Slot Parameters Research Articles

Airport time profile construction driven by flight delay prediction

Slot structure is the equilibrium result of market demand side and slot resource supply side, while slot parameters reflect the operational support capacity of the aviation system. Time parameters reflect the operational support capability of the aviation system. Time structure should not only reflect changes in market demand, but also meet the constraints of operational efficiency. Constructing a reasonable 18–24 h timetable profile for busy airports that meets normal expectations for declared capacity and seasonal scheduling is a challenge in civil aviation slot management. This study utilizes historical data on airport flights and weather conditions to establish a regression prediction model for the time structure using K-means clustering and partial least squares regression. Additionally, ensemble learning is employed to forecast flight delay levels. The findings demonstrate that random forest yields favorable results in regression and prediction tasks, allowing for the integration of upper (good weather) and lower (severse weather) limits of the time profile with delay predictions as time parameter intervals. Consequently, the flights falling within these intervals achieve an average delay level of less than 15 min which meets the expectations of normal flight.

Investigation of slot parameters on the performance of Savonius hydrokinetic turbine: a CFD study

Investigation of slot parameters on the performance of Savonius hydrokinetic turbine: a CFD study

Devising a procedure for integrated modeling of riverbed shape in the area of bridge crossing in order to avoid dangerous washing erosion

The object of research is a riverbed in the area of a bridge crossing, which is subject to the action of high water during the passage of a flood. The selection of parameters and contours of the scheme of the river section was carried out using a mathematical model of the flow and deformation of the bed of the riverbed before and after the change of its shape. It was established that the assignment of parameters of the operational slot should be performed on the basis of the principle of creating natural analogs of riverbed shapes, riverbed and floodplain terraces, with the use of mathematical modeling. To reduce erosion in the area of bridge crossings, it is proposed to regulate the riverbed by constructing a canalized riverbed. Modeling according to this option showed that the erosion in the span of a road bridge decreased and did not exceed 1.5 m. In addition, it was established that a significant role in ensuring the stability of the river is played by the vegetation cover in floodplain areas. Using the method of mathematical modeling, it was established that the area near the convex bank with a width of 150 m is subject to the strongest erosion in the design of the supports. Siltation of the existing left-bank bottom basin is also observed. It is recommended to make a decision to carry out restorative cutting of riverbed alignment annually after receiving a flood forecast from the local hydrometeorological station. In the case of a high flood warning, work should be carried out to clear the sleeves on the approach to the construction of the bridge deck. It was established that the most stable shape of riverbeds is in the form of curvilinear incomplete meandering when the radii of curvature R and the width of the riverbed B satisfy the ratio R=(4...7) B at riverbed-forming flow rate. At the same time, radii of curvature R<3.5 B should not be allowed, as this leads to separation of the flow from the convex bank and excessive erosion of the concave bank

A MATLAB simulation-based analytical study of energy, exergy, and cost benefits in jet-impinged protrusion-roughened double pass solar air collector.

This study analyzes the performance and cost-effectiveness of a protrusion-roughened jet-impinged double-pass solar air collector (PRJDPSAC) within a Reynolds number (Re) range of 2500 to 22,500. Examining jet slot parameters, i.e., the jet height ratio (Hjp/Dhd = 0.11-0.44), stream-wise pitch ratio (Xjp/Dhd = 0.44-1.32), and span-wise pitch ratio (Yjp/Dhd = 0.44-1.32), the model demonstrates enhanced energy conversion, minimizes losses, improves efficiency, and brings positive economic impact, making it a promising solution for diverse applications including drying processes, livestock facilities, remote accommodations, and HVAC system pre-heating. The examination incorporates advanced MATLAB simulations to assess energy-exergy performance and cost viability. At lower Re values, both energy ([Formula: see text]) and exergy ([Formula: see text]) efficiencies increase uniformly; however, stabilization and decline occur at higher Re values. The maximum [Formula: see text] for the PRJDPSAC is 4.38% under a temperature rise parameter of 60 × 10-3 Km2/W for obtaining optimum values of Xjp/Dhd = 1.32, Hjp/Dhd = 0.22, and Yjp/Dhd = 1.32, which is 31% higher than that of the smooth double-pass solar air collector (DPSAC). Economic benefits are significant for PRJDPSAC within mair (0.01-0.07kg/s), but above 0.07kg/s, the DPSAC becomes more cost-effective. Integrating simulation and experimental data, the study highlights MATLAB's effectiveness for solar energy system analysis and optimization, reinforcing the practicality of the proposed collector design.

