Study of the characteristics of the ascending vortex of the cyclone and the concentration of dust along its section

Introduction. Protection of the atmosphere is a social and economic problem inextricably linked with the task of creating comfortable conditions for human life and work. Cyclones are the most typical representatives of dry inertial dust collectors. This work is aimed at reducing energy consumption when cleaning gas with cyclones. Materials and methods. In the course of the work, analytical and experimental research methods were applied. Results. Analytical dependences of the aerodynamics of the ascending cyclone vortex have been obtained, which showed that the ascending vortex has a complex structure and the cyclone is an artificially created spiral structure, akin to such a natural phenomenon as a tornado. The obtained mathematical model was fully confirmed by experimental studies. Conclusions. The studies carried out show that the ascending vortex in the cyclone has a structure consisting of two zones. In the first zone (core), the force of the radial pressure gradient exceeds the centrifugal force, and the dust rushes towards the cyclone axis. In the second, the centrifugal force exceeds the force of the pressure gradient, and the dust is thrown to the periphery. The obtained theoretical model will make it possible to reasonably choose methods for more rational use of the expended energy and increasing the efficiency of cyclones.

Showerhead film cooling injection orientation design on the turbine vane leading edge considering representative lean burn combustor outflow

The heat transfer performance of showerhead film cooling on the vane leading edge was numerically investigated considering representative lean burn combustor swirling outflow. Three cases with different inflow conditions (uniform inflow, positive swirling inflow, and negative swirling inflow) and three cases with different film injection angles (45°, 90°, and 135°) were studied. As the first study to explore the showerhead film design principle under swirling inflow, a newly designed asymmetrical counter-inclined (45° and 135°) film cooling was also proposed. To examine the design principles, the cooling effectiveness, heat transfer augmentation, and heat flux reduction of the newly designed asymmetrical case were evaluated compared with the traditional symmetrical case. The results show that the swirling inflow introduces obvious radial pressure gradient on the vane. The radial pressure gradient is the key influence factor to deflect the coolant migration, decrease the cooling effect, and degrade the homogeneity. The film with opposite orientation to the radial pressure gradient can weaken the deflect effect. The radial pressure gradient direction differs in different regions, making it impossible for the film with congruent injection orientation to simultaneously resist the pressure gradient on the entire vane. For the new design, the boundary line of the counter-inclined holes is consistent with the twisted stagnation line to guarantee that the injection orientation of all the film holes is opposite to the radial pressure gradient. As expected, the new design can effectively weaken the deflection effect and show uniform film distribution. The higher coolant mass ratio provides more obvious enhancement effect. At coolant mass ratio 3.71% and 4.56%, the overall area-averaged heat flux reduction (Δ q) is increased by 0.311 and 0.576, and the overall area-averaged relative standard deviation is reduced by 12.17 and 11.66 compared with the traditional design. The results have confirmed the adaptability of the film design principle under swirling inflow.

Unsteady Measurement of Core Penetration Flow in a Turbine Rotor-Stator Disc Cavity

The existence and causes of the deep ingress of the annulus flow into the core region of a turbine rotor-stator disc cavity, or core penetration flow, have been investigated experimentally. In addition, the effects of annulus flow coefficient, rotational Reynolds number, and non-dimensional purge air flow rate on the core penetration flow have been examined. Using the low–speed, low expansion ratio single-stage cold turbine test facility at Seoul National University (SNU), time-resolved tangential and radial velocities in the cavity have been measured with 2-D hot-wire anemometers. In addition, time-resolved static pressures on the stator disc have been measured with fast response pressure transducers, and the unsteady cavity velocity field in the absolute frame has been measured using Particle Image Velocimetry (PIV). Geometric non-axisymmetry (e.g. eccentricity of a rotor disc cover in this study) can change the cavity exit pressure, and thus the radial pressure gradient in the cavity. A time lag in the tangential velocity adjustment to the variation in the radial pressure gradient results in a net radial force, leading to core penetration flow. The core penetration flow occurs twice when the cavity exit pressure increases, and once when the cavity exit pressure decreases. In this study, with a once per revolution geometric non-axisymmetry, the core penetration flow occurs three times per revolution, revolving at the disc’s rotational speed. Variations in the annulus flow coefficient or rotational Reynolds number do not affect the core penetration flow, but increasing the purge air flow rate weakens the core penetration flow.

