Using Improved Remote Visual Inspection Tools to Reach Intermediate Stages in Turbomachinery

2004 ◽  
Author(s):  
Christopher P. Brown ◽  
David B. Smith
Keyword(s):  
Visual Inspection ◽  
Axial Direction ◽  
Low Pressure ◽  
Vibration Monitoring ◽  
Steam Turbines ◽  
Foreign Object Damage ◽  
Low Pressure Turbine ◽  
Rotor Imbalance ◽  
Conventional Technology ◽  
Two Stages

Using conventional technology, only the outer stages (the first stage and the last one or two stages) of industrial steam turbines are generally accessible to visual inspection. Signs of problems such as erosion, or native or foreign object damage in the intermediate stages can only be detected by other diagnostic means, such as vibration monitoring. This deficiency can make turbine diagnosis difficult in some circumstances. A remote visual inspection technology that can penetrate to the intermediate stages through access from the first or last stages would provide more complete visual coverage. In a recent inspection of a large cross-compound steam turbine at Detroit Edison’s St. Clair Power Plant, new minimally invasive inspection tools were used to locate the cause of rotor imbalance in the low pressure turbine. Attempts to find the problem using conventional borescopes had failed — they could not be inserted far enough into the intermediate stages to locate the problem. Using the modified inspection tools, a missing shroud band segment was discovered on the L-3 stage of the low pressure turbine. Conventional tools had been unable to reach further than the L-1 stage. The new tools, featuring stiffness in the axial direction and flexibility in the radial direction, were maneuvered through ten stages of turbomachinery and were used to locate the problem and evaluate collateral damage to other turbine stages.

Sequential vs Multidisciplinary Coupled Optimization and Efficient Surrogate Modelling of a Last Stage and the Successive Axial Radial Diffuser in a Low Pressure Steam Turbine

2014 ◽  
Author(s):  
Kevin Cremanns ◽  
Dirk Roos ◽  
Arne Graßmann
Keyword(s):  
Steam Turbine ◽  
Design Process ◽  
Energy Demand ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Low Pressure ◽  
Steam Turbines ◽  
Low Pressure Turbine ◽  
Pressure Steam ◽  
Last Stage

In order to meet the requirements of rising energy demand, one goal in the design process of modern steam turbines is to achieve high efficiencies. A major gain in efficiency is expected from the optimization of the last stage and the subsequent diffuser of a low pressure turbine (LP). The aim of such optimization is to minimize the losses due to separations or inefficient blade or diffuser design. In the usual design process, as is state of the art in the industry, the last stage of the LP and the diffuser is designed and optimized sequentially. The potential physical coupling effects are not considered. Therefore the aim of this paper is to perform both a sequential and coupled optimization of a low pressure steam turbine followed by an axial radial diffuser and subsequently to compare results. In addition to the flow simulation, mechanical and modal analysis is also carried out in order to satisfy the constraints regarding the natural frequencies and stresses. This permits the use of a meta-model, which allows very time efficient three dimensional (3D) calculations to account for all flow field effects.

An Experimental Investigation of the Influence of Flash-Back Flow on Last Three Stages of Low Pressure Steam Turbines

2014 ◽  
Author(s):  
Naoki Shibukawa ◽  
Yoshifumi Iwasaki ◽  
Yoshiaki Takada ◽  
Itaru Murakami ◽  
Takashi Suzuki ◽  
...  
Keyword(s):  
Reverse Flow ◽  
Flow Region ◽  
Low Pressure ◽  
Detailed Examination ◽  
Steam Turbines ◽  
Back Flow ◽  
Large Size ◽  
Vibration Stress ◽  
Last Stage ◽  
Two Stages

A shutdown operation of a large size steam turbine could possibly cause flashing phenomena of the pooled drain water in low-pressure heaters. The boiled steam is sometimes in the same amount as the main flow in the case where shutdown is executed during low load conditions, and returns to the steam flow path through the extraction lines. A series of experimental work with a subscale model turbine facility has been carried out to investigate the vibration stress behavior, and the steady and unsteady pressures under the flashing back conditions. It was observed that the blades of the two stages before the last stage (L-2) and a stage before the last stage (L-1) presented their peak vibration stresses immediately after the flash-back flow reached the turbine. In the meantime, the vibration stresses of the last stage (L-0) blades were reduced for a few tens of seconds. It can be thought that the flash-back flow pushed out the reverse flow region around the L-0 blades and allow the blades to be more stable. A detailed examination with measured data of the L-2 blade explained that, as long as the flash-back flow has small wetness, the blade is excited in its specific vibration modes in larger than 8th harmonic of rotational speed, but once the flash back flow carries water droplets, the fluid force in random frequencies remarkably increases and excites the blade in less than 7th harmonic range.

