Disk Rotation Research Articles

Analysis of Single-Blade Passage and Full Circumference Large-Eddy Simulations of Turbine Rim Seal Flows

Abstract The flow in a 1.5-stage axial flow turbine with 16 vanes and 32 blades is investigated by large-eddy simulations with special focus on the analysis of the hot gas ingress through the rim seal into the upstream wheel space. Two setups with different solution domains are used. In the first large-eddy simulation, the full circumference of the turbine is resolved on a mesh with approximately 1 billion mesh cells. The second setup includes only a single-blade passage and is solved on a mesh with approximately 75 million cells. The analysis shows that the flow fields inside the upstream wheel space, i.e., between the disk of the upstream stator and the rotor disk strongly differ. In the 360 deg domain, two large-scale rotating vortex structures are observed, which have a strong impact on the ingress of main annulus gas into the wheel space. These structures cannot be captured in the single-blade passage domain. The instantaneous flow fields are further analyzed by dynamic mode decomposition to determine similarities and differences in the two flow fields. The comparison of the modes from the two setups reveals that the hot gas ingress from modes at the blade passing frequency generates a reduced sealing efficiency only at the outer radius of the wheel space. The additional presence of large-scale modes, however, reduce the sealing efficiency also in the inner wheel space. These results suggest that a single-blade passage simulation cannot be used for a reliable prediction of the hot gas ingress for the investigated turbine setup and operating condition.

Dynamometric Investigation on Airborne Particulate Matter from Automobile Brake: Impact of Disc Materials on Brake Emission Factor

In this work, we evaluated the impact of disc rotors of gray cast iron (GCI), nitrocarburized (NC), and superhard ceramic-coated (SCC) GCI on the brake wear PM emissions of passenger vehicles using dynamometric measurements. The brake emission factor (BEF) of the SCC was greatly reduced by more than a factor of 1/5 compared with those for the GCI and NC for both low-steel and non-steel friction materials. Surface topological and microstructural analyses confirmed that more severe wear was pronounced for the NC rotor compared with the SCC, as evidenced by large concave pits in the wear tracks. Analysis of the size-classified airborne PM suggests that reduced micron-sized particles, which originated from the GCI disc, were responsible for the lower BEF due to the increased hardness of the SCC.

Effect mechanism of multi-phase coupling on particle behaviors in magnetorheological foam plane finishing process

In this study, the effect mechanism of multi-phase coupling on particle behaviors in magnetorheological foam plane finishing (MRFPF) was researched to realize the collaborative control of particle distribution uniformity and polishing quality. To reach the goal, particle behaviors in MRFPF under the effect of fluid-solid coupling in magnetorheological foam were numerically studied by molecular dynamics (MD) simulation based on the force analysis that considering pressure drop due to fluid flow in foam pores. According to the simulation results, the influence law of different processing parameters on the radial distribution uniformity of particles was analyzed based on experimental analysis method. The results show that the polishing disk rotation speed and foam porosity have a positive effect on the radial distribution uniformity of particles, while the foam aperture affects little, and the greatest influence is produced by foam porosity which followed by polishing disk rotation speed and foam aperture. What's more, an optimal parameter combination with foam porosity 0.7, polishing disk rotation speed 30 rpm, and foam aperture 1 mm was determined by comprehensively considering the fluidity of MRPF and self-excited characteristics of abrasive particles in MRPF. Moreover, the advantages of MRFPF in improving the particle distribution uniformity and surface finishing quality to that of magnetorheological finishing were verified from numerical simulations and experiments.

Experimental and Numerical Investigations into the Effects of Rim Seal Structure on Endwall Film Cooling and Flow Field Characteristics

During the practical operation of gas turbines, relatively cooled air from the compressor and the rim seal is applied in order to prevent mainstream ingestion into the space between the rotor and stator disc cavities, which can prolong the service life of hot components. On the one hand, the purge flow from the rim seal will inevitably interact with the mainstream and result in secondary flow on the endwall. On the other hand, it can also provide an additional cooling effect. In this paper, four rim seal structures, including an original single-tooth seal (ORI), a double-tooth seal (DS), a single-tooth seal with an adverse direction of the coolant purge flow and mainstream (AS) and a double-tooth seal with an adverse direction of the coolant purge flow and mainstream (ASDS), are experimentally and numerically investigated with mass flow ratios of 0.5%, 1.0% and 1.5%. The flow orientation of the coolant from the rim seal is considered as one of the main factors. The pressure-sensitive paint technique is used to experimentally measure the film cooling effectiveness on the endwall, and flow field analysis is conducted via numerical simulations. The results show that the cooling effect decreases in the cases of DS and ASDS. AS and ASDS can achieve a better film cooling performance, especially under a higher mass flow ratio. Furthermore, the structural changes in the rim seal have little impact on the aerodynamic performance. AS and ASDS can both achieve a better aerodynamic and film cooling performance.

