Investigation Into a “Steam Whirl” Which Affected HP Rotors of 300 MW Steam Turbines

2007 ◽  
Author(s):  
Janusz Kubiak Sz. ◽  
Dara Childs ◽  
M. Rodri`guez ◽  
J. C. Garci´a
Keyword(s):  
Steam Turbine ◽  
The Other ◽  
Steam Turbines ◽  
Full Load ◽  
The Past ◽  
Instability Effect ◽  
Valve Opening ◽  
Rotordynamic Forces ◽  
Rotor Model ◽  
Load Conditions

In the past, several 300 MW steam turbine rotors were affected by vibrations, which appeared at bearing #1 during load conditions. At certain loads, vibrations of the #1 bearing increased considerably. Near full load the amplitude of vibration sometimes reduced to acceptable levels. Practically, the phenomena were partially cured by trim balancing of the HP rotor, readjusting the valve opening characteristics and by correction of the clearances in the sealing system. The results are briefly summarized. On the other hand, the simulation of the various parameters using rotordynamic codes was conducted to explain the phenomena analytically. In this part, the rotordynamic rotor model was constructed and the following simulations were carried out: rotor bearing instability, effect of the destabilizing steam forces on the rotor at the first row, effect of the seal rotordynamic forces and the valve opening sequence on the rotor stability. All results were analyzed to present general conclusions.

The Effect of Stage-Diffuser Interaction on the Aerodynamic Performance and Design of LP Steam Turbine Exhaust Systems

2018 ◽  
Author(s):  
Bowen Ding ◽  
Liping Xu ◽  
Jiandao Yang ◽  
Rui Yang ◽  
Yuejin Dai
Keyword(s):  
Steam Turbine ◽  
Renewable Energy Sources ◽  
Rotor Blades ◽  
Steam Turbines ◽  
Flow Conditions ◽  
Part Load ◽  
Last Stage ◽  
Load Conditions ◽  
Turbine Exhaust ◽  
Exhaust Systems

Modern large steam turbines for power generation are required to operate much more flexibly than ever before, due to the increasing use of intermittent renewable energy sources such as solar and wind. This has posed great challenges to the design of LP steam turbine exhaust systems, which are critical to recovering the leaving energy that is otherwise lost. In previous studies, the design had been focused on the exhaust diffuser with or without the collector. Although the interaction between the last stage and the exhaust hood has been identified for a long time, little attention has been paid to the last stage blading in the exhaust system’s design process, when the machine frequently operates at part-load conditions. This study focuses on the design of LP exhaust systems considering both the last stage and the exhaust diffuser, over a wide operating range. A 1/10th scale air test rig was built to validate the CFD tool for flow conditions representative of an actual machine at part-load conditions, characterised by highly swirling flows entering the diffuser. A numerical parametric study was performed to investigate the effect of both the diffuser geometry variation and restaggering the last stage rotor blades. Restaggering the rotor blades was found to be an effective way to control the level of leaving energy, as well as the flow conditions at the diffuser inlet, which influence the diffuser’s capability to recover the leaving energy. The benefits from diffuser resizing and rotor blade restaggering were shown to be relatively independent of each other, which suggests the two components can be designed separately. Last, the potentials of performance improvement by considering both the last stage rotor restaggering and the diffuser resizing were demonstrated by an exemplary design, which predicted an increase in the last stage power output of at least 1.5% for a typical 1000MW plant that mostly operates at part-load conditions.

Suppression of Subsynchronous Vibrations in a 11 MW Steam Turbine Using Integral Squeeze Film Damper Technology at the Exhaust Side Bearing

2016 ◽  
Author(s):  
Riccardo Ferraro ◽  
Michael Catanzaro ◽  
Jongsoo Kim ◽  
Michela Massini ◽  
Davide Betti ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Labyrinth Seal ◽  
Squeeze Film ◽  
Stable Operation ◽  
Steam Turbines ◽  
Squeeze Film Damper ◽  
Full Load ◽  
Steam Admission ◽  
Before And After ◽  
Full Speed

