Influence of Oxide Particle Size on the Erosion of the Control Stage Nozzle in a Supercritical Steam Turbine

2013 ◽  
Author(s):  
Liu-xi Cai ◽  
Shun-sen Wang ◽  
Lei Zhang ◽  
Jing-ru Mao ◽  
Zhen-ping Feng ◽  
...  
Keyword(s):  
Particle Size ◽  
Steam Turbine ◽  
Erosion Resistance ◽  
Size Range ◽  
Small Particles ◽  
Suction Surface ◽  
Erosion Damage ◽  
Pressure Surface ◽  
Control Stage ◽  
Large Particles

Reducing the solid particle erosion (SPE) of blades is one of the most important problems for high-parameter steam turbine. Based on the erosion rate models and the particle rebound models of blade materials obtained through the accelerated erosion test under high temperature, a lot of three dimension numerical simulations were conducted in this paper. The influence of particle size on the impingement point distribution on the nozzle surface and the erosion characteristics of control stage nozzle in a supercritical steam turbine were analyzed quantitatively. The size range of the oxide scale particles participating in the erosion damage were extended to 500μm, and some special anti-erosion measures corresponding to different size particles were proposed to reduce the erosion of nozzle. Results show that the erosion of pressure surface in the trailing edge of nozzle is mainly from the high-intensity impingement of particles smaller than 160μm, especially those with the size range from 20μm to 60μm. For the impingement of these small particles, optimizing the profile and cascade structure as well as coating the hard coating on the surface of nozzle can improve the erosion resistance of nozzle. However, these small particles do not impinge the nozzle trailing edge suction surface. The severe erosion damage of suction surface of nozzle was from the impingement again of the particles with the size range from 200μm to 500μm after rebounding from nozzle pressure surface. It is very difficult to resist the erosion damage of these large particles for the hard coating, and separating large particles from main steam before entering the nozzle chamber should be a good choice for improving the erosion resistance of turbine. These studies will provide a technical basis for selecting anti-erosion measures of control stage nozzle.

Study of Erosion Characteristics of Solid Particles in the First Reheat Stage Blades of a Supercritical Steam Turbine

2014 ◽  
Author(s):  
Liu-xi Cai ◽  
Shun-sen Wang ◽  
Juan Di ◽  
Jing-ru Mao ◽  
Zhen-ping Feng ◽  
...  
Keyword(s):  
Weight Loss ◽  
Particle Size ◽  
Steam Turbine ◽  
Size Distribution ◽  
Particle Erosion ◽  
Suction Surface ◽  
Erosion Damage ◽  
Rotating Blades ◽  
Pressure Surface ◽  
Axial Clearance

Reducing solid particle erosion (SPE) of blades is one of the most urgent problems for supercritical steam turbine power generation technology. Based on the erosion rate models and the particle rebound models of blade materials obtained through the accelerated erosion test under high temperature, erosion characteristics of the first reheat stage blades in a supercritical steam turbine was simulated and analyzed by three-dimension numerical simulation method in this paper. The influence of operating conditions, particle size distribution in the inlet of nozzle and axial clearance between vanes and rotating blades on the erosion distribution of cascade were explored quantitatively. Results show that: the erosion damage of the first-reheat stage stator is mainly caused by suction surface impingement from oxide particles. In designed loading condition, small and median size of particles mainly eroded the trailing edge (TE) of nozzle pressure surface, while large particles mainly impinge the leading edge (LE) of rotating blades and the TE of vane suction surface, and erosion increase along the blade height. When the turbine is running under part-load condition, particle impingement angle on stator pressure surface is basically unchanged, while impingement velocity slightly reduced. However, the amount of particles that impinge the stator TE suction side after their first-time impingement on rotor LE increase rapidly, leading to the more severe erosion damage of stator suction surface. The particle size distribution in the inlet of nozzle has a significant effect on the erosion simulation of first reheat stage blades, and the size distribution sampled in one unit may not be used to other units. When axial clearance changes, the erosion weight loss of vane pressure surface near TE is basically held constant, while the erosion weight loss in vane suction surface near TE decreases with the increase of axial clearance. For the supercritical 600MW unit simulated in this article, the anti-SPE performance and the unit efficiency can be balanced well when the axial clearance increases to 13mm. The results in this paper will provide a technology basis for reducing oxide particle erosion in the first reheat stage blades of supercritical steam turbine.

