1 RS,HN TurboPower – HPT Stage efficiency HPT Stage Efficiency Efficiency Improvements of High Pressure Turbine Stages Ranjan Saha (KTH) Hina Noor (KTH)

2 RS,HN TurboPower – HPT Stage efficiency Outline of Presentation Background TurboAero project Work packages (WP1 and WP2) WP1 : Leading Edge Contouring WP2 : Reaction Degree Time Schedule

3 RS,HN TurboPower – HPT Stage efficiency Background (1/3) Courtesy of Siemens Industrial Turbomachinery AB Courtesy of Rolls – Royce (Trent 800)  Any efficiency gain for high- pressure stages?  Considerable amount of cooling flow

4 RS,HN TurboPower – HPT Stage efficiency Background (2/3) Reduction of specific fuel consumption for 1% increased efficiency in each of the components Need for increase in efficiency of HPT Stage Adopted from lecture note of Vogt, D., 2008

5 RS,HN TurboPower – HPT Stage efficiency Background (3/3) Adopted from Denton, 2001 Complex Flow Structure

6 RS,HN TurboPower – HPT Stage efficiency TurboAero Industry Design Toolbox Leading Edge Contouring ( WP1) Reaction degree (WP2) Increased turbine effectiveness

7 RS,HN TurboPower – HPT Stage efficiency Motivation The coherent understanding of leading edge contouring is lacking in open literature Results with bulb and fillet found in open literature are based on only linear cascade and mostly subsonic range It is better to use annular set up than linear set up to get more real engine situation, for instance, radial pressure gradient WP1-Leading Edge Contouring Adopted from Becz et al., 2003

8 RS,HN TurboPower – HPT Stage efficiency Objectives WP1: Leading Edge Contouring Establish physical interpretations of leading edge contouring effect onto the endwall flow (horseshoe vortex and passage vortex) Develop design criteria of leading edge contouring for high pressure turbine vane/blade to decrease secondary flow

9 RS,HN TurboPower – HPT Stage efficiency Overview of Investigations WP1: Leading Edge Contouring Detailed literature study on Leading edge contouring and determine design criteria based on findings in open literature Design optimization study by CFD computations Experimental campaigns of 2-3 different designs with pneumatic probe measurement and oil visualization

10 RS,HN TurboPower – HPT Stage efficiency Bulb and Fillet WP1: Leading Edge Contouring Objective: Increase the intensity of suction side leg of h-s vortex Result: Decrease in passage vortex Adopted from Becz et al., 2003 Objective: Decrease the intensity of suction side leg of h-s vortex Result: Decrease the overall secondary flow BulbFillet

11 RS,HN TurboPower – HPT Stage efficiency Previous studies using Fillet WP1: Leading Edge Contouring InvestigatorGeometriesFillet LengthFillet Height Kubendran, et al., 1988Curves and linear fillets3.7δ, 7.4δ3.7δ Pierce, et al., 1992 Triangular/corner fillet, fence 0.78δ2.33δ Sung, et al., 1988Linear fillet2δ2δ1δ1δ Sauer et al., 2000Bulb on a blade1.7δNo data Kubendran & Harvey, 1985Curves and linear fillets0.14δ, 0.28δ0.14δ

12 RS,HN TurboPower – HPT Stage efficiency Some Fillet Designs WP1: Leading Edge Contouring Adopted from Sauer et al., 2000 Adopted from Zess and Thole., 2002 Adopted from Becz et al., 2003 Adopted from Mahmood and Acharya, 2007

13 RS,HN TurboPower – HPT Stage efficiency Some Results Using Fillet or Bulb WP1: Leading Edge Contouring Sauer et al., 1997: Reduction in secondary loss by 25% Sauer et al., 2000: Reduction in endwall loss by 50% Shih and Lin, 2002: Reduction of heat transfer by more than 10% on the airfoil and by more than 30% on the endwall Becz et al., 2003: Reduction of secondary loss by 15% Mahmood et al., 2007: Reduces secondary flows, vorticity and kinetic energy compared to their base profile

14 RS,HN TurboPower – HPT Stage efficiency Measurement Campaign Matrices WP1: Leading Edge Contouring FilletDescription (Y/S) max (X/Cax) max Sss/CaxSps/Cax Batch 1 (Fillet) Blends into the endwall and blade wall with a linear profile Batch 2 (Fillet) Blends into the endwall and blade wall with a curved profile BulbDescription Batch 3 (Bulb) The leading edge step is sized to be equal to the inlet boundary layer displacement thickness and is blended following cosine curve over a distance of three displacement thickness.

