The Experts below are selected from a list of 34350 Experts worldwide ranked by ideXlab platform
Deng Jianxin - One of the best experts on this subject based on the ideXlab platform.
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preparation and performance of functionally graded ceramic Nozzles in sand blasting surface treatments
Industrial Ceramics, 2008Co-Authors: Deng Jianxin, Ding ZeliangAbstract:SiC/(W,Ti)C functionally graded ceramic composites were produced by hot pressing for use as sand-blasting Nozzles, and their microstructure and wear behaviours were examined. The wear resistance of the graded Nozzles and of a stress-free nozzle with the same composition, was assessed by sand blasting surface treatments. Results showed that the surface hardness (nozzle entry zone) of the functionally graded nozzle is greatly improved compared to the homologous stress-free nozzle. The functionally graded nozzle shows higher wear resistance than the homologous stress-free nozzle, and the ceramic nozzle graded both at the entry and at the exit area exhibited higher wear resistance over the one graded only at the entry area.
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wear mechanisms of gradient ceramic Nozzles in abrasive air jet machining
International Journal of Machine Tools & Manufacture, 2007Co-Authors: Deng Jianxin, Wu Fengfang, Zhao JinlongAbstract:The nozzle is the most critical part in abrasive air-jet machining equipment. Ceramics, being with high wear resistance, have great potential as abrasive air-jet nozzle materials. In this paper, a (W,Ti)C/SiC gradient ceramic composite was developed to be used as nozzle material. The erosion wear behavior of the (W,Ti)C/SiC gradient nozzle was investigated and compared with a conventional ceramic nozzle. Results showed that the gradient ceramic Nozzles exhibited an apparent increase in erosion wear resistance over the conventional ceramic Nozzles. The mechanism responsible was found to be that the tensile stresses at the entry region of the nozzle were greatly reduced when compared with the conventional nozzle. This effect may lead to an increase in resistance to fracture, and thus increase the erosion wear resistance of the gradient nozzle. It is indicated that gradient structures in ceramic Nozzles are effective to improve the erosion wear resistance of conventional ceramic Nozzles in abrasive air-jet machining.
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erosion wear mechanisms of coal water slurry cws ceramic Nozzles in industry boilers
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Deng Jianxin, Ding Zeliang, Yuan DonglingAbstract:Abstract Al 2 O 3 /(W, Ti)C ceramic composites were prepared for the use of coal–water–slurry (CWS) Nozzles in industry boilers. The erosion rates of the CWS ceramic Nozzles were measured. Eroded bore surfaces of the Nozzles was examined by scanning electron microscopy. Finite element method (FEM) was used as a means of numerically evaluating temperature, temperature gradient, thermal stress and its distribution inside the ceramic nozzle. Results showed that the primary wear mechanisms of the CWS ceramic nozzle exhibited polishing action in the inner center hole and thermal shock damage with chipping at exit. The temperature, temperature gradient and thermal stress at exit surfaces of the CWS ceramic nozzle were higher than those of other parts of the nozzle. Greater temperature gradient and higher thermal stress were the main reason that caused the failure of the exit surface of the CWS ceramic nozzle.
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erosion wear of boron carbide ceramic Nozzles by abrasive air jets
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Deng JianxinAbstract:Boron carbide Nozzles were produced by hot pressing. The erosion wear of this nozzle caused by abrasive particle impact was investigated by abrasive air-jets. Silica, silicon carbide and alumina powders with different hardness were used as the erodent abrasive particles. Results showed that the hardness of the erodent particles played an important role with respect to the erosion wear of the boron carbide Nozzles. As the hardness of the erodent particles increases, there is a dramatic increase in erosion rate of the Nozzles. The nozzle entrance area suffered from severe abrasive impact under large impact angles, and generated maximum tensile stresses. The wear mechanisms of boron carbide nozzle at this area appeared to be entirely brittle in nature with the evidence of large scale-chipping, and exhibited a brittle fracture induced removal process. While at the nozzle center wall section, most of the particles traveled parallel to the nozzle wall, and showed minimum tensile stresses. The wear mode in this area of the nozzle changed from impact to sliding erosion, and the wear mechanisms appeared to be the lateral cracking owing to a surface fatigue fracture mechanism.
