Five turbulence models of Reynolds average Navier-Stokes(RANS),including the standard k-ω model,the RNG k-e model taking into account the low Reynolds number effect,the realizable k-ω model,the SST k-ω model,and th...Five turbulence models of Reynolds average Navier-Stokes(RANS),including the standard k-ω model,the RNG k-e model taking into account the low Reynolds number effect,the realizable k-ω model,the SST k-ω model,and the Reynolds stress model(RSM),are employed in the numerical simulations of direct current(DC)arc plasma torches in the range of arc current from 80 A to 240 A and air gas flow rate from 10 m^3 h^-1 to 50 m^3 h^-1.The calculated voltage,electric field intensity,and the heat loss in the arc chamber are compared with the experiments.The results indicate that the arc voltage,the electric field,and the heat loss in the arc chamber calculated by using the standard k-ω model,the RNG k-ωmodel taking into account the low Reynolds number effect,and the realizable k-ω model are much larger than those in the experiments.The RSM predicts relatively close results to the experiments,but fails in the trend of heat loss varying with the gas flow rate.The calculated results of the SST k-ω model are in the best agreement with the experiments,which may be attributed to the reasonable predictions of the turbulence as well as its distribution.展开更多
A modelling study is performed to investigate the characteristics of both plasma flow and heat transfer of a laminar non-transferred arc argon plasma torch operated at atmospheric and reduced pressure. It is found tha...A modelling study is performed to investigate the characteristics of both plasma flow and heat transfer of a laminar non-transferred arc argon plasma torch operated at atmospheric and reduced pressure. It is found that the calculated flow fields and temperature distributions are quite similar for both cases at a chamber pressure of 1.0 atm and 0.1 atm. A fully developed flow regime could be achieved in the arc constrictor-tube between the cathode and the anode of the plasma torch at 1.0 atm for all the flow rates covered in this study. However the flow field could not reach the fully developed regime at 0.1 atm with a higher flow rate. The arc-root is always attached to the torch anode surface near the upstream end of the anode, i.e. the abruptly expanded part of the torch channel, which is in consistence with experimental observation. The surrounding gas would be entrained from the torch exit into the torch interior due to a comparatively large inner diameter of the anode channel compared to that of the arc constrictor-tube.展开更多
为了更好地研究直流电弧等离子体炬内的流动与传热,根据磁流体动力学(MHD)理论建立了等离子体电弧区的数学物理模型,采用磁矢量势A的方法来计算磁感应强度B的大小,利用通用软件FLUENT并进行二次开发,采用用户自定义函数(user defined fu...为了更好地研究直流电弧等离子体炬内的流动与传热,根据磁流体动力学(MHD)理论建立了等离子体电弧区的数学物理模型,采用磁矢量势A的方法来计算磁感应强度B的大小,利用通用软件FLUENT并进行二次开发,采用用户自定义函数(user defined function,UDF)加入磁流体动力学方程组中的源项和物性参数,并利用用户自定义标量方程(user defined scalar,UDS)的方法加入Maxwell方程组,采用SIMPLE算法对电弧区域进行了数值模拟。计算结果表明:等离子体炬内的弧电压随着气体质量流量的增加而增加;等离子体炬内的温度随着气体质量流量的增加而减小,而速度随着气体质量流量的增加而增加;出口处的温度和速度随径向距离的增加而减小,但温度减小的速率增加。这一结果可为实验提供理论指导和参考。展开更多
基金National Natural Science Foundation of China(Nos.11675177,11875256)the Anhui Province Scientific and Technological Project(No.1604a0902145).
文摘Five turbulence models of Reynolds average Navier-Stokes(RANS),including the standard k-ω model,the RNG k-e model taking into account the low Reynolds number effect,the realizable k-ω model,the SST k-ω model,and the Reynolds stress model(RSM),are employed in the numerical simulations of direct current(DC)arc plasma torches in the range of arc current from 80 A to 240 A and air gas flow rate from 10 m^3 h^-1 to 50 m^3 h^-1.The calculated voltage,electric field intensity,and the heat loss in the arc chamber are compared with the experiments.The results indicate that the arc voltage,the electric field,and the heat loss in the arc chamber calculated by using the standard k-ω model,the RNG k-ωmodel taking into account the low Reynolds number effect,and the realizable k-ω model are much larger than those in the experiments.The RSM predicts relatively close results to the experiments,but fails in the trend of heat loss varying with the gas flow rate.The calculated results of the SST k-ω model are in the best agreement with the experiments,which may be attributed to the reasonable predictions of the turbulence as well as its distribution.
基金supported by National Natural Science Foundation of China (Nos. 10575127, 10772016)the Doctoral Research Fund of Higher Education of China (No. 20070006022)
文摘A modelling study is performed to investigate the characteristics of both plasma flow and heat transfer of a laminar non-transferred arc argon plasma torch operated at atmospheric and reduced pressure. It is found that the calculated flow fields and temperature distributions are quite similar for both cases at a chamber pressure of 1.0 atm and 0.1 atm. A fully developed flow regime could be achieved in the arc constrictor-tube between the cathode and the anode of the plasma torch at 1.0 atm for all the flow rates covered in this study. However the flow field could not reach the fully developed regime at 0.1 atm with a higher flow rate. The arc-root is always attached to the torch anode surface near the upstream end of the anode, i.e. the abruptly expanded part of the torch channel, which is in consistence with experimental observation. The surrounding gas would be entrained from the torch exit into the torch interior due to a comparatively large inner diameter of the anode channel compared to that of the arc constrictor-tube.
文摘为了更好地研究直流电弧等离子体炬内的流动与传热,根据磁流体动力学(MHD)理论建立了等离子体电弧区的数学物理模型,采用磁矢量势A的方法来计算磁感应强度B的大小,利用通用软件FLUENT并进行二次开发,采用用户自定义函数(user defined function,UDF)加入磁流体动力学方程组中的源项和物性参数,并利用用户自定义标量方程(user defined scalar,UDS)的方法加入Maxwell方程组,采用SIMPLE算法对电弧区域进行了数值模拟。计算结果表明:等离子体炬内的弧电压随着气体质量流量的增加而增加;等离子体炬内的温度随着气体质量流量的增加而减小,而速度随着气体质量流量的增加而增加;出口处的温度和速度随径向距离的增加而减小,但温度减小的速率增加。这一结果可为实验提供理论指导和参考。
