Ontario hydro's leak-before-break approach to Darlington NGS heat transport system piping

The primary objective in our Leak-Before-Break studies is to show how a rational and comprehensive approach can provide an adequate measure of confidence in the assessment of piping integrity such that provision of design features (viz. pipewhip restraints, jet impingement shields) to protect against the dynamic effects of pipe rupture is not necessary. This study is one component of the overall Leak-Before-Break approach adopted at Ontario Hydro.

The results of a review undertaken to evaluate the system transients or events sequences which may subject the piping to a potentially significant increase in loadings are reported. The focus in this paper is to show the approach used in deriving loadings for use in the elastic-plastic fracture mechanics (EPFM) analyses required to demonstrate crack stability.     

Hydroelastic piping vibration analysis by transfer matrices

A compact method is presented for determining the simultaneous acoustic and mechanical steady-state vibrations in three-dimensional piping conveying fluid. The method is based on transfer matrices which are applied for proper members of the piping such as straight pipes and bends and equipment including pumps, valves, accumulators, supports and snubbers. In addition to the high accuracy, the method has the advantage that it involves simultaneous solution of no more than 7 algebraic equations. A numerical instability associated with the transverse waves in the pipe constitutes the main drawback and is solved by a linear transformation leading to a diagonalised transfer matrix of a straight pipe. The method is finally extended to transient vibrations by performing a Fourier inversion from the frequency domain into the time domain on the basis of the theorem of residues.The method has been applied to the steady-state vibration of a reciprocating pump suction line and to the response of a cantilevered L-shaped pipe to an instantaneous valve closure at the fixed end. The results are compared with those obtained by ignoring the hydroelastic coupling between the fluid and the pipe.     

生物质发电厂上料和给料系统工艺分析

生物质电厂上料系统和给料系统是生物质能发电工程的重要组成部分,其系统因工艺复杂、转点较多、设备选型多样化、日常维护不到位等问题导致输送系统故障率较高,而长期安全稳定运行关系到生物质发电厂的经济效益.通过介绍国内4家生物质发电厂上料和给料系统工艺,对比分析各厂上料和给料系统工艺特点及存在的问题.针对上料和给料系统的设计与运行提出了建议,并给出了简化输送系统的工艺方案,以供生物质发电厂上料系统和给料系统设计与运行管理人员参考.     

Non-linear dynamic analysis of piping system using the pseudo force method

Simple piping systems are composed of linear elastic elements and can be analysed using conventional linear methods. The introduction of constraint springs, separated from the pipe with clearance gaps, to such systems to cope with the pipe whip or other extreme excitation conditions introduces non-linearities to the system, such non-linearities being associated with the gaps. Since these spring-damper constraints are usually limited in number, discretely located and produce only weak non-linearities, the analysis of linear systems including these non-linearities can be carried out by using modified linear methods. In particular, the application of pseudo force methods, wherein the non-linearities are treated as displacement-dependent forcing functions acting on the linear system, was investigated.The non-linearities induced by the constraints are taken into account as generalised pseudo forces on the right-hand side of the governing dynamic equilibrium equations. Then an existing linear elastic finite element piping code, EPIPE, was modified to permit application of the procedure. This option was inserted such that the analysis could be performed using either the direct integration method or via a modal superposition method, the Newmark-Beta integration procedure being employed in both methods. The modified code was proof tested against several problems taken from the literature or developed with the non-linear dynamics code, OSCIL. The problems included a simple pipe loop, a cantilever beam and a lumped mass system subjected to pulsed and periodic forcing functions. The problems were selected to gauge the overall accuracy of the method and to ensure that it properly predicted the jump phenomena associated with non-linear systems.Implementation of the method was found to be straightforward with the simplest iteration procedure for the pseudo force vector sufficing. The results predicted with the method agreed in all important aspects with existing solutions as well as those generated with other methods. As with linear analyses, the modal superposition solution mode was found to be the most efficient; however, exhibiting slightly greater inaccuracies.     

A study on the reliability assessment methodology for pressure piping containing circumferential defects: II: reliability analysis method of a pressure piping system

The reliability of pressure piping containing circumferential defects often needs to be known in engineering. In this paper, the reliability analysis model and the reliability assessment procedure of pressure piping containing circumferential defects are established, and theoretical analysis of the correlation between failure events of the welded joints containing circumferential defects is carried out. Then the numerical method of computing failure probability of pressure piping containing circumferential defects is set up. In the end, an effective method of improving the reliability of pressure piping containing circumferential defects is proposed.     

