A Redesign Strategy to Improve the Efficiency of a 17-Stage Steam Turbine

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
Filippo Rubechini ◽  
Andrea Schneider ◽  
Andrea Arnone ◽  
Stefano Cecchi ◽  
Francesco Malavasi
Keyword(s):  
Neural Network ◽  
Steam Turbine ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Second Step ◽  
Geometrical Transformation ◽  
First Approximation ◽  
Original Reference

A three-dimensional Reynolds averaged Navier–Stokes solver was applied to the aerodynamic redesigning of a 17-stage steam turbine. The redesign procedure was divided into three steps. In the first one, a single embedded stage was considered, and an optimization of stator lean and rotor twist was carried out by applying suitable repeating inlet/outlet boundary conditions. In the second step, a proper geometrical transformation between the original reference stage and the optimized one was identified and then applied to all other turbine stages, thus leading to a first approximation of the redesigned turbine. Finally, a neural-network-based refinement of the stator and rotor twist of each stage was performed to account for its actual position and operating conditions within the meridional channel. In this work, a detailed description of the redesign procedure is provided, and the aerodynamic characteristics of the optimized geometry are discussed and compared with the original ones.

A Redesign Strategy to Improve the Efficiency of a 17-Stage Steam Turbine

2009 ◽  
Author(s):  
Filippo Rubechini ◽  
Andrea Schneider ◽  
Andrea Arnone ◽  
Stefano Cecchi ◽  
Francesco Malavasi
Keyword(s):  
Neural Network ◽  
Boundary Conditions ◽  
Steam Turbine ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Second Step ◽  
Geometrical Transformation ◽  
First Approximation ◽  
Original Reference

A three-dimensional RANS solver was applied to the aerodynamic redesigning of a 17-stage steam turbine. The redesign procedure was divided into three steps. In the first one, a single embedded stage was considered, and an optimization of stator lean and rotor twist was carried out by applying suitable repeating inlet/outlet boundary conditions. In the second step, a proper geometrical transformation between the original reference stage and the optimized one was identified and then applied to all other turbine stages, thus leading to a first approximation of the redesigned turbine. Finally, a neural-network-based refinement of the stator and rotor twist of each stage was performed to account for its actual position and operating conditions within the meridional channel. In this work, a detailed description of the redesign procedure is provided, and the aerodynamic characteristics of the optimized geometry are discussed and compared to the original ones.

A Computational Analysis of Flow Field in Twin-Track Subway Tunnel to Improve Air Quality

2013 ◽  
Vol 319 ◽  
pp. 599-604
Author(s):  
Makhsuda Juraeva ◽  
Kyung Jin Ryu ◽  
Sang Hyun Jeong ◽  
Dong Joo Song
Keyword(s):  
Air Quality ◽  
Computational Model ◽  
Stokes Equations ◽  
Ventilation System ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Subway Tunnel ◽  
Air Supply ◽  
And Performance

A computational model of existing Seoul subway tunnelwas analyzed in this research. The computational model was comprised of one natural ventilationshaft, two mechanical ventilationshafts, one mechanical airsupply, a twin-track tunnel, and a train. Understanding the flow pattern of the train-induced airflow in the tunnel was necessary to improve ventilation performance. The research objective wasto improve the air quality in the tunnel by investigating train-induced airflow in the twin-track subway tunnel numerically. The numerical analysis characterized the aerodynamic behavior and performance of the ventilation system by solving three-dimensional turbulent Reynolds-averaged Navier-Stokes equations. ANSYS CFX software was used for the computations. The ventilation and aerodynamic characteristics in the tunnel were investigated by analyzing the mass flowrateat the exits of the ventilation mechanicalshafts. As the train passed the mechanical ventilation shafts, the amount of discharged-air in the ventilationshafts decreased rapidly. The air at the exits of the ventilation shafts was gradually recovered with time, after the train passed the ventilation shafts. The developed mechanical air-supply for discharging dusty air and supplying clean airwas investigated.The computational results showed that the developed mechanical air-supplycould improve the air quality in the tunnel.

scholarly journals Numerical Investigation on Flapping Aerodynamic Performance of Dragonfly Wings in Crosswind

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Chao Wang ◽  
Rui Zhang ◽  
Chaoying Zhou ◽  
Zhenzhong Sun
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Lateral Force ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Aerodynamic Forces ◽  
Sideslip Angle ◽  
Flight Direction ◽  
Time Average ◽  
Dragonfly Wings

