Number of channels  3  4  5  6  7  8 

arithmetic mean (m/s)  67。1  68。1  68。5  67。8  62。8  61。5 

standard deviation  3。89  4。14  2。90  1。64  4。38  3。90 

Seen  from  Table  1,  from  3channels  to  6channels  the arithmetic mean of particles speed has not changed much, but the standard deviation decreased, indicating that fluctuation in the  arithmetic  mean  is  smaller  and  the  overall  speed  of  the particles  thrown  off  rotor  has  risen。  From  6  channels  to  8 channels, the arithmetic mean decreased significantly, and the standard  deviation  also  increased,  indicating  that  the  overall speed  of  particles  thrown  down。  Therefore,  the  speed  of particles increases as the number of channels increases, in the 6  channels  reaches  a  peak  and  then  begins  to  decline。  Thus, rotor  with  6  channels  is  the  most  reasonable  design  and accelerates particles best。 Suppose  the  reasons  for  this  phenomenon  are:  with  the increase  in  the  number  of  channels,  the  time  of  particles thrown off  the  rotor  was  becoming  faster  and  faster  in  order from  3  channels  to  8  channels。  With  too  many  channels, particles  thrown  off  the  rotor  were  numerous,  resulting  in many  particles  in  rotor  without  full  acceleration  and  fall  off the  rotor,  leading  to  the  arithmetic  mean  of  particles  ejected speed  was  low  in  rotors  with  7  and  8  channels,  standard deviation was high; however, the fewer numbers  of channels would result in the fewer particles thrown off the rotor in unit time,  the  longer  accelerating  time,  and  the  reduction  of production efficiency。 In order to prove this hypothesis, it was made that the number of particles of each rotor-time graph, as shown in Fig。6Seen  from  Fig。6,  after  0。4s,  the  number  of  particles  in rotor reduced in order from 3 channels  to 8 channels  at each time  point。  In  the  case  of  equal  feeding  quantity,  it  was indicated  that  the  fewer  particles  remaining  in  the  rotor,  the faster the particles were thrown off the rotor with the shorter accelerating time。 In the time from 0。4s to 0。6s, the number of particles in rotor grew slowly, because of that the rotor began to throw particles out; meanwhile, the curve slope declined in order from 3 channels to 8 channels, which means the growth rate  of  particles’  number  decreased,  indicating  that  particles were thrown off the rotor faster and faster。 After 1。5s, none of particles  generated,  and  the  remaining  particles  were  thrown off  the  rotor,  resulting  in  the  reduction  of  the  particles’ number; the curve slope increased in order from 3 channels to 8 channels, which means the reducing rate of particles arose, showing that the particles were thrown off the rotor faster and faster  also。  This  is  consistent  with  the  content  hypothesis, proving the correctness of inference。