燃气--蒸汽联合循环无旁通烟囱的分析

分析无旁通烟囱燃气－－蒸汽联合循环的特点,指出燃机启动会对余热锅炉产生热冲击,提出根据机组的实际运行情况来确定是否设置旁通烟囱,可供联合循环方案设计者及运行人员参考。     

An investigation of the friction and wear behaviors of micrometer copper particle‐ and nanometer copper particle‐filled polyoxymethylene composites

Micrometer and nanometer copper particle‐filled polyoxymethylene composites (coded as POM‐micro Cu and POM‐nano Cu, respectively) were prepared by compression molding. The compression strength and tensile strength of the composites were evaluated with a DY35 universal materials tester. An RFT‐III reciprocating friction and wear tester was used to examine the tribological properties of the composites. The elemental compositions in the transfer films and the chemical states of the elements in the composite‐worn surfaces were analyzed with electron probe microanalysis and X‐ray photoelectron spectroscopy, while the surface morphologies were observed with scanning electron microscopy. It was found that Cu( CH₂ O )_n was produced in sliding of a POM‐nano Cu pin against an AISI 1045 steel block and Cu₂O was produced in sliding of a POM‐micro Cu pin against the same counterface. POM‐micro Cu exhibited higher copper concentration in the transfer film compared with POM‐nano Cu, and the transfer film of the former was thick and patchy compared with that of the latter. It was also found that micrometer and nanometer copper particles as fillers in POM exhibit a distinctive size effect in modifying the wear mechanisms of the composites. In other words, the wear mechanism of POM‐micro Cu is mainly scuffing and adhesion, while that of POM‐nano Cu is mainly plastic deformation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2404–2410, 2000     

无旁通烟囱燃气_蒸汽联合循环机组的运行维护和停运

论述了无旁通烟囱燃气－蒸汽联合循环机组运行维护和停运的特点,探讨了它与火力发电厂和有旁通烟囱联合循环的不同之处,总结了机组运行维护和停动的经验,可供运行人员和设计人员参考。     

The tribological behaviour and mechanism of action of sulphur-containing borate esters in rape seed oil

Three sulphur-containing borate esters and one borate ester based on boric acid and n-octanol were synthesised. The antiwear and friction-reducing properties of these synthetic compounds as additives in rape seed oil were examined using a four-ball machine. The relationship between the additive structure and tribological properties was explored, and the lubrication mechanisms of the additives investigated. The worn surfaces of a steel ball lubricated with the additive-containing rape seed oil were analysed using X-ray photoelectron spectroscopy and scanning electron microscopy. The elemental compositions of, and distributions in, the worn steel surfaces were determined with an electron probe micro-analyser. It was found that sulphur-containing borate esters as additives in rape seed oil at appropriate concentrations can be effective in improving antiwear and friction-reducing behaviour. The rape seed oil base stock experiences competitive adsorption and tribochemical reactions with additives on the rubbing steel surface. The introduction of the active element sulphur into the borate ester additives functions to improve the tribological behaviour of the base stock by increasing the rate of formation of a protective layer on the rubbing steel surface. However, the tribological behaviour of the additives is not dependent on the number of sulphur atoms in the additive molecules, and further work is needed to investigate the possible dependence of this behaviour on the ratio of boron to sulphur in the additive molecules.     

燃煤电厂烟气超低排放与深度节能综合技术研究及应用

为实现超低排放与深度节能,以某电厂为例,采用系统协同处理方法,研究分析了烟气超低排放与深度节能综合技术路线,提出了锅炉低氮燃烧器改造、电除尘器低低温与脉冲电源协同提效、电除尘器蒸汽加热与热风吹扫、脱硫托盘与交互喷淋协同提效、湿式电除尘器及其废水零排放、MGGH与凝结水加热器耦合节能等技术方案,结果表明,超低排放改造效果优于国家超低排放限值要求,同时机组能耗降低,烟气余热回收,机组对煤种的适应性也得到提升,可为同类项目提供参考。     

基于耦合算法的类人机器人模仿学习控制方法

为提高类人机器人模仿学习的准确性及效率,建立了一种改进的粒子群算法优化超限学习机的模仿学习模型。采用非线性动态系统对示教时的相关数据进行建模;以动态自适应策略改进粒子群算法的惯性权重,并利用改进后的粒子群算法对超限学习机的网络参数进行寻优;利用该耦合学习模型对模仿学习动态系统的参数进行学习,并重现了模仿学习动作。实验结果表明,该耦合算法应用在类人机器人模仿学习方面具有很好的拟合精度、自适应性及泛化能力,重现模仿学习动作时的平均误差为0.0172。     

