Numerical Prediction of Turbine Profile Loss

1990 ◽  
Author(s):  
L. Xu ◽  
J. D. Denton
Keyword(s):  
Turbine Blades ◽  
Surface Friction ◽  
Trailing Edge ◽  
Integral Boundary ◽  
Wide Range ◽  
Boundary Layer Method ◽  
Time Marching ◽  
Flow Through ◽  
Euler Solver ◽  
Profile Loss

A simple numerical method for predicting the profile loss of turbine blades in subsonic and transonic flows is presented. A time marching Euler solver is used to obtain the main flow through the blade passages, the loss due to the surface friction is calculated using an integral boundary layer method, the total mixed out loss is evaluated from the mass flow and momentum balances between the trailing edge plane and an imaginary downstream plane where the flow is uniform. The base pressure acting on the trailing edge of the blade is calculated directly from the inviscid calculation without empirical correlations. The spurious numerical loss in the Euler calculation is separated from the real loss. The rationality of the approach is justified by the agreement of the prediction with a wide range of experimental measurements.

Numerical Prediction of Profile and Endwall Losses for Multi-Splitter Turbine Cascades

1993 ◽  
Author(s):  
D. M. Zhou ◽  
Z. G. Zhang ◽  
Y. S. Li
Keyword(s):  
Surface Friction ◽  
Turbine Cascade ◽  
Integral Boundary ◽  
Flow Solver ◽  
Secondary Loss ◽  
Boundary Layer Method ◽  
Flow Through ◽  
Turbine Cascades ◽  
Semi Empirical ◽  
Profile Loss

A simple numerical method for predicting the profile loss and the endwall secondary loss of multi-splitter turbine cascade in subsonic flow is presented. A variational finite element potential flow solver is used to obtain the main flow through the blade passages, the loss due to the surface friction is calculated using an integral boundary layer method, the trailing-edge loss is calculated directly from the empirical correlation, and a semi-empirical model for estimating the endwall secondary loss is also provided. The rationality of the approach is justified by the agreement of the prediction with a range of experimental measurement.

The Aerodynamics of Trailing-Edge-Cooled Transonic Turbine Blades: Part 2 — Theoretical and Computational Approach

1997 ◽  
Author(s):  
Mathias Deckers ◽  
John D. Denton
Keyword(s):  
Transonic Flow ◽  
Theoretical Study ◽  
Computational Study ◽  
Control Volume ◽  
Turbine Blades ◽  
Computational Approach ◽  
Trailing Edge ◽  
Time Marching ◽  
Transonic Turbine ◽  
Volume Method

A theoretical and computational study into the aerodynamics of trailing-edge-cooled transonic turbine blades is described in this part of the paper. The theoretical study shows that, for unstaggered blades with coolant ejection, the base pressure and overall loss can be determined exactly by a simple control volume analysis. This theory suggests that a thick, cooled trailing edge with a wide slot can be more efficient than a thin, solid trailing edge. An existing time-marching finite volume method is adapted to calculate the transonic flow with trailing edge coolant ejection on a structured, quasi-orthogonal mesh. Good overall agreement between the present method, inviscid and viscous, and experimental evidence is obtained.

Numerical Study of Cavitation Characteristics of Profiles for Use in Marine Current Turbines

2011 ◽  
Author(s):  
Alexander Ladino
Keyword(s):  
Numerical Study ◽  
Pressure Coefficient ◽  
Turbine Blades ◽  
Design Stage ◽  
Power Performance ◽  
Trailing Edge ◽  
Free Zone ◽  
Wide Range ◽  
Marine Current ◽  
Promising Source

