scholarly journals Turbine Cascades of Last Stage Blades for Wide Range of Operating Conditions

2019 ◽  
Vol 4 (4) ◽  
pp. 33 ◽  
Author(s):  
Ondrej Novak ◽  
Marek Bobcik ◽  
Martin Luxa ◽  
Jaroslav Fort ◽  
Bartolomej Rudas ◽  
...  
Keyword(s):  
Steam Turbine ◽  
High Speed ◽  
Power Plants ◽  
Electric Energy ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Biomass Waste ◽  
Wide Range ◽  
Last Stage ◽  
Turbine Cascades

Recent trends in the electric energy market such as biomass, waste incineration or combined cycle power plants require innovative solutions in steam turbine design. Variable operating conditions cause significant changes in flow field surrounding the steam turbine last stage blades. Therefore, the enlargement of operating range for last stage blades presents new challenges in design of turbine cascades. Several turbine cascades were designed and analyzed by commercial and in-house software of CTU Prague. Selected profiles were experimentally validated in the high-speed wind tunnel for 2D cascade measurements of the Institute of Thermomechanics of the Czech Academy of Sciences which is equipped by an adjustable supersonic inlet nozzle, perforated inserts at side walls and adjustable perforated tailboard. Comparisons are presented of numerical results with optical and pneumatic measurements for a wide range of inlet and outlet Mach numbers for optimized hub and tip profile cascades.

Development of 60Hz Titanium 48-Inch Last Stage Blade for Steam Turbine

2011 ◽  
Author(s):  
Yoriharu Murata ◽  
Naoki Shibukawa ◽  
Itaru Murakami ◽  
Joji Kaneko ◽  
Kenichi Okuno
Keyword(s):  
Steam Turbine ◽  
Mechanical Design ◽  
Thermal Power ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Scale Model ◽  
Test Facility ◽  
Recent Analysis ◽  
Last Stage ◽  
Actual Size

The titanium 48-inch last stage blade that has world’s largest class exhaust annulus area and tip speed for 60Hz steam turbines has been developed. Concept of this blade is to achieve high performance and compact design of steam turbine for 1000MW thermal power plant and 300MW combined cycle plant. In the design of this blade, the optimization design has been done by using the recent analysis technologies, three dimensional CFD in aerodynamic design and FEA in mechanical design. The blade has curved axial fir-tree dovetail, snubber cover both at the tip and at the mid-span. To achieve superior vibration characteristics, continuously coupled structure was adopted for blade connection. To confirm the validity of design, first, sub-scale model blades were provided and tested in model steam turbine test facilities. Second, one row of actual size blades were assembled on the wheel of test rotor and were exposed rotating vibration test in a wheel box. Finally, these blades were tested at actual steam conditions in a full scale steam turbine test facility. In this paper, aerodynamic and mechanical design features will be introduced, and the test results of both sub-scale and actual size blades under real steam turbine operating conditions will be presented.

Development of LP Blade Module for High Back Pressure-Aerodynamic Design

2017 ◽  
Author(s):  
Ambrish ◽  
Nand Kumar Singh
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Volume Flow Rate ◽  
Back Pressure ◽  
Operating Conditions ◽  
Total Efficiency ◽  
Aerodynamic Design ◽  
Streamline Curvature ◽  
Pressure Application ◽  
Wide Range

In steam turbine power plants, the appropriate design of the last stage blades is critical in determining the plant efficiency and reliability. The development of LP module for desert applications is finding applications for a number of industrial steam turbine operating with air cooled condensers. The conventional LP Module for water cooled condenser operates at low back pressure (Pexit = 0.09 bar) and are generally not suitable for high back pressure application. This paper focuses on the aerodynamic design & optimization of last stages of LP blade module for high back pressure application and validation through 3D CFD. The guide and moving blade are designed with seven equally-spaced profiles section from hub to shroud through Axstream S/w. The profile and incidence losses are minimized for the design and off-design conditions. Aeromechanical design of LP blade module consisting of 2 stages for 0.2 bar back pressure, 1.1 bar inlet static pressure and a mass flow of 61.2 kg/s is carried out. An optimization process through a streamline curvature code and design optimization software using Optimus is established and flow path contours is optimized thoroughly, a total to total efficiency of 81.4% is achieved for the rated condition. The off-design performance is investigated for a wide range of operating conditions, especially at low volume flow rate of steam condition.

