Modeling study on the flow, heat transfer and energy conversion characteristics of low-power arc-heated hydrogen/nitrogen thrusters

A modeling study is conducted to investigate the effect of hydrogen content in propellants on the plasma flow, heat transfer and energy conversion characteristics of low-power (kW class) arc-heated hydrogen/nitrogen thrusters (arcjets). 1:0 (pure hydrogen), 3:1 (to simulate decomposed ammonia), 2:1 (to simulate decomposed hydrazine) and 0:1 (pure nitrogen) hydrogen/nitrogen mixtures are chosen as the propellants. Both the gas flow region inside the thruster nozzle and the anode-nozzle wall are included in the computational domain in order to better treat the conjugate heat transfer between the gas flow region and the solid wall region. The axial variations of the enthalpy flux, kinetic energy flux, directed kinetic-energy flux, and momentum flux, all normalized to the mass flow rate of the propellant, are used to investigate the energy conversion process inside the thruster nozzle. The modeling results show that the values of the arc voltage, the gas axial-velocity at the thruster exit, and the specific impulse of the arcjet thruster all increase with increasing hydrogen content in the propellant, but the gas temperature at the nitrogen thruster exit is significantly higher than that for other three propellants. The flow, heat transfer, and energy conversion processes taking place in the thruster nozzle have some common features for all the four propellants. The propellant is heated mainly in the near-cathode and constrictor region, accompanied with a rapid increase of the enthalpy flux, and after achieving its maximum value, the enthalpy flux decreases appreciably due to the conversion of gas internal energy into its kinetic energy in the divergent segment of the thruster nozzle. The kinetic energy flux, directed kinetic energy flux and momentum flux also increase at first due to the arc heating and the thermodynamic expansion, assume their maximum inside the nozzle and then decrease gradually as the propellant flows toward the thruster exit. It is found that a large energy loss (31-52%) occurs in the thruster nozzle due to the heat transfer to the nozzle wall and too long nozzle is not necessary. Modeling results for the NASA 1-kW class arcjet thruster with hydrogen or decomposed hydrazine as the propellant are found to compare favorably with available experimental data.

HIRFL新的束流分配系统

随着CSR的建成和兰州重粒子加速系统(HIRFL)实现质子加速,HIRFL现有的束流传输系统已不能满足越来越多的物理实验对供束时间的要求,为此,对原有的HIRFL的束流输运系统进行了分时供束改造,新的束流分配系统可以在给CSR供束和不供束两种情况下,同时使用SFC和SSC的束流在多个实验终端进行物理实验,介绍了新设计的HIRFL束流分配系统的布局和束流光学计算结果。

~(20)Na的β~+延发α粒子测量

利用兰州放射性次级束流线提供的2 0 Na束流 ,通过2 0 Na β+2 0 Ne →16 O+α过程 ,测量了2 0 Na的衰变半衰期T1/2 及衰变α粒子能谱 .结果表明 ,除了Ed≥ 2 .688MeV的 9条较高激发能级的衰变α粒子外 ,实验中还观察到衰变能量Ed 为 0 .890和 1 .0 54MeV ,1 .991MeV ,2 .4 2 4和 2 .4 57MeV的2 0 Ne低激发能级的 3条α谱线 .

单电离态Kr原子强跃迁能级振子强度的研究

阐述了用束 箔方法通过测量单电离态Kr原子强跃迁谱线的能级寿命来确定振子强度f 值的方法 ,并对确定出的强跃迁谱线的能级吸收振子强度进行简要讨论。