Improving the Incremental Regulation of Steam Turbines Equipped With Mechanical Hydraulic Control (MHC) Systems

2011 ◽  
Author(s):  
William Newbury ◽  
Steve DeCrow
Keyword(s):  
Steam Turbine ◽  
Steam Flow ◽  
Control Mode ◽  
Valve Lift ◽  
Hydraulic Control ◽  
Steam Turbines ◽  
Load Range ◽  
Load Following ◽  
Turbine Generators ◽  
Major Factors

Prior to 1970, mechanical hydraulic control (MHC) systems were used as the industry standard for operating steam turbine generators in the USA. These systems were primarily designed for safe, reliable, efficient base load operation close to nameplate rating. Today, most steam turbine generators rated at 400 megawatts (MW) or below are required to operate in some form of automatic load following central dispatch control mode. This mode of operation necessitates the need to provide a predictable linear output response to a specific demand input signal within a wide load range. A typical MHC system “Fig.1” performs multiple proportional response functions. The contents of this paper focus on the proportional relationship of the hydraulic operating cylinder stroke relative to the steam flow resulting from control valve lift specific to steam turbines manufactured by the General Electric Co. and Allis Chalmers Co. The purpose of this paper is to raise the level of awareness to: 1. The reasons why most MHC systems have difficulty operating in automatic load following mode. 2. The major factors contributing to this operating problem. 3. A proven methodology to quantify the influence of these major factors. 4. A proven cost effective approach to improving non-linear steam flow without major modifications.

Influence of Turbulence Modelling to Condensing Steam Flow in the 3D Low-Pressure Steam Turbine Stage

2016 ◽  
Author(s):  
Yogini Patel ◽  
Giteshkumar Patel ◽  
Teemu Turunen-Saaresti
Keyword(s):  
Steam Turbine ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Rapid Change ◽  
Low Pressure ◽  
Turbulence Modelling ◽  
Steam Flow ◽  
Droplet Growth ◽  
Steam Turbines ◽  
Turbine Stage

With the tremendous role played by steam turbines in power generation cycle, it is essential to understand the flow field of condensing steam flow in a steam turbine to design an energy efficient turbine because condensation at low pressure (LP) turbine introduces extra losses, and erosion in turbine blades. The turbulence has a leading role in condensing phenomena which involve a rapid change of mass, momentum and heat transfer. The paper presents the influence of turbulence modelling on non-equilibrium condensing steam flows in a LP steam turbine stage adopting CFD code. The simulations were conducted using the Eulerian-Eulerian approach, based on Reynolds-averaged Navier-Stokes equations coupled with a two equation turbulence model, which is included with nucleation and droplet growth model for the liquid phase. The SST k-ω model was modified, and the modifications were implemented in the CFD code. First, the performance of the modified model is validated with nozzles and turbine cascade cases. The effect of turbulence modelling on the wet-steam properties and the loss mechanism for the 3D stator-rotor stage is discussed. The presented results show that an accurate computational prediction of condensing steam flow requires the turbulence to be modelled accurately.

Slow-Roll of 40-MW Condensing-Extraction Steam Turbines in a 420-MW Cogeneration Plant

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Steve Ingistov ◽  
Michael Milos ◽  
Rakesh K. Bhargava
Keyword(s):  
Steam Turbine ◽  
Field Testing ◽  
Economic Losses ◽  
Successful Implementation ◽  
Steam Turbines ◽  
Turbine Generators ◽  
Rotor Design ◽  
Slow Roll ◽  
Extensive Field ◽  
Mode Of Operation

This paper describes efforts required to operate a cogeneration facility's extraction-condensing steam turbine generators with flexible rotor design on a slow-roll mode of operation (also called true stand-by). Slow-roll mode of operation became necessary due to changing steam demand from the host refinery, resulting in decreased performance of the steam turbine generators and their associated economic losses. Design modifications implemented to achieve slow-roll of steam turbine generators without affecting reliability and availability of the entire cogeneration facility are discussed in this paper. Successful implementation of the design modifications was demonstrated via extensive field testing on two steam turbine generator units during the summer of 2011. A simple life cycle economic analysis shows the payback period for the project is approximately seven months.

