| In this dissertation the principle and parameter optimization of the fan of the 4ZTL -- 1800 Stripping Combine Harvester are invested with laboratory experiments and theoretical analysis to reduce the noise of the fan ,and the Pneumatic Characteristics of the Pneumatic Conveying System are invested initially.The noise of the fan is mainly consist of circumrotatory noise and backset noise based on the theoretical analysis. The noise mechanism made by the fan tongue is further studied and the clearance between the tongue and the blade is invested experimentally, it is found that the gap of tongue is the key parameter to the noise and efficiency of the fan and the optimal gap is got based on the experiment.The experiment shows that the noise of the fan with inclining tongue is much lower than the fan with straight tongue, but the efficiency of the fan varies unobviously with the two kinds of tongue. The reason that the noise is lower with inclining tongue is:1) Both the radius of the tongue and the gap between the tongue and the blade are changed across the wideth;2)The phase angle between blade and the tongue is changed across the wideth, therefore the peak value of the noise do not appear at the same time, so the peak value of the noise with inclining tongue is much lower than the straight one.The influence of the expanded angle of the shell of the fan on the noise was invested experimentally, and the optimal angle was got.In addition, the airflow speed distribution pattern along the sunction pipe and its influence on the Pneumatic Characteristics of the Conveying System were invested.
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