Impinging-jet injectors are widely used in liquid propulsion applications, since their simple configuration provides reliable and efficient atomization. The flowfield involves a series of complicated spatio-temporal e...Impinging-jet injectors are widely used in liquid propulsion applications, since their simple configuration provides reliable and efficient atomization. The flowfield involves a series of complicated spatio-temporal evolutions. Much effort has been directed toward understanding the underlying physics and developing quantitative predictions of impinging-jet atomization. This paper summarizes the recent advances in this direction, including state-of-the-art theoretical, experimental, and numerical studies, along with representative results. Finally, concluding remarks address remaining challenges and highlight modeling capabilities of high-fidelity simulations.展开更多
Particle motion regime and enrichment behavior of dense granular impinging-jets formed by the nozzle with rectangular orifice are experimentally and numerically investigated.Two impingement patterns are identified,inc...Particle motion regime and enrichment behavior of dense granular impinging-jets formed by the nozzle with rectangular orifice are experimentally and numerically investigated.Two impingement patterns are identified,including long and short parallel patterns.Particles enrich in the central axis of the granular sheet when two jets impinge with the long axes parallel pattern.While at the short axes parallel pattern,particles generate two symmetrical enriched streams.The angle of particle-enriched streams is observed to increase with increasing angle of two impinging-jets and decreasing aspect ratio of the nozzle orifice.The particle image velocity(PIV)analysis results demonstrate that the circumferential distribution of the particle velocity on the granular sheet follows the Gaussian distribution.With the formation of particle-enriched streams,the concentration distribution of the particle evolves into a trimodal pattern.Results of the discrete element method(DEM)indicate that the core region with low velocity within the impact zone of impinging-jets generated by using two nozzles with rectangular orifices extends into a shuttle shape.The core region develops and extends along the horizontal(or vertical)directions at long(or short)axes impingement pattern,thereby,affecting the enrichment behavior of particles.展开更多
The hybrid manifold micro-pin-fin(MMPF)heat sink combined nozzle jets is an option for large-scale integrated circuits(LSI).The demond for uniform and ultra-high heat flux removal by MMPF heat sink has not been adequa...The hybrid manifold micro-pin-fin(MMPF)heat sink combined nozzle jets is an option for large-scale integrated circuits(LSI).The demond for uniform and ultra-high heat flux removal by MMPF heat sink has not been adequately investigated.This work aims to solve the problem of fluid organization.The proposed basic tiling topologies,including square,regular hexagon,30°rhombus,and 60°rhombus topologies,provide different organized fluid flows and heat transfer patterns.The present study focuses on comparing these topologies according to independent porous medium parameters,such as nozzle pore size D_(Z),flow pore size D_(X,Y),and porosityε.The results show that the square topology achieves the smallest total thermal resistance R_(tot)value of0.0975×10^(-4)K m^2/W,while the hexagon topology achieved the highest value of COP/?T,which was 2033.9 K^(-1).According to the sensitivity analysis results,the optimal total thermal resistance can be obtained by balancing the influences of nozzle pore size,flow pore size,and porosity.The optimal pressure drop can be obtained by maximizing the porosity.展开更多
基金sponsored partly by the National Natural Science Foundation of China (Nos. 11772343 and 11402274)partly by the Beijing Institute of Technology Research Fund Program for Young Scholars
文摘Impinging-jet injectors are widely used in liquid propulsion applications, since their simple configuration provides reliable and efficient atomization. The flowfield involves a series of complicated spatio-temporal evolutions. Much effort has been directed toward understanding the underlying physics and developing quantitative predictions of impinging-jet atomization. This paper summarizes the recent advances in this direction, including state-of-the-art theoretical, experimental, and numerical studies, along with representative results. Finally, concluding remarks address remaining challenges and highlight modeling capabilities of high-fidelity simulations.
基金supported by the National Natural Science Foundation of China(grant Nos.22278133 and U21B2088).
文摘Particle motion regime and enrichment behavior of dense granular impinging-jets formed by the nozzle with rectangular orifice are experimentally and numerically investigated.Two impingement patterns are identified,including long and short parallel patterns.Particles enrich in the central axis of the granular sheet when two jets impinge with the long axes parallel pattern.While at the short axes parallel pattern,particles generate two symmetrical enriched streams.The angle of particle-enriched streams is observed to increase with increasing angle of two impinging-jets and decreasing aspect ratio of the nozzle orifice.The particle image velocity(PIV)analysis results demonstrate that the circumferential distribution of the particle velocity on the granular sheet follows the Gaussian distribution.With the formation of particle-enriched streams,the concentration distribution of the particle evolves into a trimodal pattern.Results of the discrete element method(DEM)indicate that the core region with low velocity within the impact zone of impinging-jets generated by using two nozzles with rectangular orifices extends into a shuttle shape.The core region develops and extends along the horizontal(or vertical)directions at long(or short)axes impingement pattern,thereby,affecting the enrichment behavior of particles.
基金supported by the National Natural Science Foundation of China(Grant No.51876062)the Interdisciplinary Innovation Program of North China Electric Power University。
文摘The hybrid manifold micro-pin-fin(MMPF)heat sink combined nozzle jets is an option for large-scale integrated circuits(LSI).The demond for uniform and ultra-high heat flux removal by MMPF heat sink has not been adequately investigated.This work aims to solve the problem of fluid organization.The proposed basic tiling topologies,including square,regular hexagon,30°rhombus,and 60°rhombus topologies,provide different organized fluid flows and heat transfer patterns.The present study focuses on comparing these topologies according to independent porous medium parameters,such as nozzle pore size D_(Z),flow pore size D_(X,Y),and porosityε.The results show that the square topology achieves the smallest total thermal resistance R_(tot)value of0.0975×10^(-4)K m^2/W,while the hexagon topology achieved the highest value of COP/?T,which was 2033.9 K^(-1).According to the sensitivity analysis results,the optimal total thermal resistance can be obtained by balancing the influences of nozzle pore size,flow pore size,and porosity.The optimal pressure drop can be obtained by maximizing the porosity.
