The Experts below are selected from a list of 39 Experts worldwide ranked by ideXlab platform

Reinhard Niehuis - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigation of the Diffuser vane clearance effect in a centrifugal compressor stage with adjustable Diffuser geometry part i compressor performance analysis
    Journal of Turbomachinery-transactions of The Asme, 2014
    Co-Authors: Stefan Ubben, Reinhard Niehuis
    Abstract:

    The combination of variable speed control and adjustable Diffuser vanes offers an attractive design option for centrifugal compressors applied in industrial applications where a wide operating range at high efficiency level and a favorable surge line is required. However, the knowledge about the impact on compressor performance of a Diffuser vane clearance between vane and Diffuser wall which is mandatory since the Diffuser geometry adjustment has to take place during operation, is still not satisfying.This two-part paper summarizes results of investigations performed at the Institute of Jet Propulsion and Turbomachinery at RWTH Aachen with an industrial-like centrifugal compressor, featuring a design pressure ratio of 4 and a design speed of 35200 rpm. Particular attention was directed to the influence of the Diffuser clearance on the operating behavior of the entire stage, the pressure recovery in the Diffuser and on the Diffuser flow by a systematic variation of the parameters Diffuser clearance height, Diffuser vane angle, radial gap between impeller exit and Diffuser inlet, and rotor speed.Compressor map measurements provide a summary of the operating behavior related to Diffuser geometry and impeller speed, whereas detailed flow measurements with temperature and pressure probes allow a breakdown of the losses between impeller and Diffuser and contribute to a better understanding of relevant flow phenomena. The results presented in Part I show that an one-sided Diffuser clearance does not necessarily has a negative impact on the operation and loss behavior of the centrifugal compressor, but instead may contribute to an increased pressure ratio and improved efficiency.The flow phenomena responsible for this detected performance behavior are exposed in Part II [28], where the results of detailed measurements with pressure probes at Diffuser exit and Particle Image Velocimetry (PIV) measurements conducted inside the Diffuser Channel, revealing the complex and unsteady flow leaving the impeller and passing the Diffuser Channel, are discussed.The experimental results are published as an open CFD testcase “Radiver 2” [26], extending the experimental data base of the testcase “Radiver” published in 2003 by Ziegler [31].Copyright © 2014 by ASME

  • experimental investigation of the Diffuser vane clearance effect in a centrifugal compressor stage with adjustable Diffuser geometry part ii detailed flow analysis
    Journal of Turbomachinery-transactions of The Asme, 2014
    Co-Authors: Stefan Ubben, Reinhard Niehuis
    Abstract:

    The combination of variable speed control and adjustable Diffuser vanes offers an attractive design option for centrifugal compressors applied in industrial applications where a wide operating range at high efficiency level and a favorable surge line is required. However, the knowledge about the impact on compressor performance of a Diffuser vane clearance between vane and Diffuser wall which is mandatory since the Diffuser geometry adjustment has to take place during operation, is still not satisfying.The results of characteristic line and probe measurements presented in Part I [18] of this two-part paper showed that an one-sided Diffuser clearance not necessarily need to lead to a negative impact on compressor operating behavior but is able to contribute to an increase in flow range, stall margin, pressure ratio and efficiency, as long as the Diffuser passage is broad enough with respect to the clearance height.In order to reveal the relevant flow phenomena, in Part II the results of detailed measurements of the pressure distribution at Diffuser exit and Particle Image Velocimetry (PIV) measurements inside the Diffuser Channel performed at three clearance configurations and three Diffuser angles at a fixed radial gap are discussed. It was found, that for defined Diffuser configurations the clearance flow amplifies the Diffuser throat vortex capable to reduce the loading of the highly loaded vane pressure side and to support a more homogenous Diffuser flow. It turned out that the coaction of the geometry parameter Diffuser vane angle and Diffuser clearance height is of particular importance.The experimental results are published as an open CFD testcase “Radiver 2” [17], extending the experimental data base of the testcase “Radiver” published in 2003 by Ziegler [24].Copyright © 2014 by ASME

