Design and Performance Analysis of Axial Hydro Turbine with Criteria of Tangential Velocity and Constant Diffusion Factor

Priyono Sutikno,Nono Suprayetno,Nathanael P. Tandian,Firman Hartono 한국유체기계학회 2017 International journal of fluid machinery and syste Vol.10 No.4

In reality, the flow condition inside meridional channel may vary from hub to tip, therefore meridional analysis will affect to the blade geometry whether is twisted or tapered. The prediction of maximum surface velocity is not easy, but Lieblein was postulated the alternative form of diffusion factor (DF) on airfoil which can be applied for the cascade analysis. Diffusion factor on cascade is an important design parameter to avoid cavitation in turbomachinery due to the pressure distribution and velocity variation on the surface. The purpose of present study is to know the influence of tangential velocity distribution and constant DF on the blade shape and performance of the axial hydro turbine. There are four criteria of tangential velocity distribution or usually is called as swirl velocity that discussed in this paper, they are mixed vortex, free vortex, forced vortex and constant vortex. Constant DF was applied to the all tangential velocity distribution to obtain pitch chord ratio calculation. This will affect to the pitch chord ratio value and the blade shape of rotor. Performance prediction of axial turbine is performed through Computational Fluid Dynamic (CFD) to validate global parameter design. The result of numerical simulation can be used as basic consideration for manufacturing and experimental testing.

Tip gap flow and aerodynamic loss generation in a turbine cascade equipped with suction-side winglets

서용철,이상우 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.3

The tip gap flow and aerodynamic loss generation over a plane tip equipped with a “constant-width suction-side” (CWSS) winglet and a “varying-width suction-side” (VWSS) winglet have been investigated in a turbine cascade. For a fixed tip gap of h/c = 2.0%, three different winglet widths of w/p = 5.28, 10.55, and 15.83% are tested for the CWSS winglet. The VWSS winglet is designed based on flow visualization and has almost the same winglet area as the CWSS winglet of w/p = 15.83%. In general, the suction-side winglets have a role to increase aerodynamic loss in the tip leakage vortex region but reduce aerodynamic loss in the passage vortex region. For the CWSS winglet, the total-pressure loss coefficient mass-averaged all over the measurement plane has no appreciable changes with increasing w/p from 0.0 to 10.55%, but tends to decrease with further increment of w/p. The VWSS winglet performs better in reducing aerodynamic loss in the passage vortex region than the CWSS winglet of w/p = 15.83% but leads to a little bit higher aerodynamic loss in the tip leakage vortex region. The aerodynamic loss reduction by the VWSS winglet is 7.4% in comparison with the plane tip without winglet, and is about 60% lower than that by the widest CWSS winglet.

익렬유동의 수치해석에서의 복합 정렬-비정렬 격자계의 적용 연구

정향남(H. N. Jung),정희택(H. T. Chung) 한국동력기계공학회 2004 한국동력기계공학회 학술대회 논문집 Vol.- No.-

Numerical simulation has been performed to examine the effects of the computational grids on the prediction of the flow characteristics inside the transonic turbine cascades. Three kinds of computational grids are applied to the high-turning transonic turbine rotor blades and are compared in the sense of stability and accuracy. In addition, the grid adaptation has been tried in order to improve the prediction of the blade performance.

자유유동 난류강도가 터빈 캐스케이드내 3차원 난류유동 특성에 미치는 영향에 관한 전산해석

윤덕규(Deok-Kyu Yoon),이우상(Wu Sang Lee),김대현(Dae Hyun Kim),정진택(Jin Taek Chung) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

The objective of this study is to determine the influence of free-stream turbulent intensity on the three-dimensional turbulent flow in a linear turbine cascade. The range of free-stream turbulence intensity considered is 0.7~10%. This study was performed numerically. The results show that the mass averaged loss coefficient increased according to the increase of free-stream turbulence intensity due to increased value of the mass averaged total pressure loss coefficient which was higher than the decreased value of the mass averaged secondary flow loss coefficient. The loss coefficient distribution was changed suddenly at a free-stream turbulence intensity of 10% while the loss coefficient distribution was rarely changed at a lower free-stream turbulence intensity of 5%.

