Effect of melt-to-solid volume ratio and preheating temperature on Mg/Al bimetals interface by centrifugal casting

Compound casting is an efficient method for bonding dissimilar metals,in which a dramatic reaction can occur between the melt and solid.The centrifugal casting process,a type of compound casting,was applied to cast Al/Mg dissimilar bimetals.Magnesium melt was poured at 700 °C,with melt-to-solid volume ratios(Vm/Vs) of 1.5 and 3,into a preheated hollow aluminum cylinder.The preheating temperatures of the solid part were 320,400,and 450 °C,and the constant rotational speed was 1,600 rpm.The cast parts were kept inside the casting machine until reaching the cooling temperature of 150 °C.The result showed that an increase in preheating temperature from 320 to 450 °C led to an enhanced reaction layer thickness.In addition,an increase in the Vm/Vs from 1.5 to 3 resulted in raising the interface thickness from 1.2 to 1.8 mm.Moreover,the interface was not continuously formed when a Vm/Vs of 3 was selected.In this case,the force of contraction overcame the resultant acting force on the interface.An interface formed at the volume ratio of 1.5 was examined using scanning electron microscopy(SEM) equipped with energy-dispersive X-ray spectroscopy(EDS),and the results demonstrated the formation of Al_(3)Mg_(2),Al_(12)Mg_(17) and(δ+Al_(12)Mg_(17)) eutectic structures in the interface.

Analysis of Porosity and Preheating Temperature on the Decomposition and Combustion Characteristics within 5 N Ammonium Dinitramide(ADN)-based Monopropellant Thruster

In this study,the effects of porosity of the fore-catalytic bed and after-catalytic bed and preheat temperature on the decomposition and combustion characteristics of a 5N ammonium dinitramide(ADN)-based thruster were numerically investigated in terms of the distribution of components,temperature,and pressure.The results indicated that the porosity of the fore-catalytic bed and preheating temperature significantly affected the decomposition and combustion characteristics.The porosity of the fore-catalytic bed was optimized,and the thrust performance was demonstrated to improve with increasing of porosity of the after-catalytic bed and pre-heating temperature.The results were favorable for the investigation of decomposition and combustion characteristics and could also be beneficial to the design and manufacture of different types of ADN-based thrusters.

Numerical Simulation of Jet Behavior and Impingement Characteristics of Preheating Shrouded Supersonic Jets

As a novel supersonic jet technology,preheating shrouded supersonic jet was developed to deliver oxygen into molten bath efficiently and affordably.However,there has been limited research on the jet behavior and impingement characteristics of preheating shrouded supersonic jets.Computational fluid dynamics(CFD)models were established to investigate the effects of main and shrouding gas temperatures on the characteristics of flow field and impingement of shrouded supersonic jet.The preheating shrouded supersonic jet behavior was simulated and measured by numerical simulation and jet measurement experiment respectively.The influence of preheating shrouded supersonic jet on gas jet penetration and fluid flow in liquid bath was calculated by the CFD model which was validated against water model experiments.The results show that the uptrend of the potential core length of shrouded supersonic jet would be accelerated with increasing the main and shrouding gas temperatures.Also,preheating supersonic jets demonstrated significant advantages in penetrating and stirring the liquid bath.

Analysis of feed pelleting characteristics based on a single pellet press device

Pelleting is the most extensively used thermal processing method in feed industry.In this article,a single pellet press device was developed to investigate the pelleting processing of animal feed.Effects of moisture content(10%-18%w.b.),preheating temperature(60°C-100°C)and maximum compression force(0.2-0.6 kN)on feed pellet were determined and analyzed,as well as energy consumption.The results showed that unit density,pellet hardness and energy consumption were 0.87-2.92 g/cm3,1.08-4.55 kg,and 3.27-12.66 J/g,respectively.Unit density was found to increase with the increase of preheating temperature and maximum compression force,but decrease with the increase of moisture content.Pellet hardness showed a first ascending then descending trend with the increase of moisture content,but exhibited a positive relationship with both preheating temperature and maximum compression force.Energy consumption increased with the increase of maximum compression force,but exhibited descending trends with the increase of moisture content and preheating temperature.Due to its features of low cost,high efficiency and easy control,the single pellet press device has a wide application prospect in feed processing.

Experimental Investigations on NO_(x) Emission and Combustion Dynamics in an Axial Fuel Staging Combustor

Axial Fuel Staging(AFS)technology is an advanced low-emission combustion method in modem gas turbine,which divides the combustor into two axially arranged combustion zones.For revealing the characteristics of axial staged combustion,an industrial-grade combustor was designed and built.The distribution of temperature and velocity field in the combustor was presented with numerical simulation.And an Atmospheric Combustor Test Rig for axial staged combustion was built.The flow resistance characteristics of the combustor were measured at first.Then the effects of the equivalent ratio and the preheating temperature on the pollutant emission and combustion instability were investigated.The results show that the total pressure recovery coefficient in cold state is always above 98%;starting the secondary combustion at low load can reduce NO emissions by 50%,and can suppress the combustion oscillation amplitude of the combustor.At the design point with φ=0.62 and preheating temperature=400°C,NO emission and CO emission are 15.68 and 4.22 mg/m^(3)(@15%O_(2)).

Effects of Optimized Operating Parameters on Combustion Characteristics and NO_(x)Emissions of a Burner based on Orthogonal Analysis

To optimize the structure of the burner,improve the combustion performance,and reduce the emission of NO_(x),a self-circulating low NO_(x)combustion technology was used to design a new type of flue gas self-circulating low NO_(x)burner.Based on previous research on the numerical model of combustion and the composition of mixed gas on combustion and NO_(x)emissions,the effect of various factors on the ejection coefficient of the flue gas self-circulating structure was analyzed using the orthogonal test method,and the burner operating parameters,such as preheating temperature and excess air coefficient,were deeply studied through the three-dimensional finite element numerical model in this paper.The results show that the diameter ratio of the nozzle and the length of the cylindrical section of the flue gas self-circulating structure have great influence on its ejection and mixing ability.The optimal ejection coefficient was 0.4829.Overall,the amount of NO_(x)emissions greatly increased from 6.23×10^(-6)(volume fraction)at the preheating temperature 973 K to 3.5×10^(-3)at preheating temperature 1573 K.When the excess air coefficient decreased from 1.2 to 1,the maximum combustion temperature decreased from 2036.3 K to 1954.22 K,and the NO_(x)emissions decreased from 352.29×10^(-6)to 159.73×10^(-6).