DF4型机车静液压系统管路振动裂损的原因分析及处理

在机车静液压系统工作状态方面,根据流体力学原理,分析了DF4型机车静液压传动系统产生振动及造成管路裂损的原因。从检修的角度提出了解决管路裂损的措施,以保证系统工作的可靠性。     

Improved ratcheting analysis of piping components

It is well known that ratcheting (defined as the accumulation of deformation with cycles) can reduce fatigue life or cause failure of piping components or systems subjected to seismic or other cyclic loads. This phenomenon is sometime referred to as fatigue-ratcheting, which is yet to be understood clearly. Commercial finite element codes cannot accurately simulate the ratcheting responses recorded in tests on piping components or systems. One of the reasons for this deficiency has been traced to inadequate constitutive models in the existing analysis codes. To overcome this deficiency, an improved cyclic plasticity model, composed of the Armstrong–Frederick kinematic hardening rule and the Drucker–Palgen plastic modulus equation, is incorporated into an ANSYS material model subroutine. The modified ANSYS program is verified against three sets of experimental results. The simulations from this modified ANSYS show a significant improvement over the unmodified ANSYS and the ABAQUS codes.     

A computer model for probabilistic leak-rate analysis of nuclear piping and piping welds

This paper describes the development of a computer code entitled PSQUIRT for probabilistic evaluations of leak rate in nuclear piping. It is based on (1) the Henry-Fauske model of two-phase flow for thermal-hydraulic analysis and (2) an estimation model for elastic-plastic fracture-mechanics analysis. In both analyses, uncertainties arise due to the incomplete knowledge of the crackmorphology variables and statistical scatter of the pipe material properties. The relevant parameters required to conduct these analyses were modeled as random variables. Henceforth, the above thermal-hydraulic and fracture-mechanics models were put in a probabilistic format to allow statistical variability of input and determination of their effects in pipe fracture and leak-before-break (LBB) evaluations. A standard Monte Carlo simulation technique was used to perform the probabilistic analysis. Numerical examples are presented to illustrate the capabilities of the PSQUIRT code. Probabilistic analyses were performed by PSQUIRT for a stainless steel and a carbon steel pipe. Histograms were developed for leakage rate and flaw size in these pipes for LBB applications. The results suggest that the variability of leak rate can be significant due to statistical scatter of crack-morphology parameters. Using these histograms, the subsequent fracture stability of a leaking crack, actural or hypothetical, can be evaluated by either a deterministic or a probabilistic method.     

双向皮带输渣机改三通落渣管的应用分析

详细介绍双向皮带输渣机在使用过程中存在的主要问题,改造三通落渣管的实施情况、经济分析、实际意义,对火电厂实施小技改项目,改善设备性能具有一定的参考价值。     

The effect of the various system stresses on the integrity of a cracked piping system

The paper describes the analysis of a simple model which allows for the effect of the various stresses: weight, thermal, pressure and earthquake, to be incorporated within a stability analysis for a cracked piping system. The instability criterion is derived on the basis of the tearing modulus concept, and it is clearly shown that the instability condition is independent of the various types of loading but depends solely on the interplay between the properties of the cracked section, i.e. the material's crack growth resistance, and the elastic flexibility of the piping system.     

3 MW风力机叶片振动特性分析

为防止叶片发生共振、减少叶片挠度、提高风力机发电效率以及风能利用率,文章建立了3 MW风力机叶片模型,分析了风力机叶片的固有频率。当激励频率为1.26 Hz时,叶片发生共振。以年发电量和风能利用率为目标函数,采用多目标遗传算法对3 MW风力机叶片进行优化设计。优化后的叶片发电功率提高了12%左右,风能利用率提高了18%左右;叶片的固有频率明显提高,挠度减少,解决了风力机叶片共振的问题。     

Generalized differential quadrature analysis of unsteady three‐dimensional MHD radiating dissipative Casson fluid conveying tiny particles

It is worth remarking that little is known about generalized differential quadrature analysis of three‐dimensional flow of non‐Newtonian Casson fluid in the presence of Lorentz force, thermal radiation, haphazard motion of tiny particles, thermomigration of these tiny particles due to temperature gradient, heat source, significant conversion of kinetic energy into internal energy, first‐order chemical reaction, convectively heated horizontal wall, and zero nanoparticles mass flux at the stretching surface. The revised form of Buongiorno's nanofluid model accounted for significant influences of Brownian motion and thermophoresis. The similarity solution was complemented with a powerful collocation procedure based on the generalized differential quadrature method and Newton–Raphson iterative scheme to achieve accuracy and convergent outcomes. The numerical effects disclose that the Casson nanofluid parameter slows down the axial velocities in both directions. Also, the unsteadiness parameter tends to decline generally the temperature throughout the medium and decrease particularly the concentration profile away from the stretching surface. These examinations are applicable in the field of biomechanics, polymer processing, and for characterizing the cement slurries.     

