| 1. |
- Deshpande, Srikanth, et al.
(författare)
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Effect of spanwise variation of chord on the performance of a turbine cascade
- 2017
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Ingår i: Turbomachinery. - 9780791850787 ; 2A-2017
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Konferensbidrag (refereegranskat)abstract
- This paper compares the aerodynamic performance of two cascade designs, viz.: -constant-chord and varying-chord. The varying-chord design is typical of industrial gas turbines and steam turbine stators in order to reduce manufacturing costs. The present study aims to increase the understanding of the implications of this manufacturing constraint on the aerodynamics of the stator. Experiments are carried out in a linear cascade wind tunnel. Numerical simulations are performed using commercial code CFX. The profile losses and secondary losses in the two designs are compared. The overall total pressure losses indicate better aerodynamic performance of a turbine cascade with constant chord as compared to a turbine cascade of varying-chord design
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| 2. |
- Deshpande, Srikanth, et al.
(författare)
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EFFECT OF SURFACE ROUGHNESS ON AERODYNAMIC PERFORMANCE OF TURBINE REAR STRUCTURE
- 2019
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Ingår i: Proceedings of the ASME Turbo Expo.
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Konferensbidrag (refereegranskat)abstract
- A turbine rear structure (TRS) is typically used to deswirl the flow from the low pressure turbine (LPT) and hence maximize the axial thrust. It is important to study the effect of surface roughness on aerodynamic performance of TRS. Numerical simulations with surface roughness are performed and results are compared with the data from experiments. Comparisons show that the trends between the numerical analysis and the experiments are in line with one another. Further understanding of numerical analysis shows that, at higher Reynolds number, the effect ofsurface roughness is more significant when compared to the effects at low-Reynolds number. An attempt has been made to study the transition behavior in the presence of surface roughness. Since boundary layer measurements are planned for the rig, this numerical study provides good inputs in order to plan instrumentation..
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| 3. |
- Deshpande, Srikanth, et al.
(författare)
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Efficiency improvements in an industrial steam turbine stage - Part 1
- 2016
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Ingår i: Turbomachinery. - 9780791849705 ; 2B-2016
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Konferensbidrag (refereegranskat)abstract
- The present work approaches the idea of increasing the efficiency of an industrial steam turbine stage. For this endeavor, an industrial steam turbine stage comprising of prismatic stator and rotor is considered. With the velocity triangles as input, airfoil design is carried out. Firstly, the rotor is redesigned to take care of any incidence issues in the baseline case. In rotor blades, the peak Mach number is reduced in blade to blade flow passage and hence, efficiency of stage is increased. Rotor is made front loaded. After finalizing the rotor, the stator is redesigned. Stator is made more aft-loaded when compared to the baseline case. By making the stator aft-loaded, the efficiency increased by reducing profile losses. This design modification also showed advantage in secondary losses. The total pressure loss in the stator was reduced by a delta of 0.15. When creating an airfoil for stator or rotor, MISES was used in order to evaluate profile losses. The design verification for the stage was numerically done using commercial CFD software ANSYS CFX. Steady state RANS simulations were carried out. The stator and the rotor still being prismatic, only by virtue of airfoil design, the total to total stage efficiency improvement of 0.33% was predicted.
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| 4. |
- Deshpande, Srikanth, et al.
(författare)
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Efficiency improvements in an industrial steam turbine stage - Part 2
- 2016
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Ingår i: Turbomachinery. - 9780791849705 ; 2B-2016
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Konferensbidrag (refereegranskat)abstract
- Improvement in isentropic total to total efficiency of a low reaction turbine stage by airfoil redesign was considered in first part of the paper. Further, modifications in the flow path of the baseline stage is considered in second part of the paper. Flow path of the baseline stage incorporates axisymmetric meridional endwall contour(commonly called Russian kink). For a stage comprising of high aspect ratio blades, assessment of performance with endwall contour is performed. Alternatives, if required for endwall contour had to be explored and numerically verified. Endeavor in the present paper is in this direction. Static pressure distribution at the stator exit is considered as the main objective. Along with flow path modification, stator modifications like vortexing and lean are attempted to obtain stator exit static pressure distribution similar to baseline case. Straight lean on stator provides good results in terms of reducing stator exit pressure gradient as well as reducing gradient of rotor inlet swirl. Since the pressure distribution at stator exit also drives the tip leakage flow, effect of flowpath and stator modifications on tip leakage flow is studied. Performance numbers are reported for cases with and without tip shroud.
