Trailing Edge Side Research Articles

Hybrid joint interface in composite fan blade subjected to bird strike loading

An aircraft engine’s fan blades are one of the most important parts of the engine. Bird strikes on fan blades have always been an issue, as bird parts can strike other parts of the engine, potentially causing more damage. It is impossible to avoid being struck by a bird entirely. However, finite element analysis can be used to optimize the design of blade so that the overall impact of a bird on a jet engine is reduced. Even though current composite blades can withstand the impact of a bird strike, some delamination failures have been observed on the blade’s trailing edge side, probably due to vibration bending modes. Instead of the single fiber composite blade that is currently in use, this research proposes using two fibers (Carbon and Glass). For this to be possible, two fiber joints must be designed properly at different locations on the blade. At crucial joint locations, the minimum inter-laminar strain level was used as the design criteria. Blade deformation is simulated using coupon and sub-element level finite element analysis (FEA) models with appropriate boundary conditions with in-built hybrid joints inside. The first stage of this project involved using the Ansys Parametric Design Language (APDL) and linear static analysis to create coupon models for combinations of joint positions. In the present work, dynamic bird strike analysis on sub-element level models was performed with various joint location combinations. The best joint configurations based on static and dynamic analysis results will be suggested for use in the composite blade to prevent delamination.

Design and Optimization of Hybrid Interface Joint in a Composite Fan Blade of Aircraft Engine

Fan blades are one of the most important components of an aircraft engine. Bird strikes on fan blades have always been a cause of worry and it can cause slices of birds hitting other parts of the engine which may lead to greater damages. Bird strikes cannot be completely avoided. However, reduction of the impact of a bird on jet engines can be achieved by suitable design and manufacturing, through the simulation analysis. Although current composite blades can withstand the bird strike impact, some delamination failures are still observed on the trailing edge side of the blade, possibly due to vibration bending modes This paper talks about using two fibers in composite blade instead of the current single fiber one. For this to be feasible, two fiber joints at various locations on the blade have to be properly designed. The design criteria used here is the lowest inter-laminar shear strain level at critical joint locations. Suitable size coupon models in FEA with hybrid joints inside are used to simulate the blade bending with appropriate boundary conditions. The coupon models were developed by using the ANSYS APDL and linear static analysis was performed for different repetitive layups and varying layer by layer joint locations. The coupon joint designs with minimum inter-laminar shear strains are shortlisted to be recommended for use in sub-element and blade models.

Influence of inclination angle of trailing edge side on film cooling characteristics in hole shaped based on round holes with different sizes

Influence of inclination angle of trailing edge side on film cooling characteristics in hole shaped based on round holes with different sizes

Unsteady vortex structures in the wake of nonaxisymmetric bumps using spiral MRV

The temporal characteristics of the wake structure behind a nonaxisymmetric bump are studied using spiral magnetic resonance velocimetry (MRV) to measure time-series of all three velocity components in y–z-planes for bump orientations of $$5^\circ$$ , $$10^\circ$$ , $$15^\circ$$ , and $$20^\circ$$ relative to the freestream flow. The mean wake structure was shown previously to be highly sensitive to bump orientation (Ching et al. Exp Fluids, 2018). The spiral MRV method is validated by comparison to the established MRV techniques in a flow with forced periodicity. Measured velocity fluctuations in the bump wake decrease significantly as the bump angle is increased. A quasi-periodic shedding cycle is reconstructed using spectral proper orthogonal decomposition. The reconstructed cycles of each velocity component are matched through a divergence minimization method to examine the structure of the shed vortices. The vortex shed from the trailing edge side of the bump weakens as the bump angle is increased, whereas the vortex shed from the leading edge side maintains its strength. The alternating vortices move across the centerline as they are advected downstream, explaining the common-down vortex pair observed in the far wake mean fields.

Influence of geometric parameters on the thermal hydraulic performance of an ellipsoidal protruded enhanced tube

ABSTRACTIn this paper, the numerical simulation model of an ellipsoidal protruded tube has been established considering thermal hydraulic performance. The flow field characteristics and heat transfer characteristics of an ellipsoidal protruded tube were investigated. Effects of protrusion configuration, depth, pitch, number, axis ratio, and angle on thermal hydraulic performance were discussed using the realizable k–ε model under the steady-state condition. These results show that protrusion volume has a major impact on thermal hydraulic performance. The protrusions make the zone of flows narrow down at the protrusion leading edge side and expand at the trailing edge side, which resulted in protrusions increased turbulence, flow mixing, flow separation, and boundary layer distribution, thus enhancing the heat transfer performance. The maximum of local Nusselt number is located at the protrusions leading edge, and the minimum of local pressure is located at central of the protrusion surface. The configuration has no significant effect on the thermal hydraulic performance. Furthermore, the optimal selection of parameters boosts the heat transfer by up to 130.9% and amplifies the pressure loss up to 103.2%.

