共查询到11条相似文献,搜索用时 0 毫秒
1.
《Journal of Nuclear Science and Technology》2013,50(4):199-208
An analysis is made on the performance characteristics of a liquid-metal MHD induction converter with liquid-gas two-phase mixture as working fluid. The equivalent electrical conductivity and the velocity vary along the generator channel in this kind of induction converter. Two important parameters which represent the variations of the equivalent electrical conductivity and the velocity respectively are defined. With these parameters the induction equation is analytically solved with the perturbation technique. Quantities representing generator performance, such as power densities and generator efficiency, are obtained from the perturbed magnetic field and the parameters mentioned above. Suitable combination of values for these parameters will tend to let the effects brought by the variations of electrical conductivity and of velocity cancel each other, and the relation between these parameters is analytically derived that assures the non- perturbation of the magnetic field and of the gross output power density. In this condition of non-perturbation, the generator efficiency approaches that for the unperturbed case when the velocity variation and the inlet slip ratio are small. 相似文献
2.
《Journal of Nuclear Science and Technology》2013,50(7):435-445
This paper describes a new correlation for predicting a two-phase frictional pressure drop multiplier, and discusses the pressure level effects and the mass velocity effects. This correlation predicts satisfactorily the frictional pressure drop not only for liquid metals but also for ordinary fluid two-phase flow in a wide range of flow variables. The authors' void fraction correlation previously proposed is also compared with published data of void fraction for liquid metal two-phase flow, and is found to represent well the mass velocity effects. Wettability and magnetohydrodynamic effects are discussed briefly in relation to the hydrodynamic characteristics of liquid metal two-phase flow. 相似文献
3.
《Journal of Nuclear Science and Technology》2013,50(10):729-735
In the previous paper, the authors pointed out the motion of bubble or gaseous phase in the direction to the both side walls due to the pinch effect caused by the induced magnetic field in the liquid metal two-phase flow under the strong magnetic field. In the present paper, to clarify the existence of the pinch effect experimentally, an experimental study was performed. Firstly the distributions of the void fraction in the cross section perpendicular to the flow were measured at three locations in the flow direction for the various strength of the applied magnetic field. Secondly a magnetic field was superposed on the induced magnetic field by the outer coil to disturb the pinch effect by the cancel of the induced magnetic field with the superposed one, resulting in the evident redistribution of the void-fraction profile obtained above. From these experiments it is concluded that the pinch effect will play an important role to redistribute the bubble or gaseous phase in the liquid metal two-phase flow under the strong magnetic field and that the effect is more promoted with increasing magnetic interaction number defined as a ratio of the electromagnetic force to the inertia of the fluid. 相似文献
4.
《Journal of Nuclear Science and Technology》2013,50(9):378-386
In the present paper, the performance characteristics of a liquid metal MHD induction converter operated with two-phase mixture flow are treated experimentally and analytically in comparison with those with single-phase liquid flow as working fluid. The experiments were performed with a flat-linear channel induction converter, through which NaK-N2 two-phase mixture was made to flow at a velocity ranging 5–30m/sec, with a void fraction 0–50%. Data were taken over the following range of non-dimensional parameters:
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Reynolds number: 3.3x104–2.0x105 (for liquid flow alone)
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Hartmann number: 12 (with magnetic field in r.m.s. and slip S = 1)
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Baroczy's property index: 0.0031–0.023 (for two-phase flow)
5.
《Journal of Nuclear Science and Technology》2013,50(12):753-755
A correlation function for reactor noise is determined through a conditional polarity-correlation technique in which the polarity of neutron-counting fluctuations is analyzed with the start condition that the counting rate reaches a preset level. This technique, evidently, is an example of flash-start technique, developed for the purpose of improving the efficacy of reactor noise analysis. In the present case, the conditional polarity-correlation function is described mathematically assuming that the counting fluctuations of the detector conform with a Gaussian distribution. The expression thus derived reveals that this function is approximately proportional to a cross-correlation function and is a differential type of polarity-correlation function. In order to examine the validity of the obtained expression, an experiment was performed in a graphite-moderated reactor at slightly subcriticai state to measure the conditional polarity-correlation function. A novel contrivance was adopted in the experiment to eliminate the dead-time effect created during the busy time of the multi-channel time analyzer. The dependence on the preset level—i.e. flash-start condition—exhibited by the conditional polarity—correlation function showed good agreement with that expected from the mathematical expression. The prompt mode neutron decay constants were determined from the experimental data within statistical error of 3~4 %. 相似文献
6.