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| 5. |
- Deshpande, Srikanth
(författare)
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Improved Steam Turbine Design for Optimum Efficiency and Reduced Cost of Ownership
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The cost of ownership of a power plant is partly governed by the efficiency of the turbine island. The turbine stands for the production revenues when transforming the energy in fuel into electric power and district heating. One gauge of the quality of the individual processes is the component efficiency - the current work addresses the turbine part of the power plant. The turbine efficiency is dependent on both process parameters and the blading aerodynamics. The former is typically the steam data (e.g. temperature, pressure and mass flow) that influences the volumetric flow through the turbine. The blading aerodynamics is the local flow process in each stage in the turbine. The efficiency of a stage (i.e. a stator and a rotor) is limited by losses due to dissipation in boundary layers,losses due to secondary flows, leakage mixing and lost work, etc. Most previous development efforts in the industrial steam turbine segment have been towards reduced first cost and not necessarily the efficiency. Most industrial steam turbines utilize prismatic (or un-twisted) blades for shorter stages. A constant section rotor blade typically is milled in a two-axis machine whilst more advancedshapes require five-axis flank milling. The costs associated with the latter have today leveled with the simpler manufacturing methods. This technology step has been introduced in larger size utility type of turbines with very high attainable efficiency levels. An industrial size steam turbine cannot reach the same level of efficiency and lags several points behind as for a utility type unit, because of the lower volumetric flow and the cylinder pressure ratio. The focus in the present work has been to reduce the losses and hence increase efficiency in an industrial size steam turbine stage. Profile losses and secondary losses being the two main targets to improve performance, the work is focused on both the loss mechanisms. The work has been carried out by state-of-the-art turbine design tools and comprises: one-dimensional tool, two-dimensional blade-to-blade flow analysis and full three-dimensional high-fidelity CFD. The datum stage is atall stage in an assumed Siemens SST- turbine. The work, however, is generic for low-reaction steam turbines. The work shows that the stage performance can be increased. The significant improvement obtained fromnumerical prediction makes a strong case for the proposed design modifications to be considered.
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| 6. |
- Deshpande, Srikanth, et al.
(författare)
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Influence of compound lean on an industrial steam turbine stage
- 2015
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Ingår i: ASME 2015 Gas Turbine India Conference, GTINDIA 2015. - 9780791857311
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Konferensbidrag (refereegranskat)abstract
- Compound lean implemented on stator of an industrial steam turbine stage in order to reduce secondary losses are discussed. Baseline stator is a prismatic vane with aspect ratio of unity. Compound lean stator blade is designed by shearing the airfoil sections in tangential direction. Modifications are analyzed numerically using commercial code CFX. Three blade rows i.e. one complete stage with a downstream stator are analyzed. Steady state Reynolds averaged Navier Stokes equations are solved. Total pressure loss (TPL) is used as objective function to monitor reduction in secondary losses. Rotor is retained the same for baseline as well as compound leaned stator. Results show reduction in total pressure loss of stator in excess of 5%. Also, computations of coefficient of secondary kinetic energy shows significant reduction in secondary losses in excess of 30% in stator. Efficiency gained by implementation of compound lean are discussed.
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| 7. |
- Deshpande, Srikanth, et al.
(författare)
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Reduction in Secondary Losses in Turbine Cascade Using Contoured Boundary Layer Fence
- 2014
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Ingår i: Proceedings of the ASME 2014 Gas Turbine India Conference. - 9780791849644 ; , s. 2014-8175
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Konferensbidrag (refereegranskat)abstract
- Present work deals with reducing secondary losses in turbine cascade by using boundary layer fences in two ways. Firstly, to reduce the strength of vortex which is incident at the leading edge of airfoil and hence reduce the strength of horse shoe vortex, and secondly, to reduce the pressure gradient between the pressure side and the suction side in the flow passage region between airfoils. In previous works, the boundary layer fence followed the profile of airfoil. In this publication, boundary layer fence does not follow the profile of airfoil i.e stagger and camber of boundary fence is different when compared to airfoil. A profiled boundary layer fence is proposed in the present work which reduces the incident voracity and also reduces pressure gradient from pressure side to suction side. Such boundary layer fence was checked on T106 test cascade which is available as open literature. Numerical work is carried out using commercial software Ansys CFX. Viscous RANS simulations are carried out using k-omega SST turbulence model with yplus value around unity on all walls. Coefficient of secondary kinetic energy (CSKE) and Secondary Kinetic energy helicity (SKEH) are used as target functions. Total pressure loss is also monitored. All the three functions show a reduction in secondary loss. The strength of horse shoe vortex is reduced by the fence protruding in front of leading edge. The converging flow passage created by the fence near the pressure side of airfoil reduces the pressure gradient from pressure side to suction side. The total pressure loss was reduced by 1.5 % and CSKE was improved by 36 % when the boundary layer fence was adopted.
