According to the operational principle of venturi-tube, a bushing-type heater for mixing hot and cool gaseous flow is designed in order to make the blower and burner exhaust hot smoke with necessary temperature parameter by the design under normal working condition. 根据文丘里管加速降压原理,设计制作了套管形式的冷热风混合加热器,使风机和燃烧器在正常工作条件下输出设计所需温度参数的热态烟气。