scholarly journals A Numerical Study of the Effect of Particle Size on Particle Deposition on Turbine Vanes and Blades

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110178
Author(s):  
Zhengang Liu ◽  
Weinan Diao ◽  
Zhenxia Liu ◽  
Fei Zhang
Keyword(s):  
Particle Size ◽  
Particle Deposition ◽  
Numerical Study ◽  
Stokes Number ◽  
Capture Efficiency ◽  
Particle Capture ◽  
Factors Affecting ◽  
Pressure Surface ◽  
Deposition Area ◽  
Turbine Vanes

Particle deposition could decrease the aerodynamic performance and cooling efficiency of turbine vanes and blades. The particle motion in the flow and its temperature are two important factors affecting its deposition. The size of the particle influences both its motion and temperature. In this study, the motion of particles with the sizes from 1 to 20 μm in the first stage of a turbine are firstly numerically simulated with the steady method, then the particle deposition on the vanes and blades are numerically simulated with the unsteady method based on the critical viscosity model. It is discovered that the particle deposition on vanes mainly formed near the leading and trailing edge on the pressure surface, and the deposition area expands slowly to the whole pressure surface with the particle size increasing. For the particle deposition on blades, the deposition area moves from the entire pressure surface toward the tip with the particle size increasing due to the effect of rotation. For vanes, the particle capture efficiency increases with the particle size increasing since Stokes number and temperature of the particle both increase with its size. For blades, the particle capture efficiency increases firstly and then decreases with the particle size increasing.

scholarly journals Experimental Study of Sand Particle Deposition on a Film-Cooled Turbine Blade at Different Gas Temperatures and Angles of Attack

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 811 ◽  
Author(s):  
Fei Zhang ◽  
Zhenxia Liu ◽  
Zhengang Liu ◽  
Weinan Diao
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Particle Deposition ◽  
Angle Of Attack ◽  
Large Angle ◽  
Capture Efficiency ◽  
Gas Temperature ◽  
Trailing Edge ◽  
Pressure Surface ◽  
Film Cooling Holes

Particle deposition tests were conducted in a turbine deposition facility with an internally staged single-tube combustor to investigate the individual effect of the gas temperature and angle of attack. Sand particles were seeded to the combustor and deposited on a turbine blade with film-cooling holes at temperatures representative of modern engines. Fuel-air ratios were varied from 0.022 to 0.037 to achieve a gas temperature between 1272 and 1668 K. Results show that capture efficiency increased with increasing gas temperature. A dramatic increase in capture efficiency was noted when gas temperature exceeded the threshold. The deposition formed mostly downstream of the film-cooling holes on the pressure surface, while it concentrated on the suction surface at the trailing edge. Deposition tests at angles of attack between 10° and 40° presented changes in both deposition mass and distribution. The capture efficiency increased with the increase in the angle of attack, and simultaneously the growth rate slowed down. On the blade pressure surface, sand deposition was distributed mainly downstream of the film-cooling holes near the trailing edge in the case of the small angle of attack, while it concentrated on the region around the film-cooling holes near the leading edge, resulting in the partial blockage of holes, in the case of the large angle of attack.

Effects of Temperature and Particle Size on Deposition in Land Based Turbines

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Jared M. Crosby ◽  
Scott Lewis ◽  
Jeffrey P. Bons ◽  
Weiguo Ai ◽  
Thomas H. Fletcher
Keyword(s):  
Particle Size ◽  
Particle Deposition ◽  
Deposition Process ◽  
Capture Efficiency ◽  
Test Series ◽  
Test Facility ◽  
Back Side ◽  
Gas Temperature ◽  
The Third ◽  
Barrier Coating

Four series of tests were performed in an accelerated deposition test facility to study the independent effects of particle size, gas temperature, and metal temperature on ash deposits from two candidate power turbine synfuels (coal and petcoke). The facility matches the gas temperature and velocity of modern first stage high pressure turbine vanes while accelerating the deposition process. Particle size was found to have a significant effect on capture efficiency with larger particles causing significant thermal barrier coating (TBC) spallation during a 4 h accelerated test. In the second series of tests, particle deposition rate was found to decrease with decreasing gas temperature. The threshold gas temperature for deposition was approximately 960°C. In the third and fourth test series, impingement cooling was applied to the back side of the target coupon to simulate internal vane cooling. Capture efficiency was reduced with increasing mass flow of coolant air; however, at low levels of cooling, the deposits attached more tenaciously to the TBC layer. Postexposure analyses of the third test series (scanning electron microscopy and X-ray spectroscopy) show decreasing TBC damage with increased cooling levels.

