Pulsating Jet Impingement Heat Transfer Enhancement

This article presents results from a numerical study of pulsating jet impingement heat transfer. The motivation is to seek conditions offering a significant enhancement compared to steady flow impingement drying. The CFD software package FLUENT was used for simulating slot-type pulsating jet impingement flows with confinement. The parameter study included velocity amplitude ratio, mean jet velocity, and pulsation frequency. The distance from nozzle exit to surface was three times the hydraulic diameter of the nozzle. The Reynolds number based on the nozzle hydraulic diameter and jet temperature was 2,460 with a mean jet velocity of 30 m/s, which is the base case of the numerical experiments. Results showed that time-averaged surface heat transfer increased with increasing velocity amplitude for the same mean jet velocity. Large velocity amplitudes helped enhance heat transfer by two mechanisms: high jet velocity during the positive cycle and strong recirculating flows during the negative cycle. For the cases with different mean jet velocities but the same maximum velocity, time-averaged surface heat flux decreased with decreasing mean jet velocity. As for the effects of pulsation frequency, with high-velocity amplitude ratio, time-averaged surface heat fluxes were at the same level regardless of frequency. However, at low-velocity amplitude ratio, high frequency caused stronger recirculating flows resulting in greater heat transfer compared to the cases with a lower frequency.     

污水射流曝气工艺技术在聚驱中的应用

为了减少油田污水外排，应用油田采出的污水配制和稀释聚合物溶液，需要对污水进行曝气处理，通过小型试验和现场应用，对应用射流曝气技术处理油田污水的工艺和效果进行了可行性研究和试验，研究表明应用射流曝气技术处理油田污水，可以达到曝氧站的处理效果，经过射流曝气工艺处理的污水所配制和稀释的聚合物溶液粘度能够满足聚合物驱油的注入要求，并且可以大幅度降低地面工程建设投资，取得较好的经济效益和社会效益。     

等温脉冲自由射流压力场动态特性的实验研究

针对冶金工业过程脉冲燃烧及脉冲流技术所进行研究的基础部分,借助于计算机辅助信号分析手段,运用湍流统计理论,对等温脉冲自由射流压力场动态特性进行了系统的实验研究。实验的Re范围为19486～93936,st范围为0～0.057,所对应的射流脉冲频率为0～25Hz。研究结果表明;脉冲射流极大地提高了射流区压力波动水平,任何受气体的动量、热量和质量传递制约的工业过程均可望通过适当地采用脉冲流技术加以强化.     

Optimal Conditions for Preparing Ultra-Fine CeO2 Powders in A Submerged Circulative Impinging Stream Reactor

Cerium carbonate powders were produced in a submerged circulation impinging stream reactor (SCISR) from Ce(NO3)3·6H2O. NH4HCO3 was used as a precipitant in the reaction. Cerium carbonate powders were roasted to produce ultra-fine cerium dioxide (CeO2) powders. The optimal conditions of such production process were obtained by orthogonal and one-factor experiments. The results showed that ultra-fine and narrowly distributed cerium carbonate powders were produced under the optimal flowing conditions. The concentrations of Ce(NO3)3 and NH4HCO3 solutions were 0.25 and 0.3 mol·L-1, respectively. The concentration of PEG4000 added in these two solutions was 4 g·L-1. The stirring ratio, reaction temperature, feeding time, solution pH, reaction time and digestion time were 900 r·min-1, 80 ℃, 20 min, 5～6, 5 min and 1 h, respectively. The final product, CeO2 powders, was obtained by roasting the produced cerium carbonate in air for 3 h at 500 ℃. The finally produced CeO2 powders were torispherical particles with a narrow size distribution of 0.8～2.5 μm. The crystal structure of CeO2 powders belonged to cubic crystal system and its space point group was O5H-FM3M. Under optimal conditions, powders produced by SCISR were finer and more narrowly distributed than that by Stirred Tank Reactor (STR).     

小眼井最优水力学设计及分析

在充分考虑小眼井钻井特点和合理确定环空压耗的基础上，将喷射钻井理论和环空携岩理论有机结合起来，导出了在两种工作方式下优化设计小眼井钻井水力参数模型，并开发了应用软件。通过实例计算，提出了在小眼井最优水力学设计中采用最大水功率工作方式的重要性，并建议在大眼井的水力参数设计中考虑钻柱的偏心、旋转和钻杆接头对环空压耗的影响。     

喷气客机涡轮风扇发动机的振动诊断与改进

通过动态分析和现场测试对一喷气客机的发动机振动作出诊断，发现涡轮叶轮的变柔导致其极转动惯量显著下降，因而改变发动机的动态特性，使其临界转速接近飞机的巡航转速，产生不应有的振动和噪声。文章提出了具体改进方案，已为研制单位采用。     

Effects of electrode arrangement and pressure on synthesis of diamond films by arc discharge plasma jet chemical vapor deposition

The setup and deposition conditions of electrode arrangement and pressure have been studied to synthesize diamond films at high growth rate on wide area efficiently by arc discharge plasma jet chemical vapor deposition. An apparatus has been used in which four plasma torches, one is used for cathode and the others for divided anodes, are arranged and the positions of these torches are changeable. Growth rate, deposition area and thickness of diamond films have increased with changing the electrode arrangements without improvement of thickness variation. Maximum growth rate of our apparatus has occurred at the pressure of 6.7 kPa and diamond films that have less variations of quality and surface roughness have been synthesized at lower pressure during deposition. Moreover, a high conversion rate, which is the ratio of carbon atoms that form diamond in supplied methane gas, of 16% has been obtained at the pressure of 6.7 kPa and methane concentration of 2%.     

在高速气流粉碎作用下PVC的力化学降解及形态变化的研究

通过ＧＰＴ、ＦＴ－ＩＲ、ＳＥＭ和力学性能测试，研究了在高速气流作用下聚氯乙烯（ＰＶＣ）的力化学降解反应、颗粒形态和微晶结构变化及其对ＰＶＣ物理、力学性能的影响。实验结果表明，经过高速气流处理ＰＶＣ，分子量将有所降低，晶体结构发生变化，颗粒尺寸和表观密度降低，比表面积增大，加工性能和力学性能得到明显改善。     

喷嘴结构对高压射流特性影响研究

自20世纪70年代以来,高压水射流技术已在各工业领域逐渐得到了广泛应用,但迄今仍未能大规模采用,原因是还存在一些有待解决的问题,其中最为迫切的就是如何提高喷嘴射流效率、充分利用其能量的问题。喷嘴是水射流技术应用中获得高能量利用率的关键因素之一,其结构好坏直接影响射流质量。为充分发挥喷嘴最大效率,最大限度地利用水力能量,国内外有关专家从理论分析、数值计算和实验研究3个方面对喷嘴结构与高压射流特性的关系进行了研究分析,结果表明喷嘴结构对射流流动特性、冲蚀性能、空化现象等产生重要影响,指出提高喷嘴效率应当着眼于以下几个方面:加强基础研究;改变射流作用方式、将连续射流调制成脉动射流;充分利用空化空泡破裂压力,研制开发优质喷嘴,以期对拓宽水射流技术在工业中的应用有所帮助。     

火箭燃气射流对斜板冲击流场的数值模拟

采用高精度，高分辨率的二阶ＴＶＤ有限体积方法，对二维无粘射流冲击斜板的复杂流动场进行了数值模拟，得到了和实验规律相一致的计算结果。