An experiment on critical flow of water was conducted in two nozzles of 1.41 mm in diameter and 4.35 mm in length with rounded-edge and sharp-edge respectively, covering the ranges of inlet pressure of 22.1-29.1 MPa a...An experiment on critical flow of water was conducted in two nozzles of 1.41 mm in diameter and 4.35 mm in length with rounded-edge and sharp-edge respectively, covering the ranges of inlet pressure of 22.1-29.1 MPa and inlet temperature of 38-474 ℃. More than 200 data points were obtained and the characteristics and parametric trends were investigated. In the region of near and beyond pseudo-critical temperature the thermal-equilibrium is dominant, and the flow rate can be estimated by the modified homogeneous equilibrium model. In the below pseudo-critical region the results exhibit scattered feature as a result of hysteresis effect in the onset of vaporization, characterizing a bifurcation behavior. This effect is more significant in the nozzle with sharp-edge, especially at higher pressure. For temperature well below the pseudo-critical point, the flow is not at critical condition and the flow rate can be represented by the Bernoulli equation reasonably.展开更多
Nosing process of circular metal tubes in empty and polyurethane foam-filled conditions on a semispherical rigid die was analyzed by theoretical and experimental methods.A new theoretical model of plastic deformation ...Nosing process of circular metal tubes in empty and polyurethane foam-filled conditions on a semispherical rigid die was analyzed by theoretical and experimental methods.A new theoretical model of plastic deformation of circular metal tubes was demonstrated during the nosing process on a rigid semispherical die.Based on the analytical model,some theoretical relations were calculated to estimate instantaneous forming load and dissipated energy of empty and foam-filled circular metal tubes versus axial displacement.Some circular brazen and aluminum tubes were prepared and shaped into semispherical nosed nozzles to verify the present theory.Comparison of theoretical predictions and the corresponding experimental measurements reveals that predicted load?displacement and dissipated energy?displacement diagrams by theoretical formulas have a good correlation with the corresponding experimental curves and it proves verity of the theory.Also,the present theory shows that dissipated energy and axial load of empty tubes depend on material type,wall thickness and diameter of the tubes and they are independent of tube initial length.Furthermore,the experimental results show that the presence of polyethylene Teflon-constraints increases ultimate axial displacement of the forming process.展开更多
This paper studies the influence of feed injection on the hydrodynamic behavior of fluid catalytic cracking riser reactors. Experiments were conducted in a cold model of 186 mm ID with two oppositely inclined secondar...This paper studies the influence of feed injection on the hydrodynamic behavior of fluid catalytic cracking riser reactors. Experiments were conducted in a cold model of 186 mm ID with two oppositely inclined secondary air feed nozzles. The flow structure was determined by means of the axial static pressure measurements and local radial optic fiber probe measurements on different levels with emphasis on the sections downstream of the secondary injection. The measurements reveal that the secondary injection plays a crucial role on riser hydrodynamics. Just above the secondary injection, the flow and mixing are strongly affected, while below the secondary injection the effect is weak. The radial profile just downstream of secondary injection demonstrates wavy features. The effective region of secondary injection could be estimated by the axial pressure gradient profiles and/or the radial profiles of local solids velocity and density.展开更多
Pulsed electrohydrodynamic printing （EHDP） is used to fabricate conductive silver patterns with micrometer resolution. The silver ink pendant experiences swelling, pulsation, and ejection under an applied pulse volt...Pulsed electrohydrodynamic printing （EHDP） is used to fabricate conductive silver patterns with micrometer resolution. The silver ink pendant experiences swelling, pulsation, and ejection under an applied pulse voltage of 20 Hz. The droplet deposi- tion frequency is equal to the applied voltage frequency so that the EHDP can deposit silver ink on demand. A low applied voltage favors uniform and non-scattering silver patterns while a high applied voltage results in ink scattering. Discrete drop- lets with 45-55 gm in diameter and continuous tracks with 60 gm in width are generated by using a ll0-i.tm-cailber nozzle. The feature size of deposited patterns is about half of the nozzle caliber, and a finer resolution can be achieved with the intro- duction of smaller nozzle calibers. Furthermore, the appropriate curing condition is investigated for sufficient combustion of ink solvent. The minimum resistivity of 3.3 gf~ cm is demonstrated for a continuous track cured at 200~C for 10 min. Eventu- ally, several passive electrical components, such as coated resistors, interdigitated capacitors （6 pF）, and spiral inductors （0.6 gH）, are successfully fabricated.展开更多
Cold spray is a technique to make a coating on a wide variety of mechanical or electric parts by spraying solid particles accelerated through a high-speed gas flow in a converging-diverging nozzle. In this study, pseu...Cold spray is a technique to make a coating on a wide variety of mechanical or electric parts by spraying solid particles accelerated through a high-speed gas flow in a converging-diverging nozzle. In this study, pseudo-shock waves in a modeled cold spray nozzle as well as high-speed gas jets are visualized by schlieren technique. The schlieren photographs reveals the supersonic flow with shock train in the nozzle. Static pressure along the barrel wall is also measured. The location of the head of pseudo-shock wave and its pressure distribution along the nozzle wall are analytically explained by using a formula of pseudo-shock wave. The analytical results show that the supersonic flow accompanying shock wave in the nozzle should be treated as pseudo-shock wave instead of normal shock wave.展开更多
This paper deals mainly with pneumatic measurements on a radial turbine nozzle cascade. The fill radial cascade guarantees the exit flow field periodicity downstream of it. A special traversing mechanism with a five -...This paper deals mainly with pneumatic measurements on a radial turbine nozzle cascade. The fill radial cascade guarantees the exit flow field periodicity downstream of it. A special traversing mechanism with a five - hole conical probe moving along a circular path behind the cascade was used for flow field investigation in this type of cascade with very low aspect ratio. The analyses of results of 2D and 3D pneumatic measurements including loss coefficient values are presented.展开更多
文摘An experiment on critical flow of water was conducted in two nozzles of 1.41 mm in diameter and 4.35 mm in length with rounded-edge and sharp-edge respectively, covering the ranges of inlet pressure of 22.1-29.1 MPa and inlet temperature of 38-474 ℃. More than 200 data points were obtained and the characteristics and parametric trends were investigated. In the region of near and beyond pseudo-critical temperature the thermal-equilibrium is dominant, and the flow rate can be estimated by the modified homogeneous equilibrium model. In the below pseudo-critical region the results exhibit scattered feature as a result of hysteresis effect in the onset of vaporization, characterizing a bifurcation behavior. This effect is more significant in the nozzle with sharp-edge, especially at higher pressure. For temperature well below the pseudo-critical point, the flow is not at critical condition and the flow rate can be represented by the Bernoulli equation reasonably.
