Speed Regime Research Articles

Effects of Rollers Speed Regime on the Roller Screen Efficiency

ABSTRACT Roller screen is a key device in pelletizing plants employed to size classification of green pellets. Realistic observations showed that some pellets with size slightly larger than the gap were trapped between the rollers and caused blockage and decreasing the device efficiency consequently. Here, a speed regime for the rollers is proposed and its effects on the device efficiency were studied numerically. To perform the simulations, discrete element method was used and to ensure the results accuracy, surface meshing and the time step sensitivity analysis were performed. Using the numerical results, impact of each of the variables independently and also their cross effects were studied and discussed. The results proved that the proposed gradient speed regime improves the efficiency considerably. However, both the speed regime and the deck angle should be adjusted in optimum values to achieve maximum efficiency.

Effect of sintering regimes and thickness on optical properties of zirconia ceramics for dental applications

AbstractIn dentistry, monolithic zirconia restorations have been preferred over all‐ceramic restorations in recent years. Translucency is an aesthetic demand in dental restorations, and it can be identified with translucency parameter (TP). Zirconia thickness, Y2O3 content, and sintering conditions are important parameters that influence the translucency of the restorations. It is crucial to investigate monolithic zirconia ceramics under different sintering regimes and reveal the critical parameters for dental restorations. The aim of this study was to determine the optical and microstructural behaviors of monolithic zirconia ceramics containing different amounts of yttria depending on various sintering regimes and thicknesses. Therefore, a conventional zirconia CopranZri (CZI) and two monolithic zirconia materials, CopraSupreme (CSP), CopraSmile (CSM) were used. Slow, normal, speed, and translucency sintering regimes with thicknesses of 0.7, 1.0, 1.3 mm were selected. TP of the specimens was calculated, and statistical analyses were performed by using one‐way ANOVA and Tukey‐Kramer post hoc tests. Characterization of the specimens was performed by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X‐ray (EDX) techniques. The results showed that the effect of different sintering programs is more critical for CSP and CSM in terms of translucency variations and translucency program led to the most grain growth.

Development of a floating liner test rig and lubrication model for the study of the piston compression ring friction force under fully flooded and starved lubrication

Advances in internal combustion engines make it necessary to study in depth their contribution to engine efficiency, and thus to friction mechanical losses, especially those generated in the piston-cylinder liner assembly. In this paper, the design of a novel test rig is presented, based on the floating liner principle, with the key objective of having the capability of developing multiple parameters tests in a relatively quick and easy way. The final design integrates a single-cylinder internal combustion engine, a mechanical solution that allows the liner to float, three piezoelectric force sensors and a novel design of lateral support based on ball transfer units. Reproducibility and repeatability of tests were assessed demonstrating the capability of the test rig to develop reliable friction measurements. Some parameters tests were developed to evaluate the sensitivity of the friction force measurements to variations in the working conditions, oil temperature and engine speed. A theoretical model for the piston compression ring is presented for both fully flooded and starved lubrication conditions, including asperity interactions and lubricant rheology. Comparisons of these approaches with experimental results showed that, for the working conditions of the test rig, lubrication of the compression ring is better estimated under fully flooded lubrication condition, as the starved lubrication analysis results in over-estimated friction force values at higher engine speed regimes.

An implicit kinetic inviscid flux for predicting continuum flows in all speed regimes

