| 1. |
- Gao, Yang, et al.
(författare)
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Numerical Investigation of the Performance Impact of Stator Tilting Endwall Designs on a Mixed Flow Turbine
- 2021
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Ingår i: INTERNATIONAL JOURNAL OF TURBOMACHINERY PROPULSION AND POWER. - : MDPI AG. - 2504-186X. ; 6:2, s. 14-
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Tidskriftsartikel (refereegranskat)abstract
- This paper numerically investigates stator endwall designs for a mixed flow turbine. One key design parameter studied is the tilting angle of the stator endwall. By examining stator designs with different tilting angles, the aim of this paper is to improve the efficiency of the studied mixed flow turbine at low velocity ratio working conditions. The performance curve at the design speed was chosen for the comparison between the baseline design and the tilted endwall designs. First, the numerical predictions for the baseline design were validated with experimental data. Then, to understand the mechanism of the performance variation between the different designs, the internal flow field was analyzed in detail. It was found that the tilting stator endwall could form a geometric "kink" in the endwall profiles. On the shroud side, certain designs with such kink caused local flow separations upstream the rotor leading edge. This separation could have the effect of reducing the intensity of the tip leakage vortex and the exit kinetic energy losses at the rotor outlet and may also improve the performance of the exhaust diffuser. As a result, the peak of the efficiency curve shifted toward lower velocity ratio. If the turbine stage incorporated a downstream exhaust diffuser, the optimal design in this study showed a shift of the velocity ratio of the peak efficiency point from 0.62 to 0.60 compared with the baseline. The maximum efficiency improvement was 1.3% points, which occurred at low velocity ratio. Meanwhile, the peak efficiency was 0.2% points higher than the baseline. If the exhaust diffuser was removed, a similar shift of the efficiency curve was observed but less efficiency gain was achieved at the low velocity ratio condition. A preliminary unsteady simulation was also conducted for the optimal design in this study.
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| 2. |
- Jonsson, Isak, 1990, et al.
(författare)
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Infrared Thermography Investigation of Heat Transfer on Outlet Guide Vanes in a Turbine Rear Structure
- 2020
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - : MDPI AG. - 2504-186X. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Aerothermal heat transfer measurements in fluid dynamics have a relatively high acceptance of uncertainty due to the intricate nature of the experiments. The large velocity and pressure gradients present in turbomachinery application add further complexity to the measurement procedure. Recent method and manufacturing development has addressed some of the primary sources of uncertainty in these heat transfer measurements. However, new methods have so far not been applied in a holistic approach for heat transfer studies. This gap is bridged in the present study where a cost-effective and highly accurate method for heat transfer measurements is implemented, utilising infrared thermography technique (IRT) for surface temperature measurement. Novel heat transfer results are obtained for the turbine rear sturcture (TRS), at engine representative conditions for three different outlet guide vane (OGV) blade loading and at Reynolds Number of 235000. In addition to that, an extensive description of the implementation and error mitigation is presented.
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| 3. |
- Sundström, Elias, et al.
(författare)
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Analysis of Vaneless Diffuser Stall Instability in a Centrifugal Compressor
- 2017
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Ingår i: International Journal of Turbomachinery Propulsion and Power. - Basel, Switzerland : MDPI AG. - 2504-186X. ; 2:4
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Tidskriftsartikel (refereegranskat)abstract
- Numerical simulations based on the large eddy simulation approach were conducted with the aim to explore vaneless diffuser rotating stall instability in a centrifugal compressor. The effect of the impeller blade passage was included as an inlet boundary condition with sufficiently low flow angle relative to the tangent to provoke the instability and cause circulation in the diffuser core flow. Flow quantities, velocity and pressure, were extracted to accumulate statistics for calculating mean velocity and mean Reynolds stresses in the wall-to-wall direction. The paper focuses on the assessment of the complex response of the system to the velocity perturbations imposed, the resulting pressure gradient and flow curvature effects.
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| 4. |
- Szász, Robert-Zoltán, et al.
(författare)
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Numerical modelling of the ice throw from wind turbines
- 2019
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - : MDPI AG. - 2504-186X. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Ice throw is a significant risk factor in the vicinity of wind turbines located in cold climate areas. We present a method to estimate the ice chunk trajectories. First, similar to the common practice, only translation is accounted for and the object trajectory is determined by gravity and the aerodynamic drag force. The sensitivity of the trajectories to the launch positions, wind speed, turbine rotation and aerodynamic drag is assessed. Next, trajectory computations with six-degree-of-freedom motion are presented. The required aerodynamic forces and moments are precomputed using CFD. The results indicate that object rotation might be non-negligible when higher accuracy is needed for the trajectory estimates.
