the possibility of separation of the condensable gas and the effect of shape of nozzle inlet on the flow field were examined numerically.
基金Project supported by the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20220919)the National Key Laboratory of Transient Physics Foundation Project, China (Grants No. 6142604210203)。
文摘Acoustic characteristics of the detonation sound wave generated by a pulse detonation engine with an annular nozzle,including peak sound pressure, directivity, and A duration, are experimentally investigated while utilizing gasoline as fuel and oxygen-enriched air as oxidizer. Three annular nozzle geometries are evaluated by varying the ratio of inner cone diameter to detonation tube exit diameter from 0.36 to 0.68. The experimental results show that the annular nozzles have a significant effect on the acoustic characteristics of the detonation sound wave. The annular nozzles can amplify the peak sound pressure of the detonation sound wave at 90° while reducing it at 0° and 30°. The directivity angle of the detonation sound wave is changed by annular nozzles from 30° to 90°. The A duration of the detonation sound wave at 90° is also increased by the annular nozzles. These changes indicate that the annular nozzles have an important influence on the acoustic energy distribution of the detonation sound wave, which amplify the acoustic energy in a direction perpendicular to the tube axis and weaken it along the direction of the tube axis.
文摘In recent years,separating and extracting technologies of condensate gas have been developed by combining a swirl flow with non-equilibrium condensation phenomena of condensate gas generated in a supersonic flow.The technology can reduce the size of the device and does not use chemicals.However,there are many unresolved problems for performance of the separation,extraction and operating principle.Therefore it is necessary to research further in order to improve the performance of the equipment.In the present study,the numerical study was carried out to clarify the effect of the heterogeneous condensation on the characteristics of the swirling flow field in a supersonic annular nozzle,and the differences between homogeneous condensation and heterogeneous condensation in the flow field.As the results,it is found that the condensation flow with a swirl affects the position of sonic line,the generating position of condensate and the radial distribution ratio of liquid phase.
