抽水蓄能电站相继甩负荷工况导叶-球阀协联关闭规律优化

为提高抽水蓄能电站相继甩负荷工况的动态品质,提出了一种基于多目标算法的导叶-球阀协联关闭策略。首先,建立抽水蓄能电站的精细化仿真模型;然后,确定考虑机组转速和流道水击压力在内的多个优化目标,并基于多目标控制要求引入改进引力搜索算法优化导叶-球阀协联关闭规律,得到一组Pareto最优解;最后,从Pareto最优解中选取综合水击压力目标函数最小值、与平衡点距离最小值及转速目标函数最小值三个典型解进行仿真试验,验证该策略下相继甩负荷工况过渡过程的动态品质。根据优化结果,推荐对发生相继甩负荷工况的两台机组均进行导叶-球阀协联关闭规律优化。结果表明,优化所得最优解均能满足调节保证计算的控制要求,且典型解1比典型解3的蜗壳末端最大压力下降了21.9m,但转速值仅升高了2r/min,这说明提出的导叶-球阀协联关闭策略更好地协调了机组转速与管道水击压力之间的矛盾,可为相继甩负荷工况下电站的安全稳定运行提供有效的技术指导。     

水电站甩负荷大波动过渡过程模拟

本文针对南方某大型水电站,进行水力机组甩负荷大波动过渡过程模拟。在计算软件Matlab的支持下,模拟出了压力变化曲线和转速变化曲线,继而得出引水系统最大压力升高和蜗壳末端最大转速升高。通过电站实测数据与模拟结果之间的对比,验证二者之间的一致性,这种模拟和对比结果也可以为同类型水电站的调节保证计算和稳定性分析提供一定的参考。     

一洞三机式抽水蓄能机组发电工况甩负荷试验分析

为验证某一洞三机式抽水蓄能机组选型设计的安全性及调节保证计算的可靠性,分别进行一洞一机/两机/三机发电工况甩负荷试验。详细介绍了甩负荷试验注意事项、试验方法及测点布置,对甩负荷过程中的转速、水流压力及机组稳定性等试验数据进行分析,发现各种甩负荷工况下的最大转速、蜗壳最大水压及尾水进口真空度等关键指标均满足设计要求,转速上升率、蜗壳进口/末端压力上升率及机组振动摆度等指标均随甩负荷的工况负荷或机组台数的增加而变大。对比过渡过程中关键技术参数的现场实测数据与仿真计算结果可知,两者吻合度较高。研究成果为后续抽水蓄能电站水工布置、机组选型及其过渡过程优化设计提供了参考。     

有调压井水电站甩负荷试验与仿真分析

对于有调压井长引水隧洞水电站,机组甩负荷后,调压井内低频的水位波动决定了机组引水道的压力变化过程,具有一定的特殊性。针对南水水电厂增容改造开展了有调压井水电站甩负荷试验及仿真计算,分析了影响计算与试验结果一致性的主要因素。结果表明,对数学模型及计算参数的修正能使计算结果与试验结果基本吻合,说明目前的数值仿真计算能够反映实际情况,可通过计算分析机组在各工况下的甩负荷过渡过程,优化机组的导叶关闭规律,确保其过渡过程满足调节保证的要求。     

某水电站真机原位试验反演计算及极端工况预测

水电站真机原位试验是机组正式投产前必做试验,试验时进行辅助反演计算可发现试验过程中的问题,计算分析极端工况可为机组永久运行提供重要支撑。针对某水电站甩负荷试验过程中产生的蜗壳最大压力和机组转速上升率超出控制标准的问题进行初步分析及反演计算,发现机组导叶关闭规律与设定的关闭规律有一定差别,且该关闭规律的鲁棒性较差;接着结合试验情况优化机组导叶关闭规律,再对调整后的甩负荷试验进行了同等边界条件下的数值仿真计算,对比分析实测数据及数值计算结果获得特征参数的修正值;最后,通过数值仿真计算预测大波动过渡过程极端工况。研究思路可为类似工程提供参考。     

带侧堰压力前池的非恒定流计算

研究水力过渡过程中压力前池的最高、最低涌波水位,对于确定隧洞或渠顶高程及压力钢管进口高程有重要参照意义。考虑引水渠道末端扩散段及压力钢管对涌波水位的影响,建立了无压引水渠道—压力前池—压力管道非恒定流计算的整体计算模型,计算了电站在增、甩负荷工况下,前池水位的波动过程。结果表明,考虑扩散段和侧堰的影响,计算模型更符合工程实际,可为初步设计提供参考。     

管道末端水击压力计算及误区分析

引水系统的管道参数不同会导致管道末端水击压力波动形态差异较大,在工程仿真计算时得到的管道末端压力变化曲线难以校验。为得到管道末端压力波动曲线,首先结合经典的水击分类图,分析了引用传统水击计算方法时存在的误区。其次,从水击经典理论中的阀门端压力升高方程组出发,推导出各相水击压力升高值的通用形式,得到管道末端水压的简化计算公式,公式表明管道末端阀门开度是影响管道末端水压变化形态的重要因素。最后,利用数值仿真验证所提计算方法的可行性。结果表明,提出的管道末端水压简化计算方法与特征线法得到的压力变化曲线相似度较高,且表现出水压波动形态在管道末端阀门不同初始开度下的变化规律,方法简单实用。     

