Effect of Aerodynamic Blade Change of Two-Stage Axial Subsonic Turbine on Design Point (original) (raw)
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Research Square (Research Square), 2022
For high-aspect-ratio turbine blades, profile loss is dominant and its reduction is important for improving performance. In this paper, a two-stage low-pressure turbine (power turbine) is optimized in two steps: cycle optimization and aerodynamic optimization. In the cycle optimization step, the thermodynamic boundary condition of the turbine is modified. In the second step, which is the main focus of this study, the aerodynamic improvement of a turbine using a two-dimensional optimization technique is performed. The Genetic Algorithm (GA) is used in the optimization process to identify variables that satisfy a defined objective function which is subject to some constraints. The Artificial Neutral Network (ANN) is introduced to correlate variables with the defined objective functions and constraints. Maximum velocity and its location on the blade surface determine transition location and diffusion factor which directly affect total pressure losses. Therefore, in the optimization process, maximum velocity and its location are controlled and defined as objective functions. Profile shape at any given radius is represented with the camber-thickness method. The flow solver used for the aerodynamic analysis of profiles is the cascade analysis code MISES. After improving the performance of vanes and blades' 2D sections, to be confident for performance enhancement of final power turbine ANSYS CFX is used. Finally, the aerodynamic characteristics of the power turbine using optimized geometries are discussed and compared to the original one. The results demonstrate a 1.19 percent improvement in power turbine efficiency at the same pressure ratio.
Aerodynamic design of a gas turbine rotor blade for the KTH test turbine
The purpose of the thesis was to design a new rotor blade for the KTH test turbine according to present design guidelines for gas turbines manufactured at Siemens Industrial Turbomachinery in Finspång. Stage one of a real gas turbine was used as a reference for the aerodynamic design providing a starting point for the project. Using similar gas conditions the new rotor blade was optimized with regard to metal angles and pitch/chord ratio at reference scale. With a satisfying geometry the new blade was scaled back to test turbine size. The blade design could be evaluated and modified using several different in house codes: MAC1, used for meanline design, Beta2 for through flow design, CATO for airfoil design and Multall for 3D design. During the project certain reference specifications restricted the design and had to be considered. ANSYS CFX was used to analyze the final geometry in great detail not possible in any of the other software. The new blade was first analyzed at reference scale and then once again evaluated in Beta2, Multall06 and ANSYS CFX at test turbine scale. As a consequence of generally having low Reynolds number in model tests the results are not entirely comparable with the real case. Effects of transition using different transition models were assessed providing valuable information about the expected differences.
The effect of turbulence intensity and length scale on low-pressure turbine blade aerodynamics
International Journal of Heat and Fluid Flow, 2001
Unpredicted losses have been observed in low-pressure gas turbine stages during high altitude operation. These losses have been attributed to aerodynamic separation on the turbine blade suction surfaces. To gain insight into boundary layer transition and separation for these low Reynolds number conditions, the heat transfer distribution on a Langston turbine blade shape was measured in a linear cascade wind tunnel for turbulence levels of 0.8% and 10% and Reynolds numbers of 40±80k. Turbulence levels of 10% were generated using three passive biplanar lattice grids with square-bar widths of 1.27, 2.54 and 6.03 cm to investigate the eect of turbulence length scale. The heat transfer was measured using a uniform heat¯ux (UHF) liquid crystal technique. As turbulence levels increased, stagnation heat transfer increased and the location of the suction-side boundary layer transition moved upstream toward the blade leading edge. For this turbine blade shape the transition location did not depend on turbulence length scale, the location is more dependent on pressure distribution, Reynolds number and turbulence intensity. For the 10% turbulence cases, the smaller length scales had a larger aect on heat transfer at the stagnation point. A laser tuft method was used to differentiate between boundary layer transition and separation on the suction surface of the blade. Separation was observed for all of the low turbulence (clean tunnel) cases while transition was observed for all of the 10% turbulence cases. Separation and transition locations corresponded to local minimums in heat transfer. Reattachment points did not correspond to local maximums in heat transfer, but instead, the heat transfer coecient continued to rise downstream of the reattachment point. For the clean tunnel cases, streamwise streaks of varying heat transfer were recorded on the concave pressure side of the turbine blade. These streaks are characteristic of either G ortler vortices or a three-dimensional transition process. For the 10% turbulence cases, these streaks were not present. The results presented in this paper show that turbulence length scale, in addition to intensity have an important contribution to turbine blade aerodynamics and are important to CFD modelers who seek to predict boundary layer behavior in support of turbine blade design optimization eorts. Ó
Aerothermal optimization of partially shrouded axial turbines
ETH Ph. D. dissertation, 2007
This work presents the results of an aerodynamic and thermal study of three different shrouded axial turbine configurations. The blade geometry of the turbine stages and the tip clearances of the test cases under investigation are identical although the shroud design is different. The first test case (RRD) is representative of a full shroud geometry while the second (CPS) and third (EPS) test cases adopt different partial shroud arrangements. In the EPS case, a shroud platform is added to cover the blade throat.
