Increase Of Taper Angle Research Articles

Enhancement in air-cooling of lithium-ion battery packs using tapered airflow duct

Temperature uniformity and peak-temperature reduction of lithium-ion battery packs are critical for adequate battery performance, cycle life, and safety. In air-cooled battery packs that use conventional rectangular ducts for airflow, the insufficient cooling of cells near the duct outlet leads to temperature nonuniformity and a rise in peak temperature. This study proposes a simple method of using a converging, tapered airflow duct to attain temperature uniformity and reduce peak temperature in air-cooled lithium-ion battery packs. The conjugate forced convection heat transfer from the battery pack was investigated using computational fluid dynamics, and the computational model was validated using experimental results for a limiting case. The proposed converging taper provided to the airflow duct reduced the peak temperature rise and improved the temperature uniformity of the batteries. For the conventional duct, the boundary layer development and the increase in air temperature downstream resulted in hotspots on cells near the outlet. In contrast, for the proposed tapered duct, the flow velocity increased downstream, resulting in improved heat dissipation from the cells near the outlet. Furthermore, the study investigated the effects of taper angle, inlet velocity, and heat generation rate on the flow and thermal fields. Notably, with the increase in taper angle, owing to the increase in turbulent heat transfer near the exit, the location of peak temperature shifted from the exit region to the central region of the battery pack. The taper-induced improvement in cooling was evident over the entire range of inlet velocities and heat generation rates investigated in the study. The peak temperature rise and maximum temperature difference of the battery pack were reduced by up to 20% and 19%, respectively. The proposed method, being effective and simple, could find its application in the cooling arrangements for battery packs in electric vehicles.

Electrochemical machining of blades by using tapered cathode sheet with micro-grooves structure

The combined electrode with cathode body and cathode sheet is widely used in the electrochemical machining of ruled surface parts. Due to the thickness of the cathode sheet, however, stray corrosion of the side wall of the cathode sheet will affect the machining accuracy and surface quality of the workpiece. In order to suppress stray corrosion, a tapered cathode sheet with a micro-grooves structure is proposed in this paper, which reduces the intensity of the stray electric field by increasing the distance between the side wall of the cathode sheet and the workpiece. According to the electric field distribution, the current density on the surface of the machined anode workpiece decreases as the cathode taper angle increases. In addition, to enhance the liquid-phase mass transfer, a micro-grooves structure was fabricated in the side wall of the tapered cathode sheet. Through the numerical simulation analysis of the flow field, the micro-grooves structure reduces the flow resistance of the electrolyte and suppresses stray corrosion of the dispersed electrolyte. Finally, the experimental results show that the ruled surface blade with a machining taper of 0.93° and blade surface roughness of 0.566 μm can be successfully obtained using a 50° tapered cathode sheet with a micro-grooves structure. This study provides an effective process that can be used for the ECM of ruled surface parts with high precision and good quality, and in the future this process can be extended to machining space complex surface parts.

A Simple Approach for the Dynamic Analysis of a Circular Tapered Pile under Axial Harmonic Vibration

The tapered pile offers sustainable use of construction materials due to its higher axial and lateral capacity and better performance owing to its geometry. This paper develops a semi-analytical solution of the vertical dynamic impedance of the tapered pile based on the dynamic Winkler theory and transfer matrix method. The accuracy and reliability of the proposed approach are verified by comparing the impedance functions of cylindrical and tapered piles obtained from the analytical solution and finite element analysis. A parametric study is performed to investigate the influence of the taper angle on the vertical dynamic impedance and resonant frequency. The results reveal that the taper angle has a significant influence on the vertical dynamic impedance, while it does not affect the oscillation period of the dynamic impedance and the resonant frequency. Besides, the vibration performance of the tapered pile is better than that of a cylindrical pile with the same volume. For a fixed-volume tapered pile, varying the pile length while keeping the pile tip diameter constant yields a better dynamic impedance than varying the pile tip diameter while keeping the pile length constant. Finally, the vertical displacement amplitude of the tapered pile decreases as the taper angle increases, especially for high-frequency excitation.

