TATEF 2. Turbine Aero-Thermal External Flows 2. Contract No. AST3-CT Final Publishable Report 54 MONTHS. From July 2004 to December 2008

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1 Turbine Aero-Thermal External Flows 2 TATEF 2 RTD-Project 6 th FP, Contract AST3-CT Start Date: 1 st July Duration: 54 months Coordinator: R. OLIVE, SNECMA Tel: +33 (0) remi.olive@snecma.fr Turbine Aero-Thermal External Flows 2 Contract No. AST3-CT Final Publishable Report 54 MONTHS From July 2004 to December 2008 Project Coordinator: SNECMA Project Partners: 1. SNECMA 9. ONERA 2. Rolls-Royce 10. ITP 3. MTU Aero Engines 11. VKI 4. ALSTOM 12. University of Karlsruhe 5. AVIO 13. EPFL 6. Turboméca 14. University of Oxford 7. Rolls-Royce Deutschland 15. University of Florence 8. QinetiQ 16. ACIES Starting Date: 1st July 2004 Duration: 54 months Edited by: Rémi OLIVE (SNECMA) 1st Edition - May 2010 This report has been prepared with the help of the Work Package leaders K. Chana for QinetiQ, G. Paniagua for VKI, A. Schulz for the University of Karlsruhe and F. Martelli for the University of Florence. Disclaimer Contractors, Associated Contractors and Subcontractors participating to this report shall incur no liability whatsoever for any damage or loss that may result from the use or exploitation of Information and/or Rights contained in this report. Consequently, Community and/or third Party using and/or exploiting such Information and/or Rights will hold harmless the Party proprietary of such used Information and/or Rights against any action of any other third Party that may result from such use. FPR_ed0 Page 1 of 11

2 NOMENCLATURE CT3 Isentropic Compression Tube Facility (VKI) D# Deliverable report HDL Hub Disk Leakage HP, IP, LP High Pressure, Intermediate Pressure, Low Pressure Indus. Industrial ILPF Isentropic Light Piston Facility (previous appellation for the facility at QinetiQ) LPV Low Pressure Vane M Mach number (also Ma), blowing ratio M# Milestone MAS Month After Start measmt. measurements MT1 Turbine stage investigated in QinetiQ NGV Nozzle Guide Vane Nu Nusselt number (E)OTDF (Enhanced) Overall Temperature Distortion Factor PSP Pressure Sensitive Paint TATEF Turbine Aero-Thermal External Flows LCT Liquid Crystal Temperature TTF Turbine Test Facility (at QinetiQ) TuHP High Pressure Turbine WP Work Package PARTNER ACRONYMS ALSTOM AVIO EPFL ITP MTU ONERA QinetiQ RR RRD Sn TM U-Flor U-Karl UOXF VKI ACIES EC ALSTOM Ltd AVIO S.p.A. Ecole Polytechnique Fédérale de Lausanne Industria de Turbopropulsores S.A MTU Aero Engines GmbH Office National d Etudes et de Recherches Aérospatiales QinetiQ PLC Rolls-Royce PLC Rolls-Royce Deutschland Ltd & Co.KG SNECMA Turboméca University of Florence University of Karlsruhe University of Oxford Von Karman Institute for Fluid Dynamics ACIES SAS European Commission FAR_ed0 Page 2 of 11

3 The overall objectives of the project was to understand the complex aero-thermal phenomena generated in turbines, to build the associated databases and to facilitate the validation of improved Computational Fluid Dynamics (CFD) methods. Indeed, Aero-engine manufacturers request to gain understanding of the aero-thermal flow physics, to improve modelling capacity, accuracy and robustness, to try and validate new concepts/designs and methods and improve CFD know-how - leakage flows, heat transfer in particular regions - and validate CFD codes - optimised design process for higher efficiency and specific power, lower emissions, failure risk and global costs. Figure 1 - HP turbines in aero-engines The work programme has been sub-divided in four complementary tasks dealing with the most important turbine external aero-thermal aspects: WP1 Inlet temperature distortion and inlet swirl variation effects It aims to measure the aero-thermal efficiency and losses associated to a shroud-less high pressure turbine, with inlet temperature non-uniformity and inlet swirl variation, and to investigate the transmission of these two phenomena through the turbine stage. WP2 Aero-thermal performance of HP turbines and interaction phenomena Its objectives are to quantify the overall performance of the stage in terms of mass flow, power, etc. in the view of determining its efficiency. To investigate the rotor-stator interaction with a strong vane trailing edge shock in order to improve the knowledge on the unsteady aerodynamics and the forcing function. To study the aerodynamic and heat transfer of the rotor platform in presence of coolant and with ejection of flow between the stator and rotor hub platforms. To determine the aero thermal performance of an innovative second stator combining aerodynamic and structural function. WP3 Fundamental film cooling studies It is dedicated to the investigation of the effect of steady and unsteady shock waves on film cooling performance, to the analysis of the flow field inside the film cooling holes for various flow conditions at the hole inlet, to the study of film cooling effectiveness and heat transfer coefficient on a nozzle guide vane (assembled in a linear cascade) and its platforms. FAR_ed0 Page 3 of 11