Stefan Ubben - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigation of the Diffuser vane clearance effect in a centrifugal compressor stage with adjustable Diffuser geometry part i compressor performance analysis
    Journal of Turbomachinery-transactions of The Asme, 2014
    Co-Authors: Stefan Ubben, Reinhard Niehuis
    Abstract:

    The combination of variable speed control and adjustable Diffuser vanes offers an attractive design option for centrifugal compressors applied in industrial applications where a wide operating range at high efficiency level and a favorable surge line is required. However, the knowledge about the impact on compressor performance of a Diffuser vane clearance between vane and Diffuser wall which is mandatory since the Diffuser geometry adjustment has to take place during operation, is still not satisfying.This two-part paper summarizes results of investigations performed at the Institute of Jet Propulsion and Turbomachinery at RWTH Aachen with an industrial-like centrifugal compressor, featuring a design pressure ratio of 4 and a design speed of 35200 rpm. Particular attention was directed to the influence of the Diffuser clearance on the operating behavior of the entire stage, the pressure recovery in the Diffuser and on the Diffuser flow by a systematic variation of the parameters Diffuser clearance height, Diffuser vane angle, radial gap between impeller exit and Diffuser inlet, and rotor speed.Compressor map measurements provide a summary of the operating behavior related to Diffuser geometry and impeller speed, whereas detailed flow measurements with temperature and pressure probes allow a breakdown of the losses between impeller and Diffuser and contribute to a better understanding of relevant flow phenomena. The results presented in Part I show that an one-sided Diffuser clearance does not necessarily has a negative impact on the operation and loss behavior of the centrifugal compressor, but instead may contribute to an increased pressure ratio and improved efficiency.The flow phenomena responsible for this detected performance behavior are exposed in Part II [28], where the results of detailed measurements with pressure probes at Diffuser exit and Particle Image Velocimetry (PIV) measurements conducted inside the Diffuser Channel, revealing the complex and unsteady flow leaving the impeller and passing the Diffuser Channel, are discussed.The experimental results are published as an open CFD testcase “Radiver 2” [26], extending the experimental data base of the testcase “Radiver” published in 2003 by Ziegler [31].Copyright © 2014 by ASME

  • experimental investigation of the Diffuser vane clearance effect in a centrifugal compressor stage with adjustable Diffuser geometry part ii detailed flow analysis
    Journal of Turbomachinery-transactions of The Asme, 2014
    Co-Authors: Stefan Ubben, Reinhard Niehuis
    Abstract:

    The combination of variable speed control and adjustable Diffuser vanes offers an attractive design option for centrifugal compressors applied in industrial applications where a wide operating range at high efficiency level and a favorable surge line is required. However, the knowledge about the impact on compressor performance of a Diffuser vane clearance between vane and Diffuser wall which is mandatory since the Diffuser geometry adjustment has to take place during operation, is still not satisfying.The results of characteristic line and probe measurements presented in Part I [18] of this two-part paper showed that an one-sided Diffuser clearance not necessarily need to lead to a negative impact on compressor operating behavior but is able to contribute to an increase in flow range, stall margin, pressure ratio and efficiency, as long as the Diffuser passage is broad enough with respect to the clearance height.In order to reveal the relevant flow phenomena, in Part II the results of detailed measurements of the pressure distribution at Diffuser exit and Particle Image Velocimetry (PIV) measurements inside the Diffuser Channel performed at three clearance configurations and three Diffuser angles at a fixed radial gap are discussed. It was found, that for defined Diffuser configurations the clearance flow amplifies the Diffuser throat vortex capable to reduce the loading of the highly loaded vane pressure side and to support a more homogenous Diffuser flow. It turned out that the coaction of the geometry parameter Diffuser vane angle and Diffuser clearance height is of particular importance.The experimental results are published as an open CFD testcase “Radiver 2” [17], extending the experimental data base of the testcase “Radiver” published in 2003 by Ziegler [24].Copyright © 2014 by ASME

S S Dmitriev - One of the best experts on this subject based on the ideXlab platform.

