Alkali cyanides in the iron blast-furnace

An experimental and numerical investigation on the hot surface ignition of premixed gases under microgravity conditions

The effect of gravity on the combustion synthesis characteristics and the resultant microstructures of the synthesized metal matrix composites (MMCs) were studied for the HfB2/Al and Ni3Ti/TiB2 reaction systems conducted under both normal (1 g) and low gravity conditions. Under normal gravity conditions, the pellets were ignited at three orientations to the gravity vector. The low gravity combustion synthesis reactions were conducted on a DC-9 aircraft at NASA Lewis Research Center (NASA-LeRC). It was found that under normal gravity conditions, both the combustion temperature and wave velocity were highest when the pellets were ignited from the bottom. Both the combustion temperature and wave velocity were lower when conducting the reactions under low gravity than under normal gravity conditions. It is believed that the convective flow of argon gas was responsible for this phenomenon. Gravity-induced, density-driven fluid flow (sedimentation) of the heavier phases in the MMCs was also observed for both re...

The current research is focused on the study of methane-air flame stabilization under the flow geometry variation for normal and upside-down (reverse) flame orientation. The experimental studies of plane-symmetrical rod-stabilized flames under the normal and reverse-oriented gravity conditions were carried out. The results of numerical simulation are presented. The blow-off is shown to be the function of stabilization-body position. We consider both V-shaped and M-shaped plane-symmetrical open flames for different Reynolds numbers, fuel-air ratio and flame orientation relative to the gravity direction. Blow-off limits appear to be independent on the gravity for the lean methane-air mixtures while the quenching processes are different for the normal and reverse-oriented gravity conditions. Blow-off is also accompanied by the chemiluminescence intensity decrease under reverse-oriented gravity conditions, which is exhibited in localized plume extinction and gradual quenching. While under the normal gravity, it appears via stepwise vortex separation from the lateral plume parts. Under such conditions chemiluminescence intensity remains almost constant. The blow-off time scale under the normal gravity conditions is bigger as compared to reversed-oriented ones by several times.

Two-phase flows of gas and liquid are increasingly paid much attention to space application due to excellent properties of heat and mass transfer, so it is very meaningful to develop studies on them in microgravity. In this paper, gas-phase distribution and turbulence characteristics of bubbly flow in normal gravity and microgravity were investigated in detail by using Euler–Lagrange two-way model. The liquid-phase velocity field was solved by using direct numerical simulations (DNS) in Euler frame of reference, and the bubble motion was tracked by using Newtonian motion equations that took into account interphase interaction forces including drag force, shear lift force, wall lift force, virtual mass force and inertia force, etc. in Lagrange frame of reference. The coupling between gas–liquid phases was made with regarding interphase forces as a momentum source term in the momentum equation of the liquid phase. Under the normal gravity condition, a great number of bubbles accumulate near the walls under the influence of the shear lift force, and addition of bubbles reduces turbulence of the liquid phase. Different from the normal gravity condition, in microgravity, an overwhelming majority of bubbles migrate towards the centre of the channel driven by the pressure gradient force, and bubbles have little effect on the turbulence of the liquid phase.

The effects of gravity on the combustion characteristics and microstructure of metal-ceramic composites (HfB2/Al and Ni3Ti/TiB2 systems) were studied under both normal and low gravity conditions. Under normal gravity conditions, pellets were ignited in three orientations relative to the gravity vector. Low gravity combustion synthesis (SHS) was carried out on a DC-9 aircraft at the NASA-Lewis Research Center. It was found that under normal gravity conditions, both the combustion temperature and wave velocity were highest when the pellet was ignited from the bottom orientation; i.e., the wave propagation direction was directly opposed to the gravitational force. The SHS of 70 vol pct Al (in the Al-HfB2 system) was changed from unstable, slow, and incomplete when ignited from the top to unstable, faster, and complete combustion when ignited from the bottom. The hydrostatic force (height × density × gravity) in the liquid aluminum was thought to be the cause of formation of aluminum nodules at the surface of the pellet. The aluminum nodules that were observed on the surface of the pellet when reacted under normal gravity were totally absent for reactions conducted under low gravity. Buoyancy of the TiB2 particles and sedimentation of the Ni3Ti phase were observed for the Ni3Ti/TiB2 system. The possibility of liquid convective flow at the combustion front was also discussed. Under low gravity conditions, both the combustion temperature and wave velocity were lower than those under normal gravity. The distribution of the ceramic phase, i.e., TiB2 or HfB2, in the intermetallic (Ni3Ti) or reactive (Al) matrix was more uniform.

Oscillatory thermocapillary convection in a liquid bridge: Part 1—1 g Experiments

In view of the great importance of two geometrical parameters such as void fraction and interfacial area concentration to the accurate two-phase flow analysis at microgravity conditions, axial developments of flow parameters such as void fraction, interfacial area concentration, bubble Sauter mean diameter, and bubble number density were measured in bubbly flow at microgravity and low liquid Reynolds number conditions where the gravity effect on the flow parameters were pronounced. A total of seven data sets were acquired in the flow range of the void fraction from 1.01% to 3.36% and the liquid Reynolds number from 1,400 to 4,750. The measurements were also performed in the similar flow range at normal gravity conditions. The transport mechanisms of the flow parameters are discussed in detail based on the data measured at normal and microgravity conditions, and the drift-flux model developed at microgravity conditions are compared with the measured data.

