Conical Coil Research Articles

Computational fluid dynamic investigation of the primary and secondary atomization of the free-fall atomizer in electrode induction melting gas atomization process

Nickel-based superalloy is mainly used for fabricating the important high temperature parts including the turbine disk, turbine baffle, compressor disk, and other critical components. Ceramic inclusions in powder metallurgy (PM) superalloy could promote fatigue crack initiation, and thus accelerating the crack propagation under certain conditions. In this case, the ultra-clean nickel-based superalloy powder is critical for PM superalloy components. Generally, there are two well-known methods of fabricating superalloy powders, i.e., argon gas atomization (AA) and plasma rotating electrode process (PREP). Electrode induction melting gas atomization (EIGA) process is a newly developed method of preparing ultra-clean metal powders. The EIGA process is a completely crucible-free melting and atomization process developed by ALD vacuum technologies. In this process, a slowly rotating prealloyed bar is fed into a conical induction coil. The end of the bar is inductively heated and molten alloys falls into an atomizer where the liquid alloy is atomized with a high-pressure inert gas. The EIGA prepared powders possess the advantages of AA (more fine powders) and PREP (ultra-clean powders) processes. Generally, there are two key issues in EIGA process, and the free-fall gas atomizer design is one of the critical issues for the powder yield and quality. Free-fall gas atomizers are some of the first two fluid atomizer designs to be used for molten metal atomization. In a simple open (unconfined stream) design a melt stream falls from a tundish exit via gravity into the convergence of focused atomization gas jets where it is disintegrated. The gas-melt interaction is complex, and it is difficult to characterize the interaction process directly. To have a good understanding of the atomisation technology, the physical break-up process instead of correlating the gas dynamics with droplet fragmentation indirectly must be able to be examined. And it will be desirable, if we input the atomization parameters, we can obtain the particles' distributions directly. In this work, a computational fluid dynamic approach to simulating the primary and secondary atomization processes is developed by using the volume of fluid method and discrete phase model. By integrating the metal stream break-up (in primary atomization) with the flow field and particles distribution simulation (in second atomization), this numerical simulation method is able to provide the direct assessment for the atomisation process. To verify the method performance, the melt stream is initialized into a 4 mm-diameter stream, which is then injected into the gas flow field for further fragmentation. The experimental results show that the simulated particles' diameter distribution is consistent with the experimental results in the same conditions.

Collective acceleration of laser plasma in a nonstationary and nonuniform magnetic field

This paper presents the new experimental results concerning acceleration of deuterium ions extracted from laser plasma in the rapid-growing nonuniform magnetic field in order to initiate the nuclear reactions D(d, n)3He and T(d, n)4He. For obtaining of laser plasma a Nd: YAG laser (λ = 1,06 μm) that generates in Q-switched mode the radiation pulses with the energy W ≤ 0,85 J and duration of τ ≈ 10 ns was used. Rapid-growing magnetic field was created with the discharge of Arkadyev-Marx pulsed-voltage generator to conical coil with the inductance of 0,65 μΗ. At characteristic discharge time of 30 ns, the rate of magnetic field growth achieved 2·107 T/s. Ion velocity was determined with the time-of-flight technique. During the experiment on deuterium plasma an ion flux velocity of ∼3 · 108 cm/s was obtained, which corresponds to the deuteron energy of ∼100 keV. Herewith, for target power density of ∼5·1011 W/cm2 obtaining of up to 1015 of accelerated deuterons and up to 108 of neutrons per a pulse is expected.

Magnetic field homogeneity of a conical coaxial coil pair.

An analytical study of the magnetic field created by a double-conical conducting sheet is presented. The analysis is based on the expansion of the magnetic field in terms of Legendre polynomials. It is demonstrated analytically that the angle of the conical surface that produces a nearly homogeneous magnetic field coincides with that of a pair of loops that fulfills the Helmholtz condition. From the results obtained, we propose an electric circuit formed by pairs of isolated conducting loops tightly wound around a pair of conical surfaces, calculating numerically the magnetic field produced by this system and its heterogeneity. An experimental setup of the proposed circuit was constructed and its magnetic field was measured. The results were compared with those obtained by numerical calculation, finding a good agreement. The numerical results demonstrate a significant improvement in homogeneity in the field of the proposed pair of conical coils compared with that achieved with a simple pair of Helmholtz loops or with a double solenoid. Moreover, a new design of a double pair of conical coils based on Braunbek's four loops is also proposed to achieve greater homogeneity. Regarding homogeneity, the rating of the analyzed configurations from best to worst is as follows: (1) double pair of conical coils, (2) pair of conical coils, (3) Braunbek's four loops, (4) Helmholtz pair, and (5) solenoid pair.