In this study, the kinetic inviscid flux (KIF) is improved and coupled with an implicit strategy. The KIF is a recently proposed numerical method, which is a dynamic combination of the kinetic flux vector splitting (KFVS) method and the totally thermalized transport (TTT) method. The inherent microscopic mechanism of the KFVS makes the KIF good at solving shock waves and avoiding the numerical shock instability phenomenon. When developing the implicit KIF, it is noticed that, in boundary layers, the KFVS part of the KIF not only reduces the accuracy but also seriously reduces the Courant–Friedrichs–Lewy (CFL) number. As a result, a new weight is proposed in this paper to combine the KFVS method with the TTT method properly. Besides admitting the use of larger CFL numbers, this new weight also contributes to more accurate numerical results like pressure, friction coefficient, and heat flux when solving shock waves, boundary layers, and complex supersonic/hypersonic flows. To examine the validity, accuracy, and efficiency of the proposed method, six numerical test cases covering the whole speed regime are conducted, including the hypersonic viscous flow past a cylinder, the hypersonic double-cone flow, the hypersonic double-ellipsoid flow, the laminar shock-boundary layer interaction, the supersonic flow around a ramp segment and the subsonic lid-driven cavity flow.

Tropical Cyclone Wind Speed Estimation From Satellite Altimeter‐Derived Ocean Parameters

AbstractThis study investigates the satellite altimeter‐derived ocean parameters from Joint Altimetry Satellite Oceanography Network (Jason)‐2 and Jason‐3 response to the coincident wind speed at 10 m from sea surface (U10) from Meteorological Operational (MetOp)‐A and MetOp‐B satellite scatterometers inside the tropical cyclone environment. The high wind speed regime and rainy condition inside the tropical cyclone have reduced the U10 accuracy and thus, would benefit from more ocean related parameters to be considered. The altimeter Ku‐band backscatter and significant wave height are commonly used to estimate extreme U10 but still show significant error in rainy tropical cyclone. New U10 models incorporating several Jasons derived ocean parameters (including brightness temperatures and water content) were designed by the multiple linear regression and artificial neural network techniques. Parameter analysis indicated that the C‐band backscatter outperforms the Ku‐band counterpart in relation to U10 inside the tropical cyclone. The proposed models show U10 estimation up to 35 ms−1 with 1 ms−1 accuracy and major improvement inside the tropical cyclone rain and at the high wind speed regime. This too shows the ability of satellite altimeter in estimating U10 in extreme environment with great accuracy.

INVESTIGATION OF THE SPEED OF MOVEMENT OF POWDER PARTICLES OF COLD GAS DYNAMIC SPRAYING

The article shows the results of the study of the velocity of the sprayed powder particles on the example of cold gas-dynamic spraying of copper powder C01-11. Features and advantages of gas-dynamic spraying before other gas-thermal coating methods are given. The importance of the speed regime of coating and its influence on the formation of the coating is analyzed. A computational experimental method for determining the velocity of sprayed particles is proposed, as well as an experimental setup with the help of which it is possible to obtain objective data on the velocity regime of cold gas-dynamic coating. The design of the applied gas-dynamic spraying device is shown, which contains an electric heater of the compressed air flow and an accelerator of the heated compressed air into which the sprayed metal powder is driven due to the ejection effect. An experimental setup was used for the study, which contained two rotating disks mounted at a distance of 20 mm from each other on the shaft of a high-speed electric motor, with holes in the upper disk through which spraying occurs on the surface of the lower disk. Due to the fact that the disks with the spraying process rotate at a speed of 10587 rpm is the displacement of the sputtering figure on the lower disk relative to the projection of the hole of the upper disk on the lower disk. The magnitude of this displacement is calculated by the velocity of the particles of the sprayed powder, according to the above method. The parameters that are taken into account when calculating the speed of the spray particles of the powder is the diameter of the nozzle of the spray device 5 mm. The distance from the nozzle cut to the upper disk is 10 mm. The distance from the nozzle cut to the lower disk is 32 mm. The distance between the disks a = 22 mm. The radius on which the nozzle of the spray device is installed is 90 mm. As a result of the experiments, it was found that when spraying copper powder C01-11 at a temperature of 20 ºC, the spraying speed is 232.2 m / s, which does not provide conditions for coating, and at elevated temperatures to 285 ºC quality coating was formed. The spraying speed was from 302.7 to 359.2 m / s for critical sections of 2.5 and 3.01 mm2, and the spraying area at higher speeds was approximately 20% higher than at lower speeds. This makes it possible for researchers to determine the velocity modes of spraying and, accordingly, to more accurately assign the optimal technological parameters to achieve the highest quality results of creating functional coatings.