Research on Coanda Effect Appeared in Oil-Air Annular Flow through the Conical Diffuser

Physical model and numerical simulation model for oil-air annular flow through conical diffusers are built by Fluent, and Coanda Effect, a commonly phenomenon, appeared in this kind of oil-air annular flow field is studied, especially influences of Coanda Effect on the attachment of the liquid phase of annular flow trended to the curved wall are analyzed in detail by changing expansion angles to calculate the radial pressure distribution and pressure drop, employed numerical simulation method, in this paper. The simulation results show that the expansion angle has a great influence on the attachment of liquid phase in annular flow to the curved wall, the radial pressure gradient is an important factor of the Coanda Effect which make the liquid phase of annular flow convey near the wall, and the radial pressure gradient will decrease but the pressure drop increase when the expansion angle becomes larger. These conclusions will provide useful reference in designing pipelines conveying the two-phase annular flow in oil-air lubrication system.

Derivation of radial electric fields using kinetic theory in tokamak

In the current study, radial electric field with fluid equations has been calculated. The calculation started with kinetic theory, Boltzmann and momentum balance equations were derived, the negligible terms compared with others were eliminated, and the radial electric field expression in steady state was derived. As mentioned in previous researches, this expression includes all types of particles such as electrons, ions, and neutrals. The consequence of this solution reveals that three major driving forces contribute in radial electric field: radial pressure gradient, poloidal rotation, and toroidal rotation; rotational terms mean Lorentz force. Therefore, radial electric field and plasma rotation are connected through the radial momentum balance.

Effect of the Radial Pressure Gradient on the Secondary Flow Generated in an Annular Turbine Cascade

This paper introduces an investigation of the effect of radial pressure gradient on the secondary flow generated in turbine cascades. Laboratory measurements were performed using an annular sector cascade which allowed the investigation using relatively small number of blades. The flow was measured upstream and downstream of the cascade using a calibrated five-hole pressure probe. The three-dimensional Reynolds Averaged Navier Stokes equations were solved to understand flow physics. Turbulence was modeled using eddy-viscosity assumption and the two-equation Shear Stress Transport (SST)k-ωmodel. The results obtained through this study showed that the secondary flow is significantly affected by the pressure gradient along blade span. The experimental measurements and the numerical calculations predicted passage vortex near blade hub which had larger and stronger values than that predicted near blade tip. The loss distribution revealed that secondary flow loss was concentrated near blade hub. It is recommended that attempts of reducing secondary flow in annular cascade should put emphasis on the passage vortex near the hub.

Influences of Inlet Swirl Distributions on an Inter-Turbine Duct: Part I—Casing Swirl Variation

The inter-turbine transition duct (ITD) of a gas turbine engine has significant potential for engine weight reduction and/or aerodynamic performance improvement. This potential arises because very little is understood of the flow behavior in the duct in relation to the hub and casing shapes and the flow entering the duct (e.g., swirl angle, turbulence intensity, periodic unsteadiness and blade tip vortices from upstream HP turbine blade rows). In this study, the flow development in an ITD with different inlet swirl distributions was investigated experimentally and numerically. The current paper, which is the first part of a two-part paper, presents the investigations of the influences of the casing swirl variations on the flow physics in the ITD. The results show a fair agreement between the predicted and experimental data. The radial pressure gradient at the first bend of ITD drives the low momentum hub boundary layer and wake flow radially, which results in a pair of hub counter-rotating vortices. Furthermore, the radially moving low momentum wake flow feeds into the casing region and causes 3D casing boundary layer. At the second bend, the reversed radial pressure gradient together with the 3D casing boundary layer generates a pair of casing counter-rotating vortices. Due to the local adverse pressure gradient, 3D boundary layer separation occurs on both the casing and hub at the second bend and the exit of the ITD, respectively. The casing 3D separation enhances the 3D features of the casing boundary layer as well as the existing casing counter-rotating vortices. With increasing casing swirl angle, the casing 3D boundary layer separation is delayed and the casing counter-rotating vortices are weakened. On the other hand, although the hub swirls are kept constant, the hub counter-rotating vortices get stronger with the increasing inlet swirl gradient. The total pressure coefficients within the ITD are significantly redistributed by the casing and hub counter-rotating vortices.