Measuring the Flow Functions of Pharmaceutical Powders Using the Brookfield Powder Flow Tester and Freeman FT4

This study examined the feasibility of combining data from different powder flow testers to determine the flow function characteristics of pharmaceutical powders. The Brookfield PFT and Freeman FT4 can measure flow function over different scales of consolidation load but were found to be most complementary with CRM limestone powder and lactose. The brittle behaviour of Easytab particles at higher loads made obtaining repeatable results with the FT4 challenging. By using the method of Wang et al., where the flow function coefficient ffc is plotted against the dimensionless cohesion C* (measured cohesion Ta divided by the initial compaction I), a plot was formed which could be used to predict the behaviour of other systems, which compared well with previous studies.

MECHANICAL CHARACTERISTICS OF THE RUBBED MAIZE STRAW DURING SCREW CONVEYING

In order to reduce the power consumption of screw conveyor and to improve the productivity, this study investigated such mechanical characteristics of rubbed maize straw as coefficient of sliding friction, angle of repose, internal friction coefficient, cohesion, flow function value and compressible coefficient with respect to its moisture content and density. An experiment was designed and consists of a sliding friction characteristic test-bed, a direct shear apparatus, a self-made device with adjustable density and compression. The results showed that: the coefficient of sliding friction increases with the increase of moisture content and density; the angle of repose and internal friction coefficient each increases with increasing moisture content respectively; there is no significant effect between the moisture content and the cohesion of rubbed maize straw; the flow function value goes up with the increase of the moisture content; also the increase of the moisture content leads to the increased bulk density due to the reduced materials gap and the increased compression coefficient, which makes it hard to compress. The equation of pressure and density was found, and it is suitable for the analysis of compression characteristic of rubbed maize straw. The research results lay a theoretical foundation and a basis for the further study on mechanical properties of maize straw.

A Study on the Leakage Characteristics of a Stepped Labyrinth Seal with a Ribbed Casing

A new type of stepped seal with a ribbed casing is proposed to efficiently reduce the leakage at the tips of turbine blades. The leakage characteristics of two different types of labyrinth seals (conventional seal vs. ribbed seal) were compared and analyzed through computational fluid dynamics (CFD) in a wide operating range of pressure ratios and clearances. The analysis showed that the ribbed seal has superior leakage performance to the conventional seal at all clearance sizes. With the same clearance size (S/H = 1.0), the flow function of the ribbed seal was approximately 21.5–42.6% less than that of the conventional seal. Also, different trends of variation in the flow function according to the increase of the clearance were found between the conventional and ribbed seals. The leakage flow inside the labyrinth seal was analyzed to explain the cause of this difference in tendency, and it was confirmed that the added ribs cause collision between the leakage flow and the tooth wall, even with the increase of the clearance. Also, the ribbed seal enables operation at a larger clearance with the same leakage performance when comparing the absolute leakage flow rate of the two seals. In addition, a parametric study on the influence of the rib height and rib inclination angle revealed that the flow function generally decreases as both parameters increase.

Optimal Inflow Performance Relationship Equation for Horizontal and Deviated Wells in Low-Permeability Reservoirs