The presence of high subsynchronous vibrations and other rotordynamic instabilities in steam turbines can prevent operation at full speed and/or full load. The destabilizing forces generating subsynchronous vibrations can be derived from bearings, seals, impellers or other aerodynamic sources. The present paper describes the case of an 11 MW steam turbine, driving a syngas centrifugal compressor train, affected by subsynchronous vibrations at full load. After the occurrence of anomalous vibrations at high load and a machine trip due to the high vibrations, the analysis of data collected at the site confirmed instability of the first lateral mode. Further calculations identified that the labyrinth seal at the balance drum was the main source of destabilizing effects, due to the high pre-swirl and the relatively tight seal clearance. The particular layout of the turbine, a passing-through machine with a combined journal/double thrust bearing on the steam admission side, together with the need for a fast and reliable corrective action limited the possible solutions. Based on the analyses performed, adjusting the clearance and preload of the journal bearings could not have ensured stable operation at each operating condition. The use of swirl brakes to reduce the steam pre-swirl at the recovery seal entrance would have required a lengthy overhaul of the unit and significant labor to access and modify the parts. The final choice was a drop-in replacement of only the rear bearing (on the steam exhaust side) with a bearing featuring integral squeeze film damper (ISFD) technology. In addition to being a time efficient solution, the ISFD technology ensured an effective tuning of stiffness and damping, as proven by the field results. The analyses carried out to understand the source of the subsynchronous vibrations and to identify possible corrective actions, as well as the comparison of rotordynamic data before and after the application of the bearing with ISFD technology, are discussed.

Oil Ring Design Influence on Lube Oil Consumption of SI Engines

2004 ◽  
Author(s):  
Andre´ Ferrarese ◽  
Fernando F. Rovai
Keyword(s):  
Thermal Stability ◽  
The Other ◽  
Oil Consumption ◽  
Ring Type ◽  
Full Load ◽  
Sealing Capacity ◽  
Other Hand ◽  
Actual Use ◽  
Si Engines ◽  
Load Conditions

2-piece and 3-piece oil ring designs were tested in dynamometer and vehicles in order to evaluate the ring type influence on lube oil consumption of spark ignited (SI) engines. The dynamometer tests were executed according a typical durability cycle of SI engines. This cycle is predominantly in full load conditions. Under these conditions, 2-piece oil ring design showed lower lube oil consumption than 3-piece. Two different vehicle tests were also run: urban and mountain circuits. The purpose of the urban circuit test was to simulate the actual use of the engine. The mountain circuit was selected to verify the rings behavior under motoring conditions. In vehicle tests, 3-piece showed lower or equivalent oil consumption than 2 piece, which disagreed with the dynamometer tests. This difference can be explained by the better side sealing capacity of the 3-piece oil ring. On the other hand, 2-piece oil rings present better conformability, important for applications with larger bore distortion. So, the most appropriate application of oil ring type depends on the load and speed conditions, in which the engine would predominantly operate. Ring wear and thermal stability are compared using bench and vehicle tests.

Rotordynamic Stability Under Partial Admission Conditions in a Large Power Steam Turbine

2009 ◽  
Author(s):  
Lin Gao ◽  
Yiping Dai ◽  
Zhiqiang Wang ◽  
Yatao Xu ◽  
Qingzhong Ma
Keyword(s):  
Steam Turbine ◽  
Fluid Model ◽  
Rotor System ◽  
System Stability ◽  
Steam Turbines ◽  
Large Power ◽  
Control Stage ◽  
Partial Admission ◽  
The Stability ◽  
Load Conditions

At present, the majority of power steam turbines operate under part-load conditions during most of their working time in accordance with the fluctuation of power supply. The load governing method may cause partial admission in control stage and even some pressure stages, which impacts much on the stability of the rotor system. In this paper, CFD and FEM method were used to analyze the effect of partial admission on rotor system stability. A new approach is proposed to simplify the 3D fluid model for a partial admission control stage. Rotordynamic analysis was carried out to test the stability of the HP rotor of a 600 MW steam turbine under different load conditions. 13 different governing modes on the rotor stability were conducted and data were analyzed. It is found that rotor stability varies significantly with different governing modes and mass flow rates, which is consistent with the operation. Asymmetric fluid forces resulted from partial admission cause a fluctuation of the dynamic characteristics of the HP bearings, which consequently affect the stability of the rotor system. One of the nozzle governing modes in which the diagonal valves open firstly is demonstrated as the optimal mode with the maximum system stability. The optimization has been applied to 16 power generation units in China and result in improved rotor stabilities.

scholarly journals Influence of Intercept Valves on Control of Multiple Stages Steam Turbines During the Switching into the Island Operation

2015 ◽  
Vol 66 (2) ◽  
pp. 103-107
Author(s):  
Ladislav Laštovka ◽  
Pavla Hejtmánková
Keyword(s):  
High Pressure ◽  
Control System ◽  
Steam Turbine ◽  
Dynamic Load ◽  
The Other ◽  
Steam Turbines ◽  
Electrical Grid ◽  
Operation Status ◽  
Hydraulic Valves ◽  
Multiple Stages

Abstract This paper presents control of a multiple stages steam turbine which is switched into the island operation. The frequency in an electrical grid is stated on nominal value which is in UCTE grid 50 Hz. When deviation of frequency is higher then 0.2 Hz, the switching of particular steam units into the island operation is only the chance how to maintain the supply of, at least, some small grids. The other possibility how to keep power units in operation, to be prepared for the next synchronization to the grid, is to switch them to operation status in which they supply only their self-consumption. This change of the operating state is the most dynamic load change for the control system of the unit. The multiple stages turbines are equipped with high pressure hydraulic valves for steam turbine governing. Influence of the intercept valve on steam turbine control during the switching process into the island operation is examined in Matlab Simuling software.