3D Slot Roughness of Contemporary Ceramic Brackets

Purpose of Study: To examine the roughness of slots of three ceramic brackets. Materials and Methods: Three ceramic bracket types (Encore, Reflections and Inspire ICE). The bottom of each slot of every bracket was selected for evaluation and pictures were taken by optical microscopy at magnification (20x) for a general estimation of the roughness. Then the roughness parameters (Sa, Sq, St, Sz) of every slot were examined in a 3D optical profilometer in a higher magnification. Results: The picture from Optical microscope gave a differences of textural morphology of brackets slots for tested brackets. Metallic slots gave differences of grooves and striations whereas plastic slots presented peaks and pits. Inspire ICE showed the highest Sa and Sq value, statistically higher than the other brackets tested. Reflections gave the highest Sz and St values, which were statistically significant higher than the other brackets, followed by Inspire ICE which presented statistically significant higher values compared to Encore. Conclusions: The significant differences were revealed through 3D-images and roughness parameters of slots gives significantly different among the tested bracket. Encore and exhibited low roughness parameters.

A comparative study of purge slot exit shape on the film cooling effectiveness of a gas turbine shroud

To achieve higher efficiency and performance, a modern gas turbine withstands the extremely high thermal environment. In the turbine endwall passage, a high and non-uniform heat transfer appears due to various secondary flow. The purge flow injected through the upstream slot between the stationary and rotating pars can thermally protect the endwall surface by forming air film layer on it. However, since an excessive amount of purge flow reduce the system efficiency, it is needed to effectively inject the purge flow with a limited amount. Accordingly, in the present study, the effect of purge slot exit shape on the film cooling effectiveness (hereby FCE) of a shroud surface was discussed. As nondimensional design parameters of the purge slot, L/Ws, RW/Ws, and RL/Ws were defined, representing the geometric features: the slot width (Ws), the fillet radius at the windward side (RW) and fillet radius at the leeward side (RL) of slot exit, respectively. The measurement of the FCE was performed in a five-blade linear cascade rig using the PSP (Pressure sensitive paint) technique. The results showed that the FCE increased for wider slot width at a given blowing ratio condition. In addition, the fillet radius at the windward side (RW) has a negative effect on the FCE regardless of blowing ratio condition since the purge flow was easily disturbed by the accelerated mainstream injection. On the other hand, the Case 7 with the RW/Ws = 0.9 showed 5.1 % of the improvement of FCE at a higher blowing ratio M = 0.25 compared with the Case 2 with RW/Ws = 0, which represents the sharp edge at the windward side of the slot exit.

Wideband millimeter-wave hybrid dielectric resonator antenna array with dual-slot feeding

ABSTRACTA hybrid dielectric resonator antenna (DRA) array is proposed for the wideband millimeter-wave communication. The radiator is composed with a pair of stacked dielectric resonators (DRs), which are H-shaped and Hexagon-shaped DRs, respectively. The dual-slots on the substrate integrated waveguide (SIW) cavity are utilized for higher mode generation in the DRA element. The antenna bandwidth is improved by the stacked DRs and dual-slot feeding. The structural characteristics and key parameters of feeding slots are discussed in detail. The DRA array fed with parallel power distribution feeding network is fabricated and measured to verify the reliability of the simulations, and the simulations and measurements have reasonable consistency. The impedance bandwidth is from 23.55 GHz to 27.28 GHz (14.7%), and the measured gain ranges from 13.1 dBi to 15.7 dBi. The radiation patterns are stable in the operation band. The proposed DRA array has a promising application prospect for 5 G communication system.

Large Eddy simulation in optimizing trench configuration to improve cooling effectiveness of a laidback fan-shaped hole

In modern gas turbines, a thermal barrier coating (TBC) is used to protect the components of the turbine from the hot flow coming from the combustor, which results in the cooling holes on the blade surfaces being embedded in a 2D trench slot. In this study, large eddy simulations (LES) were carried out to investigate the effects of trench geometry on the film-cooling effectiveness of a shaped cooling hole. The shaped cooling hole is located on a flat surface with an injection angle of 30 degrees, and the blowing and density ratios are fixed at 1.5. Thirteen different designed cases were sampled using Box-Behnken method based on three different geometry parameters of the trench slot, trench height and upstream and downstream trench lengths. A genetic aggregation algorithm was applied to achieve the optimal trench configuration that maximizes the overall cooling effectiveness. The film-cooling performance computed by the LES method was validated for a reference case without a trench and three different trenched cases with the experiments using the PSP (pressure sensitive paint) technique. The cooling effectiveness of the trench cavity and flat plate was found to be significantly enhanced in cases of trenches with relatively greater trench height and less downstream trench length. The optimal trench configuration demonstrated less turbulent fluctuations in the mixing region, and the overall area-averaged adiabatic film-cooling effectiveness was improved by 23% in comparison with a reference hole without a trench.