International Journal of Engineering Science and Computing, 2019
These paper focuses on how gas turbine engines are optimize generally when their operating conditions changes. Gas Turbine engines are optimize to operate at a nearly fixed speed with fixed blade geometries for its design operating conditions. The flow incidence angle may not be optimize with the blade geometries to reduce off-design performance when the operating conditions of the engine changes. The efficiency of turbo machines are affected by the aerodynamic characteristics of its components, and these have effects on the frequent dynamic operations. These operations include routine start-up, load change and shut downs to cover operation envelope. To optimize the performance of turbo machines, a flow solution has to be determine, the airfoil-shaped bodies must be specified to produce the desired flow field.
The adoption of counter-rotating stages for propellers, axial-flow pumps and low-speed fans has opened a way to design high performance and compact turbomachines in various industrial domains, leading to potentially high savings in energy consumption. Because of the reduction of rotational speed and a better homogenization of the flow downstream of the rear rotor, these machines may have very good aerodynamic performances. However, they are rarely used in subsonic applications, mainly due to poor knowledge of the aerodynamics in the mixing area between the two rotors, where very complex structures are produced by the interaction of highly unsteady flows. The purpose of the present work is to compare the global performances (static pressure rise and static efficiency) and the wall pressure fluctuations downstream of the first rotor for three different stages operating at the same point: a single subsonic axial-flow fan, a conventional rotor-stator stage and a counter-rotating stage that have been designed with in-house tools. The counter-rotating stage allows large savings of energy with respect to the other two systems, for lower rotation rates and by adjusting the distance between the two rotors, a solution with comparable wall pressure fluctuations levels for the three systems is found.
Aerodynamic analysis of 1.5MW horizontal wind turbine blade
Journal of emerging technologies and innovative research, 2019
The paper presents a detailed design andaerodynamic analysis of small power wind turbine blade, including airfoil selection, pitch angle of blade tip.The aerodynamic simulations were performed using a Computational Fluid Dynamics (CFD) method based on the steady-state 1-way FSI (Fluid-Structure Interaction) analysis.The commercially available software FLUENT is employed for calculation of flow field using Navier-Stokes equation in conjunction with the k-omega shear stress transport (SST).The obtained results are verified using numerically calculated data with analytical data.
Rotor Blade Sweep Effect on the Performance of a Small Axial Supersonic Impulse Turbine
International Journal of Aeronautical and Space Sciences, 2015
In this paper, a computational study was conducted in order to investigate the rotor blade sweep effect on the aerodynamics of a small axial supersonic impulse turbine stage. For this purpose, three-dimensional unsteady RANS simulations have been performed with three different rotor blade sweep angles (-15°, 0°, +15°) and the results were compared with each other. Both NTG (No tip gap) and WTG (With tip gap) models were applied to examine the effect on tip leakage flow. As a result of the simulation, the positive sweep model (+15°) showed better performance in relative flow angle, Mach number distribution, entropy rise, and tip leakage mass flow rate compared with no sweep model. With the blade static pressure distribution result, the positive sweep model showed that hub and tip loading was increased and midspan loading was reduced compared with no sweep model while the negative sweep model (-15°) showed the opposite result. The positive sweep model also showed a good aerodynamic performance around the hub region compared with other models. Overall, the positive sweep angle enhanced the turbine efficiency.