After Vogel proposed a dimensionless inflow performance equation, with the rise of the horizontal well production mode, a large number of inflow performance relationship (IPR) equations have emerged. In the productivity analysis of deviated and horizontal wells, the IPR equation proposed by Cheng is mainly used. However, it is still unclear whether these inflow performance models (such as the Cheng, Klins-Majcher, Bendakhlia-Aziz, and Wiggins-Russell-Jennings types) are suitable for productivity evaluations of horizontal and deviated wells in low-permeability reservoirs. In-depth comparisons and analyses have not been carried out, which hinders improvements in the accuracy of the productivity evaluations of horizontal wells in low-permeability reservoirs. In this study, exploratory work was conducted in two areas. First, the linear flow function relationship used in previous studies was improved. Based on the experimental pressure-volume-temperature results, a power exponential flow function model was established according to different intervals greater or less than the bubble point pressure, which was introduced into the subsequent derivation of the inflow performance equation. Second, given the particularity of low-permeability reservoir percolation, considering that the reservoir is a deformation medium, and because of the existence of a threshold pressure gradient in fluid flow, the relationship between permeability and pressure was changed. The starting pressure gradient was introduced into the subsequent establishment of the inflow performance equation. Based on the above two aspects of this work, the dimensionless IPR of single-phase and oil-gas two-phase horizontal wells in a deformed medium reservoir was established by using the equivalent seepage resistance method and complex potential superposition principle. Furthermore, through regression and error analyses of the standard inflow performance data, the correlation coefficients and error distributions of six types of IPR equations applicable to deviated and horizontal wells at different inclination angles were compared. The results show that the IPR equation established in this study features good stability and accuracy and that it can fully reflect the particularity of low-permeability reservoir seepage. It provides the best choice of the IPR between inclined wells and horizontal wells in low-permeability reservoirs. The other types of IPR equations are the Wiggins-Russell-Jennings, Klins-Majcher, Vogel, Fetkovich, Bendakhlia-Aziz, and Harrison equations, listed here in order from good to poor in accuracy.

Spatial Analogues of Numerical Quasiconformal Mapping Methods for Solving Problems of Bursts Parameters Identification

An approach to solving the problem of image reconstruction based on applied quasipotential tomographic data in the three-dimensional case is developed. It is based on the synthesis of spatial analogues of numerical quasiconformal mapping methods and algorithm for identifying the parameters of local bursts of homogeneous materials using similar methods on the plane. The peculiarity of the corresponding algorithm is taking into account (for each of the appropriate injections) the presence of only equipotential lines (with given values of the flow function or distributions of local velocities on them) and flow lines (with known potential distributions on them) at the domain boundary. Numerical experiments of simulative restoration of the environment structure are carried out.

ВИБІР І ОБҐРУНТУВАННЯ МЕТОДУ ГЕНЕРАЦІЇ СІТКИ ДЛЯ МОДЕЛЮВАННЯ ТЕЧІЇ У ВЕНТИЛЯТОРІ ГАЗОТУРБІННОГО ДВИГУНА

The study of flow in aircraft gas turbine engines is one of the main components for the creation of new compressors and fans with improved aerodynamic, acoustic, strength, overall weight, and other characteristics. In modern scientific research, the methods of the physical experiment are used at the final stages of flow studies in blade machines. a numerical experiment is used in the early stages. An obvious advantage of the numerical experiment is the ability to study many variants of constructions under different input and boundary conditions in a short period. However, a numerical experiment requires a preliminary selection and justification of its parameters and components. One such important component is the type of calculation mesh. The literature review shows that it is impossible to make an unambiguous conclusion about the choice of the type of method for generating the finite element mesh and the turbulence model. This work aims to compare a hybrid and structured mesh for flow modeling in an axial fan of a bypass engine with a high bypass ratio. Two impellers of a bypass engine with a high bypass ratio are selected as the object of study. Flow simulation in fans was studied at a rotor speed of 2202 rpm in the range of values of the gas-dynamic flow function at the inlet q (λ) = 0.4 ... 0.65. Based on the literature review, the system of Navier-Stokes equations was closed by the SST turbulent model. To select and substantiate the method of finite-element grid generation, a structured and hybrid mesh for two fan variants were constructed. According to the results of the calculations, the dependence of the pressure ratio of fan π on the gas-dynamic flow function at the inlet q (λ) was constructed. According to the results of the study, it can be stated that the discrepancy of the calculations for the impellers in the axial fan of a bypass engine with a high bypass ratio with structured and hybrid meshes will be up to 2 %. When choosing the method of mesh generation, the time of calculation is also an important factor. Studies have shown that the calculation with a structured mesh took place in less time by 50 ... 70% than when using a hybrid mesh for one variant of the geometry.