Stability Test of a Pair of Conical Coils for Open-Bore MRI Magnet

To improve the openness of MRI scanners and reduce potential patient claustrophobia, a novel magnet concept with conical-shaped outermost main coils was investigated. This concept may also improve the coil stability because the Lorentz force acting on conical coils is mostly perpendicular to the coil/former interface, which may reduce friction-slip induced quench risk. A pair of conical superconducting coils has been tested to evaluate its stability. The test coil has 16° conical angle with a 50-cm diameter at the smaller diameter end. Both coils are supported by an aluminum former embracing coil OD surfaces. The pair of coils was ramped in a vertical Dewar with instrumentation measuring coil temperature, current, voltage, and strains. Two training quenches were observed at 74% and 81% Io/Ic before the coil current reached 100% of the short sample Ic value.

Simulation of the target creation through FRC merging for a magneto-inertial fusion concept

A two-dimensional magnetohydrodynamics model has been used to simulate the target creation process in a magneto-inertial fusion concept named Magnetized Plasma Fusion Reactor (MPFR) [C. Li and X. Yang, Phys. Plasmas 23, 102702 (2016)], where the target plasma created through Field reversed configuration (FRC) merging was compressed by an imploding liner driven by the pulsed-power driver. In the scheme, two initial FRCs (Field reversed configurations) are translated into the region where FRC merging occurs, bringing out the target plasma ready for compression. The simulations cover the three stages of the target creation process: formation, translation, and merging. The factors affecting the achieved target are analyzed numerically. The magnetic field gradient produced by the conical coils is found to determine how fast the FRC is accelerated to peak velocity and the collision merging occurs. Moreover, it is demonstrated that FRC merging can be realized by real coils with gaps showing nearly identical performance, and the optimized target by FRC merging shows larger internal energy and retained flux, which is more suitable for the MPFR concept.

Concentrical coils counter-current chromatography for natural products isolation: Salvia miltiorrhiza Bunge as example

Countercurrent chromatography (CCC) is an efficient separation technique without the solid support matrix, largely depending on the partition of two-immiscible liquid phases in the separation column. Since the helical coil planet centrifuge was invented in early 1970s by Yoichiro Ito, a series of coils columns, including spiral coils and conical coils columns have been developed for CCC separation. In this work, we introduced a new simple and efficient concentrical coils column for CCC separation, which was prepared by winding the whole polytetrafluoroethylene (PTFE) tube into the circular grooves from the rotation axis in the same direction. Once the PTFE tube filled in all space of one round of the circular groove, it was jumped into the nearby outer circular groove through the gap and until the whole groove was filled. The three same concentrical coils distributed on three disc-shaped holders were connected by the same PTFE tube to form concentrical coils separation column. The separation capacity was further investigated using ten tanshinones of the extracts of a Traditional Chinese Medicine Salvia miltiorrhiza Bunge as a model natural product. All results indicated that the concentrical coils column could hold satisfactory retention of the stationary phase, higher theoretical plate number and better resolution for CCC separation of more than ten tanshinones. It may be an alternative CCC column for non-targeted and targeted isolation of bioactive natural products.