Computations for Unsteady Compressible Flows in a Multi-Stage Steam Turbine With Steam Properties at Low Load Operations

2010 ◽  
Author(s):  
Shigeki Senoo ◽  
Kiyoshi Segawa ◽  
Hisashi Hamatake ◽  
Takeshi Kudo ◽  
Tateki Nakamura ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Compressible Flows ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Computation Time ◽  
Steam Turbines ◽  
Multi Stage ◽  
Low Load ◽  
Pressure Steam ◽  
Load Conditions

A computational technique for compressive fluid in multistage steam turbines which can allow for thermodynamic properties of steam is presented. The understanding and prediction of flow field not only at design conditions but also at off-design conditions are important for realizing high-performance and high-reliability steam turbines. Computational fluid dynamics is useful for estimations of flows. However, current three-dimensional multi-stage calculations for unsteady flows have two main problems. One is the long computation time and the other is how to include the thermodynamic properties of steam. Properties of the ideal gas, such as equations of state and enthalpy formula, are assumed in most computational techniques for compressible flows. In order to shorten the computation time, a quasi-three-dimensional flow calculation technique is developed. In the analysis, system equations of conservation laws for compressible fluid in axisymmetric cylindrical coordinates are solved by using a finite volume method based on an approximate Riemann solver. Blade forces are calculated from the camber and lean angles of blades using momentum equations. The axisymmetric assumption and the blade force model enable the effective calculation for multi-stage flows, even when the flow is strongly unsteady under off-design conditions. In order to take into account steam properties including effects of the gas-liquid phase change and two-phase flow, a flux-splitting procedure of compressible flow is generalized for real fluid. Density and internal energy per unit volume are selected as independent thermodynamic variables. Pressure and temperature in a superheated region or wetness mass fraction in a wet region are calculated by using a steam table. To improve computational efficiency, a discretized steam table matrix is made in which the density and specific internal energy are independent variables. For accuracy and continuity of steam properties, the second order Taylor expansion and linear interpolation are introduced. The computed results of last four-stage low-pressure steam turbine at low load conditions show that there is a reverse flow near the hub region of the last (fourth stage bucket and the flow concentrates in the tip region due to the centrifugal force. At a very low load condition, the reverse flow region extends to the former (i.e. the first to third) stages and the unsteadiness of flow gets larger due to many vortices. Four-stage low pressure steam turbine tests are also carried out at low load or even zero load. The radial distributions of flow direction downstream from each stage are measured by traversing pneumatic probes. Additionally pressure transducers are installed in the side wall to measure the unsteady pressure. The regions of reverse flow are compared between computations and experiments at different load conditions, and their agreement is good. Further, the computation can follow the trends of standard deviation of unsteady pressure on the wall to volumetric flow rate of experiments. The validity of the analysis method is verified.

Thermo-Economic Analysis of an Intercooled, Reheat and Recuperated Gas Turbine for Cogeneration Applications: Part II — Part-Load Operation

2001 ◽  
Author(s):  
R. Bhargava ◽  
G. Negri di Montenegro ◽  
A. Peretto
Keyword(s):  
Economic Analysis ◽  
Gas Turbine ◽  
The Other ◽  
Load Range ◽  
Part Load ◽  
Full Load ◽  
Performance Loss ◽  
Low Load ◽  
Cogeneration System ◽  
Load Conditions

The knowledge of off-design performance for a given gas turbine system is critical particularly in applications where considerable operation at low load setting is required. This information allows designers to ensure safe operation of the system and determine in advance thermo-economic penalty due to performance loss while operating under part-load conditions. In this paper, thermo-economic analysis results for the intercooled, reheat (ICRH) and recuperated gas turbine, at the part-load conditions in cogeneration applications, have been presented. Thermodynamically, a recuperated ICRH gas turbine based cogeneration system showed lower penalty in terms of electric efficiency and Energy Saving Index over the entire part-load range in comparison to the other cycles (non-recuperated ICRH, recuperated Brayton and simple Brayton cycles) investigated. Based on the comprehensive economic analysis for the assumed values of economic parameters, this study shows that, a mid-size (electric power capacity 20 MW) cogeneration system utilizing non-recuperated ICRH cycle provides higher return on investment both at full-load and part-load conditions, compared to the other same size cycles, over the entire range of fuel cost, electric sale and steam sale values examined. The plausible reasons for the observed trends in thermodynamic and economic performance parameters for four cycles and three sizes of cogeneration systems under full-load and part-load conditions have been presented in this paper.