Design and Performance Analysis of Axial Hydro Turbine with Criteria of Tangential Velocity and Constant Diffusion Factor

Sutikno, Priyono,Suprayetno, Nono,Tandian, Nathanael P.,Hartono, Firman Korean Society for Fluid machinery 2017 International journal of fluid machinery and syste Vol.10 No.4

In reality, the flow condition inside meridional channel may vary from hub to tip, therefore meridional analysis will affect to the blade geometry whether is twisted or tapered. The prediction of maximum surface velocity is not easy, but Lieblein was postulated the alternative form of diffusion factor (DF) on airfoil which can be applied for the cascade analysis. Diffusion factor on cascade is an important design parameter to avoid cavitation in turbomachinery due to the pressure distribution and velocity variation on the surface. The purpose of present study is to know the influence of tangential velocity distribution and constant DF on the blade shape and performance of the axial hydro turbine. There are four criteria of tangential velocity distribution or usually is called as swirl velocity that discussed in this paper, they are mixed vortex, free vortex, forced vortex and constant vortex. Constant DF was applied to the all tangential velocity distribution to obtain pitch chord ratio calculation. This will affect to the pitch chord ratio value and the blade shape of rotor. Performance prediction of axial turbine is performed through Computational Fluid Dynamic (CFD) to validate global parameter design. The result of numerical simulation can be used as basic consideration for manufacturing and experimental testing.

Numerical Optimization for the Cascade of a Transonic Axial Turbine via Genetic Algorithm

Mehrdad Nafar-Sefiddashti,Mahdi Nili-Ahmadabadi,Kyung Chun Kim 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11

This study presents a numerical optimization method for the cascade of an axial turbine. The optimization of a turbine blade is in fact the redesign of the existing blade by coupling a CFD flow solver with an optimization algorithm in order to achieve better performance. Genetic algorithm was used as the optimization algorithm. The CIRCLE method, as a design method with continuous surface curvature distribution, parameterized the geometry of the blades by 33 geometrical parameters. The cost function was to reduce the total pressure loss by considering the constraints on the load factor, blade cross-section, mass flow rate and outlet flow angle. Finally, the genetic algorithm, the geometry parameterization algorithm, computational grid generator and CFD flow solver were automatically coupled to optimize a transonic stator blade row.

Pressure and force on a blade row operated in partial admission with different solidity

조수용,안국영,이영덕,김영철 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.2

Partial admission has advantages over full admission for some operating conditions of turbine. However, additional losses such as expansion, mixing, or pumping are generated in partial admission compared to full admission. Thus, an experiment was conducted in a linear cascade apparatus having a partial admission region in order to investigate the effect of partial admission on a blade row. The admission region was formed by a spouting nozzle installed at the inlet of the linear cascade apparatus. Its cross section was circular, and its diameter was 180 mm. The nozzle was set to have a flow angle of 65°. The tested blade was axial-type, and its chord was 200 mm. The experiment was conducted at a Reynolds number of 3 ´ 105 based on the chord. One blade row of nineteen identical blades was applied to the linear cascade for the partial admission experiment, and this blade row moved along the pitchwise direction in front of the admission region. The operating forces and surface pressures on a blade were measured along the direction at the steady state. For investigating the effect of solidity, three different solidities of 1.25, 1.38, and 1.67 were applied to the blade row. From the experimental results, the maximum rotational force and axial force increased for a larger solidity.

터빈 캐스케이드에서 팁 간극 내 유동장에 대한 큰 팁 간극 효과

손영기,송성진 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.4

이 논문은 터빈 캐스케이드 내에서 큰 팁 간극이 팁 간극 내 유동장에 주는 효과에 관한 연구이다. 액체로켓엔진의 터보펌프와 같은 소형 터보기계는 제조공정 상 공차의 한계로 인해 상대적으로 큰 팁 간극(10%~)을 갖는다. 기존 논문에서는 큰 팁 간극(10%~)에서 오히려 전압손실이 감소됨을 확인하였으나, 이에 관한 자세한 연구가 수행되지 않고 있다. 이러한 큰 팁 간극에서의 전압손실의 변화를 연구하기 위해서는 큰 팁 간극에 의한 팁 간극내의 유동장의 변화에 대한 연구가 필요하다. 이 논문에서는 이효성 연구의 실험 결과와 CFD 시뮬레이션 결과를 토대로 팁 간극내의 유동장의 변화에 대해 알아보았다. 큰 팁 간극에서는 팁 간극에 의한 유동구조와 end-wall 과의 상호작용이 감소됨을 알 수 있었고, 팁 vortex 와 블레이드 흡입면 사이의 상호작용을 감소됨을 알 수 있었다. 또한 큰 팁 간극에서는 end-wall 의 경계층 유동에 의한 vortex 가 소멸되는 것을 알 수 있었고, 팁 간극을 선회 없이 바로 지나가는 유동이 증가함을 알 수 있었다. This paper describes large tip clearance effect on the flow field in the tip gap in a turbine cascade. Small turbomachine like a turbopump in liquid rocket engine has relatively large tip clearance due to the tolerance limits. Even though the trend of the overall loss which decreases for large tip clearance was found by previous studies, the reason of the variation of overall loss has not been studied in detail. To understand the variation of the overall loss, studies about the flow field variation in large tip clearance are needed. This paper investigated the flow field variation based on the Lee's experiment result and CFD simulation. For large tip clearance, the interaction of tip vortex with end-wall and blade suction surface decreases. Also, for large tip clearance, the vortex by end-wall boundary layer flow diminishes and unturned flow increases.