CFD Modelling of Steam Turbine Last Stage Blades at Low Load Using Multiple Mixing Plane Approach

2020 ◽  
Author(s):  
Antonio Mambro ◽  
Francesco Congiu ◽  
Enzo Galloni
Keyword(s):  
Steam Turbine ◽  
Flow Behavior ◽  
Volume Flow ◽  
Operating Conditions ◽  
Continuous Increase ◽  
Multiple Mixing ◽  
Wide Range ◽  
Low Load ◽  
Last Stage ◽  
Low Volume

Abstract The continuous increase of variable renewable energy and fuel cost requires steam turbine power plants to operate with high flexibility. This situation leads to steam turbines running at very low volume flow (LVF) for an extended time. Ventilation power and temperature predictions have a significant impact on the thermo-economic optimization of the power plant and lifetime assessment of the ventilating stages. In the last decade with increasing capabilities of CFD and computational resources, significant steps have been made in assessing complex flow behavior. Full size or scaled experimental testing of different last stage blades for a wide range of low load operating conditions is expensive, therefore CFD provides new opportunities in low load assessment. However, prediction of the flow structure of the ventilating stages still represents a challenge for the current CFD tools in terms of calculation time and reliability of the results. There are many different approaches in assessing this phenomenon, which require different computer resources and may not be necessary for most industrial applications. This paper presents the validation of the multiple mixing plane approach (MMP) presented by [9] for low-pressure steam turbine running at low load. Through a comparison with measurements results and more sophisticated methods, it is shown that this approach is able to sufficiently accurately predict the flow field and hence the ventilation power and temperature at low volume flow.

Design, Manufacturing and Testing of a New Family of Steam Turbine Low Pressure Stages

2007 ◽  
Author(s):  
Lorenzo Cosi ◽  
Jonathon Slepski ◽  
Steven DeLessio ◽  
Michele Taviani ◽  
Amir Mujezinovic´
Keyword(s):  
Power Generation ◽  
Steam Turbine ◽  
Low Pressure ◽  
Full Scale ◽  
Operating Conditions ◽  
Test Facility ◽  
Steam Turbines ◽  
Wide Range ◽  
The Family ◽  
Last Stage

New low pressure (LP), stages for variable speed, mechanical drive and geared power generation steam turbines have been developed. The new blade and nozzle designs can be applied to a wide range of turbine rotational speeds and last stage blade annulus areas, thus forming a family of low pressure stages—High Speed (HS) blades and nozzles. Different family members are exact scales of each other and the tip speeds of the corresponding blades within the family are identical. Thus the aeromechanical and aerodynamic characteristics of the individual stages within the family are identical as well. Last stage blades and nozzles have been developed concurrently with the three upstream stages, creating optimised, reusable low pressure turbine sections. These blades represent a step forward in improving speed, mass flow capability, reliability and aerodynamic efficiency of the low pressure stages for the industrial steam turbines. These four stages are designed as a system using the most modern design tools applied on Power Generation and Aircraft Engines turbo-machineries. The aerodynamic performance of the last three stage of the newly designed group will be verified in a full-scale test facility. The last stage blade construction incorporates a three hooks, axial entry dovetail with improved load carrying capability over other blade attachment methods. The next to the last stage blade also uses a three hooks axial entry dovetail, while the two front stage blades employ internal tangential entry dovetails. The last and next to the last stage blades utilize continuous tip coupling via implementation of integral snubber cover while a Z-lock integral cover is employed for the two upstream stages. Low dynamic strains at all operating conditions (off and on resonance speeds) will be validated via steam turbine testing at realistic steam conditions (steam flows, temperatures and pressures). Low load, high condenser pressure operation will also be verified using a three stage test turbine operated in the actual steam conditions as well. In addition, resonance speed margins of the four stages have been verified through full-scale wheel box tests in the vacuum spin cell, thus allowing the application of these stages to Power Generation applications. Stator blades are produced with a manufacturing technology, which combines full milling and electro-discharge machining. This process allows machining of the blades from an integral disc, and thus improving uniformity of the throat distribution. Accuracy of the throat distribution is also improved when compared to the assembled or welded stator blade technology. This paper will discuss the aerodynamic and aeromechanical design, development and testing program completed for this new low pressure stages family.

Evaluation of Impact Loads of Clutch Engaging Within Single Shaft Applications for Power Generation

2008 ◽  
Author(s):  
Bernd Lu¨neburg ◽  
Meinolf Klocke ◽  
Stefan Kulig ◽  
Frank Joswig
Keyword(s):  
Power Generation ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Impact Loading ◽  
Power Plants ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Mass Model ◽  
Inertia Effects ◽  
The Impact