Slow-Roll of 40 MW Condensing-Extraction Steam Turbines in a 420 MW Cogeneration Plant

2012 ◽  
Author(s):  
Steve Ingistov ◽  
Michael Milos ◽  
Rakesh K. Bhargava
Keyword(s):  
Steam Turbine ◽  
Field Testing ◽  
Economic Losses ◽  
Successful Implementation ◽  
Steam Turbines ◽  
Turbine Generators ◽  
Rotor Design ◽  
Slow Roll ◽  
Extensive Field ◽  
Mode Of Operation

This paper describes efforts required to operate condensing-extraction steam turbine generators with flexible rotor design on a slow-roll (also called, true stand-by) mode of operation. This mode of operation became necessary as a result of changing steam demand from the refinery and the resulting decreased performance of the existing steam turbine generators and the associated economic losses for the cogeneration facility. Design modifications implemented to achieve slow-roll of steam turbine generators and produce maximum power output obtainable with new steam flow conditions without affecting reliability and availability of the entire cogeneration facility are discussed in this paper. Successful implementation of the proposed design approach was demonstrated through extensive field testing completed in the summer of 2011. A simple life cycle economic analysis shows that the payback period associated with the proposed design modifications implemented to two steam turbine generators at the plant is approximately six (6) months.

Effect of Inlet Steam Temperature on the HP Section Efficiency of a Steam Turbine

2015 ◽  
Author(s):  
Yiping Fu ◽  
Thomas Winterberger
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Pressure Ratio ◽  
Control Valve ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Steam Temperature ◽  
Load Range ◽  
Lp Turbine ◽  
The Relationship

Steam turbines for modern fossil and combined cycle power plants typically utilize a reheat cycle with High Pressure (HP), Intermediate Pressure (IP), and Low Pressure (LP) turbine sections. For an HP turbine section operating entirely in the superheat region, section efficiency can be calculated based on pressure and temperature measurements at the inlet and exhaust. For this case HP section efficiency is normally assumed to be a constant value over a load range if inlet control valve position and section pressure ratio remain constant. It has been observed that changes in inlet steam temperature impact HP section efficiency. K.C. Cotton stated that ‘the effect of throttle temperature on HP turbine efficiency is significant’ in his book ‘Evaluating and Improving Steam Turbine Performance’ (2nd Edition, 1998). The information and conclusions provided by K.C. Cotton are based on test results for large fossil units calculated with 1967 ASME steam tables. Since the time of Mr. Cotton’s observations, turbine configurations have evolved, more accurate 1997 ASME steam tables have been released, and our ability to quickly analyze large quantities of data has greatly increased. This paper studies the relationship between inlet steam temperature and HP section efficiency based on both 1967 and 1997 ASME steam tables and recent test data, which is analyzed computationally to reveal patterns and trends. With the efficiencies of various inlet pressure class HP section turbines being calculated with both 1967 and 1997 ASME steam tables, a comparison reveals different characteristics in the relationship between inlet steam temperature and HP section efficiency. Recommendations are made on how the results may be used to improve accuracy when testing and trending HP section performance.

Investigation of wet steam flow in a 300 MW direct air-cooling steam turbine. Part 1: Measurement principles, probe, and wetness

2009 ◽  
Vol 223 (5) ◽  
pp. 625-634 ◽  
Author(s):  
X Cai ◽  
T Ning ◽  
F Niu ◽  
G Wu ◽  
Y Song
Keyword(s):  
Steam Turbine ◽  
Steam Flow ◽  
Light Extinction ◽  
Air Cooling ◽  
Steam Turbines ◽  
Wet Steam ◽  
The North ◽  
Multi Wavelength ◽  
Wet Steam Flow ◽  
Short Time

The direct air-cooling steam turbines have been operated more and more in the north of China. The backpressure of a turbine is affected easily with weather and varies very often in a short time. The variation of backpressure in a larger range from about 10 to 60 kPa causes many problems in design and operation of the turbine. To study the properties of the wet steam flow in the low pressure direct air-cooling steam turbine, an optical—pneumatic probe was developed based on the multi-wavelength light extinction and four-hole wedge probe. Measurements with this probe in a 300 MW direct air-cooling turbine were carried out. The measured local wetness, total wetness of exhaust steam, size distribution of fine droplets, and their profiles along the blade height are presented. The measured cylinder efficiency and total wetness agree well with the results obtained by the thermal performance tests.

Eulerian-Lagrangian Numerical Simulation of Wet Steam Flow Through Multi-Stage Steam Turbine

2013 ◽  
Author(s):  
Yasuhiro Sasao ◽  
Satoshi Miyake ◽  
Kenji Okazaki ◽  
Satoru Yamamoto ◽  
Hiroharu Ooyama
Keyword(s):  
Steam Turbine ◽  
Turbine Blades ◽  
Steam Flow ◽  
Droplet Growth ◽  
Computational Domain ◽  
Steam Turbines ◽  
Wet Steam ◽  
Multi Stage ◽  
Flow Through ◽  
Wet Steam Flow