Simulation Analysis of the Effect of Slit/Slot Pintle Geometry on Atomization of Bipropellant Engine

In order to optimize the slit/slot geometry design of a bipropellant pintle injector, the impinging spray development of a pintle injector was numerically investigated. The VOF (volume of fluid) and LES (large eddy simulation) methods were employed for an analysis to capture the gas–liquid interface by means of the AMR (adaptive mesh refinement) method. In those simulation cases, different flowrates, slot numbers, pintle diameters, slot thicknesses and slot shapes were compared for an analysis. In a comparison of visualization and quantification, a high flowrate and large pintle diameter were shown to be more positive features for improving the atomization quality and mixing effect. As for the slot parameters and shape, the spray development was mainly determined by the flow proportion between the slit jet and slot jet. The simulation results indicated that dominant slot jets cause a more dispersed spatial distribution, which is more conducive to the subsequent improvement of combustion efficiency in a limited space. However, an excessive increase in the number of slot jets can weaken the overall atomization quality and mixing effect, so it is suggested to ensure a balance for geometry design optimization.

A spiral slotted transducer with high longitudinal-torsional conversion rate

The longitudinal-torsional (L-T) composite piezoelectric transducer has wide applications in material processing, welding, and other fields due to its exceptional machining efficiency. This study introduces a spiral slotted L-T transducer, which is designed to achieve a high L-T conversion rate at low operating frequency. The equivalent spring concept is employed to derive the equivalent circuit of the L-T transducer, which provides a convenient study for the frequency characteristics of the transducer. A finite element model is developed to analyze the performance of the transducer and investigate the effect of the spiral slot parameters on the resonance frequency, amplitude, and the L-T conversion rate of it. Two prototype transducers are constructed and measured experimentally. Theoretical computation results, finite element simulation results, and experimental results are compared to each other. The comparison results demonstrate that the proposed computation model provides accurate prediction of the L-T coupling resonance frequency of the transducer. By adjusting the spiral slot parameters of the transducer, a higher L-T conversion rate can be achieved, which may have more applications in practical engineering.

IDDES Investigation of Rotor Blade Tip Vortices in Hovering State with Tip Slots

The slots on a blade tip can effectively suppress the tip vortices by diffusing the core structure of a vortex and thus mitigate the adverse impacts of vortex interactions. In this paper, the effect of a slotted tip on vortex diffusion in the hovering state is investigated numerically by implementing the IDDES method using the fifth-order WENO scheme. The resulting wake flow field show that the number of secondary turbulent structures of so-called vortex worms near the slotted tip reduces significantly, indicating the weakening of vortex core rotation. It was found that the slotted tip reduced the peak value of velocity profiles in the vicinity of the vortex core by about 50%. The numerical result is close to the experimental conclusion. Correspondingly, the diameter of the vortex core is approximately doubled at each wake age relative to the baseline blade because the local flow passing through the slots will disintegrate the stable structure of the core region during the early stages of tip vortex generation. This promotes the turbulence mixture, resulting in the reduction in the vorticity value and rotating effect near the vortex core. Based on the overall results, the study of the slot parameters demonstrated that reducing the slot number or diameter will weaken the diffusing effect, causing a decrease in the flow rate.

Research on Lubrication Characteristics of Cage-Free Ball Bearing with Local Functional Slot

The factors affecting the lubrication effect of a ball bearing without cage and containing a functional slot are analyzed, including the structural parameters of the functional slot, the speed of the rolling element, and the deformation of the contact surface, in order to establish the initial oil volume equation. Based on the multiple mesh method and Matlab programming, the established model is solved by obtaining the distribution rules of oil film pressure, oil film thickness, and oil film flow rate between the rolling element, the conventional raceway, and the functional slot under different speed conditions, and by determining the optimal functional slot depth. Finally, through an experiment performed to verify the lubrication effect of the lubricating oil in the functional slot, the results show that the lubricating oil in the functional slot can have a lubricating effect, and the initial amount of lubricating oil needed increases with an increase in speed.