Numerical simulations are performed to investigate the influence of crosswind on the aerodynamic characteristics of rigid dragonfly-like flapping wings through the solution of the three-dimensional unsteady Navier-Stokes equations. The aerodynamic forces, the moments, and the flow structures of four dragonfly wings are examined when the sideslip angle ϑ between the crosswind and the flight direction varied from 0o to 90o. The stability of the dragonfly model in crosswind is analyzed. The results show that the sideslip angle ϑ has a little effect on the total time-average lift force but significant influence on the total time-average thrust force, lateral force, and three-direction torques. An increase in the sideslip angle gives rise to a larger total time-average lateral force and yaw moment. These may accelerate the lateral skewing of the dragonfly, and the increased rolling and pitching moments will further aggravate the instability of the dragonfly model. The vorticities and reattached flow on the wings move laterally to one side due to the crosswind, and the pressure on wing surfaces is no longer symmetrical and hence, the balance between the aerodynamic forces of the wings on two sides is broken. The effects of the sideslip angle ϑ on each dragonfly wing are different, e.g., ϑ has a greater effect on the aerodynamic forces of the hind wings than those of the fore wings. When sensing a crosswind, it is optimal to control the two hind wings of the bionic dragonfly-like micro aerial vehicles.

Some Aspects of CFD Modeling in the Analysis of a Low-Pressure Steam Turbine

2007 ◽  
Author(s):  
Filippo Rubechini ◽  
Michele Marconcini ◽  
Andrea Arnone ◽  
Stefano Cecchi ◽  
Federico Dacca`
Keyword(s):  
Steam Turbine ◽  
Computational Cost ◽  
Three Dimensional ◽  
Low Pressure ◽  
Design Tool ◽  
Cfd Modeling ◽  
Navier Stokes ◽  
Sources And Sinks ◽  
Leakage Flows ◽  
Pressure Steam

A three-dimensional, multistage, Navier-Stokes solver is applied to the numerical investigation of a four stage low-pressure steam turbine. The thermodynamic behavior of the wet steam is reproduced by adopting a real-gas model, based on the use of gas property tables. Geometrical features and flow-path details consistent with the actual turbine geometry, such as cavity purge flows, shroud leakage flows and partspan snubbers, are accounted for, and their impact on the turbine performance is discussed. These details are included in the analysis using simple models, which prevent a considerable growth of the computational cost and make the overall procedure attractive as a design tool for industrial purposes. Shroud leakage flows are modeled by means of suitable endwall boundary conditions, based on coupled sources and sinks, while body forces are applied to simulate the presence of the damping wires on the blades. In this work a detailed description of these models is provided, and the results of computations are compared with experimental measurements.

Three-Dimensional Flowfields Inside a Transonic Compressor With Swept Blades

1991 ◽  
Vol 113 (2) ◽  
pp. 241-250 ◽  
Author(s):  
C. Hah ◽  
A. J. Wennerstrom
Keyword(s):  
Turbulence Modeling ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Improved Performance

The concept of swept blades for a transonic or supersonic compressor was reconsidered by Wennerstrom in the early 1980s. Several transonic rotors designed with swept blades have shown very good aerodynamic efficiency. The improved performance of the rotor is believed to be due to reduced shock strength near the shroud and better distribution of secondary flows. A three-dimensional flowfield inside a transonic rotor with swept blades is analyzed in detail experimentally and numerically. A Reynolds-averaged Navier–Stokes equation is solved for the flow inside the rotor. The numerical solution is based on a high-order upwinding relaxation scheme, and a two-equation turbulence model with a low Reynolds number modification is used for the turbulence modeling. To predict flows near the shroud properly, the tip-clearance flow also must be properly calculated. The numerical results at three different operating conditions agree well with the available experimental data and reveal various interesting aspects of shock structure inside the rotor.

scholarly journals Darmstadt Rotor No. 2, II: Design of Leaning Rotor Blades

2003 ◽  
Vol 9 (6) ◽  
pp. 385-391
Author(s):  
Jörg Bergner ◽  
Dietmar K. Hennecke ◽  
Martin Hoeger ◽  
Karl Engel
Keyword(s):  
Mechanical Stability ◽  
Three Dimensional ◽  
Stability Limit ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Structural Constraints ◽  
Transonic Compressor ◽  
Aero Engines ◽  
The Impact

For Darmstadt University of Technology's axial singlestage transonic compressor rig, a new three-dimensional aft-swept rotor was designed and manufactured at MTU Aero Engines in Munich, Germany. The application of carbon fiber–reinforced plastic made it possible to overcome structural constraints and therefore to further increase the amount of lean and sweep of the blade. The aim of the design was to improve the mechanical stability at operation that is close to stall.To avoid the hazard of rubbing at the blade tip, which is found especially at off-design operating conditions close to the stability limit of the compression system, aft-sweep was introduced together with excessive backward lean.This article reports an investigation of the impact of various amounts of lean on the aerodynamic behavior of the compressor stage on the basis of steady-state Navier-Stokes simulations. The results indicate that high backward lean promotes an undesirable redistribution of mass flow and gives rise to a basic change in the shock pattern, whereas a forward-leaning geometry results in the development of a highly back-swept shock front. However, the disadvantage is a decrease in shock strength and efficiency.