Study on Erosion Characteristics of Solid Particles in the First Reheat Stage Blades of a Supercritical Steam Turbine

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Liu-xi Cai ◽  
Shun-sen Wang ◽  
Jing-ru Mao ◽  
Juan Di ◽  
Zhen-ping Feng ◽  
...  
Keyword(s):  
Weight Loss ◽  
Particle Size ◽  
Steam Turbine ◽  
Size Distribution ◽  
Particle Erosion ◽  
Suction Surface ◽  
Erosion Damage ◽  
Rotating Blades ◽  
Pressure Surface ◽  
Axial Clearance

Reducing solid particle erosion (SPE) of blades is one of the most urgent problems for supercritical steam turbine power generation technology. Based on the erosion rate models and the particle rebound models of blade materials obtained through the accelerated erosion test under high temperature, erosion characteristics of the first reheat stage blades in a supercritical steam turbine was simulated and analyzed by three-dimensional numerical simulation method in this paper. The influence of operating conditions, particle size distribution in the inlet of nozzle, and axial clearance between vanes and rotating blades on the erosion distribution of cascade were explored quantitatively. Results show that the erosion damage of the first-reheat stage stator is mainly caused by suction surface impingement from oxide particles. In designed loading condition, small and medium size of particles mainly eroded the trailing edge (TE) of nozzle pressure surface, while large particles mainly impinge the leading edge (LE) of rotating blades and the TE of vane suction surface, and erosion increase along the blade height. When the turbine is running under part-load condition, particle impingement angle on stator pressure surface is basically unchanged, while impingement velocity slightly reduced. However, the amount of particles that impinge the stator TE suction side after their first-time impingement on rotor LE increase rapidly, leading to the more severe erosion damage of stator suction surface. The particle size distribution in the inlet of nozzle has a significant effect on the erosion simulation of first reheat stage blades, and the size distribution sampled in one unit may not be used to other units. When axial clearance changes, the erosion weight loss of vane pressure surface near TE is basically held constant, while the erosion weight loss in vane suction surface near TE decreases with the increase of axial clearance. For the supercritical 600 MW unit simulated in this article, the antiSPE performance and the unit efficiency can be balanced well when the axial clearance increases to 13 mm. The results in this paper will provide a technology basis for reducing oxide particle erosion in the first reheat stage blades of supercritical steam turbine.

Investigation on the arc erosion behavior of new silver matrix composites: Part I. Reinforced by particles

2003 ◽  
Vol 18 (4) ◽  
pp. 804-816 ◽  
Author(s):  
Shou-Yi Chang ◽  
Chia-Jung Hsu ◽  
Cher-Hao Hsu ◽  
Su-Jien Lin
Keyword(s):  
Particle Size ◽  
Erosion Resistance ◽  
High Viscosity ◽  
Matrix Composites ◽  
Particle Content ◽  
Arc Erosion ◽  
Erosion Behavior ◽  
Surface Areas ◽  
Large Particles ◽  
Silver Matrix

Static-gap, single-spark tests were used to investigate the arc erosion behavior of newly developed silicon carbide and alumina particle reinforced silver matrix composites (SiCp/Ag, Al2O3p/Ag). Craters and hills exist on the surfaces of eroded silver matrix composites, and their depths and sizes decrease as the particle content increases and the particle size decreases. Obvious melting, flow, severe splash of molten silver, and the segregation of particles are present on the surfaces of eroded composites containing low volume percents of large particles. Easier silver flow results in smooth surfaces and reduces the total surface areas of the eroded composites containing large particles. The flow and splash of silver decreased with increasing particle content and decreasing particle size, exhibiting a better erosion resistance to single-spark tests. The static-gap, single-spark erosion behavior of silver matrix composites is dominated by the flow and splash of molten composites. A high viscosity of the liquids provides the composites a good arc erosion resistance.

