Estimating the Loss Associated With Film Cooling for a Turbine Stage

2010 ◽  
Author(s):  
Chia Hui Lim ◽  
Graham Pullan ◽  
John Northall
Keyword(s):  
Film Cooling ◽  
Control Volume ◽  
Flow Direction ◽  
Three Dimensional ◽  
Turbine Stage ◽  
Flow Properties ◽  
Pragmatic Approach ◽  
Turbine Efficiency ◽  
Mainstream Flow ◽  
The Impact

A methodology is presented to allow designers to estimate the penalty for turbine efficiency associated with film cooling. The approach is based on the control volume analysis of Hartsel and the entropy-based formulations of Young and Wilcock. The present work extends these techniques to include flow ejected at compound angles and uses three-dimensional CFD to provide the mainstream flow properties. The method allows the loss contribution from each hole to be identified separately. The proposed method is applied to an aeroengine high-pressure turbine stage. It is found that, if the efficiency definition includes all irreversibilities, the penalty associated with film cooling would be 8.0%. However, if the pragmatic approach is adopted whereby the unavoidable entropy generated due to the equilibration of coolant and mainstream static temperatures is ignored, the efficiency penalty is 0.7%. Finally, a series of case studies is used to quantify the impact of changes to the local mainstream flow direction and coolant ejection angle on the predicted turbine efficiency. It is shown, quantitatively, that reducing the angle between the directions of the coolant and mainstream flows offers the greatest potential for the designer to improve film cooled turbine efficiency.

Estimating the Loss Associated With Film Cooling for a Turbine Stage

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Chia Hui Lim ◽  
Graham Pullan ◽  
John Northall
Keyword(s):  
Film Cooling ◽  
Control Volume ◽  
Flow Direction ◽  
Three Dimensional ◽  
Turbine Stage ◽  
Flow Properties ◽  
Turbine Efficiency ◽  
Mainstream Flow ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

A methodology is presented to allow designers to estimate the penalty for turbine efficiency associated with film cooling. The approach is based on the control volume analysis of Hartsel and the entropy-based formulations of Young and Wilcock. The present work extends these techniques to include flow ejected at compound angles and uses three-dimensional computational fluid dynamics (CFD) to provide the mainstream flow properties. The method allows the loss contribution from each hole to be identified separately. The proposed method is applied to an aeroengine high-pressure turbine stage. It is found that, if the efficiency definition includes all irreversibilities, the penalty associated with film cooling would be 8.0%. However, if the pragmatic approach is adopted whereby the unavoidable entropy generated due to the equilibration of coolant and mainstream static temperatures is ignored, the efficiency penalty is 0.7%. Finally, a series of case studies is used to quantify the impact of changes to the local mainstream flow direction and coolant ejection angle on the predicted turbine efficiency. It is shown, quantitatively, that reducing the angle between the directions of the coolant and mainstream flows offers the greatest potential for the designer to improve film-cooled turbine efficiency.

scholarly journals Design Guidelines for Axial Turbines Operating With Non-Ideal Compressible Flows

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Andrea Giuffre' ◽  
Matteo Pini
Keyword(s):  
Compressible Flows ◽  
Control Volume ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Design Guidelines ◽  
Design Parameters ◽  
Stage Model ◽  
Turbine Stage ◽  
Similarity Equation ◽  
The Impact

Abstract The impact of non-ideal compressible flows on the fluid-dynamic design of axial turbine stages is examined. First, the classical similarity equation (CSE) is revised and extended to account for the effect of flow non-ideality. Then, the influence of the most relevant design parameters is investigated through the application of a dimensionless turbine stage model embedding a first-principles loss model. The results show that compressibility effects induced by the fluid molecular complexity and the stage volumetric flow ratio produce an offset in the efficiency trends and in the optimal stage layout. Furthermore, flow non-ideality can lead to either an increase or a decrease of stage efficiency up to 3–4% relative to turbines designed to operate in dilute gas state. This effect can be predicted at preliminary design phase through the evaluation of the isentropic pressure–volume exponent. Three-dimensional (3D) RANS simulations of selected test cases corroborate the trends predicted with the reduced-order turbine stage model. URANS computations provide equivalent trends, except for case study niMM1, featuring a non-monotonic variation of the generalized isentropic exponent. For such turbine stage, the efficiency is predicted to be higher than the one computed with any steady-state model based on the control volume approach.

