科创中国

In working state, the dynamic performance of dry gas seal, generated by the rotating end face with spiral grooves, is determined by the open force of gas film and leakage flow rate. Generally, the open force and the leakage flow rate can be obtained by finite element method, computational fluid dynamics method and experimental measurement method. However, it will take much time to carry out the above measurements and calculations. In this paper, the approximate model of parallel grooves based on the narrow groove theory is used to establish the dynamic equations of the gas film for the purpose of obtaining the dynamic parameters of gas film. The nonlinear differential equations of gas film model are solved by Runge-Kutta method and shooting method. The numerical values of the pressure profiles, leakage flux and opening force on the seal surface are integrated, and then compared to experimental data for the reliability of the numerical simulation. The results show that the numerical simulation curves are in good agreement with experimental values. Furthermore, the opening force and the leakage flux are proved to be strongly correlated with the operating parameters. Then, the function-coupling method is introduced to analyze the numerical results to obtain the correlation formulae of the opening force and leakage flux respectively with the operating parameters, i.e., the inlet pressure and the rotating speed. This study intends to provide an effective way to predict the aerodynamic performance for designing and optimizing the groove styles in dry gas seal rapidly and accurately.

The current research of the valveless piezoelectric pump focuses on increasing the flow rate and pressure differential. Compared with the valve piezoelectric pump, the valveless one has excellent performances in simple structure, low cost, and easy miniaturization. So, their important development trend is the mitigation of their weakness, and the multi-function integration. The flow in a spiral tube element is sensitive to the element attitude caused by the Coriolis force, and that a valveless piezoelectric pump is designed by applying this phenomenon. The pump has gyroscopic effect, and has both the actuator function of fluid transfer and the sensor function, which can obtain the angular velocity when its attitude changes. First, the present paper analyzes the flow characteristics in the tube, obtains the calculation formula for the pump flow, and identifies the relationship between pump attitude and flow, which clarifies the impact of flow and driving voltage, frequency, spiral line type and element attitude, and verifies the gyroscopic effect of the pump. Then, the finite element simulation is used to verify the theory. Finally, a pump is fabricated for experimental testing of the relationship between pump attitude and pressure differential. Experimental results show that when Archimedes spiral θ=4π is selected for the tube design, and the rotation speed of the plate is 70 r/min, the pressure differential is 88.2 Pa, which is 1.5 times that of 0 r/min rotation speed. The spiral-tube-type valveless piezoelectric pump proposed can turn the element attitude into a form of pressure output, which is important for the multi-function integration of the valveless piezoelectric pump and for the development of civil gyroscope in the future.

目的 分析不典型恶性胃肠道间质瘤(GIST)的螺旋CT扫描图像的表现特点,以提高对该病的诊断准确性.方法 回顾性分析13例不典型恶性GIST的螺旋CT扫描图像特点.所有病例术前均行螺旋CT平扫加增强扫描检查,均经手术病理证实为GIST.结果 13例腹腔CT表现为边界不清的不规则或浅分叶状占位,其密度多不均匀;螺旋CT平扫8例呈实性等或稍低密度,5例呈囊实性,3例病灶内见气体密度,4例见点状钙化灶;增强扫描见实性病灶及病灶的实性部分呈持续强化或延迟强化,囊性部分无强化,病灶内部均可见范围不等的无强化区.结论 不典型恶性GIST的螺旋CT图像特点是腹腔内巨大不规则或浅分叶状占位,密度不均匀,病灶内部见范围不等的低密度区.增强扫描呈延迟强化或持续强化,内部见不同程度的无强化区.

选择在螺旋卷式反渗透膜元件组件设计中,对影响膜元件使用寿命的抗污染性能及影响膜元件系统运行能耗的工艺参数进行理论模拟实验,并与实际生产运行相结合,得出最优化的设计组合.主要工艺参数为给水流道布宽度、深度、入水角度、及膜元件卷制页数的优化选择,筛选出提高抗污染性能及低能耗、高经济性的膜元件,并对螺旋卷式膜元件的设计起指导作用.