A new equation of state to predict S-CO<Subscript>2</Subscript> flow with real gas effects

The accuracy of the thermodynamic properties prediction from the different Equation of state (EOS) varies upon the range of temperature and pressure. Despite the variety of EOS available, there is no de facto for selecting an EOS for particular computational modeling. The EOS model recently developed by Kumar and Kim (K-K EOS) determines more accurately the thermodynamic properties of CO₂ than earlier models. In this present study, K-K EOS is successfully implemented in the computational analysis of compressible supercritical CO₂ flow (S-CO₂) in the thermodynamic region near and away from the vapour-liquid critical point. Computational results of SCO₂ flow with the real gas properties predicted with the K-K EOS is compared with Span and Wagner (SW EOS) and ideal EOS.     

Influence of tip end-plate on noise of small axial fan

In this work, tip end-plate is used to improve the noise performance of small axial fans. Both numerical simulations and experimental methods were adopted to study the fluid flow and noise level of axial fans. Four modified models and the prototype are simulated. Influences of tip end-plate on static characteristics, internal flow field and noise of small axial fans are analyzed. The results show that on basis of the prototype, the model with the tip end-plate of 2 mm width and changed length achieved best noise performance. The overall sound pressure level of the model with the tip end-plate of 2 mm width and changed length is 2.4 dB less than that of the prototype at the monitoring point in specified far field. It is found that the mechanism of noise reduction is due to the decrease of vorticity variation on the surface of blades caused by the tip end-plate. Compared with the prototype, the static pressure of the model with the tip end-plate of 2 mm width and changed length at design flow rate decreases by 2 Pa and the efficiency decreases by 0.8%. It is concluded that the method of adding tip end-plate to impeller blades has a positive influence on reducing noise, but it may diminish the static characteristics of small axial fan to some extent.     

Experimental investigations on impaction pin nozzles for inlet fogging system

Increasing power demands have necessitated the development of energy efficient systems in the industrial sector. At present, about 10% of the overall electric power used by large industrial plants is consumed by high-capacity compressors supplying compressed air. Likewise, in a gas turbine power plant, nearly half the generated power is used for driving the compressor. The work of compression is proportional to inlet air temperature, and cooling the inlet air can save considerable amount of power in large turbo machines during hot summer months. Inlet fogging is a popular means of inlet air cooling, and fog nozzles are the most critical components in an inlet fogging installation. Majority of these installations employ impaction pin nozzles. In the present work, experiments are conducted over a wide range of operating parameters in variable length wind tunnels of different cross sections in order to investigate the performance of impaction pin nozzle in inlet fogging. Flow visualization and measurements are carried out to analyze the fog behavior and identify suitable nozzle locations in typical air ducts. The results show that impaction pin nozzles are suitable for inlet fogging applications.     

Study on the compressible viscous flows through a straight pipe

When sonic nozzles of significantly smaller diameter are used as standard flow meters, the critical backpressure ratio is affected by the boundary layer at the nozzle throat. It is known that, as the flow pathway is complicated in actual valves, the critical pressure ratio differs from the ideal value. However, the effect of the boundary layer thickness on choking criteria is still controversial. Choking phenomenon in a sonic nozzle fitted with a straight circular pipe of variable length is investigated numerically and the results are compared with experimental and theoretical ones. The results show that the actual critical pressure ratio is less than the ideal value and it decreases with increase in pipe length. The effect of boundary layer thickness on main flow Mach number is also made clear in this work. In addition, sonic conductance and pressure loss in actual viscous flows computed are compared with the ISO 6358 standard.     

Experimental study on hysteresis phenomena of shock wave structure in an over-expanded axisymmetric jet

In recent studies on two-dimensional supersonic jets, it is reported that the hysteresis phenomenon for the reflection type of shock waves in the jet flow field is occurred under the quasi-steady flow condition and this phenomenon is affected by the transitional pressure ratio between the regular reflection and Mach reflection. However, so far, there are few researches on the hysteresis phenomenon for the transition of shock waves between regular and Mach reflection in over-expanded supersonic jets and the phenomenon has not been investigated satisfactorily. Therefore, the purpose of this study is to clarify the hysteresis phenomena for the reflection type of shock wave in the over-expanded axi-symmetric supersonic jet experimentally, and to discuss the relationship between hysteresis phenomenon and rate of the change of pressure ratio with time. Furthermore, the effect of Mach number at the nozzle exit on hysteresis loop was investigated for two kinds of nozzle.     