Optimization of Trenched Film Cooling Using RSM Coupled CFD

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
V.G. Krishna Anand ◽  
K.M. Parammasivam
Keyword(s):  
Film Cooling ◽  
Three Dimensional ◽  
Response Surfaces ◽  
Test Surface ◽  
Response Factor ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Flow Parameters ◽  
Considerable Impact ◽  
The Impact

AbstractThe trench film cooling employs film holes embedded in a slot created on the surface that requires protection from the impact of hot mainstream flow. The present investigation employs Response Surface Methodology (RSM) approach coupled with CFD analysis to develop a regression predictive model and to optimize the trench geometric and flow parameters viz., trench width (w), trench depth (d), film hole compound angle (β) and blowing ratio (M). The Area-averaged film cooling effectiveness (ȠAA) were chosen as a response factor for RSM and with trench design and flow parameters used as input factors for regression analysis. Analysis of variance (ANOVA) analysis was carried out on the regression model to identify the influence of individual parameters. Three dimensional response surfaces that relate the effect of input parameters on the response factor were analyzed. Experimental results of a case identified from the RSM matrix was found to correlate well with computational investigations. Results from the study indicate that the parameters d, β and M have considerable impact on film cooling performance of test surface with trenches.

scholarly journals An experimental and theoretical investigation of particle–wall impacts in a T-junction

2013 ◽  
Vol 727 ◽  
pp. 236-255 ◽  
Author(s):  
D. Vigolo ◽  
I. M. Griffiths ◽  
S. Radl ◽  
H. A. Stone
Keyword(s):  
Flow Direction ◽  
Three Dimensional ◽  
Stokes Number ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Viscous Boundary Layer ◽  
Particle Tracing ◽  
Two Dimensional Model ◽  
Viscous Boundary ◽  
The Impact

AbstractUnderstanding the behaviour of particles entrained in a fluid flow upon changes in flow direction is crucial in problems where particle inertia is important, such as the erosion process in pipe bends. We present results on the impact of particles in a T-shaped channel in the laminar–turbulent transitional regime. The impacting event for a given system is described in terms of the Reynolds number and the particle Stokes number. Experimental results for the impact are compared with the trajectories predicted by theoretical particle-tracing models for a range of configurations to determine the role of the viscous boundary layer in retarding the particles and reducing the rate of collision with the substrate. In particular, a two-dimensional model based on a stagnation-point flow is used together with three-dimensional numerical simulations. We show how the simple two-dimensional model provides a tractable way of understanding the general collision behaviour, while more advanced three-dimensional simulations can be helpful in understanding the details of the flow.

The Impact of Gas Modeling in the Numerical Analysis of a Multistage Gas Turbine

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Filippo Rubechini ◽  
Michele Marconcini ◽  
Andrea Arnone ◽  
Massimiliano Maritano ◽  
Stefano Cecchi
Keyword(s):  
Gas Turbine ◽  
Flow Direction ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Ratio Distribution ◽  
Real Gas ◽  
Turbine Performance ◽  
Wall Boundary Conditions ◽  
Heavy Duty Gas Turbine ◽  
The Impact

In this work a numerical investigation of a four stage heavy-duty gas turbine is presented. Fully three-dimensional, multistage, Navier-Stokes analyses are carried out to predict the overall turbine performance. Coolant injections, cavity purge flows, and leakage flows are included in the turbine modeling by means of suitable wall boundary conditions. The main objective is the evaluation of the impact of gas modeling on the prediction of the stage and turbine performance parameters. To this end, four different gas models were used: three models are based on the perfect gas assumption with different values of constant cp, and the fourth is a real gas model which accounts for thermodynamic gas properties variations with temperature and mean fuel∕air ratio distribution in the through-flow direction. For the real gas computations, a numerical model is used which is based on the use of gas property tables, and exploits a local fitting of gas data to compute thermodynamic properties. Experimental measurements are available for comparison purposes in terms of static pressure values at the inlet∕outlet of each row and total temperature at the turbine exit.