4 WP4 CFD calculations Performing CFD calculations on the tested configurations and confronting the results to the experimental data aims to improve the simulation techniques. The CFD tools for heat transfer and unsteady computations are assessed, as their usability for the most suited ones. Moreover the comparisons between the results from the different partners (industrial and also research) allow these partners to assess their code competence. The involved project partners form an European platform being able to carry out the work programme. It is constituted by - nearly all the European aircraft/helicopter engine manufacturers: SNECMA, Rolls-Royce (UK & Deutschland), MTU Aero Engines, AVIO, Turbomeca, ITP; - one major gas turbine producer: ALSTOM; - the best available research centres and universities in the turbine domain: QinetiQ, von Karman Institute, ONERA, University of Oxford, University of Karlsruhe, University of Florence, Ecole Polytechnique Fédérale de Lausanne; - a company specialised in the research promotion and the management consulting: ACIES. WP1 The high pressure (HP) turbine stage investigated with inlet temperature distortion and inlet swirl variation effects in this part of the programme was installed and investigated in the frame of two predecessor programmes, IACA and TATEF. While the turbine was designed by R-R the geometry is available to the members of the consortium established in the frame of the two predecessor contracts. The turbine is referred to as the MT1 turbine stage. Figure 2 - QinetiQ Turbine Test Facility The overall aims for this work package were: Measurement of the aero-thermal efficiency and losses associated with a shroud-less high pressure turbine, with inlet temperature non-uniformity and inlet swirl variation. Investigate inlet temperature non-uniformity and inlet swirl effects on the turbine mass-flow and torque. Investigate the transmission of engine realistic non-uniform inlet temperature through a HP turbine stage. FAR_ed0 Page 4 of 11

5 Final Publishable Report Figure 3 - Turbine interactions EOTDF (QQ) Investigate the measurement of engine realistic inlet swirl through a HP turbine stage. Figure 4 - Turbine interactions Swirl (QQ) WP2 In terms of instrumentation significant progress has been obtained regarding fast directional probes, dual thin film sensors, tip clearance probes and pressure sensitive paints. Two new methodologies were developed. First of all high confidence efficiency measurements were obtained for the first time. Additionally a novel technique to determine the heat flux in cooled airfoils has been implemented. FAR_ed0 Page 5 of 11

6 Figure 5 - VKI Compression Tube 3 Regarding the flow analysis, interesting features have been observed regarding the strong shocks, rim seal interactions and HP-IP interactions. At high pressure ratio the analysis of the data indicate that the vane shocks give rise to a vortical structure that is the main cause of the turbine loss. Regarding the rim-seal investigation we observed a rise in efficiency when blowing, contrary to the experience with subsonic turbines. Detailed loss analyses indicate that such increase is associated to a decrease in the shock loss. The multi-splitter IP configuration with equally spaced vanes indicates clear separated regions at off-design conditions. Figure 6 - Stator rim seal (HDL) (VKI) FAR_ed0 Page 6 of 11

7 Figure 7 - Turbine interactions LP Strut vane (VKI) WP3 Film cooling is the state-of-the-art method to cool in efficient way high thermally loaded turbine vanes and blades. The cooling air, taken from the compressor, is being bypassed to the turbine. As this air does not contribute to the thermodynamic cycle it has to be considered as a loss. Considering that up to 20% of the total engine core mass flow is used for cooling, the reduction of coolant mass-flow is one of the main potentials to further increase the overall efficiency of the engine and hence to decrease the specific CO 2 -emissions. Consequently, numerous studies have been performed in the past to obtain a deeper insight into the aero-thermal behaviour of cooling films. In TATEF1 several basic film cooling issues could be addressed performing generic experiments which allowed to separate main influencing effects such as coolant cross flow, free stream turbulence, wake passing or row interaction. The outcome of these studies helped to better understand film cooling physics. Nevertheless, major unknowns still remained. WP3 of persued the course of TATEF1: Separating and analysing effects that were of actual concern of the industrial partners. Increasing turbine-stage loads for examples leading to supersonic free stream conditions raised new questions regarding the impact of shock waves on film cooling performance. This issue was addressed in subtask 3.1 Film cooling in transonic flows. With the request for powerful optical measuring techniques, a unique design of a generic experimental set-up was developed, allowing for simulating transonic suction-side Mach-number distributions at realistic shock strengths, Reynolds-numbers, and coolant to free stream density ratios. For the first time, the shock film cooling interaction zone could be analysed with great thermal as well as local resolution owing to infrared thermography. Facing challenges in applying this measurement technique to the present high temperature gradient flows, new calibration techniques have been developed. The major outcome of the study is that cooling films are quite insensitive to shock waves within the range of Mach numbers and shock strengths usually present in modern transonic turbines. However, the discharge behaviour of cooling holes changes in transonic free streams. Hence, a correlation on discharge coefficient was developed covering a wide range of operating conditions. With the knowledge gained from subtask 3.1 the amount of cooling air can be further decreased for the next generation of aero-engines, since the factor of safety formerly necessary for the unknown shock influence can be reduced. FAR_ed0 Page 7 of 11

