The increasing use of gas turbines in combined cycle power plants together with the high amount of kinetic energy in modem gas turbine exhaust flows focuses attention on the design of gas turbine diffusers as the conn...The increasing use of gas turbines in combined cycle power plants together with the high amount of kinetic energy in modem gas turbine exhaust flows focuses attention on the design of gas turbine diffusers as the connecting part between the Brayton/Joule and the Rankine parts of the combined cycle. A scale model of a typical gas turbine exhaust diffuser is investigated experimentally. The test rig consists of a radial type, variable swirl generator which provides the exhaust flow corresponding to different gas turbine operating conditions. Static pressure measurements are carried out along the outer diffuser walls and along the hub of the annular part and along the centerline of the conical diffuser. Velocity distributions at several axial positions in the annular and conical diffuser have been measured using a Laser Doppler Velocimeter （LDV）. Pressure recovery coefficients and velocity profiles are depicted as a function of diffuser length for several combinations of swirl strength, tip flow and strut geometries. The diffuser without struts achieved a higher pressure recovery than the diffuser with struts at all swirl angle settings. The diffuser with cylindrical struts achieved a higher pressure recovery than the diffuser with profiled struts at all swirl angle seO.ings. Inlet flows with swirl angles over 18° affected the pressure recovery negatively for all strut configurations.展开更多
Highly efficient turbine exhaust diffuser cannot be designed without taking into account the unsteady interactions with the last rotating row of the turbine. Former investigations described in the literature show a ve...Highly efficient turbine exhaust diffuser cannot be designed without taking into account the unsteady interactions with the last rotating row of the turbine. Former investigations described in the literature show a very high potential compared to that of other parts of turbomachines for improving the diffuser. A scale model of a typical gas turbine exhaust diffuser is investigated experimentally. To investigate the influence of rotating wakes, measurements without a spoke wheel as well as measurements with a variable-speed rotating cylindrical spoke wheel with 2 mm- or 10 mm-spokes simulating turbine rotor wakes were made. Miniaturized 3-hole pneumatic probes as well as a 2D-Laser-Doppler-Velocimeter （LDV） were used to investigate velocity profiles. 122 static pressure tapings were used to measure several axial and circumferential static pressure distributions. Without a spoke-wheel the annular diffuser separates at the shroud for all swirl configurations. For the measurements with the 2 mm spoke wheel, the separating diffuser was unstable while keeping the test rig operating parameters constant. For a non-rotating 10 mm spoke wheel and at rotational speeds less than 1,000 rpm, the annular diffuser separated at the shroud. Increasing the rotational speed of the 10mm spoke wheel, flow did not separate at the shroud and much higher pressure recovery than without spoke wheel has achieved.展开更多
The design of turbine exhaust diffusers is still commonly based upon conservative design charts which do not consider the influence of the components installed upstream such as the last turbine stage.Based on investig...The design of turbine exhaust diffusers is still commonly based upon conservative design charts which do not consider the influence of the components installed upstream such as the last turbine stage.Based on investigations with different spoke wheels which approximate the blade wakes of the last turbine stage,the influence of a rotating bladed disc on the flow in a exhaust diffuser is presented.The pressure recovery for an annual diffuser with 15° half cone angle and the 5 mm spoke wheel used in the model test is very high and nearly independent on the rotational speed and the corresponding Strouhal number.For a 20° annual diffuser,the pressure recovery increases with Strouhal number展开更多
Theflow kinetic-energy conversion into the pressure-forcesfield in the outlet turbine diffuser increases the heat drop to the last stage,generating additional power.The recovery properties of the diffuser are determin...Theflow kinetic-energy conversion into the pressure-forcesfield in the outlet turbine diffuser increases the heat drop to the last stage,generating additional power.The recovery properties of the diffuser are determined predominantly by the inlet boundary conditions of theflow formed by the last turbine stage.This study aims to demonstrate the influence of the last turbine stage swirl law on the boundary conditions formation at the diffuser inlet.The aerodynamics of the“turbine stageeexhaust diffuser”system(“SeD”system)was studied by an experi-mental method.The experimental results validated the numerical model of theflow in the“SeD”system.The stage's integral characteristics,the diffuser,and the“SeD”system were obtained for three system geometry variants.The results of the experiments revealed the indisputable advantage of the“negative”swirl law of the last turbine stage.An analysis of theflow structure based on the numerical simulation results revealed the details of the advantages of the boundary conditions at the diffuser inlet formed by the stage with a“negative”swirl compared with the stage with the traditional swirl law.Based on the results,recommendations for the“SeD”system design of powerful stationary gas turbines are proposed.展开更多
