Gas distribution device of the fluidized bed apparatus

A common scientific problem is that the monographs of leading scientists provide very modest recommendations for the calculation and design of gas distribution devices in fluidized bed apparatus. So, in the monograph of P.G. Romankov and N.B. Rashkovsky, hydraulic resistance of the switchgear is advised to be taken equal to half the hydraulic resistance of the fluidized bed. This recommendation does not take into account such factors as: the specific gravity of the fluidized product, the rate of fluidization and removal of small particles of the product, and the geometric parameters of the gas distribution device. In the monograph of B.S. Sazhin, it is recommended that a pressure drop on the gas distribution device is taken not less than 1000 Pa. What parameters should induce such a pressure drop is not specified. In the work of V.M. Marchevsky and R.N. Zherebkina, the dependence connecting the hydrodynamic stability of the fluidized bed with the area of the "living" section of the openings in the gas distribution device and with the parameters of the velocity regime of the fluidized bed was obtained experimentally. The value of the hydrodynamic stability was taken as the difference in the bed heights at which the fluidization of the higher layer ceased. The obtained dependence allows calculating the cross-sectional areas of the openings for the passage of the coolant, but does not allow calculating the design of the gas distribution device: in particular, the configuration and number of openings, their location, pitch and hydraulic resistance. Experimental studies are needed for their calculation. The unsolved part of the scientific problem is that it is not possible to find an exact theoretical definition of the hydraulic resistance coefficients; their values can be found only experimentally. Experiments and literature data show that the hydraulic resistance coefficient does not depend on numbers Re ≥ 1000. The main factor influencing the value of the hydraulic resistance coefficient is the ratio F / F1, where F is the cross-sectional area of the lattice holes and F1 is the cross-sectional area of the apparatus. Analysis of the parameters presented in this paper confirms that the value of the hydraulic resistance coefficient increases with increasing according to the linear law . Segment 0 - 1, which cuts off the approximating line on the y-axis, reflects the hydraulic resistance coefficient of the columnar grid. The obtained equation describes with sufficient accuracy the dependence of the hydraulic resistance coefficient on the parameter in the range of . The standard deviation of the experimental values of the hydraulic resistance coefficient from the calculated one is σ = 0.075. It is established that the main factor influencing the value of the hydraulic resistance coefficient is the relative area of the "living" cross-section of the openings in the gas distribution device.

Hydraulic resistance accompanying waterjet cutting

Introduction. Two-phase flow transmission is a complex process exposed to the influence of numerous factors. Its characteristics may depend on the physical properties of a flowing medium and on the properties of a pipeline, flow velocities, etc. A research into new types of hydraulic systems serves to identify the parameters that characterize the processes that accompany their transmission, especially if a multi-component flow is analyzed (a mix of water and abrasive particles). The mission of the research is to identify the value of hydraulic resistance coefficient in the course of transmission of a two-phase flow, or a mix of water and an abrasive. Materials and methods. A physics experiment, mathematical data processing methods, data description. Results. The co-authors have identified the hydraulic resistance coefficient value in the course of the mix transmission, as well as the parameters characterizing supplementary pressure losses in the course of the abrasive transmission. The experimental research enabled the co-authors to identify maximal water and mix application distances that reach 317 and 290 meters. Conclusions. The results, obtained by the co-authors, are the consequence of the pressure losses that occur in the course of mix transmission and the coefficients that characterize it. The flows considered in the article are used in the systems whose parameters are considerably different from those of traditional hydraulic engineering systems; therefore, any theoretical results obtained by the co-authors need experimental verification. Further, similar systems having different parameters must also be exposed to research to identify the relation between the pressure loss and the abrasive consumption rate and amount. The practical value of the research consists in the identification of maximal water and mix transmission and application distances providing that the operating parameters of the systems remain unchanged.

Determination of hydraulic resistance of the aerothermopressor for gas turbine cyclic air cooling

One of the promising trends to increase the fuel and energy efficiency of gas turbines is contact cooling of cyclic air by using a twophase jet apparatus – an aerothermopressor. The rational parameters of work processes of the aerothermopressor were studied. The experimental setup was designed to simulate the aerothermopressor operation in the cooling air cycle of the gas turbine and to determine pressure losses in the aerothermopressor flow part. Based on the obtained experimental data, an empirical equation was proposed to determine the hydraulic resistance coefficient of the aerothermopressor flow part, depending on the initial pressure and the amount of water injected. The deviation of the calculated hydraulic resistance coefficient from the experimental ones is ± 25 %. The obtained results can be used in the practice of designing the aerothermopressor for gas turbine cyclic air cooling.

Collecting of finely dispersed particles by means of a separator with the arc-shaped elements

This paper includes the description of a separator, developed by the authors for the gas flow purification from the finely dispersed particles. The authors also studied the influence of the separator dimensions and the dusty gas flow rate on the degree of its purification from the finely dispersed particles, as well as on the change in the hydraulic resistance of this apparatus. This paper also shows that the main forces that make the greatest contribution to the purification of the gas flow from the finely dispersed particles are centrifugal and inertial. Moreover, the dependencies of the purification efficiency on the Stokes numbers are shown in this paper. The authors studied the change in the hydraulic resistance coefficient of this apparatus from the Reynolds numbers as well.

The hydraulic resistance coefficient in the conditions of simultaneous effect of Re, Fr and Unknown node mfrac found in MathML fragment.$ {B \over h} $

One of the most important tasks of engineering hydraulics is to determine the energy loss during the motion of the fluid flow. The study of the question of whether the patterns of hydraulic resistances are similar in a calm and turbulent flow is relevant in the design of hydraulic structures. In most cases, a turbulent regime of fluid motion is observed in various applications, but to date, the theory of turbulence is not considered complete. When designing hydraulic structures, inaccuracies in the existing calculation methods can lead to a decrease in the efficiency and reliability of the entire spillway structure as a whole. The need for an integrated approach to the analysis of the impact on the hydraulic resistance of various factors is noted (degree of spread $ \left( {{B \over h}} \right) $), the degree of turbulence (Re) and the degree of flow roughness (Fr)), which is not always provided by known dependencies and methods of calculation. On the basis of our own experimental data, a new formula for calculating the hydraulic resistance of turbulent flows in smooth channels was obtained. The functional dependence of the hydraulic resistance coefficient on the parameters $ \left( {{B \over h}} \right) $, Re and Fr is obtained.

The regularities of resistance and flow in pipes and wide channels

The data of hydraulic characteristics of flow are required to be more accurate to increase reliability and accident-free work of water conducting systems and hydraulic structures. One of the problems in hydraulic calculations is the determination of friction loss that is associated with the distribution of velocities over the cross section of the flow. The article presents a comparative analysis of the regularities of velocity distribution based on the logarithmic velocity profile and hydraulic resistance in pipes and open channels. It is revealed that the Karman parameter is associated with the second turbulence constant and depend on the hydraulic resistance coefficient. The research showed that the behavior of the second turbulence constant in the velocity profile is determined mainly by the Karman parameter. The attached illustrations picture the dependence of logarithmic velocity profile parameters based on different values of the hydraulic resistance coefficient. The results of the calculations were compared to the experimental-based Nikuradze formulas for smooth and rough pipes.