Last-Stage Blade Failure Evaluation

2007 ◽  
Author(s):  
Zdzislaw Mazur ◽  
Rafael Garci´a-Illescas ◽  
Jorge Aguirre-Romano ◽  
Norberto Pe´rez-Rodri´guez
Keyword(s):  
High Pressure ◽  
Turbine Blades ◽  
Low Pressure ◽  
Laboratory Evaluation ◽  
Metallographic Analysis ◽  
History Of ◽  
Last Stage ◽  
Blade Failure ◽  
Lp Turbine ◽  
Failure Evaluation

A last stage turbine blades failure was experienced in two units of 660 MW. These units have one high-pressure turbine and two tandem-compound low-pressure turbines with 44-inch last-stage blades. The blades that failed were in a low pressure (LP) turbine connected to the high pressure (HP) turbine (LP1) and in LP turbine connected to the generator (LP2). The failed blades had cracks in their roots initiating at the trailing edge, concave side of the steeple outermost fillet radius. Laboratory evaluation of the cracking indicates the failure mechanism to be high cycle fatigue (HCF). The last-stage blades failure evaluation was carried out. The investigation included a metallographic analysis of the cracked blades, natural frequency test and analysis, blade stress analysis, unit’s operation parameters and history of events analysis, fracture mechanics and crack propagation analysis. This paper provides an overview of this failure investigation, which led to the identification of the blades torsional vibrations near 120 Hz and some operation periods with low load low vacuum as the primary contribution to the observed failure.

L-0 Blades Failure Investigation of a 110 MW Geothermal Turbine

2006 ◽  
Author(s):  
Zdzislaw Mazur ◽  
Alejandro Herna´ndez-Rossette ◽  
Rafael Garci´a-Illesoas
Keyword(s):  
Turbine Blades ◽  
Laboratory Evaluation ◽  
Metallographic Analysis ◽  
Unstable Flow ◽  
Failure Investigation ◽  
Propagation Analysis ◽  
Last Stage ◽  
Lp Turbine ◽  
One Year ◽  
Natural Frequency Analysis

A last stage (L-0) turbine blades failure was experienced in a 110 MW geothermal unit after one year of operation period. This unit has two tandem-compound intermediate/low-pressure turbines (turbine A and turbine B) with 23-inch/3600 rpm last-stage blades. There were flexible blades continuously coupled 360 degrees around the row by loose cover segment at the tip and loose sleeve and lug at the mid-span (pre-twist design). The failed blades were in the L-0 row of the LP turbine B connected to the generator. The visual examination indicated that the group of 12 L-0 blades of rotor B on the generator side was bent and another group of 5 blades at 140 degrees from the first damaged group was also bent. The cover segments were spread out from the damaged blades and had cracks. Laboratory evaluation of the cracking in the cover segments indicates the failure mechanism to be high cycle fatigue (HCF), initiating at the cover segment holes outer fillet radius. The L-0 blades failure investigation was carried out. The investigation included a metallographic analysis of the cracked cover segments and bent blades, Finite Element Method (FEM) stress and natural frequency analysis (of blades/cover segments), fracture mechanics and crack propagation analysis. This paper provides an overview of the L-0 blades failure investigation, which led to the identification of the blades vibrations within the range 250 Hz to 588 Hz induced due to unstable flow excitation (stall flutter) as the primary contribution to the observed failure.

Improved µ-Scale Turbine Expander for Energy Recovery

2010 ◽  
Author(s):  
Marcus Keding ◽  
Piotr Dudzinski ◽  
Alexander Reissner ◽  
Stefan Hummel ◽  
Martin Tajmar
Keyword(s):  
High Pressure ◽  
Power Output ◽  
Energy Recovery ◽  
Turbine Blades ◽  
Low Pressure ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Work Recovery ◽  
Micro Power ◽  
Pressure Part

Micro power converters for energy recovery are increasingly important for a number of future applications. The Austrian Institute of Technology (AIT) is presently developing an innovative μ-scale turbine expander for work recovery in transcritical CO2 heat pumps. The main drawback of a lower COP (coefficient of performance) of transcritical CO2 heat pumps compared to conventional heat pump systems can be compensated by utilizing the pressure difference between the high pressure and low pressure part of the pump for work recovery. Work recovery can be realized by substituting the expansion valve between the high and low pressure side by a Pelton turbine with specific two phase flow turbine blades. In order to increase the power output, the generator was integrated into the turbine to reduce the friction losses and hence increase the overall efficiency. An important aspect is that the generator is directly connected with the high pressure part of the turbine. One part of the project is the optimization of the turbine geometry via simulation tools. The paper will give an overview about our microturbine development as well as a comparison of the power output of each turbine generation. Furthermore the present paper discusses a concept that utilizes our microturbine together with a micro combustion module that enables a micro power generator with very high power-to-weight ratios based on green fuels.

