排汽缸导流内环子午型线改型设计的数值研究

为了降低某汽轮机低压排汽缸的流动损失,对占流动损失比例较高的环形扩压器进行了改型设计,改变扩压器内导流环子午型线圆弧段半径,数值研究其大小变化对排汽缸气动性能的影响。结果表明,扩压器内导流环圆弧段半径增大,提高了汽流在环形扩压器中的增压程度,降低了汽流由扩压器出口进入排汽蜗壳时的压力突升,改善了排汽缸的气动性能。     

汽轮机低压排汽缸气动性能的数值研究

汽轮机低压排汽缸的气动性能对汽轮机组效率的影响至关重要。采用CFD软件CFX,对某型号机组的低压排汽缸小尺寸实验模型在不同来流条件下进行数值模拟研究,并进行了具有对称和非对称两种不同结构扩压器的排汽缸性能对比。结果表明不同的进口旋流对排汽缸性能影响很大,扩压器性能是影响排汽缸性能的主要因素,非对称扩压器更有利于排汽缸性能的提高。     

某新型高效冷凝发电汽轮机排汽缸气动性能研究与结构优化

采用雷诺时均处理的N-S方程和标准k-ε湍流模型,将某新型高效冷凝发电汽轮机低压排汽缸与末级叶栅进行了联合仿真数值模拟研究。计算结果表明:排汽缸中存在以分离涡和通道涡占主导地位的漩涡流,导致气动性能不佳;为了改善扩压能力进而提高其气动性能,采取调整内外导流环扩张角度以及轴向长度等措施对扩压器进行了结构优化,优化后排汽缸出口静压恢复系数从-0.137提升到了0.1617,总压损失系数降低了近18.5%,整机效率提升了近0.5%。     

汽轮机排汽缸的气动研究进展

汽轮机排汽缸是连接凝汽式汽轮机末级出口至冷凝器的通道,改善其气动性能可提高汽轮机的效率。本文从数值分析及试验两方面对排汽缸的研究进行了分析,并对提高气动性能的新型措施进行了归纳。分析表明：末级与排汽缸湿蒸气汽液两相流的联合数值分析是排汽缸流场数值分析的发展方向;模型试验是排汽缸研究的主要方法,由于进口气流对排汽缸性能的影响敏感,进口流场应反映末级出口气流的真实状况,并要特别注意叶栅顶部出口气流的模拟。提高排汽缸气动性能的新型措施为：采用具有负超高的扩压器和非对称扩压器;中分面布置轴向栅格型涡阻尼器;采用除湿措施,减少湿度损失;冷凝器喉部结构及加强系统的改进。     

汽轮机低压末三级耦合排汽缸的气动性能研究

为满足大型核电汽轮机低压排汽系统的开发,采用ANSYS-CFX软件数值求解Reynolds-Averaged Navier-Stokes (RANS)方程和k-ε紊流模型方法研究了低压缸末三级与排汽缸的变工况气动性能.结果表明:变工况显著改变了末级动叶的气动性能,对次次末级、次末级和末级静叶的气动性能几乎没有影响;排汽缸的气动性能受变工况的影响较大,小流量工况下的涡系结构发生较大变化,降低了扩压器静压恢复能力,增加了总压损失和改变了蜗壳内的流场;排汽缸背压减小导致透平级流量的降低和末级动叶出口气流角的变化,进而改变了排汽缸进口的流场特征.研究结果可以为汽轮机排汽缸的设计和优化提供理论支持.     

基于iSight平台的汽轮机低压排汽缸气动优化设计

采用iSight优化设计平台构建了1个汽轮机低压排汽缸全三维粘性气动优化设计系统,该系统耦合了参数化建模、CFD分析与组合优化技术.采用该系统分别对具有轴对称和非轴对称2种不同结构导流环的汽轮机低压排汽缸进行了气动优化设计.优化后与原型设计相比,具有轴对称导流环的排汽缸平均静压恢复系数提高了21.21 %,具有非轴对称导流环的排汽缸平均静压恢复系数提高了45.46%,表明该系统能有效地提高汽轮机低压排汽缸的气动性能.     