Direct numerical simulations on the flow past an inclined circular disk

Abstract The three-dimensional flow past an inclined circular disk is investigated using direct numerical simulations. Various incidence angles of the disk with respect to the inflow are considered from 0 ° to 60 ° , where 0 ° refers to the condition in which the flow is perpendicular to the disk. The aspect ratio (diameter/thickness) of the disk is considered to be 50. The Reynolds number based on the inflow velocity and the diameter of the disk is up to 500. The drag and lift coefficients, pressure coefficients, and three-dimensional vortical structures are analyzed using time-dependent and time-averaged techniques. Detailed comparisons between the results of the disk at different incidence angles are presented. The flow pattern gradually changes from chaotic to a periodic state as the incidence angle increases from 0 ° to 60 ° . At incidence angles of 45 ° and 50 ° , an evident low-frequency modulation exists whose period is approximately ten times greater than the primary vortex shedding period. For the inclined disks, the wake flow is tilted to the trailing edge side of the disk rather than parallel to the streamwise direction. The distance between two successive vortical rings is observed to decrease as the incidence angle increases. The streamwise length of the mean recirculation bubble decreases as the incidence angle increases.

The flexibility effect of a plate according to various angles of attack in a free-stream

This paper presents a computational fluid–structure interaction analysis for a flexible plate in a free-stream to investigate the effects of flexibility and angle of attack on force generation. A Lattice Boltzmann Method with an immersed boundary technique using a direct forcing scheme model of the fluid is coupled to a finite element model with rectangular bending elements. We investigated the effects of various angles of attack of a flexible plate fixed at one of the end edges in a free-stream at a Reynolds number of 5000, which represents the wing flapping condition of insects and small birds in nature. The lift of the flexible plate is maintained at the large angle of attack, whereas the rigid plate shows the largest lift at angles of attack around 30–40° and then drastic reductions in the lift at the large angle of attack. If we consider the efficiency as the lift divided by the drag, the flexible plate shows better efficiency at angles of attack greater than 30° compared to the rigid plate. The better performance of the flexible plate at large angles of attack comes from the deformation of the plate, which produces an interaction between the trailing edge vortex and the short edge vortex. The horseshoe-shaped vortex produced by a large vortex interaction at the trailing edge side has an important role in increasing the lift, and the small projection area due to the deformation reduces the drag. Furthermore, we investigate the role of flexibility on the lift and the drag force of the rectangular plate in a free-stream as the Reynolds number increases. Whenever a large vortex interaction at the trailing edge side is shown, the efficiency of the rectangular plate is improved. Especially, the flexible plate shows better efficiency as the Reynolds number increases regardless of the angle of attack. • The lift force of a flexible plate is maintained at large angle of attack. • Horseshoe-shaped vortex at the trailing edge side is important in increasing the lift force. • The flexible plate shows better efficiency as Reynolds number increases. • Fluid-structure analysis combined with FEM and LBM is presented and validated.

Modelling of Effect of Non-Uniform Current Density on the Performance of Soluble Lead Redox Flow Batteries

Soluble lead acid redox flow battery (SLRFB) offers a number of advantages. These advantages can be harnessed after problems associated with buildup of active material on electrodes (residue) are resolved. A mathematical model is developed to understand residue formation in SLRFB. The model incorporates fluid flow, ion transport, electrode reactions, and non-uniform current distribution on electrode surfaces. A number of limiting cases are studied to conclude that ion transport and electrode reaction on anode simultaneously control battery performance. The model fits the reported cell voltage vs. time profiles very well. During the discharge cycle, the model predicts complete dissolution of deposited material from trailing edge side of the electrodes. With time, the active surface area of electrodes decreases rapidly. The corresponding increase in current density leads to precipitous decrease in cell potential before all the deposited material is dissolved. The successive charge-discharge cycles add to the residue. The model correctly captures the marginal effect of flow rate on cell voltage profiles, and identifies flow rate and flow direction as new variables for controlling residue buildup. Simulations carried out with alternating flow direction and a SLRFB with cylindrical electrodes show improved performance with respect to energy efficiency and residue buildup.

