Droplet behavior in the wave-type flow channel is discussed, especially with the secondary .droplet generation due to impingement of droplets on the wall considered. A numerical method is suggested to simulate tile dr...Droplet behavior in the wave-type flow channel is discussed, especially with the secondary .droplet generation due to impingement of droplets on the wall considered. A numerical method is suggested to simulate tile droplet behavior in the flow field. Calculations are compared With experimental data on the ; pressure drop and separating efficiency. Good agreement exists between the calculations and air-water experiments. The numerical method developed gives a reasonable description of the droplet deposition and secondary droplet generation, and it can be applied to predict the performance of wave-type vane separators.展开更多
It has been shown that much dynamic information is hidden in the pressure fluctuation signals of a gas-solid fluidized bed. Unfortunately, due to the random and capricious nature of this signal, it is hard to realize ...It has been shown that much dynamic information is hidden in the pressure fluctuation signals of a gas-solid fluidized bed. Unfortunately, due to the random and capricious nature of this signal, it is hard to realize reliable analysis using traditional signal processing methods such as statistical analysis or spectral analysis, which is done in Fourier domain. Information in different frequency band can be extracted by using wavelet analysis. On the evidence of the composition of the pressure fluctuation signals, energy of low frequency (ELF) is proposed to show the transition of fluidized regimes from bubbling fluidization to turbulent fluidization. Plots are presented to describe the fluidized bed's evolution to help identify the state of different flow regimes and provide a characteristic curve to identify the fluidized status effectively and reliably.展开更多
Gas–liquid two-phase flow abounds in industrial processes and facilities. Identification of its flow pattern plays an essential role in the field of multiphase flow measurement. A bluff body was introduced in this s...Gas–liquid two-phase flow abounds in industrial processes and facilities. Identification of its flow pattern plays an essential role in the field of multiphase flow measurement. A bluff body was introduced in this study to recognize gas–liquid flow patterns by inducing fluid oscillation that enlarged differences between each flow pattern. Experiments with air–water mixtures were carried out in horizontal pipelines at ambient temperature and atmospheric pressure. Differential pressure signals from the bluff-body wake were obtained in bubble, bubble/plug transitional, plug, slug, and annular flows. Utilizing the adaptive ensemble empirical mode decomposition method and the Hilbert transform, the time–frequency entropy S of the differential pressure signals was obtained. By combining S and other flow parameters, such as the volumetric void fraction β, the dryness x, the ratio of density φ and the modified fluid coefficient ψ, a new flow pattern map was constructed which adopted S（1–x）φ and （1–β）ψ as the vertical and horizontal coordinates, respectively. The overall rate of classification of the map was verified to be 92.9% by the experimental data. It provides an effective and simple solution to the gas–liquid flow pattern identification problems.展开更多
The effects of gas temperature fluctuations on soot formation and oxidation reactions are investigated numerically in a reacting flow. The instantaneous variations of soot mass fraction with time are obtained under th...The effects of gas temperature fluctuations on soot formation and oxidation reactions are investigated numerically in a reacting flow. The instantaneous variations of soot mass fraction with time are obtained under the time-averaged gas temperature of 1500-1700 K. The simulation results show that the gas temperature fluctuation has obvious influence on the instantaneous processes of soot formation and oxidation. Within the present range of gas temperature, the gas temperature fluctuation results in generally lower soot mass fraction comparing to that without gas temperature fluctuation. The increase in the fluctuation amplitude of gas temperature leads to decrease in time-averaged soot mass fraction and increase in time-averaged soot particle number density.展开更多
According to the research results of motion parameters of coal-gas flow,analyzedthe formation mechanism of shock waves at different states of coal-gas flow in theprocess of coal and gas outburst,and briefly described ...According to the research results of motion parameters of coal-gas flow,analyzedthe formation mechanism of shock waves at different states of coal-gas flow in theprocess of coal and gas outburst,and briefly described the two possible cases of outburstshock wave formation and their formation conditions in the process of coal and gas out-burst,and then pointed out that a high degree of under-expanded coal-gas flow was themain reason for the formation of a highly destructive shock wave.The research resultsimproved the shock wave theory in coal and gas outburst.展开更多
Random fluctuations of turbulence bring random fluctuations of the refractive index, making the atmosphere a random fluctuation medium that destroys the coherence of light-waves. Research in atmospheric turbulence is ...Random fluctuations of turbulence bring random fluctuations of the refractive index, making the atmosphere a random fluctuation medium that destroys the coherence of light-waves. Research in atmospheric turbulence is actually the investigation of the atmospheric refractive index. The atmospheric structure constant of refractive index, C n 2 , is an important parameter denoting atmospheric turbulence. In this paper, C n 2 is measured during the day and at night and in all four seasons using a high sensitivity micro-thermal meter QHTP-2. The vertical profile of C n 2 in Hefei (0-30 km) is investigated by the analysis of experimental data. The average profile of C n 2 in Hefei exhibits conspicuous day and night differences with increased altitude. The distribution of log(C n 2 ) is nearly normal and has conspicuous seasonal differences.展开更多
