Effects of Plate Edge Thickness On Droplet Generation Caused by Water Film Breakup At the Plate Edge

2021 ◽  
Author(s):  
Daisuke Ito ◽  
Susumu Nakano ◽  
yu Matsuzaki ◽  
Yoichi Takeda
Keyword(s):  
Droplet Diameter ◽  
Critical Diameter ◽  
Water Film ◽  
Leading Edge ◽  
Steam Turbines ◽  
Airflow Velocity ◽  
Plate Edge ◽  
Frequency Distributions ◽  
Air Flow Velocity ◽  
End Stage

Abstract Droplets generated at trailing edges of low-pressure steam turbines strike the leading edge of moving blades, resulting in severe damage by erosion. In this study, water film flows on a plate set in a parallel airflow and breakup patterns are observed and measured to investigate the breakup behavior of the water film at the plate edge and the effect of the plate edge thickness. Profiles of frequency distribution of the droplet diameters exhibit on approximately linear in a semilog graph. The gradient of those distributions becomes steeper when the air flow velocity increases. Coarse droplets are generated from the deformation of ligaments, as shown in the end stage of a sheet-type breakup, and will result in a secondary breakup. Meanwhile fine droplets whose diameters are similar to the critical diameter remain in the high airflow velocity region; they are assumed to contribute significantly to erosion damage. The plate edge thickness does not affect the frequency distributions of the droplet diameter and Sauter mean diameter. However, it affects the intermittency of discharge water. The discharged water period becomes longer when the plate edge thickness increases. This discharged water frequency is smaller than the wave frequency of the water film flow on the plate when the airflow velocity is high. Based on an experiment involving the highest airflow velocity, the discharged water frequency is similar to that generated by a general turbine rotation speed.

Evaluation on the performance fluctuation after water ingestion for a turbofan engine compressor during flight descent

2020 ◽  
pp. 095441002097798
Author(s):  
Lu Yang ◽  
Qun Zheng ◽  
Aqiang Lin
Keyword(s):  
Droplet Diameter ◽  
Pressure Ratio ◽  
Critical Role ◽  
Water Film ◽  
Heavy Rain ◽  
Diameter Distribution ◽  
Turbofan Engine ◽  
Water Ingestion ◽  
The Core ◽  
Engine Compressor

Turbofan engine compressor is most severely threatened by the entry of liquid water during flight descent. This study aims to deeply understand the fluctuations of compressor performance parameters caused by water ingestion through frequency spectrum analysis. The water content and droplet diameter distribution are determined based on the real heavy rain environment. Results reveal that most of the droplets actually entering the core compressor have a particle size of less than 100 μm. In addition, the formation and motion of water film plays a critical role in affecting the fluctuation characteristics. Water ingestion deteriorates the compression performance and aggravates the unsteady fluctuations of the fan. However, the performance of the core compressor is less affected by water ingestion, but their fluctuations are still exacerbated. For some important parameters, such as inlet mass flow rate, total pressure ratio, total temperature ratio, compression work and efficiency, their main frequency of fluctuation are switched from the original blade passing frequency to the rotor passing frequency, and their amplitudes are correspondingly amplified to varying degrees. These phenomena can be observed in both the fluctuations of the fan and core compressor. Moreover, the operating point of them will be in the long-period and large-amplitude fluctuations, which leads them experiences the non-optimal state for a long time and threatens their operating stability.

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.

Optimizing the Tip Section Profiles of a Steam Turbine Blading

2013 ◽  
Author(s):  
Rudolf Dvořák ◽  
Pavel Šafařík ◽  
Martin Luxa ◽  
David Šimurda
Keyword(s):  
Shock Wave ◽  
Leading Edge ◽  
Optimization Method ◽  
Edge Region ◽  
Steam Turbines ◽  
Shape Modification ◽  
Proper Design ◽  
Last Stage ◽  
Turbine Blading ◽  
Large Output