Combined Cycle Power Plants (CCPP) in single shaft arrangements consist of a gas turbine, a generator and a steam turbine on one shaft line. In order to enhance the plant availability and operational flexibility, Siemens Fossil Power Generation introduces a switchable clutch between steam turbine and generator. The clutch is a synchronous self-shifting device that engages automatically at rated speed as soon as the steam turbine overruns the gas turbine-generator. It disengages automatically when the steam turbine speed drops below the speed of the gas turbine. A rather complicated mechanism consisting pawls and ratchets and a thread of helical splines including damper mechanisms is used to provide the required coupling functions. The primary reason for the clutch is to ensure independent gas turbine and steam turbine operation below steam turbine rated speed. The clutch is especially advantageous during startup and gas turbine simple-cycle operation. Next to these advantages, the clutch engaging processes could introduce significant impact loading to the shaft components which differ from other. Next to the normal engaging process fault cases like engaging processes after gas turbine trip at high acceleration values due to the gas turbine compressor losses must be sustained by all rotor train components. This paper documents a nonlinear torsional analysis of the single shaft arrangement to assess the impact loading due to clutch engaging processes. A dynamic three-mass-model of the clutch including nonlinear stiffness and damping functions is set up and applied for the simulations. The coupling of the translatory and the rotatory inertia effects of the main sliding component of the clutch has been taken into account. Different load case scenarios in different single shaft component arrangements respectively different inertia ranges of the steam turbine rotor train are investigated in detail by the transient analyses. Based on this procedure, it is ensured that the mechanical layout of the single shaft components is sufficiently designed to withstand all operational loads under normal and faulty operating conditions.

Development of a Robust LP Blade Family for Variable Speed Applications

2018 ◽  
Author(s):  
Martin Schubert ◽  
Johannes Tusche
Keyword(s):  
Steam Turbine ◽  
High Speed ◽  
Design Method ◽  
Suction Side ◽  
Operating Conditions ◽  
Subsequent Paper ◽  
Variable Speed ◽  
Design Changes ◽  
Last Stage ◽  
High Flexibility

Industrial steam turbine applications require a high flexibility in terms of aerodynamically as well as mechanically operating conditions. Mechanical drives run at variable rotor speeds and often face high backpressure levels, which is a particularly challenging aspect for the last-stage moving blade (LSMB) row of a low-pressure (LP) steam turbine. As speed synchronous blade resonances cannot be excluded over the entire operating speed range, the LSMB needs to be designed resonance proof from viewpoint of dynamics and mechanical strength. The subsequent paper describes a new developed LP stage group for variable speed applications, which is available as fully scaled blade family with distinct exhaust area and rotational speed limit reaching from conventional 3000rpm up to high speed utilities for special purposes. It consists of two standard stages, which can be operated at off resonance as well as resonance conditions. For that reason frictional elements were implemented in both moving blade rows. They are loosely assembled into pockets, which are placed on the pressure as well as suction side of each airfoil. Basically, this feature was already introduced for certain Siemens LP blades, see [1], [2], [3] and [4]. However, the recent development on this field utilizes several design changes for the benefit of robustness and reliability. The present paper focuses on the non-linear dynamic behavior of the friction damped, coupled blade rows and outlines the underlying design method as well as calculation process.

Absorber modeling for NGCC carbon capture with aqueous piperazine

2016 ◽  
Vol 192 ◽  
pp. 459-477 ◽  
Author(s):  
Yue Zhang ◽  
Brice Freeman ◽  
Pingjiao Hao ◽  
Gary T. Rochelle
Keyword(s):  
Flue Gas ◽  
Water Availability ◽  
Carbon Capture ◽  
Power Plants ◽  
Cooling Water ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Wide Range ◽  
Natural Gas Combined Cycle ◽  
Dry Cooling

A hybrid system combining amine scrubbing with membrane technology for carbon capture from natural gas combined cycle (NGCC) power plants is proposed in this paper. In this process, the CO2 in the flue gas can be enriched from 4% to 18% by the membrane, and the amine scrubbing system will have lower capture costs. Aqueous piperazine (PZ) is chosen as the solvent. Different direct contact cooler (DCC) options, multiple absorber operating conditions, optimal intercooling designs, and different cooling options have been evaluated across a wide range of inlet CO2. Amine scrubbing without DCC is a superior design for NGCC carbon capture. Pump-around cooling at the bottom of the absorber can effectively manage the temperature of the hot flue gas, and still be effective for CO2 absorption. The absorber gas inlet must be designed to avoid excessive localized temperature and solvent evaporation. When the inlet CO2 increases from 4% to 18%, total absorber CAPEX decreases by 60%; another 10% of the total absorber CAPEX can be saved by eliminating the DCC. In-and-out intercooling works well for high CO2, while pump-around intercooling is more effective for low CO2. Dry cooling requires more packing and energy but appears to be technically and economically feasible if cooling water availability is limited.