An Experimental Investigation of the Influence of Flash-Back Flow on Last Three Stages of Low Pressure Steam Turbines

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Naoki Shibukawa ◽  
Takao Fukushima ◽  
Yoshifumi Iwasaki ◽  
Yoshiaki Takada ◽  
Itaru Murakami ◽  
...  
Keyword(s):  
Reverse Flow ◽  
Flow Region ◽  
Low Pressure ◽  
Detailed Examination ◽  
Steam Turbines ◽  
Back Flow ◽  
Large Size ◽  
Vibration Stress ◽  
Last Stage ◽  
Two Stages

A shutdown operation of a large size steam turbine could possibly cause flashing phenomena of the pooled drain water in low-pressure heaters. The boiled steam is sometimes in the same amount as the main flow in the case where shutdown is executed during low load conditions, and returns to the steam flow path through the extraction lines. A series of experimental work with a subscale model turbine facility has been carried out to investigate the vibration stress behavior, and the steady and unsteady pressures under the flashing back (FB) conditions. It was observed that the blades of the two stages before the last stage (L-2) and a stage before the last stage (L-1) presented their peak vibration stresses immediately after the flash-back flow reached the turbine. In the meantime, the vibration stresses of the last stage (L-0) blades were reduced for a few tens of seconds. It can be thought that the flash-back flow pushed out the reverse flow region around the L-0 blades and allow the blades to be more stable. A detailed examination with measured data of the L-2 blade explained that, as long as the flash-back flow has small wetness, the blade is excited in its specific vibration modes in larger than eighth harmonic of rotational speed, but once the flash-back flow carries water droplets, the fluid force in random frequencies remarkably increases and excites the blade in less than seventh harmonic range.

scholarly journals New two-tier low pressure turbine for heavy duty steam turbines

2017 ◽  
Vol 891 ◽  
pp. 012257 ◽  
Author(s):  
A E Zaryankin ◽  
A N Rogalev ◽  
S K Osipov ◽  
N M Bychkov
Keyword(s):  
Low Pressure ◽  
Steam Turbines ◽  
Heavy Duty ◽  
Low Pressure Turbine

Unsteady Wet-Steam Flows Through Low Pressure Turbine Final Three Stages Considering Blade Number

2015 ◽  
Author(s):  
Satoshi Miyake ◽  
Hironori Miyazawa ◽  
Satoru Yamamoto ◽  
Yasuhiro Sasao ◽  
Kazuhiro Momma ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Low Pressure ◽  
Numerical Results ◽  
Steam Turbines ◽  
Wet Steam ◽  
Flow Simulations ◽  
Low Pressure Turbine ◽  
Blade Number ◽  
Pressure Steam ◽  
Three Stages

Unsteady three-dimensional wet-steam flows through stator–rotor blade rows in the final three stages of a low-pressure steam turbine, taking the blade number into consideration, are numerically investigated. In ASME Turbo Expo 2014, we presented the numerical results of the unsteady flow assuming the same blade number. Here, this previous study is extended to flow simulations using the real blade number. The flows under three flow conditions, with and without condensation and considering the same and real blade numbers are simulated, and the numerical results are compared with each other and with the experimental results. Finally, the effect of the blade number on unsteady wet-steam flows in real low-pressure steam turbines is discussed.

Nonequilibrium Throughflow Analyses of Low-Pressure, Wet Steam Turbines

1984 ◽  
Vol 106 (4) ◽  
pp. 716-724 ◽  
Author(s):  
C. C. Yeoh ◽  
J. B. Young
Keyword(s):  
Low Pressure ◽  
Computational Method ◽  
Virial Equation ◽  
Complete Analysis ◽  
Steam Turbines ◽  
Wet Steam ◽  
Streamline Curvature ◽  
Low Pressure Turbine ◽  
Aerodynamic Parameters ◽  
Theoretical Test

The paper describes a throughflow computational method that combines wet steam theory with an axisymmetric streamline curvature technique in order to predict nonequilibrium effects in low-pressure steam turbines. The computer program developed is able to deal with both subsonic and fully choked supersonic flows, and steam properties are represented by a truncated virial equation of state. A number of theoretical test cases have been investigated, including the nonequilibrium flow in the primary nucleating stage of a low-pressure turbine and the complete analysis of a six-stage, 320-MW operational turbine. The calculations are the first of their kind in being able to provide information on the spanwise variation of the Wilson point, the average droplet size nucleated, the degree of supercooling throughout the flowfield, the thermodynamic wetness loss, and the nonequilibrium choking mass flow rate in addition to the aerodynamic parameters which are of interest to the designer.