小水电增效扩容改造过渡过程调节保证建模仿真分析

为掌握水轮机调节特性并优选调节保证措施,基于有压输水系统瞬变流特征线求解法,联合Matlab仿真模型库,构建机组甩负荷过渡过程数字仿真模型,对蜗壳末端压力上升值和机组转速上升率进行数值模拟。仿真结果表明,增设调压阀可有效约束水压和转速上升趋势,改善机组过渡过程调节条件,实现与导叶的协联启闭。建立的非线性数字仿真模型,经学习训练生成能反映机组过渡过程调节特性的瞬变值及波动曲线,可为机组调节保证设计及控制决策提供数据支撑。     

某抽水蓄能电站~#6机组甩负荷试验仿真与实测分析

在某抽水蓄能电站~#6机组甩负荷试验前,用特征线方法对试验过程中的导叶开度、机组转速、蜗壳末端压力及尾水管进口压力等关键技术参数进行仿真预测,并将仿真计算值与试验实测值进行对比,结果表明数值仿真方法与计算模型的准确性较高;以机组在过渡工况中的工作点运行轨迹为基础数据,分析试验机组在甩负荷过程中的运行状态,探究了仿真数据与实测数据出现差别的内在原因,为后续电站出现类似情况的处理提供了参考。     

天荒坪抽水蓄能电站甩负荷过渡过程实测成果仿真分析

介绍了天荒坪抽水蓄能电站一管一机和一管二机现场甩负荷试验实测成果和仿真分析结果,通过对蜗壳进口水压力、机组转速等的现场试验实测曲线与数值仿真计算曲线的比较分析,论证了输水系统及机组各有关参数的可能误差对电站甩负荷过渡过程数值仿真计算结果的影响,同时校正了该电站甩负荷过渡过程计算软件中的有关系数和基本参数,为一管三机甩负荷过渡过程预测和计算分析奠定了基础。     

直喷式柴油机瞬态工况燃烧噪声机理

通过测量瞬态工况与稳态工况燃烧噪声的各种影响参数,研究气体动力载荷及燃烧压力高频振荡对燃烧噪声的影响机理．瞬态工况的壁面温度、喷油压力、针阀升程最大值和针阀开启持续时间均高于同负荷、同转速的稳态工况,导致瞬态工况滞燃期、燃烧始点和喷油量与稳态工况相比产生差异,引起燃烧压力、庄力升高率及高频压力振荡频率和幅值发生变化．结果表明,瞬态工况与同负荷、同转速的稳态工况相比,着火延迟期缩短,但每循环喷油量增大,燃烧噪声增大．     

直喷式柴油机瞬态工况燃烧噪声的试验研究与分析

研究直喷式柴油机瞬态工况对燃烧噪声影响机理。开展内燃机瞬态工况测试技术和测试方法研究,找出瞬态工况下燃烧噪声相对于同转速、同负荷的稳态工况燃烧噪声差异的规律,并从瞬念与稳态工况下燃烧过程的差异对试验结果进行分析。瞬态工况擘面温度、喷油爪力、针阀升程最大值和针阀外启持续时问均高于同负荷同转速的稳态工况,导致瞬态工况滞燃期、燃烧始点和喷油最与稳态工况相比产生差异。结果表明,瞬态工况下动力负荷和压力高频振荡相对于同负荷同转速的稳态工况发生改变是引起燃烧噪声产生差异的根本原因。     

Experimental and simulation analysis of the transient operation of a turbocharged multi-cylinder IDI diesel engine

An experimental and theoretical analysis is carried out to study the response of a multi-cylinder, turbocharged, IDI (indirect injection) compression ignition engine, under transient operating conditions. To this aim, a comprehensive digital computer model is developed which solves the governing differential equations individually for each cylinder, providing thus increased accuracy over previous ‘single-cylinder’ simulations. Special attention has been paid for diversifying the transient operation from the steady-state one, providing improved or even new relations concerning combustion, heat transfer to the cylinder walls, friction, turbocharger and aftercooler operation, and dynamic analysis for the transient case. An extended steady state and transient experimental work is conducted on a specially developed engine test bed configuration, located at the authors' laboratory, which is connected to a high-speed data acquisition and processing system. The steady-state measurements are used for the calibration of the individual submodel constants. The transient investigation includes both speed and load changes operating schedules. During each transient test four major measurements are continuously made, i.e. engine speed, fuel pump rack position, main chamber pressure and turbocharger compressor boost pressure. The hydraulic brake coupled to the engine possesses a high mass moment of inertia and long nonlinear load-change times, which together with the indirect injection nature of the engine are important challenges for the simulation code. Explicit multiple diagrams are given to describe the engine and turbocharger transient behaviour including smoke predictions. The agreement between experimental and predicted responses is satisfactory, for all the cases examined, proving the validity of the simulation process, while providing useful information for the engine response under various transient operations. © 1998 John Wiley & Sons, Ltd.     

