Circumferential Angle Research Articles

Two-year randomized controlled trial of circumferential versus segmental ab externo angle surgery in patients with primary open angle glaucoma.

To compare the surgical outcomes of visco-circumferential-suture-trabeculotomy (VCST) and rigid probe segmental viscotrabeculotomy (VT) in primary open-angle glaucoma (POAG). A prospective randomized controlled study. Patients presenting with POAG and operated upon in Mansoura Ophthalmic Center in Mansoura, Egypt between February 2017 and September 2021 were enrolled. Study eyes were randomized to either VCST or VT and follow up extended for 24 months. Success was defined as an intra ocular pressure (IOP)≤18 mmHg with a 40% reduction from baseline. Complications were noted. The study enrolled 166 (82 in the circumferential group) eyes of 107 patients. There were no statistically significant differences between both groups in any demographic or preoperative clinical characteristics. The IOP trend demonstrated marked initial reduction (from 32.3±2.4 and 31.8±2.6 mmHg preoperatively in VCST and VT groups respectively) followed by a slow gradual rise over subsequent follow-up settling at lower IOP values in the circumferential (12.4±1.2 mmHg) than in the segmental group (15.5±0.9 mmHg) (p<0.001), both settling at significantly lower levels than preoperative values. The survival curve demonstrates complete success rates at 12, 15, 18, and 24 months were 98.8%, 96.4%, 95.1%, and 85.4% in the circumferential group and 98.8%, 92.9%, 91.7%, 79.8% in the segmental group respectively. Minimal self-limiting hyphema was universal in all study eyes. Angle procedures -segmental and circumferential- are effective in lowering the IOP for at least 2 years in eyes with POAG, with circumferential angle surgery providing a greater reduction of IOP and requiring fewer subsequent glaucoma procedures.

Anterior Segment Pharmacological Accommodative Changes and Its Impact on the Circumferential Anterior Chamber Angle after ICL V4c Implantation: Angle following ICL implantation.

To investigate the pharmacological accommodative changes of the anterior segment and its impact on the circumferential anterior chamber angle (ACA) after implantable collamer lens (ICL) implantation using swept-source optical coherence tomography (SS-OCT). Eye and ENT Hospital, Fudan University, Shanghai, CHINA. Prospective randomized contralateral eye study. Eight men and 24 women (mean age, 28.2 ± 5.8 years; range, 19-42 years); 64 eyes were included at 3 months after ICL implantation. One eye per patient was randomly assigned to undergo tropicamide instillation (mydriasis group), and the contralateral eye underwent pilocarpine instillation (miosis group). SS-OCT examinations were performed before and after instillation to measure angle parameters. Trabecular-iris angle 500 (TIA500), angle opening distance 500 (AOD500), trabecular-iris space area (TISA500), angle opening distance circumference area 500 (AODA500), trabecular-iris circumference volume 500 (TICV500), and central vault (ICL to crystalline lens [ICL-L]) were evaluated. Relative to baseline levels, TIA500, AOD500, and TISA500 values all increased significantly in both groups (all P < 0.01). AODA500 and TICV500 values increased by 19.7% and 12.1%, respectively, in the mydriasis group (all P < 0.001), and these values similarly increased by 23.4% and 27.7%, respectively, in the miosis group (all P < 0.001). After instillation, the ICL-L decrease in the miosis group was significantly larger than that in the mydriasis group (P = 0.004). Mean AOD500, TISA500, and TICV500 in the miosis group were significantly larger than those in the mydriasis group (all P ≤ 0.036), especially at 8 and 10 o'clock (all P ≤ 0.014). Correlation analyses indicated that the increase in anterior chamber angle parameters was positively correlated with the change in ICL-L for both groups. Pilocarpine induced a more significant increase in ACA than tropicamide, because of different mechanism of anterior segment changes. We recommend circumferential meridian scan to assess angle status.