Experimental and Numerical Investigation of Stator Exit Flow Field of an Automotive Torque Converter

1996 ◽  
Vol 118 (4) ◽  
pp. 835-843 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana ◽  
Y. Dong
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Complex Flow ◽  
Rate Of Decay

The objective of this investigation is to understand the nature of the complex flow field inside each element of the torque converter through a systematic experimental and numerical investigation of the flow field. A miniature five-hole probe was used to acquire the data at the exit of the stator at several operating conditions. The flow field is found to be highly three dimensional with substantial flow deviations, and secondary flow at the exit of the stator. The secondary flow structure, caused by the upstream radial variation of the through flow, induces flow overturning near the core. Flow separation near the shell causes flow underturning in this region. The rate of decay of stator wake is found to be slower than that observed in the wakes of axial flow turbine nozzles. The flow predictions by a Navier–Stokes code are in good agreement with the pressure and the flow field measured at the exit of the stator at the design and the off-design conditions.

Numerical Characterisation of Jet-Vane based Thrust Vector Control Systems

2015 ◽  
Vol 65 (4) ◽  
pp. 261 ◽  
Author(s):  
M.S.R. Chandra Murthy ◽  
Debasis Chakraborty
Keyword(s):  
Vector Control ◽  
Control Systems ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Static Tests ◽  
Thrust Vector Control ◽  
Thrust Vector

<p>Computational fluid dynamics methodology was used in characterising jet vane based thrust vector control systems of tactical missiles. Three-dimensional Reynolds Averaged Navier-Stokes equations were solved along with two-equation turbulence model for different operating conditions. Nonlinear regression analysis was applied to the detailed CFD database to evolve a mathematical model for the thrust vector control system. The developed model was validated with series of ground based 6-Component static tests. The proven methodology is applied toa new configuration.</p><p><strong>Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 261-264, DOI: http://dx.doi.org/10.14429/dsj.65.7960</strong></p>

scholarly journals Three-Dimensional Flowfields Inside a Transonic Compressor With Swept Blades

1990 ◽  
Author(s):  
C. Hah ◽  
A. J. Wennerstrom
Keyword(s):  
Turbulence Modeling ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Improved Performance

The concept of swept blades for a transonic or supersonic compressor was reconsidered by Wennerstrom in the early 1980s. Several transonic rotors designed with swept blades have shown very good aerodynamic efficiency. The improved performance of the rotor is believed to be due to reduced shock strength near the shroud and better distribution of secondary flows. A three-dimensional flowfield inside a transonic rotor with swept blades is analyzed in detail experimentally and numerically. A Reynolds-averaged Navier-Stokes equation is solved for the flow inside the rotor. The numerical solution is based on a high-order upwinding relaxation scheme, and a two-equation turbulence model with a low Reynolds number modification is used for the turbulence modeling. To properly predict flows near the shroud, the tip-clearance flow also must be properly calculated. The numerical results at three different operating conditions agree well with the available experimental data and reveal various interesting aspects of shock structure inside the rotor.

scholarly journals Effect of Blade Profiles on the performance of Bidirectional Wave Energy Turbine

2018 ◽  
Vol 172 ◽  
pp. 06002
Author(s):  
P.Madhan Kumar ◽  
Abdus Samad
Keyword(s):  
Wave Energy ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Wells Turbine ◽  
Reference Case ◽  
Navier Stokes Equation ◽  
World Energy ◽  
Entrapped Air ◽  
Experimental Values

To fulfill the ever growing demands of world energy consumption, the wave energy should be extracted economically. The oscillating water column is most commonly used to xtract energy from waves. It consists of a chamber in which waves drives the entrapped air column to rotate the Wells turbine. The Wells turbine is a self-rectifying low-pressure axial reaction turbine with 90ο stagger angle. These turbines consist of symmetrical airfoil profile to achieve unidirectional rotation for the bi-directional airflow. The turbine performance predominantly depends on the aerodynamic characteristics of the airfoil profile used. In this study, the performance of Wells turbine with various symmetrical airfoil profiles was analysed using ANSYS CFX 14.5. The CFD analysis was performed by solving three dimensional steady Reynolds averaged Navier-Stokes equation with k-ω SST turbulence closure model. The reference geometry has NACA0015 as blade profile and the CFD results were compared with the experimental values. The performance characteristics of the new airfoil profiles were compared with the reference case to analyse the suitability of airfoils in wave energy extraction. The NACA0021 airfoil profile showed better performance in the post-stall regime compared to the NACA0015 and the S1046 airfoil profiles.

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