Free vibrations of axially loaded thin-walled shaft-disk rotors subjected to non-uniform temperature field

Research on vibrations of shaft-disk rotors in non-uniform thermal field is essential for the design of rotating machinery. In this paper, the dynamic model of axially loaded thin-walled shaft-disk rotors in axial non-uniform temperature field is developed, considering three-dimensional displacement fields of the shaft and disk. This model introduces the temperature-dependent properties of materials, and gyroscopic and centrifugal effects. Based on the Euler-Bernoulli beam theory and the Kirchhoff plate theory, Lagrange's equation is used to derive the differential equations of motion. By comparing with the results of the existing reference and finite element results, the accuracy of the present model is verified. The effects of the axial displacement of shaft, temperature-dependent material property, temperature difference, temperature distribution, disk position and axial preload on the free vibration of shaft-disk rotors are discussed. Results show that the present model can effectively predict free vibrations of shaft-disk rotors in axial non-uniform temperature field. The effect of thermal field on vibrations of shaft-disk rotors is affected by the rotational speed and disk location as well.

Experimental Measurements of Flow-Averaged Toroidal Vortices in Buoyancy-Dominated Rotating Cavities

Abstract The flow structures and heat transfer within rotating cavities of aero-engine axial compressors influence the thermal expansion of the rotor disks, and consequently the blade-tip clearances. To investigate the flow field at the bore and lower cavity region, experimental measurements have been acquired in an engine-representative test facility. Axial, tangential, and radial velocities were measured using a miniature five-hole probe at a range of axial and radial positions. Time-averaged results from 28 tests carried out at nondimensional parameters comparable to engine conditions: 1.3 × 104 ≤ Rez ≤ 8.2 × 104, 3.0 × 105 ≤ Reθ ≤ 3.2 × 106, 0.11 ≤ Ro ≤ 3.24, 0.14 ≤ βΔT ≤ 0.36 are presented in this paper. The axial and tangential velocity measurements conform to previous work, while the radial velocity component provides quantitative evidence of an asymmetric toroidal vortex in the cavity gap, biased toward the downstream disk. The vortex is characterized by the local vorticity and grows in strength and size as Rossby number increases above Ro = 0.34 to 1.63. The effect of βΔT on the vortex formation is negligible compared to the influence of the tangential Reynolds number as the local circulation is suppressed by the Coriolis forces at high rotational speeds. Both the tangential and radial velocity results suggest that as Ro is increased, the proportion of air that is radially ingested and expelled from a cavity decreases.

Optimization of operational parameters using RSM, ANN, and SVM in membrane integrated with rotating biological contactor

Membrane fouling is a critical bottleneck to the widespread adoption of membrane separation processes. It diminishes the membrane permeability and results in high operational energy costs. The current study presents optimizing the operating parameters of a novel rotating biological contactor (RBC) integrated with an external membrane (RBC + ME) that combines membrane technology with an RBC. In the RBC + ME, the membrane panel is placed external to the bioreactor. Response surface methodology (RSM) is applied to optimize the membrane permeability through three operating parameters (hydraulic retention time (HRT), rotational disk speed, and sludge retention time (SRT)). The artificial neural networks (ANN) and support vector machine (SVM) are implemented to depict the statistical modelling approach using experimental data sets. The results showed that all three operating parameters contribute significantly to the performance of the bioreactor. RSM revealed an optimum value of 40.7 rpm disk rotational speed, 18 h HRT and 12.4 d SRT, respectively. An ANN model with ten hidden layers provides the highest R2 value, while the SVM model with the Bayesian optimizer provides the highest R2. RSM, ANN, and SVM models reveal the highest R-square values of 0.97, 0.99, and 0.99, respectively. Machine learning techniques help predict the model based on the experimental results and training data sets.

