Prevention of Cyclic Thermal-Stress Cracking in Steam-Turbine Rotors

1964 ◽  
Vol 86 (3) ◽  
pp. 361-367 ◽  
Author(s):  
W. R. Berry ◽  
Ivar Johnsson
Keyword(s):  
High Pressure ◽  
Thermal Stress ◽  
Steam Turbine ◽  
Outer Surface ◽  
Recent Experience ◽  
High Pressure Steam ◽  
Stress Cracking ◽  
Pressure Steam ◽  
Turbine Rotors ◽  
Stress Fatigue

Recent experience with cracking of the outer surface of load-cycled, high-pressure, steam-turbine rotors is analyzed as a thermal stress-fatigue problem. Cyclic strains are evaluated as a function of the operating transient and of the detailed rotor geometry. Operating recommendations are given with the aim of reducing the incidence of such cracking.

Experimental Research on Surface Temperature Measurement of Steam Turbine Rotors Based on IR Thermometry

2011 ◽  
Author(s):  
Fangming Lv ◽  
Kun Wang ◽  
Bo Wu ◽  
Shuhong Huang ◽  
Guoqiang He ◽  
...  
Keyword(s):  
High Pressure ◽  
Surface Temperature ◽  
Temperature Measurement ◽  
Steam Turbine ◽  
Temperature Measurements ◽  
Empirical Formulas ◽  
Surface Temperature Measurement ◽  
High Pressure Steam ◽  
Pressure Steam ◽  
Turbine Rotors

The surface temperature measurement of steam turbine rotors is of great importance to thermal stress monitoring and security evaluation. Traditionally, the temperature is calculated indirectly by empirical formulas with the vapors’ temperature measured by thermocouples. However, there is huge deviation among the results from different empirical formulas, and which may lead to inaccuracy that cannot be ignored to some extends. In this paper, the feasibility of surface temperature measurement of steam turbine rotors based on infrared radiation (IR) thermometry was discussed and verified experimentally considering the characteristics of the rotors (e.g. high speed rotation, vibration, high-temperature and high-pressure steam, and temperature variation). In the first experiment, the oxidation of alloy samples named refined 12%Cr steel was conducted in a high-pressure steam vessel, and the spectral emissivity of the samples were measured with a monochromatic pyrometer in 1.6μ m. The results shows that the compact oxidation film on the surface of samples had high emissivity, which fitted with a polynomial of third order to the temperature measurements. Then, in the second experiment, the monochromatic pyrometer was used to detect the surface temperature of metal, which was surrounded with high parameters steam(supercritical parameter: up to 25.7MPa and 395°C). The results indicate that the technology of infrared temperature measurement could be applied to the steam turbine rotors, and the deviation can be controlled under 5°C with appropriate infrared emissivity(e.g. assuming e = 0.85). At last, the uncertainty of the temperature measurements was discussed for further work.

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.

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.

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.

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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