气脉冲除灰技术燃烧和除灰过程研究

中国电站锅炉燃用大量的未经洗选的劣质煤，导致严重的锅炉积灰问题，尤其是125-600MWe的大型锅炉的回转式空气预热器堵灰更加严重。积灰不仅使锅炉热效率下降，而且堵塞烟气流道，影响了锅炉的正常运行。已有的各种除灰器都有较大的局限性。中国科学院力学研究所燃烧研究实验室根据我国国情开发出了燃烧气脉冲除灰技术，并在30多台大型电站锅炉应用取得了很好的效果。为了理解气脉冲除灰的工作过程，掌握运行规律，解释应用中出现的问题，以提高技术水平和开发新产品，尚需对气脉冲除灰的燃烧和除灰过程做更深入的研究。本论文工作针对燃烧气脉冲除灰技术在实际使用中提出的问题，开展了实验室研究。主要研究了乙炔、水煤气、液化石油气和甲烷四种燃料在气脉冲实验装置中的火焰传播情况和压力波形。研究了混合比、阻塞比和出口截面比对火焰速度和压力峰值的影响。在现有点火条件下找到了在静止混合气体中四种燃料的贫点火极限和乙炔在有一定流速时的贫点火极限；比较了燃烧室内乙炔空气混合物静止时和有一定流速时的爆炸压力峰值。初步搞清了各种因素对火焰速度和压力波形的影响，实验结果对实际应用有指导作用。为了理解火焰传播和压力波形之间的关系，用燃烧室内压力均匀的简化模型，计算了压力波形并且与实验结果进行了对照，由此推算了湍流燃烧速度并探讨了各种因素对它的影响。用考虑了管内有压力波传播的一维简化模型，计算了火焰传播过程中燃烧室两端的压力波形和火焰面前后的气流速度，以及不同时刻的燃烧室内气体流速分布。估算了气流剪切力的量级，进行了模拟积灰的气脉冲对比实验，测量了同一气脉冲条件下两种厚薄不同板的振动加速度值及其随时间和空间的衰减情况。还得到了压力在空间的衰减变化情况。定性地研究了积灰脱落机理，初步认为：对于粘结灰只有振动才有效，气流的剪切不能除去粘结灰。

An Analytical Solution for Three-Dimensional Diffraction of Plane P-Waves by a Hemispherical Alluvial Valley with Saturated Soil Deposits

An analytical solution for the three-dimensional scattering and diffraction of plane P-waves by a hemispherical alluvial valley with saturated soil deposits is developed by employing Fourier-Bessel series expansion technique. Unlike previous studies, in which the saturated soil deposits were simulated with the single-phase elastic theory, in this paper, they are simulated with Biot's dynamic theory for saturated porous media, and the half space is assumed as a single-phase elastic medium. The effects of the dimensionless frequency, the incidence angle of P-wave and the porosity of soil deposits on the surface displacement magnifications of the hemispherical alluvial valley are investigated. Numerical results show that the existence of a saturated hemispherical alluvial valley has much influence on the surface displacement magnifications. It is more reasonable to simulate soil deposits with Biot's dynamic theory when evaluating the displacement responses of a hemispherical alluvial valley with an incidence of P-waves.

NOx emission and thermal efficiency of a 300 MWe utility boiler retrofitted by air staging

Full-scale experiments were performed on a 300 MWe utility boiler retrofitted with air staging. In order to improve boiler thermal efficiency and to reduce NOx emission, the influencing factors including the overall excessive air ratio, the secondary air distribution pattern, the damper openings of CCOFA and SOFA, and pulverized coal fineness were investigated. Through comprehensive combustion adjustment, NOx emission decreased 182 ppm (NOx reduction efficiency was 44%), and boiler heat efficiency merely decreased 0.21%. After combustion improvement, high efficiency and low NOx emission was achieved in the utility coal-fired boiler retrofitted with air staging, and the unburned carbon in ash can maintain at a desired level where the utilization of fly-ash as byproducts was not influenced.

Contribution of inherent organic carbon to the bulk delta C-13 signal in loess deposits from the arid western Chinese Loess Plateau

IEECAS SKLLQG

Application Of (CS)-C-137 fingerprinting technique to interpreting sediment production records from reservoir deposits in a small catchment of the Hilly Loess Plateau；China

IEECAS SKLLQG

Are Chinese loess deposits essentially continuous?

IEECAS SKLLQG

Tectonic uplift in the northern Tibetan Plateau since 13.7 Ma ago inferred from molasse deposits along the Altyn Tagh Fault

IEECAS SKLLQG