The Effect of Particle Size and Film Cooling on Nozzle Guide Vane Deposition

2012 ◽  
Author(s):  
C. Bonilla ◽  
J. Webb ◽  
C. Clum ◽  
B. Casaday ◽  
E. Brewer ◽  
...  
Keyword(s):  
Particle Size ◽  
Film Cooling ◽  
Guide Vane ◽  
Stokes Number ◽  
Capture Efficiency ◽  
Test Facility ◽  
Deposit Thickness ◽  
Nozzle Guide Vane ◽  
Effect Of Particle Size ◽  
Nozzle Guide

An accelerated deposition test facility is used to study the effect of particle size and film cooling on deposit roughness, spatial distribution and thickness. Tests were run at gas turbine representative inlet Mach numbers (0.08) and temperatures (1080°C). Deposits were created from a sub-bituminous coal fly ash with mass median diameters from 4 to 16 microns (Stokes numbers ranging from 0.1 to 1.9. Two CFM56-5B nozzle guide vane doublets comprising three full passages and two half passages of flow were utilized as the test articles. Tests were run with three levels of film cooling. The addition of film cooling to the vanes was shown to decrease deposit capture efficiency by as much as a factor of 3 and shift the primary location of deposit buildup to the leading edge coincident with an increased region of positive cooling backflow margin. Video taken during tests noted that film cooling holes with negative backflow margin were primary areas of deposit formation regardless of film cooling percentage. Stokes number was shown to have a marked effect on vane capture efficiency, with the largest Stokes number ash (St = 1.9) approximately 3 times as likely to stick to the vane as the smallest Stokes number ash (St = 0.1). Post test observations on deposit thickness were made using a coordinate measurement machine. Deposit thickness was noted to be reduced with decreasing Stokes number and increased film cooling percentage. Deposit surface roughness falls with particle size but is only weakly dependent on cooling level.

Deposition Velocity and Penetration Efficiency in a Square Channel Using a Lagrangian-Based Modeling Approach

2020 ◽  
Author(s):  
Byung-Hee Choi ◽  
Daniel Orea ◽  
Thien Nguyen ◽  
N. K. Anand ◽  
Yassin Hassan ◽  
...  
Keyword(s):  
Particle Deposition ◽  
Numerical Study ◽  
Numerical Technique ◽  
Deposition Velocity ◽  
Stokes Number ◽  
Department Of Energy ◽  
Main Stream ◽  
Proof Of Concept ◽  
Square Channel ◽  
Lagrangian Framework

Abstract Texas A&M University is working on the development of gas cooled fast reactor cartridge loop under the Department of Energy VTR program. Our research project aims to develop and implement techniques to quantify the transport and deposition of particle inside the cartridge loop. Before the developed techniques are applied in a complicated actual facility, it is essential to verify and validate their performance using numerical simulations and to quantify their uncertainties. This article presents a numerical study of particle transport and deposition in a proof-of-concept facility. The proof-of-concept facility houses a series of three square duct test sections, each of which has a cross-section of 3 in.2 and a length of 24 in., for a combined total length of 72 in. The numerical simulation domain is based on the geometrical dimensions of the experimental facility. The main stream in the channel is solved using the Eulerian turbulence model, and the particle motion is interpreted in the Lagrangian framework. It is assumed that a well-mixed air–particle mixture at a constant temperature is injected into the horizontal channel. Lagrangian simulations of surrogate particles allow us to understand their behavior precisely. The Reynolds stress model is selected to reproduce the secondary flow and the associated secondary drag force. The state-of-the-art Lagrangian approach, in combination with a random walk model coupled with a computational fluid dynamics model, is employed to investigate the behaviors of the surrogate particles within the square channel. Gravitational settling is also considered. The deposition velocity and penetration efficiency are estimated for representing the characteristics of particle deposition in the proof-of-concept facility. Because the conventional method of measuring the deposition velocity is based on the Eulerian framework, it is not suitable for direct adoption in the Lagrangian framework. This study proposes a numerical technique to measure the deposition velocity; this technique can be efficiently used in the Lagrangian framework of the simulation. The results agree well with both our experimental measurements and correlations available in the literature. Using this technique, the correlations for the deposition velocity are established as functions of the normalized channel length, Stokes number, and Reynolds number. Finally, the relationship between the deposition velocity and penetration efficiency is examined, and a correlation is proposed. Consequently, the penetration efficiency can be directly compared with several conventional reference data based on the deposition velocity.

scholarly journals Numerical study of particle capture efficiency in fibrous filter

2017 ◽  
Vol 140 ◽  
pp. 03003 ◽  
Author(s):  
Jianhua Fan ◽  
Franck Lominé ◽  
Mustapha Hellou
Keyword(s):  
Numerical Study ◽  
Capture Efficiency ◽  
Particle Capture ◽  
Fibrous Filter

