挠性转子振型平衡

对汽轮机柔性转子采用振型平衡法进行高速动平衡的方法做了阐述,并介绍了一些平衡标准及一些实用的平衡方法。     

P-wave检测PCCP管断丝原理的三维数值仿真

预应力钢筒混凝土管道在服役期间会由于钢丝断裂而引发爆管,影响管道的使用寿命。P-wave是检测大口径PCCP管断丝的重要方法,采用三维电磁场有限元方法,仿真P-wave检测E型PCCP管道。对于有阴极保护钢带的E型管道,根据检测信号幅值和相位的变化规律可以确定非钢带处断丝的数量和轴向位置,结合PCCP的受力特征,判定断丝的环向位置。同时通过敏感性分析,探究了P-wave的检测原理,P-wave借助屏蔽盘隔绝直接耦合分量,使得激励场垂直穿过管壁,在钢丝内激发出涡流效应,从而实现近场检测;发生断丝时钢丝断口附近电流密度下降,导致感应磁场分布发生变化,检测信号的幅值和相位也随之变化。该研究为大口径PCCP管断丝检测实际应用提供了理论依据。     

9FA重型燃气轮机转子高速动平衡研究

本文对9FA重型燃气轮机转子高速动平衡试验方法、平衡方法、平衡设备等做了详细的介绍,同时也介绍了GE公司的低速平衡方法,为9FA燃气轮机转子今后的高速动平衡提供了可资参考和借鉴的经验.     

凝结水再循环管道的防振动设计

本根据可能引发凝结水再循环管道振动的原因，指出调节阀布置在U形管下部水平管段上是防止该管道振动有效而经济的措施，并从管道及其旁路阀布置、管件配置和支吊架设计等几个方面提出防止该管道振动一些的设计方法。     

基于等线长迭代的特高压直线塔地线不平衡张力计算

特高压直线塔地线金具多次因不均匀覆冰发生事故。首先采用不平衡张力的数值计算模型,并给出张力初始值的取值方法和收敛判断条件。然后计算分析了特高压输电线路不同档距、档数、高差、冰厚、串长、大小档等多种情况时直线塔地线的不平衡张力。结果表明减少耐张段档数、缩小档距、降低高差、路径选择中尽量避开冰区较重的地方、增加地线悬垂串长度、排位时尽量使档距均匀分布等均可降低直线塔地线的不平衡张力。对新建工程和已建工程,分别提出了降低地线不平衡张力差的对策,可为后续特高压输电线路的设计提供参考。     

转子现场平衡与平衡机上平衡试验的比较

本文讨论大中型汽轮发电机组或燃气轮机发电机组在检修期间转子的高速平衡试验问题。到底在现场进行高速平衡试验还是将转子运到专门的高速平衡试验装置上进行平衡?哪种方案对用户更合适而且平衡精度更高些?本文旨在为发电厂机组大修期选择合适的平衡方案提供一点参考。     

水下管道局部冲刷平衡深度预测方法

为了更准确地预测水下管道局部冲刷平衡深度,提出了一种预测局部冲刷平衡深度的新方法,通过数值模拟手段,利用有限体积法来求解N-S方程和标准κ-ε方程,得到了冲刷平衡时的水下管道绕流场,进而分析了冲刷坑内过流量,通过数据拟合得到与冲刷坑深度有关的冲刷坑过流量经验公式,并应用基于该公式的冲刷平衡深度预测方法和已有方法对不同水流条件下冲刷坑深度进行了预测。结果表明,该方法预测结果与试验结果更接近,预测误差在20%以内,明显高于已有方法,为水下管道局部冲刷平衡深度预测提供了技术手段。     

基于元体能量平衡法的垂直U型埋管换热特性的研究

基于元体能量平衡法建立了垂直U型埋管的传热模型,模型考虑了流体温度的沿程变化,并通过引入热干扰角与等效传热间距反映两管脚间的热干扰问题,使之更符合实际的传热情况。通过所建模型对U型埋管的换热特性进行了数值模拟,结果表明:增加土壤与回填物导热系数、管脚间距、管内流体流量及减小管脚热干扰角与进口流体温度(供热工况下)均可以增强埋管的换热效果,其中土壤导热性影响最为显著。但回填物导热系数不可无限制增大,其大小还要考虑对增强管脚间热干扰的影响及其与管脚间距的相互关联性。同时,流量的增加要考虑对流动阻力增加的限制,可以采用变流量设计来进行调节与优化。此外,为了充分发挥地源热泵的能效,实际设计应该考虑埋管、热泵及负荷三者间的相互匹配性。     

