Erosion of polymer-particle composite coatings by liquid water jets

Gas turbine inlet fog / overspray cooling is considered as a simple and effective method to increase power output. To help understand the water mist transport in the compressor flow passage, this study conducts a computational simulation of wet compression in a single rotor-stator compressor stage using the commercial code, Fluent. A sliding mesh scheme is used to simulate the stator-rotor interaction in a rotating frame. The effect of different heat transfer models and forces (e.g. drags, thermophoretic, Brownian, Saffman’s lift force etc.) are investigated. Models to simulate droplet breakup and coalescence are incorporated to take into consideration the effect of local acceleration and deceleration on water droplet dynamics. Analysis on droplet history (trajectory and size) with stochastic tracking is employed to interpret the mechanism of droplet dynamics under influence of local turbulence, acceleration, diffusion, and body forces. An erosion model is also included. The results show that droplet local slip velocity is noticeably affected by local acceleration and deceleration of the compressor blade, and in turn, the heat transfer and water evaporation rate are affected. Due to the short droplet residence time in the compressor stage, local thermal equilibrium is not always achieved, and the air may not always reach saturation even sufficient amount of liquid mass is in the air. The results also show erosion occurs near the rotor fore-body on the suction side with the present erosion model, which is subject to continuous improvement and further verification. The transient results of different rotor/stator relative positions show low airflow blockage produces more effective compression and higher temperature rise. Different types of droplet boundary conditions show the effect is negligible.

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“…al. [32], who described the erosion from the solid mechanics point of view by elasticity and plasticity. Briscoe et.…”

Section: Erosion Modelmentioning

confidence: 99%

Simulation of Inlet Fogging and Wet-Compression in a Single Stage Compressor Including Erosion Analysis

Khan

Wang

2008

Volume 7: Education; Industrial and Cogeneration; Marine; Oil and Gas Applications

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“…Research also concerns material erosion like steels [7], aluminum [8], copper [9], ceramics [10] and polymers [11] but it seems to not have any source on graphite erosion.…”

Section: Technique Presentationmentioning

confidence: 99%

New Methods for HTR Fuel Waste Management

Guittonneau

Abdelouas

Grambow

et al. 2008

Fourth International Topical Meeting on High Temperature Reactor Technology, Volume 2

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Considering the need to reduce waste production and greenhouse emissions by still keeping high energy efficiency, various 4 th generation nuclear energy systems have been proposed. As far as graphite moderated reactors are concerned, one of the key issues is the large volumes of irradiated graphite encountered (1770 m 3 for fuel elements and 840 m 3 for reflector elements during the lifetime (60 years) of a single reactor module [1]). With the objective to reduce volume of waste in the HTR concept, it is very important to be able to separate the fuel from low level activity graphite. This requires to separate TRISO particles from the graphite matrix with the sine qua non condition to not break TRISO particles in case of future embedding of particles in a matrix for disposal.According to National Regulatory Systems, in case of limited graphite waste production or of short duration HTR projects (e.g. in Germany), direct disposal without separation is acceptable. Nevertheless, in case of large scale deployment of HTR technology, such approach is not economical and sustainable. Previous attempts in graphite management (furnace, fluidised bed and laser incinerations and encapsulation matrices) dealt with graphite matrix only. These are the reasons why we studied the management of irradiated compact-type fuel element. We simulated the presence of fuel in the particles by using ZrO 2 kernels. Compacts with ZrO 2 TRISO particles were manufactured by AREVA NP.Two original methods have been studied. First, we tested high pressure jet to erode graphite and clean TRISO particles. Best erosion rate reached about 0.18 kg/h for a single nose ending. Examination of treated graphite showed a mixture of undamaged TRISO particles, particles that have lost the outer pyrolytic carbon layer and ZrO 2 kernels. Secondly, we studied the thermal shock method by immerging successively graphite into liquid nitrogen and hot water to cause fracturing of the compact. This produced particles and graphite fragments with diameter ranging from several centimetres to less than 500 µm. This relatively simple and economic method may potentially be considered as a pre-treatment step and be coupled with other method(s) before reprocessing and recycling for example.