Towards a Rationalization of Ultrafast Laser-Induced Crystallization in Lithium Niobium Borosilicate Glasses: The Key Role of the Scanning Speed

Femtosecond (fs)-laser direct writing is a powerful technique to enable a large variety of integrated photonic functions in glass materials. One possible way to achieve functionalization is through highly localized and controlled crystallization inside the glass volume, for example by precipitating nanocrystals with second-order susceptibility (frequency converters, optical modulators), and/or with larger refractive indices with respect to their glass matrices (graded index or diffractive lenses, waveguides, gratings). In this paper, this is achieved through fs-laser-induced crystallization of LiNbO3 nonlinear crystals inside two different glass matrices: a silicate (mol%: 33Li2O-33Nb2O5-34SiO2, labeled as LNS) and a borosilicate (mol%: 33Li2O-33Nb2O5-13SiO2-21B2O3, labeled as LNSB). More specifically, we investigate the effect of laser scanning speed on the crystallization kinetics, as it is a valuable parameter for glass laser processing. The impact of scanning energy and speed on the fabrication of oriented nanocrystals and nanogratings during fs-laser irradiation is studied.Fs-laser direct writing of crystallized lines in both LNS and LNSB glass is investigated using both optical and electron microscopy techniques. Among the main findings to highlight, we observed the possibility to maintain crystallization during scanning at speeds ~5 times higher in LNSB relative to LNS (up to ~600 µm/s in our experimental conditions). We found a speed regime where lines exhibited a large polarization-controlled retardance response (up to 200 nm in LNSB), which is attributed to the texturation of the crystal/glass phase separation with a low scattering level. These characteristics are regarded as assets for future elaboration methods and designs of photonic devices involving crystallization. Finally, by using temperature and irradiation time variations along the main laser parameters (pulse energy, pulse repetition rate, scanning speed), we propose an explanation on the origin of (1) crystallization limitation upon scanning speed, (2) laser track width variation with respect to scanning speed, and (3) narrowing of the nanogratings volume but not the heat-affected volume.

Performance Characteristics of A Micro Wind Turbine Integrated on A Noise Barrier

Micro wind turbines can be structurally integrated on top of the solid base of noise barriers near highways. A number of performance factors were assessed with holistic experiments in wind tunnel and in the field. The wind turbines underperformed when exposed in yawed flow conditions. The theoretical cosθ theories for yaw misalignment did not always predict power correctly. Inverter losses turned out to be crucial especially in standby mode. Combination of standby losses with yawed flow losses and low wind speed regime may even result in a net power consuming turbine. The micro wind turbine control system for maintaining optimal power production underperformed in the field when comparing tip speed ratios and performance coefficients with the values recorded in the wind tunnel. The turbine was idling between 20%–30% of time as it was assessed for sites with annual average wind speeds of three to five meters per second without any power production. Finally, the field test analysis showed that inadequate yaw response could potentially lead to 18% of the losses, the inverter related losses to 8%, and control related losses to 33%. The totalized loss led to a 48% efficiency drop when compared with the ideal power production measured before the inverter. Micro wind turbine’s performance has room for optimization for application in turbulent wind conditions on top of noise barriers.

