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- Arroyo, Carlos, 1977
(författare)
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Aerothermal Investigation of an Intermediate Turbine Duct
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Intermediate turbine ducts are used to guide the flow in turbofan engines from the short-radius high-pressure turbine to the large-radius low-pressure turbine. The demand for more efficient and silent jet engines and with a reduced environmental impact requires turbofans with increasingly higher by-pass ratios. Intermediate turbine ducts that could provide a greater radial offset in shorter length would contribute greatly to achieving this goal, especially if they maintained low pressure losses and avoided non-uniformities in the outlet flow that might affect the downstream low-pressure turbine. This thesis presents an experimental study of the flowfield and the heat transfer in an aggressive intermediate turbine duct. The goals of this research were to obtain an understanding of the mechanisms governing the heat transfer in intermediate turbine ducts; and as well, to provide detailed high-quality flow and heat transfer experimental data for CFD validation purposes.The experiments were carried out in a state-of-the-art aggressive intermediate turbine duct with structural struts in a large-scale low-speed turbine facility at realistic engine Reynolds numbers and inlet conditions. For the flow measurements, oil-film visualization, static pressure measurements, 5-hole pressure probe and hot-wire anemometry were used. The heat transfer measurements were performed using a technique based on IR-thermography. The experiments were performed for three different turbine operating points in order to evaluate the effect of inlet swirl on the flow and heat transfer in the duct. The results showed that the stationary flow features arising from the upstream turbine had a large effect on both the flowfield and the heat transfer in the duct. The combination of tip leakage flow and structural struts gave rise to a large vortex with changing relative strength for different inlet swirl. This vortex locally dominated the heat transfer in the neighborhood of the suction side of the vane. Also, counter-rotating vortex pairs near the hub created streaks of low and high heat transfer coefficient that varied ±20% on the hub. For a lower inlet swirl angle, flow separation occurred at the corner between the shroud endwall and the strut pressure side due to the mismatch of the strut and flow angles in the tip leakage region. These flow separations created large circumferential variations in the duct outflow, and significantly modified the flowfield and heat transfer on the endwalls where an increase in the heat transfer coefficient of up to 25% was seen. These and other important effects of the flowfield on the heat transfer distributions have been identified. The results provide valuable insights into duct flow phenomena and how they are coupled to the heat transfer. Together they represent a first step towards understanding the heat transfer phenomena in the duct. The results are already being used to improve design methods in industry.Keywords: Intermediate turbine duct, flowfield measurements, heat transfer measurements.
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| 2. |
- Arroyo, Carlos, 1977, et al.
(författare)
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Experimental and Numerical Investigation of an Aggressive Intermediate Turbine Duct: Part 2−Flowfield under Off-Design Inlet Conditions
- 2008
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Ingår i: Collection of Technical Papers - AIAA Applied Aerodynamics Conference. - Reston, Virigina : American Institute of Aeronautics and Astronautics. - 1048-5953.
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Konferensbidrag (refereegranskat)abstract
- Intermediate turbine ducts (ITD’s) are annular S-shaped channels used in turbofan engines to guide the flow between the small-radius high-pressure turbine and the large-radius lowpressureturbine. This paper is the second part of a two-part paper presenting the results of acombined experimental and computational investigation of the flow in an aggressiveintermediate turbine duct. The first part of the paper focused on the flowfield under the ITDdesign conditions. This second part of the paper presents and analyses the flowfield andperformance under two off-design conditions (i.e. lower and higher turbine load). The focus ison the changes of the flowfield for these conditions as the inlet flow angles differ from thedesign values (e.g. flow separation occurs in the duct for the lower turbine load case) and theeffect of this change on the duct performance. Total pressure losses are seen to increase forboth off-design cases, especially for the case with flow separation (lower turbine load). Thestatic pressure recovery is also found to be lower for the case with flow separation while for thehigher turbine load tested it remains almost unchanged. In addition, differences foundbetween the measured and predicted performance parameters are discussed. The experimentalstudy was performed in a large-scale, low-speed turbine facility. The CFD computations wereperformed for the same flow conditions and used boundary conditions based on the measuredinlet plane.
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| 3. |
- Arroyo, Carlos, 1977, et al.
(författare)
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Experimental Heat Transfer Investigation of an Aggressive Intermediate Turbine Duct
- 2012
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Ingår i: Journal of Turbomachinery. - : ASME International. - 1528-8900 .- 0889-504X. ; 134:5
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Tidskriftsartikel (refereegranskat)abstract
- In most designs of two-spool turbofan engines, intermediate turbine ducts (ITDs) are used to connect the high-pressure turbine (HPT) with the low-pressure turbine (LPT). Demands for more efficient engines with reduced emissions require more "aggressive ducts," ducts which provide both a higher radial offset and a larger area ratio in the shortest possible length, while maintaining low pressure losses and avoiding nonuniformities in the outlet flow that might affect the performance of the downstream LPT. The work presented in this paper is part of a more comprehensive experimental and computational study of the flowfield and the heat transfer in an aggressive ITD. The main objectives of the study were to obtain an understanding of the mechanisms governing the heat transfer in ITDs and to obtain high quality experimental data for the improvement of the CFD-based design tools. This paper presents and discusses the results of the experimental study. The duct studied was a state-of-the-art "aggressive" design with nine thick nonturning structural struts. It was tested in a large-scale low-speed experimental facility with a single-stage HPT. In this paper measurements of the steady convective heat transfer coefficient (HTC) distribution on both endwalls and on the strut for the duct design inlet conditions are presented. The heat transfer measurement technique used is based on infrared thermography. Part of the results of the flow measurements is also included.
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| 8. |
- Wallin, Fredrik, 1978, et al.
(författare)
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Experimental and Numerical Investigation of an Aggressive Intermediate Turbine Duct: Part 1−Flowfield at Design Inlet Conditions
- 2008
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Ingår i: Paper AIAA-2008-7055, 26th AIAA Applied Aerodynamics Conference, Honolulu, August 18-21, 2008. - Reston, Virigina : American Institute of Aeronautics and Astronautics. - 1048-5953.
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Konferensbidrag (refereegranskat)abstract
- Demands on lower emissions and reduced noise levels drive the design of modern turbofan engines toward high by-pass ratios. The design of the intermediate turbine ducts, connecting the high- and low-pressure turbines, will become more important as the turbofan engine by-pass ratios are increased. In order to introduce more aggressive designs there is a need to understand the flow features of high aspect ratio and high diffusion ducts. This is part one of a two-part paper, presenting a comparison between an experimental study and a CFD analysis of the flowfield of an aggressive intermediate turbine duct for design inlet conditions. Part one focuses on the on-design conditions and the second part will focus on off-design conditions. The experimental study was performed in a large-scale, low-speed turbine facility. The work presented highlights some of the challenges associated with more aggressive intermediate ducts for the next generation of turbofan engines. The main flow features are successfully reproduced by the CFD, but there are discrepancies found in the predicted local velocity and loss levels. An explanation of the discrepancies between the experimental data and the CFD results is provided and an attempt to track the origin of these differences is made.
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| 9. |
- Wallin, Fredrik, et al.
(författare)
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Heat transfer investigation of an aggressive intermediate turbine duct: Part 2 - Numerical analysis
- 2010
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Ingår i: Proceedings of the ASME Turbo Expo, Power for Land, Sea, and Air, GT 2010, Glasgow, 14 June 2010 through 18 June 2010. ; 4:PARTS A AND B,, s. 81-89
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Konferensbidrag (refereegranskat)
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