8 Figure 8 - Fundamental film-cooling studies (U-Karl) A possibility to further increase total cooling efficiency is to combine technologies such as internal convective cooling and film cooling. To promote the internal convective heat flux obstacles like ribs are positioned at the inner surface. These obstacles cause enhanced turbulent mixing and lead at the same time to an increased heat transferring surface. However, the effect of complex flow structures generated by the internal obstacles on the hole discharge behaviour and film cooling performance cannot be satisfactorily predicted with available design tools. Hence the major goal of subtask 3.2 is to develop correlations of discharge coefficients taking into account these effects. Comprehensive aerodynamic as well as thermal measurements have been performed providing a database allowing for the evaluation of the aero-thermal performance of a cooling film under the influence of internal geometries. Furthermore the aerodynamic tests performed at the hole entry and exit region as well as pressure measurements inside a film cooling hole help to validate CFD methods and to better understand the flow physics. Figure 9 - Fundamental film-cooling studies (U-Karl) The application of film cooling on the hub and casing walls (platforms) is becoming more and more attractive due to the increased demand for power and efficiency of gas turbines and aero engines. There is a considerable complexity in applying film cooling in these regions due to the 3D flow features present in the gas flow. The main objective of subtask 3.3 is to measure and analyse the film cooling performance on platforms. This has been done with emphasis on engine- FAR_ed0 Page 8 of 11

9 realistic advanced cooling configurations composed of multiple rows of cylindrical and shaped holes as well as slot leakage injection. A comprehensive database of film cooling performance data obtained on airfoils and platforms of a heavily film cooled nozzle guide vane has been delivered. The experimental and computational results of the test cases allow the industrial partners to for example strengthen film cooling protection schemes without increasing the cooling air consumption. Moreover, the work package has enabled the establishment of expertise, skills and knowledge in the field of turbine cooling technologies. It turned out to be more challenging to measure heat transfer on the platforms with the existing technique than anticipated. An improved thermal measurement procedure has been established and validated. Successful validation and application of pressure sensitive paint for film cooling measurements has been carried out. Figure 10 - Fundamental film-cooling studies (EPFL) WP4 The Work Package 4 is mainly driven to the numerical simulation of heat transfer and unsteady stage aerodynamics in the test cases selected by Industrial Partners. The main targets of this Work package can be summarized as follows: Validate numerical methods and assess their accuracy through a wide comparison with experimental data, and improve modelling capacity; Gain understanding in the complex time-averaged and time resolved flow field behaviour both in aerodynamics a as well in heat transfer; Improve the understanding of aero-thermal flow physics with special attention to film cooled configuration; Develop and improve physical and numerical modelling of the HP turbine stage physics and provide suggestion and guidelines for improving the utilization and practice of Industrial and commercial codes through an intelligent comparison with experiment and research codes Two tasks of this WP are devoted to the physical model improvement of heat transfer and unsteady stage simulation. Another task is devoted to the production calculations by Industrial partners with their in house codes or commercial ones; The last one is devoted to the comparison of such calculation among them, with the experiments and Research code calculations and to achieve guideline and practice to better the use of the Numerical tools. FAR_ed0 Page 9 of 11