A probabilistic-based analysis for wind distribution determination of a runway

PurposeThe purpose of this study is to describe precisely the wind speed regime and characteristics of a runway of an International Airport, the north-western part of Turkey.Design methodology approachThree different probability distributions, namely, Inverse Gaussian (IG), widely used two-parameter Weibull and Rayleigh distributions in the literature, are used to represent wind regime and characteristics of the runway. The parameters of each distribution are estimated by the pattern search (PS)-based heuristic algorithm. The results are compared with the other three methods-based numerical computation, including maximum-likelihood method, moment method (MoM) and power density method, respectively. To evaluate the fitting performance of the proposed method, several statistical goodness tests including the mostly used root mean square error (RMSE) and chi-squared (X2) are conducted.FindingsIn the light of the statistical goodness tests, the results of the IG-based PS attain better performance than the classical Weibull and Rayleigh functions. Both the RMSE and X2 values achieved by the IG-based PS method lower than that of Weibull and Rayleigh distributions. It exhibits a better fitting performance with 0.0074 for RMSE and 0.58 × 10−4 for X2 for probability density function (PDF) in 2012 and with RMSE of 0.0084 and X2 of 0.74 × 10−4 for PDF in 2013. As regard the cumulative density function of the measured wind data, the best results are found to be Weibull-based PS with RMSE of 0.0175 and X2 of 3.25 × 10−4 in 2012. However, Weibull-based MoM shows more excellent ability in 2013, with RMSE of 0.0166 and X2 of 2.94 × 10−4. Consequently, it is considered that the results of this study confirm that IG-based PS with the lowest error value can a good choice to model more accurately and characterize the wind speed profile of the airport.Practical implicationsThis paper presents a realistic point of view regarding the wind regime and characteristics of an airport. This study may cast the light on researchers, policymakers, policy analysts and airport designers intending to investigate the wind profile of a runway at the airport in the world and also provide a significant pathway on how to determine the wind distribution of the runway.Originality valueInstead of the well-known Weibull distribution for the representing of wind distribution in the literature, in this paper, IG distribution is used. Furthermore, the suitability of IG to represent the wind distribution is validated when compared with two-parameter Weibull and Rayleigh distributions. Besides, the performance and efficiency of PS have been evaluated by comparing it with other methods.

Metaheuristic data fitting methods to estimate Weibull parameters for wind speed data: a case study of Hasan Polatkan Airport

ABSTRACTFlight delays may be decreased in a predictable way if the Weibull wind speed parameters of a runway, which are an important aspect of safety during the take-off and landing phases of aircraft, can be determined. One aim of this work is to determine the wind profile of Hasan Polatkan Airport (HPA) as a case study. Numerical methods for Weibull parameter determination perform better when the average wind speed estimation is the main objective. In this paper, a novel objective function that minimises the root-mean-square error by employing the cumulative distribution function is proposed based on the genetic algorithm and particle swarm optimisation. The results are compared with well-known numerical methods, such as maximum-likelihood estimation, the empirical method, the graphical method and the equivalent energy method, as well as the available objective function. Various statistical tests in the literature are applied, such as R2, Root-Mean-Square Error (RMSE) and $\chi$2. In addition, the Mean Absolute Error (MAE) and total elapsed time calculated using the algorithms are compared. According to the results of the statistical tests, the proposed methods outperform others, achieving scores as high as 0.9789 and 0.9996 for the R2 test, as low as 0.0058 and 0.0057 for the RMSE test, 0.0036 and 0.0045 for the MAE test and 3.53 × 10−5 and 3.50 × 10−5 for the $\chi$2 test. In addition, the determination of the wind speed characteristics at HPA show that low wind speed characteristics and regimes throughout the year offer safer take-off and landing schedules for target aircraft. The principle aim of this paper is to help establish the correct orientation of new runways at HPA and maximise the capacity of the airport by minimising flight delays, which represent a significant impediment to air traffic flow.

