降低转速 meaning in English

despin mechanism
despinning
gear down

According to pump performance curve shown we can get that the distance h is changed with the rotate speed n in the same point q , and the flux q is changed with the rotate speed n in the same point h . from the curve we can get the rule that the distance and rotate speed are in direct with ratio at the same flux point , and the rotate speed and the flux are also in direct with ratio at the same distance point
根据相似定律：流量与转速的一次方成正比；扬程与转速的二次方成正比；功率与转速的三次方成正比。即在降低转速，调低水泵出水扬程的同时，功率下降的幅度非常大，从中可以节省相当大的电能。完全应在高水位时降低水泵机组转速，从而使电机的输出功率随着转速下降值与转速原值商的三次方关系下降。