In order to optimize airflow parameters and zeroposition control system of the closed steam hood in paper machine’s dryer section, the air condition both inside and outside of the hood was firstly analyzed. The pressuredifference changing curve between inside and outside of the hood was established under mechanical ventilation. On the other hand, the influence of air temperature or volumedifference between supplied and drawn air on zeroposition was also quantitatively analyzed. Finally, the quantificational zeroposition control model was established. The results indicated that the air temperature inside upper hood, the variation of which is about 55 % of the variation of supplied air temperature, is directly propotional to the level of zeroposition. The variation of supplied air moisture can cause the volumedifference between supplied and drawn air changing by about 12.5 % which has an inverse propotion to the level of zeroposition. According to the principle of adjusting the volumedifference between supplied and drawn air, the deviation of zeroposition can be quickly regulated by setting feedforward control system.
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