Taper angle dependence of the dynamical transmission of several-hundred-keV protons through PC conical capillary

The dynamical transmission of intermediate-energy protons through a polycarbonate (PC) conical capillary with taper angle from 0.48° to 2° are simulated. The results show that for small taper angle of 0.48°, the transmission of 100 keV protons is dominated by the deposited-charge-assisted specular reflection. This reflection effect decreases with the increase of the taper angle. When the taper angle is increased to 2°, the transmission of the protons is mainly influenced by small angle scattering, which is consistent with the experimental data. The asymptotic transmission rate decreases with the increase of the capillary taper angle. These results suggest that the deposited-charge-assisted specular reflection is significant in focusing several-hundred-keV protons.

Theoretical investigations for combination optical fiber tip sensors

For the optical fiber biosensor made of combination optical fiber tip, the effects of the refractive index RI of outer medium and the geometrical parameters of combination optical fiber tip on two important quantities have been investigated. One factor is the total intensity of the evanescent wave into fluorescent layer through core-medium interface; the other is the intensity of the fluorescence signal transmitted from fluorescent layer to measurement end. Theoretical investigations show that the two quantities are dependent upon the RI of outer medium, and the total intensity of the evanescent wave into fluorescent layer increases with the increase of taper angle, and the fluorescence signal arrived at the measurement end gets larger value for shorter fiber tip when the RI of outer medium is smaller than the RI of fiber core.

Experimental and theoretical study on hydrodynamic characteristics of tapered fluidized beds

A novel fluidized bed ash cooler was developed for circulating fluidized bed boilers based on a proposed modified tapered fluidized bed. A cold model was built to study the hydrodynamic characteristics of the modified tapered fluidized bed, and its critical superficial gas velocity umf and critical velocity for full fluidization umff were particularly studied. The effects of taper angle α, static bed height H, air inlet section width δ and particle size dp on the umf and umff were experimentally investigated. Furthermore, a theoretical model and an empirical correlation have been proposed to predict the umf and umff, respectively. The predicting capabilities of the model and correlation have been experimentally discussed. And the predicting capability of the model has also been compared with that of an existing representative model. It is found that both the umf and umff increase with the increase of taper angle α, static bed height H and particle size dp, but decrease with the increase of air inlet section width δ, respectively. Additionally, the predicted values of umf and umff compare well with the experimental data, and the model has a better capability than the existing representative model in predicting the umf of the modified bed.

Coherent beam combination of fiber lasers with a strongly confined tapered self-imaging waveguide: theoretical modeling and simulation

Coherent beam combination (CBC) of fiber lasers based on self-imaging properties of a strongly confined tapered waveguide (SCTW) is studied systematically. Analytical formulas are derived for the positions, amplitudes, and phases of the N self-images at the output of a SCTW, which are important for quantitative analysis of waveguide-based CBC. The formulas are verified with numerical examples by a finite difference beam propagation method (FDBPM) and the errors of the analytical expressions are studied. This study shows that the analytical formulas agree well with the FDBPM simulation results when the taper angle is less than 1.4° and the phase distortion is less than λ/10. The relative errors increase as the taper angle increases. Based on the theoretical model and the FDBPM, we simulated the CBC of fiber laser array and compared the CBC based on the tapered waveguide with that based on the nontapered one. The effects of input beam number, aperture fill factor, and taper angle on the combination performance have been studied. The study reveals that a beam which has near-diffraction limited beam quality (M2≤1.41) and a single beam without side lobe in the far field can be achieved with tapered-waveguide-based CBC. It is shown that beam quality depends on input beam number, aperture fill factor, and taper angle. There exists a best fill factor which will increase as input beam number increases. The tolerance of the system on the fill factor and the taper angle is studied, which is 0.45<t<0.67 and θ<0.8°, respectively. The results may be useful for practical, high-power fiber laser systems.