In gas turbines,there are strong flow interactions between the last stage turbine and the exhaust diffuser which have a significant influence on the aerodynamic performance of the turbine and diffuser.The supporting s...In gas turbines,there are strong flow interactions between the last stage turbine and the exhaust diffuser which have a significant influence on the aerodynamic performance of the turbine and diffuser.The supporting strut in the diffuser plays a major role in the coupled flow between the turbine and the diffuser.But the influence mechanism imposed by strut on the coupled flow is not fully understood.In this paper,the effects of the strut on the flow pattern evolution and aerodynamic performance of the coupled system are numerically investigated.A full-scale last stage turbine and exhaust diffuser are included in the calculation domains to obtain the full velocity coupling flow field.Annular diffusers with or without struts were designed and compared under different operational conditions.Qualitative and quantitative coupling relationships between the turbine and the exhaust diffuser in terms of flow and performance were concluded and validated in this paper.Under the different operational conditions,the sum of the static pressure coefficient and the total pressure loss coefficient tends to be a constant which is related to the inflow Mach number,the area ratio,and flow uniformity at inlet and outlet of the diffuser no matter with or without strut.There is an exponential relationship between the efficiency of the turbine and the static pressure recovery coefficient of the diffuser.The struts cause the circumferential non-uniformity flow field in the turbine passages,but impose slight influences on the radial distributions of the averaged flow parameters at the turbine exit.The struts help to suppress the vortices near the diffuser case and induce flow separation under the conditions of strut’s attack angle larger than±20°,which results in the performances of the diffuser and turbine fluctuate within a wider range due to the changes of the operational conditions.展开更多
文摘The increasing use of gas turbines in combined cycle power plants together with the high amount of kinetic energy in modem gas turbine exhaust flows focuses attention on the design of gas turbine diffusers as the connecting part between the Brayton/Joule and the Rankine parts of the combined cycle. A scale model of a typical gas turbine exhaust diffuser is investigated experimentally. The test rig consists of a radial type, variable swirl generator which provides the exhaust flow corresponding to different gas turbine operating conditions. Static pressure measurements are carried out along the outer diffuser walls and along the hub of the annular part and along the centerline of the conical diffuser. Velocity distributions at several axial positions in the annular and conical diffuser have been measured using a Laser Doppler Velocimeter （LDV）. Pressure recovery coefficients and velocity profiles are depicted as a function of diffuser length for several combinations of swirl strength, tip flow and strut geometries. The diffuser without struts achieved a higher pressure recovery than the diffuser with struts at all swirl angle settings. The diffuser with cylindrical struts achieved a higher pressure recovery than the diffuser with profiled struts at all swirl angle seO.ings. Inlet flows with swirl angles over 18° affected the pressure recovery negatively for all strut configurations.
基金German Ministry of Economics and Technology under the AG Turbo's COOREFF-T program
文摘Highly efficient turbine exhaust diffuser cannot be designed without taking into account the unsteady interactions with the last rotating row of the turbine. Former investigations described in the literature show a very high potential compared to that of other parts of turbomachines for improving the diffuser. A scale model of a typical gas turbine exhaust diffuser is investigated experimentally. To investigate the influence of rotating wakes, measurements without a spoke wheel as well as measurements with a variable-speed rotating cylindrical spoke wheel with 2 mm- or 10 mm-spokes simulating turbine rotor wakes were made. Miniaturized 3-hole pneumatic probes as well as a 2D-Laser-Doppler-Velocimeter （LDV） were used to investigate velocity profiles. 122 static pressure tapings were used to measure several axial and circumferential static pressure distributions. Without a spoke-wheel the annular diffuser separates at the shroud for all swirl configurations. For the measurements with the 2 mm spoke wheel, the separating diffuser was unstable while keeping the test rig operating parameters constant. For a non-rotating 10 mm spoke wheel and at rotational speeds less than 1,000 rpm, the annular diffuser separated at the shroud. Increasing the rotational speed of the 10mm spoke wheel, flow did not separate at the shroud and much higher pressure recovery than without spoke wheel has achieved.