Numerical Investigation of Deposition Characteristics of Solid CO2 During Choked Flow for CO2 Pipelines

2016 ◽  
Author(s):  
Lin Teng ◽  
Yuxing Li ◽  
Hui Han ◽  
Pengfei Zhao ◽  
Datong Zhang
Keyword(s):  
Particle Size ◽  
Flow Velocity ◽  
Particle Deposition ◽  
Transport Model ◽  
Fluid Dynamic ◽  
Flow Characteristics ◽  
Stokes Number ◽  
Sudden Expansion ◽  
Choked Flow ◽  
Tracking Model

Choke valves are applied to control the pressure in CO2 pipeline. However, the temperature of fluid would drop rapidly because of Joule-Thomson cooling (JTC), which may cause solid CO2 generate and block the pipe. In this work, a three-dimensional Computational Fluid Dynamic (CFD) model, using the Lagrangian method, Reynold’s Stress Transport model (RSM) for turbulence and stochastic tracking model (STM) for particle trajectory, was developed to predict the gas-solid CO2 flow and deposition characteristics downstream pipeline. The model predictions were in good agreement with the experimental data published in the literature. The effects of particle size, flow velocity and pipeline diameter on the fluid-particle flow characteristics were examined. Results showed that the increase in the flow velocity would cause a decrease in particle deposition ratio and there existed the critical particle size that caused the deposition ratio maximum for each velocity. The paper also presents the effects of particle motion on different deposition regions. Moreover, the main deposition region (the sudden expansion region) is the easy to be blocked by the particles. With the increase in pipeline diameter, the particle deposition ratio was decreasing. In addition, it was recommended for Stokes number to avoid 3-8 St.

A numerical study of the particle size distribution of an aerosol undergoing turbulent coagulation

2000 ◽  
Vol 415 ◽  
pp. 45-64 ◽  
Author(s):  
WALTER C. READE ◽  
LANCE R. COLLINS
Keyword(s):  
Particle Size ◽  
Standard Deviation ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Radial Distribution ◽  
Isotropic Turbulence ◽  
Numerical Study ◽  
Functional Dependence ◽  
Stokes Number ◽  
Final Particle

Coagulation and growth of aerosol particles subject to isotropic turbulence has been explored using direct numerical simulations. The computations follow the trajectories of 262 144 initial particles as they are convected by the turbulent flow field. Collision between two parent particles leads to the formation of a new daughter particle with the mass and momentum (but not necessarily the energy) of the parent particles. The initially monodisperse population of particles will develop a size distribution over time that is controlled by the collision dynamics. In an earlier study, Sundaram & Collins (1997) showed that collision rates in isotropic turbulence are controlled by two statistics: (i) the radial distribution of the particles and (ii) the relative velocity probability density function. Their study considered particles that rebound elastically; however, we find that the formula that they derived is equally valid in a coagulating system. However, coagulation alters the numerical values of these statistics from the values they attain for the elastic rebound case. This difference is substantial and must be taken into consideration to properly predict the evolution of the size distribution of a population of particles. The DNS results also show surprising trends in the relative breadth of the particle size distribution. First, in all cases, the standard deviation of the particle size distribution of particles with finite Stokes numbers is much larger than the standard deviation for either the zero-Stokes-number or infinite-Stokes-number limits. Secondly, for particles with small initial Stokes numbers, the standard deviation of the final particle size distribution decreases with increasing initial particle size; however, the opposite trend is observed for particles with slightly larger initial Stokes numbers. An explanation for these phenomena can be found by carefully examining the functional dependence of the radial distribution function on the particle size and Stokes number.

Flow and Deposition Characteristics Following Chokes for Pressurized CO2 Pipelines

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Lin Teng ◽  
Yuxing Li ◽  
Hui Han ◽  
Pengfei Zhao ◽  
Datong Zhang
Keyword(s):  
Particle Size ◽  
Flow Velocity ◽  
Particle Deposition ◽  
Transport Model ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Stokes Number ◽  
Sudden Expansion ◽  
Tracking Model ◽  
Good Agreement