The Relationship Between Colliery-waste Particle Sizes and Plant Growth

1974 ◽  
Vol 1 (4) ◽  
pp. 281-284 ◽  
Author(s):  
Christopher G. Down
Keyword(s):  
Particle Size ◽  
Plant Growth ◽  
Water Retention ◽  
Size Range ◽  
Growth Period ◽  
Dry Weight ◽  
Particle Sizes ◽  
Small Particles ◽  
The Relationship ◽  
Water Holding

Seed germination and dry-weight production in Lolium perenne were examined in relation to growth on 12-years-old colliery waste separated into seven size-fractions. The size-range was from more than 4,000 μ to less than 125 μ, and the growth period was up to 30 days. Germination percentages after 6 days generally increased with decreasing particle-size, as did dry-weight. Shoot : root ratios also showed an inverse relationship with particle size.After 30 days there was no distinction between dryweights on different particle sizes, except that on the largest fractions it had been found impossible to keep the plants alive. Problems of water-holding capacity are discussed, and the significance of soil particle-size in revegetation work is examined, it being concluded that an admixture of small particles is important for water retention and plant growth.

Studies of cattle and sheep eating leaf and stem fractions of grasses. 3. The retention time in the rumen of large feed particles

1981 ◽  
Vol 32 (1) ◽  
pp. 123 ◽  
Author(s):  
DP Poppi ◽  
DJ Minson ◽  
JH Ternouth
Keyword(s):  
Particle Size ◽  
Retention Time ◽  
Dry Matter ◽  
Simulation Studies ◽  
Small Particles ◽  
Dry Matter Distribution ◽  
Rhodes Grass ◽  
Large Particles ◽  
Voluntary Intake ◽  
Cattle And Sheep

Pangola grass (Digitavia decumbens) and Rhodes grass (Chlovis gayana) cut as 6 and 12 week regrowths were separated into leaf and stem fractions and fed ad libitum to four cattle and eight sheep fitted with ruminal fistulae to determine the importance of particle size in controlling the retention time of feed in the rumeno-reticulum (rumen). Particle size was determined by using a wet sieving technique, and based on the cumulative dry matter distribution on the sieves of faeces from cattle and sheep; all particles >1.18 mm were described as large particles. The proportion of large particles was measured in the chopped diet offered, the masticated diet, the ruminal contents and the faeces. Chopped leaf and stem fractions contained 0.85 and 0.86 g/g large particles respectively. Mastication by cattle reduced the proportion of large particles in leaf and stem to 0.58 and 0.76 (P < 0.01), and mastication by sheep to 0.56 and 0.67 (P < 0.01). The proportion of large particles in the rumen of sheep was 0.236 and 0.249 for leaf and stem respectively (P > 0.05) and in cattle 0.272 and 0.345 (P < 0.05). The faeces contained relatively few large feed particles (< 0.045 for cattle and <0.018 for sheep). Cattle eating leaf and stem produced faeces containing 0.027 and 0.040 (g/g) large particles (P <0.05), compared with only 0,008 and 0.013 (P < 0.05) in sheep. Most of the large particles entering the rumen in the masticated feed disappeared in the rumen by breakdown to smaller particles or by digestion. In cattle the proportions that disappeared were 0.978 and 0.976 (P > 0.05) for leaf and stem, and in sheep 0.993 and 0.991 (P > 0.05). Large particles in leaf and stem were retained in the rumen of the sheep for 11.0 and 11.7 h (P > 0.05). Cattle retained large particles in all diets for a longer time (P < 0.01); 16.1 h for leaf and 20,2 h for stem (P > 0.05). Differences in retention time of large particles in the rumen did not appear to be the only factor controlling the retention of dry matter in the rumen and voluntary intake. A model was developed to describe the flow of large and small particles through the rumen. Intake simulation studies indicated that the most important factor influencing dry matter retention time in the rumen was the retention time of small particles (> 1.18 mm). Changes in the rate of breakdown of large particles had a small effect on dry matter retention time.

