Gas mass flux rate,metal mass flux rate and outlet gas velocity are three atomization scale parameters which greatly affect the atomization efficiency. A Laval-style annual slot supersonic nozzle is designed by optimi...Gas mass flux rate,metal mass flux rate and outlet gas velocity are three atomization scale parameters which greatly affect the atomization efficiency. A Laval-style annual slot supersonic nozzle is designed by optimizing the geometric parameters of delivery tube outlet and gas outlet to obtain applicable atomization scale parameters. A computational fluid flow model is adopted to investigate the effect of atomization gas pressure ( P0 ) on the gas flow field in gas atomization progress. The numerical results show that the outlet gas velocity of the nozzle is not affected by P0 and the maximum gas velocity reaches 452 m / s. The alternation of aspiration pressure ( ΔP) is caused by the variations of stagnation pressure and location of Mach shock disk, and hardly by the location of stagnation point. The aspiration pressure is found to decrease as P0 increases when P0 < 1. 3 MPa. However,at a higher atomization gas pressure increasing P0 causes an opposite: the aspiration pressure atomization increases with the gas pressure,and keeps a plateau when P0 > 2. 0 MPa. The minimum aspiration pressure ΔP = - 70 kPa is obtained at P0 = 1. 3 MPa. The results indicate that the designed Laval- style annual slot nozzle has well atomization characteristic at lower atomization pressure.展开更多
The bleed slot is necessary for the requirement of the hypersonic quiet flow all over the world. The aim of the bleed slot is to decrease the influence of the disturbances from the contraction of the quiet nozzle to t...The bleed slot is necessary for the requirement of the hypersonic quiet flow all over the world. The aim of the bleed slot is to decrease the influence of the disturbances from the contraction of the quiet nozzle to the boundary layer downstream of the throat, so that the boundary layer of the nozzle could be maintained as laminar flow. The main parameters of the bleed slot include the distance from lip to throat (DLT) and the width of slot (WS). Various values of those parameters will affect the performance of the slot by changing the suction intensity of the bleed slot. Two kinds of the bleed slots in the world are compared in this paper and the aerodynamic design of the bleed slots is optimized based on the Purdue-type slot. The influences of the various values of those parameters to the flow field around the throat are analyzed and the optimizing results of DLT and WS are consistent with those relative data designed for the slot of the Boeing/AFOSR Ma 6 Quiet Tunnel.展开更多
Slot nozzle and intensive nozzle can be used in ultra fast cooling equipment. The spray cooling method with higher water pressure can be taken in order to achieve ultra fast cooling for hot rolled strip. Water will be...Slot nozzle and intensive nozzle can be used in ultra fast cooling equipment. The spray cooling method with higher water pressure can be taken in order to achieve ultra fast cooling for hot rolled strip. Water will be diffused after it is sprayed out from ultra fast cooling nozzle. Spray diffusivity will affect water velocity and penetrability of water into residual water layer on top of the strip,and then it will affect strip cooling effect. Water spraying process can be simulated by Fluent and some conclusions were obtained. Slot nozzle width and outlet velocity within setting range could not affect the length of potential core zone and the spray diffusivity. Intensive nozzle diameter and outlet velocity will affect the length of potential core zone and the spray diffusivity with different extent. These conclusions will provide referenced role for confirming ultra fast cooling nozzle size and distance between ultra fast cooling nozzle and hot rolled strip.展开更多
The flow field and heat transfer of the strip surface due to the twin slot vertical jet impingement were investigated using the ANSYS FLUENT.The RNG k-ε model was carried out in the turbulent calculation.Systematic p...The flow field and heat transfer of the strip surface due to the twin slot vertical jet impingement were investigated using the ANSYS FLUENT.The RNG k-ε model was carried out in the turbulent calculation.Systematic parametric research was conducted by varying the jet velocity of nozzle exit(V=5 m/s,7.5 m/s,10 m/s),the temperature of cooling water(T_w=280 K,300 K),the normalized spacing from the nozzle to the strip surface(H=10,15,20,33),and the normalized spacing from the nozzle to nozzle centerline(W=0,15,30).The velocity streamline of the flow domain and the general trend of the distribution of the local Nusselt number on the impingement surface of strip were obtained.The result indicate that,the average Nusselt number increases by about70%(90%) as the jet velocity is increased from 5 m/s to 7.5 m/s(from 7.5 m/s to 10 m/s),and T_w,Hand//have minimal effect on it.While the valley Nusselt number decreases by about 10%-43%with the increase of H and W.The functional relationship between the average Nusselt number and the systematic parameters is derived by the least square regression method.展开更多