Experimental investigation on heat transfer and pressure drop of conical coil heat exchanger

The heat transfer and pressure drop analysis of conical coil heat exchanger with various tube diameters, fluid flow rates, and cone angles is presented in this paper. Fifteen coils of cone angles 180? (horizontal spiral), 135?, 90?, 45?, and 0? (vertical helical) are fabricated and analysed with, same average coil diameter, and tube length, with three different tube diameters. The experimentation is carried out with hot and cold water of flow rate 10 to 100 L per hour (Reynolds range 500 to 5000), and 30 to 90 L per hour, respectively. The temperatures and pressure drop across the heat exchanger are recorded at different mass flow rates of cold and hot fluid. The various parameters: heat transfer coefficient, Nusselt number, effectiveness, and friction factor, are estimated using the temperature, mass flow rate, and pressure drop across the heat exchanger. The analysis indicates that, Nusselt number and friction factor are function of flow rate, tube diameter, cone angle, and curvature ratio. Increase in tube side flow rate increases Nusselt number, whereas it reduces with increase in shell side flow rate. Increase in cone angle and tube diameter, reduces Nusselt number. The effects of cone angle, tube diameter, and fluid flow rates on heat transfer and pressure drop characteristics are detailed in this paper. The empirical correlations are proposed to bring out the physics of the thermal aspects of the conical coil heat exchangers.

Performance scaling of inductive pulsed plasma thrusters with coil angle and pulse rate

A circuit model for an inductive pulsed plasma thruster was developed in order to investigate the performance of thrusters with conical coils; the model can accommodate cone-angles from 0° (a straight theta-pinch coil) to 90° (a planar coil). The plasma is treated as a deformable slug that moves both radially and axially in response to the force applied by the coil. The radial equation of motion includes a restoring force due to the plasma pressure, which is derived under the assumption that the electron population is isothermal, while the ions are isothermal, adiabatic, or shock-heated depending on the magnitude and sign of the radial velocity. The inductance of the coil and the plasma slug, and their mutual inductance, was determined using QuickField. A local maximum in efficiency and specific impulse was found for angles less than 90°; however the absolute maximum for both these quantities occurs at 90°. High pulse-rate operation was found to yield dynamic efficiencies (excluding ionization cost) as high as 60–70% for ISP in the range of 3000–5000 s, even for a device with modest jet-power (5 kW). This mode of operation also permits elimination of the pulsed gas valve, which would be a significant system-level simplification. An alternate mode of inductive recapture, in which the current is interrupted at the second zero-crossing, was found to result in a sacrifice of only 1–2% in efficiency, while offering other significant system-level benefits for this kind of thruster.

Investigation on thermal analysis of conical coil heat exchanger

The experimental investigation on thermal analysis of conical coil heat exchanger is presented in this paper. Fifteen conical coils of different cone angles (0° (helical), 45°, 90°, 135°, 180° (spiral)), with three different tube sizes (ID×OD, 8×10, 10×12 and 12×15) are fabricated and analysed with, same average coil diameter (Dm=200mm) and tube length (L=3m). The experimentation is carried out with hot and cold water of flow rate 10–100lph (Re – 500 to 5000) and 30–90lph respectively. The observations recorded were leads to analysis the heat exchanger for heat transfer and pressure drop characteristics at different flow rate of cold and hot fluid. The various parameters (heat transfer coefficient (hi), Nusselt number (Nu) effectiveness (ε) and friction factor (f)) are estimated for the heat exchanger. The analysis indicates that, Nu and f are the functions of flow rates, tube diameter, curvature ratio and cone angle. Nu increase with increase in tube side flow rate whereas it reduces with increase in shell side flow rate, increase in cone angle and increase in tube diameter. The effects of cone angle, tube diameter and fluid flow rates on heat transfer and pressure drop characteristics are detailed in this paper. The empirical correlations are proposed to bring out the physics of the thermal aspects of the conical coil heat exchangers.

Experimental investigation on heat transfer analysis of conical coil heat exchanger with 90° cone angle

In the present study, an experimental investigation on thermal performance of the conical coil heat exchanger with 90° conical coil heat exchanger is reported. Three different conical coil heat exchangers of same mean coil diameter (Dm = 200 mm) with different tube diameters (di = 8, 10, 12.5 mm) are analyzed under steady state condition. The analysis is carried out for the tube side hot fluid flow range of 10–100 lph (Re = 500–5,000), while the shell side flow range of 30–90 lph. The data available from experimentation leads to evaluate heat transfer coefficients for inside and outside the tube of the conical coil heat exchanger by Wilsons plot method. The calculations are further extended to estimate Nusselt Number (Nu) and effectiveness. The empirical correlations are proposed for predicting Nu and the outlet temperatures of hot and cold fluids. The predicted empirical correlations show reasonable agreement with the experimental results within the given range of parameters.