某60Hz、185MW汽轮机转子高速动平衡试验试重大小及位置探究

针对汽轮机转子个性化设计的特点,文章结合在250t试验台位上进行转子高速动平衡试验所积累的经验。对全新设计的某60Hz、185MW汽轮机转子厂内动平衡试验平衡块试加重量及方位角进行探究。实践证明．文章总结的方法可以有效地缩短转子动平衡时间,并可以推广应用到其它转子厂内高速动平衡试验上。     

热力设备水冲击的原因分析及防范措施

热力管系由于水冲击故障而振动、损伤 ;重者 ,热力设备焊口撕裂乃至爆破。一些用热单位就曾发生过多起热力管系及锅炉设备水击故障 ,压力容器也曾发生过焊口炸裂 ,容器严重变形、设备报废等。水冲击 ,又称“水锤”。当水在管道中流动或蒸汽进入含水的管道或容器中时 ,因速度突然发生变化导致该处压力突变 ,形成压力波并沿管道或容器壁传播的现象。在热力系统中当输出的蒸汽与少量的积水相遇时 ,部分热量被水迅速吸收 ,使少量蒸汽冷凝成水 ,体积突然缩小 ,形成局部真空 ,引起周围水介质的高速冲击 ,产生巨大的音响和震动 ,另外 ,在管道内 ,流…     

Leak-before-break application in US light water reactor balance-of-plant piping

This paper describes the criteria and methodology for a leak-before-break (LBB) program for high energy balance-of-plant (BOP) nuclear piping in the United States. LBB, the analytical demonstration that high toughness piping will leak detectably before catastrophic failure, can be applied to any operational or pre-operational light water reactor plant to minimize pipe rupture hardware and to discount pipe rupture dynamic effects.

The general methodology described herein, encompasses applicable US NRC regulatory requirements and incorporates experience gained in the licensing process of actual LBB programs. First, candidate piping systems must be carefully screened to verify that they are not subject to failure by phenomena that would adversely affect the accurate evaluation of flaws. Next, pipe stresses, material properties, and leak detection capabilities are gathered for the fracture mechanics and fluid mechanics analyses. At the piping locations which have the least favorable combination of material properties and stress, a crack is postulated which is of sufficient size that the resulting leakage will be detected by installed leak detection systems. Finally, LBB is demonstrated if the postulated crack remains stable even if a seismic event takes place before the crack is discovered and repaired. An LBB example is presented in this paper for a generic pressurizer surge line, and reflects the consideration of flow stratification on LBB analyses.     

Structural modelling and testing of failed high energy pipe runs: 2D and 3D pipe whip

The sudden rupture of a high energy piping system is a safety-related issue and has been the subject of extensive study and discussed in several industrial reports (e.g. [2], [3], [4]). The dynamic plastic response of the deforming pipe segment under the blow-down force of the escaping liquid is termed pipe whip. Because of the potential damage that such an event could cause, various geometric and kinematic features of this phenomenon have been modelled from the point of view of dynamic structural plasticity. After a comprehensive summary of the behaviour of in-plane deformation of pipe runs [9], [10] that deform in 2D in a plane, the more complicated case of 3D out-of-plane deformation is discussed. Both experimental studies and modelling using analytical and FE methods have been carried out and they show that, for a good estimate of the “hazard zone” when unconstrained pipe whip motion could occur, a large displacement analysis is essential. The classical, rigid plastic, small deflection analysis (e.g. see [2], [8]), is valid for estimating the initial failure mechanisms, however it is insufficient for describing the details and consequences of large deflection behaviour.     