Though there is not much freedom in shape modification of profiles for tip sections of steam turbines of large output, there is still enough space for optimizing these profiles. The constraints are already in the thermodynamic design of the last stage blading. The layout of the tip cascade indicates that the optimizing strategy should primarily concern the leading edge region and the trailing edge. Proper design can cut down both the front and exit shock wave intensities and the shock wave direct and indirect losses, as well as attenuate the interacting shock waves. This “partial optimization” method has been experimentally verified and is presented in this paper.

scholarly journals Numerical and experimental study of droplet-film-interaction for low pressure steam turbine erosion protection applications

2021 ◽  
Vol 5 ◽  
pp. 90-103
Author(s):  
Dieter Bohn ◽  
Tatsuya Uno ◽  
Takeshi Yoshida ◽  
Christian Betcher ◽  
Jan Frohnheiser ◽  
...  
Keyword(s):  
Water Film ◽  
Low Pressure ◽  
Numerical Approach ◽  
Fluid Film ◽  
Steam Turbines ◽  
Airfoil Surface ◽  
Collection Rate ◽  
Lagrangian Simulation ◽  
Pressure Steam ◽  
Surrounding Fluid

One common approach for anti-erosion measures in low pressure steam turbines is to equip a hollow stator vane with slots on the airfoil surface in order to remove the water film by suction and consequently reduce the amount of secondary droplets. The purpose of this paper is to build an understanding of the predominant effects in fluid-film interaction and to examine the suitability of modern numerical methods for the design process of such slots. The performance of a suction slot in terms of collection rate and air leakage is investigated numerically in a flatplate setup with upstream injection of water. In order to model the relevant phenomena (film transport, edge stripping of droplets, transport of droplets in the surrounding fluid, wall impingement of droplets) an unsteady Eulerian-Lagrangian simulation setup is applied. The accuracy of the numerical approach is assessed by comparison with experimental measurements. The comparison of four cases with the measured data demonstrates that the chosen simulation approach is able to predict the main features of film flow and interaction with the surrounding fluid. The collection rate as well as fluid film properties show the same qualitative dependency from water mass flow rate and air velocity.

Investigation on Flow and Breakdown Characteristics Under Horizontal Shear of Water Film Falling Down Vertical Corrugated Plate Dryer

2018 ◽  
Author(s):  
Bo Wang ◽  
Rui-feng Tian ◽  
Chen Bowen ◽  
Mao Feng
Keyword(s):  
Film Thickness ◽  
Separation Efficiency ◽  
Water Film ◽  
Experimental Result ◽  
Horizontal Shear ◽  
Airflow Velocity ◽  
Water Separation ◽  
Water Film Thickness ◽  
Film Breakdown ◽  
Two Phases

The corrugated plate dryer is a very important equipment for the steam-water separation in the steam generator. Its separation efficiency determines the economic indicators of nuclear power plants. The study of the complicated steam-water separation mechanism of the corrugated plate dryer is very helpful to improve its separation efficiency. Flow and breakdown characteristics under horizontal shear of water film falling down vertical corrugated plate dryer is investigated. Air and water are used as the two phases in the research. This paper also derives a model calculating the critical airflow velocity of water film breakdown and completes the comparison of the experimental result and the result calculated by the model. The relationship between the water film thickness and critical airflow velocity of water film breakdown is investigated through the experiment. In addition, the water film thickness is measured according to CCD high-speed camera acquisition system and the Planar Laser Induced Fluorescence (PLIF) method is also used for the measurement. The experimental result reveals that the critical airflow velocity of water film breakdown is related to the corrugated plate structural parameters, the properties of the two phases and the water film thickness. The critical airflow velocity of water film breakdown and the water film thickness are negatively correlated. The result calculated by the model is in good agreement with the experimental result as the water film thickness is large in a certain range.