Numerical study on flow pattern transition, liquid film and heat transfer for R1233zd/FC72 mixtures across tube bundles

The non-azeotropic mixtures phase-change flow across tube bundles is widely used in the refrigeration industry. A simulation model of R1233zd/FC72 mixtures is presented to study flow pattern transition and heat transfer across tube bundles. Volume of Fluid (VOF) model is used to determine the flow pattern. An experiment is conducted to validate the simulation model with average deviation of 8.97%. The results showed that the flow pattern transition appears for various conditions. In addition, the liquid film thickness and heat transfer are analyzed, focusing particularly on the impact of various mixture components. With increasing vapor quality, the flow pattern transfers from sheet flow to semi-annular flow and then to droplet flow. Sheet to semi-annular flow transition occurs for a vapor quality of 0.4–0.6, and semi-annular flow transfers to droplet flow for a vapor quality of 0.7–0.8. For sheet flow, the local heat transfer coefficient on the tube surface is the highest at 90° (circumferential angle) from the summit point of the cross-sectional tube circle due to the thinnest liquid film. The liquid film turns thinner with increasing mass fraction of R1233zd and vapor quality. Increasing the mass fraction of R1233zd and vapor quality promotes heat transfer. However, the flow pattern transfers from sheet flow to the other ones, the heat transfer coefficient starts to decrease. The heat transfer coefficient is the highest for a vapor quality of around 0.4–0.5 and a mass fraction of R1233zd of around 0.7–0.9.

Research on surface integrity of titanium alloy in V-groove micro-textured ball-end milling cutter

In order to realize chip guiding control in titanium alloy machining, reduce the negative influence of unstable chip flow direction on the milling environment, and improve the performance and reliability of parts, this article adopts the V-groove micro-texture carbide tool as the research object and takes the laser preparation of the V-groove micro-texture as a breakthrough point, analyzes the influence of laser parameters on the aspect ratio of V-groove micro-texture, and optimizes the laser parameters. The titanium alloy milling test platform was built to analyze the influence of the micro-texture parameters of the V-groove on the surface integrity of the workpiece, reveal the action mechanism, and optimize the relevant parameters based on the artificial bee colony algorithm. The results show that laser power has the largest influence on the aspect ratio of the groove. The power determines the melt content in the groove and influences the width and depth of the micro-texture. The optimized laser combination parameters are: laser power 42.5 W, scanning speed 10 mm/s scanning times nine times, scanning frequency 30 kHz, and spot diameter 30 μm. The V-groove micro-texture on the tool surface can change the chip flow direction, reduce the contact area of the chip, accommodate the cutting particles, and improve heat conduction, reducing cutting resistance and friction, thereby optimizing cutting control distance, thereby improving the surface integrity of the workpiece becomes. The optimized V-groove micro-texture parameters are as follows: V-groove angle X = 46.2°, V-groove height H = 175 μm, radial spacing L = 259.4 μm, circumferential angle J = 2.1°, and distance from the edge K = 120 μm.

Data-driven prediction of convective heat transfer coefficients in internal walls of aero-engine bearing chambers using Mind Evolution Algorithm-Enhanced Bayesian regularization neural networks

In the bearing chambers of aero-engines, the complex nature of the oil–gas flow complicates the precise calculation of heat transfer coefficients. Addressing computational discrepancies, firstly, this study establishes a correlation analysis method, which considers the relationship between several independent variables including the geometric shape of the bearing chamber, rotational speed, oil flow rate, thermal sealing air mass, circumferential angle, axial position, and the dependent variable, which is the logarithmic Nusselt number on the internal wall. Secondly, four models are developed using Multiple Linear Regression, Back Propagation Neural Network, Deep Belief Neural Network, and Convolutional Neural Network with Long Short-Term Memory Network, yielding Mean Relative Percentage Errors (MRPE) of 5.14%, 2.80%, 4.66%, and 4.12%, respectively. Due to the limited predictive performance of these models, the neural network topology is further optimized. After repeated trial-and-error calculations, the neural network with three hidden layers was found to be the most effective. Finally, a novel BP Neural Network optimized by the Mind Evolution Algorithm-enhanced with Bayesian regularization (MEA-BPNN-Bayesian) model is proposed forpredicting the local convective heat transfer, achieving an MRPE of 1.71%. The model accurately predicted heat transfer coefficients, opening up new ways to improve heat management in bearing chambers.