The Science, Technology, and Implementation of TiAl Alloys in Commercial Aircraft Engines

2013 ◽  
Vol 1516 ◽  
pp. 49-58 ◽  
Author(s):  
B. P. Bewlay ◽  
M. Weimer ◽  
T. Kelly ◽  
A. Suzuki ◽  
P.R. Subramanian
Keyword(s):  
Titanium Aluminide ◽  
Turbine Blades ◽  
Aircraft Engine ◽  
Low Pressure ◽  
Major Advance ◽  
Commercial Aircraft ◽  
Tial Alloys ◽  
Low Pressure Turbine ◽  
Titanium Aluminide Alloy ◽  
History Of

ABSTRACTThe present article will describe the science and technology of titanium aluminide (TiAl) alloys and the engineering development of TiAl for commercial aircraft engine applications. The GEnxTM engine is the first commercial aircraft engine that is flying titanium aluminide (alloy 4822) blades and it represents a major advance in propulsion efficiency, realizing a 20% reduction in fuel consumption, a 50% reduction in noise, and an 80% reduction in NOx emissions compared with prior engines in its class. The GEnxTM uses the latest materials and design processes to reduce weight, improve performance, and reduce maintenance costs.GE’s TiAl low-pressure turbine blade production status will be discussed along with the history of implementation. In 2006, GE began to explore near net shape casting as an alternative to the initial overstock conventional gravity casting plus machining approach. To date, more than 40,000 TiAl low-pressure turbine blades have been manufactured for the GEnxTM 1B (Boeing 787) and the GEnxTM 2B (Boeing 747-8) applications. The implementation of TiAl in other GE and non-GE engines will also be discussed.

Velocity Distributions for Low Pressure Turbines

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
J. D. Coull ◽  
R. L. Thomas ◽  
H. P. Hodson
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Laser Doppler Anemometry ◽  
Peak Velocity ◽  
Turbine Blades ◽  
Low Pressure ◽  
Number Range ◽  
Reduced Frequency ◽  
Unsteady Interaction ◽  
Lp Turbine

A parametric set of velocity distributions has been investigated using a flat-plate experiment. Three different diffusion factors and peak velocity locations were tested. These were designed to mimic the suction surfaces of low pressure (LP) turbine blades. Unsteady wakes, inherent in real turbomachinery flows, were generated using a moving bar mechanism. A turbulence grid generated a freestream turbulence level that is believed to be typical of LP turbines. Measurements were taken across a Reynolds number range 50,000–220,000 at three reduced frequencies (0.314, 0.628, and 0.942). Boundary layer traverses were performed at the nominal trailing edge using a laser Doppler anemometry system and hot films were used to examine the boundary layer behavior along the surface. For every velocity distribution tested, the boundary layer separated in the diffusing flow downstream of the peak velocity. The loss production is dominated by the mixing in the reattachment process, mixing in the turbulent boundary layer downstream of reattachment, and the effects of the unsteady interaction between the wakes and the boundary layer. A sensitive balance governs the optimal location of peak velocity on the surface. Moving the velocity peak forward on the blade was found to be increasingly beneficial when bubble-generated losses are high, i.e. at low Reynolds number, at low reduced frequency, and at high diffusion factors.

Loss reduction on ultra high lift low-pressure turbine blades using selective roughness and wake unsteadiness

2007 ◽  
Vol 111 (1118) ◽  
pp. 257-266 ◽  
Author(s):  
R. J. Howell ◽  
K. M. Roman
Keyword(s):  
Boundary Layer ◽  
Steady Flow ◽  
Separation Bubble ◽  
Turbine Blades ◽  
Low Pressure ◽  
Surface Boundary ◽  
Suction Surface ◽  
High Lift ◽  
Profile Losses ◽  
Lp Turbine