Investigation of Hot Film Jet Vortex Effects on Droplets Characteristics Over Aero-Engine Inlet Strut

2016 ◽  
Author(s):  
Yun Zhang ◽  
Peng Ke ◽  
Chunxin Yang ◽  
Guangfeng Yu
Keyword(s):  
Collection Efficiency ◽  
Droplet Diameter ◽  
Rear Surface ◽  
Leading Edge ◽  
Computation Method ◽  
Blowing Ratio ◽  
Impingement Heat Transfer ◽  
Aero Engine ◽  
Hot Film ◽  
Air Film

The jetted hot film could affect the trajectories of the water droplets near the aero-engine inlet strut surface, which equipped with the ice protection system combined the internal impingement heat transfer and the external hot air film heating. To evaluate the droplets impingement characteristics of four ice-protection structures designed with different film-slot jet angles, a droplets impingement computation method based on Eulerian framework was developed and validated. The influences of film-slot angle and blowing ratio on the impingement characteristics for droplet diameter of 20μm were investigated and the jet vortex was found to be an important factor. The results indicated that the local collection efficiency and the impingement limitation could decrease significantly due to the blowing from the external hot-film, and the influence would be more significant in case that the film-slot was closer to the leading edge. For example, the average local collection efficiencies of four typical configurations with different slot angles and positions decreased 82%, 8%, 1% and 0.5% respectively comparing to those without air film. Besides that, the maximum local collection efficiency and the impingement limitation decreased with the increasing blowing ratios, and the film-slot nearest to the leading edge was most sensitive to the blowing ratio. It was also found that no droplets impinged on the rear surface after the jet slots at some higher blowing ratios.

Cooling Performance of the Steam-Cooled Vane in a Steam Turbine Cascade

2005 ◽  
Author(s):  
Dieter Bohn ◽  
Jing Ren ◽  
Karsten Kusterer
Keyword(s):  
Steam Turbine ◽  
Thermal Load ◽  
Leading Edge ◽  
Suction Side ◽  
Live Steam ◽  
Steam Turbines ◽  
Medium Term ◽  
High Thermal Load ◽  
Steam Cooling ◽  
Cooling Technique

With the increasing demand of the electricity, an efficiency improvement and thereby a reduced CO2 emission of the coal-fired plants are expected in order to reach the goal of the Kyoto protocol. In the medium term, increase of thermal efficiency of the steam cycle can be achieved by a rise of the process parameters. Currently, live steam pressures and temperatures up to 300 bar and 923 K are planned as a next step. This means an increase of 50–100 K in comparison to plants presently under operation. Such a large increase will only be possible, if all thermally high loaded components of the plant are made of new materials and/or new technologies for cooling and thermal insulation are applied. Closed circuit steam cooling of blades and vanes in modern steam turbines is a promising technology in order to establish elevated live steam temperatures in future steam turbine cycles. Due to the cooling of the components, materials can be used, which are common in todays application. In this paper, a steam-cooled test vane in a cascade with external hot steam flow is analysed numerically by applying a Conjugate Calculation Technique. The boundary conditions of the hot steam are derived from the planned inlet parameter of the HP steam turbine in a medium term and a long term in order to show the application potential of such a cooling technique. The supply steam parameters of the cooling are set equal to those of the outlet steam from the HP steam turbine. The results show that the steam cooling technique can reach necessary cooling effectiveness in the steam turbine by using only minor amounts of cooling steam. The internal part of the vane is cooled homogeneously in both investigated cases. Basic features and phenomena of the steam cooling technique in steam turbines are discussed in the paper with respect to future application. It has been found that the trailing edge region of the steam-cooled vane is less critical with respect to high thermal load than in gas turbine application with the same configuration. At the leading edge of the vane, high thermal load can be detected because of the direct impingement of the hot steam. Improvement of the leading edge cooling is recommended by increasing cooling steam amount for the leading edge channel. Thus, a larger diameter of the channel can increase internal cooling efficiency for the leading edge. Due to the different heat transfer characteristics on the suction side and pressure side, the suction side shows also a higher temperature distribution in the investigated cases.