Leak-before-break: An integrated approach for high energy piping

An integrated approach that involves system design, thermal hydraulics, materials, and fracture mechanics analyses to assure that pipe failure is highly unlikely is described. This approach is based on a leak-before-break (LBB) premise and includes through-wall flaw detectable leakage, through-wall flaw stability, and part-through-wall flaw fatigue crack propagation calculations. A successful application of LBB can reduce the amount of excessive pipe rupture restraint hardware. Assuring LBB not only reduces initial construction, future maintenance, and radiation exposure costs, but the overall safety and integrity of the plant are improved. This last benefit comes about from gaining additional insight into the piping systems and their capabilities. Details of the LBB methodology are presented here with specific examples for two pressurized water reactor lines (one inside containment fabricated of stainless steel, and the other outside containment made from ferritic steel). The application of this approach at Beaver Valley Power Station—Unit 2 indicates that pipe rupture hardware is not necessary for stainless steel lines inside containment as small as 6-in (152 mm) nominal pipe size that have passed screening criteria designed to eliminate potential problem systems (such as the feedwater system). Similarly, some ferritic steel lines as small as 3-in (76 mm) diameter (outside containment) can qualify for pipe rupture hardware elimination.     

A leak-before-break strategy for CANDU primary piping systems

Recent advances in elastic-plastic fracture mechanics have made it possible to assess the stability of cracks in ductile piping systems. These technological developments have been used by Ontario Hydro as the nucleus of an approach for demonstrating that CANDU primary heat transport piping systems will not break catastrophically; at worst they would leak at a detectable rate. This leak-before-break approach has been taken on the Darlington nuclear generating station as a design stage alternative to the provision of pipe whip restraints on large diameter, primary heat transport system piping. Positive conclusions reached via this approach are considered sufficient to exclude the requirement to provide protective devices, such as pipe whip restraints.

In arriving at the proposed leak-before-break approach a review of current and proposed leak-before-break licensing positions of other jurisdictions (particularly those in the United States and the Federal Republic of Germany) was carried out. The approach presented makes use of recent American developments in the area of elastic-plastic fracture mechanics. It also gives consideration to aspects which are unique to the pressurized heavy water (CANDU) reactors used by Ontario Hydro.

The present paper describes the proposed leak-before-break approach and illustrates its use by applying it to the Darlington generating station primary heat transport system pump suction piping.     

Development of USNRC standard review plan 3.6.3 for leak-before-break applications to nuclear power plants

In the United States, it is now permissible to eliminate the dynamic effects of postulated high energy pipe ruptures from the design basis of nuclear power plants using ‘Leak-Before-Break’ (LBB) technology. To provide review guidance for the implementation of LBB, a new Standard Review Plan (SRP) 3.6.3 was issued for public comment. Based upon public comments received and advances in fracture mechanics application, further development of SRP 3.6.3 is in progress.

SRP 3.6.3 will outline the review procedures and acceptance criteria for LBB licensing applications. A deterministic fracture mechanics evaluation accounting for material toughness will be required. Margins on load, crack size, and leakage will be specified and the load combination methods and leakage detection sensitivity will be described. Piping particularly susceptible to failure from potential degradation mechanisms will be excluded from the application of LBB. The design basis of containment, emergency core cooling systems, and environmental qualification of equipment in the context of LBB applicability will be clarified.     

Leak-before-break qualification of primary heat transport piping of 500 MWe Tarapur atomic power plant

The advent of Leak-Before-Break (LBB) concept has now replaced the traditional design basis event of the Double-Ended-Guillotine-Break (DEGB) to design the Primary Heat Transport (PHT) system piping of the Pressurised Heavy Water Reactor (PHWR) and Pressurised Water Reactor (PWR). This approach is being adopted to design the PHT system piping of 500 MWe Indian PHWR to be built at Tarapur (Tarapur Atomic Power Plant 3 and 4). The LBB concept basically demonstrates through fracture mechanics analysis that there is negligible chance of any catastrophic break of PHT pipes without prior indication of leakage. There are several steps in this work of LBB qualification, namely, evaluation of loads on the piping components, generation of tensile and fracture properties of PHT pipe base and weld material, determination of leakage size crack (LSC) and the elastic–plastic fracture mechanics (EPFM) and limit load analysis of the piping components with postulated LSC to evaluate the critical load at unstable ductile tearing and the limit load, respectively. The paper deals with the fracture analysis of the straight pipes and elbows of three pipe lines in the PHT system of TAPP 3 and 4. Three crack configurations are considered in the analysis. These are throughwall circumferential crack at the weld location of straight pipe and extrados of the elbow and throughwall axial crack at the elbow crown. In all the cases, necessary factor of safety with respect to the anticipated safe shutdown earthquake (SSE) load and LSC are shown to be more than the minimum required values for LBB qualification.     