This study explores a novel hypothesis. According to Taheri, various T-Consciousness Fields (TCFs) exist, each with distinct functions, and are considered subsets of the Cosmic Consciousness Network. Although these fields lack any physical entity, their effects can be detected through laboratory experiments. It is hypothesized that when a subject is exposed to TCFs, the information transmitted from these fields can alter the properties or behavior of the treated samples compared to untreated controls. In the present experiment, the Faradarmani Consciousness Field, one type of TCF, was applied to investigate its effect on the cell cycle progression of the lymphoma Raji cell line under both simulated microgravity and normal Earth gravity conditions. There were four experimental groups, and the experiment duration was 48 hours. Samples not exposed to the Faradarmani Consciousness Field were considered the control group. Based on flow cytometry analysis, apoptosis was observed in cells exposed to microgravity (MG), with the sub-G1 phase increasing to approximately 42% (p-value< 0.05), whereas Faradarmani-treated samples remained almost unchanged under MG stress Similarly, Faradarmani-treated samples exhibited similar percentages of G1 and S phases under microgravity conditions compared to Earth gravity, while a significant decrease was observed in samples without the field effect (p-value < 0.05). However, under normal gravity conditions, the effect of FCF was not significant compared to the control. These observations suggest that the Faradarmani Consciousness Field influences cell cycle progression differently depending on environmental conditions. Under microgravity (MG) stress, the information transmitted from this T-Consciousness Field appears to have an alleviating effect, whereas under normal Earth gravity, it did not produce a significant change.

A transient short-hot-wire technique is proposed and used to measure the thermal conductivity and thermal diffusivity of liquids simultaneously. The method is based on the numerical evaluation of unsteady heat conduction from a wire with the same length diameter ratio and boundary conditions as those in the experiments. To confirm the applicability and accuracy of this method. Measurements were made for five sample liquids with known thermophysical properties and were performed under both normal gravity and microgravity conditions. The results reveal that the present method determines both the thermal conductivity and the diffusivity within 2 and 5%. respectively. The microgravity experiments clearly indicate that even under normal gravity conditions, natural-convection effects are negligible for at least l s after the start of heating. This method would be particularly suitable for a valuable and expensive liquid, and has a potential for application to electrically conducting and or corrosive liquids when the probe is effectively coated with an insulating and anticorrosive material.

Limiting oxygen concentration for extinction of upward spreading flames over inclined thin polyethylene-insulated NiCr electrical wires with opposed-flow under normal- and micro-gravity

In this article, flame spread phenomena over cylindrical fuel geometry are studied in spacecraft environments and contrasted with those on Earth. An in-house 2D axisymmetric computational fluid dynamics model is used to study the flame spread phenomena. Experimental flame spread results, in normal gravity and microgravity conditions, are used for model validation. The effect of uniform external opposed flow (0–25 cm/s) and surrounding oxygen concentrations (17.5–35%) is investigated in detail for a thin fuel rod of diameter 1 mm. The flow fields around the flame spreading in normal gravity and microgravity are very different. In normal gravity, buoyancy accelerates the flow and entrains surrounding air into the flame. In microgravity, the flow velocities increase only moderately due to thermal expansion. The change in the flow field results in significantly larger flames in microgravity, which spreads faster than the normal gravity flames. A detailed heat transfer analysis is carried out for the solid fuel. In general, the radial heat conduction of heat from the flame to fresh fuel ahead of the flame is the most prominent mode of heat transfer that controls the flame spread rate. However, in normal gravity conditions, near the low oxygen extinction limit, the contribution of axial heat conduction through the solid fuel also becomes significant and may contribute to about 20% of the total heat input to the fresh solid fuel. In normal gravity, the flame spread rate decreases with the increase in external flow speed. On the other hand, in microgravity, an increasing and decreasing trend in flame spread rate is observed with the increase in external flow speed. The flame spread rate increases with the increase in oxygen in normal gravity and microgravity environments.

A fluidized bed reactor for use under microgravity and partial gravity conditions has been designed and tested at NASA Glenn's 2.2 Second Drop Tower. Injection of a swirling flow is utilized to stabilize the bed. Under microgravity conditions, the fluidized bed is formed under a balance of radial drag and centrifugal forces acting on the bed particles. In laboratory tests, gravitational effects, primarily related to settling effects of the particles under normal gravity conditions, are clearly observed and impact the fluidized bed formation. In microgravity, there is a lack of gravitational settling of the particles. Analysis of the particle distribution is carried out by imaging with orthogonal cameras.

Experimental and numerical investigations on dissolution and recrystallization processes of GaSb/InSb/GaSb under microgravity and terrestrial conditions

This paper focuses on the analysis of multi-component droplet heating and evaporation under microgravity and normal gravity conditions. This analysis is based on the conventional conservation equations of species and energy for the gas phase, and the energy balance equation at the liquid–gas interface. The species diffusion is based on the Hirschfelder law, rather than on the less general Fick’s equation. Moreover, the heat flux due to species diffusion is taken into account in addition to the classical conduction heat flux between the gas and the liquid droplets. The liquid phase analysis is based on the infinite thermal conductivity liquid phase model, which has been justified by a reasonably good agreement between the predicted and experimental results. Indeed, the developed evaporation model has been validated against experimental data reported by Chauveau et al. (2008), where the droplets evaporation has been observed in microgravity and normal gravity conditions. The effects of gravity have been taken into account by introducing the Grashof number in the expressions of the Sherwood and Nusselt numbers. This model has been implemented in the multidimensional IFP-C3D industrial software. The modeling and experimental results have been shown to be reasonably close and the gravitational effects have been revealed to be significant especially for multi-component liquids including heavy components.

Characteristics of developing vertical bubbly flow under normal and microgravity conditions