Unsteady Flow Field and Coarse Droplet Measurements in the Last Stage of a Low Pressure Steam Turbine With Supersonic Airfoils Near the Blade Tip

2016 ◽  
Author(s):  
Ilias Bosdas ◽  
Michel Mansour ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Shigeki Senoo
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Leading Edge ◽  
Suction Side ◽  
Fast Response ◽  
Operating Conditions ◽  
Electricity Production ◽  
Test Facility ◽  
Steam Turbines ◽  
Last Stage

The largest share of electricity production worldwide belongs to steam turbines. However, the increase of renewable energy production has led steam turbines to operate under part load conditions and increase in size. As a consequence long rotor blades will generate a relative supersonic flow field at the inlet of the last rotor. This paper presents a unique experiment work that focuses at the top 30% of stator exit in the last stage of an LP steam turbine test facility with coarse droplets and high wetness mass fraction under different operating conditions. The measurements were performed with two novel fast response probes. A fast response probe for three dimensional flow field wet steam measurements and an optical backscatter probe for coarse water droplet measurements ranging from 30 up to 110μm in diameter. This study has shown that the attached bow shock at the rotor leading edge is the main source of inter blade row interactions between the stator and rotor of the last stage. In addition, the measurements showed that coarse droplets are present in the entire stator pitch with larger droplets located at the vicinity of the stator’s suction side. Unsteady droplet measurements showed that the coarse water droplets are modulated with the downstream rotor blade-passing period. This set of time-resolved data will be used for in-house CFD code development and validation.

Subsonic Stall Flutter of a Linear Turbine Blade Cascade Using Experimental and CFD Analysis

2020 ◽  
Author(s):  
Vaclav Slama ◽  
Bartolomej Rudas ◽  
Jiri Ira ◽  
Ales Macalka ◽  
Petr Eret ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Separation Bubble ◽  
Turbine Blades ◽  
Leading Edge ◽  
Travelling Wave ◽  
Computational Domain ◽  
Steam Turbines ◽  
Suction Surface ◽  
Blade Cascade ◽  
Stall Flutter

Abstract Stall flutter of long blades influences the operation safety of the large steam turbines in off-design conditions. As angles of attack are typically high, a partial or complete separation of the flow from the blade surface occurs. The prediction of stall flutter of turbine blades is a crucial task in the design and development of modern turbomachinery units and reliable design tools are necessary. In this work, aerodynamic stability of a linear turbine blade cascade is tested experimentally at high angle of attack +15°, Ma = 0.2 and the reduced frequency of 0.38. Controlled flutter testing has been performed in a travelling wave mode approach for the torsion with the motion amplitude of 0.5°. In addition, ANSYS CFX with SST k-ω turbulent model is used for URANS simulations of a full-scale computational domain. A separation bubble formed on suction surface near the leading edge has been found in CFD results for each blade. Excellent agreement between the experimental and numerical results in stability maps has been achieved for this case under investigation. This is encouraging and both experimental and numerical techniques will be tested further.

scholarly journals Numerical Simulation of Airfoil Aerodynamic Penalties and Mechanisms in Heavy Rain

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Zhenlong Wu ◽  
Yihua Cao ◽  
M. Ismail
Keyword(s):  
Boundary Layer ◽  
Water Film ◽  
Leading Edge ◽  
Heavy Rain ◽  
Mathematic Model ◽  
Boundary Layer Separation ◽  
Boundary Layer Transition ◽  
Percentage Increase ◽  
Layer Transition ◽  
Maximum Percentage

Numerical simulations that are conducted on a transport-type airfoil, NACA 64-210, at a Reynolds number of2.6×106and LWC of 25 g/m3explore the aerodynamic penalties and mechanisms that affect airfoil performance in heavy rain conditions. Our simulation results agree well with the experimental data and show significant aerodynamic penalties for the airfoil in heavy rain. The maximum percentage decrease inCLis reached by 13.2% and the maximum percentage increase inCDby 47.6%. Performance degradation in heavy rain at low angles of attack is emulated by an originally creative boundary-layer-tripped technique near the leading edge. Numerical flow visualization technique is used to show premature boundary-layer separation at high angles of attack and the particulate trajectories at various angles of attack. A mathematic model is established to qualitatively study the water film effect on the airfoil geometric changes. All above efforts indicate that two primary mechanisms are accountable for the airfoil aerodynamic penalties. One is to cause premature boundary-layer transition at low AOA and separation at high AOA. The other occurs at times scales consistent with the water film layer, which is thought to alter the airfoil geometry and increase the mass effectively.

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