Numerical Simulation and ANN Prediction of Crack Problems within Corrosion Defects.

Buried pipelines are widely used, so it is necessary to analyze and study their fracture characteristics. The locations of corrosion defects on the pipe are more susceptible to fracture under the influence of internal pressure generated during material transportation. In the open literature, a large number of studies have been conducted on the failure pressure or residual strength of corroded pipelines. On this basis, this study conducts a fracture analysis on buried pipelines with corrosion areas under seismic loads. The extended finite element method was used to model and analyze the buried pipeline under seismic load, and it was found that the stress value at the crack tip was maximum when the circumferential angle of the crack was near 5° in the corrosion area. The changes in the stress field at the crack tip in the corrosion zone of the pipeline under different loads were compared. Based on the BP algorithm, a neural network model that can predict the stress field at the pipe crack tip is established. The neural network is trained using numerical model data, and a prediction model with a prediction error of less than 10% is constructed. The crack tip characteristics were further studied using the BP neural network model, and it was determined that the tip stress fluctuation range is between 450 MPa and 500 MPa. The neural network model is optimized based on the GA algorithm, which solves the problem of convergence difficulties and improves the prediction accuracy. According to the prediction results, it is found that when the internal pressure increases, the corrosion depth will significantly affect the crack tip stress field. The maximum error of the optimized neural network is 5.32%. The calculation data of the optimized neural network model were compared with the calculation data of other models, and it was determined that GA-BPNN has better adaptability in this research problem.

Experimental study on the scaling law of the heat exchange tube surface in the process of low-temperature single-effect distillation of high-mineralized mine water

High-mineralized mine water, due to its characteristics such as high mineralization degree, will have scaling phenomena on the surface of the heat exchange tube during the desalination treatment process, resulting in a reduction in the water production efficiency of the equipment and affecting the normal operation. To reduce the cost of water production and improve the service life of distillation equipment, this paper independently designs and builds a low-temperature single-effect distillation high-mineralized mine water experimental system to study the influence of operating parameters (temperature, spray density, concentration ratio, and system pressure) on the scaling law on the surface of the heat exchange tube. The distribution and characteristics of scale deposits on the surface of the heat exchange tube are analyzed through the growth rate and microscopic morphology of the scale deposit. The results indicate that the scaling on the surface of the titanium plate is mainly in the needle-like and rod-like morphology of CaCO3 aragonite, and a small amount of CaSO4 and calcite are generated with the increase of temperature. It was found that within the range of spray density from 0.0509 kg/(m·s) to 0.0625 kg/(m·s), concentration ratio from 2.3 to 2.7, and system pressure at 36.3 kPa, it is beneficial to the evaporation heat transfer of the heat exchange tube and the reduction of scaling generation. At the same time, it is found that the scaling of the first row of heat exchange tubes is mainly within the range of circumferential angle from 0 to 100 degrees, and the scaling of the second row and the third row of heat exchange tubes is mainly within the range of circumferential angle from 110 to 170 degrees. The research results of this paper provide support for the design and operation of the low-temperature multi-effect treatment system for mine water in engineering, promote the process of zero discharge of high-mineralized mine water in Xinjiang, China, and improve the resource utilization rate of high-mineralized mine water.

Fabrication and mechanical characterization of near field electrospun bioresorbable vascular grafts with fibrous architecture mimicking the arterial extracellular matrix