Thermoeconomic Analysis of an Intercooled, Reheat, and Recuperated Gas Turbine for Cogeneration Applications—Part II: Part-Load Operation

2002 ◽  
Vol 124 (4) ◽  
pp. 892-903 ◽  
Author(s):  
R. Bhargava ◽  
G. Negri di Montenegro ◽  
A. Peretto
Keyword(s):  
Gas Turbine ◽  
The Other ◽  
Safe Operation ◽  
Load Range ◽  
Part Load ◽  
Full Load ◽  
Performance Loss ◽  
Low Load ◽  
Cogeneration System ◽  
Load Conditions

The knowledge of off-design performance for a given gas turbine system is critical particularly in applications where considerable operation at low load setting is required. This information allows designers to ensure safe operation of the system and determine in advance thermoeconomic penalty due to performance loss while operating under part-load conditions. In this paper, thermoeconomic analysis results for the intercooled reheat (ICRH) and recuperated gas turbine, at the part-load conditions in cogeneration applications, have been presented. Thermodynamically, a recuperated ICRH gas turbine-based cogeneration system showed lower penalty in terms of electric efficiency and Energy Saving Index over the entire part-load range in comparison to the other cycles (nonrecuperated ICRH, recuperated Brayton and simple Brayton cycles) investigated. Based on the comprehensive economic analysis for the assumed values of economic parameters, this study shows that a midsize (electric power capacity 20 MW) cogeneration system utilizing nonrecuperated ICRH cycle provides higher return on investment both at full-load and part-load conditions, compared to the other same size cycles, over the entire range of fuel cost, electric sale, and steam sale values examined. The plausible reasons for the observed trends in thermodynamic and economic performance parameters for four cycles and three sizes of cogeneration systems under full-load and part-load conditions have been presented in this paper.

Mechanical Design of Large Steam Turbine Components for Part Load Conditions

2013 ◽  
Author(s):  
N. Lückemeyer ◽  
F. Qin
Keyword(s):  
Steam Turbine ◽  
Structural Integrity ◽  
Mechanical Design ◽  
Point Of View ◽  
Heat Radiation ◽  
Steam Turbines ◽  
Load Case ◽  
Part Load ◽  
Load Regime ◽  
Load Conditions

Recent developments like the significant introduction of renewable energy sources to the electricity networks worldwide have led to more frequent and extended operation of fossil power plants in part load conditions. As a result the typical load spectrum of large steam turbines used for electricity generation has changed over the last years and will continue to do so. A number of papers has already been published on how to optimize the water-steam cycle and the steam turbine from a thermodynamical and aero-dynamical point of view for this new load regime in order to improve the average efficiency. But the changed load regime also poses a challenge for the mechanical design and structural integrity assessment of steam turbines. Reason for this is that the rated conditions are not necessarily the most challenging boundary conditions and therefore not necessarily a suitable, conservative envelope for all other load cases for mechanical design. Pressures decrease, but steam temperatures in part loads can increase and heat transfer coefficients and the influence of radiation on the component temperatures change. With an increasing demand for and a wider range of part load operation it for this reason becomes more important than ever to consider these load cases in the mechanical design. This paper uses a large, double-flow intermediate pressure steam turbine as an example to investigate the impact of extended part load operation on the design. Both an analytical model and finite element calculations are used to compare from a structural integrity point of view a low part-load load case and the rated load case and to evaluate the significance of heat radiation.

Nuclear Steam Turbine With 60 inch Last Stage Blade

2013 ◽  
Author(s):  
Motonari Haraguchi ◽  
Tateki Nakamura ◽  
Hideo Yoda ◽  
Takeshi Kudo ◽  
Shigeki Senoo
Keyword(s):  
Steam Turbine ◽  
Nuclear Power ◽  
New Technologies ◽  
The Other ◽  
Power Equipment ◽  
Steam Turbines ◽  
Candu Reactors ◽  
Last Stage ◽  
Reactor Types ◽  
And Performance

Nuclear steam turbines can be classified into two categories, one for BWR reactors where some countermeasures are taken for radiated steam and water, the other is for PWR reactors and PHWR (CANDU) reactors where steam and water are not radiated. As for Low Pressure section, there is some difference in LP rotor end structure, and LP last three stage blade components can be applied to all reactor types. The trend in nuclear power equipment is in a direction of larger capacity. In response to this trend, longer last stage blade is required if same number of casing is kept to make nuclear turbines reasonably compact. This paper addresses some of the key developments and new technologies to be employed focusing on longer Last Stage Blade (LSB) development with Continuous Cover Blades (CCB), and other enhancements in product reliability and performance.

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