锁骨下动脉闭塞机械再通的方法研究

目的研究锁骨下动脉闭塞血管内机械再通方法和疗效。方法选择３２例症状性锁骨下动脉闭塞患者行血管内机械再通治疗，观察再通率及疗效。结果３２例锁骨下动脉闭塞患者中，用不同方法成功完成血管内机械再通后行血管内支架成形术，术后全部患者后循环缺血症状和上肢缺血症状明显改善。结论采用适当方法行机械再通治疗锁骨下动脉闭塞安全、可行。     

外科手术后假性动脉瘤的介入治疗

目的总结外科手术后继发假性动脉瘤介入治疗的效果和经验。方法５例外科手术后继发不同部位假性动脉瘤，采用不同的介入方法治疗。１例左侧髂总动脉假性动脉瘤经腹主动脉球囊阻断后作手术人工血管置换，１例右侧锁骨下动脉假性动脉瘤采用覆膜支架置入术将其隔绝，３例终末型动脉的假性动脉瘤采用明胶海绵和（或）弹簧圈栓塞。结果所有假性动脉瘤均完全闭合，未出现治疗相关并发症。结论采用不同的介入技术治疗外科手术后继发假性动脉瘤临床效果肯定，是一种值得推广的治疗方法。     

肝癌肝外血管多层螺旋CT三维重建的临床应用

目的探讨原发性肝细胞肝癌（HCC）肝外供血动脉多层螺旋CT三维重建的显示能力及其临床价值。方法６４层螺旋CT常规肝脏三期扫描，动脉期采用容积再现（VR）及最大密度投影（MIP）三维重建技术，对８９例原发性中晚期HCC肝内、外供血动脉的起源及走行行三维重建，并与血管造影结果对比。结果肿瘤巨块型５９例，发生肿瘤肝外供血３３例；弥漫型２１例，发生肝外供血４例；结节型９例，发生肝外供血１例。肿瘤肝外供血动脉有８条途经，共发现肿瘤肝外供血动脉４４支，肝动脉起源变异１９支。结论HCC肝外供血动脉较为常见和多变，并与肿瘤类型和部位有关，６４层螺旋CT血管三维重建能达到血管造影效果，可减少血管造影次数，减少对比剂用量，减少医患辐射剂量，提高治疗效果。     

未破裂后交通动脉瘤致动眼神经麻痹血管内治疗疗效分析

目的探讨未破裂后交通动脉瘤（PComA）致动眼神经麻痹（OMNP）血管内治疗疗效。方法对１１例伴有OMNP的PComA患者的治疗时机、治疗方式与动眼神经功能恢复的关系进行分析。结果治疗后动眼神经功能全部恢复１０例（９０．９％），部分恢复１例（９．１％），其恢复状况与治疗时机、麻痹程度密切相关。结论血管内栓塞未破裂PComA可有效恢复其致OMNP，但神经功能的恢复取决于麻痹程度和早期手术时机。     

不同剂量MTX经动脉灌注治疗切口妊娠疗效的分析

目的探讨剖宫产后切口瘢痕妊娠经子宫动脉灌注MTX的有效剂量。方法孕周在５～９周的３６例切口瘢痕妊娠，经两侧子宫动脉灌注MTX，剂量从６０mg 起逐渐加至１００、１５０、２００mg ，每一剂量组均为９例，灌注后用明胶海绵阻塞两侧子宫动脉直至DSA下子宫动脉造影染色消失，３d至１周内行刮宫术。结果介入术后１周内血β－HCG和血孕酮的下降速度与MTX用量大小存在一定关系。６０、２００mg 间差异有统计学意义（P＜０．０５），１００、１５０mg 组间差异无统计学意义（P＜０．０５）。住院时间２００mg 组＜１００、１５０mg 组＜６０mg 组。结论切口妊娠经动脉灌注MTX的有效用量建议为２００mg ，介入术后可杀死胚胎，迅速降低血β－HCG和血孕酮，缩短住院日期。