双喷气自循环机匣处理对对转压气机性能的影响

为发展适用于对转压气机变转速比工况下的扩稳技术,基于某两级对转压气机设计出一种新型双喷气自循环机匣处理结构,能够实现在不同转速比下提高对转压气机的失速裕度。在设计转速比下研究了轴向喷气位置对自循环机匣处理扩稳能力的影响,并选取扩稳性能最佳的双喷气自循环机匣处理方案探究其在变转速比工况下的扩稳潜力。研究结果表明,在设计转速下,双喷气自循环机匣处理主要改善后排转子的叶顶流场,失速裕度最大提高8.40%;在非设计转速比下,双喷气自循环机匣处理可将失速裕度提升8.71%~9.74%。双喷气自循环机匣处理的双射流将叶顶泄漏流和主流的交界面推向下游,同时改善了两转子的叶顶流场品质,从而推迟失速的发生。

Amenability to dry processing of high ash thermal coal using a pneumatic table

High ash thermal coal from India was used to conduct the dry processing of fine coal using a pneumatic table to evolve a techno-economically novel technique. The fine as-received sample having 55.2g ash was subjected to washability studies at variant densities from 1.4 to 2.2 to assess the amenability to separa- tion. The experiments were conducted using a central composite design for assessing the interactive effects of the variable parameters of a pneumatic table on the product yield and ash content. The performance of the pneumatic table was analyzed in terms of clean coal yield, recovery of combustibles, separation efficiency （Esp） and useful heat value of clean coal. The combustibles of clean coal obtained through a single stage operation at 35% and 38.7% ash were 40% and 63% respectively. However, the two stage processing was more effective in reducing the ash content in the clean coal. The rougher concentrate generated at higher ash level was subsequently processed in different conditions at 35% ash level, and 58g combustibles could be recovered. Hence, two stage processing increases the combustibles by 18 units and the useful heat value of clean coal increases from 1190 kcal/kg to 3750 kcal/kg.

Pilot Project on in Situ Aerobisation of Old Landfills： Results from Konstanz Dorfweiher Landfill

A new in situ treatment technique was being utilized on a part of the Dorfweiher landfill in Konstanz, Germany to reduce the aftercare period. From 2010 to 2012, the landfill was aerated intermittently with low pressure. Outgoing air was treated passively in an open biofilter which covers the landfill surface. The landfill was aerated by means of 80 air injection wells arranged area-wide in a 10 m grid. An elaborate measuring process and technological controls are being utilized in the pilot scheme. The data collected offer interesting insights about the processes during aeration, allowing optimization of the aeration strategy depending on changes of the conditions in the landfill. During the three-year aeration phase, conditions have changed inside the landfill section in various ways. In numerous zones of the landfill body, the aeration caused aerobic conditions with a decline of methane production. Accelerated settlings are measured up to 11%. The effects of the aerobic stabilization on the landfill are evaluated in a two-year monitoring phase started in 2013.

Numerical investigation of the casing treatment mechanism with a single circumferential groove

The paper investigates the effect of a single circumferential groove casing treatment(CGCT) on a transonic compressor rotor numerically.In particular,the effect of the groove at different axial locations on the flow field is studied in detail and stall margin improvement is also discussed.The present results show that the groove close to the leading edge plays a crucial role in stabilizing the near stall flow structures and,hence,improves the stall margin.The groove at the mid-chord-section of the blade can help exchange and transfer momentums between different directions,and suppress the flow unsteadiness,leading to increased efficiency in rotor performance and extended operation range.The groove located near the blade trailing edge has limited effects on stall margin improvement and may cause additional penalty in efficiency.Through comparison with the recent work on CGCT,some common flow physics can be observed.

Advanced partial nucleation for single-phase FA0.92MA0.08PbI3-based high-efficiency perovskite solar cells

To date, extensive research has been carried out,with considerable success, on the development of highperformance perovskite solar cells(PSCs). Owing to its wide absorption range and remarkable thermal stability, the mixedcation perovskite FAxMA1-xPbI3(formamidinium/methylammonium lead iodide) promises high performance. However, the ratio of the mixed cations in the perovskite film has proved difficult to control with precursor solution. In addition, the FAxMA1-xPbI3 films contain a high percentage of MA+and suffer from serious phase separation and high trap states, resulting in inferior photovoltaic performance. In this study, to suppress phase separation, a post-processing method was developed to partially nucleate before annealing, by treating the as-prepared intermediate phase FAI-Pb I2-DMSO(DMSO: dimethylsulfoxide) with mixed FAI/MAI solution. It was found that in the final perovskite, FA0.92MA0.08 PbI3, defects were substantially reduced because the analogous molecular structure initiated ion exchange in the post-processed thin perovskite films, which advanced partial nucleation. As a result, the increased light harvesting and reduced trap states contributed to the enhancement of open-circuit voltage and short-circuit current. The PSCs produced by the post-processing method presented reliable reproducibility, with a maximum power conversion efficiency of 20.80% and a degradation of ~30% for 80 days in standard atmospheric conditions.

Wrinkle-free graphene with spatially uniform electrical properties grown on hot-pressed copper

The chemical vapor deposition （CVD） of graphene on Cu substrates enables the fabrication of large-area monolayer graphene on desired substrates. However, during the transfer of the synthesized graphene, topographic defects are unavoidably formed along the Cu grain boundaries, degrading the electrical properties of graphene and increasing the device-to-device variability. Here, we introduce a method of hot-pressing as a surface pre-treatment to improve the thermal stability of Cu thin film for the suppression of grain boundary grooving. The flattened Cu thin film maintains its smooth surface even after the subsequent high temperature CVD process necessary for graphene growth, and the formation of graphene without wrinkles is realized. Graphene field effect transistors （FETs） fabricated using the graphene synthesized on hot-pressed Cu thin film exhibit superior field effect mobility and significantly reduced device-to-device variation.

Investigation on Multiple Cylindrical Holes Casing Treatment for Transonic Axial Compressor Stability Enhancement

Casing treatment is one possible way of regaining axial compressor operating range. However, most of casing treatments extend the operating range with the cost of efficiency penalty. A new form of multiple cylindrical holes casing treatment(MHCT) with pre-swirl blowing for the NASA Rotor-37 has been designed based on profound understanding of the stall inception. Unsteady numerical simulations have been performed for Rotor-37 with and without MHCT. Parametric studies of the total extraction holes area and their axial locations show that the compressor performance deteriorates as the area ratio increases but the stall margin is extended and there is an optimum extraction holes axial location for stall margin extending. The better configuration of MHCT could extend the stall margin by 6.2% with only 0.23% peak efficiency reduction. Detailed analysis of the physical mechanism behind the stall margin improvement shows that the casing treatment could eliminate the passage blockage by suppressing breakup of tip leakage vortex and decrease the blade load in tip region, which both contribute to improve stall margin of transonic axial compressors.