汽轮机低压排汽缸内流场的数值模拟研究

利用fluent软件对汽轮机低压排汽缸进行数值模拟,分析排汽缸内部流场特性、涡系分布;利用CFD-POST软件分析排汽缸内部气动性能参数及其分布,并与流场分布进行对比,获知其压力损失来源。研究结果表明:通道涡是造成排汽缸内部能量损失最主要的原因;分离涡分布虽然小于通道涡,但是其最主要的影响是造成扩压管扩压性能的下降;其它涡系结构分布远离主流,影响较小。为排汽缸的优化设计提供基础。     

导流环结构对汽轮机排汽缸气动性能的影响

以某600MW汽轮机为研究对象,应用计算流体力学软件CFX对低压缸末级和排汽缸的耦合模型进行了数值模拟,分析了导流环的起始扩散角、直径以及轴向长度对排汽缸气动性能的影响。结果表明:随着导流环起始扩散角的增加,排汽缸的气动性能得到改善,但当增加到30°时,在扩压器内会产生流动分离,其最佳值为25°;导流环的直径和轴向长度过大或过小均不利于排汽缸的气动性能,其中直径最佳值为5000mm,轴向长度最佳值为900mm。选取3个变量最佳值作为导流环的优化方案,与优化前排汽缸的气动性能进行对比,排汽缸出口的静压恢复系数提高了7.2%,总压损失系数降低了8.4%,气动性能有了明显的改善。     

600MW空冷汽轮机组低压排汽缸流场模拟和结构优化

采用雷诺平均的NS方程和标准的k-ε湍流模型对某空冷汽轮机低压排汽缸进行数值模拟。计算结果显示设计工况下该排汽缸中扩压器出口附近流动发生了分离,导致排汽缸的气动性能不理想。为了改善扩压通道的流场进而提高其气动性能,对扩压器结构进行了优化。优化后的扩压器出口的静压恢复系数比原结构提高了46.5%,总压损失系数分别降低了20.4%。对于排汽缸,其出口的静压恢复系数提高了137.7%,总压损失系数降低了30.6%。由此说明优化后的排汽缸具有较好的气动性能。     

带轴径向扩压器低压排汽缸几何参数的选择

以大量系列试验数据和数值计算为基础,分析了轴径向扩压器及低压排汽缸各种几何参数对排汽缸气动性能的影响,并在此基础上提出了带轴径向扩压器低压排汽缸几何参数选择的范围。     

Influence of various volute designs on volute overall performance

This paper discusses the influence of various volute designs on volute overall performance for a certain centrifu- gal compressor with both vaned and vaneless diffuser. Firstly, based on a free vortex flow pattern and the assumption of a circumferentially uniform flow at the design condition, a corrected method for volute design is adopted. By means of this method, corresponding to five geometric parameters affecting the volute overall performance, ten volute cases are designed. Secondly, the numerical simulation is employed and the detailed flow field and losses in different volutes with different geometric parameters are analyzed. The numerical investigation reveals that in all of the five geometric parameters, the radial location of the cross-section has the strongest influence on the performance of the volute. The non-uniform volute inlet formed by the upward vaned diffuser outlet flow is another important factor. Finally a relatively better value of D1/D2 is concluded.     

入口旋流角对排气扩压段气动性能影响的数值研究

为了研究入口气流旋流角对带支撑结构轴流排气扩压段气动性能的影响,以某型燃气轮机排气扩压段为研究对象,采用数值计算的方法,对单独排气段模型及排气段和涡轮末级动叶耦合模型分别进行数值模拟。采用总压保持系数和静压恢复系数作为衡量排气扩压段气动性能的主要参数。排气段单独模拟的结果显示,当旋流角从0°变化至-32°,总压保持系数下降4%,且在-20°以后开始呈现突然的快速下降趋势;而静压恢复系数先上升后降低,在-16°时达到最大值。另外,通过耦合模型与单独排气段模型的数值计算对比,发现当排气段入口旋流角和质量流量相同时,计算结果较为一致。以上结果说明,入口旋流角是影响排气扩压段流动性能的关键因素之一,进行排气段结构设计时要充分考虑旋流角对内部流动的影响。而且,单独排气段数值模拟在相同质量流量和旋流角度条件下,可近似达到耦合模拟的精度,提高设计效率。     

Three-Dimensional Simulation of Nonstationary Flow Phenomena in "Last Stage-Exhaust Hood"Compartment

INTRODUCTIONThemostheavyloadedelementsofnowpathoflargesteamturbinesarelastcompartmentsoflowpressurecylinders,whichconsistoflaststageandex-hausthood-owingtotechnologicalrestrictionsthiselementsoflastcompartmentshavemaximalreservesofitsefficiency,soitsimprovementisactuallypossi-ble.MostofthepublicationsongasdynamicsoflastcomPartmentcolltainmainlythedataabouttheop-erationofstageandexhausthoodunderuniformin-letandoutletconditionsandtheimportantquestionssuchasarangeofapplicabilityofisolatedmode…     