The relieving system using the choke valve is applied to control the pressure in CO2 pipeline. However, the temperature of fluid would drop rapidly because of Joule–Thomson cooling (JTC), which may cause solid CO2 form and block the pipe. A three-dimensional (3D) computational fluid dynamic (CFD) model considering the phase transition and turbulence was developed to predict the fluid-particle flow and deposition characteristics. The Lagrangian method, Reynold's stress transport model (RSM) for turbulence, and stochastic tracking model (STM) were used. The results show that the model predictions were in good agreement with the experimental data published. The effects of particle size, flow velocity, and pipeline diameter were analyzed. It was found that the increase of the flow velocity would cause the decrease of particle deposition ratio and there existed the critical particle size that causes the deposition ratio maximum. It also presents the four types of particle motions corresponding to the four deposition regions. Moreover, the sudden expansion region is the easiest to be blocked by the particles. In addition, the Stokes number had an effect on the deposition ratio and it was recommended for Stokes number to avoid 3–8 St.

scholarly journals Density-ratio effects on the capture of suspended particles in aquatic systems

2015 ◽  
Vol 783 ◽  
pp. 191-210 ◽  
Author(s):  
Alexis Espinosa-Gayosso ◽  
Marco Ghisalberti ◽  
Gregory N. Ivey ◽  
Nicole L. Jones
Keyword(s):  
Aquatic Vegetation ◽  
Particle Density ◽  
Density Ratio ◽  
Stokes Number ◽  
Critical Value ◽  
Suspended Particles ◽  
Capture Efficiency ◽  
Aquatic Systems ◽  
Sediment Type ◽  
Particle Capture

Particle capture, whereby suspended particles contact and adhere to a solid surface (a ‘collector’), is important in a range of environmental processes, including suspension feeding by corals and ‘filtering’ by aquatic vegetation. Although aquatic particles are often considered as perfect tracers when estimating capture efficiency, the particle density ratio (${\it\rho}^{+}$) – the ratio of the particle density to the fluid density – can significantly affect capture. In this paper, we use a numerical analysis of particle trajectories to quantify the influence of ${\it\rho}^{+}$ on particle capture by circular collectors in a parameter space relevant to aquatic systems. As it is generally believed that inertia augments the capture efficiency when the Stokes number ($\mathit{St}$) of the particles exceeds a critical value, we first estimate the critical Stokes number for aquatic-type particles and demonstrate its dependence on both ${\it\rho}^{+}$ and the Reynolds number ($\mathit{Re}$). Second, we analyse how efficiently circular collectors can capture neutrally buoyant (${\it\rho}^{+}=1$), sediment-type (${\it\rho}^{+}=2.6$) and weakly buoyant (${\it\rho}^{+}=0.9$) aquatic particles. Our analysis shows that, for ${\it\rho}^{+}>1$, inertia can either augment or diminish capture efficiency, and inertial effects appear well before the critical Stokes number is reached. The role of particle inertia is maximised at Stokes numbers above the critical value and, for sediment-type particles, can result in as much as a fourfold increase in the rate of capture relative to perfect tracers of the same size. Similar but opposite effects are observed for weakly buoyant particles, where capture efficiency can decrease by 60 % relative to the capture of perfect tracers.

The Effect of Particle Size and Film Cooling on Nozzle Guide Vane Deposition

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
C. Bonilla ◽  
J. Webb ◽  
C. Clum ◽  
B. Casaday ◽  
E. Brewer ◽  
...  
Keyword(s):  
Particle Size ◽  
Film Cooling ◽  
Guide Vane ◽  
Stokes Number ◽  
Capture Efficiency ◽  
Test Facility ◽  
Deposit Thickness ◽  
Nozzle Guide Vane ◽  
Effect Of Particle Size ◽  
Nozzle Guide

An accelerated deposition test facility is used to study the effect of particle size and film cooling on deposit roughness, spatial distribution, and thickness. Tests were run at gas turbine representative inlet Mach numbers (0.08) and temperatures (1080 °C). Deposits were created from a subbituminous coal fly ash with mass median diameters from 4 to 16 micron (Stokes numbers ranging from 0.1 to 1.9). Two CFM56-5B nozzle guide vane doublets comprising three full passages and two half passages of flow were utilized as the test articles. Tests were run with three levels of film cooling. The addition of film cooling to the vanes was shown to decrease the deposit capture efficiency by as much as a factor of 3 and shift the primary location of deposit buildup to the leading edge, coincident with an increased region of positive cooling backflow margin. Video taken during the tests noted that film cooling holes with a negative backflow margin were primary areas of deposit formation, regardless of the film cooling percentage. The Stokes number was shown to have a marked effect on the vane capture efficiency, with the largest Stokes number ash (St = 1.9) approximately 3 times as likely to stick to the vane as the smallest Stokes number ash (St = 0.1). Posttest observations on the deposit thickness were made using a coordinate measurement machine. The deposit thickness was noted to be reduced with a decreasing Stokes number and an increased film cooling percentage. The deposit surface roughness falls with particle size but is only weakly dependent on the cooling level.

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