Aerodynamic losses for squealer tip with different winglets

2019 ◽  
Vol 33 (2) ◽  
pp. 639-647 ◽  
Author(s):  
Yong Cheol Seo ◽  
Sang Woo Lee
Keyword(s):  
Aerodynamic Losses

scholarly journals The Design of an Improved Endwall Film-Cooling Configuration

1998 ◽  
Author(s):  
S. Friedrichs ◽  
H. P. Hodson ◽  
W. N. Dawes
Keyword(s):  
Secondary Flow ◽  
Film Cooling ◽  
Large Scale ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Aerodynamic Loss ◽  
Cooling Flow ◽  
High Static Pressure ◽  
Endwall Film Cooling ◽  
Aerodynamic Losses

The endwall film-cooling cooling configuration investigated by Friedrichs et al. (1996, 1997) had in principle sufficient cooling flow for the endwall, but in practice, the redistribution of this coolant by secondary flows left large endwall areas uncooled. This paper describes the attempt to improve upon this datum cooling configuration by redistributing the available coolant to provide a better coolant coverage on the endwall surface, whilst keeping the associated aerodynamic losses small. The design of the new, improved cooling configuration was based on the understanding of endwall film-cooling described by Friedrichs et al. (1996, 1997). Computational fluid dynamics were used to predict the basic flow and pressure field without coolant ejection. Using this as a basis, the above described understanding was used to place cooling holes so that they would provide the necessary cooling coverage at minimal aerodynamic penalty. The simple analytical modelling developed in Friedrichs et al. (1997) was then used to check that the coolant consumption and the increase in aerodynamic loss lay within the limits of the design goal. The improved cooling configuration was tested experimentally in a large scale, low speed linear cascade. An analysis of the results shows that the redesign of the cooling configuration has been successful in achieving an improved coolant coverage with lower aerodynamic losses, whilst using the same amount of coolant as in the datum cooling configuration. The improved cooling configuration has reconfirmed conclusions from Friedrichs et al. (1996, 1997); firstly, coolant ejection downstream of the three-dimensional separation lines on the endwall does not change the secondary flow structures; secondly, placement of holes in regions of high static pressure helps reduce the aerodynamic penalties of platform coolant ejection; finally, taking account of secondary flow can improve the design of endwall film-cooling configurations.

3D-CFD-Study of Aerodynamic Losses in Compressor Impellers

2018 ◽  
Vol 11 (3) ◽  
pp. 191-200 ◽  
Author(s):  
Fangming Zhang ◽  
Roland Baar
Keyword(s):  
Aerodynamic Losses

scholarly journals Numerical Prediction of Film Cooling Effectiveness and the Associated Aerodynamic Losses With a Three-Dimensional Calculation Procedure

1990 ◽  
Author(s):  
G. H. Dibelius ◽  
R. Pitt ◽  
B. Wen
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Reverse Flow ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Temperature Pattern ◽  
Main Stream ◽  
Cooling Efficiency ◽  
Film Cooling Effectiveness ◽  
Aerodynamic Losses

Film cooling of turbine blades by injecting air through holes or slots affects the main stream flow. A numerical model has been developed to predict the resulting three-dimensional flow and the temperature pattern under steady flow conditions. An elliptic procedure is used in the near injection area to include reverse flow situations, while in the upstream area as well as far downstream a partial-parabolic procedure is applied. As first step an adiabatic wall has been assumed as boundary condition, since for this case experimental data are readily available for comparison. At elevated momentum blowing rates, zones of reverse flow occur downstream of the injection holes resulting in a decrease of cooling efficiency. A variation of the relevant parameters momentum blowing rate m, injection angle α and ratio of hole spacing to diameter s/d revealed the combination of m ≈ 1, α ≈ 30° and s/d ≈ 2 to be the optimum with respect to the averaged cooling efficiency and to the aerodynamic losses. Cooling is more efficient with slots than with a row of holes not considering the related problems of manufacture and service life. The calculated temperature patterns compare well with the experimental data available.

Axisymmetric Endwall Contouring in a Four-Stage Turbine: Comparison of Experimental and Numerical Results

2002 ◽  
Author(s):  
Dieter E. Bohn ◽  
Norbert Su¨rken ◽  
Qing Yu ◽  
Franz Kreitmeier
Keyword(s):  
Flow Field ◽  
Positive Influence ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Flow Measurements ◽  
Flow Angle ◽  
Numerical Predictions ◽  
Before And After ◽  
Endwall Contouring ◽  
Aerodynamic Losses

Secondary flows and leakage flows lead to complex vortex structures in the 3-D flow field of a turbine blading. Aerodynamic losses are the consequence. Reducing these aerodynamic losses by axisymmetric endwall contouring is the subject of a current experimental and numerical investigation of the flow field in a 4-stage test turbine with repeating stages. Numerical 4-stage simulations for the reconstructed turbine with an axisymmetric off-set arc endwall contour at the casing have been performed and compared to corresponding numerical investigations of the original machine without endwall modifications. The 3-D flow fields have been calculated by application of a steady 3-D Navier-Stokes code. Based on these results the experimental setup is modified to the off-set arc endwall design. The characteristics of the reconstructed machine are measured and compared to the original test rig. Special emphasis is put on the determination of the aerodynamic efficiencies over the four stages. For a detailed assessment of the radial and spanwise flow field properties inside the blading, 5-hole pressure probes are used for steady flow measurements in the narrow axial gaps before and after the 3rd stage. Finally, the measured radial distributions of the flow field properties and the machine characteristics are compared to the corresponding numerical predictions. All results show a significant positive influence of the endwall contouring on the radial distribution of the flow angle, the pressure field and the aerodynamic efficiency.