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“…The rate of flow of momentum in the radial direction is also appreciable, which can promote peeling. Briscoe et al [3] termed this process hydrodynamic flow induced erosion and discussed the experimental study of Kaye [4] as involving the initial 115 penetration of the layer under the jet footprint, followed by removal by the lateral fluid flow.…”

Section: Introductionmentioning

confidence: 99%

Quantitative modelling of the erosive removal of a thin soil deposit by impinging liquid jets

Oevermann¹,

Bhagat²,

Fernandes³

et al. 2019

Wear

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Kaye et al. (1995, Wear, 186-187, 413-420) conducted an experimental investigation of the cleaning of thin soil layers by water jets generated from stationary nozzles of diameter 0.25-2 35 mm and velocities ranging from 6-40 m s -1 . The soil layers were prepared by drying a commercial cleaning suspension on polymethylmethacrylate plates. Several of their data sets have been re-analysed and are shown to fit the 'strong soil' model for cleaning by peeling reported by Bhagat et al. (2017, Food Bioproduct Proc., 102, 31-54). The model is demonstrated to be able to explain the trends in cleaning efficiency observed by Kaye et al. 40 quantitatively, including the transition in efficiency observed at longer times. Kaye et al. also investigated the case of cleaning by a moving nozzle for one set of jet conditions, and reported an increase in cleared area with nozzle velocity. This behaviour is not predicted for the 'strong soil' and the model was modified to incorporate a contribution from the milling action of the jet in its impingent zone. This 'very strong soil' result gave good agreement with the data for 45 the area cleared and the shape of the cleared region. NomenclatureRoman 50 a Radius of cleaned area, [m] ai Radius when cleaning front is first seen, [m] ai* Dimensionless radius when cleaning front is first seen, [-] ax Distance to cleaning front on jet path, [m] A Area of the cleared region, [m 2 ] 55 c1 Lumped parameters, 1 = 10 o 2 3 2 , [m -3 ] c2 Parameter, Eq. [8], [-] c3 Parameter, Eq. [9], [m -3 ] dN Nozzle diameter, [m] E Efficiency factor, [m -1 ] 60 EU Prefactor efficiency, [m -1 ] k' Lumped cleaning rate constant, [m s kg -1 ] L Distance from nozzle to target, [m] ṁ Mass flow rate, [kg s -1 ] M Momentum flow per unit width, [kg s -2 ] 65 p Radial distance to cleaning front, [m] p* Dimensionless radial distance to cleaning front, [-] Q Flow rate leaving nozzle, [m 3 s -1 ] r Radial co-ordinate, [m] rb Boundary layer radius, [m] 70 ro Jet radius, o = 1 2 N [m] Re Reynolds number, defined Re = UodN/µ t Time, [s] ti Induction time, [s] Uo Jet velocity, [m s -1 ] 75 V Jet's traversal velocity, [m s -1 ] WeG Weber number gaseous, defined We = GUo 2 dN/γ WeL Weber number liquid, defined We = LUo 2 dN/γ 80 4 Greek  Angle to direction of nozzle motion, [-] γ Surface tension, [N m -1 ]    Density, [kg m -3 ] µ  Dynamic viscosity, [Pa s] 85 σ Cleaning rate parameter, [m 2 s -1 ] Acronyms PMMA Polymethylmethacrylate RFZ Radial flow zone 90

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Erosion of polymer-particle composite coatings by liquid water jets

Cited by 22 publications

References 10 publications

Simulation of Inlet Fogging and Wet-Compression in a Single Stage Compressor Including Erosion Analysis

Simulation of Inlet Fogging and Wet-Compression in a Single Stage Compressor Including Erosion Analysis

New Methods for HTR Fuel Waste Management

Quantitative modelling of the erosive removal of a thin soil deposit by impinging liquid jets

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