一型號(hào)為150S-78型離心泵Q=160m3/h,H=78米水柱,η=74%,n=2950轉(zhuǎn)/分,擬將原葉輪直徑D2=245mm,切削為D1=223mm,問(wèn)此時(shí)該泵軸功率是多少?