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| 5. |
- Barigozzi, Giovanna, et al.
(författare)
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The Aero-Thermal Performance of Purge Flow and Discrete Holes Film Cooling of Rotor Blade Platform in Modern High Pressure Gas Turbines: A Review
- 2022
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - : MDPI AG. - 2504-186X. ; 7:3
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Forskningsöversikt (refereegranskat)abstract
- Design of cooling systems for rotor platforms is critical due to the complex flow field and heat transfer phenomena related to the secondary flow structures originating at the blade leading edge. Horseshoe vortex and passage vortex are the fluid-dynamic features that largely influence the aerodynamic behaviour and the thermal protection level of the platform. The driving parameter is the coolant to mainstream momentum flux ratio, but several issues have to be considered in the design process of cooling technologies. As well acknowledged, an in-depth understanding of losses and heat transfer phenomena are deemed necessary to design effective cooling systems. In the present review, measurements and predictions on the behaviour of the HPT rotor cooled platform, obtained during the last two decades by several research groups, are gathered, described and analysed in terms of aerodynamic losses and heat transfer performance, and are compared with one another with respect to the effectiveness level that is ensured.
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| 6. |
- Dahlqvist, Johan, et al.
(författare)
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Purge Flow Impact on Turbine Stage and Seal Performance at Varying Cavity Purge Rates and Operating Speed
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - 2504-186X.
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Tidskriftsartikel (refereegranskat)abstract
- The impact of the wheelspace cavity purge flow on a high-pressure axial low-reaction turbine stage is investigated. Both the flow's sealing ability and the performance impact associated with its injection are studied. Two operating speeds are tested, namely a high loading case and the peak efficiency, with purge flow rates covering a wide range. As the purge flow is injected upstream of the rotor, the sealing effectiveness is quantified both radially and tangentially close to the rim seal, where the tangential variation is used to identify the seal mixing region. Having passed the rotor blading, the purge flow distribution in the main annulus is quantified, showing an influence of operating speed. The purge flow core is localized to the trace of the vane wake, however somewhat migrated while passing through the blading. The combination of measurements shows that the impact on flow parameters cannot be used to determine the spanwise transport of the purge flow; hence two techniques are necessary to both judge the spanwise transport and impact on flow. With known sealing effectiveness, industry correlations may be adapted to make use of the variation of necessary purge rate to obtain a certain degree of effectiveness at a given operating point, and thereby optimize the efficiency. Also the distribution of the coolant in the main flow path may be used to optimize film cooling in that area.
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| 7. |
- Feuk, Henrik, et al.
(författare)
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Impact of Methane and Hydrogen-Enriched Methane Pilot Injection on the Surface Temperature of a Scaled-Down Burner Nozzle Measured Using Phosphor Thermometry
- 2022
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - : MDPI AG. - 2504-186X. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- The surface temperature of a burner nozzle using three different pilot hardware configurations was measured using lifetime phosphor thermometry with the ZnS:Ag phosphor in a gas turbine model combustor designed to mimic the Siemens DLE (Dry Low Emission) burner. The three pilot hardware configurations included a non-premixed pilot injection setup and two partially premixed pilot injections where one had a relatively higher degree of premixing. For each pilot hardware configuration, the combustor was operated with either methane or hydrogen-enriched methane (H2/CH4: 50/50 in volume %). The local heating from pilot flames was much more significant for hydrogen-enriched methane compared with pure methane due to the pilot flames being in general more closely attached to the pilot nozzles with hydrogen-enriched methane. For the methane fuel, the average surface temperature of the burner nozzle was approximately 40 K higher for the partially premixed pilot injection configuration with a lower degree of mixing as compared to the non-premixed pilot injection configuration. In contrast, with the hydrogen-enriched methane fuel, the differences in surface temperature between the different pilot injection hardware configurations were much smaller due to the close-to-nozzle frame structure.
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| 8. |
- Kilian, Nicklas, et al.