15 RS,HN TurboPower – HPT Stage efficiency Present Status WP1: Leading Edge Contouring Literature report on Flow Field in HPT: Done (by Abhishek Nanjundappa) Literature report on Leading Edge Contouring: Done (on review process) Solid Model: On going CFD on CFX and ICEM: On going Course work

16 RS,HN TurboPower – HPT Stage efficiency WP2-Reaction Degree (R) “R is a measure of acceleration in blade or vane passage” ‘R’ effects: Blade design and hence the velocity triangles Blade number and Blade Spacing Blade platform fit Affects the amount of cooling requirement for Blade Cascade Conventional blade platform R = 0R = 0.5 (Wolfgang, 2008) (Moustapha H et al, 2003)

17 RS,HN TurboPower – HPT Stage efficiency Motivation & Objective WP2: Reaction Degree The Motivating Question: Q: Is there any general method to be used to quantify the effect of the ‘R’ onto the coolant requirements and cooling losses? Objective: R = Function (cooling loss, cooling flows, stage loading(), flow coefficient (), Blade design …. ) Selection criteria for the R value in contrast to the coolant consumption and losses for high pressure industrial gas turbines

18 RS,HN TurboPower – HPT Stage efficiency Overview of Investigations WP2: Reaction Degree 1D design calculations (LUAX-T Tool) A parametric study for varying design parameters such as Stage loading(), Flow coefficient () & Reaction degree (R) Test Matrix Validating the (LUAX-T) Loss Model using the Vane loss measurement data from Test rig experiments Throughflow calculations R=0.30 R=0.35 R=0.40 R=0.45 1.8 1.1 0.75 0.35

19 RS,HN TurboPower – HPT Stage efficiency Efficiency vs. Reaction WP2:Reaction Degree Optimum reaction degree is observed to decreases as the stage loading increases.. Results (1/4) Optimum reaction degree as a function of stage pressure ratio (Moustapha H et al, 2003)

20 RS,HN TurboPower – HPT Stage efficiency Efficiency vs. Design Parameters WP2:Reaction Degree Efficiency increases as the stage loading and flow coefficient reduces.. Results (2/4)

21 RS,HN TurboPower – HPT Stage efficiency Cooling mass flow WP2:Reaction Degree Lower rotor cooling requirements for a choice of low Reaction value.. Results (3/4)

22 RS,HN TurboPower – HPT Stage efficiency Loss Model Validation WP2:Reaction Degree Annular sector cascade test rig at KTH Film cooled vane MEASUREDLUAXT Expansion efficiency 91.85%90.26% Av. Kinetic loss coefficient 8.15±0.4%8.87% Results (4/4)

23 RS,HN TurboPower – HPT Stage efficiency Conclusions (1/2) WP2:Reaction Degree Conclusions obtained from performed parametric study: “Isentropic efficiency” shows good trends Optimal Reaction for higher loading or high pressure ratio is a lower value and vise versa Uncooled turbine shows increase in optimal reaction degree Uncooled turbine shows comparatively higher losses (aspect ratio lower, sec loss more) The current “thermodynamic” efficiency does not provide reasonable results

24 RS,HN TurboPower – HPT Stage efficiency Conclusions (2/2) WP2:Reaction Degree Profile losses more for a low reaction transonic vane More secondary loss if the loading and flow parameter is kept low An optimum choice of flow coefficient and stage loading with low reaction decreases rotor cooling comparatively & hence lower overall losses

25 RS,HN TurboPower – HPT Stage efficiency Present Status & Next Step WP2:Reaction Degree 1D Results interpretation Course work The loss Model validation using the measured data from test rig Abstract submitted to 9th European Turbomachinery Conference Comparing results to SIT in-house loss models Through-flow calculations

26 RS,HN TurboPower – HPT Stage efficiency Time Schedule (1/2) WP1(Leading Edge contouring) & WP2(Reaction degree) Deliverable No Description D 1.1 D 2.1 Literature report Literature report and 1D Calculations report D 1.2 D 2.2 Leading edge contouring (lit. report) ( ) Results from 1D turbine design Calculations (publication+report) D 1.3 D 2.3 Synthesis of design and numerical calculations (report) Results for throughflow calculations and vane inclination technique ( ) D 1.4Synthesis of experimental results with numerical comparisons ( ). ASME Turbo IGTI 2011 (Submitted before ), ASME Turbo IGTI 2012 (Submitted before ) Work Package NoDescription WP1.1 & WP2.1Literature Study, cycle & flow path calculations WP1.2Detailed literature study on Leading edge contouring WP2.21D Design calculations & Loss Model Validation WP1.3Design study (of leading edge contouring) & steady CFD computation of final designs WP2.3Throughflow calculations WP1.4Experimental campaigns of 2-3 different designs

27 RS,HN TurboPower – HPT Stage efficiency Time Schedule (2/2) WP1(Leading Edge contouring) & WP2(Reaction degree) Work package WP 1.1 D1.1 WP 2.1 D2.1 WP 1.2 D1.2 WP 2.2 D2.2 WP 1.3 D1.3 WP2.3 D2.3 WP1.4 D1.4 Delivered To be deliver

28 RS,HN TurboPower – HPT Stage efficiency THANK YOU