10 The Assessment of CFD tools for heat transfer of turbine stage components has been achieved through the improvements of physical model on the basis of CFD simulation of selected cases focused on the basic of Film Cooling (WP3.1). The physical model improvement for HT calculations have been completed and a transition model for the boundary layer has been successfully added to the two equation turbulence models already present in the HybFlow code, Research code developed in the past at University of Florence. Grid generation for the fanshaped holes test case has been concluded to share the grid with other partners. Furthermore, a grid refinement technique have been developed and tested on the WP3.1 test cases and it has been already successfully tested in the WP2.3 test case, too. Investigation of the cooled platform has been concluded and a short collaboration with MTU and EPFL on the CFD aspects has been done. The obtained knowledge helped us to decide the next improvements in the CFD code and to correct some model s approximations. Considering the WP objectives, they have been reached without any deviation from the work-programme. A Second activity (Task 4.2) was focused on the steady and unsteady stage aerodynamics & heat transfer simulation of the selected cases. A lot of efforts have been dedicated to the improvement of the computing efficiency in terms of accuracy of unsteady treatment, computational time diminishing and transition modelling. The computational time have been diminished by a factor of 33% by changing the CFD code algorithm. Most of the tested experimental cases (MT1 and CT3 test cases, WP1 and WP2) have been computed in unsteady configuration The CFD simulation of the Enhanced OTDF and the Flow with Strong Shocks cases have been performed and the results have been compared with the experimental data. Unsteady Quasi-3D simulation of CT3 test case with Strong Shocks has been completed. Furthermore some steady simulations on the CT3 test case for the platform cooling have been done in collaboration with SNECMA and ONERA to understand the segregated effects of some technological features on the flow field of the rotor vane of the CT3 test case. Calculations with three different CFD codes [ELSAdeveloped at ONERA, CEDRE-developed at ONERA, HybFlow-developed and used by U-Flor T.E.E.G.] have been realized and the results obtained are deeply compared. Considering the unsteady method for the stage computations, a Phase Lag approach have been considered and successfully implemented in the HybFlow CFD code. It has been tested on the WP2.2 mid-span. The simulation of these cases allowed to demonstrate the reliability of the HybFlow code on these kind of test cases. Considering the WP objectives, they have been reached without any deviation from the work-programme and many publications have been realized on the performed simulations. In Fig. 11 two results of the HybFlow calculation performed on experimented configurations are reported. Figure 11 - Tip leakage vortex development (MT1, WP1.1) and shock system (CT3, WP2.2) FAR_ed0 Page 10 of 11

11 The activity of the Industrial partners has been concentrated in the development of Stage aerodynamics & heat transfer calculation. The test matrix from Industrial partners has been completed. The main objectives for this task are the supervision and support to the CFD simulations done by the Ind. Partner. U-Flor, provided the data collection from the Exp, the geometries, the boundaries conditions and updated the existing database for the CFD calculations with the experimental and numerical results available. They have been acting as a referring point for the partners. In some cases grid generation and other data needed for calculations have been provided. Several tools have been prepared for the post-processing of the steady and unsteady stage computations. A web page for all the partners have been implemented with all the data divided in an open and restricted areas according to the industrial and research institution needs. This was not originally planned in the program, but it proved to be very useful both for internal exchange and assessment and for exploitation. Considering the WP objectives, they have been reached over the expectations. Finally all the collected data from calculations and experiments have been compared and some guidelines and suggestions on the best practise for improved accuracy of the CFD tools is going to be prepared together with a report on the improvements achieved on the numerical and physical modelling of the Computational tools. Validation of numerical methods and assessment has been achieved with improvements in modelling capacity. Deep Investigation of the complex time-averaged and time resolved flow field has resulted in a better understanding of the aerodynamics and the heat transfer in basic film cooling configuration, as well as in stage behaviour. The socio-economic impacts of this Work can be summarised in the improvements, through the high number of PhD student and young researchers who have been involved in the calculations, research, investigation and analyses of the results, of the competitiveness the Fluid dynamics and Engineering European Community, in an enlargement of the employment opportunity and in increase of the feeling towards the environmental items, as the achievement of better and longer performance of the aero-engines will result in a reduced environmental impact of the aeronautical transportation. From the point of view of the Universities the improved knowledge of the problems and tools involved in the design of aero-engines will results in a better teaching capability closer and closer to the need of an advance society based on the knowledge, and to the European feeling of the crucial needs for the future of our new generations: Environment, Competitiveness and skills increase as engines for the harmonic development of European and World Economy. The performed work since the start of the programme has resulted in 26 milestones and 44 deliverables. On the dissemination side, has been prolific since 36 articles were submitted, joining a long list of more than 40 publications about TATEF1 subjects since the closure of this project. The administrative documents are agreed and signed: associated contracts (EC contract and Form A), Consortium Agreement and both research contracts (testing activity in QinetiQ and in VKI). During the building of the project, O. SGARZI was the coordinator. Then Th. COTON was in charge of the coordination from the 1 st of July 2004 till September R. OLIVE was nominated to be his successor and thus has written this Final Activity Report. Rémi OLIVE SNECMA - Groupe Safran Tel: remi.olive@snecma.fr FAR_ed0 Page 11 of 11