터빈 캐스케이드에서 블레이드 하중에 대한 큰 팁 간극 효과

손영기,송성진 한국항공우주학회 2011 한국항공우주학회 학술발표회 논문집 Vol.2011 No.11

This paper describes large tip clearance effect on blade loading in a turbine cascade. Small turbomachine like a turbopump in liquid rocket engine has relatively large tip clearance due to the tolerance limits. However, only a few studies so far have been conducted on this topic and understanding of large tip clearance effect on turbine blade is lacking. Based on previous Lee(1)'s experiment result, numerical Simulation was conducted and validated. This paper shows that lift coefficient increase for tip clearance smaller than 7.5% of blade chord and then decrease after 7.5% tip clearance. Tip leakage vortex has variation in its strength and position with growing tip clearance and these variations mainly result in the change of lift coefficient. 이 논문은 터빈 캐스케이드 내에서 큰 팁 간극이 블레이드 하중에 주는 효과에 관한 연구이다. 액체로켓엔진의 터보펌프와 같은 소형 터보기계는 제조공정 상 공차의 한계로 인해 상대적으로 큰 팁 간극(10%~)을 갖는다. 그러나 현재 터빈에서의 큰 팁 간극의 효과에 관한 연구가 많이 수행되지 않고 있다. 이 논문에서는 이전 이효성(1) 연구의 실험 결과를 토대로 CFD 계산 및 validaton 을 하였고, 팁 간극이 7.5%보다 작은 경우 전체 블레이드 양력 계수는 팁 간극이 커짐에 따라 증가하다가 7.5% 이후에는 팁 간극이 커짐에 따라 블레이드 양력 계수는 감소하는 경향을 확인하였다. 이러한 경향은 팁 간극의 변화에 따른 팁 와류의 강도 및 위치 변화가 가장 큰 요인으로 확인되었다.

RANS simulation of secondary flows in a low pressure turbine cascade: Influence of inlet boundary layer profile

Michele, Errante,Andrea, Ferrero,Francesco, Larocca Techno-Press 2022 Advances in aircraft and spacecraft science Vol.9 No.5

Secondary flows have a huge impact on losses generation in modern low pressure gas turbines (LPTs). At design point, the interaction of the blade profile with the end-wall boundary layer is responsible for up to 40% of total losses. Therefore, predicting accurately the end-wall flow field in a LPT is extremely important in the industrial design phase. Since the inlet boundary layer profile is one of the factors which most affects the evolution of secondary flows, the first main objective of the present work is to investigate the impact of two different inlet conditions on the end-wall flow field of the T106A, a well known LPT cascade. The first condition, labeled in the paper as C1, is represented by uniform conditions at the inlet plane and the second, C2, by a flow characterized by a defined inlet boundary layer profile. The code used for the simulations is based on the Discontinuous Galerkin (DG) formulation and solves the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the Spalart Allmaras turbulence model. Secondly, this work aims at estimating the influence of viscosity and turbulence on the T106A end-wall flow field. In order to do so, RANS results are compared with those obtained from an inviscid simulation with a prescribed inlet total pressure profile, which mimics a boundary layer. A comparison between C1 and C2 results highlights an influence of secondary flows on the flow field up to a significant distance from the end-wall. In particular, the C2 end-wall flow field appears to be characterized by greater over turning and under turning angles and higher total pressure losses. Furthermore, the C2 simulated flow field shows good agreement with experimental and numerical data available in literature. The C2 and inviscid Euler computed flow fields, although globally comparable, present evident differences. The cascade passage simulated with inviscid flow is mainly dominated by a single large and homogeneous vortex structure, less stretched in the spanwise direction and closer to the end-wall than vortical structures computed by compressible flow simulation. It is reasonable, then, asserting that for the chosen test case a great part of the secondary flows details is strongly dependent on viscous phenomena and turbulence.