The paper instruduces the construction,the law of airflow and calculation methodof Laval Nozle were,which was used in the double pipes positive pneumatic conveying systen of moden flour mill.

• 介绍了在现代专用粉厂气力压运复式系统中使用的拉伐尔喷管的结构、气流运动规律及计算方法。