Computational analysis for the effect of the taper angle and helical pitch on the heat transfer characteristics of the helical cone coils

This numerical research is devoted to introducing the concept of helical cone coils and comparing the performance of helical cone coils as heat exchangers to the ordinary helical coils. Helical and spiral coils are known to have better heat and mass transfer than straight tubes, which is attributed to the generation of a vortex at the helical coil. This vortex, known as the Dean Vortex, is a secondary flow superimposed on the primary flow. The Dean number, which is a dimensionless number used in describing the Dean Vortex, is a function of Reynolds Number and the square root of the curvature ratio, so varying the curvature ratio for the same coil would vary the Dean Number. Numerical investigation based on the commercial CFD software fluent is used to study the effect of changing the structural parameters (taper angle of the helical coil, pitch and the base radius of curvature changes while the height is kept constant) on the Nusselt Number, heat transfer coefficient and coil outlet temperature. Six main coils having pipe diameters of 10 and 12.5 mm and base radius of curvature of 70, 80 and 90 mm were used in the investigation. It was found that, as the taper angle increases, both Nusselt Number and the heat transfer coefficient increase, also the pitch at the various taper angles was found to have an influence on Nusselt Number and the heat transfer coefficient. A MATLAB code was built to calculate the Nusselt Number at each coil turn, then to calculate the average Nusselt number for all of the coil turns. The MATLAB code was based on empirical correlation of Manlapaz and Churchill for ordinary helical coils. The CFD simulation results were found acceptable when compared with the MATLAB results.

Near-field thermal transport in a nanotip under laser irradiation

We report on a systematic study of highly enhanced optical field and its induced thermaltransport in nanotips under laser irradiation. The effects on electric field distributioncaused by curvature radius, tip aspect ratio, and polarization angle of the incident laser arestudied. Our Poynting vectors’ study clearly shows that when a laser interacts with a metaltip, it is bent around the tip and concentrated under the apex, where extremely high fieldenhancement appears. This phenomenon is more like a liquid flow being forced/squeezed togo through a narrow channel. As the tip–substrate distance increases, the peak fieldenhancement decreases exponentially. A shift of field peak position away from the tip axisis observed. For the incident light, only its component along the tip axis direction has acontribution to the electric field enhancement under the tip apex. The optimum tipapex radius for field enhancement is about 9 nm when the half taper angle is10°. Fora tip with a fixed radius of 30 nm, field enhancement increases with the half taper angle when it is lessthan 25°. The thermal transport inside the nanoscale tungsten tips due to absorption of incidentlaser light is explored using the finite element method. A small fraction of lightpenetrates into the tip. As the polarization angle or apex radius increases, thepeak apex temperature decreases. The peak apex temperature goes down as thehalf taper angle increases, even though the mean laser intensity inside the tipincreases, revealing a very strong effect of the taper angle on thermal transport.

Field Press–in Test of Tapered Steel Pipe and Timber Piles

A relatively simple method was proposed in a previous study for predicting the vertical behavior of tapered piles penetrating from the ground surface. This method uses the radial cavity expansion theory to model the increase in side resistance due to the radial ground expansion as a tapered pile is being pressed, and applies the second theory of the ultimate point bearing capacity proposed by Takano N. for the point resistance. Field press–in tests were conducted on four steel sheet piles and nine timber piles at a site mainly composed of silty layers. This paper presents the test results of these four steel piles and three timber piles including one straight–sided steel pile and one straight–sided timber pile. Pile resistance obtained from field tests is compared with the predictions made by the proposed analytical method. As expected, the shaft resistance increased with the increase in taper angle and the tapered piles offered a larger resistance than the straight–sided piles. It was also found that, on sites consisting of extremely soft soil, the penetration force–displacement relationships are very sensitive to the internal frictional angle of the soil.