Construction and flame-retardant performance of layer-by-layer assembled hexagonal boron nitride coatings on flexible polyurethane foams

We first prepared a novel hexagonal boron nitride (h-BN) nanosheet filled flame-retardant coating on the surface of flexible polyurethane foams (FPUFs) by a layer-by-layer assembly method to improve the fire safety of the FPUFs. The microstructures and compositions of the coatings could be well tailored by the alteration of the concentrations of the h-BN dispersions; this resulted in obvious improvements in the thermal stability and flame-retardant properties for the FPUFs under optimal conditions. Particularly, cone calorimetry testing confirmed that the FPUFs coated with a proper amount of h-BN nanosheets effectively reduced the peak of the heat-release rate (50.1%) and CO production (53.8%) of the FPUFs, which demonstrated excellent flame-retardant performance. The excellent flame-retardant properties were attributed to the physical barrier and tortuous-path effects and anisotropic thermal conductivity of the h-BN nanosheets; these retarded the transfer and diffusion of heat toward the polymer matrix. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47839.     

Space‐Charge‐Stabilized Ferroelectric Polarization in Self‐Oriented Croconic Acid Films

Great progress has been made recently in molecular ferroelectrics with properties even comparable to those of inorganic ferroelectrics. However, it is difficult to develop basic thin films and devices for practical applications since most molecular ferroelectrics are uniaxial. The single polar axes of crystallites inside their films, if available, are usually oriented randomly. These can induce the components without contribution to ferroelectric polarization and a large depolarization electric field to suppress polarization. In this work, it is demonstrated that uniaxial croconic acid films in two‐terminal devices, deposited by thermal evaporation, can show effective ferroelectric polarization and nonvolatile memory switching behavior with small coercive fields of 11–30 kV cm^?1. The polar c‐axes in thick crystalline films (>500 nm) are found to be self‐oriented nearly at a desired direction. With the assistance of trapped charges, stable ferroelectric polarization can be achieved, in spite of the existence of nonferroelectric components. These may pave a way to utilize uniaxial molecular ferroelectrics for various applications, such as gate dielectrics, electrets, and memory devices.     

Highly Efficient 1D/3D Ferroelectric Perovskite Solar Cell

With the capability to manipulate the built-in field in solar cells, ferroelectricity is found to be a promising attribute for harvesting solar energy in solar cell devices by influencing associated device parameters. Researchers have devoted themselves to the exploration of ferroelectric materials that simultaneously possess strong light absorption and good electric transport properties for a long time. Here, it is presented a novel and facile approach of combining state-of-art light absorption and electric transport properties with ferroelectricity by the incorporation of room temperature 1D ferroelectric perovskite with 3D organic–inorganic hybrid perovskite (OIHP). The 1D/3D mixed OIHP films are found to exhibit evident ferroelectric properties. It is notable that the poling of the 1D/3D mixed ferroelectric OIHP solar cell can increase the average V_oc can be increased from 1.13 to 1.16 V, the average PCE from 20.7% to 21.5%. A maximum power conversion efficiency of 22.7%, along with an enhanced fill factor of over 80% and open-circuit voltage of 1.19 V, can be achieved in the champion device. The enhancement is by virtue of reduced surface recombination by ferroelectricity-induced modification of the built-in field. The maximum power point tracking measurement substantiates the retention of ferroelectric-polarization during the continued operation.     

Numerical modeling of permeability evolution based on degradation approach during progressive failure of brittle rocks

The permeability evolution of rock during the progressive failure process is described.In combination with the strength degradation index,the degradation formulas of s and a,which are dependent on the plastic confining strain component,the material constants of Hoek–Brown failure criterion are presented,and a modified elemental scale elastic–brittle–plastic constitutive model of rock is established.The relationship between volumetric strain and permeability through tri-axial compression is investigated.Based on the above,a permeability evolution model is established.The model incorporates confining pressuredependent degradation of strength,dilatancy and corresponding permeability evolution.The model is implemented in FLAC by the FISH function method.The permeability evolution behavior of rock is investigated during the progressive failure process in a numerical case.The results show that the model is capable of reproducing,and allowing visualization of a range of hydro-mechanical responses of rock.The effects of confining pressure on degradation of strength,dilatancy and permeability evolution are also reflected.