Numerical investigation of influence of the clocking effect on the unsteady pressure fluctuations and radial forces in the centrifugal pump with vaned diffuser

The relative position between the diffuser vane and the volute tongue (clocking effect) has a great effect on the performance of the single-stage centrifugal pump, which however, is often ignored by designers. In this paper, the influence of clocking effect on the unsteady pressure fluctuation in a centrifugal pump and on the radial force of impeller is investigated. The hydrodynamic performance of the centrifugal pump with vaned diffuser was experimentally measured. Numerical simulation based on the Reynolds-averaged Navier–Stokes (RANS) combined with the SST k-w turbulence model was used to obtain hydrodynamic performance of the centrifugal pump. The numerical results of the hydrodynamic performance were in agreement with the experimental data. The results show that the clocking effect has great influence on the pressure fluctuation and on the unsteady radial force imposed on the impeller. When the diffuser vane approaches the volute tongue, the pressure fluctuation intensity in volute is relatively lower. Meanwhile, relatively larger radial force on the impeller and the lower efficiency are obtained when the diffuser vane is near the volute tongue. Thus, it is suggested that the volute tongue should be located near the middle of two diffuser vanes to obtain better performance.     

Influences of inflow condition on non-axisymmetric flows in turbine exhaust hoods

The complex 3D flow in a steam turbine exhaust hood model with different inlet swirl and inlet total pressure radial distributions has been simulated by employing CFX-5 and analyzed in this paper. It＇s found that the inlet tangential flow angle at hub has a negative effect on the exhaust hood performance, while a negative gradient of inlet total pressure radial distribution has a positive impact on the hood performances. It＇s also numerically con- firmed that a proper distribution of total pressure at hood inlet can successfully eliminate the negative effects caused by the inappropriate inlet swirl distribution and improve the hood aerodynamic performance.     

汽轮机低压排汽缸结构优化设计分析系统及其应用

简要介绍了汽轮机低压排汽缸结构优化设计分析系统的构成和相应的结构优化设计数值试验及分析研究。结果表明该系统能够较快、较省地实现排汽缸的结构设计,得到了较理想的优化设计结果,且为排汽缸的设计研究开辟了一条新的途径,具有良好的工程应用前景。此外,还利用该系统探讨了两种排汽缸导流结构对排汽缸气动性能的改进作用。     

排气蜗壳与轴流涡轮相互作用的气动性能研究进展

排气蜗壳是连接燃气轮机末级涡轮与大气的关键部件,同时也是进一步提高动力装置输出功率最有潜力的部件之一,其与上游末级轴流涡轮因紧密耦合而产生的流动复杂性和非定常性可对涡轮和排气蜗壳的气动性能产生较大影响。国内外研究大多集中于单独的排气蜗壳性能和优化,而对排气蜗壳与轴流涡轮之间耦合的相互作用研究很少。本文主要从排气蜗壳内流动和损失机理、涡轮和排气蜗壳之间流动的相互作用以及排气蜗壳和轴流涡轮耦合的数值研究方法等方面对排气蜗壳内部流场分布及其与轴流涡轮流动相互作用的气动性能研究进展进行综述,重点梳理了二者流动的相互作用以及相关研究方法。最后,对排气蜗壳与轴流涡轮气动性能耦合研究的未来研究重点和发展趋势进行了展望。     

Numerical investigation on influence of diffuser vane height of centrifugal pump

Vaned diffusers are extensively used in centrifugal pumps, but the influence of vane height on internal flow field and overall performance is not explicit. This paper mainly presents numerical investigation on influence mechanism of diffuser vane height in a single-stage centrifugal pump. The head values were carried out on a low specific speed centrifugal pump equipped with different diffuser vane height by numerical simulation and experimental method. And the deviation between numerical results and experimental results were < 5%. The diffuser vane height h/b ratio is changed as 0, 0.3, 0.4, 0.5, 0.6, 0.8, and 1 in this study. The numerical analysis shows that reducing diffuser vane height could eliminate the vortex which appears at tongue region. Meanwhile, the influence of rotor-stator interaction was reduced by reducing the vane height. Consequently, the energy loss in the volute and the diffuser could both be decreased at design flow point and over flow point. In the other hand, the circumferential velocity at partial flow point gets larger which could lead to large frictional loss. In general, reducing the diffuser vane height at design and over flow point could improve the output work of impeller.