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Test Turbine Measurements and Comparison with Mean-Line and Throughflow Calculations

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Test Turbine Measurements and Comparison with Mean-Line and Throughflow Calculations Test turbine measurements and comparison with mean-line and throughflow calculations NAVID MIKAILLIAN Master of Science Thesis KTH School of Industrial Engineering and Management Energy Technology EGI-2012-091MSC Division of EKV SE-100 44 STOCKHOLM Master of Science Thesis EGI 2012:091MSC EKV917 Test turbine measurements and comparison with mean-line and throughflow calculations Navid Mikaillian Approved Examiner Supervisor 25-Oct-2012 Ass. Prof. Damian Vogt Dr. Jens Fridh Commissioner Contact person Abstract This thesis is a collaboration between Siemens Industrial Turbomachinery(SIT) and Royal Institute of Technology(KTH). It is aimed to study and compare the outputs of two different computational approaches in axial gas turbine design procedure with the data obtained from experimental work on a test turbine. The main focus during this research is to extend the available test databank and to further understand and investigate the turbine stage efficiency, mass flow parameters and reaction degree under different working conditions. Meanwhile the concept and effect of different loss mechanisms and models will be briefly studied. The experimental part was performed at Heat and Power Technology department on a single stage test turbine in its full admission mode. Three different pressure ratios were tested. For the medium pressure ratio a constant temperature anemometry (CTA) method was deployed in two cases, with and without turbulence grid, to determine the effect of free-stream turbulence intensity on the investigated parameters. During the test campaign the raw gathered data was processed with online tools and also they served as boundary condition for the computational codes later. The computational scope includes a one-dimensional design approach known as mean-line calculation and also a two-dimensional method known as throughflow calculation. An in-house SIT software, CATO, generated the stage geometry (vane, blade and the channel) and then two other internal computational codes, MAC1 and BETA2, were employed for the one-dimensional and two-dimensional computations respectively. It was observed that to obtain more accurate mass flow predictions a certain level of channel blockage should be implemented to represent the boundary layer development and secondary flow which is typically around 2%. The codes are also equipped with two options to predict the friction loss: One is a more empirical correlation named as the Old approach in SIT manuals and the other works based on allocation of boundary layer transition point, named as BL in the present thesis. Simulations were done by use of both approaches and it turned out that the latter works more accurately if it is provided with appropriate transition point and blockage estimation. The measured data also suggests the idea that the transition point of the vane and blade is not affected by a change in turbulence intensity at least up to 6% in the tested Reynolds numbers, ~ 5 × 105. Amongst -i- different solutions the one which used BL approach and constant transition point (while the turbulence intensity changed) managed to predict this behavior. Also it was investigated and revealed that the codes inherently predict poor results in off-design loadings which is mainly due to positive incidence angle in addition to high spanwise gradient of the flow parameters. -ii- Acknowledgments Immediately I would like to thank my very dedicated supervisors Dr. Jens Fridh, KTH, and Lars Hedlund at Siemens Industrial Turbomachinery, SIT. I had their great support during this study and they led the project to be also a compact gas turbine course for me via a perfect plan. Furthermore my thanks will go to Mats Annerfeldt for giving me the opportunity to do my thesis in SIT, Ted Jablonowski and Aliaksandr Rahachou for their precious time and aid to solve the technical problems and even update my required codes, Ake Klang and Ken Flydalen whom enthusiastically shared their knowledge with me and all the other members of SIT Aerodynamics group. In addition I will never forget the joyous moments I had with the other diploma-workers. Thank you all my good friends! Also I want to appreciate the kind help of the technical staffs at Heat and Power Technology department, KTH, especially Leif Pettersson who really assisted me during the experimental part of this task. Last but of course not the least, there will be my special gratitude to my beloved fiancée Farzaneh, whom always encouraged me with love from four thousand kilometers away. -iii- Table of Contents Abstract ............................................................................................................................................................................ i Acknowledgments ........................................................................................................................................................ iii Table of Contents ......................................................................................................................................................... iv List of Figures ............................................................................................................................................................... vi List of Tables ................................................................................................................................................................. xi Nomenclature............................................................................................................................................................... xii 1 Introduction .......................................................................................................................................................... 1 1.1 Background .................................................................................................................................................. 1 1.2 Objective....................................................................................................................................................... 1 1.3 Method .......................................................................................................................................................... 2 1.4 Limitations.................................................................................................................................................... 2 2 Turbine Theory ..................................................................................................................................................... 3 2.1 Gas Turbine Outline ................................................................................................................................... 3 2.2 Generation of Work in a Turbine Stage .................................................................................................. 4 2.3 Turbine Parameters ..................................................................................................................................... 6 2.3.1 Total-to-total and Total-to-static Efficiencies ............................................................................... 6 2.3.2 Degree of Reaction ............................................................................................................................ 7 2.3.3 Stage Loading Coefficient ................................................................................................................. 7 2.3.4 Flow Coefficient ................................................................................................................................. 8 2.3.5 Velocity Ratio ..................................................................................................................................... 8 2.3.6 Flow Capacity ..................................................................................................................................... 8 2.3.7 Turbine Constant ............................................................................................................................... 9 3 Structure of Computational Methods .............................................................................................................10 3.1 Mean-line Turbine Calculations ..............................................................................................................10 3.2 Through-flow Turbine Calculations .......................................................................................................14 4 Experimental Method ........................................................................................................................................23 4.1 Test Turbine Specifications and Instrumentations ..............................................................................23 4.2 Performed Tests ........................................................................................................................................26 4.3 Experiments Results and Discussions ...................................................................................................26 4.3.1 Mass Flow, Turbine constant and Flow Coefficient ..................................................................27 4.3.2 Stage Efficiency ................................................................................................................................29 4.3.3 Degree of Reaction ..........................................................................................................................31
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