Kinetic energy in the oceans offers an important and promising source of renewable energy which can be exploited by marine current turbines (MCT). One of the key issues related with design of MCT’s is the cavitation inception along turbine blades. Cavitation occurrence in MCT’s blades generates erosion and poor power performance with similar effect in the hydraulic turbine case. In this work, a numerical investigation using the vorticity–stream function code XFOIL in order to study cavitation characteristics in NACA 4 series profiles was performed. The study was developed systematically starting from NACA 4415 profiles and varying independently camber percentage, camber position and thickness. Other study carried out was the effect of trailing edge deflection in the cavitation bucket. Results show a symmetrical increment in cavitation free zone for profiles with increasing thickness. Also for camber increment, the cavitation free zone is incremented, especially at high angles of attack. For variation of camber percentage, increasing camber produces the cavitation bucket moves to high lift zone which suggest that the profile could cavitate at low and negative Cl in wide range of cavitation numbers. Finally the effect of trailing edge deflection produces a slight increment in cavitation free zone which is similar to the effect of camber increment. Also, the trailing edge deflection shows that a same Cl can be achieved with lower angle of attack and lower pressure coefficient compared with the standard profile, constituting a desired behavior from the cavitation point of view. Finally, local dimensionless correlations were developed which can be used for parametric studies of cavitation performance of MCT’s in the design stage.

scholarly journals Computation of Transonic Flows in and About Turbine Cascades With Viscous Effects

1984 ◽  
Author(s):  
U. K. Singh
Keyword(s):  
Inviscid Flow ◽  
Viscous Effects ◽  
Trailing Edge ◽  
Pressure Surface ◽  
Integral Methods ◽  
Interaction Treatment ◽  
Time Marching ◽  
Flow Through ◽  
Turbine Cascades ◽  
Good Agreement

An inviscid-viscous interaction treatment has been developed to predict the flow through transonic axial turbine blade cascades. The treatment includes a trailing-edge base pressure model. This model is based on treating the area between the points of flow separation on the blade surfaces at the trailing-edge and the point of downstream confluence of the suction and pressure surface flows as a region of constant pressure. A time marching technique is used to calculate the inviscid flow and viscous flow is calculated by integral methods for laminar and turbulent boundary layers. Good agreement with experimental data has been obtained.

A Simple Procedure to Compute Losses in Transonic Turbines Cascades

1985 ◽  
Author(s):  
Francesco Martelli ◽  
Alberto Boretti
Keyword(s):  
Transonic Flow ◽  
Simple Procedure ◽  
Turbine Blades ◽  
Wave Interaction ◽  
Integral Boundary ◽  
Shock Wave Interaction ◽  
Time Requirements ◽  
Time Marching ◽  
Shock System ◽  
Marching Method

The prediction of losses in transonic flow in turbines is an important step in the design of turbine stages, but at the same time requirements of simplicity and speed are needed to allow the work of designers. The paper presents a procedure developed to match this goal. It uses classical codes, experimental correlations and simple geometrical models of the shock system. The result of a time marching method with standard mesh is used to run an Integral Boundary layer calculation in which shock wave interaction effects have been included. The shock system is made up of this information plus empirical correlation and a suitable procedure. A mixing calculation is then performed to get the downstream total pressure. The method has been tested with various kinds of turbine blades of which losses and data for calculations have been published. The results are quite good and the procedure appears simple and fast.

scholarly journals Performance Prediction of Subsonic Separated Cascades

1990 ◽  
Author(s):  
N. Yazigi ◽  
M. H. Charlier ◽  
G. A. Gerolymos ◽  
J. Chauvin
Keyword(s):  
Separated Flow ◽  
Inviscid Flow ◽  
Analysis Tool ◽  
Integral Boundary ◽  
Layer Method ◽  
Wide Range ◽  
Boundary Layer Method ◽  
Interaction Approach ◽  
Operating Points ◽  
Good Agreement