Preliminary analysis and calculation of liquid metal Li17Pb83 magnetogydrodynamic (MHD) pressure drop in the blanket for the FDS have been presented to evaluate the significance of MHD effects on the thermal-hydraulic design of the blanket.To decrease the liquid metal MHD pressure drop,Al2O3 is applied as an electronically insulated coating onto the inner surface of the ducts.The requirement for the insulated coating to reduce the additional leakage pressure drop caused by coating imperfections has been analyzed.Finally,the total liquid metal MHD pressure drop and magnetic pump power in the FDS blanket have been given. 相似文献
7.
《Journal of Nuclear Science and Technology》2013,50(4):219-226
In this paper, the frictional pressure drop in an isothermal liquid metal-gas two-phase flow through a rectangular channel with large width-to-height ratio is treated semiempirically for a NaK-N2 two-phase flow system. The frictional pressure drop in the two-phase flow is compared with the following two reference values : 1. The frictional pressure drop in the liquid flowing alone in single phase with the same velocity as that of the liquid in the two-phase mixture. 2. The frictional pressure drop in the liquid flowing alone in single phase with the same mass flow rate as that of the liquid in the two-phase mixture. The comparison with the former reference value is necessary for the prediction of friction loss in a liquid metal MHD generator channel whose medium would be two-phase mixture. The semiempirical analysis was performed assuming the two-phase mixture to be a continuous medium with its properties, e.g. viscosity and density, defined by void fraction and the velocity determined by the total mass flow rate. In the region of low slip and density ratio ρg/ρl the frictional pressure drop in the two-phase flow appeared to be smaller than that due to the liquid flowing alone with the same velocity as that of the liquid in the two-phase flow. The experiments have been undertaken with the NaK-N2 two-phase mixture flowing through a rectangular channel (4 × 60 mm2). Data were taken over the following parameter range: NaK velocity: 5~30 m/sec, Void fraction: 0~70% Density ratio: 0.006~0.013, Quality: 0.07~1.10%. 相似文献
8.
Magnetohydrodynamic (MHD) pressure drop in the Chinese Dual Functional Liquid Lithium-lead Test Blanket Module (DFLL-TBM) proposed for ITER is discussed in this paper. Electrical insulation between the coolant channel surfaces and the liquid metal is required to reduce the MHD pressure drop to a manageable level. Insulation can be provided by a thin insulating coating, such as Al2O3, which can also serve as a tritium barrier layer, at the channel surfaces in contact with LiPb. The coating's effectiveness for reducing the MHD pressure drop is analysed through three-dimensional numerical simulation. A MHD-based commercial computational fluid dynamic (CFD) software FLUENT is used to simulate the LiPb flow. The effect on the MHD pressure drop due to cracks or faults in the coating layer is also considered. The insulating performance requirement for the coating material in DFLL-TBM design is proposed according to the analysis. 相似文献
9.
《Journal of Nuclear Science and Technology》2013,50(12):886-898
For gas-liquid two-phase flow, two kinds of fundamental equations have been proposed by the methods of hydrodynamics and hydraulics. The hydrodynamic equation, to avoid analytical difficulties, does not deal with two-phase flow itself, but with a hypothetical liquid flow which has actual physical quantities in the region where the liquid phase really exists and has the imaginary physical quantities of liquid in the region where the gas exists, for each instant, and with a hypothetical gas flow similarly. The hydraulic equation differs from the usual form in the treatment of friction term or interaction, and has better physical insight. These equations are analyzed mathematically and some relationship between physical quantities centering void fraction are discussed. Hydrodynamic equation shows the void fraction distribution to have relation to pressure loss and velocity distributions, and, for the case of laminar two-phase flow with axial symmetry, explicit expression is presented. By hydraulic equation, the relation between void fraction and other variables are discussed. For the upward two-phase flow with constant flow area, gas-liquid interaction force is discussed theoretically and experimentally. 相似文献
10.
11.
《Journal of Nuclear Science and Technology》2013,50(11):915-928
Experimental results are presented on the flow behavior, phase distribution, average void fraction and slip ratio in air-water two-phase mixture flowing through an inverted U-bend. The curved test section of transparent acrylic resin tubing with 24 mm I. D. was used, comprising a riser, an inverted U-bend with radius of 96 mm, and a downcomer. From the visual observation, a flow map was derived, which indicates the relation between the flow patterns and velocities. Distributions of local void fraction along a diameter lying in the central plane of the bend and over the whole cross section of bend tube were measured, and those distribution mechanisms were explained by the effect of centrifugal and gravitational forces. The average void fraction around the bend was obtained by numerical integration of the measured local void fraction, and the slip ratio was calculated using the average void fraction. 相似文献