Analytical Study on Impingement Heat Transfer with Single—Phase Free—Surface Circular Liquid Jets

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Sickle bush (Dichrostachys cinerea L.) field performance and physical–chemical property assessment for energy purposes

The sickle bush (Dichrostachys cinerea (L.) Wight & Arn.) comprises a woody legume shrub which is widely distributed throughout of the tropical areas of Africa, Asia and Oceania, being found as well in Cuba where it represents a difficult to control invasive plant. It holds great silvopasture and energy crop potentials. In southwestern Spain a two year field trial was conducted contemplating also another six hardwood taxa commonly used as energy crops. The sickle bush above ground dry biomass fraction was 60.4%; sickle bush displayed a high transpiration rate during hot days (3.02 kg m⁻² d⁻¹ to 6.82 kg m⁻² d⁻¹); cold winter temperatures (<−2 °C) together with hot and dry summer air (<20% relative humidity) committed survival and growth. The physical-chemical wood properties and the pellets thereof derived were analyzed and compared to those of the other energy crop taxa. The within other woody species normal chemical composition range coupled to a high wood density and energetic use properties (19.2 MJ kg⁻¹ higher heating value, 29 g kg⁻¹ ash content) all allow for an industrial use. Pellets evidenced also good physical and mechanical properties (690 kg m⁻³ bulk density, 42 g kg⁻¹ moisture content). However, the mechanical durability (93.9%) was slightly less than that required by the non-industrial use standards, therefore further improvements should be studied. All of the above could encourage scrubland cuts in Cuba as a mechanical control method, in addition to the expansion of plantations within of their tropical climate based natural habitats.     

新型三功能煤粉锅炉燃烧器

三功能燃烧器是在偏置射流预燃室的基础上发展起来的一种新型煤粉燃烧器。它是利用一次风射流、控制射流和整流射流组合的空气动力学原理研制的，具有锅炉冷态点火启动、低负荷稳定火焰和作主燃烧器运行三项功能。该燃烧器可利用锅炉原有的供粉系统和一次风管道，并能在运行中方便地转换稳焰和主燃烧器功能，及调节着火点的距离。试验和运行表明，该燃烧器完全能够满足锅炉调峰的要求。具有重要的实用价值和显著的节油效果。     

旬阳钟家坪水电站溢流坝的面流消能设计与试验

研究了旬阳钟家坪水电站溢流坝的面流消能问题,通过分析确定了合理的溢流坝跌坎高度、鼻坎挑角和反弧半径等参数,并对下游水面线、水面波动和流速分布等情况进行了试验研究,为面流消能设计提供了依据,保证了设计的可靠性。     

Conditional analysis of lifted hydrogen jet diffusion flame experimental data and comparison to laminar flame solutions

Simultaneous point measurements of temperature, mixture fraction, major species, and OH concentrations in a lifted turbulent hydrogen jet flame are reprocessed to obtain the Favre average and conditional mean profiles. Large discrepancies between the Favre average and the ensemble average temperature, H₂O, and OH mole fractions are found at the lifted flame base, due to density weighting of fairly large samples of unreacted mixtures. Conditional statistics are used to reveal the reaction zone structure in mixture fraction coordinates. The cross-stream dependence of conditional reactive scalars, which is most notable at the lifted flame base and decreases to negligible levels with increasing streamwise positions, could be attributed to radial differences in both the Damköhler number and the level of partial premixing. Conditional results indicate that the lifted flame is stabilized at the outer region of the jet characterized by low strain rates and lean mixtures. Comparison of the measured conditional mean OH vs H₂O with a series of stretched laminar partially premixed flame and diffusion flame calculations reveals that strong partial premixing takes place at the lifted flame base and the strain rates vary from a=14,000 to 100 s⁻¹. The level of partial premixing and the strain rate decrease with increasing downstream locations. The range of estimated scalar dissipation rates (χ≈1–0.13 s⁻¹) at a further downstream location (x/D=33.3) is in agreement with reported values and the flame composition reaches an equilibrium condition at x/D=194.4. These results combined with previously reported data provide a benchmark data set for evaluation and refinement of turbulent combustion models for lifted hydrogen jet flame predictions.     

