Waste sintered Nd-Fe-B permanent magnets were recycled via doping (Nd 20 Dy 80 ) 76 Co 20 Cu 3 Fe 1 special alloy (SA) powders. The effect of the SA on the microstructure and magnetic properties of the recycled magnets has been studied. The SA additives between 0.0 and 2.0 wt% have little effect on the remanence (B r ) of the recycled magnet. When the additive content is more than 2.0 wt%, the remanence (B r ) begins to decrease. The coercivity of recycled magnet increases gradually as the SA additive increases. Compared with the properties of the original waste sintered magnet, a magnet recycled with 2.0 wt% SA recovers 97.5%, 92.4%, and 93.1% of B r , H cj and (BH) max , respectively. The volume fraction of the Nd-rich phase reaches a maximum of 7.4 vol% for 2.0 wt% SA, which is nearly equal to that of the original waste magnet. The average grain size of all the recycled magnets is larger than that of the original waste magnet. It is our conclusion that currently 2.0 wt% SA additive is the best content for recovering the properties of the waste magnets.Index Terms-Magnetic properties, Nd-Fe-B sintered magnet, rare earth rich alloys, recycling.

This paper has built a mathematical model for the evaporating characteristics of the grooved micro heat pipe’s thin film region and computed them in a specific working condition. The evaporating model of Wayner was employed in this mathematical model. The results from computation showed, for the H2O and NH3 as working fluid, at the beginning of the thin film region, the heat flux raised rapidly to a peak value and then declined to almost 0 also rapidly in a very short distance. Differently, for the Na and K as working fluid, the heat flux raised quickly but declined slower. Therefore, the alkali metals working fluids had larger area of high heat flux covered. The results indicated that the alkali metals working fluid has better evaporating characteristics for the high-temperature heat pipe than normal working fluids.

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The Nd2Fe14B/α-Fe bulk exchange-spring magnets have been prepared by spark plasma sintering melt spun Nd9.8Dy0. 4Fe78.4Co5.6B5.8 flakes under different temperatures and pressures. It was found that higher sintering temperature improved the densification of the magnets, while deteriorated their magnetic properties simultaneously. An increased compressive pressure can restrain the grain growth remarkably and then leads to better magnetic properties and higher density for the magnet at same sintering temperature. XRD analysis showed that with the increase of sintering pressure, some peaks indicating c-axis texture such as (006) and (105) became dominant. As a result, the bulk magnet exhibited higher remanence and maximum energy product than starting powders.

Forward-facing cavity mounted on the blunt nose of hypersonic vehicle is a good choice to reduce the stagnation heating. Presently, the study on hypersonic vehicles nose tip with forward-facing cavity mainly focus on its thermology characteristic, and little work can be found investigating the effect of cavity on aerodynamic force for a holistic vehicle. The CFD method is developed to investigate the effect of cavity geometry on aerodynamic performance of hypersonic vehicle with a forward-facing cavity on the nose-tip. Drag coefficient, lift coefficient and pitching moment coefficient of the vehicle for different attack angle are calculated. It is found that the cavity length to diameter (L/D) can not be a characteristic parameter in aerodynamic research, though it was used as a main characteristic parameter in investigation on the thermal protection. The length of the cavity L has little effect on aerodynamic characteristic of the vehicle, and the cavity diameter D has a crucial influence on the aerodynamic performance and the aerodynamic performance decrease with the D increasing. With the attack angle increasing, the drag coefficient, lift coefficient, pitching moment coefficient and lift-drag ratio of the hypersonic vehicle all increase.

The cooling effect of a film cooling thermal protection system is investigated, and the flow field, aerodynamic force and surface temperature distribution are obtained. The numerical method is validated by experiment with no film cooling. The physical mechanism of the reduction of temperature is analyzed. The jet interacts with the free stream to form a thermal insulating layer on the wall, which enables the free stream to flow outside the wall rather than interact with the surface to produce aerodynamic heating. In addition, the film cooling flow form a cool recirculation region, which reduces the temperature on the surface. Analysis of the numerical simulation results shows that this kind of thermal protection system has an excellent cooling effect on the surface of the nose-tip. With the outlet speed increasing, the cooling efficiency is improved and the aerodynamic resistance is changeless. When outlet speed and total pressure are invariable, the cooling effect of air and nitrogen is the same, but the cooling effect of helium is better.

In this paper, a thermal protection system (TPS) of opposing jet combined with a forward-facing cavity in hypersonic flow was investigated numerically. The flow field parameters and heat flux distribution along the outer body surface are obtained. The thermal protection efficiency of the combined TPS and the single opposing jet TPS was compared. The numerical results shows that this combined TPS has a good effect on cooling the nose of hypersonic vehicle. The recirculation region plays an pivotal role for the reduction of heat flux. The exist of the cavity strengthen the cooling efficiency.

The GO2/ethanol/water tripropellant evaporation and combustion in axisymmetric combustion chamber was numerically simulated. The different characteristics of the evaporation and combustion between dilative and traditional un-dilative entrance, and the different dilation-angles of the combustion chamber entrance are analyzed. The results indicate that the dilative entrance combustion chamber is benefit for thermal protection of the injection, and the flamelet backpedals with increase of the entrance dilation-angle. At the same time, that dilative inlet combustion chamber reduces the evaporation of the liquid component seriously. The evaporation rate decreases with the increase of the dilation-angle at first, but after the dilation-angle is bigger than a critical one, it increases.