The Effect of Stator-Rotor Hub Sealing Flow on the Mainstream Aerodynamics of a Turbine

2006 ◽  
Author(s):  
Kevin Reid ◽  
John Denton ◽  
Graham Pullan ◽  
Eric Curtis ◽  
John Longley
Keyword(s):  
Steady State ◽  
Entropy Generation ◽  
Flow Rate ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Flow Conditions ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Mainstream Flow ◽  
Flow Interactions

An investigation into the effect of stator-rotor hub gap sealing flow on turbine performance is presented. Efficiency measurements and rotor exit area traverse data from a low speed research turbine are reported. Tests carried out over a range of sealing flow conditions show that the turbine efficiency decreases with increasing sealant flow rate but that this penalty is reduced by swirling the sealant flow. Results from time-accurate and steady-state simulations using a three-dimensional multi-block RANS solver are presented with particular emphasis paid to the mechanisms of loss production. The contributions toward entropy generation of the mixing of the sealant fluid with the mainstream flow and of the perturbed rotor secondary flows are assessed. The importance of unsteady stator wake/sealant flow interactions is also highlighted.

Modeling Partial Admission in Control Stages of Small Steam Turbines With CFD

2018 ◽  
Author(s):  
Juri Bellucci ◽  
Filippo Rubechini ◽  
Andrea Arnone
Keyword(s):  
Steam Turbine ◽  
Three Dimensional ◽  
Admission Rate ◽  
Point Of View ◽  
Test Case ◽  
Steam Turbines ◽  
Turbine Stage ◽  
Performance Curves ◽  
Partial Admission ◽  
The Impact

This work aims at investigating the impact of partial admission on a steam turbine stage, focusing on the aerodynamic performance and the mechanical behavior. The partialized stage of a small steam turbine was chosen as test case. A block of nozzles was glued in a single “thick nozzle” in order to mimic the effect of a partial admission arc. Numerical analyses in full and in partial admission cases were carried out by means of three-dimensional, viscous, unsteady simulations. Several cases were tested by varying the admission rate, that is the length of the partial arc, and the number of active sectors of the wheel. The goal was to study the effect of partial admission conditions on the stage operation, and, in particular on the shape of stage performance curves as well as on the forces acting on bucket row. First of all, a comparison between the flow field of the full and the partial admission case is presented, in order to point out the main aspects related to the presence of a partial arc. Then, from an aerodynamic point of view, a detailed discussion of the modifications of unsteady rows interaction (potential, shock/wake), and how these ones propagate downstream, is provided. The attention is focused on the phenomena experienced in the filling/emptying region, which represent an important source of aerodynamic losses. The results try to deepen the understanding in the loss mechanisms involved in this type of stage. Finally, some mechanical aspects are addressed, and the effects on bucket loading and on aeromechanical forcing are investigated.

