Closed-Loop Stability Monitoring of Axial Flow Compression Systems

Monitoring systems are proposed for the detection of incipient instability in axial flow compression systems. The work employs generic features associated with the response to noise inputs of systems bordering on instability. Based on these generic features, a closed-loop monitoring system is proposed. Numerical simulation is used to illustrate the operation of the proposed closed-loop monitoring system.     

Unitive analysis schemes on problems of multiple moving boundaries with 3-D liquid-solid multiple nonlinear coupling for uplift of anchored liquid storage tanks

I.Intr0ducti0nAnchored1iquidstoragetanksareextensivelyusedinbusiness,nuclearpowerplants,spaceflightandpetrochemicalindustry.Theystoragepetrochemicalproductions0fover9Opercentintheworld.Theanchoredliquidstoragetanksarecontinuelydamagedduringearthquakestoha…     

海堤越浪的数值模拟

基于RANS方程和两方程湍流模型,采用有限体积法,将人射波波场作为人工的分布源项加人动量方程,提出了适用于VOF方法的源造波一消波技术。通过对行波及驻波的计算,分别考察了数值波浪水槽前端及末端消波段的有效性。在本文建立的数值波浪水槽内对规则波在海堤上爬高和越浪过程进行了数值模拟,并将计算结果与现有实验结果进行了比较。验证计算结果表明,数值模拟结果较好地复演了海堤越浪过程。为了研究模型尺度对越浪量的影响,文中设计了一组满足重力相似但具有不同几何比尺的数值实验模型。系列数值实验结果表明,若按重力相似换算越浪量,计算结果与实验预报值间的偏差随模型比尺的增大和堤前波浪破碎强度的增强而增大,建议在进行越浪物理模型实验时需进一步考虑模型比尺对原型预报值的影响。     

Flux‐corrected transport technique for open channel flow

In modeling flow in open channels, the traditional finite difference/finite volume schemes become inefficient and warrant special numerical treatment in the presence of shocks and discontinuities. The numerical oscillations that arise by making use of a second‐ and higher‐order schemes require some additional smoothing mechanism. A characteristic feature of high‐resolution schemes lies in smooth capturing of the shock fronts. This paper provides a general formulation for a flux‐corrected transport algorithm to the one‐dimensional open channel flow equations. The preliminary results presented show that the present algorithm is an efficient, conservative and robust tool that can be easily coded. To demonstrate the robustness of the present formulation, results are compared with other published numerical results, experimental data and analytical solutions when available. In particular, a comprehensive study on the effect of the source term, dry bed, variable width channel, steep sloping channel and flow with mixed flow conditions (as in a hydraulic jump) has been carried out to test the efficacy of the present algorithm. Copyright © 1999 John Wiley & Sons, Ltd.     

MODELLING OF FLOW IN RECTANGULAR SEDIMENTATION TANKS BY AN EXPLICIT THIRD-ORDER UPWINDING TECHNIQUE

A new numerical model has been developed to simulate the transport of dye in primary sedimentation tanks operating under neutral density conditions. A multidimensional algorithm based on a new skew third-order upwinding scheme (STOUS) is used to eliminate numerical diffusion. This algorithm introduces cross-difference terms to overcome the instability problems of the componentwise one-dimensional formulae for simulating multi-dimensional flows. Small physically unrealistic overshooting and undershooting have been avoided by using a well-established technique known as the universal limiter. A well-known rotating velocity field test was used to show the capability of STOUS in eliminating numerical diffusion. The STOUS results are compared with another third-order upwinding technique known as UTOPIA. The velocity field is obtained by solving the equations of motion in the vorticity–streamfunction formulation. A k– ϵ model is used to simulate the turbulence phenomena. The velocity field compares favourably with previous measurements and with UTOPIA results. An additional differential equation governing the unsteady transport of dye in a steady flow field is solved to calculate the dye concentration and to produce flow-through curves (FTCs) which are used in evaluating the hydraulic efficiency of settling tanks. The resulting FTC was compared with both measurements and numerical results predicted by various discretization schemes. © 1997 by John Wiley & Sons, Ltd.     

着火油罐燃烧特性的理论分析

本文利用自行建立的油罐火灾燃烧特性通用模型,计算得到了燃烧速度、火焰高度,火焰跳动频率和平均温度等油罐燃烧特性的变化规律,并深入探讨了油品燃烧速度在油罐直径、风速、环境温度和油位等因素影响下的变化趋势。为了验证理论计算的准确性,将计算结果与汽油和柴油储罐的燃烧实验数据进行了对比,获得了较为满意的结果。     

叶轮机械内部不稳定流动现象的研究

叶轮机械的内部流动的不稳定现象-喘振与失速,不但影响了叶轮机械的性能,而且限制了叶轮机械的运行范围．本文采用了混沌理论的SVD(Singular Value Decomposition)方法,通过构造相空间的轨迹图(Phase Portrait),分析了离心压气机的失速和诱导轮(Inducer)的气化过程的不稳定现象．结果表明．SVD方法可以用来分析叶轮机械的不稳定现象．