2150 t/h切圆燃烧锅炉旋流指数的试验研究

为减小切圆燃烧锅炉的汽温偏差,以2 150 t/h四角切圆燃烧锅炉为试验对象,研究了炉膛火焰中心与旋流指数的关联以及燃烧调整对旋流指数的影响.在试验分析的基础上,结合汽温偏差变化,得到了炉膛火焰中心随旋流指数的变化轨迹.从风箱炉膛压差控制的角度进行了计算,并分析了加大配风不均衡性对旋流指数的影响.结果表明:加大配风不均衡性会导致旋流指数增大；旋流指数与负荷不存在确定的对应关系；降低氧体积分数过程中旋流指数减小,降低氧体积分数后降负荷过程中旋流指数的变化幅度增大,易引起汽温偏差增大和超温现象；燃烧器下摆会增大旋流指数；反切分离燃尽风(SOFA)过大时,反向旋流指数的增大同样会引起两侧汽温偏差增大.     

低品质汽油的催化改质

直馏汽油和焦化汽油属于辛烷值较低的低品值汽油。经裂化催化剂催化改质后，C3～C4产率可以达到30％～40％，其中C_3= C_4=约占60％～70％。催化改质后，汽油族组成发生变化，烷烃和环烷烃含量降低，芳烃含量大幅度增加，从而使汽油的MON提高10～20个单位。     

Acquiring Recursive and Iterative Concepts with Explanation-Based Learning

In explanation-based learning, a specific problem's solution is generalized into a form that can be later used to solve conceptually similar problems. Most research in explanation-based learning involves relaxing constraints on the variables in the explanation of a specific example, rather than generalizing the graphical structure of the explanation itself. However, this precludes the acquisition of concepts where an iterative or recursive process is implicitly represented in the explanation by a fixed number of applications. This paper presents an algorithm that generalizes explanation structures and reports empirical results that demonstrate the value of acquiring recursive and iterative concepts. The BAGGER2 algorithm learns recursive and iterative concepts, integrates results from multiple examples, and extracts useful subconcepts during generalization. On problems where learning a recursive rule is not appropriate, the system produces the same result as standard explanation-based methods. Applying the learned recursive rules only requires a minor extension to a PROLOG-like problem solver, namely, the ability to explicitly call a specific rule. Empirical studies demonstrate that generalizing the structure of explanations helps avoid the recently reported negative effects of learning.     

Flow of viscoelastic polymer solutions in mixed beds of particles

New extensive pressure drop-flow rate data are reported for the creeping flow of well characterised viscoelastic polymer solutions through packed beds of mixed size spheres and of spheres and cylinders. It is established that the effective mean surface diameter is adequate in correlating the pressure loss data in flow through packed beds of mixed size and shape. A distinct correlation exists between the excess pressure loss observed with viscoelastic fluids and the Weissenberg number.     

Optimal fault margin in a computer system

This paper suggests a stochastic model how to determine a fault margin in a computer system, who fails when the total number of hidden faults exceeds a threshold level N of tolerance: A fault occurs at a non-homogeneous Poisson process, and (i) becomes system failure with probability p₁, (ii) becomes hidden fault with probability p₂ and is accumulated, or (iii) is removed with probability p₃. The expected cost rate to system failure is derived, and an optimal number N^* to minimize it is discussed. A numerical example is finally given.     

催化裂化汽油组成对其储存安定性的影响

 通过对催化裂化（FCC）汽油组成、诱导期、吸光度等性质指标的跟踪测试，考察了影响FCC汽油安定性的主要因素。结果表明，FCC汽油中除按产品质量要求严格控制含量的烯烃、总硫及硫醇是影响FCC汽油不安定的主要因素外，共轭二烯烃的存在严重影响FCC汽油的储存安定性，含氮化合物是油品变色的关键物质，而大部分酚类化合物具有抗氧化性，它们的存在有利于延长氧化变质诱导期，但对FCC汽油生胶、变色具有酸性催化剂作用。酚含量越多的FCC汽油，其诱导期越长，但油品变色也越快。FCC汽油的酚含量较高（＞200μg/g）时，其诱导期随着二烯值的增大而缩短，储存吸光度随着二烯值、碱性氮含量的增大而增加；酚含量较低（＜120μg/g＝时，汽油颜色稳定，二烯值、碱性氮含量的变化对储存吸光度影响不大，二烯值小至0.7μg/g也可导致诱导期缩短。通过优化催化原料和操作条件、优化调合和添加抗氧防胶剂等措施，可有效地提高FCC汽油的储存安定性。     

The mean flow field generated by a pitched blade turbine: Changes in the circulation pattern due to impeller geometry

The mean flow field in a tank stirred with a pitched blade turbine was measured using a two-component Laser Doppler Anemometer system (LDA). The effects of impeller clearances and impeller geometries (number of blades, blade angle and blade size) on the mean flow field have been studied. The primary pumping number, induced pumping number of the primary circulation loop and the induced pumping number of the secondary circulation loop, which often has been ignored, are reported. The flow patterns and circulation loops are more complex than those traditional ones, which vary with the geometries of the PTD and the clearances.     

石蜡基基础油氧化安定性影响因素的研究

运用数理统计的原理石蜡基基础油的联评数据进行分析，得到石蜡基基础油氧化安定性的主要影响因素是碱性氮，酸值的结论，并对ＨＶＩ基础油标准中的碱性氮指标提出了建议值。     

小浪底导流洞中闸室施工修改体型研究

通过模型试验,对中闸室施工修改体型即预留凹槽方案进行了论证,认为该体型在运用中发生空化的可能性较大,不宜采用;原设计无凹槽体型方案,水流流态较好,水流空化数大于初生空化数,建议采用.对改建施工中需凿除部分,建议采用降低砼标号的方法来减小施工难度.     

Liquid solidification in low peclet number pipe flows

The combined effects of axial conduction and solidification on heat transfer and pressure drop in pipe flows are investigated by the use of a modified Galerkin finite element method. To allow for the upstream heat conduction, the domain of study is extended from X = -∞ to X = -∞ as has been done in previous analyses. As a preliminary study on the effect of axial conduction, the present investigation assumes a superheat ratio that is sufficiently large (T_o > T_f or T_w ≈ T_f) such that solidification begins at a location near X = 0. For numerical convenience, the infinite domain -∞ ≤ X ≤ ∞ is transformed onto a finite domain -1 ≤ z ≤ 1. The energy equation for the liquid-phase is then solved by a modified Galerkin finite element method. For better numerical stability, a procedure is proposed for controlling the numerical error that might propagate from the singular point (X, R) = (O, R_o). The profile of the solid-liquid interface, the heat transfer rate and the pressure drop are presented for various values of Peclet number, Pe = 1, 3, 5, 10 and 30, and for the modified superheat ratio, c = 0.1, 0.5, 5.0, and ∞.