Calculations of Cooled Turbine Efficiency

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
J. H. Horlock ◽  
Leonardo Torbidoni
Keyword(s):  
Film Cooling ◽  
Gas Flow ◽  
Coolant Flow ◽  
The Other ◽  
Turbine Stage ◽  
Isentropic Expansion ◽  
Turbine Efficiency ◽  
Flow Through ◽  
Definition Of ◽  
Industrial Gas Turbine

The efficiency of a cooled turbine stage has been discussed in the literature. All proposed definitions compare the actual power output with an ideal output, which has to be determined; but usually, one of two definitions has been used by turbine designers. In the first, the so-called Hartsel efficiency, the mainstream gas flow, and the various coolant flows to rotor and stator are assumed to expand separately and isentropically to the backpressure. In the second, it is assumed that these flows mix at constant (mainstream) gas pressure before expanding isentropically (sometimes, the rotor coolant flow is ignored in this definition). More recently, it has been suggested that a thermodynamically sounder definition is one in which the gas and coolant flows mix reversibly and adiabatically before isentropic expansion to the backpressure. In the current paper, these three efficiencies are compared, for a typical stage—the first cooled stage of a multistage industrial gas turbine. It is shown that all the efficiencies fall more or less linearly with increase of the fractional (total) coolant flow. It is also shown that the new definition of efficiency gives values considerably lower than the other two efficiencies, which are more widely used at present. Finally, the various irreversibilities associated with the flow through a cooled turbine are calculated. Although all these irreversibilities increase with the fractional coolant flow, it is shown that the “thermal” irreversibility associated with film cooling is higher than the other irreversibilities at large fractional coolant flow.

The Influence of Shroud and Cavity Geometry on Turbine Performance: An Experimental and Computational Study—Part I: Shroud Geometry

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Budimir Rosic ◽  
John D. Denton ◽  
Eric M. Curtis
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Leading Edge ◽  
Leakage Flow ◽  
Cavity Depth ◽  
Industrial Practice ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Mainstream Flow ◽  
Mass Fractions

Imperfections in the turbine annulus geometry, caused by the presence of the shroud and associated cavity, have a significant influence on the aerodynamics of the main passage flow path. In this paper, the datum shroud geometry, representative of steam turbine industrial practice, was systematically varied and numerically tested. The study was carried out using a three-dimensional multiblock solver, which modeled the flow in a 1.5 stage turbine. The following geometry parameters were varied: inlet and exit cavity length, shroud overhang upstream of the rotor leading edge and downstream of the trailing edge, shroud thickness for fixed casing geometry and shroud cavity depth, and shroud cavity depth for the fixed shroud thickness. The aim of this study was to investigate the influence of the above geometric modifications on mainstream aerodynamics and to obtain a map of the possible turbine efficiency changes caused by different shroud geometries. The paper then focuses on the influence of different leakage flow fractions on the mainstream aerodynamics. This work highlighted the main mechanisms through which leakage flow affects the mainstream flow and how the two interact for different geometrical variations and leakage flow mass fractions.

The Influence of Shroud and Cavity Geometry on Turbine Performance — An Experimental and Computational Study: Part I — Shroud Geometry

2007 ◽  
Author(s):  
Budimir Rosic ◽  
John D. Denton ◽  
Eric M. Curtis
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Leading Edge ◽  
Leakage Flow ◽  
Cavity Depth ◽  
Industrial Practice ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Mainstream Flow ◽  
Mass Fractions

Imperfections in the turbine annulus geometry, caused by the presence of the shroud and associated cavity have a significant influence on the aerodynamics of the main passage flow path. In this paper the datum shroud geometry, representative of steam turbine industrial practice, was systematically varied and numerically tested. The study was carried out using a three-dimensional multi-block solver, which modelled the flow in a 1.5 stage turbine. The following geometry parameters were varied: - Inlet and exit cavity length, - Shroud overhang upstream of the rotor leading edge and downstream of the trailing edge, - Shroud thickness for fixed casing geometry and shroud cavity depth, and - Shroud cavity depth for the fixed shroud thickness. The aim of this study was to investigate the influence of the above geometric modifications on mainstream aerodynamics, and to obtain a map of the possible turbine efficiency changes caused by different shroud geometries. The paper then focuses on the influence of different leakage flow fractions on the mainstream aerodynamics. This work highlighted the main mechanisms through which leakage flow affects the mainstream flow and how the two interact for different geometrical variations and leakage flow mass fractions.

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