Using CFD to Enhance the Preliminary Design of High-Pressure Steam Turbines

2013 ◽  
Author(s):  
Juri Bellucci ◽  
Federica Sazzini ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Lorenzo Arcangeli ◽  
...  
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Design Tool ◽  
Tip Clearance ◽  
Large Set ◽  
Preliminary Design ◽  
Steam Turbines ◽  
High Pressure Steam ◽  
Wide Range ◽  
Pressure Steam

This paper focuses on the use of the CFD for improving a steam turbine preliminary design tool. Three-dimensional RANS analyses were carried out in order to independently investigate the effects of profile, secondary flow and tip clearance losses, on the efficiency of two high-pressure steam turbine stages. The parametric study included geometrical features such as stagger angle, aspect ratio and radius ratio, and was conducted for a wide range of flow coefficients to cover the whole operating envelope. The results are reported in terms of stage performance curves, enthalpy loss coefficients and span-wise distribution of the blade-to-blade exit angles. A detailed discussion of these results is provided in order to highlight the different aerodynamic behavior of the two geometries. Once the analysis was concluded, the tuning of a preliminary steam turbine design tool was carried out, based on a correlative approach. Due to the lack of a large set of experimental data, the information obtained from the post-processing of the CFD computations were applied to update the current correlations, in order to improve the accuracy of the efficiency evaluation for both stages. Finally, the predictions of the tuned preliminary design tool were compared with the results of the CFD computations, in terms of stage efficiency, in a broad range of flow coefficients and in different real machine layouts.

Optimization of a High-Pressure Steam Turbine Stage for a Wide Flow Coefficient Range

2012 ◽  
Author(s):  
Juri Bellucci ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Lorenzo Arcangeli ◽  
Nicola Maceli ◽  
...  
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Low Flow ◽  
Turbine Stage ◽  
Aerodynamic Optimization ◽  
High Pressure Steam ◽  
Wide Range ◽  
Pressure Steam

In this paper a multi-objective, aerodynamic optimization of a high-pressure steam turbine stage is presented. The overall optimization strategy relies on a neural-network-based approach, aimed at maximizing the stage’s efficiency, while at the same time increasing the stage loading. The stage under investigation is composed of prismatic blades, usually employed in a repeating stage environment and in a wide range of operating conditions. For this reason, two different optimizations are carried out, at high and low flow coefficients. The optimized geometries are chosen taking into account aerodynamic constraints, such as limitation of the pressure recovery in the uncovered part of the suction side, as well as mechanical constraints, such as root tensile stress and dynamic behavior. As a result, an optimum airfoil is selected and its performance are characterized over the whole range of operating conditions. Parallel to the numerical activity, both optimized and original geometries are tested in a linear cascade, and experimental results are available for comparison purposes in terms of loading distributions and loss coefficients. Comparisons between measurements and calculations are presented and discussed for a number of incidence angles and expansion ratios.

Aerodynamic Flutter of Turbine Brush Seals

2017 ◽  
Author(s):  
Samuel J. Borgueta ◽  
Nicholas R. Bach ◽  
Jared J. Correia ◽  
Brendan G. J. Egan ◽  
Joshua S. Horton ◽  
...  
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Steam Turbines ◽  
High Pressure Steam ◽  
Modes Of Failure ◽  
Brush Seal ◽  
Pressure Steam ◽  
Brush Seals

With global energy demands continually growing and environmental impacts a major concern in power production, maximizing the efficiencies of power plants is of top priority. EthosEnergy2 has sponsored a project at the University of Massachusetts Dartmouth to study and analyze the brush seals in steam turbines in pursuit of increasing steam turbine thermodynamic efficiency. Brush seals are incorporated circumferentially around the turbine blades in their housing. The brush seals provide a very minimal clearance height that compensates for start-up rotor deviation and minimizes high-pressure steam blow-by around the edges of the blades. Brush seals minimize the clearance height between the blades and housing, which allows the turbine to produce more work. However, overtime brush seals can be damaged, greatly reducing efficiency. The seals that are repeatedly showing excessive wear and damage, occur in the high-pressure sections of steam turbines with high Reynolds numbers. The bristle breakdown is attributed to high Reynolds numbers and aerodynamic flutter. The purpose of this research is to design a prototype and empirically model steam turbine conditions with air to map out the fluid-solid interaction, determine the modes of bristle failure, and ultimately reproduce and record bristle flutter. A pressure vessel and pressure system was designed to test linear strips of brush seals with air as the working fluid. The pressure vessel accommodates varying clearance heights to identify the correlation of clearance height and the effects on fluid flow. The system also incorporates a high-speed camera that can capture the phenomena of flutter, precisely identify the modes of failure, and record fluid-solid interaction and the interaction of the bristles with each other. Designing a prototype to empirically model this problem serves as a fundamental and critical step in understanding the fluid interaction with seals in high-pressure steam turbines and will identify brush seal modes of failure. The prototype’s ability to model steam turbine conditions and rapidly test various seal designs will facilitate better brush seal designs to be constructed and will ultimately increase the thermal efficiencies of steam turbines, aid in accommodating the increase in global energy demands, and reduce the detrimental environmental impacts of producing power. The system successfully produced and recorded brush-seal-bristle flutter while modeling high-pressure steam turbine conditions. Matching Reynolds and Euler numbers of the steam turbine stages provided the ability to scale the steam turbine to our prototype, with air as the working fluid. Brush seal breakdown was occurring in steam turbines at Reynolds numbers above 20,000. The prototype repeatedly produced brush seal flutter at Reynolds numbers above 25,000, validating the theory that brush seal breakdown is dependent predominantly on the Reynolds number.