  • analysis of pressure pulsations on the wall in a flat Diffuser Channel in unseparated and separated flow regimes
    High Temperature, 2019
    Co-Authors: S S Dmitriev, S M S O Mokhamed, A V Barbashin
    Abstract:

    The paper presents the results of experimental studies of pressure pulsations on the wall of a flat Diffuser Channel in unseparated and separated flow regimes. The dependences of the root-mean-square values of pressure pulsation amplitudes along the wall and the frequency responses for different flow regimes in the Channel are given. It is shown that the maximum of the pulsation motion near the wall takes place in the beginning of the Diffuser section and corresponds to the preseparation regime. The enhancement of the pulsating motion in the near-wall zone is related to the response of the flow to the pressure gradient, which is determined by the Channel geometry, and is aimed at maintaining the initial unseparated flow in the boundary layer.

  • research of influence of the installation of perforated plates on the flow in the Diffuser ducts with turning of the flow at 90
    Thermal Engineering, 2016
    Co-Authors: S S Dmitriev, I M Borsch, M O Plodistiy, A A Gusev, N A Larin
    Abstract:

    Diffuser Channels with 90° rotation of the flow are used in a number of technical devices to slow down and turn the flow of the working fluid. Besides slowing down and turning of the flow at the outlet of the Channels, it is necessary, as a rule, to possibly provide a uniform field of velocities. However, it is necessary to take into account the requirements for the compactness, which, in some cases, are crucial and lead to the need for nonoptimal Channels in terms of aerodynamics, including wide-angle Diffusers, which are highly likely to cause the flow breakaway with sharply uneven output velocity field. The results of experimental research method of alignment of the velocity field at the output of the wide-angle flat Diffuser Channel with 90° rotation of the flow by installing plates with round and square holes and varying degrees of perforation inside of the Channel are presented in this paper. The studies were carried out on an open-type wind tunnel changing the dimensionless velocity at the inlet of the Diffuser Channel section in the range from 0.18 to 0.72. The values of the coefficients of the total energy loss in a Channel were determined. Which of the installed perforated plates lead to the lowest increase of the energy loss was established. The optimal location of these plates within the duct was determined. The measurements of the velocity fields at the outlet of the Channel were carried out. Simultaneously, the measurements of the pressure pulsations on the side wall at the outlet of the Channel were carried out. It was shown that the minimal increase in energy losses due to the installation of plates can substantially equalize the output of the velocity field and reduce the dynamic loads on the walls. The obtained results allow us to recommend this method of aligning the output of the velocity field for real technical devices that require the simultaneous slowdown in the flow and its rotation.

Солодов, Валерий Григорьевич - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of efficiency of the exhaust compartment of the low-pressure cylinder with a cut Diffuser in the range of regimes
    Национальный технический университет "Харьковский политехнический институт", 2019
    Co-Authors: Солодов, Валерий Григорьевич, Конев, Владимир Афанасьевич
    Abstract:

