Practice questions on July 5, 2017; replies will earn 0–6 points (no scoring for replies sent more than 1 day after posting). Thank you for your replies
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Single-choice question (zero points for wrong answers): The method used by a vortex pump to regulate flow rate is ＿＿＿. (1) Adjust the outlet valve (2) Adjust the inlet valve (3) Adjust the bypass valve (4) Adjust both the inlet and outlet valves simultaneously. Answer: (3) No scoring for replies given within 1 day of posting; thank you for your reply
3 Because some of the liquid returns from the pump’s discharge pipe to the suction pipe, thereby reducing the flow rate in the discharge pipe. This method is more suitable for vortex pumps, as the characteristic curve of vortex pumps shows a sharp increase in head when the flow rate decreases, resulting in an increase in shaft power; whereas when the flow rate increases, the shaft power slightly decreases.