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In the present study, a detailed investigation of unsteady supersonic flows around rigid parachute models is performed by numerically solving three-dimensional compressible Navier-Stokes equations at a freestream Mach number of 1.5. The parachute system employed here consists of a capsule and a canopy. The cases with different capsule angles of attack (α) are simulated. The objective of this study is to examine the effects of capsule angle of attack on the flow fields and investigate ways to suppress the complicated aerodynamic interactions around the parachute models. As a result, it is found that as α is increased, the unsteady pulsation flow mode is weaken, and it almost disappears at α =10 deg.

The effects of vibrational non-equilibrium and vibration–chemistry coupling on hydrogen–air detonation are numerically investigated by solving reactive Euler equations coupled with a multiple vibrational temperature-based model. Detailed hydrogen–air reaction kinetic is utilized, Landau–Teller model is adopted to solve the vibrational relaxation process, and the coupled vibration–chemistry vibration model is used to evaluate the vibration–chemistry coupling. It is shown that the relaxation process and vibration–chemistry coupling considerably influence the hydrogen–air detonation structure, highlighting the importance of correct treatment of vibrational non-equilibrium in detonation simulations.

The scramjet engines have been extensively studied for use in aircraft and future space transportation systems operating at speeds of about Mach 5 and above. At these high flight velocities, the incoming air is slowed down and maintained supersonic speed within the combustor

The operating conditions of a turbulent contact absorber (TCA) can be divided into four regimes. The characteristic behaviour of a TCA in each of the regimes is discussed. The condition below the flooding point is the usual operating regime. Correlations are developed to relate the pressure drop and the liquid holdup of a TCA by the operating variables. A terminal velocity model is developed to explain the flooding condition of a TCA. With this model, the hydrodynamic behavior of the TCA at the flooding point can be identified. The total pressure drop and the pressure drop across a single stage are distinguished to clarify the controversy whether the gas velocity can affect the pressure drop of a TCA. The total pressure drop of a TCA is composed of the pressure drop due to distributor loss at the entrance and the pressure drop of the bed itself. The pressure drop of a single stage bed of a TCA is independent of gas velocity. On peut diviser en 4 regimes les conditions operatoires d'un absorbeur a contact turbulent (ACT); on discute le comportement caracteristique d'un ACT dans chacun d'eux. La condition qui prevaut au-dessous du point d'engorgement constitue le regime habituel d'operation. On a mis au point des correlations entre la chute de pression et la retention du liquide d'un ACT par les variables operatoires. On a mis au point un modele terminal de vitesse pour expliquer la condition d'engorgement d'un ACT; on peut grâce a celui-ci identifier le comportement hydrodynamique de l'ACT au point d'engorgement. On fait une distinction entre la chute totale de pression et la chute de pression dans un simple etage, pour clarifier la controverse relative a l'influence possible de la vitesse du gaz sur la chute de pression d'un ACT. La chute totale de pression d'un ACT comprend la chute de pression qui resulte de la perte du distributeur a l'entree et la chute de pression du lit meme. La chute de pression d'un lit a etage simple d'un ACT est independante de la vitesse du gaz.

Bubble size is one of the most important parameters in the design and simulation of a fluidized-bed reactor. A correlation of the bubble size and growth in fluidized beds of various diameters is developed. A maximum bubble diameter determined from the bubble coalescence is incorporated in the correlation to relate the effect of the bed diameter on the bubble size. Experimental data of bubble size reported are used to develop and test the validity of the correlation. The bubble diameters calculated using this correlation show good agreement with the observed bubble diameters.

A model describing the entrainment of solid particles in the freeboard region of a fluidized bed is proposed. Published experimental data have been used to correlate the entrainment rate near the bed surface and the elutriation rate above the bed. It has been shown that the column diameter can have an important influence on the amount of fines elutriated.

Transient equations based on impulse, step, ramp, parabolic and sinusoidal inputs for reactors of various flow models are presented. The flows accompanied by the first order irreversible chemical reaction are considered. The response expressions are useful for the selection of a proper model and for the evaluation of the residence time distributions in a given reactor. On preesente les equations transitoires pour divers modeles d'ecoulement dans des reacteurs selon des inputs varies tels que: en escalier, a variation constante, par impulsion, sinusoidal et parabolique. On considere les ecoulements accompagnes d'une reaction chimique irreversible du premier ordre. Les expressions sont utiles pour l'evaluation des distributions de temps de residence dans un reacteur donne.

Mechanical and dynamical characteristics of semifluidized beds of single-size particles in solid-liquid system were investigated. A semifluidized bed is a type of fluidized bed in which the bed expansion is partially restricted. The emphasis was placed on the study of packed bed formation and pressure drop increase when the semifluidized beds were formed by the compression of fluidized beds. The data showed good agreement with the theoretical and semiempirical equations based on a simple model of fluidized beds. The results of this investigation would also contribute to the understanding of fluidized beds.

The flow characteristics of dense solid-gas mixtures transported through horizontal pipes were studied with glass beads and coal powders of various sizes (0.0028 to 0.0297 in.) in 1/2-, 3/4- and 1-in. glass pipes and a 1/4-in. steel pipe. Fluidized-bed feeders were utilized, thus permitting solid-gas ratios considerably higher (range 80 to 750) than those possible with conventional pneumatic transport. When such high solid-gas ratios are used, the flow of mixtures in transport lines is characterized by a large amount of slippage between gas and solids. The flow pattern is dicussed on the basis of visual observation through glass pipes. A simple and interesting velocity relationship was noted, namely that the average gas velocity is about twice as large as the average solid-particle velocity. The solid-particle velocities and solid loadings in the pipe line were found to be primary factors affecting pressure drops, and the particle sizes and shapes, on the other hand, exerted a very slight effect on the pressure drops. This is apparently due to the fact that the solids move predominantly in the bottom of the pipes as agglomerated masses rather than as individually suspended particles. A pressure-drop correlation for the dense solid-gas mixtures is proposed, and applications and limitations of the correlation are shown.

Longitudinal liquid mixing in fluidized and fixed beds was studied using sinusoidal and pulse response techniques. The tracer used was light emissive fluorescein dye. A systematical study of liquid phase dispersion by varying particle size, fluid velocity, fraction voids, and particle density was conducted. A generalized correlation applicable to both fixed bed and fluidized bed was obtained. The application of the correlation in predicting the effect of the dispersion on reactor performance was discussed.

It is well known that the identification of flow regimes is important in scale-ups and designs of multiphase reactors. Therefore, it is natural that the selections of parameter prediction methods for the reactor models should be based on flow regimes. Very few correlations, theories and models are capable of covering the whole spectrum of flow regimes. Often, accuracy is sacrificed for generality. By concentrating on each individual flow regime and its characteristics, the correlations and models selected can be expected to give better results. The evaluation of correlations for phase holdups and liquid dispersion coefficients has been evaluated for both the slurry reactors and the three-phase fluidized bed reactors.

Experiments were conducted in a three-dimensional fluidized bed to investigate the presence of stagnant zones near the grid region. It was found that the formation of the dead zone above the distributor was influenced by the orifice gas velocity, orifice pitch, orifice diameter, particle size and particle density. The effect of bed height on the critical orifice gas velocity required for the elimination of the dead zone was insignificant within the range of bed heights investigated. Empirical correlations are proposed to calculate the critical orifice gas velocity required to eliminate the dead zone as a function of pitch, orifice diameter, particle size and particle density for a perforated plate distributor and for two different arrangements of a cap plate distributor.