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| 8. |
- Deshpande, Srikanth, et al.
(författare)
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Vortexing methods to reduce secondary losses in a low reaction industrial turbine
- 2015
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Ingår i: Turbomachinery. - 9780791856635 ; 2A
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Konferensbidrag (refereegranskat)abstract
- Vortexing methods implemented on an industrial steam turbine vane in order to reduce secondary losses are discussed. Three vortexing methods presented are prismatic blade design, inverse vortex and parabolic forced vortex. Baseline industrial vane considered for study is a prismatic blade design. Modifications are analysed numerically using commercial code CFX. Modified vanes along with baseline rotor as a complete stage is considered for analysis. Steady state Reynolds averaged Navier Stokes equations are solved. Total pressure loss (TPL) is used as target functions to monitor reduction in secondary losses. Rotor considered for the study is the baseline industrial rotor for all design modifications of vane.
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| 9. |
- Glodic, Nenad, et al.
(författare)
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ARIAS project- Summary of project results
- 2023
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The present report contains the summary of project activities and main achievements of the ARIAS project. It starts with a brief overview of the project goals and objectives, breaking these down on a WP level. A description of each subtask in the work package with its specific objectives is included, providing the necessary background for the interpretation of the results. The main results and achievements of each project's tasks are thereafter highlighted.
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| 10. |
- Jonsson, Isak, 1990, et al.
(författare)
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Experimental and Numerical Study of Laminar-Turbulent Transition on a Low-Pressure Turbine Outlet Guide Vane
- 2020
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Ingår i: Proceedings of the ASME Turbo Expo. ; 2B
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Konferensbidrag (refereegranskat)abstract
- In modern commercial aviation engines, the low-pressure turbine (LPT) has a high outlet swirl to maximize turbine power to weight ratio. Downstream of the last LPT rotor is the turbine rear structure (TRS) that with relatively few low-aspect-ratio outlet guide vanes (OGV) de-swirls the flow to maximize the thrust. The performance of the TRS is strongly connected to secondary flow structures, which in turn are strongly influenced by the laminar-turbulent transition. Transition can be challenging to predict in turbomachinery due to the highly complex flow present. At the design point the TRS can have both by-pass transition and laminar separation with transition and a following turbulent reattachment. In addition, a TRS needs to perform well in a large off-design envelope, with large variations of the inlet swirl angle. Accurately predicting transition, both at the design point and in important off-design points, is critical for the development of future TRS modules. In modern geared and ultra-high by-pass engines the TRS swirl angle off-design requirements are also increasing. There are several available transition models in RANS simulations and most of them need parameter tuning when introduced to new conditions. Evaluation of these models for different turbomachinery components is relatively well covered in the literature even though the model specifics often is a classified property of engine manufacturers. However, there are no cases in the literature of transition prediction with experimental verification in the TRS at engine-realistic conditions. This work presents the first experimental verification of laminar-turbulent transition in a TRS module tested in the LPT-OGV experimental facility at Chalmers Laboratory of Thermal and Fluid Science. The facility is a semi-closed rig using a rotating 1.5 stage shrouded low-pressure turbine stage to create engine representative inlet conditions for the TRS downstream of the LPT stage. Transition was measured using differential IR-thermography (DIT) which is a non-intrusive two-dimensional measurement technique. The technique was specially developed at Chalmers for this particular purpose and validated by boundary layer hot-wire measurements. The numerical analysis was done using commercially available transition models in Fluent and Ansys CFX. Gamma-theta transition model was used with the k-omega SST turbulence model. Experiments and numerical simulations were performed at a chord Reynold number of 235000 and with LPT outlet swirl angles covering both the design point (ADP) and relevant off-design points. Numerical and experimental results show that agreement between transition models and experiments can be achieved at these conditions. Boundary layers on the pressure side and suction side undergo laminar-turbulent transition for the selected test range. At decreased OGV aerodynamic load, the boundary layer on the pressure side near the leading edge is laminar along most of the span. At higher OGV loads the secondary flow is influencing the region near the shroud on the pressure side as well as near the hub on the suction side. The transition on the suction side midspan is significantly influenced by the vane load. The numerical analysis was used to better understand the involved flow mechanisms.
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