文摘Nosing process of circular metal tubes in empty and polyurethane foam-filled conditions on a semispherical rigid die was analyzed by theoretical and experimental methods.A new theoretical model of plastic deformation of circular metal tubes was demonstrated during the nosing process on a rigid semispherical die.Based on the analytical model,some theoretical relations were calculated to estimate instantaneous forming load and dissipated energy of empty and foam-filled circular metal tubes versus axial displacement.Some circular brazen and aluminum tubes were prepared and shaped into semispherical nosed nozzles to verify the present theory.Comparison of theoretical predictions and the corresponding experimental measurements reveals that predicted load?displacement and dissipated energy?displacement diagrams by theoretical formulas have a good correlation with the corresponding experimental curves and it proves verity of the theory.Also,the present theory shows that dissipated energy and axial load of empty tubes depend on material type,wall thickness and diameter of the tubes and they are independent of tube initial length.Furthermore,the experimental results show that the presence of polyethylene Teflon-constraints increases ultimate axial displacement of the forming process.
基金Supported by the National Natural Science Foundation of China(No.29976024)
文摘This paper studies the influence of feed injection on the hydrodynamic behavior of fluid catalytic cracking riser reactors. Experiments were conducted in a cold model of 186 mm ID with two oppositely inclined secondary air feed nozzles. The flow structure was determined by means of the axial static pressure measurements and local radial optic fiber probe measurements on different levels with emphasis on the sections downstream of the secondary injection. The measurements reveal that the secondary injection plays a crucial role on riser hydrodynamics. Just above the secondary injection, the flow and mixing are strongly affected, while below the secondary injection the effect is weak. The radial profile just downstream of secondary injection demonstrates wavy features. The effective region of secondary injection could be estimated by the axial pressure gradient profiles and/or the radial profiles of local solids velocity and density.
基金supported by the National Natural Science Foundation of China (Grant No. 51035002)the Key Project of Chinese Ministry of Edu-cation (Grant No. 708055)the Fundamental Research Funds for the Central Universities (Grant No. 2010121039)
文摘Pulsed electrohydrodynamic printing （EHDP） is used to fabricate conductive silver patterns with micrometer resolution. The silver ink pendant experiences swelling, pulsation, and ejection under an applied pulse voltage of 20 Hz. The droplet deposi- tion frequency is equal to the applied voltage frequency so that the EHDP can deposit silver ink on demand. A low applied voltage favors uniform and non-scattering silver patterns while a high applied voltage results in ink scattering. Discrete drop- lets with 45-55 gm in diameter and continuous tracks with 60 gm in width are generated by using a ll0-i.tm-cailber nozzle. The feature size of deposited patterns is about half of the nozzle caliber, and a finer resolution can be achieved with the intro- duction of smaller nozzle calibers. Furthermore, the appropriate curing condition is investigated for sufficient combustion of ink solvent. The minimum resistivity of 3.3 gf~ cm is demonstrated for a continuous track cured at 200~C for 10 min. Eventu- ally, several passive electrical components, such as coated resistors, interdigitated capacitors （6 pF）, and spiral inductors （0.6 gH）, are successfully fabricated.
文摘Cold spray is a technique to make a coating on a wide variety of mechanical or electric parts by spraying solid particles accelerated through a high-speed gas flow in a converging-diverging nozzle. In this study, pseudo-shock waves in a modeled cold spray nozzle as well as high-speed gas jets are visualized by schlieren technique. The schlieren photographs reveals the supersonic flow with shock train in the nozzle. Static pressure along the barrel wall is also measured. The location of the head of pseudo-shock wave and its pressure distribution along the nozzle wall are analytically explained by using a formula of pseudo-shock wave. The analytical results show that the supersonic flow accompanying shock wave in the nozzle should be treated as pseudo-shock wave instead of normal shock wave.
基金supported by the Project KONTAKT #ME 08025 monitored by the Ministry of Education of the Czech Republicthe grant No101/08/0623 supported by the Czech Science Foundation
文摘This paper deals mainly with pneumatic measurements on a radial turbine nozzle cascade. The fill radial cascade guarantees the exit flow field periodicity downstream of it. A special traversing mechanism with a five - hole conical probe moving along a circular path behind the cascade was used for flow field investigation in this type of cascade with very low aspect ratio. The analyses of results of 2D and 3D pneumatic measurements including loss coefficient values are presented.