母管制循环水系统优化调度分析

火电厂循环水系统优化调度方案的选择,主要是依据各循环水泵的特性参数、曲线和每台机组凝汽器的循环水量、真空、负荷等,以获得机组最佳运行台数和最佳经济性。本文以母管制循环水系统为例,建立优化运行数学模型,从而得到最佳运行方式及相关各参量。并通过对某电厂2×300MW机组的母管制循环水系统进行计算分析,得出优化调度方案。可以根据各循环水系统的实际情况结合计算机运算的结果进行优化调度,可使火电厂取得明显的经济效益,节能效果明显。     

Modeling and computational fluid dynamic analysis on a non-AC bus coach system

The main objective of this paper is to reduce the drag force and enhance the uniform airflow inside an existing non-air-conditioning bus coach system. The redesigning of an existing bus carried out by considering the forces that reduce the moment of the bus. Modeling and meshing was carried out using solid works and Hypermesh software, respectively. Finally, the problem is simulated using Ansys fluent software and analysis is carried out for different bus models. The noteworthy findings state that the air resistance of the vehicle is found to be 812.74 N and coefficient of drag is 0.67 are less as compared to existing bus model.     

Interference of spherical wave of thermal radiation emitted by a film system

This paper deals with the interference of spherical waves of thermal radiation emitted by a surface film system which consists of a metal substrate and a semi-transparent film. A spectroscopic experiment is made to reconfirm the clear interference in emission spectra of the film system. We present a theoretical model in which an electromagnetic theory for a spherical wave is combined with Planck’s theory of thermal radiation. The mechanism of interference of spherical waves is discussed, and it is suggested that thermal radiation waves emitted by a number of dipoles of the metal might be coherent among each other.     

Optimising a Wells-turbine-type wave energy system

This paper is concerned with the wave power installation located on the Island of Islay, which lies off the western coast of Scotland. A system simulation has been conducted and validated by a comparison between predicted results and measured data. In order both to reduce power ripple content and improve efficiency, an optimisation study has been performed and optimum parameters are suggested. The results demonstrate that an overall optimum for system performance results from a combination of system components which are not individually optimised     

Geo-spatial multi-criteria analysis for wave energy conversion system deployment

The growing requirements for renewable energy production lead to the development of a new series of systems, including wave energy conversion systems. Due to their sensitivity and the impact of the aggressive marine environment, the selection of the most adequate location for these systems is a major and very important task. Several factors, such as technological limitations, environmental conditions, administrative and logistic conditions, have to be taken into account in order to support the decision for best location.This paper describes a geo-spatial multi-criteria analysis methodology, based on geographic information systems technology, for identification of the best location to deploy a wave energy farm. This methodology is not conversion system dependent and therefore can be easily customized for different systems and implementation conditions. Selection factors can include, for example, ocean depth, sea bottom type, existing underwater cables, marine protected areas, ports location, shoreline, power grid location, military exercise areas, climatology of wave significant height, period and power.A case study demonstrating this methodology is presented, for an area offshore the Portuguese southwest coast. The system output allows a clear differential identification of the best spots for implementing a wave energy farm. It is not just a simple Boolean result showing valid and invalid locations, but a layer with a valued suitability for farm deployment.     

Thermodynamic analysis of a novel energy storage system with carbon dioxide as working fluid

Recently, energy storage system (ESS) with carbon dioxide (CO₂) as working fluid has been proposed as a new method to deal with the application restrictions of Compressed Air Energy Storage (CAES) technology, such as dependence on geological formations and low energy storage density. A novel ESS named as Compressed CO₂ Energy Storage (CCES) based on transcritical CO₂ Brayton cycle is presented in this paper. The working principle of CCES system is introduced and thermodynamic model is established to assess the system performance. Parametric analysis is carried out to study the effect of some key parameters on system performance. Results show that the increase of turbine efficiency is more favorable for system optimization and the effect of minimum pressures on system performance is more significant compared with maximum pressures. A simple comparison of CCES system, liquid CO₂ system and Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) system is conducted. It is shown that the system efficiency of CCES is lower than that of AA-CAES system but 4.05% higher than that of liquid CO₂ system, while the energy density of CCES system is 2.8 times the value of AA-CAES system, which makes CCES a novel ESS with potential application.     

Thermodynamic analysis of a novel energy storage system based on compressed CO2 fluid

Because of rapidly growing renewable power capacity, energy storage system is in urgent need to cope with the reliability and stability challenges. CO₂ has already been selected as the working fluid, including thermo‐electrical energy storage or electrothermal energy storage systems and compressed CO₂ energy storage (CCES) systems. In this paper, a CCES system based on Brayton cycle with hot water as the heat storage medium is proposed and analyzed. Thermodynamic model of the system is established for energy and exergy analysis. Sensitivity analysis is then conducted to reveal effects of different parameters on system performances and pursue optimization potential. At a typical transcritical operation condition, round trip efficiency is 60% with energy density of 2.6 kWh/m³. And for the typical supercritical operation condition, the round trip efficiency can reach 71% with energy density of 23 kWh/m³. High round trip efficiency and energy density, which is comparable with those of compressed air energy storage systems, thermo‐electrical energy storage (electrothermal energy storage) systems, and other CCES systems, lead to promising prospect of the proposed system. Copyright © 2017 John Wiley & Sons, Ltd.