A practical application of an evaluation model for the restraint effect of pressure-induced bending on a plastic crack opening

This paper presents an evaluation model for the restraint effect of pressure-induced bending (PIB) on the opening of a circumferential through-wall crack (TWC) and a result of its application to the calculation of crack-opening displacement (COD) of postulated cracks for a practical leak-before-break (LBB) analysis. Three-dimensional finite element analyses with different crack lengths, restraint conditions, pipe geometries, magnitudes of internal pressure, and material tensile properties were used to investigate the influence of each parameter on the PIB restraint for the plastic COD. From these investigations, we proposed an evaluation model based on elastic–perfectly plastic behavior. Comparison with finite element analysis results demonstrated that the proposed model reliably estimated the PIB restraint effect on the plastic crack opening of a circumferential TWC and properly reflected the effect of each parameter within the range over which the analytical expression was derived. The model was then used to calculate restrained CODs of postulated cracks for a practical LBB analysis. When plastic crack behavior was considered, the PIB restraint effect was considerable for some LBB analysis cases of the primary piping systems in a typical nuclear power plant. This effect was estimated to be negligible by existing linear elastic-based models.     

某核电堆型蒸汽发生器排污系统设计改进

根据全范围事故分析结果,在发生蒸汽发生器传热管破裂(SGTR)事故中,为使发生故障的蒸汽发生器水位不会上升太快,需通过蒸汽发生器排污系统排污管线来控制故障蒸发器的水位和压力。通过对蒸汽发生器排污系统进行设计改进,提高系统的设计标准,将破损蒸汽发生器内漏液排向内置换料水箱,使破损蒸汽发生器降压,同时限制破损蒸汽发生器水位,防止破损蒸汽发生器满溢,满足蒸汽发生器排污系统在设计基准事故工况下承担安全功能的要求。改进后的蒸汽发生器排污系统满足国内三代核电技术的要求,为国内三代核电的安全性提供理论依据。     

压水堆核电厂二回路系统管道热效率的影响因素分析

在压水堆核电厂热经济性分析中,管道热效率的分析往往不被研究者所重视。首先从管道热效率的定义出发,给出了管道热效率的计算表达式,以及各种管道损失的计算方法。然后针对某些影响管道热效率的因素,同时也对蒸汽动力转换系统循环热效率产生影响的问题,分析了影响管道热效率的因素变化对蒸汽动力转换系统循环热效率和压水堆核电厂全厂热效率的影响。最后,以某990MW核电机组为例,通过计算分析了如主蒸汽管道疏水门泄漏蒸汽、厂用蒸汽、主蒸汽管道散热、蒸汽发生器排污等对管道热效率、蒸汽动力转换系统循环热效率及全厂热效率的影响。结果表明,上述因素变化均导致管道热效率降低和全厂热效率的降低,但不同因素变化对全厂热效率的影响机理却存在较大的差别。     

Development of criteria for protection against pipe breaks in LWR plants

A proving test for the structural integrity of safety-related carbon steel piping components in light water reactor plants was conducted in NUPEC as a four-year project, in which the applicability of the Leak-Before-Break (LBB) concept to protect against a postulated pipe break was reviewed in parallel with the clarification of fracture behavior. The comprehensive review of LBB applications consists of applicable piping systems, premise for evaluations, procedure and evaluation findings. The review concluded that present practice for design, fabrication, installation and operation can ensure structural integrity and moreover postulated that instantaneous pipe break as a basis for structural design is unrealistic if certain conditions are met. Fatigue is the only failure mechanism to be considered to affect the piping system.