    Разработана и исследована численная модель варианта выхлопного отсека, включающего межступенчатый канал, отбор пара перед диафрагмой последней ступени, два отсоса пара из межвенцового зазора с камерой влагоудаления, надбандажные протечки, инжекцию пара из камеры влагоудаления в канал диффузора. Представлены результаты численного исследования газодинамических и энергетических характеристик выхлопного отсека цилиндра низкого давления, включающего последнюю ступень с рабочей лопаткой длиной 1100 мм и выхлопной тракт, на частичных режимах. Течение в каждой расчетной подобласти описывается полной системой нестационарных уравнений Навье-Стокса, осредненных по Рейнольдсу-Фавру. Турбулентные эффекты описаны на основе модели SST Ментера в ступени, и модифицированной дифференциальной модели турбулентности Спаларта-Аллмараса в тракте. Интегрирование системы уравнений Навье-Стокса и ассоциированных уравнений осуществляется с помощью авторского программного комплекса MTFS®. Расчетные подобласти аппроксимируются неструктурированными гексагональными сетками. В данных расчетах солвер использует неявную разностную TVDсхему конечных объемов 2-го порядка точности на основе решения задачи Римана на гранях элементарных объемов. Организация вычислений использует вариант алгоритма, основанного на расщеплении вычислительного процесса для многопроцессорных платформ. Модель ступени основана на осреднении потоков массы, импульса и энергии в окружном направлении. Передача параметров от ступени к патрубку и обратно осуществлялась на основе осреднения по массовому расходу. Все расчеты выполнены на основе модели влажного пара, заданного таблицами. Использовано приближение равновесной конденсации. Исследуется работа варианта выхлопного отсека для частичных режимов турбины К-220-44-2М АЭС «Ловииса». Обсуждается эффективность организации выхода избыточного пара из камеры влагоудаления через тангенциальные щели в нижней половине выпуклой оболочки диффузора.Numerical model of exhaust compartment variant, including the interstage Channel, steam extraction in front of the last stage diaphragm, two steam suctions from the interrow gap with a dehumidification chamber, over-leakage, and steam injection from the dehumidification chamber into the Diffuser Channel has been developed and investigated. The results of a numerical study of the gas-dynamic characteristics of the exhaust compartment of low-pressure cylinder, including the last stage with a blade length of 1100 mm and the exhaust path, for partial regimes are presented. The flow in each computational subdomain is described by the complete system of unsteady Navier-Stokes equations averaged over Reynolds-Favre. Turbulent effects are described on the basis of the SST Menter model in the stage, and the modified Spalart-Allmaras differential turbulence model in the path. The integration of the Navier-Stokes system of equations and the associated equations is carried out using an author software package MTFS®. The calculated subdomains are approximated by unstructured hexagonal grids. In these calculations, the solver used an implicit difference TVD scheme of finite volumes of the 2nd order of accuracy based on the solution of the Riemann problem on the faces of the elementary volumes. Organization of calculations used a variant of the algorithm based on splitting the computational process for multiprocessor platforms. The model of stage is based on averaging the mass, momentum and energy fluxes in the circumferential direction in the interstage gap during the passage of the rotor blade along the stator grid step. The transfer of parameters from the stage to the exhaust hood and back was carried out based on mass flow averaging. All calculations are based on the model of wet steam given by the tables. The equilibrium condensation approximation was used. The operation of exhaust compartment variants is considered for the partial regimes of the K-220-44-2M turbine of the Loviisa NPP. The effectiveness of organizing the release of excess steam from the moisture removal chamber through the tangential slots in the lower half of the convex shell of the Diffuser is discussed

  • Investigation of aerodynamic and power characteristics of the exhaust compartment of the low-pressure cylinder "stage-Diffuser"
    НТУ "ХПИ", 2014
    Co-Authors: Швецов, В. Л., Солодов, Валерий Григорьевич, Кожешкурт, И. И., Конев, В. А., Хандримайлов, А. А.
    Abstract:

    Выполнено численное исследование аэродинамических и энергетических характеристик последней ступени ЦНД мощной паровой турбины с предвключенным каналом межступенчатого зазора и входным участком канала диффузора выхлопного патрубка на стационарном режиме с использованием свойств влажного пара на основе односкоростного приближения и равновесной конденсации. Представлена трехмерная структура, осредненные аэродинамические характеристики элементов отсека, энергетические характеристики каналов ступени. Анализируется влияние геометрических элементов – щели отсоса влаги, проволочной демпферной связи и периферийного цельнофрезерованного полочного бандажа на течение в каналах ступени. Обсуждается эффект и параметры струи надбандажной протечки на течение в диффузоре, влияние проволочной демпферной связи на энергетические характеристики ступени. Исследован эффект возможного перетекания пара через технологическую щель в лопатке вблизи проволочной демпферной связи.The numeric investigation of aerodynamic and power characteristics of the last stage of LPC of a powerful steam turbine with the preswitched on Channel of the stage gap and with the input section of the Diffuser Channel of the exhaust branch pipe for the stationary mode was performed using the properties of the wet steam on the basis of one-velocity approximation and the equilibrium condensation. A three-dimensional structure, and averaged aerodynamic characteristics of compartment elements and power characteristics of the stage Channel have been given. The influence produced by geometric elements, in particular moisture suction slots, damper wire tie and peripheral integrally machined rack shroud on the flow in the stage Channels has been analyzed. The effect of the jet of the over-shroud leakage and also jet parameters on the Diffuser flow is discussed including the influence of the damper wire tie on the power characteristics of the stage. The effect of the possible steam flow through the blade slot near the damper wire tie has been studied