文摘Gas mass flux rate,metal mass flux rate and outlet gas velocity are three atomization scale parameters which greatly affect the atomization efficiency. A Laval-style annual slot supersonic nozzle is designed by optimizing the geometric parameters of delivery tube outlet and gas outlet to obtain applicable atomization scale parameters. A computational fluid flow model is adopted to investigate the effect of atomization gas pressure ( P0 ) on the gas flow field in gas atomization progress. The numerical results show that the outlet gas velocity of the nozzle is not affected by P0 and the maximum gas velocity reaches 452 m / s. The alternation of aspiration pressure ( ΔP) is caused by the variations of stagnation pressure and location of Mach shock disk, and hardly by the location of stagnation point. The aspiration pressure is found to decrease as P0 increases when P0 < 1. 3 MPa. However,at a higher atomization gas pressure increasing P0 causes an opposite: the aspiration pressure atomization increases with the gas pressure,and keeps a plateau when P0 > 2. 0 MPa. The minimum aspiration pressure ΔP = - 70 kPa is obtained at P0 = 1. 3 MPa. The results indicate that the designed Laval- style annual slot nozzle has well atomization characteristic at lower atomization pressure.
文摘The bleed slot is necessary for the requirement of the hypersonic quiet flow all over the world. The aim of the bleed slot is to decrease the influence of the disturbances from the contraction of the quiet nozzle to the boundary layer downstream of the throat, so that the boundary layer of the nozzle could be maintained as laminar flow. The main parameters of the bleed slot include the distance from lip to throat (DLT) and the width of slot (WS). Various values of those parameters will affect the performance of the slot by changing the suction intensity of the bleed slot. Two kinds of the bleed slots in the world are compared in this paper and the aerodynamic design of the bleed slots is optimized based on the Purdue-type slot. The influences of the various values of those parameters to the flow field around the throat are analyzed and the optimizing results of DLT and WS are consistent with those relative data designed for the slot of the Boeing/AFOSR Ma 6 Quiet Tunnel.
基金State"1025"Science and Technology Support Projects,China(No.2012BAF04B01)
文摘Slot nozzle and intensive nozzle can be used in ultra fast cooling equipment. The spray cooling method with higher water pressure can be taken in order to achieve ultra fast cooling for hot rolled strip. Water will be diffused after it is sprayed out from ultra fast cooling nozzle. Spray diffusivity will affect water velocity and penetrability of water into residual water layer on top of the strip,and then it will affect strip cooling effect. Water spraying process can be simulated by Fluent and some conclusions were obtained. Slot nozzle width and outlet velocity within setting range could not affect the length of potential core zone and the spray diffusivity. Intensive nozzle diameter and outlet velocity will affect the length of potential core zone and the spray diffusivity with different extent. These conclusions will provide referenced role for confirming ultra fast cooling nozzle size and distance between ultra fast cooling nozzle and hot rolled strip.
基金Project(2012 BAF04B01)Supported by the National Science and Technology Pillar Program during the Twelfth Five-year Plan of China
文摘The flow field and heat transfer of the strip surface due to the twin slot vertical jet impingement were investigated using the ANSYS FLUENT.The RNG k-ε model was carried out in the turbulent calculation.Systematic parametric research was conducted by varying the jet velocity of nozzle exit(V=5 m/s,7.5 m/s,10 m/s),the temperature of cooling water(T_w=280 K,300 K),the normalized spacing from the nozzle to the strip surface(H=10,15,20,33),and the normalized spacing from the nozzle to nozzle centerline(W=0,15,30).The velocity streamline of the flow domain and the general trend of the distribution of the local Nusselt number on the impingement surface of strip were obtained.The result indicate that,the average Nusselt number increases by about70%(90%) as the jet velocity is increased from 5 m/s to 7.5 m/s(from 7.5 m/s to 10 m/s),and T_w,Hand//have minimal effect on it.While the valley Nusselt number decreases by about 10%-43%with the increase of H and W.The functional relationship between the average Nusselt number and the systematic parameters is derived by the least square regression method.