ANALYTICAL DETERMINATION OF ASYMMETRIC PARAMETERS DISK HARROW

Having analyzed the technologies of pre-sowing field preparation, it should be concluded that the soil is processed before sowing with cultivators, disk, tooth and needle harrows, as well as soil tillers. Rolling before sowing ensures the destruction of soil lumps, as well as partial leveling of the field surface. However, the task of qualitative preparation of the field for sowing with the use of disk harrows is currently insufficiently solved, therefore it is necessary to substantiate the rational design parameters of an asymmetric disk harrow containing working bodies, which include, in particular, spherical disks. The following should also be noted, if the harrow is intended for use on harder, for example, chernozem soil, then the rod is attached to the hole further from the axis of rotation of the two-armed lever, which ensures the distance of the attachment device from the middle line of the harrow, which conditions the preservation of its balance when working on such soil. The process of rectilinear movement and rotation of spherical disks with a certain radius R in the soil at a depth h, which are installed at different angles to the direction of harrow movement, is considered. In the work, the impact of spherical disks with the remains of stubble, chopped straw was considered, it was established that spherical disks should be clamped between the sharpened cutting edge and the soil and cut them. It has been established that for guaranteed rotation of a spherical disk in the soil with minimal slippage and rolling resistance, its diameter must be substantiated. Since the spherical disk for soil cultivation is installed at an angle of attack α, to the direction of harrow movement, the projection of the spherical disk in the longitudinal-vertical plane is an ellipse with semi-axes. The rational diameter of the spherical disc of the asymmetric disc harrow under the conditions of its rotation in the soil with minimal values of sliding and rolling resistance, as well as a high-quality process of cutting the soil, stubble and soil displacement, is theoretically substantiated. It was established that the rational values of the diameter of the spherical disc of the asymmetric disc harrow depends on the depth h of soil treatment, the angle of attack α and the physical and mechanical properties of the soil.

MODELING OF ROUGH ROTARY MILLING OF CRANKSHAFT PINS

The development of the modern automotive industry requires a quick adaptation of new production methods. This is possible thanks to software capable of simulating manufacturing processes. The paper discusses the modeling of the machining operation of a crankshaft’s crankpins for a diesel engine with the use of the planetary milling method. i.e., modeling of milling operation when a disc milling cutter, having its cutting inserts directed inwards, is performing rotary motion, and at the same time, the axis of this milling cutter circulates around the axis of a machined crankpin. For this purpose, a geometrical model of the machining of the crankshaft’s crankpin has been developed. Based on the design documentation of the crankshaft of the 4C90 type diesel engine and the documentation of the Steyr internal disc milling cutter, their CAD models have been developed, and the both models were linked together with suitable kinematic dependencies. In the next step, the crankpin having a length of 25 mm was divided by planes (in quantity lp=21) into 1.25 mm sections. On the main cutting edge of two cutting inserts of the disc milling cutter, points were marked at intersection locations with these planes. Using the Inventor 2016 system, twelve spline curves have been generated for each plane because each plane intersects 12 cutting inserts mounted in cassettes positioned around the circumference of the body of the disc milling cutter. Next, the spline curves were brought to a common coordinate system, rotating them at an angle resulting from the positioning of the cassettes with cutting inserts in the body of the disc milling cutter. Prepared in such a way, spline curves were written in dwg format, which allowed for trimming of the spline curves at the circle with a radius of rcp = 27.90 mm, corresponding to the radius of the crankpin after milling, considering grinding allowance (ø55h6 + 0.80 mm grinding allowance). As a result, it enabled to leave sections of the arcs tangential to the diameter ø55.80 mm and, in such a way, generate the outline of the shape of the crankpin using the REGION command for 21 cross-sections. The outline of the cylindricity of the crankpin was obtained using the strategy of outlines of the roundness, which were generated earlier; this strategy consisted in the collection of 360 points on the circumference of 21 mutually parallel sections cut by planes perpendicular to the axis of the crankpin. To determine the effects of the circular feed rate of the circulating move of the axis of rotation of the internal disc milling cutter on the accuracy of the machining, simulations of the shape of the crankpin were performed for three values of the feedrate: vf = 1200 mm/min; vf = 2100 mm/min and vf = 3000 mm/min. The spline curves with a determined (depending on the duration of the simulation) number of points: 3500, 2100 and 1409 were obtained for each simulation. The calculated cylindricity deviation for the feedrate vf = 1200 mm/min amounted to CYLrck = 0.2272 mm, for the feedrate vf = 2100 mm/min – CYLrck = 0.2406 mm, while for the feedrate vf = 3000 mm/min – CYLrck = 0.2929 mm.