This paper describes how it is possible to reduce the profile losses on ultra high lift low pressure (LP) turbine blade profiles with the application of selected surface roughness and wake unsteadiness. Over the past several years, an understanding of wake interactions with the suction surface boundary layer on LP turbines has allowed the design of blades with ever increasing levels of lift. Under steady flow conditions, ultra high lift profiles would have large (and possibly open) separation bubbles present on the suction side which result from the very high diffusion levels. The separation bubble losses produced by it are reduced when unsteady wake flows are present. However, LP turbine blades have now reached a level of loading and diffusion where profile losses can no longer be controlled by wake unsteadiness alone. The ultra high lift profiles investigated here were created by attaching a flap to the trailing edge of another blade in a linear cascade — the so called flap-test technique. The experimental set-up used in this investigation allows for the simulation of upstream wakes by using a moving bar system. Hotwire and hotfilm measurements were used to obtain information about the boundary-layer state on the suction surface of the blade as it evolved in time. Measurements were taken at a Reynolds numbers ranging between 100,000 and 210,000. Two types of ultra high lift profile were investigated; ultra high lift and extended ultra high lift, where the latter has 25% greater back surface diffusion as well as a 12% increase in lift compared to the former. Results revealed that distributed roughness reduced the size of the separation bubble with steady flow. When wakes were present, the distributed roughness amplified disturbances in the boundary layer allowing for more rapid wake induced transition to take place, which tended to eliminate the separation bubble under the wake. The extended ultra high lift profile generated only slightly higher losses than the original ultra high lift profile, but more importantly it generated 12% greater lift.

The Deposition of Fog Droplets on Steam Turbine Blades by Turbulent Diffusion

1987 ◽  
Vol 109 (3) ◽  
pp. 429-435 ◽  
Author(s):  
K. K. Yau ◽  
J. B. Young
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Turbulent Diffusion ◽  
Turbine Blades ◽  
Low Pressure ◽  
Surface Velocity ◽  
Reliable Estimate ◽  
Surface Shear Stress ◽  
Blade Surface ◽  
Steam Turbine Blades

A theoretical approach for calculating the rate of deposition of fog droplets on steam turbine blades by turbulent diffusion is described. The theory is similar to that which has proved successful for predicting deposition of small particles in pipe flow and includes a recent correlation for the inertia-moderated regime. A reliable estimate of the blade surface shear stress distribution is required and is obtained by a quasi-three-dimensional inviscid flow calculation to give the blade surface velocity distribution, followed by a two-dimensional boundary layer calculation. The theory has been applied to two representative case studies. The first involves deposition on the final stage blading of the low-pressure cylinder of an operating 500 MW turbine, and the second concerns deposition in a high-pressure, wet steam turbine. Results are presented showing the effect of fog droplet size, surface roughness, and other flow parameters on the deposition rate. A comparison is made between the rates of deposition by diffusional and purely inertial mechanisms. In low-pressure turbines these are of comparable magnitude, but in high-pressure machines diffusional deposition may dominate.

The Effect of Rotor Casing on Low-Pressure Steam Turbine and Diffuser Interactions

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Gursharanjit Singh ◽  
Andrew P. S. Wheeler ◽  
Gurnam Singh
Keyword(s):  
Steam Turbine ◽  
Computational Study ◽  
Low Pressure ◽  
Computational Method ◽  
Test Facility ◽  
Leakage Flows ◽  
Flow Features ◽  
Last Stage ◽  
Lp Turbine ◽  
Tip Leakage Flows

The present study aims to investigate the interaction between a last-stage steam turbine blade row and diffuser. This work is carried out using computational fluid dynamics (CFD) simulations of a generic last-stage low-pressure (LP) turbine and axial–radial exhaust diffuser attached to it. In order to determine the validity of the computational method, the CFD predictions are first compared with data obtained from an experimental test facility. A computational study is then performed for different design configurations of the diffuser and rotor casing shapes. The study focuses on typical flow features such as effects of rotor tip leakage flows and subsequent changes in the rotor–diffuser interactions. The results suggest that the rotor casing shape influences the rotor work extraction capability and yields significant improvements in the diffuser static pressure recovery.

Nasalance and Nasality in Low Pressure and High Pressure Speech

1998 ◽  
Vol 35 (4) ◽  
pp. 293-298 ◽  
Author(s):  
Thomas Watterson ◽  
Kerry E. Lewis ◽  
Candace Deutsch
Keyword(s):  
High Pressure ◽  
Correlation Coefficient ◽  
Low Pressure ◽  
Communication Disorder ◽  
Test Sensitivity ◽  
Significant Difference ◽  
History Of ◽  
Hypernasal Speech ◽  
Test Specificity ◽  
The Mean