含引水和尾水明渠输水的水电站过渡过程分析

鉴于无压明渠的水力特性直接影响含明渠引水式水电站的过渡过程和运行控制,结合有压输水系统的特征线法,采用明渠瞬变流分析的特征隐式格式和相应的边界条件,构建含非自动调节引水明渠、压力前池、尾水池和尾水明渠的引水式水电站的过渡过程分析模型,研究了明渠流水力特性对水电站过渡过程和稳定性的影响。结果表明,在大波动过渡过程中,明渠流水力特性对机组蜗壳进口内水压力和转速极值的影响很小,而尾水渠水力特性及尾水池最低涌波水位决定了尾水管进口的最小内水压力;考虑明渠瞬变流特性的影响,水力干扰下受扰机组的调节品质变化较为明显,而水力-机械系统小波动调节品质变化较小。     

High-speed and heavy-load tribological properties of hydrostatic thrust bearing with double rectangular recess

The rotational speed and load are two main factors affecting the tribological properties of the hydrostatic thrust bearing, especially under high-speed and heavy-load conditions. The three-dimensional simulation models of oil film and bearing friction pairs are established. The oil film pressure field, oil film temperature field, bearing friction pairs deformation field, and oil film thickness field are obtained and discussed under high-speed and heavy-load working conditions. A test rig for studying high-speed and heavy-load tribological properties of hydrostatic thrust bearing with double rectangular recess is developed. The feasibility of the simulation method is validated by experiments. It is found that a reasonable matching relationship between rotational speed and load is obtained, and the burden is the main factor affecting oil film pressure. Still, the rotational speed has a significant impact on the oil film temperature. The influence of friction pairs deformation on tribological properties under high-speed and heavy-load working conditions is explored, the oil film thickness is obtained, and dry friction will appear if the working conditions are further enlarged. This work guides the application of hydrostatic thrust bearing under working conditions of high speed and heavy load.     

Unsteady seepage solutions for hydraulic fracturing around vertical wellbores in hydrocarbon reservoirs

This paper establishes an analytical model to study the influence mechanism of hydraulic fracturing around vertical wellbores under the unsteady seepage in hydrocarbon reservoirs, deduces the analytical solution of water pressure and hydraulic gradient of the model, and compares the law of water pressure and hydraulic gradient changing with time with the results of numerical simulation. The results confirm the accuracy of these analytical solutions. The variation laws of water pressure and hydraulic gradient in the sample under unsteady seepage are analysed by using the COMSOL Multiphysics software. The results show that: the increasing rate and amplitude of water pressure decrease with the distance of water inlet, however, hydraulic gradient near the water inlet is the largest and decreasing with the distance. In order to better understand the mechanism of hydraulic fracturing of rock mass, we studied the influence of permeability and water injection pressure on water pressure and hydraulic gradient of rock mass. The results show that: large permeability coefficient and high hydraulic gradient will increase the probability of rock mass hydraulic fracturing. The permeability and hydraulic gradient of rock mass is important factor in determining whether the rock has hydraulic fracturing. The distribution law of water pressure and hydraulic gradient in rock mass under unsteady seepage provides important reference and basis in hydrogen developing reservoirs.     

中低比转速混流式水轮机空化与水力振动分析

针对中低比转速水轮机空化、振动问题比较突出的现象,以大桥电站水轮机为例,采用分离涡模型(DES)对其进行了三维CFD计算,得到了活动导叶、转轮和尾水管内的压力分布、速度分布及压力脉动特性。结果表明,转轮空化发生在叶片出水边靠近下环的区域,与实际情况相符;机组在高水头、大开度工况下,振动更突出,振动频率为机组旋转频率的整数倍,表明振动主要由转轮造成,而非尾水管涡带引起的。     

竖井旋流泄洪洞出口体型优化研究

为对某竖井旋流泄洪洞出口体型进行优化,提出了一种新型出口形式,通过多组物理模型试验获得了初步的优化设计原则,并结合数值模拟综合验证分析.结果 表明,出口结构前端为竖向环状水跃与横向淹没水跃相连的二级掺混消能区域,湍动能大,消能效果显著,大泄量下总体消能率相对提高10％;后部水流流态转化平顺,低速平稳流出;底板压强分布合...     

直喷式柴油机瞬态工况燃烧噪声二级影响机理研究

研究直喷式柴油机瞬态工况燃烧噪声二级影响机理。设计瞬态与稳态工况燃烧噪声试验,测量燃烧噪声二级影响因素,分析瞬态工况下壁面温度、油管压力和针阀升程等间接因素影响动力负荷与压力高频振荡,从而影响燃烧噪声的二级影响机理,并对不同供油提前角瞬态工况燃烧噪声二级影响机理进行了研究。结果表明,瞬态工况壁面温度、油管压力、针阀升程及针阀开启时间均高于同负荷同转速的稳态工况,影响到瞬态工况滞燃期以及滞燃期的喷油量,进而影响动力负荷和压力高频振荡,使得瞬态与稳态工况燃烧噪声产生差异。