Corner separation control in compressor stators with jets from the blade leading edge

Corner separation occurs easily in highly loaded compressor stators. This paper proposes a novel slot inside the stator blade, with the slot inlet located at the blade leading edge and the slot outlet located at the suction surface, by using the momentum of the incoming flow to form a high velocity jet to control the development of the boundary layer on the blade suction surface. For 3D compressor cascades, the influence of the key geometrical slot parameters on the flow fields in the slot and cascade passage and the aerodynamic performance of the cascade were investigated with a numerical method. Then, the stator blades in a highly loaded compressor stage were slotted to improve the flow in the stator blade passages. The main results can be summarized as follows. The use of slotted blades in the cascade effectively suppresses corner separation. When the cascade inlet velocity is high or the inlet flow is at a positive attack angle, the separation control effect improves. In the highly loaded compressor stage, slotted stator blades considerably reduced the flow loss at the stator corner, and the stage efficiency increased over the entire flow rate range. Furthermore, two cascades with unslotted and slotted blades were tested. The experimental and numerical results were consistent, demonstrating that the total pressure loss coefficient of a cascade can be effectively reduced by slotting the blades in the cascade.

Experimental investigation and optimization of dimple-roughened impinging jet solar air collector using a novel AHP-MABAC approach.

The effect of the flow and geometric parameters of a dimple-roughened absorber plate on the enactment of solar air collectors (SACs) with air-impinged jets was investigated in this study. The performance-defining criteria (PDCs) of a jet-impinged dimple-roughened SAC (JIDRSAC)-forced convection airflow system are significantly affected by variations in the system's control factors (CFs), such as the arc angle (αaa) ranging from 30° to 75°, dimple pitch ratio (pd/Dh) ranging from 0.269 to 1.08, and dimple height ratio (ed/Dh) ranging from 0.016 to 0.0324. The constant parameters of the jet slot are a stream-wise pitch ratio (Xi/Dhd) is 1.079, a span-wise pitch ratio (Yi/Dhd) is 1.619, and a jet diameter(Di/Dhd) is 0.081. Based on the combined approach of the analytic hierarchy process and multi-attributive border approximation area comparison (AHP-MABAC), the Reynolds number (Re) = 15,000, αaa = 60°, pd/Dh = 0.27, and ed/Dh = 0.027 depicted the best alternative (A-9) set among 16 alternatives to deliver the optimal performance of the JIDRSAC. The jet impingement pass compared to the smooth pass, the Nusselt number increased by 2.16-2.81, and friction factor increased by 3.35-5.95, and JIDRSAC was compared to the jet impingement pass, exhibiting an enhancement in Nusselt number and friction factor in the range of 0.55-0.80 and 0.05-0.15, respectively. In addition, sensitivity analysis is used to examine the ranking's stability and reliability in relation to the PDC weights.

Optimization of Stator Slot Parameters for Electromagnetic Vibration Reduction of Permanent Magnet Synchronous Motors

Slight electromagnetic vibration is one of the crucial indicators that must be considered in the motor design stage. Considering the influence of complex stator slot structure and inevitable saturation at slot opening, a permeance calculation model suitable for the motor with any pole-slot combination is introduced, and the electromagnetic force waves of the motor are calculated quickly and accurately. Considering the orthogonality of stator material and the influence of enclosure and windings, the natural frequencies of the entire stator are analyzed, and the vibration accelerations are calculated by the multiphysics model including control, electromagnetic, structural, and vibration models, the accuracy of the calculation results is verified by the prototype test. Furthermore, the components of electromagnetic force waves that have great impact on electromagnetic vibration are summarized, a weakening method of electromagnetic vibration based on the optimization of the stator slot parameters is proposed, and the optimal stator slot parameters are obtained by the simplified model and the accurate model combining deep neural network (DNN) and immune clone algorithm (ICA), respectively. For the 6-pole 36-slot motor, the vibration accelerations near the six-order natural frequency are greatly reduced by optimizing the stator slot parameters based on the accurate model combining DNN and ICA, and the maximum vibration accelerations are reduced by 34.1% at no load and 36.8% at rated load.

Design, optimization and application of two-element airfoils for tactical UAV

Owning to the requirements for longer endurance, larger payloads as well as simpler mechanical structure of tactical UAV, the two-element airfoil technology is introduced. Firstly, the aerodynamic characteristics of five common low-speed airfoils are calculated and compared. The airfoil with good aerodynamic performance after segmentation is selected as initial airfoil. Then, the influence of different segmentation types on the aerodynamic characteristics of airfoils is analyzed, and the segmentation type which brings the best aerodynamic benefits is selected. The slot parameters are optimized by NSGA-II optimization algorithm under cruising, take-off, and a large angle of attack states to obtain a high-performance self-adaption tactical UAV airfoil. Finally, the new airfoil is applied to Sparrow-hawk tactical UAV, the CL1.5 /CD of acceleration state increases 15.5%, the CL of large angle of attack increases 20.4% and the CL1.5 /CD of cruising state after enlarge the aspect ratio increase12.3%.