基金supported by the Bundesmin-isterium für Wirtschaft und Technologie (BMWi) as per resolution of the German Federal Parliament under grant number 0327717B
文摘The design of turbine exhaust diffusers is still commonly based upon conservative design charts which do not consider the influence of the components installed upstream such as the last turbine stage.Based on investigations with different spoke wheels which approximate the blade wakes of the last turbine stage,the influence of a rotating bladed disc on the flow in a exhaust diffuser is presented.The pressure recovery for an annual diffuser with 15° half cone angle and the 5 mm spoke wheel used in the model test is very high and nearly independent on the rotational speed and the corresponding Strouhal number.For a 20° annual diffuser,the pressure recovery increases with Strouhal number
基金funded by the Ministry of Science and Higher Educ ation of the Rus sian Federation as part of the World-class Research Center program:Advanced Digital Technologies(contract No.075-15-2022-311 dated April 20,2022).
文摘Theflow kinetic-energy conversion into the pressure-forcesfield in the outlet turbine diffuser increases the heat drop to the last stage,generating additional power.The recovery properties of the diffuser are determined predominantly by the inlet boundary conditions of theflow formed by the last turbine stage.This study aims to demonstrate the influence of the last turbine stage swirl law on the boundary conditions formation at the diffuser inlet.The aerodynamics of the“turbine stageeexhaust diffuser”system(“SeD”system)was studied by an experi-mental method.The experimental results validated the numerical model of theflow in the“SeD”system.The stage's integral characteristics,the diffuser,and the“SeD”system were obtained for three system geometry variants.The results of the experiments revealed the indisputable advantage of the“negative”swirl law of the last turbine stage.An analysis of theflow structure based on the numerical simulation results revealed the details of the advantages of the boundary conditions at the diffuser inlet formed by the stage with a“negative”swirl compared with the stage with the traditional swirl law.Based on the results,recommendations for the“SeD”system design of powerful stationary gas turbines are proposed.
基金supported by the National Science and Technology Major Project (J2019-Ⅱ-0017-0038).
文摘In gas turbines,there are strong flow interactions between the last stage turbine and the exhaust diffuser which have a significant influence on the aerodynamic performance of the turbine and diffuser.The supporting strut in the diffuser plays a major role in the coupled flow between the turbine and the diffuser.But the influence mechanism imposed by strut on the coupled flow is not fully understood.In this paper,the effects of the strut on the flow pattern evolution and aerodynamic performance of the coupled system are numerically investigated.A full-scale last stage turbine and exhaust diffuser are included in the calculation domains to obtain the full velocity coupling flow field.Annular diffusers with or without struts were designed and compared under different operational conditions.Qualitative and quantitative coupling relationships between the turbine and the exhaust diffuser in terms of flow and performance were concluded and validated in this paper.Under the different operational conditions,the sum of the static pressure coefficient and the total pressure loss coefficient tends to be a constant which is related to the inflow Mach number,the area ratio,and flow uniformity at inlet and outlet of the diffuser no matter with or without strut.There is an exponential relationship between the efficiency of the turbine and the static pressure recovery coefficient of the diffuser.The struts cause the circumferential non-uniformity flow field in the turbine passages,but impose slight influences on the radial distributions of the averaged flow parameters at the turbine exit.The struts help to suppress the vortices near the diffuser case and induce flow separation under the conditions of strut’s attack angle larger than±20°,which results in the performances of the diffuser and turbine fluctuate within a wider range due to the changes of the operational conditions.