When a normal shock wave interacts with a boundary layer along a wall surface in supersonic internal flows and the shock is strong enough to separate the boundary layer, the shock is bifurcated and a series of shocks ...When a normal shock wave interacts with a boundary layer along a wall surface in supersonic internal flows and the shock is strong enough to separate the boundary layer, the shock is bifurcated and a series of shocks called “shock train” is formed. The flow is decelerated from supersonic to subsonic through the whole interaction region that is referred to as “pseudo-shock”. In the present paper some characteristics of the shock train and pseudo-shock and some examples of the pseudo-shocks in some flow devices are described.展开更多
In this paper numerical calculations of the dry and humid air flows in the nozzle are presented. The dry air flow (adiabatic flow) and the humid air flow (flow with homogeneous condensation, diabatic flow) are modeled...In this paper numerical calculations of the dry and humid air flows in the nozzle are presented. The dry air flow (adiabatic flow) and the humid air flow (flow with homogeneous condensation, diabatic flow) are modeled with the use of Reynolds Averaged Navier-Stokes (RANS) equations. The comparison of these two types of flow is carried out. The influence of the air humidity on the shock wave location and its interaction with the boundary layer is examined. Obtained numerical results present a first numerical approach of the condensation and evaporation process in transonic flow of humid air. The phenomena considered here are very complex and complicated and need further in-depth numerical analysis.展开更多
We propose here an experimental investigation of a vortex submitted to a radial perturbation while being compressed. This experiment reproduces a model situation of the complex flows that take place in a real engine c...We propose here an experimental investigation of a vortex submitted to a radial perturbation while being compressed. This experiment reproduces a model situation of the complex flows that take place in a real engine cylinder. An isolated tumbling flow is first submitted to an injection of fluid and then compressed and measurements are realised by Particle Image Velocimetry (PIV). The Proper Orthogonal Decomposition is known to be an unbiased method to identify the coherent structures of turbulent flows. It is possible to make this decomposition for a given phase or to create a set of basis functions with the whole set of compression stroke velocity fields.First, the experimental set-up will be presented, then the second part provides the POD principle. Results of phased POD decomposition of the compression of the unperturbated vortex will be presented. Finally results from the time invariant POD will be discussed to study the influence of the jet perturbation in the compression of a vortex.展开更多
The experimental and numerical investigations of the flow with reaction of two gases: hydrogen chloride HC1 and ammonia NH3 were performed. The article contains description of the visualisation method of the formation...The experimental and numerical investigations of the flow with reaction of two gases: hydrogen chloride HC1 and ammonia NH3 were performed. The article contains description of the visualisation method of the formation and flow of particles of ammonia chloride NH4Cl. Analyses of mean concentration and variance of concentration fluctuations of dispersed phase were performed for different outputs of gases. Numerical calculations were performed for analysed phenomenon. Both numerical and visualisation results were matched and compared.展开更多
基金Supported by the National Key Laboratory of Bubble Physics&Natural Circulation(No.51482150104JW0502).
文摘Droplet behavior in the wave-type flow channel is discussed, especially with the secondary .droplet generation due to impingement of droplets on the wall considered. A numerical method is suggested to simulate tile droplet behavior in the flow field. Calculations are compared With experimental data on the ; pressure drop and separating efficiency. Good agreement exists between the calculations and air-water experiments. The numerical method developed gives a reasonable description of the droplet deposition and secondary droplet generation, and it can be applied to predict the performance of wave-type vane separators.
文摘It has been shown that much dynamic information is hidden in the pressure fluctuation signals of a gas-solid fluidized bed. Unfortunately, due to the random and capricious nature of this signal, it is hard to realize reliable analysis using traditional signal processing methods such as statistical analysis or spectral analysis, which is done in Fourier domain. Information in different frequency band can be extracted by using wavelet analysis. On the evidence of the composition of the pressure fluctuation signals, energy of low frequency (ELF) is proposed to show the transition of fluidized regimes from bubbling fluidization to turbulent fluidization. Plots are presented to describe the fluidized bed's evolution to help identify the state of different flow regimes and provide a characteristic curve to identify the fluidized status effectively and reliably.
基金Project(51576213)supported by the National Natural Science Foundation of ChinaProject(2015RS4015)supported by the Hunan Scientific Program,ChinaProject(2016zzts323)supported by the Innovation Project of Central South University,China
文摘Gas–liquid two-phase flow abounds in industrial processes and facilities. Identification of its flow pattern plays an essential role in the field of multiphase flow measurement. A bluff body was introduced in this study to recognize gas–liquid flow patterns by inducing fluid oscillation that enlarged differences between each flow pattern. Experiments with air–water mixtures were carried out in horizontal pipelines at ambient temperature and atmospheric pressure. Differential pressure signals from the bluff-body wake were obtained in bubble, bubble/plug transitional, plug, slug, and annular flows. Utilizing the adaptive ensemble empirical mode decomposition method and the Hilbert transform, the time–frequency entropy S of the differential pressure signals was obtained. By combining S and other flow parameters, such as the volumetric void fraction β, the dryness x, the ratio of density φ and the modified fluid coefficient ψ, a new flow pattern map was constructed which adopted S（1–x）φ and （1–β）ψ as the vertical and horizontal coordinates, respectively. The overall rate of classification of the map was verified to be 92.9% by the experimental data. It provides an effective and simple solution to the gas–liquid flow pattern identification problems.