Конев, Владимир Афанасьевич - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of efficiency of the exhaust compartment of the low-pressure cylinder with a cut Diffuser in the range of regimes
    Национальный технический университет "Харьковский политехнический институт", 2019
    Co-Authors: Солодов, Валерий Григорьевич, Конев, Владимир Афанасьевич
    Abstract:

    Разработана и исследована численная модель варианта выхлопного отсека, включающего межступенчатый канал, отбор пара перед диафрагмой последней ступени, два отсоса пара из межвенцового зазора с камерой влагоудаления, надбандажные протечки, инжекцию пара из камеры влагоудаления в канал диффузора. Представлены результаты численного исследования газодинамических и энергетических характеристик выхлопного отсека цилиндра низкого давления, включающего последнюю ступень с рабочей лопаткой длиной 1100 мм и выхлопной тракт, на частичных режимах. Течение в каждой расчетной подобласти описывается полной системой нестационарных уравнений Навье-Стокса, осредненных по Рейнольдсу-Фавру. Турбулентные эффекты описаны на основе модели SST Ментера в ступени, и модифицированной дифференциальной модели турбулентности Спаларта-Аллмараса в тракте. Интегрирование системы уравнений Навье-Стокса и ассоциированных уравнений осуществляется с помощью авторского программного комплекса MTFS®. Расчетные подобласти аппроксимируются неструктурированными гексагональными сетками. В данных расчетах солвер использует неявную разностную TVDсхему конечных объемов 2-го порядка точности на основе решения задачи Римана на гранях элементарных объемов. Организация вычислений использует вариант алгоритма, основанного на расщеплении вычислительного процесса для многопроцессорных платформ. Модель ступени основана на осреднении потоков массы, импульса и энергии в окружном направлении. Передача параметров от ступени к патрубку и обратно осуществлялась на основе осреднения по массовому расходу. Все расчеты выполнены на основе модели влажного пара, заданного таблицами. Использовано приближение равновесной конденсации. Исследуется работа варианта выхлопного отсека для частичных режимов турбины К-220-44-2М АЭС «Ловииса». Обсуждается эффективность организации выхода избыточного пара из камеры влагоудаления через тангенциальные щели в нижней половине выпуклой оболочки диффузора.Numerical model of exhaust compartment variant, including the interstage Channel, steam extraction in front of the last stage diaphragm, two steam suctions from the interrow gap with a dehumidification chamber, over-leakage, and steam injection from the dehumidification chamber into the Diffuser Channel has been developed and investigated. The results of a numerical study of the gas-dynamic characteristics of the exhaust compartment of low-pressure cylinder, including the last stage with a blade length of 1100 mm and the exhaust path, for partial regimes are presented. The flow in each computational subdomain is described by the complete system of unsteady Navier-Stokes equations averaged over Reynolds-Favre. Turbulent effects are described on the basis of the SST Menter model in the stage, and the modified Spalart-Allmaras differential turbulence model in the path. The integration of the Navier-Stokes system of equations and the associated equations is carried out using an author software package MTFS®. The calculated subdomains are approximated by unstructured hexagonal grids. In these calculations, the solver used an implicit difference TVD scheme of finite volumes of the 2nd order of accuracy based on the solution of the Riemann problem on the faces of the elementary volumes. Organization of calculations used a variant of the algorithm based on splitting the computational process for multiprocessor platforms. The model of stage is based on averaging the mass, momentum and energy fluxes in the circumferential direction in the interstage gap during the passage of the rotor blade along the stator grid step. The transfer of parameters from the stage to the exhaust hood and back was carried out based on mass flow averaging. All calculations are based on the model of wet steam given by the tables. The equilibrium condensation approximation was used. The operation of exhaust compartment variants is considered for the partial regimes of the K-220-44-2M turbine of the Loviisa NPP. The effectiveness of organizing the release of excess steam from the moisture removal chamber through the tangential slots in the lower half of the convex shell of the Diffuser is discussed