Comprehensive Evaluation of Operating Speeds for High-Speed Railway: A Case Study of China High-Speed Railway

This paper proposes the indicator systems and integrated desirability framework for comprehensive evaluation towards the operating speeds of high-speed railway (HSR). Speed is a crucial piece in the characterization of the HSR system. The debate about what is the most appropriate operating speed continues. The established indicator systems and integrated desirability framework can comprehensively evaluate the HSR operating speeds from stand points of the economic efficiency, operational efficiency, track capacity, operational security, and environment impact. Moreover, the integrated desirability framework, which is a combination of entropy-analytical hierarchy procedure (EAHP) and technique for order preference by similarity to ideal solution (TOPSIS), can output some references for selecting the most suitable speed regimes of HSR. The application of the desirability framework to the case of China high-speed railway (CHSR) is demonstrated concretely. Based on the case study of CHSR, the comprehensive analysis of the effectiveness of the indicator systems on HSR operating speeds is carried out. The case study shows that the proposed indicator systems and integrated desirability framework can be used to evaluate comprehensively the HSR operating speeds under various conditions.

Effect of liquid elasticity on the behaviour of high-speed focused jets

We investigate the effect of highly contrasting non-Newtonian liquid properties on the formation of liquid jets with a focused shape. By using two nozzle-free ejection techniques, mechanically impact- and laser-induced, fast jets of a highly elastic (sodium polyacrylate) and weakly elastic (xanthan-gum) diluted polymer solutions are generated. A unique high-speed effect is encountered at the jet ejection onset of the highly elastic solution. Its jet-tip speed is on average 1.4 times faster in comparison to a Newtonian (glycerin/water) and the weakly elastic liquids. We explain this effect occurring as a result of the high viscoelasticity of the sodium polyacrylate solution. Additionally, a ‘bungee jumper’ jet behaviour (Morrison and Harlen in Rheol Acta 49(6):619–632, 2010) is observed in a regime of high speed (10<V_j<40 m/s) and high viscosity (mu >20 mPa s) not previously examined. We additionally characterise the viscoelastic non-breakup jet limit using the Bazilevskii et al. (Fluid Dyn 40(3):376–392, 2005) ejection criterion. Herein, the extensional rheological parameters are measured implementing a novel DoS-CaBER technique (Dinic et al. in Lab Chip 17(3):460–473, 2017). Our findings may influence results of inkjet printing technologies and recent nozzle-free ejection systems for ejecting liquids with non-Newtonian properties.Graphical abstract

Investigation of Reduction in Base Drag using Experiment and CFD at Subsonic Speed Regimes

Base drag, arising from flow separation at the blunt base of a body can be a sizeable fraction of total drag in the context of projectiles, missiles and after bodies of fighter aircrafts. The base drag is the major contribution of total drag for low speed regimes, flight tests have shown that the base drag may account for up to 50% of the total drag. Computational and experimental investigation for a hemispherical flight vehicle body of length 500mm and diameter 50mm was conducted for the purpose of investigating the base drag. Three case studies were conducted to investigate the properties of the flow field around the flight vehicle at different flow velocities of 20m/s, 30m/s and 50m/s at zero angle of attack (AoA). The three cases were (i) a flight vehicle with flat base configuration, (ii) a flight vehicle with a nozzle at the base and (iii) a flight vehicle configuration with a boat tail, Fig 1. Also, the three configurations were investigated at different AoA of -2ï‚°, 0ï‚° and +2ï‚°. The base drags for three configurations are calculated and the experimental results are compared with the CFD results.

Computational Analysis of Base Drag Reduction for a Subsonic Missile Projectile at Different Flow Velocity Conditions

Base drag is arising from flow separation at blunt base of a body. It can be a sizeable fraction of total drag in context of projectiles, missiles and after bodies of fighter aircrafts. The base drag is the major contribution of total drag for low speed regimes, flight tests have shown that the base drag may account for up to 50% of total drag. In this paper an experimental investigation for simple semi-circular flight vehicle body of length 500mm and diameter 50mm was conducted for the purpose of investigating base drag. The base drags for three configurations are calculated and the results are compared with CFD data. The three configurations used for testing are flat base configuration, closed nozzle configuration and boat tail configuration. The evaluation of base drag for three different flow velocities such as (i) 20m/s, (ii) 35m/s and (iii) 50m/s at different angle of attack such as -2ï‚°, 0ï‚° and 2ï‚° are experimented and compared.