Creep Deformation of High Pressure Steam Turbine Part

2015 ◽  
Vol 732 ◽  
pp. 187-190
Author(s):  
František Straka ◽  
Pavel Albl ◽  
Pavel Pánek
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Steam Turbine ◽  
Creep Deformation ◽  
Steam Turbines ◽  
High Pressure Turbine ◽  
High Pressure Steam ◽  
Pressure Steam ◽  
Temperature Levels ◽  
Steam Parameters

Steam turbines are complex rotating machines working at high pressure and high temperature levels. Their high-pressure parts, which are subjected to the highest steam parameters, are most affected by these conditions and may suffer from creep deformation. Permanent changes in geometry become visible in high-pressure turbine casings when they are disassembled after certain time in operation.

CFD Investigation on the Rotordynamic Characteristics of Shroud Leakage Flow in High Pressure Steam Turbine

2013 ◽  
Author(s):  
Noriyo Nishijima ◽  
Akira Endo ◽  
Kazuyuki Yamaguchi
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Mass Flow ◽  
Guide Vane ◽  
Flow Distribution ◽  
Labyrinth Seal ◽  
High Pressure Steam ◽  
Cfd Models ◽  
Pressure Steam ◽  
The Difference

We conducted a computational fluid dynamics (CFD) study to investigate the rotordynamic characteristics of the shroud labyrinth seal of a high-pressure steam turbine. Four different CFD models were constructed to investigate the appropriate modeling approach for evaluating the seal force of an actual steam turbine because shroud seals are generally short with fewer fins and the effect of surrounding flow field is thought to be large. The four models are a full model consisting of a 1-stage stator/rotor cascade and a labyrinth seal over the rotor shroud, a guide-vane model to simulate the condition similar to seal element experiments, and two other simplified models. The calculated stiffness coefficients of the four models did not agree and fell into two groups. Through careful investigations of flow fields, it was found that the difference could be explained by the circumferential mass flow distribution at the seal inlet and the mass flow bias rate is an important factor in evaluating the seal force of a turbine shroud. The results also indicate that the rotordynamic characteristics obtained from seal element experiments may differ from those of actual turbines, especially in short seals.

Upgrades of Steam Turbine Generator Units in Watson Cogeneration Combined Cycle Plant

2002 ◽  
Author(s):  
Steve Ingistov
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Heat Rate ◽  
Combined Cycle ◽  
High Pressure Steam ◽  
Turbine Generators ◽  
Pressure Steam ◽  
Combined Cycle Plant ◽  
Path Modification ◽  
Sealing Elements

This paper describes efforts that were implemented in modifying two Steam Turbine Generators (STG) that are presently operating in Watson Cogeneration Company (WCC) Plant. WCC Plant is comprised of four identical GE made Gas Turbine Generators (GTG) and four Heat Recovery Steam Generators (HRSG) designed and fabricated by Vogt. Portion of high pressure steam is expanded inside two Dresser-Rand-made Steam Turbine Generators (STG). The modifications presented in this paper include replacement of six original stages of expansion, introduction of shaft retractable labyrinths/packing and installation of the spill strips around shrouded blades. The modifications of high pressure steam path (except 1st stage blading) were completed in 1992 and modification of rotor steam sealing elements such as shaft labyrinths were completed in April and May 2001. The steam path modification uprated STG from original 34.50MW to present 40MW each. The upgrades of the rotor sealing elements resulted in 2.80% Heat Rate (HR) reduction.

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