Modeling and optimization of longitudinal-torsional vibration horn with the large tool head

There are problems such as large deviations in resonant frequency and difficulties in selecting the structural parameters of helical slot when designing longitudinal-torsional vibration horn with large tool head (HWLTD) using traditional design theory of horn. Therefore, in this paper, HWLTD was designed integrally, the model of HWLTD was established, longitudinal vibration frequency equation of HWLTD was derived and consequently, the resonant frequency was predicted and optimized. Then, the principle of vibration mode transformation (POVMT) of helical slots was derived. Combined with POVMT and ANSYS simulation analysis, resonant frequency and torsional-longitudinal ratio of longitudinal-torsional vibration of HWLTD were optimized, thereby improving the vibration characteristics of HWLTD. The resonant frequency and vibration effect of HWLTD were tested, and the measurements were agreed with the theoretical design and simulation analysis, which validates the HWLTD model and POVMT. The research provides a reference for the efficient and reliable design of HWLTD in the field of ultrasonic machining.

Analysis of Impact of a Novel Combined Casing Treatment on Flow Characteristics and Performance of a Transonic Compressor

To reduce the negative impacts of stall and surge on compressor performance, a novel combined casing treatment (CCT) structure with axial skewed slots and injection groove is proposed in this paper. The aerodynamic performance, as well as the mechanisms of loss generation, of a transonic axial compressor with NASA Rotor 67 are investigated numerically. The simulation results indicate that, compared with individual casing treatment method, the CCT works effectively with regard to operation performance. The stall margin (SM) is increased by 14.7% with 1.12% decrease in the peak efficiency. The interaction of axial skewed slots and injection groove can be explained by the enhancement of exchange flow in slots and axial motion of fluid. As a result, the leakage flow near the blade tip is eliminated and the flow separation is further suppressed. What is more, an analysis of entropy generation is also conducted. The results reveal that the effect of CCT on loss reduction mainly concentrates in the tip part of the blade, with the loss decrease about 14.46% compared with the original rotor. The best control effect can be expected by appropriate match between geometrical parameters of axial skewed slots and mass flow rate of injection from the parameter analysis.

Design of Ka band substrate integrated waveguide slot traveling wave array antenna

Aiming at the requirements of Missile Radio Fuze Antenna with low sidelobe, narrow beam and specific directional pattern, a design method of Ka band substrate integrated waveguide (SIW) slot traveling wave array antenna is proposed. Based on the slot theory of SIW, the slot parameters and the excitation amplitude of Taylor linear array elements are calculated by MATLAB, and then the slot parameters and the excitation amplitude of array elements are optimized by Ansoft HFSS electromagnetic simulation software to realize the design of Ka band SIW slot traveling wave array antenna. The simulation results show that the Ka band SIW slot quasi traveling wave array antenna has a working frequency of 34.5 GHz, a gain of 14.2 dB, an E-plane beam width of 8° and a beam inclination of 20°, which can meet the requirements of missile radio fuze.

High-Extinction-Ratio and Compact 1310/1550 nm Wavelength Diplexer on SOI Platform Based on an SWG-Structured Two-Mode Interference Coupler

We propose a 1310/1550 nm wavelength diplexer on a 220-nm silicon-on-insulator (SOI) platform. The device is based on a compact two-mode interference (TMI) coupler enabled by a subwavelength grating (SWG) slot. The ideal beat length ratio of 2:1 is achieved with the transverse magnetic (TM) mode by fine-tuning the SWG slot parameters, resulting in a TMI length of only 37 µm. We reveal that the key to high extinction ratio (ER) is the careful design of the tapers, and the device achieves high ERs of 28.05/42.54 dB at 1310/1550 nm with simulation. The measured bandwidths for ER <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula> 15 dB are 82 nm and 56 nm at O- and C-band. Moreover, the design guarantees large calculated 1-dB-insertion-loss (IL) bandwidths of 192/123 nm at 1310/1550 nm. To the best of our knowledge, this is the first experimental demonstration of a high-performance compact silicon 1310/1550 nm diplexer based on a TMI coupler.