Conical coils counter-current chromatography for preparative isolation and purification of tanshinones from Salvia miltiorrhiza Bunge

Modern counter-current chromatography (CCC) originated from the helical coil planet centrifuge. Recently, spiral coils were found to possess higher separation efficiency in both the retention of stationary phase and solutes resolution than other CCC coils like the helical and toroidal coils used on type-J CCC and cross-axis CCC. In this work, we built a novel conical coil CCC for the preparative isolation and purification of tanshinones from Salvia miltiorrhiza Bunge. The conical coils were wound on three identical upright tapered holders in head-to-tail and left-handed direction and connected in series. Compared with helical and spiral coil CCC, conical coil CCC not only placed CCC column in a two-dimensional centrifugal field, but also provided a potential centrifugal force gradient both in axial and radial directions. The extra centrifugal gradient made mobile phase move faster and enabled CCC much higher retention of stationary phase and better resolution. As a result, higher efficiency has been obtained with the solvent system of hexane–ethyl acetate–methanol–water (HEMWat) with the volume ratio of 5:5:7:3 by using conical coil CCC apparatus. Four tanshinones, including cryptotanshinone (1), tanshinone I (2), 1,2-dihydrotanshinquinone (3) and tanshinone IIA (4), were well resolved from 500mg to 1g crude samples with high purity. Furthermore, the conical coil CCC can make a much higher solid phase retention, which makes it to be a powerful separation tool with high throughput. This is the first report about conical coil CCC for separation of tanshinones and it may also be an important advancement for natural products isolation.

Effect of experimental parameters on needleless electrospinning from a conical wire coil

AbstractIn this study, a conical wire coil was used as spinneret to launch a novel needleless electrospinning. Multiple polymer jets were observed on the surface of the coil in the electrospinning process. Productivity of the nanofibers can be enhanced to >2.5 g/h by using this novel nozzle. The fiber productivity and diameter together with diameter distribution were dependent on the concentration of the polymer solution, applied voltage, and collecting distance. This novel concept of using wire coil as the electrospinning nozzle depicts a model of large‐scale needleless electrospinning system for nanofiber production. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Evaluation of the heat transfer performance of helical coils of non-circular tubes

This study addresses heat transfer performance of various configurations of coiled non-circular tubes, e.g., in-plane spiral ducts, helical spiral ducts, and conical spiral ducts. The laminar flow of a Newtonian fluid in helical coils made of square cross section tubes is simulated using the computational fluid dynamic approach. The effects of tube Reynolds number, fluid Prandtl number, coil diameter, etc., are quantified and discussed. Both constant wall temperature and constant heat flux conditions are simulated. The effect of in-plane coil versus a cylindrical design of constant coil, as well as a conical coil design is discussed. Results are compared with those for a straight square tube of the same length as that used to form the coils. Advantages and limitations of using coiled tubes are discussed in light of the numerical results.

Needleless electrospinning of nanofibers with a conical wire coil

AbstractIn this article, we have demonstrated a novel needleless electrospinning of PVA nanofibers by using a conical metal wire‐coil as spinneret. Multiple polymer jets were observed to generate on the coil surface. Up to 70 kV electric voltage can be applied to this needleless electrospinning nozzle without causing “corona discharge.” Compared with conventional needle electrospinning, this needleless electrospinning system produced finer nanofibers on a much larger scale, and the fiber processing ability showed a much greater dependence on the applied voltage. Finite element calculation indicates that the electric field intensity profiles for the two systems are also quite different. This novel concept of using wire coil as the electrospinning nozzle will contribute to the further development of new large‐scale needleless electrospinning system for nanofiber production. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Comparison of Directly and Inductively Coupled Pulsed Electromagnetic Thrusters