Cardiovascular disease, arteriosclerosis, is characterized by the thickening of blood vessel (arteries) walls restricting blood flow and is a global health problem. One treatment option is a surgical procedure utilizing an autologous or synthetic vascular graft to bypass or replace the diseased arterial segment. The goal of this study was to fabricate and mechanically characterize near field electrospun bioresorbable vascular grafts with a fibrous architecture that mimics the arterial extracellular matrix. Polydioxanone vascular constructs with circumferential fiber alignment angles of 15°/75° and 30°/60° (0° representing circumferential fiber alignment) were fabricated using a custom built near-field electrospinning (NFES) system. The vascular construct mechanical properties were compared to the saphenous vein (SV) and internal mammary artery (IMA) through longitudinal and circumferential uniaxial mechanical testing, suture retention, and burst pressure evaluations. The results demonstrated that the 15°/75° templates were closest to mimicking the native vessel target properties as compared to the 30°/60°; however, neither of the vascular template designs achieved or exceeded all the target values. For the ultimate tensile strength, both the constructs met the SV value on the circumferential axis (2.61 MPa) and the IMA value on the longitudinal axis (4.3 MPa). In terms of suture retention, the 15°/75° template was the only construct that was in the IMA and SV targeted range of 138–200 gf. Finally, the burst pressure testing results indicated that neither of the vascular constructs achieved the level of the SV or IMA (1600–3196 mmHg), however, the 15° constructs were within the lower error of the SV. In conclusion, with further design modifications, NFES constructs have demonstrated promise as small-diameter vascular grafts by mimicking native arterial architecture and mechanical properties.

Diagnostic Abilities of Three-Dimensional Anterior Segment Optical Coherence Tomography in Detecting Angle Closure.

Three-dimensional (3D) angle parameters and cutoff values for detecting angle closure were proposed. The 3D parameters demonstrated excellent diagnostic performance. Certain horizontal two-dimensional (2D) parameters [ie, trabecular iris space area (TISA)-750, angle opening distance (AOD)-750, and AOD-500] can attain similar performance to their high-performing 3D counterparts. To investigate the diagnostic performance of single horizontal 2D versus 3D angle parameters from swept-source anterior segment optical coherence tomography (CASIA2) in detecting angle closure. The cross-sectional study included 118 phakic patients (59 open angles, 59 closed angles). AOD, angle recess area (ARA), and TISA at 250, 500, and 750μm from scleral spur were measured in 360-degree radial-scan images. The 3D information of each measurement was analyzed in 2 patterns: (1) average 3D parameter-the averaged value from 360-degree angle values and (2) estimate 3D parameter-the estimation of surface area of circumferential angle inlet (using AOD) or circumferential angle volume (using ARA and TISA). The areas under the receiver operating characteristic curve [areas under the curve (AUCs)] of eighteen 3D parameters were compared with 2D horizontal parameters. Among 3D parameters, AOD-500 estimate 3D gave the highest AUC (AUC: 0.950, cutoff: 6.09mm 2 ), followed by AOD-750 estimate 3D (AUC: 0.948, cutoff: 8.26mm 2 ). 3D parameters significantly increased the AUC of ARA-250 and TISA-250 (all P < 0.02) compared with the 2D parameters. No significant improvement in AUC was demonstrated for AOD-250 and all parameters at 500 and 750μm. No significant difference in AUC was found among the 6 maximum AUC parameters, which were AOD-750 horizontal 2D, AOD-500 estimate 3D, TISA-750 horizontal 2D, AOD-500 horizontal 2D, AOD-750 estimate 3D, and TISA-750 average 3D. The 3D-angle parameters had high performance in detecting angle closure. However, comparing a horizontal measurement to 3D parameters, the AUC improvement was mostly insignificant.

Vibration transmission characteristics of the pyramidal cylinder lattice truss structure

In this work, an innovative cylindrical metamaterial inspired by origami was developed. It featured arrays of pyramid units arranged both circumferentially and axially. The vibration transfer characteristics were determined using numerical method (Frequency Domain Frequency Response Solver of COMSOL) and dynamic testing (Scanning Vibrometer System). The results indicate that the structure effectively attenuates vibrations within the 0–6000 Hz range. Adjusting key geometric parameters can widen or shift vibration attenuation bands toward low–frequencies. Increasing the rod diameter weakens the vibration attenuation capability, while an increase in circumferential and axial angles has a positive impact on the frequency band for vibration attenuation. The significance of this work lies in providing an appropriate method to enhance vibration attenuation for the design and optimization of engineering structures.