Flute Instability Effects for Disk Accretion onto Neutron Stars with Strong Magnetic Fields

The flute instability at the inner edge of a thin diamagnetic accretion disk is analyzed. Themagnetic field configuration model fromAly (1980) is used. We have analyzed a modified dispersion relationfor the flute instability that takes into account the Keplerian disk rotation. We have derived the inner radiusof the accretion disk within our analysis of the flute instability.We show that the inner radius does not differfrom the Alfve´ n radius for spherical accretion to within a dimensionless coefficient, with the proportionalitycoefficient depending only on the turbulence alpha parameter and the relative disk thickness (h/r).

Vibration Control of a Multi-Disc Rotor System with Active Lateral Bearings and Disturbance Estimation

A rotor system used in a wide range of engineering applications generally consists of a rotor shaft, multiple discs, blades and other essential components, generating a multi-disc rotor arrangement. System uncertainties caused by unbalanced discs and disc mass variation, compounded with external disturbances under different operating conditions, can lead to a variation in rotor-dynamic characteristics with multiple structural resonances, potentially causing an excessive level of rotor lateral vibration. Therefore, to effectively suppress lateral vibration for such a multi-disc rotor system, an active vibration control approach using active lateral bearings with disturbance estimation is presented in this work. The utilized active lateral bearings can generate necessary bearing displacement regulations to eliminate the bearing forces so to effectively control the lateral vibration of the rotor system. The disturbance estimation approach is used to estimate the unknown uncertainties associated with the system's internal dynamics and external disturbances affecting the rotor system, incorporating an extended state observer (ESO). Utilizing the total disturbance estimated by the ESO to cancel out the effects of the disturbance using active lateral bearings, the rotor lateral vibration can be satisfactorily suppressed with sufficient control robustness against uncertainties in the rotor internal dynamics, particularly associated with the degree of mass unbalance of rotor discs, demonstrating the effectiveness of the active vibration control approach for suppressing vibration in a rotor system.

Galaxy kinematics and mass estimates at z ∼ 1 from ionized gas and stars

ABSTRACT We compare ionized gas and stellar kinematics of 16 star-forming galaxies (log (M⋆/M⊙) = 9.7–11.2, SFR =6 − 86 M⊙ yr−1) at z ∼ 1 using near-infrared integral field spectroscopy (IFS) of Hα emission from the KMOS3D (the K-band Multi-Object Spectrograph 3D) survey and optical slit spectroscopy of stellar absorption and gas emission from the LEGA-C (Large Early Galaxy Astrophysics Census) survey. Hα is dynamically colder than stars, with higher disc rotation velocities (by ∼45 per cent) and lower disc velocity dispersions (by a factor ∼2). This is similar to trends observed in the local Universe. We find higher rotational support for Hα relative to [O ii], potentially explaining systematic offsets in kinematic scaling relations found in the literature. Regarding dynamical mass measurements, for six galaxies with cumulative mass profiles from Jeans Anisotropic Multi-Gaussian Expansion (JAM) models the Hα dynamical mass models agree remarkably well out to ∼10 kpc for all but one galaxy (average $\Delta M_{\rm dyn}(R_{e,\rm F814W})\lt 0.1$ dex). Simpler dynamical mass estimates based on integrated stellar velocity dispersion are less accurate (standard deviation 0.24 dex). Differences in dynamical mass estimates are larger, for example, for galaxies with stronger misalignments of the Hα kinematic major axis and the photometric position angle, highlighting the added value of IFS observations for dynamics studies. The good agreement between the JAM and the dynamical models based on Hα kinematics at z ∼ 1 corroborates the validity of dynamical mass measurements from Hα IFS observations, which can be more easily obtained for higher redshift galaxies.