Three-Dimensional Blade Stacking Strategies and Understanding of Flow Physics in Low-Pressure Steam Turbines—Part II: Stacking Equivalence and Differentiators

2015 ◽  
Vol 138 (6) ◽  
Author(s):  
Said Havakechian ◽  
John Denton
Keyword(s):  
Guide Vane ◽  
Three Dimensional ◽  
Low Pressure ◽  
Cfd Modeling ◽  
Steam Turbines ◽  
Flow Parameters ◽  
Pressure Steam ◽  
Computational Fluid Dynamics Cfd ◽  
Last Stage ◽  
Two Stages

Optimization of blade stacking in low-pressure (LP) steam turbine development constitutes one of the most delicate and time-consuming parts of the design process. This is the second part of two papers focusing on stacking strategies applied to the last stage guide vane and represents an attempt to discern the aerodynamic targets that can be achieved by each of the well-known and most often used basic stacking schemes. The effects of lean and twist have been investigated through an iterative process, involving comprehensive 3D computational fluid dynamics (CFD) modeling of the last two stages of a standard LP, where the basic lean and twist stacking schemes were applied on the last stage guide vanes while keeping the throat area (TA) unchanged. It has been found that it is possible to achieve the same target value and pattern of stage reaction by applying either tangential lean or an equivalent value of twist. Moreover, the significance of axial sweep on hub reaction has been found to become pronounced when the blade sweep is carried out at constant TA. The importance of hub-profiling has also been demonstrated and assessed. Detailed analysis of the flow fields has provided an overall picture, revealing the differences in the main flow parameters as produced by each of the alternative basic stacking schemes.

scholarly journals The applicability of two-tier low pressure turbine in high-power condensing steam turbines

2018 ◽  
Author(s):  
Zaryankin Arkadiy ◽  
Osipov Sergey ◽  
Krutitskii Vladislav
Keyword(s):  
High Power ◽  
Low Pressure ◽  
Steam Turbines ◽  
Low Pressure Turbine

Development of a model for thin films and numerical sensitivity tests

2018 ◽  
Vol 232 (5) ◽  
pp. 525-535 ◽  
Author(s):  
Amélie Simon ◽  
Jean-Marc Dorey ◽  
Michel Lance
Keyword(s):  
Surface Tension ◽  
Shear Stress ◽  
Thin Liquid Film ◽  
Low Pressure ◽  
Liquid Films ◽  
Steam Turbines ◽  
Low Pressure Turbine ◽  
Plane Plate ◽  
Dimensional Version ◽  
The Waves

Because the unsteady behavior of liquid films in steam turbines is a key point for additional friction losses and atomization process (that leads to coarse water generation), the development of a dedicated model has been found necessary. A two-dimensional computational fluid dynamics code for unstructured mesh is being developed using the finite volume method to simulate this thin liquid film. The aim is to predict the formation of the waves in the film since it is suspected to be a key parameter for friction and atomization. Applied as a first step to a plane plate, the code has been verified in a one-dimensional version with analytical solutions and is tested in low-pressure turbine steam conditions. Falling films computations (without gas shear stress) show that the model is capable to reproduce the waves’ shape of experiments from the literature. With steam under low-pressure turbine conditions, and compared to experimental data from the University of Michigan, the model including shear stress and surface tension provides good results for heights. Sensitivity calculations have been undergone showing the crucial influence of the surface tension and the generation of solitary waves for high velocities is captured by the code. The effect of gravity is also quantified.

Designing a High Fidelity Wake Simulator for Research Using Linear Cascades

2009 ◽  
Author(s):  
Jonathon Pluim ◽  
Curtis Memory ◽  
Jeffrey Bons ◽  
Jen-Ping Chen
Keyword(s):  
Turbine Blade ◽  
Cross Sections ◽  
Bluff Body ◽  
Axial Direction ◽  
Low Pressure ◽  
Shear Stresses ◽  
Bluff Bodies ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Experimental Findings

Owing to the extensive use of wake generators in the study of turbine and compressor airfoils in linear cascades, a study was undertaken to determine the most accurate model for the wakes generated by upstream blade rows. Velocity (PIV) measurements were taken to compare wake properties of several bluff bodies with different cross sections to the wake of an ultra high lift low pressure turbine profile. These measurements were taken at two Reynolds numbers, a low and a high one to simulate a separated and attached wake, respectively, for both the blade and two of the shape configurations. The L1A turbine blade profile was determined to shed a wake typical of high lift turbine blade profiles. It is shown that the wake of the turbine blade is highly dependent on Reynolds number. In order to make an appropriate comparison, all bluff body data were extracted along a plane parallel to the equivalent inlet plane of a rotor stage in the stationary frame of reference. It was found that no single rod shape matched all of the blade wake characteristics. From among the shapes used in this study, a 30° isosceles wedge placed 6 diameters upstream of the cascade inlet in the axial direction and skewed 15° from the rod relative flow was found to yield the closest match for the low Re case due to the asymmetry in the velocity and Reynolds shear stresses in this wake compared with the wake of the low pressure turbine blade. The same configuration placed 10 diameters upstream yielded the best comparison to a higher Re, more attached L1A wake. Large Eddy Simulations of various shapes largely corroborate the experimental findings.

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