(författare)
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Numerical investigation of forced response in a transonic compressor stage-highlighting challenges using experimental validation
- 2024
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - : MDPI AG. - 2504-186X. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- An experiment-supported simulation process chain is set up to perform numerical forced response analyses on a transonic high-pressure compressor front stage at varying operating conditions. A wake generator is used upstream of the rotor to excite a specific resonance within the operating range of the compressor. Thereby, extensive aerodynamic and structural dynamic experimental data, obtained from state-of-the-art rig testing at the Transonic Compressor Darmstadt test facility at the Technical University of Darmstadt, are used to validate numerical results and ensure realistic boundary conditions. In the course of this, five-hole-probe measurements at steady operating conditions close to the investigated resonance enable a validation of the steady aerodynamics. Subsequently, numerically obtained aeroelastic quantities, such as resonance frequency, and damping, as well as maximum alternating blade stresses and tip deflections, are compared to experimental blade tip timing data. Experimental trends in damping can be confirmed and better explained by considering numerical results regarding the aerodynamic wall work density and secondary flow phenomena. The influence of varying loading conditions on the resonance frequency is not observed as distinctly in numerical, as in experimental results. Generally, alternating blade stresses and deflections appear to be significantly lower than in the experiments. However, similar to the aerodynamic damping, numerical results contribute to a better understanding of experimental trends. The successive experimental validation shows the capabilities of the numerical forced response analysis setup and enables the highlighting of challenges and identification of potential further adaptations.
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| 9. |
- Nambiar, Sanjay, 1997-, et al.
(författare)
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Multidisciplinary Automation in Design of Turbine Vane Cooling Channels
- 2024
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - : MDPI. - 2504-186X. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- In the quest to enhance the efficiency of gas turbines, there is a growing demand for innovative solutions to optimize high-pressure turbine blade cooling. However, the traditional methods for achieving this optimization are known for their complexity and time-consuming nature. We present an automation framework to streamline the design, meshing, and structural analysis of cooling channels, achieving design automation at both the morphological and topological levels. This framework offers a comprehensive approach for evaluating turbine blade lifetime and enabling multidisciplinary design analyses, emphasizing flexibility in turbine cooling design through high-level CAD templates and knowledge-based engineering. The streamlined automation process, supported by a knowledge base, ensures continuity in both the mesh and structural simulation automations, contributing significantly to advancements in gas turbine technology.
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| 10. |
- Ottersten, Martin, 1981, et al.
(författare)
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Inlet Gap Effect on Tonal Noise Generated from a Voluteless Centrifugal Fan
- 2022
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - : MDPI AG. - 2504-186X. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- In this study, three voluteless centrifugal fans are compared for their aeroacoustic performances. The tonal noise is predicted by coupling the IDDES with Formulation 1A of Farassat. The sources of the tonal noise at the blade passing frequency (BPF) are identified. It is found that the sources are related to the fan inlet gap, which introduces higher velocity intensities and turbulent fluctuations interacting with the blade leading edge. By redesigning the gap, the tonal noise at the BPF is reduced effectively.
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| 11. |
- Sjögren, Oliver, 1993, et al.
(författare)
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FAN STAGE DESIGN AND PERFORMANCE OPTIMIZATION FOR LOW SPECIFIC THRUST TURBOFANS
- 2023
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Ingår i: International Journal of Turbomachinery, Propulsion and Power. - 2504-186X. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- In modern turbofan engines the bypass section of the fan stage alone provides the majority of the total thrust in cruise and the size of the fan has a considerable effect on overall engine weight and nacelle drag. Thrust requirements in different parts of the flight envelope must also be satisfied together with sufficient margins towards stall. An accurate description of the interdependencies of relevant performance and design attributes of the fan stage alone - such as efficiency, surge margin, fan-face Mach number, stage loading, flow coefficient and aspect ratio - are therefore necessary to estimate system level objectives such as mission fuel burn and direct operating cost with enough confidence during the conceptual design phase. The contribution of this study is to apply a parametric optimization approach to conceptual design of fan stages for low specific thrust turbofans based on the streamline curvature method. Trade-offs between fan stage attributes for Pareto-optimal solutions are modelled by training a Kriging surrogate model on the results from the parametric optimization. The trends predicted by the resulting surrogate model are analyzed both quantitatively and qualitatively. Most of the trends could be justified with some degree of physical reasoning or comparison with common guidelines from the literature. Trends of stage efficiency with Mach number and stage loading may indicate that shock losses have a larger impact on stage efficiency for designs with low stage loading compared to designs with high stage loading. Means to reduce the strength of the passage shock wave, such as blade sweep, may therefore be of more importance as stage loading is reduced.
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