Burst-and-coast swimmers optimize gait by adapting unique intrinsic cycle

This paper addresses the physical mechanism of intermittent swimming by considering the burst-and-coast regime of fish swimming at different speeds. The burst-and-coast regime consists of a cycle with two successive phases, i.e., a phase of active undulation powered by the fish muscles followed by a passive gliding phase. Observations of real fish whose swimming gait is forced in a water flume from low to high speed regimes are performed, using a full description of the fish kinematics and mechanics. We first show that fish modulate a unique intrinsic cycle to sustain the demanded speed by modifying the bursting to coasting ratio while maintaining the duration of the cycle nearly constant. Secondly, we show using numerical simulations that the chosen kinematics by correspond to optimized gaits for swimming speeds larger than 1 body length per second.

Forecasting the hazards of transport flows

The analysis of the indicators of the danger of conflict points on the equivalent intersections of roads along two directions of traffic of cars is considered: directly and to the left. Information is provided on the calculation of the forecast characteristics of the danger formed at the intersection of conflicting points in the current time mode by the input values of the speed of cars moving straight and to the left. Variations in the intensity of movement of cars moving in these two directions along the hour intervals are taken into account. Using the proposed methodology allows you to make decisions about the limitations of speed regimes and directions of traffic along the lanes of the carriageway.

The development of force in speed regime in the training of football players through the pliometric method

The development of force in speed regime in the training of football players through the pliometric method

Estimation of the instantaneous rotational frequency of gear transmission with large speed variations using short-time angular resampling and ridge-enhancing techniques

Instantaneous rotational frequency (IRF) is essential for most of the gear fault diagnosis methods used for nonstationary conditions. However, estimating the IRF under large speed-variation conditions is challenging. In this work, we developed a short time angular resampling and ridge-enhancing (STAR-RE) method for estimating the IRF of a gear transmission system of large speed variations. The method is integrated with a rigorous approach for eliminating ridge smearing based on angular resampling and a straightforward scheme for enhancing the target ridge by merging the ridges of several gear meshing harmonics. Data collected from a laboratory gearbox and an in-field wind turbine gearbox operated at variable speed regimes were used to test the accuracy and effectiveness of the STAR-RE method. The results indicated that the STAR-RE method achieved more accurate IRFs than the benchmark methods.

Performance Evaluation of CKF Based Sensorless Vector Controlled PM Synchronous Motor Drive

Sensor-less vector control of Surface Mount Permanent Magnet Synchronous Motor (SPMSM) throughout the entire speed regime is a challenging problem in PMSM drive. This paper addresses this control problem and presents the design and simulation study of sensor-less vector control of SPMSM using Cubature Kalman filter (CKF) based rotor position and speed estimator. The use of CKF for speed and position estimation of PMSM is reported in recently literature. However, the results are not substantial. Position and speed estimation errors are quite large, also the estimated speed and position contain considerably large ripple. In the present work the performance of CKF observer in terms of position and speed estimation accuracy is significantly improved. The dynamic performance of the drive throughout the entire speed zone under variable load torque is also improved.

Pitch damping identification in high speed regimes with a free-to-tumble rig

Many re-entry bodies, even if they are debris or not, have nonlinear dynamic stability characteristics that produce oscillations in flight. The free-to-tumble techniques can be used to extract damping coefficient of specific body for planetary entry. The curve fitting approach is used to predict oscillatory behavior and the damping coefficient for the various test conditions of the wind tunnel obtained after the experimental data. The analysis presented provides an overview of the free-to-tumble test techniques and illustrates the effects of dynamic stability of the inter-stage tronconical system. It is proposed that these test techniques and curve fitting solution be refined in the future to better define the dynamic stability curves for the re-entry bodies.