Numerical investigation into turbulent drag reduction via the application of pufferfish spine-inspired cone microstructures in Suboff models

The effective reduction of seawater drag is pivotal in enhancing the speed and minimizing the energy consumption of submarines, which has significant implications in the fields of energy and defense. Surface bionics has emerged as one of the leading techniques for drag reduction. Current research primarily focuses on replicating the groove-like structures observed on shark skins and the flexible properties of dolphin skins. However, the application of cone microstructures on submarine surfaces remains relatively underexplored. In this study, a novel arrangement of bionic drag-reducing microstructures is employed to modify the turbulence structure surrounding the submarine by incorporating bionic cone microstructures at both the front and rear ends of the submarine. Numerical simulations were performed using the SST k-ω turbulence model to evaluate the impact of these frontal microstructures on drag reduction under varying Reynolds numbers, spacings, and positions, as well as the tail microstructures’ effect at different Reynolds numbers, heights, and circumferential separation angles. The findings reveal that positioning microstructures at the submarine’s head increases the drag reduction rate proportionally with the distance from the apex, displaying an inverse relationship between spacing and drag reduction rate. Conversely, an increase in cone separation angle at the tail leads to a decrease in the overall drag reduction rate. At the same time, an inverse proportionality is observed between cone height and drag reduction rate. This suggests that cone microstructures play a dual role: mitigating friction drag greatly and augmenting pressure drag, thereby achieving overall drag reduction. Moreover, these cone microstructures disrupt eddy currents within the boundary layer surrounding the submarine, restraining the propagation of turbulent momentum transfer in both the head and tail regions. This research not only pioneers a novel drag reduction strategy for underwater vehicles but also sparks new avenues for their optimized surface design.

Study of the Effect of Static Eccentricity on Vibration Damping Properties of Squeeze Film Dampers Considering the Two-Phase Flow Case

To analyze the effect of static eccentricity on the air ingestion distribution and vibration damping properties of the SFD, a numerical simulation study of SFDs considering two-phase flow was carried out based on CFD using a transient solution method and dynamic mesh technique. The results show that the angle between the static eccentricity direction and the circumferential direction of the oil supply hole increases and the air ingestion area in the oil film expands. In contrast, the oil film damping decreases, and the larger the static eccentricity distance, the greater its effect on the air ingestion area in the oil film. When the circumferential angle is small, the oil film damping increases with the increase of static eccentricity distance, and when the circumferential angle is large, the oil film damping decreases with the increase of static eccentricity distance and then increases. With the increase of static eccentricity distance, the air ingestion area at both ends of the oil film increases. At the same time, studying the effect of dynamic eccentricity shows that as the dynamic eccentricity increases, the oil film damping first decreases and then increases, and the air ingestion area increases. Comparing the 1 hole, the 2 hole, and the 3 hole oil supplies, the air ingestion area is significantly larger in the 1 hole oil supply than in the 2 hole or the 3 hole oil supplies, and the oil film damping of the 1 hole oil supply is smaller than the oil film damping of the 2 hole or the 3 hole oil supplies. It can be seen from the present study that in the actual installation of the SFD, when the circumferential angle is less than 60°, the static eccentricity can be increased appropriately. When the circumferential angle is greater than 60°, the static eccentricity can be appropriately reduced.

An experimental and simulation study on the velocity distribution of the falling film on a horizontal tube in jet mode

The velocity characteristics of falling film on horizontal tube affect the heat transfer efficiency. To date, experimental studies on velocity distribution of liquid film on tube surface are very scarce. In this paper, the mean velocity of liquid film is measured using particle tracking velocimetry (PTV). A simulation is also conducted to investigate the flow characteristics of falling film. Results show that the spreading of liquid film undergoes two stages: circular spreading and circumferential flow. In circumferential direction, the liquid film tangential velocity shows different law in planes of L* = 0–0.3 and L* = 0.4/0.5. The tangential velocity decreases and then increases as axial distance increases. Simulation results agree well with the experimental results within experimental angle range. The liquid film axial velocity is always zero at L* = 0. When L* = 0.1–0.5, the axial velocity decreases as circumferential angle increases and gradually tends toward zero.