Unsteady Al2O3-Cu/H2O hybrid nanofluid flow over a rotatable stretching disk with heat generation and deceleration: Stable dual solutions

This study reveals the impact of heat generation and variable strength of rotation on the unsteady flow of a hybrid nanofluid over a rotatable disk with stretching characteristics and deceleration. A novel mathematical model specifically tailored to elucidate the behavior of a hybrid nanofluid is proposed. By employing similarity variables, the governing model is reformulated into ordinary differential equations (ODEs). The bvp4c function (MATLAB) is employed to efficiently obtain the numerical solutions of these ODEs. To provide a comprehensive study, a stability analysis is also conducted to investigate the properties associated with the non-unique dual solutions generated by the model. Dual solutions are generated, and both are analyzed to be stable. A lower amount of heat generation with greater disk rotation strength is recommended to further improve the heat transfer rate of the model. The bifurcation point is absent within the setup ranges of the parameters in the present study, which suggests a well-maintained laminar flow simulation. The findings of this study offer valuable insights and can assist other researchers in improving their understanding and modeling of similar fluid flow systems, particularly hybrid nanofluid flow systems.

Numerical and regression analysis of horizontal magnetic field in slippery nanofluid flow with Arrhenius activation energy

The significance of magnetic field in the fluid flow models is important in order to stabilize the flow stream. The present work explores the horizontal magnetic field influences in steady-state laminar swirl Newtonian nanomaterial fluid flow triggered by disk rotation. To categorize the thermal performance, a well-established theory of nanofluid (Buongiorno model) is implemented in flow phenomenon. Thermal radiative term is demonstrated in the energy transportation equation. The impact of chemical species is investigated by the expression of AAE (Arrhenius activation energy). The flow model is normalized in accordance with von Kármán similarity transformations. The resulting normalized system of equations is converted to a system consisting of first order differential equations and then is solved by Runge-Kutta-Fehlberg (RKF-45) built-in method. The physical results are discussed graphically on velocity, temperature, and concentration streams. Shear stresses, local Nusselt and Sherwood numbers are calculated at the surface of the rotating disk. In addition, the regression process is utilized to address the parameters impacts on the variables. The stabilizing impact of magnetic field along radial direction is noticed by means of direction angle close to 00 and 900. Velocity profiles in radial direction are enhanced by the velocity slip parameter. Concentration filed is increased through activation energy. The inclination angle has a weak impact on heat transfer rate. Finally, a comparison is established with the published literature in limiting scenario.

Flow characteristics of an automotive compressor with an additively manufactured rotor disc

Flow characteristics of an automotive compressor with an additively manufactured rotor disc

A Rotating Accretion Disk around MWC 297, a Young B1.5Ve Star

High-resolution spectra with iSHELL on IRTF in the K and M bands of the young, heavily accreting B1.5Ve star MWC 297 show numerous double-peaked CO lines. These CO lines originate in an inclined gaseous disk in Keplerian rotation. MWC 297 is the only early B star known to show a Keplerian disk in CO. Analysis of the spectra shows that 12CO 1–0 is optically thick for the low excitation lines. Even the 13CO 1–0 and 12CO 2–1 have somewhat optically thick lines at low J levels. We find that the CO emission in the disk can be fitted with CO being in a narrow ring at a radius of 12 au, with a temperature of 1500 K and a CO column density of 1.6 × 1018 cm−2. This model underestimates the line strength of high-J lines, indicating that they are excited by fluorescence. The CO overtone lines have a similar temperature. The 13CO lines are much brighter than expected from interstellar isotope ratios. The 13CO lines are wider than the 12CO ones, suggesting different excitation conditions. The same is true for 12CO 2–1. We see strong absorption in 12CO and 13CO 1–0 at low J levels, which is due to two cold foreground clouds. These clouds, one with a temperature of 8.3 K and a column density of 6.7 1017 cm−2 and the other one colder and with lower column density, can fully account for the observed extinction toward MWC 297.