Repowering and Retrofitting

2002 ◽  
Author(s):  
Andreas Pickard
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Free Market ◽  
Leading Edge ◽  
Project Planning ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Planning Stage ◽  
Reheat Steam ◽  
Plant Optimization

At the start of this new century, environmental regulations and free-market economics are becoming the key drivers for the electricity generating industry. Advances in Gas Turbine (GT) technology, allied with integration and refinement of Heat Recovery Steam Generators (HRSG) and Steam Turbine (ST) plant, have made Combined Cycle installations the most efficient of the new power station types. This potential can also be realized, to equal effect, by adding GT’s and HRSG’s to existing conventional steam power plants in a so-called ‘repowering’ process. This paper presents the economical and environmental considerations of retrofitting the steam turbine within repowering schemes. Changing the thermal cycle parameters of the plant, for example by deletion of the feed heating steambleeds or by modified live and reheat steam conditions to suit the combined cycle process, can result in off-design operation of the existing steam turbine. Retrofitting the steam turbine to match the combined cycle unit can significantly increase the overall cycle efficiency compared to repowering without the ST upgrade. The paper illustrates that repowering, including ST retrofitting, when considered as a whole at the project planning stage, has the potential for greater gain by allowing proper plant optimization. Much of the repowering in the past has been carried out without due regard to the benefits of re-matching the steam turbine. Retrospective ST upgrade of such cases can still give benefit to the plant owner, especially when it is realized that most repowering to date has retained an unmodified steam turbine (that first went into operation some decades before). The old equipment will have suffered deterioration due to aging and the steam path will be to an archaic design of poor efficiency. Retrofitting older generation plant with modern leading-edge steam-path technology has the potential for realizing those substantial advances made over the last 20 to 30 years. Some examples, given in the paper, of successfully retrofitted steam turbines applied in repowered plants will show, by specific solution, the optimization of the economics and benefit to the environment of the converted plant as a whole.

Inlet Air Cooling Applied to Combined Cycle Power Plants: Influence of Site Climate and Thermal Storage Systems

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Nicola Palestra ◽  
Giovanna Barigozzi ◽  
Antonio Perdichizzi
Keyword(s):  
Power Output ◽  
Parametric Analysis ◽  
Power Plants ◽  
Cooling System ◽  
Thermal Storage ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Air Cooling ◽  
Ambient Conditions ◽  
Cooling Systems

The paper presents the results of an investigation on inlet air cooling systems based on cool thermal storage, applied to combined cycle power plants. Such systems provide a significant increase of electric energy production in the peak hours; the charge of the cool thermal storage is performed instead during the night time. The inlet air cooling system also allows the plant to reduce power output dependence on ambient conditions. A 127MW combined cycle power plant operating in the Italian scenario is the object of this investigation. Two different technologies for cool thermal storage have been considered: ice harvester and stratified chilled water. To evaluate the performance of the combined cycle under different operating conditions, inlet cooling systems have been simulated with an in-house developed computational code. An economical analysis has been then performed. Different plant location sites have been considered, with the purpose to weigh up the influence of climatic conditions. Finally, a parametric analysis has been carried out in order to investigate how a variation of the thermal storage size affects the combined cycle performances and the investment profitability. It was found that both cool thermal storage technologies considered perform similarly in terms of gross extra production of energy. Despite this, the ice harvester shows higher parasitic load due to chillers consumptions. Warmer climates of the plant site resulted in a greater increase in the amount of operational hours than power output augmentation; investment profitability is different as well. Results of parametric analysis showed how important the size of inlet cooling storage may be for economical results.

Characteristics of air entrainment during dynamic wetting failure along a planar substrate

2014 ◽  
Vol 747 ◽  
pp. 119-140 ◽  
Author(s):  
E. Vandre ◽  
M. S. Carvalho ◽  
S. Kumar
Keyword(s):  
High Speed ◽  
Water Solution ◽  
Air Entrainment ◽  
Dynamic Contact ◽  
Operating Conditions ◽  
Dynamic Wetting ◽  
Glycerol Water ◽  
Planar Substrate ◽  
Wide Range ◽  
Stationary Plate

AbstractCharacteristic substrate speeds and meniscus shapes associated with the onset of air entrainment are studied during dynamic wetting failure along a planar substrate. Using high-speed video, the behaviour of the dynamic contact line (DCL) is recorded as a tape substrate is drawn through a bath of a glycerol/water solution. Air entrainment is identified by triangular air films that elongate from the DCL above some critical substrate speed. Meniscus confinement within a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a wide range of liquid viscosities, expanding upon the findings of Vandre, Carvalho & Kumar (J. Fluid Mech., vol. 707, 2012, pp. 496–520). A pressurized liquid reservoir controls the meniscus position within the confinement gap. It is found that liquid pressurization further postpones air entrainment when the meniscus is located near a sharp corner along the stationary plate. Meniscus shapes recorded near the DCL demonstrate that operating conditions influence the size of entrained air films, with smaller films appearing in the more viscous solutions. Regardless of size, air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Recorded critical speeds and air-film sizes compare well to predictions from a hydrodynamic model for dynamic wetting failure, suggesting that strong air stresses near the DCL trigger the onset of air entrainment.

Sign in / Sign up

Export Citation Format

Share Document