Objective This study compared nasalance measures and nasality ratings in low pressure (LP) and high pressure (HP) speech. Subjects The subjects for this study were 25 children ranging in age from 5 to 13 years. Twenty of the subjects were patients followed by a craniofacial team, and five had no history of communication disorder. Results The mean nasalance for the LP speech was 29.98% (SD, 16.16), and the mean nasalance for the HP speech was 30.28% (SD, 15.35). The mean nasality rating for the LP speech was 2.31, and the mean nasality rating for the HP speech was 2.59. Separate paired t tests revealed no significant difference between the LP or the HP speech for either the nasalance scores or the nasality ratings. The correlation coefficient between nasalance and nasality for the LP speech was r = 0.78, and for the HP speech r = 0.77. Using a cutoff of 26% for nasalance and 2.0 for nasality, Nasometer test sensitivity was 0.84 and test specificity was 0.88. Conclusions In general, clinicians may obtain valid measures of nasalance and/or ratings of nasality using either an LP stimulus or an HP stimulus. Sensitivity and specificity scores indicated that the Nasometer was reasonably accurate in distinguishing between normal and hypernasal speech samples.

Analyses of Temperature Distribution on Steam Turbine Last Stage Low Pressure Buckets at Low Flow Operations

2011 ◽  
Author(s):  
Victor Filippenko ◽  
Boris Frolov ◽  
Andrey Chernobrovkin ◽  
Bin Zhou ◽  
Amir Mujezinovic´ ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Fluid Dynamic ◽  
Low Pressure ◽  
Low Flow ◽  
Experimental Investigations ◽  
Temperature Prediction ◽  
Operation Conditions ◽  
Wide Range ◽  
Last Stage ◽  
Lp Turbine

Steam turbine power plant operations during start up and during operation at high exhaust pressure have the potential to result in an extremely low steam flow through the Low Pressure (LP) turbine. This inevitably leads to windage and results in significant temperature increases in the Last Stage Buckets (LSBs). High steam temperature can also initiate potential thermo-mechanical failure of the LSBs. Temperature prediction for a wide range of operational regimes imposes a significant challenge to modern LSB design. Extensive numerical and experimental investigations on an LP section steam turbine with LSBs of different lengths at typical low flow operation conditions have been conducted with the primary focus on LSB temperature prediction. A Low Pressure Development Turbine (LPDT) test rig was used to help develop and validate Computational Fluid Dynamic (CFD) based temperature prediction methodologies, which later were applied to predict operational temperatures for multiple LP section configurations under development. This article presents some important results of LPDT test measurements as well as CFD predictions of LP turbine flow structures and temperature distributions in last stage buckets.

scholarly journals Research on Water Droplet Movement Characteristics in the Last Two Stages of Low-Pressure Cylinder of Steam Turbine Under Low Load Conditions

2021 ◽  
Vol 9 ◽  
Author(s):  
Shuangshuang Fan ◽  
Ying Wang ◽  
Kun Yao ◽  
Yi Fan ◽  
Jie Wan ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Turbine Blades ◽  
Low Pressure ◽  
Water Droplets ◽  
Movement Characteristics ◽  
Low Load ◽  
Pressure Cylinder ◽  
Last Stage ◽  
Two Stages ◽  
Load Conditions

In the operating process of the coal-fired generation during flexible peaking regulation, the primary and secondary water droplets in the steam flowing through the last two stages of the low-pressure cylinder could influence the efficiency and safety of the steam turbine definitely. However, systematic analysis of the movement characteristics of water droplets under low-load conditions is scarcely in the existing research, especially the ultra-low load conditions below 30%. Toward this end, the more novel algebraic slip model and particle transport model mentioned in this paper are used to simulate the primary and secondary water droplets. Taking a 600 MW unit as a research object, the droplets motion characteristics of the last two stages were simulated within four load conditions, including 100, 50, 40, and 30% THA. The results show that the diameter of the primary water droplets is smaller, ranging from 0 to 1 µm, during the flexible peak regulation process of the steam turbine. The deposition is mainly located at the entire moving blades and the trailing edge of the last two stator blades. With the load decreasing, the deposition effect decreases sustainably. And the larger diameters of secondary water droplets range from 10 to 300 µm. The erosion of secondary water droplets in the last stage is more serious than that of the second last stage for different load conditions, and the erosion of the second last stage could be negligible. The pressure face and suction face at 30% blade height of the last stage blade have been eroded most seriously. The lower the load, the worse erosion from the secondary water droplets, which poses a potential threat to the fracture of the last stage blades of the steam turbine. This study provides a certain reference value for the optimal design of steam turbine blades under flexible peak regulation.

Sign in / Sign up

Export Citation Format

Share Document