The Infrared Analysis of Polyethylene Terephthalate Fibers and of Their Strength as Related to Sample Preparation and to Particle Size

1989 ◽  
Vol 43 (5) ◽  
pp. 791-794 ◽  
Author(s):  
R. O. Carter ◽  
K. R. Carduner ◽  
M. C. Paputa Peck ◽  
D. H. Motry
Keyword(s):  
Particle Size ◽  
Sample Preparation ◽  
Polyethylene Terephthalate ◽  
Infrared Analysis ◽  
Spectral Features ◽  
Band Broadening ◽  
Small Particles ◽  
Large Particles ◽  
Local Sample ◽  
Infrared Microscope

An explanation is presented for the broadening of intense spectral features observed in the infrared spectra of polyethylene terephthalate fibers prepared as KBr pellets. Since band broadening occurs in the spectra of stronger, undegraded fiber, it is proposed that, the stronger the fiber, the more the difficulty one has in pulverizing the sample. Larger particles result from undegraded polyester, which lead to broader bands for intense features. The local sample pathlength in the region of the large particles is greater than that for small particles, which can be more homogeneously mixed. Fiber samples can also be presented to an infrared microscope either “as is” or flattened. Striking differences exist between spectra for flattened and round fibers that were otherwise similar.

scholarly journals Stable solutions of a scalar conservation law for particle-size segregation in dense granular avalanches

2008 ◽  
Vol 19 (1) ◽  
pp. 61-86 ◽  
Author(s):  
M. SHEARER ◽  
J. M. N. T. GRAY ◽  
A. R. THORNTON
Keyword(s):  
Particle Size ◽  
Free Surface ◽  
Shear Flow ◽  
Free Surface Flows ◽  
Size Segregation ◽  
Small Particles ◽  
Surface Flows ◽  
Scalar Conservation Law ◽  
Large Particles ◽  
Scalar Conservation

Dense, dry granular avalanches are very efficient at sorting the larger particles towards the free surface of the flow, and finer grains towards the base, through the combined processes of kinetic sieving and squeeze expulsion. This generates an inversely graded particle-size distribution, which is fundamental to a variety of pattern formation mechanisms, as well as subtle size-mobility feedback effects, leading to the formation of coarse-grained lateral levees that create channels in geophysical flows, enhancing their run-out. In this paper we investigate some of the properties of a recent model [Gray, J. M. N. T. & Thornton, A. R. (2005) A theory for particle size segregation in shallow granular free-surface flows. Proc. R. Soc. 461, 1447–1473]; [Thornton, A. R., Gray, J. M. N. T. & Hogg, A. J. (2006) A three-phase mixture theory for particle size segregation in shallow granular free-surface flows. J. Fluid. Mech. 550, 1–25] for the segregation of particles of two sizes but the same density in a shear flow typical of shallow avalanches. The model is a scalar conservation law in space and time, for the volume fraction of smaller particles, with non-constant coefficients depending on depth within the avalanche. It is proved that for steady flow from an inlet, complete segregation occurs beyond a certain finite distance down the slope, no matter what the mixture at the inlet. In time-dependent flow, dynamic shock waves can develop; they are interfaces separating different mixes of particles. Shock waves are shown to be stable if and only if there is a greater concentration of large particles above the interface than below. Constructions with shocks and rarefaction waves are demonstrated on a pair of physically relevant initial boundary value problems, in which a region of all small particles is penetrated from the inlet by either a uniform mixture of particles or by a layer of small particles over a layer of large particles. In both cases, and under a linear shear flow, solutions are constructed for all time and shown to have similar structure for all choices of parameters.