A Study on Abrasive Water Jet Machining of Aluminum with Garnet Abrasives

In this study the effect of some cutting variables on the quality of the surface pnxiuced during abrasive water jet machining of aluminum has been investigated. The type of abrasive used was gamet of mesh size 80. The machining was done on the abrasive water jet machine WJ4080. The cutting variables were stand-off distance of the nozzle from the work surface. work feed rate and jet pressure. The evaluating criteria of the surface produced were width of cut, taper of the cut slot and work surface roughness. It was found experimentally that in order to minimize the width of cut; the nozzle should be placed close to the work surface. Increase in jet pressure results in widening of the cut slot both at the top and the at exit of the jet from the work. However. the width of cut at the bottom (exit) was always found to be larger than that at the top (at a stand-off distance of 3 mm and the work feed rate of 15 mm min-I). It was found that the taper of cut gradually reduces with increase in stand-off distance and was close to zero at the stand-off distance of 4 nun (at ajetpressure of 30 ksi and a work feed rate of 15 mm min-I). The feed rate of the work should be kept within 40 rum min- I (at the jet pressure of 30 h i and the stand-off distance of3 mm). because a feed rate beyond 40 mm min-I results in sharp increase in taper angle. The jet pressure does not show significant influence on the taper angle within the range of work feed and the stand-off distance considered. Both stand-off distance and the work feed rate show strong influence on the roughness of the machined surface. It was concluded that stand-off distance should be kept within 3 mm (at aiet pressure oDD ksi and a work feed rate ofl5 mm min-') and the work feed rate should be kept within 30 rum min-I (at ajetpressure of 30 hi and a stand-off distance of 3 nun) in order to have a good surface finish, since beyond those values of the parametern the roughness of the machined surface rises sharply. Increase in jet pressure shows positive effect in tenus of smoothness of the machined surface. With increase in jet pressure, the surface roughness decreases (at a stand-off distance of3mm and work feed of 15 mm min-I). This is due to fragmentation of the abrasive particles into smaller sizes at a higher pressure and due to the fact that smaller particles produce smoother surface. It was also found that within the jet pressure considered, the work surface is smoother near the top surface and gradually it becomes rougher at higher depths.

Computer simulation and energy absorption of tapered thin-walled rectangular tubes

Tapered thin-walled tubes have been considered desirable energy absorbers under axial loading due to their relatively stable crush load and deformation response compared with straight tubes. This paper compares the energy absorption response of straight and tapered thin-walled rectangular tubes under quasi-static axial loading, for variations in their wall thickness, taper angle and number of tapered sides. Overall the study highlights the advantages of using tapered tubes as energy absorbers. In particular, the peak load required to crush the tubes decreases with the introduction of a taper, and as the taper angle increases. This is desirable for minimising the impact loads transmitted to the protected structure. The practical outcome of the study is design information for the use of tapered thin-walled rectangular tubes as energy absorbers in impact loading applications. Analysis has been undertaken using a finite element model, validated using existing theoretical and numerical models.

Two-dimensional model for tapered pulse tubes. Part 2: mass streaming and streaming-driven enthalpy flow loss

The effects of the taper angle and the frequency on the steady mass flux and the enthalpy flow loss associated with the steady mass streaming were analyzed by two-dimensional analysis of the tapered pulse tube. It was shown that the mass streaming could lead to a large steady second-order temperature. The enthalpy flow loss driven by the mass streaming increases as the frequency increases. For the pulse tube where the viscous penetration depth is far thinner than the inner radius, the enthalpy flow loss can be significantly reduced by tapering the pulse tube since the steady mass flux and the steady second-order temperature decrease as the taper angle increases.

Fabrication and characterization of optical-fiber nanoprobes for scanning near-field optical microscopy

The current scanning near-field optical microscopy has been developed with optical-fiber probes obtained by use of either laser-heated pulling or chemical etching. For high-resolution near-field imaging, the detected signal is rapidly attenuated as the aperture size of the probe decreases. It is thus important to fabricate probes optimized for both spot size and optical transmission. We present a two-step fabrication that allowed us to achieve an improved performance of the optical-fiber probes. Initially, a CO(2) laser-heated pulling was used to produce a parabolic transitional taper ending with a top thin filament. Then, a rapid chemical etching with 50% buffered hydrofluoric acid was used to remove the thin filament and to result in a final conical tip on the top of the parabolic transitional taper. Systematically, we obtained optical-fiber nanoprobes with the apex size as small as 10 nm and the final cone angle varying from 15 degrees to 80 degrees . It was found that the optical transmission efficiency increases rapidly as the taper angle increases from 15 degrees to 50 degrees , but a further increase in the taper angle gives rise to important broadening of the spot size. Finally, the fabricated nanoprobes were used in photon-scanning tunneling microscopy, which allowed observation of etched double lines and grating structures with periods as small as 200 nm.

Interface shape and radial distribution of impurities in 〈111〉 silicon crystals

The solid-liquid interface shape at the shoulder of ingot growth is affected by the taper angle. The interface changes from concave to convex with an increase of taper angle. The interface shape at the main body of ingot growth depends on the crystal length. The interface becomes more concave with increase in the length of a crystal. The radial dopant distribution has been correlated with the interface shape and its radius of curvature. No correlation is found between the interface shape and radial distribution of oxygen or carbon.