Flow and aerodynamic noise control of a circular cylinder by local blowing

In this experimental study, the impact of symmetric local blowing on suppressing the vortex-induced noise of a circular cylinder was investigated. A highly instrumented cylinder with pressure taps and a series of blowing chambers was used to inject air along the span (seven times the cylinder diameter) at circumferential angles $\theta _{b}={\pm }41^{\circ }$ , ${\pm }90^{\circ }$ and ${\pm }131^{\circ }$ corresponding to the boundary layer, shear layers on the cylinder and separated shear layers, respectively. The investigation aimed to understand the noise reduction mechanism of local blowing by conducting near-field pressure and far-field noise measurements in synchronisation with flow field velocity measurements. Near-field pressure was measured around the circumference of the cylinder using a remote-sensing technique and planar particle image velocimetry was implemented to measure the velocity of the wake flow field at a diameter-based Reynolds number of $Re=7\times 10^{4}$ . The results revealed that the interaction of the rolling up separated shear layers, under the influence of high-momentum fluid travelling from the free stream to the wake, induced significant vertical flow movement in the vortex-formation region. This movement led to strong alternating surface pressure fluctuations at the cylinder's shoulders, contributing to the scattering of noise. It was demonstrated that local blowing delayed vortex shedding for all cases, except at $\theta _{b}={\pm }90^{\circ }$ , which elongated the shear layers and pushed the high-momentum transfer area farther downstream. The application of local blowing at $\theta _{b}={\pm }41^{\circ }$ was particularly effective in increasing the vortex formation size due to reduced entrainment of fluid-bearing vorticity.

Compressed air energy storage system: Effect of variable relative stator installation angle on nozzle governing turbine performance

The air storage pressure of compressed air energy storage system gradually decreases during the process of energy release, and a reasonable air distribution method for the turbine is required to make the turbine work efficiently in this process. In this paper, based on the single nozzle governing method, the effect of the variation of the full circumferential relative stator installation angle on the system performance improvement under the rated output work condition is investigated. It is shown that the specific work of the variable relative stator installation angle can be improved by up to 6.3 % relative to the design stator installation angle and up to 15.7 % relative to the throttle governing method under the base pressure of 10.0 MPa. With the same absence of throttling losses, the specific work of 3-nozzle inlets method is higher than that of 4-nozzle inlets method, and the turbine internal losses are reduced by 10.6 %. This study provides a theoretical basis for the design, optimization and operation control of nozzle governing turbines.

Effect of dynamic contact angle behavior on droplet topological structure and film thickness evolutions in droplet mode

The droplet mode falling film evaporation was an area of intense research due to its thin liquid film and large interfacial area. A two-dimensional mathematical model based on the dynamic contact angle (DCA) model was developed to quantitatively analyze the effect of DCA behavior on droplet topological structure and film thickness evolutions of droplet mode in falling-film evaporation. Due to the movement of the three-phase contact line (vc) considered in the DCA model, the fact that the calculated DCA was significantly greater than the static contact angle (SCA) resulted in the phenomena of the liquid ring and droplet pulsation captured by the DCA model. The observed fluctuations of the DCA and vc might be attributed to the break-up of the liquid neck. For the impact stage, the peaks of the transient film thickness calculated by the DCA model were thicker than those by the SCA model and their differences increased with the increasing circumferential angle. For the metastable stage, the average film thickness predicted by the DCA model was thicker than that by the SCA model due to the captured droplet pulsation and calculated shorter metastable state by the DCA model.

