cqvip:An overview of some popular rotary and reciprocating positive displacement( PD) pump types is given with the objective of presenting and comparing the respective sizing relationships and performance features. Reciprocating pumps discussed are the piston and plunger types. Rotary pumps addressed are gear( external and internal),vane,lobe,screw,and liquid ring pumps. To put the relative pump sizes in perspective,attention is fixed on the rotors or reciprocating elements of PD pumps,just as impellers indicate the sizes of rotodynamic pumps. The size of a PD pump is found from a dimensionless combination of displacement flow rate,rotative speed and diameter. The flow rate,head( or pressure rise) and power are related through the component efficiencies. The cavitation coefficient,often close to unity,connects the rotor tip speed or piston speed with the required NPSH,which can also be affected by the pressure rise of the pump due to leakage across the internal clearances. Operational effects due to cavitation,ingestion of gas or abrasives,and viscous and non-Newtonian fluids are discussed.
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机译：那是哪个Redpoll？ -比利时的Mealy Redpoll flammea ssp flammea和小Redpoll Carduelis flammea ssp歌舞表演的状态和现场识别原始名称（非英语）QUI SONT NOS SIZERINS？身份鉴定DU SIZERIN布尔卡德莱斯（FLAMMEA）FLAMMEA ET DU SIZERIN卡瓦莱德（FLAMMEA）比利时卡巴莱特[法国]