Jonathan B. Freund - One of the best experts on this subject based on the ideXlab platform.
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very near nozzle shear layer turbulence and jet noise
Journal of Fluid Mechanics, 2015Co-Authors: Ryan A Fontaine, Joanna Austin, Gregory S Elliott, Jonathan B. FreundAbstract:One of the principal challenges in the prediction and design of low-noise Nozzles is accounting for the near-nozzle turbulent mixing layers at the high Reynolds numbers of engineering conditions. Even large-eddy simulation is a challenge because the locally largest scales are so small relative to the nozzle diameter. Model-scale experiments likewise typically have relatively thick near-nozzle shear layers, which potentially hampers their applicability to high-Reynolds-number design. To quantify the sensitivity of the far-field sound to nozzle turbulent-shear-layer conditions, a family of diameter $D$ Nozzles is studied in which the exit turbulent boundary layer momentum thickness is varied from $0.0042D$ up to $0.021D$ for otherwise identical flow conditions. Measurements include particle image velocimetry (PIV) to within $0.04D$ of the exit plane and far-field acoustic spectra. The influence of the initial turbulent-shear-layer thickness is pronounced, though it is less significant than the well-known sensitivity of the far-field sound to laminar versus turbulent shear-layer exit conditions. For thicker shear layers, the nominally missing region, where the corresponding thinner shear layer would develop, leads to the noise difference. The nozzle-exit momentum thickness successfully scales the high-frequency radiated sound for Nozzles of different sizes and exhaust conditions. Yet, despite this success, the detailed turbulence statistics show distinct signatures of the different nozzle boundary layers from the different Nozzles. Still, the different nozzle shear-layer thicknesses and shapes have a similar downstream development, which is consistent with a linear stability analysis of the measured velocity profiles.
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very near nozzle shear layer turbulence and jet noise
Journal of Fluid Mechanics, 2015Co-Authors: Ryan A Fontaine, Joanna Austin, Gregory S Elliott, Jonathan B. FreundAbstract:One of the principal challenges in the prediction and design of low-noise Nozzles is accounting for the near-nozzle turbulent mixing layers at the high Reynolds numbers of engineering conditions. Even large-eddy simulation is a challenge because the locally largest scales are so small relative to the nozzle diameter. Model-scale experiments likewise typically have relatively thick near-nozzle shear layers, which potentially hampers their applicability to high-Reynolds-number design. To quantify the sensitivity of the far-field sound to nozzle turbulent-shear-layer conditions, a family of diameter $D$ Nozzles is studied in which the exit turbulent boundary layer momentum thickness is varied from $0.0042D$ up to $0.021D$ for otherwise identical flow conditions. Measurements include particle image velocimetry (PIV) to within $0.04D$ of the exit plane and far-field acoustic spectra. The influence of the initial turbulent-shear-layer thickness is pronounced, though it is less significant than the well-known sensitivity of the far-field sound to laminar versus turbulent shear-layer exit conditions. For thicker shear layers, the nominally missing region, where the corresponding thinner shear layer would develop, leads to the noise difference. The nozzle-exit momentum thickness successfully scales the high-frequency radiated sound for Nozzles of different sizes and exhaust conditions. Yet, despite this success, the detailed turbulence statistics show distinct signatures of the different nozzle boundary layers from the different Nozzles. Still, the different nozzle shear-layer thicknesses and shapes have a similar downstream development, which is consistent with a linear stability analysis of the measured velocity profiles.
Ryan A Fontaine - One of the best experts on this subject based on the ideXlab platform.