In this paper, we present an inclusive tracking algorithm for water droplets in a wet steam flow through a multi-stage steam turbine. This algorism is based on the Eulerian-Lagrangian coupled solver. The solver continuously computes water droplet growth, kinematic non-equilibrium between vapor and droplets, capture and kinetics of droplets on turbine blades, departure of large droplets from the trailing edge of blades, acceleration and atomization of large droplets, and recollisions between blades and droplets. Our Eulerian-Lagrangian coupled solver is used to predict wetness in unsteady three-dimensional (3D) wet steam flows through three-stage stator rotor cascade channels in a low pressure (LP) steam turbine model which is developed by Mitsubishi Heavy Industries (MHI). Droplet groups tracked by the discrete droplet model (DDM) are placed in the computational domain according to the predicted wetness. Interference from the gas phase on the droplets is considered, to track their kinetic and behavior, until they reach the outlet of the computational domain. The aim of this research is to investigate those multi-physics phenomena that trigger all forms of loss in steam turbines. In addition, this method will also be applied to multi-physics problems such as erosion in future work. This paper is presented as a first step in the research. Overviews of model of current coupling solver and several test calculations are presented.

Catastrophe Performance Analysis of Steam-Flow-Excited Vibration in the Governing Stage of Large Steam Turbines With Partial Admission

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Jianlan Li ◽  
Xuhong Guo ◽  
Chen Yu ◽  
Shuhong Huang
Keyword(s):  
Performance Analysis ◽  
Steam Turbine ◽  
Catastrophe Theory ◽  
Exciting Force ◽  
Steam Flow ◽  
Impact Factors ◽  
Steam Turbines ◽  
Excited Vibration ◽  
Partial Admission ◽  
The Impact

Steam-flow-excited vibration is one of the main faults of large steam turbines. The catastrophe caused by steam-flow-excited vibration brings danger to the operation of units. Therefore, it is significant to identify the impact factors of catastrophe, and master the rules of catastrophe. In this paper, the quantitative analysis of catastrophe performance induced by steam exciting force in the steam turbine governing stage is conducted based on the catastrophe theory, nonlinear vibration theory, and fluid dynamics. The model of steam exciting force in the condition of partial admission in the governing stage is derived. The nonlinear kinetic model of the governing stage with steam exciting force is proposed as well. The cusp catastrophe and bifurcation set of steam-flow-excited vibration are deduced. The rotational angular frequency, the eccentric distance and the opening degrees of the governing valves are identified as the main impact factors to induce catastrophe. Then, the catastrophe performance analysis is conducted for a 300 MW subcritical steam turbine. The rules of catastrophe are discussed, and the system's catastrophe areas are divided. It is discovered that the system catastrophe will not occur until the impact factors satisfy given conditions. Finally, the numerical calculation method is employed to analyze the amplitude response of steam-flow-excited vibration. The results verify the correctness of the proposed analysis method based on the catastrophe theory. This study provides a new way for the catastrophe performance research of steam-flow-excited vibration in large steam turbines.

Fault diagnosis method of peak-load-regulation steam turbine based on improved PCA-HKNN artificial neural network

2021 ◽  
pp. 1748006X2110105
Author(s):  
Yifan Wu ◽  
Wei Li ◽  
Deren Sheng ◽  
Jianhong Chen ◽  
Zitao Yu
Keyword(s):  
Neural Network ◽  
Fault Diagnosis ◽  
Steam Turbine ◽  
Power Plants ◽  
Peak Load ◽  
Clean Energy ◽  
Steam Turbines ◽  
Peak Shaving ◽  
Diagnosis Method ◽  
Load Regulation

Clean energy is now developing rapidly, especially in the United States, China, the Britain and the European Union. To ensure the stability of power production and consumption, and to give higher priority to clean energy, it is essential for large power plants to implement peak shaving operation, which means that even the 1000 MW steam turbines in large plants will undertake peak shaving tasks for a long period of time. However, with the peak load regulation, the steam turbines operating in low capacity may be much more likely to cause faults. In this paper, aiming at peak load shaving, a fault diagnosis method of steam turbine vibration has been presented. The major models, namely hierarchy-KNN model on the basis of improved principal component analysis (Improved PCA-HKNN) has been discussed in detail. Additionally, a new fault diagnosis method has been proposed. By applying the PCA improved by information entropy, the vibration and thermal original data are decomposed and classified into a finite number of characteristic parameters and factor matrices. For the peak shaving power plants, the peak load shaving state involving their methods of operation and results of vibration would be elaborated further. Combined with the data and the operation state, the HKNN model is established to carry out the fault diagnosis. Finally, the efficiency and reliability of the improved PCA-HKNN model is discussed. It’s indicated that compared with the traditional method, especially handling the large data, this model enhances the convergence speed and the anti-interference ability of the neural network, reduces the training time and diagnosis time by more than 50%, improving the reliability of the diagnosis from 76% to 97%.

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