During the design process of fans and compressors, rapid computation of performance characteristics at various operating points is essential. In view of estimating off-design performance, the prediction of compressible separated flow is needed. A method has been developed for predicting such flows in 2-D cascades, with varying blade-height, based on an iterative viscous-inviscid interaction approach. Inviscid flow is simulated using a panel method. The effects of compressibility and streamsheet convergence or divergence are taken into account by singularities distributed in the interior of the flowfield. Viscous flow is simulated using an integral boundary-layer method, till the point of separation. Laminar and transitory separation bubbles are modelled semi-empirically. Separated-flow regions are simulated using a free streamline model. The method has been systematically compared with available experimental data and has shown very good agreement concerning the prediction of pressure distribution, deviation angle and loss coefficient, from negative to positive stall and for a wide range of Reynolds number and subsonic Mach number. The method is an interesting performance analysis tool due to its rapidity and reliability.

scholarly journals The Aerodynamics of Trailing-Edge-Cooled Transonic Turbine Blades: Part 1 — Experimental Approach

1997 ◽  
Author(s):  
Mathias Deckers ◽  
John D. Denton
Keyword(s):  
Turbine Blades ◽  
Base Pressure ◽  
Stagnation Temperature ◽  
Trailing Edge ◽  
Static Pressure Distribution ◽  
Discernible Effect ◽  
Two Dimensional Flow ◽  
Shock System ◽  
Flow Through ◽  
Transonic Turbine

The research presented in this part of the paper involved a detailed experimental study of the flow through transonic turbine blading with trailing edge coolant ejection. The tests were carried out on (nearly) flat plate models representing the region of uncovered turning downstream of the throat. The investigation focused on the aerodynamic aspects associated with trailing edge ejection in steady two-dimensional flow over a range of exit Mach numbers, coolant pressure ratios and temperature ratios. The experiments showed that the simple existence of the coolant cavity leads to a substantial change of the flow field in the near wake. Consequently, the slotted unblown base was found to have considerably less loss than the solid one. The effect of coolant ejection is shown to cause a substantial increase in base pressure and reduction in overall loss. The surface static pressure distribution and boundary layers were affected by the coolant in two ways: directly from downstream, via the base pressure, and indirectly through a changed trailing edge shock system. However, the coolant stagnation temperature ratio was found to have no discernible effect on the base pressure and loss.

The Base Pressure and Loss of a Family of Four Turbine Blades

1988 ◽  
Vol 110 (1) ◽  
pp. 9-17 ◽  
Author(s):  
L. Xu ◽  
J. D. Denton
Keyword(s):  
Dominant Role ◽  
Turbine Blades ◽  
Base Pressure ◽  
Trailing Edge ◽  
Edge Geometry ◽  
Trailing Edges ◽  
Loss Prediction ◽  
Turbine Cascades ◽  
Profile Loss ◽  
Made In

Measurements of the effect of trailing edge geometry on the base pressure and loss of a family of four turbine cascades are presented. The measurements were made in the transonic range of Mach number from 0.8 to 1.2. It is found that, for blades with typical trailing edge thickness, the trailing edge loss is the major source of profile loss at these speeds and that the base pressure plays a dominant role in determining the loss. For blades with thick trailing edges an accurate prediction of base pressure is crucial to loss prediction. However, it is found that current methods of base pressure prediction are unable to give reliable predictions.

Performance and Design of Transpiration-Cooled Turbine Blading

1978 ◽  
Author(s):  
F. J. Bayley
Keyword(s):  
Design Method ◽  
Turbine Blades ◽  
Transfer Coefficients ◽  
Integral Boundary ◽  
Heat Transfer Coefficients ◽  
Boundary Layer Method ◽  
Blade Section ◽  
Experimental And Theoretical Studies ◽  
Turbine Blading ◽  
Good Agreement

This paper reports recent experimental and theoretical studies of transpiration-cooled turbine blades, and on the basis of this and earlier work in the total research program proposes a design method for such cooling systems. An integral boundary-layer method of analysis is shown to produce good agreement between observed and predicted heat transfer coefficients over most of the blade section where the effect of the coolant flow is significant, while a simple momentum-mixing theory appears adequate for assessing the effects of the coolant on the blade profile loss.

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