Effect of beam angle on HAZ, recast and oxide layer characteristics in laser drilling of TBC nickel superalloys

Industrial applications of laser drilling include the production of cooling holes at acute angles in certain parts of the aero-engine components. These parts are often covered with ceramic thermal barrier coatings (TBC) to protect them from reaching excessive temperatures in hot engine environments. Acute angle TBC drilling brings three major simultaneous complications to the process. These are: (i) multi-layer drilling, (ii) non-symmetrical geometry and melt ejection, and (iii) increased depth of drilling. In a previous investigation by the authors, delamination of TBC was found as a main problem of angled drilling and mechanisms involved were studied. In the present study, implications of these difficulties on the hole quality is investigated through a comparative study of vertical and acute angle drilled holes. Characteristics of recast layer, heat-affected zone (HAZ), oxide layer and TBC delamination are investigated. Variation of these metallurgical characteristics with the depth of the hole is evaluated. Results for vertical and inclined holes are compared. The extent of HAZ, recast layer and oxide layer is seen to vary significantly with location and is found increasing with decreasing drilling angle to surface. Numerical simulation of pulsed laser heating of TBC Nimonic 263 was carried out for acute angle drilling with assist gas considerations. Results from the simulation suggested that the total heat transfer rate is higher on the leading edge side than the trailing edge of the heated region. Experimentally observed larger HAZ on leading edge side and larger recast layer on trailing edge side are explained by the analysis of heat flow characteristics obtained with the model.

수직분사각도를 갖는 직사각 막냉각홀 내부에서의 유동 및 열/물질전달 특성

An experimental study has been conducted to investigate the flow and heat/mass transfer characteristics within a rectangular film cooling hole of normal injection angle for various blowing ratios and Reynolds numbers. The results are compared with those for the square hole. The experiments have been performed using a naphthalene sublimation method and the flow field has been analyzed by numerical calculation using a commercial code (FLUENT). The heat/mass transfer around the hole entrance region is enhanced considerably due to the reattachment of separated flow and the vortices generated within the hole. At the hole exit region, the heat/mass transfer increases because the main flow induces a secondary vortex. It is observed that the overall heat/mass transfer characteristics are similar to those for the square hole. However, the different heat/mass transfer patterns come out due to increased aspect ratio. Unlike the square hole, the heat/mass transfer on the trailing edge side of hole entrance region has two peak regions due to split flow reattachment, and heat/mass transfer on the hole exit region is less sensitive to the blowing ratios than the squarbr/

Flow and turbulence conditions in the wake of a H-section in cross flow

Abstract Both steady and unsteady wakes of a torsional aeroelastic wind energy converter are examined. The converter consists of a H-section prism with attached pendulums for adjusting the natural frequency of the system. To provide an understanding of the wake characteristics of the device, a particle image velocimetry system was used to measure the mean and fluctuating velocity fields from which various single-point statistics were calculated. For the steady case, wake profiles were obtained at angles of attack from −30° to +30° (at 5° intervals) with the H-section fixed at each angle. In the unsteady case, the H-section was free to vibrate due to flow–structure interaction and a torsional vibration was produced with angles of attack from −30° to +30°. Turbulent wake profiles obtained for the H-section at fixed angles of attack are compared with the oscillating cases and the differences between the various single-point turbulence velocity statistics are discussed. The presented results indicate that the overall dynamic wake deficit for the oscillating case is less than the static wake deficit. Furthermore, the dynamic wake deficit, which is about 20% of U∞ is dispersed across the entire section; whereas, the static wake is concentrated around the trailing edge side of the converter.

Effects of tip clearance on the noise generated from low pressure axial flow fans. Difference caused by the width and location of a ring set in the tip clearance and the blade tip profile.

The effect of the width and the location of a ring set in the clearance between a duct inner wall and a blade tip and the profile of a blade tip on fan noise are experimentally investigated by using three rings of different widths and four impellers with different tip geometry. The results are summarized as follows : A considerable amount of noise reduction can be expected by setting a ring within a tip clearance, when its initial gap is rather large. Both the noise and the aerodynamic characteristics at the maximum efficiency point are better in the case with a larger gap on the leading edge side than on the trailing edge side. In the lower flow rate range, however, the fan with a smaller tip clearance on the leading edge side is superior.