Numerical Simulation of Temperature Field for Laser Rapid Prototyping
The temperature field model for laser rapid prototyping is established by the mathematical treatment of laser power input. Temperature fields with different process conditions are numerical simulated, and the temperature is Gaussian distribution as the intensity distribution on laser beam cross-section. Temperature fields for laser rapid prototyping ware measured by thermal imager in real time. The simulation results agree with the experimental measurement. Experiments show that the temperature field model can be used for computer analysis and optimizing of laser rapid prototyping processing.
A note on rapid manufacturing process of metallic parts based on SLS plastic prototype
Abstract The polystyrene prototypes were produced by selective laser sintering (SLS) rapid prototyping process. According to properties of thermal depolymerisation of prototype material, the rapid manufacturing process for metallic parts was worked out through the combination of rapid prototypes and precise casting technology. After prototypes burned out in precision shell moulds, a series of complicate thin walled Al-alloy parts have been successfully made by vacuum differential pressure casting (VDPC) process. Accuracy of parts and influencing factors were investigated and discussed. The process combines the advantages of producing high-qualified metallic parts with shortening the period of production cycle.
Numerical and experimental investigation on air distributor design of fluidized bed reactor of sawdust pyrolysis
Abstract An improved biomass conversion in a lab-scale fluidized bed reactor (FBR) is achieved by optimizing the air distributor orifice size and number. Two approaches for introducing air were numerically and experimentally examined. These included perforated plate and downward orifice sparger. 3 mm and 5 mm orifice diameters, and 7, 9 and 13 holes were simulated at flow velocities of 2, 4, 6, and 8 times the minimum fluidization velocity, Umf. The simulation results revealed that increasing the orifice number has a positive effect on gas holdup, particularly for the perforated plate, which showed a uniform distribution of bubbles. The sparger configuration produced larger bubbles sizes, which could lead to better recirculation of solid flux, while stagnant particle zones were observed at the lower section of both distributors. A pyrolysis unit is also inserted at the top of freeboard of the FBR. For perforated plate with 6Umf, the pyrolysis process achieved thermal and cold gas efficiencies of 82.91% and 52.03%, respectively, while combustible gases with 41.6%mol CO, 8.7%mol CH 4 and 2.17%mol HC, were obtained. For sparger pipe and 6U mf _sp, 35.33 ppm NOx and 111 ppm SO 2 were measured in flue gas from combustion process at bed region.