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very near nozzle shear layer turbulence and jet noise
Journal of Fluid Mechanics, 2015Co-Authors: Ryan A Fontaine, Joanna Austin, Gregory S Elliott, Jonathan B. FreundAbstract:One of the principal challenges in the prediction and design of low-noise Nozzles is accounting for the near-nozzle turbulent mixing layers at the high Reynolds numbers of engineering conditions. Even large-eddy simulation is a challenge because the locally largest scales are so small relative to the nozzle diameter. Model-scale experiments likewise typically have relatively thick near-nozzle shear layers, which potentially hampers their applicability to high-Reynolds-number design. To quantify the sensitivity of the far-field sound to nozzle turbulent-shear-layer conditions, a family of diameter $D$ Nozzles is studied in which the exit turbulent boundary layer momentum thickness is varied from $0.0042D$ up to $0.021D$ for otherwise identical flow conditions. Measurements include particle image velocimetry (PIV) to within $0.04D$ of the exit plane and far-field acoustic spectra. The influence of the initial turbulent-shear-layer thickness is pronounced, though it is less significant than the well-known sensitivity of the far-field sound to laminar versus turbulent shear-layer exit conditions. For thicker shear layers, the nominally missing region, where the corresponding thinner shear layer would develop, leads to the noise difference. The nozzle-exit momentum thickness successfully scales the high-frequency radiated sound for Nozzles of different sizes and exhaust conditions. Yet, despite this success, the detailed turbulence statistics show distinct signatures of the different nozzle boundary layers from the different Nozzles. Still, the different nozzle shear-layer thicknesses and shapes have a similar downstream development, which is consistent with a linear stability analysis of the measured velocity profiles.
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very near nozzle shear layer turbulence and jet noise
Journal of Fluid Mechanics, 2015Co-Authors: Ryan A Fontaine, Joanna Austin, Gregory S Elliott, Jonathan B. FreundAbstract:One of the principal challenges in the prediction and design of low-noise Nozzles is accounting for the near-nozzle turbulent mixing layers at the high Reynolds numbers of engineering conditions. Even large-eddy simulation is a challenge because the locally largest scales are so small relative to the nozzle diameter. Model-scale experiments likewise typically have relatively thick near-nozzle shear layers, which potentially hampers their applicability to high-Reynolds-number design. To quantify the sensitivity of the far-field sound to nozzle turbulent-shear-layer conditions, a family of diameter $D$ Nozzles is studied in which the exit turbulent boundary layer momentum thickness is varied from $0.0042D$ up to $0.021D$ for otherwise identical flow conditions. Measurements include particle image velocimetry (PIV) to within $0.04D$ of the exit plane and far-field acoustic spectra. The influence of the initial turbulent-shear-layer thickness is pronounced, though it is less significant than the well-known sensitivity of the far-field sound to laminar versus turbulent shear-layer exit conditions. For thicker shear layers, the nominally missing region, where the corresponding thinner shear layer would develop, leads to the noise difference. The nozzle-exit momentum thickness successfully scales the high-frequency radiated sound for Nozzles of different sizes and exhaust conditions. Yet, despite this success, the detailed turbulence statistics show distinct signatures of the different nozzle boundary layers from the different Nozzles. Still, the different nozzle shear-layer thicknesses and shapes have a similar downstream development, which is consistent with a linear stability analysis of the measured velocity profiles.
Zhao Jinlong - One of the best experts on this subject based on the ideXlab platform.
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wear mechanisms of gradient ceramic Nozzles in abrasive air jet machining
International Journal of Machine Tools & Manufacture, 2007Co-Authors: Deng Jianxin, Wu Fengfang, Zhao JinlongAbstract:The nozzle is the most critical part in abrasive air-jet machining equipment. Ceramics, being with high wear resistance, have great potential as abrasive air-jet nozzle materials. In this paper, a (W,Ti)C/SiC gradient ceramic composite was developed to be used as nozzle material. The erosion wear behavior of the (W,Ti)C/SiC gradient nozzle was investigated and compared with a conventional ceramic nozzle. Results showed that the gradient ceramic Nozzles exhibited an apparent increase in erosion wear resistance over the conventional ceramic Nozzles. The mechanism responsible was found to be that the tensile stresses at the entry region of the nozzle were greatly reduced when compared with the conventional nozzle. This effect may lead to an increase in resistance to fracture, and thus increase the erosion wear resistance of the gradient nozzle. It is indicated that gradient structures in ceramic Nozzles are effective to improve the erosion wear resistance of conventional ceramic Nozzles in abrasive air-jet machining.