Characterization of high-pressure,underexpanded hydrogen-jet flames

Measurements were performed to characterize the dimensional and radiative properties of large-scale, vertical hydrogen-jet flames. This data is relevant to the safety scenario of a sudden leak in a high-pressure hydrogen containment vessel and will provide a technological basis for determining hazardous length scales associated with unintended hydrogen releases at storage and distribution centers. Jet flames originating from high-pressure sources up to 413 bar (6000 psi) were studied to verify the application of correlations and scaling laws based on lower-pressure subsonic and choked-flow jet flames. These higher pressures are expected to be typical of the pressure ranges in future hydrogen storage vessels. At these pressures the flows exiting the jet nozzle are categorized as underexpanded jets in which the flow is choked at the jet exit. Additionally, the gas behavior departs from that of an ideal-gas and alternate formulations for non-ideal gas must be introduced. Visible flame emission was recorded on video to evaluate flame length and structure. Radiometer measurements allowed determination of the radiant heat flux characteristics. The flame length results show that lower-pressure engineering correlations, based on the Froude number and a non-dimensional flame length, also apply to releases up to 413 bar (6000 psi). Similarly, radiative heat flux characteristics of these high-pressure jet flames obey scaling laws developed for low-pressure, smaller-scale flames and a wide variety of fuels. The results verify that such correlations can be used to a priori predict dimensional characteristics and radiative heat flux from a wide variety of hydrogen-jet flames resulting from accidental releases.     

Acoustic enhancement of combustion in lifted nonpremixed jet flames

Lifted nonpremixed jet flames are often used in industrial processes and present inherent difficulties such as their reattachment to the burner, blowout, and poor combustion. One solution is to control the jet by acoustic forcing. For flames lifted in the hysteresis zone where anchoring may occur, forcing at high amplitudes and middle frequencies (around 200 Hz) changes the combustion regime and prevents reattachement. The common long yellow plume, due to soot radiation, vanishes. The flame becomes shorter, totally blue and stabilizes at a higher position above the burner. The phenomenon is explained using the results obtained by analyzing the flow dynamics with high-speed laser tomography, laser Doppler anemometry, particle image velocimetry, and Mie scattering techniques. Measurements show that the excitation periodically generates axial velocities higher than the maximum velocity of the hysteresis zone, leading to flame liftoff. Some primary and streamwise eddy vortices similar to natural instabilities develop during the jet deceleration. Contrary to the unexcited case, these structures, disorganized by the superimposition of the forcing wave, lead to quasi-homogeneous turbulence which provides efficient mixing and improves the combustion regime. Finally, the frequency is sufficiently high to avoid excessive fluctuations of the lift-off height and the reattachment to the burner.     

一种新的基于水蒸气和水混合流体去胶方法

随着半导体器件尺寸越来越小,光刻胶的剥离,尤其是对硬烘后和离子注入后的光刻胶剥离,被认为是现代半导体器件制造过程中最具挑战的工艺之一。本文提出了一种新的湿法去胶技术从而可以替代现有的湿法剥离工艺和等离子灰化工艺。并针对固化后的光刻胶以及金膜和铬膜,进行了相关实验。然后给出了光刻胶的剥离图片,并分析和讨论了该过程的机理。结果表明,利用水蒸气和水的混合流体射流清洗技术可以很容易去除固化后的光刻胶和金属膜。     

Novel photoresist stripping technology using steam-water mixture

A novel wet vapor photoresist stripping technology is developed as an alternative to dry plasma ashing and wet stripping.Experiments using this technology to strip hard baked SU-8 photoresist,aurum and chromium film are carried out.Then the images of stripping results are shown and the mechanism is analyzed and discussed. The most striking result of this experiment is that the spraying mixture of steam and water droplets can strip photoresist and even metal film with ease.     

Accurate surface potential determination in Schottky diodes by use of correlated current and capacitance voltage measurements. Application to n–InP

Based on current voltage (I-V_g) and capacitance voltage (C-V_g) measurements, a reliable procedure is proposed to determine the effective surface potential V_d.V_g/ in Schottky diodes. In the framework of thermionic emission, our analysis includes both the effect of the series resistance and the ideality factor, even voltage dependent. This technique is applied to n-type indium phosphide (n-InP) Schottky diodes with and without an interfacial layer and allows us to provide an interpretation of the observed peak on the C-V_g measurements. The study clearly shows that the depletion width and the flat band barrier height deduced from C-V_g, which are important parameters directly related to the surface potential in the semiconductor, should be estimated within our approach to obtain more reliable information.