Wake suppression of a cylinder immersed in turbulence using rotating rods

In this study, we conducted three-dimensional direct numerical simulations to investigate the control performance of the free-stream turbulence past a circular cylinder with two small rotating rods at Re = 3900. In the case A and case B, two control rods with different rotating ratio α are positioned symmetrically at the circumferential angle θ=±45° and θ=±120° from the forward stagnation point of the main cylinder, respectively. Here, α is the ratio of the tangential velocity of the control rod surface ur to the inflow velocity U∞. Compared to the bare cylinder immersed in turbulence, both installation positions of the rotating rods at α = 2 result in a significant suppression on the wake flow. Specifically, the time-averaged drag coefficient Cd¯ was reduced by 25%, and the root mean square value of the lift coefficient measured to reduce by up to 30%. Statistical analysis is then performed, in terms of the Reynolds stresses, mean field, and the turbulent wake visualization to show variations in the flow dynamics. As expected, the front-mounted control rods inject kinetic energy into the boundary layer, effectively suppressing the turbulence fluctuations on both sides of the main cylinder. The work done by viscous forces around the rotating control rods and the suppression of turbulent fluctuations contribute to the pressure recovery observed in the rear-mounted control rod case. Proper orthogonal decomposition method is further employed to analyze the key features of the controlled wake of two cases with α = 2.

Performance analysis of tilting pad thrust bearing incorporating the surface roughness, texture and turbulence effect

In order to improve the lubrication performance of the friction pair, the effect of composite micro-texture on the lubrication performance of the tilting pad thrust bearing is studied. Based on the structural model of tilting pad thrust bearing considering composite micro-texture, the lubrication characteristics of thrust bearing with composite micro-texture parameters and tilting pad parameters are analyzed. At the same time, the theoretical model of tilting pad composite micro-texture bearing considering roughness and turbulence effect is established, and the performance of thrust bearing considering roughness and turbulence effect is studied. The results show that the performance of composite micro-textured bearings is better than that of single micro-textured bearings, the performance of tilting pad bearings is better than that of parallel pad bearings, and the performance of circular composite fish-shaped micro-textured tilting pad bearings is the best. The optimal bearing fulcrum position is near the inner diameter, and the optimal fulcrum circumferential inclination angle is about 27.5°. Considering the roughness and turbulence effect, the maximum pressure and bearing capacity of the bearing improves, and the friction coefficient significantly reduces.

Experimental Study of Piezoelectric Control for Changing Tilting Pad Journal Bearing Circumferential Angle and Radial Displacement

In order to improve the vibration performance of the oil-lubricated tilting pad bearing system, an experimental approach using a piezoelectric actuator to control two new flexible tilting pads is proposed. The performance test bench of the bearing–rotor system based on a tilting pad bearing with a flexible support is established. The different circumferential angles of the angle bearing tilting pad and the radial displacement of the displacement bearing are tested by a piezoelectric actuator. At the same time, the trajectory of the rotor center under actual operating conditions is analyzed. The experimental results show that the amplitude of the rotor journal can be significantly reduced by controlling the control variables related to the circumferential angle and radial displacement of the bearing bush. Therefore, this control improvement can improve the vibration performance of two new flexible tilting pad bearing–rotor systems. The technical means are provided for the active control of an oil-lubricated tilting pad bearing.

Optimizing circumferential assembly angle of rotor parts connected by curvic couplings based on acquired tooth surface error data

Due to the excellent self-centering and load-carrying capability, curvic couplings have been widely used in advanced aero-engine rotors. However, curvic tooth surface errors lead to poor assembly precision. Traditional physical-master-gauge-based indirect tooth surface error measurement and circumferential assembly angle optimization methods have the disadvantages of high cost and weak generality. The unknown tooth surface fitting mechanism is a big barrier to assembly precision prediction and improvement. Therefore, this work puts forward a data-driven assembly simulation and optimization approach for aero-engine rotors connected by curvic couplings. The origin of curvic tooth surface error is deeply investigated. Using 5-axis sweep scan method, a large amount of high-precision curvic tooth surface data are acquired efficiently. Based on geometric models of parts, the fitting mechanism of curvic couplings is uncovered for assembly precision simulation and prediction. A circumferential assembly angle optimization model is developed to decrease axial and radial assembly runouts. Experimental results show that the assembly precision can be predicted accurately and improved dramatically. By uncovering the essential principle of the assembly precision formation and proposing circumferential assembly angle optimization model, this work is meaningful for assembly quality, efficiency and economy improvement of multistage aero-engine rotors connected by curvic couplings.