Inkjet printable silver dispersions: Effect of bimodal particle-size distribution on film formation and electrical conductivity

2010 ◽  
Vol 25 (5) ◽  
pp. 821-827 ◽  
Author(s):  
Krishna Balantrapu ◽  
Meaghan McMurran ◽  
Dan V. Goia
Keyword(s):  
Electrical Conductivity ◽  
Particle Size ◽  
Size Distribution ◽  
Film Formation ◽  
Small Particles ◽  
Silver Films ◽  
On Demand ◽  
Drop On Demand ◽  
Large Particles ◽  
Effect Of Particle Size

Inks containing silver nanoparticles of 12 nm, 80 nm, and a 15%/85% mixture of the two sizes were used to evaluate the effect of particle size and size distribution on the electrical properties of sintered films. The silver layers deposited with a “drop-on-demand” inkjet printer were heated at temperatures ranging from 125 to 200 °C. The small particles formed less resistive films at 125 °C, while the larger ones provided better electrical conductivity above 150 °C. The inks containing mixed small and large particles yielded the most conductive silver films over the entire investigated temperature range. A mechanism explaining these results is proposed based on the evolution of film microstructure with temperature.

Flow-induced segregation in confined multicomponent suspensions: effects of particle size and rigidity

2013 ◽  
Vol 738 ◽  
pp. 423-462 ◽  
Author(s):  
Amit Kumar ◽  
Rafael G. Henríquez Rivera ◽  
Michael D. Graham
Keyword(s):  
Particle Size ◽  
Master Equation ◽  
Migration Velocity ◽  
Equation Model ◽  
Simple Shear Flow ◽  
Small Particles ◽  
Large Particles ◽  
Dilute Suspensions ◽  
Normal Particle ◽  
Non Local

AbstractThe effects of particle size and rigidity on segregation behaviour in confined simple shear flow of binary suspensions of fluid-filled elastic capsules are investigated in a model system that resembles blood. We study this problem with direct simulations as well as with a master equation model that incorporates two key sources of wall-normal particle transport: wall-induced migration and hydrodynamic pair collisions. The simulation results indicate that, in a mixture of large and small particles with equal capillary numbers, the small particles marginate, while the large particles antimarginate in their respective dilute suspensions. Here margination refers to localization of particles near walls, while antimargination refers to the opposite. In a mixture of particles with equal size and unequal capillary number, the stiffer particles marginate while the flexible particles antimarginate. The master equation model traces the origins of the segregation behaviour to the size and rigidity dependence of the wall-induced migration velocity and of the cross-stream particle displacements in various types of collisions. In particular, segregation by rigidity, especially at low volume fractions, is driven in large part by heterogeneous collisions, in which the stiff particle undergoes larger displacement. In contrast, segregation by size is driven mostly by the larger wall-induced migration velocity of larger particles. Additionally, a non-local drift-diffusion equation is derived from the master equation model, which provides further insights into the segregation behaviour.

scholarly journals Studies on respiratory infection: II. The influence of aerosol particle size on infection of the guinea-pig with Pasteurella pestis

1956 ◽  
Vol 54 (1) ◽  
pp. 37-48 ◽  
Author(s):  
H. A. Druett ◽  
J. M. Robinson ◽  
D. W. Henderson ◽  
L. Packman ◽  
S. Peacock
Keyword(s):  
Particle Size ◽  
Guinea Pig ◽  
Respiratory Tract ◽  
Respiratory Infection ◽  
Cross Infection ◽  
Airborne Particles ◽  
Small Particles ◽  
Large Particles ◽  
Aerosol Particle Size ◽  
Disease Characteristic

The LD50 dose of Past. pestis is much greater when tested by the respiratory route than by subcutaneous challenge. This is probably due to trauma inflicted on the airborne particles.Two forms of plague, both originating in the respiratory tract of the guinea-pig, can develop according to the size of the particle containing Past. pestis presented to the host. Small particles initiate a broncho-pneumonia which leads to septicaemia and death. Large particles establish a septicaemia, and death results more quickly without the development of a pneumonia.Cross-infection to normal animals occurs irregularly when they are exposed to others developing plague by the respiratory route. Such incident is rare when the initially infected animals are exposed to large particles. Cross-infected animals suffer from the disease characteristic of exposure to large particles. Attempts to establish an epizootic by cross-respiratory infection were abortive, probably due, in some measure, to the type of disease developing in first cross-infections.

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