Gregory S Elliott - One of the best experts on this subject based on the ideXlab platform.
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very near nozzle shear layer turbulence and jet noise
Journal of Fluid Mechanics, 2015Co-Authors: Ryan A Fontaine, Joanna Austin, Gregory S Elliott, Jonathan B. FreundAbstract:One of the principal challenges in the prediction and design of low-noise Nozzles is accounting for the near-nozzle turbulent mixing layers at the high Reynolds numbers of engineering conditions. Even large-eddy simulation is a challenge because the locally largest scales are so small relative to the nozzle diameter. Model-scale experiments likewise typically have relatively thick near-nozzle shear layers, which potentially hampers their applicability to high-Reynolds-number design. To quantify the sensitivity of the far-field sound to nozzle turbulent-shear-layer conditions, a family of diameter $D$ Nozzles is studied in which the exit turbulent boundary layer momentum thickness is varied from $0.0042D$ up to $0.021D$ for otherwise identical flow conditions. Measurements include particle image velocimetry (PIV) to within $0.04D$ of the exit plane and far-field acoustic spectra. The influence of the initial turbulent-shear-layer thickness is pronounced, though it is less significant than the well-known sensitivity of the far-field sound to laminar versus turbulent shear-layer exit conditions. For thicker shear layers, the nominally missing region, where the corresponding thinner shear layer would develop, leads to the noise difference. The nozzle-exit momentum thickness successfully scales the high-frequency radiated sound for Nozzles of different sizes and exhaust conditions. Yet, despite this success, the detailed turbulence statistics show distinct signatures of the different nozzle boundary layers from the different Nozzles. Still, the different nozzle shear-layer thicknesses and shapes have a similar downstream development, which is consistent with a linear stability analysis of the measured velocity profiles.
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very near nozzle shear layer turbulence and jet noise
Journal of Fluid Mechanics, 2015Co-Authors: Ryan A Fontaine, Joanna Austin, Gregory S Elliott, Jonathan B. FreundAbstract:One of the principal challenges in the prediction and design of low-noise Nozzles is accounting for the near-nozzle turbulent mixing layers at the high Reynolds numbers of engineering conditions. Even large-eddy simulation is a challenge because the locally largest scales are so small relative to the nozzle diameter. Model-scale experiments likewise typically have relatively thick near-nozzle shear layers, which potentially hampers their applicability to high-Reynolds-number design. To quantify the sensitivity of the far-field sound to nozzle turbulent-shear-layer conditions, a family of diameter $D$ Nozzles is studied in which the exit turbulent boundary layer momentum thickness is varied from $0.0042D$ up to $0.021D$ for otherwise identical flow conditions. Measurements include particle image velocimetry (PIV) to within $0.04D$ of the exit plane and far-field acoustic spectra. The influence of the initial turbulent-shear-layer thickness is pronounced, though it is less significant than the well-known sensitivity of the far-field sound to laminar versus turbulent shear-layer exit conditions. For thicker shear layers, the nominally missing region, where the corresponding thinner shear layer would develop, leads to the noise difference. The nozzle-exit momentum thickness successfully scales the high-frequency radiated sound for Nozzles of different sizes and exhaust conditions. Yet, despite this success, the detailed turbulence statistics show distinct signatures of the different nozzle boundary layers from the different Nozzles. Still, the different nozzle shear-layer thicknesses and shapes have a similar downstream development, which is consistent with a linear stability analysis of the measured velocity profiles.