Pulsed electromagnetic plasma accelerators and, more specifically, those that are inductively coupled potentially have high thrust density, high specific impulse, and long thruster lifetime since there is limited contact between the plasma and coil(s). One-dimensional electromechanical models of these thrusters, which are important for identifying important relationships among circuit parameters, coil geometry, and plasma, usually make the same underlying assumption about the mutual inductance between the primary coil and induced plasma current, based on empirical evidence. This approach is inconvenient for arbitrary coil geometries and if trying to make comparisons with directly coupled plasma accelerators, such as coaxial plasma guns. A generalized slug model was developed in which RLC circuit equations are coupled to a mechanical force equation. The acceleration term was made to be thruster and geometry dependent, so that the same model could be used to study both coaxial plasma guns and conical theta pinches. The calculated mutual inductance from the coil model exhibits the same exponential falloff with distance as in previous models and experiments. Efficiency (plasma kinetic energy divided by initial capacitor bank energy) and exhaust velocity were calculated for the conical theta pinch coil over a 5-D parameter space. For the cases with highest efficiencies, peak coaxial plasma accelerator efficiencies were calculated under certain operating constraints. It was found that, while coaxial plasma accelerators are generally more efficient, under certain conditions, the conical theta pinch performance is higher.

Low Torque Engine Valve System Using Conical Coil Spring and Electromagnetic Actuator

In this research, a new type valve system using a conical coil spring and an electromagnetic actuator was developed. This system uses a conical coil spring whose spring constant is low, and therefore, the valve system has a low torque in a low-speed rotation mode. As a result, the energy loss in a low-speed rotation is decreased. However, the jump and bounce phenomena would happen in the high-speed rotation mode. The phenomena are suppressed by using an electromagnetic actuator consisting of two permanent magnets and electromagnet. The electromagnetic actuator strengthens the restoration force of the spring by the repulsive force, and controls the jump and bounce phenomena. It was confirmed that the use of a conical coil spring lessened the load torque in this experiment and that the jump and bounce phenomena were suppressed by using the present electromagnetic actuator.

Adiabatic model and design of a translating field reversed configuration

We apply an adiabatic evolution model to predict the behavior of a field reversed configuration (FRC) during decompression and translation, as well as during boundary compression. Semi-empirical scaling laws, which were developed and benchmarked primarily for collisionless FRCs, are expected to remain valid even for the collisional regime of FRX-L experiment. We use this approach to outline the design implications for FRX-L, the high density translated FRC experiment at Los Alamos National Laboratory. A conical theta coil is used to accelerate the FRC to the largest practical velocity so it can enter a mirror bounded compression region, where it must be a suitable target for a magnetized target fusion (MTF) implosion. FRX-L provides the physics basis for the integrated MTF plasma compression experiment at the Shiva-Star pulsed power facility at Kirtland Air Force Research Laboratory, where the FRC will be compressed inside a flux conserving cylindrical shell.

Numerical Investigation of Forced Fluid Flow and Heat Transfer from Conically Coiled Pipes

Numerical investigations were conducted to understand forced laminar fluid flow over coiled pipes with circular cross-section. The focus was addressed on exploring the convective heat transfer from conical and helical coils with comparative studies. The same numerical investigation method was applied to the two differentially coiled pipes (helical and conical) and for different Reynolds numbers corresponding to five cases of exterior flow arrangement. The results show better heat transfer performance for cases of conical coils where much flow turbulence was observed due to an effective flow arrangement.

Experimental chaos in nonlinear vibration isolation system

The chaotic vibration isolation method was studied thoroughly from an experimental perspective. The nonlinear load-deflection characteristic of the conical coil spring used in the experiment was surveyed. Chaos and subharmonic responses including period-2 and period-6 motions were observed. The line spectrum reduction and the drop of the acceleration vibration level in chaotic state and that in non-chaotic state were compared, respectively. It was concluded from the experiment that the nonlinear vibration isolation system in chaotic state has strong ability in line spectrum reduction.

Physics Basis and Progress for a Translating FRC for MTF

We describe a physics scaling model used to design the high density field reversed configuration (FRC) at LANL that will translate into a mirror bounded compression region, and undergo Magnetized Target Fusion compression to a high energy density plasma. At Kirtland AFRL the FRC will be compressed inside a flux conserving cylindrical shell. The theta pinch formed FRC will be expelled from inside a conical theta coil. Even though the ideal FRC has zero helicity and toroidal magnetic field, significant non-ideal properties follow from formation within a conical (not cylindrical) theta coil. The FRC stability and lifetime properties may improve. Several experimental features will also allow unique scientific investigations of this high Lundquist number but collisional plasma.