Loss Audit of a Turbine Stage

2015 ◽  
Author(s):  
Sungho Yoon ◽  
Thomas Vandeputte ◽  
Hiteshkumar Mistry ◽  
Jonathan Ong ◽  
Alexander Stein
Keyword(s):  
Significant Loss ◽  
Turbine Stage ◽  
Trailing Edge ◽  
Aerodynamic Efficiency ◽  
Aerodynamic Loss ◽  
Unsteady Interaction ◽  
Generation Mechanisms ◽  
Endwall Cooling ◽  
Entropy Growth ◽  
Aerodynamic Losses

In order to achieve high aerodynamic efficiency of a turbine stage, it is crucial to identify the source of aerodynamic losses and understand the associated loss generation mechanisms. This helps a turbine designer to maximize the performance of the turbine stage. It is well known that aerodynamic losses include profile, endwall, cooling/mixing loss, leakage, and trailing edge loss components. However, it is not a trivial task to separate one from the others because different loss sources occur concurrently and they interact with each other in a machine. Consequently, designers tend to rely on various empirical correlations to get an approximate estimate of each aerodynamic loss contribution. In this study, a systematic loss audit of an uncooled turbine stage has been undertaken by conducting a series of numerical experiments. By comparing entropy growth across the turbine stage, aerodynamic losses are broken down within the stator, rotor, and inter-bladerow gap. Furthermore, losses across each blade row are broken down into profile, leakage, endwall and trailing edge losses. The effect of unsteady interaction due to the relative motion of the stator and the rotor was also identified. For the examined turbine stage, trailing edge losses of the rotor dominated, contributing to more than a third of the total aerodynamic loss. The profile loss across the stator and the rotor, unsteady loss between the stator and the rotor, and the stator endwall loss were also identified to be significant loss sources for this turbine stage. The design implications of the findings are discussed.

Influence of the Alignment of Two Airfoils in the Losses Generation

2009 ◽  
Vol 15 ◽  
pp. 27-32
Author(s):  
Luis A. Moreno-Pacheco ◽  
G.E. Valle-Meléndez ◽  
Claudia del Carmen Gutiérrez Torres ◽  
J.A. Jiménez-Bernal ◽  
M. Toledo-Velázquez
Keyword(s):  
Numerical Simulation ◽  
Pressure Drop ◽  
Turbulence Model ◽  
Drag Forces ◽  
Naca 0012 ◽  
Aerodynamic Losses

A numerical simulation of a flow passing throw two NACA 0012 airfoils is presented in this paper. Aerodynamics, drag forces, and pressure drop is quantified when both profiles are axially aligned and then when one of them is vertically displaced. NUMECA code and Spalart-Allmaras turbulence model were used for this purpose. The results showed that aerodynamic losses are present in both profiles, meaning that the presence of the back profile plays an important role in the aerodynamic behavior of the frontal profile.

Improved clearance designs to minimize aerodynamic losses in a variable geometry turbine vane cascade

2017 ◽  
Vol 232 (17) ◽  
pp. 3085-3101 ◽  
Author(s):  
Jie Gao ◽  
Ming Wei ◽  
Pengfei Liu ◽  
Guoqiang Yue ◽  
Qun Zheng
Keyword(s):  
Gas Turbines ◽  
Strong Interactions ◽  
Variable Geometry ◽  
Specific Flow ◽  
Pressure Losses ◽  
Variable Geometry Turbine ◽  
Gap Height ◽  
Yaw Angle ◽  
Vane Tip ◽  
Aerodynamic Losses

Variable geometry turbine exists in small mobile gas turbines or some marine gas turbines to enhance the part-load performance. However, there are efficiency penalties associated with the vane partial gap, which is needed for the movement of variable vanes. This paper investigates the vane-end clearance leakage flow for a flat tip, a cavity tip, a winglet tip, a tip with passive injection, and a cavity-winglet tip to assess the possibility of minimizing vane-end clearance losses in a variable geometry turbine cascade. First, calculations were done at the test rig conditions for comparison with measured data, and they were used for validation of computational fluid dynamics model. Then, numerical calculations were done for turbine typical conditions. Specific flow structures of the various clearance designs of variable vanes are described, and then the effects of vane turning, including exit Mach numbers of 0.34, 0.44, and 0.54 as well as turning angles of –6°, 0°, and 6° on total pressure losses and outflow yaw angle for different vane tips are shown. In addition, the sensitivity of aerodynamic losses to vane tip gap height is evaluated. Results show that the strong interactions near the tip endwall region change the near-tip loading distribution significantly. With winglet and cavity-winglet tip designs, the loading distribution becomes very similar to the typical fixed vane, and the total loading is reduced, thus reducing the vane-end losses. Among the different vane tips presented, the cavity-winglet tip achieves the best aerodynamic performance, and the cavity tip has the lowest sensitivity to vane tip gap height. Overall, the cavity-winglet tip is found to be the best choice for variable vanes. The research results can provide useful reference for the vane design in a real high endwall-angle variable geometry turbine.

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