基金Supported jointly by the National Natural Science Foundation of China(51076082)the State Key Laboratory of Engines(SKLE200902)
文摘The effects of gas temperature fluctuations on soot formation and oxidation reactions are investigated numerically in a reacting flow. The instantaneous variations of soot mass fraction with time are obtained under the time-averaged gas temperature of 1500-1700 K. The simulation results show that the gas temperature fluctuation has obvious influence on the instantaneous processes of soot formation and oxidation. Within the present range of gas temperature, the gas temperature fluctuation results in generally lower soot mass fraction comparing to that without gas temperature fluctuation. The increase in the fluctuation amplitude of gas temperature leads to decrease in time-averaged soot mass fraction and increase in time-averaged soot particle number density.
基金Supported by the Key Program of National Basic Research Program of China(973)(2005CB221504)the Key Program of National Natural Science Foundation of China(50534080)
文摘According to the research results of motion parameters of coal-gas flow,analyzedthe formation mechanism of shock waves at different states of coal-gas flow in theprocess of coal and gas outburst,and briefly described the two possible cases of outburstshock wave formation and their formation conditions in the process of coal and gas out-burst,and then pointed out that a high degree of under-expanded coal-gas flow was themain reason for the formation of a highly destructive shock wave.The research resultsimproved the shock wave theory in coal and gas outburst.
基金supported by the National High Technology Research and Development Program of China (GrantNo. 2011AA8061007)
文摘Random fluctuations of turbulence bring random fluctuations of the refractive index, making the atmosphere a random fluctuation medium that destroys the coherence of light-waves. Research in atmospheric turbulence is actually the investigation of the atmospheric refractive index. The atmospheric structure constant of refractive index, C n 2 , is an important parameter denoting atmospheric turbulence. In this paper, C n 2 is measured during the day and at night and in all four seasons using a high sensitivity micro-thermal meter QHTP-2. The vertical profile of C n 2 in Hefei (0-30 km) is investigated by the analysis of experimental data. The average profile of C n 2 in Hefei exhibits conspicuous day and night differences with increased altitude. The distribution of log(C n 2 ) is nearly normal and has conspicuous seasonal differences.
文摘When a normal shock wave interacts with a boundary layer along a wall surface in supersonic internal flows and the shock is strong enough to separate the boundary layer, the shock is bifurcated and a series of shocks called “shock train” is formed. The flow is decelerated from supersonic to subsonic through the whole interaction region that is referred to as “pseudo-shock”. In the present paper some characteristics of the shock train and pseudo-shock and some examples of the pseudo-shocks in some flow devices are described.
文摘In this paper numerical calculations of the dry and humid air flows in the nozzle are presented. The dry air flow (adiabatic flow) and the humid air flow (flow with homogeneous condensation, diabatic flow) are modeled with the use of Reynolds Averaged Navier-Stokes (RANS) equations. The comparison of these two types of flow is carried out. The influence of the air humidity on the shock wave location and its interaction with the boundary layer is examined. Obtained numerical results present a first numerical approach of the condensation and evaporation process in transonic flow of humid air. The phenomena considered here are very complex and complicated and need further in-depth numerical analysis.
文摘We propose here an experimental investigation of a vortex submitted to a radial perturbation while being compressed. This experiment reproduces a model situation of the complex flows that take place in a real engine cylinder. An isolated tumbling flow is first submitted to an injection of fluid and then compressed and measurements are realised by Particle Image Velocimetry (PIV). The Proper Orthogonal Decomposition is known to be an unbiased method to identify the coherent structures of turbulent flows. It is possible to make this decomposition for a given phase or to create a set of basis functions with the whole set of compression stroke velocity fields.First, the experimental set-up will be presented, then the second part provides the POD principle. Results of phased POD decomposition of the compression of the unperturbated vortex will be presented. Finally results from the time invariant POD will be discussed to study the influence of the jet perturbation in the compression of a vortex.
文摘The experimental and numerical investigations of the flow with reaction of two gases: hydrogen chloride HC1 and ammonia NH3 were performed. The article contains description of the visualisation method of the formation and flow of particles of ammonia chloride NH4Cl. Analyses of mean concentration and variance of concentration fluctuations of dispersed phase were performed for different outputs of gases. Numerical calculations were performed for analysed phenomenon. Both numerical and visualisation results were matched and compared.