An analytical solution for convective heat transfer in conical gaps with either cone or disk rotating

This study is devoted to solving two problems of laminar fluid flow in a conical gap with small conicity angles up to 4°: cone rotation with a fixed disk, and disk rotation with a fixed cone. A new improved asymptotic expansion method for energy equation was used to obtain an approximate analytical solution to the convective heat transfer equation. The characteristic Reynolds number ranged from 0.001 to 1.0, the Prandtl number took values 0.71, 1, 5, and 10, and the exponent n* in the power-law for the disk temperature was 0 (constant disk temperature) or 2 (strongly radially increasing disk temperature). A novel model for the asymptotic expansion of the temperature profile and a novel expansion parameter Sv = Re2Pr, which is a new dimensionless number proposed for the first time in the known scientific literature, was developed. For the first time, new approximate analytical solutions were obtained for temperature profiles and Nusselt numbers on the disk and cone for both problems that agree well with the self-similar solution, if the Re and Pr numbers do not exceed threshold values. These analytical solutions are advantageous in analysis of experimental data and further development of one-dimensional models for gases, water, and aqueous solutions (Pr = 0.71–10).

A Wall Effects and Means of Controlling the Evolution of Swirling Flows with Vortex Breakdown

This paper investigates numerically the bubble-type vortex breakdown apparition in the case of closed rotating flows of a viscous, axisymmetric, and incompressible fluid. First, a truncated conical/cylindrical cavity of spherical end disks is used to simulate and analyze the vortex structure under rigid surface conditions. The geometric effects of the enclosure are also studied. Vortex breakdown is demonstrated beyond the lower disk rotation rate threshold by introducing the no-slip condition imposed on the upper wall. The objective is to explore ways of controlling the evolution of this physical event by modifying the confinement conditions upstream of the vortex rupture. Particular attention is also paid to the effective kinematic viscosity, thermal diffusivity and geometric control of recirculation zones on the axis of rotation (axial bubble type). The second geometry consists of a spherical annulus formed by two concentric hemispheres in differential rotation under plat-free surface conditions. The results show that rotation of the inner hemisphere induces a vortex bubble on the polar axis. In contrast, the outer hemisphere rotation induces a toroidal vortex on the equator.

Technoeconomic comparison of optimised bioreactor-filtration systems for mAb production

Primary post-cultivation biomass recovery (cell culture removal from API-rich solutions) is essential in biopharmaceutical manufacturing. Centrifugation and depth filtration are dominant industrial primary recovery technologies, but mechanistic dynamic models suitable for performance evaluation are scarce. This paper uses established literature models to present and analyse optimal operation strategies for integrated process designs of fed-batch or perfusion CHO bioreactors (for mAb cultivation via CHO cultures), with an explicit rotational disk (dynamic crossflow) filtration model (for primary recovery). A rigorous DAE filter model (Marke et al., 2020) is employed here, to evaluate system performance. Dynamic optimisation of bioreactor-filter systems has been completed for different bioreactor types, filter arrangements and feed manipulations, considering the same annual mAb plant production target. A technoeconomic analysis of optimal designs addresses industrial viability, confirming a clear cost advantage of fed-batch reactors combined with stacked membrane microfilters.

A lattice Boltzmann model for the interface tracking of immiscible ternary fluids based on the conservative Allen-Cahn equation

A lattice Boltzmann (LB) model for the interface tracking of immiscible ternary fluids is proposed based on the conservative Allen-Cahn (A-C) equation. A nonlocal equilibrium distribution function source term is adopted in the LB equation to eliminate the unwanted numerical items. With the new LB equation and the carefully designed equilibrium distribution function, Chapman-Enskog analysis shows that the present model can correctly recover the conservative A-C equation with second-order accuracy. A series of benchmark cases have been used to validate the accuracy and stability of the present model, including the classical diagonal translation of two concentric circular interfaces, the rigid-body rotation of Zalesak's disk, and the periodic shear deformation of two tangent circular interfaces. By coupling the dynamic LB model for Navier-Stokes equations, the stationary droplets, the spreading of a liquid lens, the spinodal decomposition, and the Raleigh-Taylor instability have also been simulated in the framework of ternary fluids. Utilizing the geometric interpolation method, the wettability effect of the horizontal boundary is considered and numerical tests with different wall contact angles have been performed to verify the applicability of the present model. All the numerical tests show that the present model can capture the interfaces among the immiscible ternary fluids accurately. Furthermore, using fewer discrete velocity directions, the present model shows higher numerical accuracy and stability compared with other existing numerical models. Therefore, it is promising to improve computational efficiency.