取N=3 1000/3/3600 12.86m/S 0.06×0.12 dln/dn=√uB/B=√13.89×0.06/12:6×0.1=0.805 dC=6.491m 33~5 534%38.0%100%n=90.34% D=0.24m,N=3取N=3 1000 / 3/ 3600 12.86 / 0.06 0.12 u m s i = = / / 13.89 0.06/12.86 0.1 0.805 C C i i d d u B u B = = = = d m C 6.49 <3 3~5 >5 5.34% 38.0% 100% →η=90.34% ∴ D=0.24m,N=3